biofisica.org.ar.ca1.toservers.combiofisica.org.ar.ca1.toservers.com/reunion2014/files/... · 2014-12-04 · XLIII RA – SAB 2014 COMISIONES Y COMITÉS _____________________________________________________

XLIII RA SAB 2014

_____________________________________________________

SOCIEDAD ARGENTINA DE

BIOFSICA

XLIII Reunin Anual 3 5 de Diciembre 2014

Sierra de la Ventana, Pcia. de Buenos Aires ARGENTINA

XLIII RA SAB 2014

_____________________________________________________

Fecha de Catalogacin: 01/12/2014

Quedan prohibidos, dentro de los lmites establecidos en la ley y

bajo apercibimiento legalmente previsto, la reproduccin total o

parcial de esta obra por cualquier medio o procedimientos ya sea

electrnico o mecnico, el tratamiento informtico, el alquiler o

cualquiera otra forma de cesin de la obra sin la autorizacin

previa y por escrito de los titulares del copyright.

Diagramacin y Edicin: Nstor Edgardo Sanchez Fornillo

Diseo de Tapa: Marcelo Costabel.

Asistencia Tcnica Web: Juan Pablo Acierno - Mauricio Sica

Sanchez Fornillo, Nstor Edgardo SAB 2014: XLIII Reunin Anual de la Sociedad Argentina de Biofsica / Nstor E. Sanchez Fornillo ; Marcelo D. Costabel. 1 ed. Baha Blanca Sociedad Argentina de Biofsica 2014 ISBN 978-987-27591-3-1 1 Biologa. Investigacin. I. Sanchez Fornillo, Nestor E. II. Costabel, Marcelo III. Ttulo CDD 571.4

XLIII RA SAB 2014 COMISIONES Y COMITS

_____________________________________________________

COMISION DIRECTIVA DE LA

SOCIEDAD ARGENTINA DE BIOFSICA AO 2014

PRESIDENTE Gerardo Fidelio Universidad Nacional de Crdoba

VICEPRESIDENTA Gabriela Amodeo Universidad de Buenos Aires

Presidente Saliente Luis Gonzalez Flecha Universidad de Buenos Aires

Secretario Mauricio Sica Centro Atmico Bariloche

Tesorero La Pietrasanta Universidad de Buenos Aires

Vocales Titulares Karina Alleva Universidad de Buenos Aires

Rosana Chehn

Universidad Nacional de Tucumn

Vocales Suplentes Rodolfo Rassia Universidad Nacional de Rosario

Florencia Martini

Universidad de Buenos Aires.

XLIII RA SAB 2014 COMISIONES Y COMITS

_____________________________________________________

COMIT CIENTFICO

Dra. Gabriela Amodeo Universidad de Buenos Aires

Dra. Silvia Antollini Universidad Nacional del Sur

Dra. Cecilia Bouzat

Universidad Nacional del Sur

Dra. Betina Crsico Universidad Nacional de La Plata

Dr. Marcelo Costabel Universidad Nacional del Sur

Dra. Vernica Dodero Universidad Nacional del Sur

Dra. La Pietrasanta

Universidad de Buenos Aires

Comit organizador (SAB-Baha Blanca)

Dr. Marcelo Costabel

Dra. Silvia Antollini

Dra. Cecilia Bouzat

Dra. Vernica Dodero

Dr. Jeremas Corradi

Ing. Nstor Snchez Fornillo

Bioq. Fernando Zamarreo

Colaboradores

Lic. Ma Julia Admundarain Bioq. Giorgina Herrera Bioq. Daniel A. Pealva Dra. Tania Veuthey

Lic. Juan F. Viso

XLIII RA SAB 2014 NDICE GENERAL

_____________________________________________________

PALABRAS COMIT ORGANIZADOR.. 7

AUSPICIANTES 8

PROGRAMA. 10

CONFERENCIAS Y SIMPOSIOS. 22

POSTERS

Bioenergtica, Transferencia Electrnica. Bioenergetics, Electronic Transfer.

54

Enzimologa. Enzimology

58

Lpidos y Biomembranas Lipids and Biomembranes...

61

Nuevas Tcnicas y Aplicaciones en Biofsica.. New Techniques and Applications in Biophysics.

85

Protenas y cidos Nucleicos.. Proteins and Nucleic Acids

95

Sealizacin y Dinmica Intracelular Signaling and Intercellular Dynamics..

129

Teora y Modelado de Sistemas Biolgicos. Theory and Modelling of Biological Systems.

136

Transportadores, Receptores y Canales... Transporters, Receptos and Channels.

157

INDICE DE AUTORES. 179

XLIII RA SAB 2014 PALABRAS DEL COMIT ORGANIZADOR

________________________________________________

7

Pas mucho desde aquel Club de la Membrana

Hoy, en las reuniones SAB, no slo se escucha de lpidos y

de cmo organizarlos en estructuras ms complejas; las protenas, y otras macromolculas pasaron a ser, tambin, parte fundamental de las preguntas que intentamos responder. Ms an, adems del cambio en los sistemas que estudiamos, las tcnicas y la metodologa han variado sustancialmente con el correr de los aos; el espectro experimental ha crecido en variantes y precisin y los modelos computacionales han adquirido un protagonismo esencial en la bsqueda de respuestas donde el experimento an no puede llegar. Inexorablemente nuestra SAB se ha transformado en un mundo donde la biologa, la bioqumica, la fsica, la qumica, la informtica y sus variadas combinaciones se aglutinan para ofrecernos herramientas de discusin que nos permitan describir un universo cuanto menos fascinante.

En funcin de esto, si quisiramos resumir hoy nuestra reunin SAB en una palabra, quizs esa palabra sea Consiliencia. Es por esto que, disfrutando de un entorno maravilloso donde se mezclan las sierras, los campos y los riachos de una Ventania prdiga, seamos capaces de entretejer ideas y dejemos que esa consiliencia desarrolle sus frutos y nos d el marco adecuado para intentar dar forma a un proyecto de ciencia diferente, donde nuestros jvenes encuentren su lugar y su oportunidad sin necesidad de mezquindades, y sepan que el trabajo con inteligencia puede tener su premio.

Unas ltimas palabras para todos los que comparten estos das. Gracias a todos los que aportaron su trabajo, su tiempo, su opinin, su consejo, su reflexin, y tambin su crtica en pos de una organizacin no perfecta; pero seguramente empeada en el bienestar de todos. Y gracias a cada uno de los que hoy llegaron hasta aqu: los conferencistas, simposistas y asistentes en general sin los cuales, obviamente, todo esto no tendra sentido.

En fin en un contexto econmico difcil, fue arduo armar el rompecabezas, pero llegamos a este punto con la esperanza puesta en que todos los que hoy comparten la reunin vuelvan a su terruo con una sonrisa y sientan el placer de que cada minuto en Sierra de la Ventana vali la pena.

XLIII RA SAB 2014 AUSPICIANTES

_____________________________________________________

8

XLIII RA SAB 2014 PROGRAMA

_____________________________________________________

9

PROGRAMAPROGRAMAPROGRAMAPROGRAMA


_____________________________________________________

10

Mircoles 3 de diciembre 9:00 - 12.00 hs REGISTRO

11:50 12:00 hs APERTURA

12:00 - 13.00 hs CONFERENCIA 1 CONFERENCIA DE APERTURA Insertion of a transmembrane helix, and its uses in targeting tumors Dr. Donald M. Engelman Department of Molecular Biophysics and Biochemistry, Yale University, Estados Unidos

13.00 - 14.30 hs Almuerzo /Colocacin de posters

14.30 - 16.00 hs SIMPOSIO 1: POSTERS SELECCIONADOS Coordinadora: Dra. Gabriela Amodeo

16.00 - 17.00 hs CONFERENCIA 2 Dynamic Aspects of Peptide/Protein-DNA Interaction Dr. Norbert Sewald Department of Organic and Bioorganic Chemistry University of Bielefeld, Alemania

17:00 - 17.30 hs Caf

17.30 - 19.30 SIMPOSIO 2: INTERACCIONES MOLECULARES Coordinadora Dra. Betina Crsico Regulation of Voltage gated sodium channels by Calmodulin Dra. Sandra Gabelli


_____________________________________________________

11

Johns Hopkins University School of Medicine, Baltimore, Estados Unidos

Sterols in membranes: structural features that rule the interaction with phospholipids Dr. Jorge Wenz Instituto de Investigaciones Bioqumicas de Baha Blanca, Universidad Nacional del Sur Argentina

Lipid and protein aggregates activate receptors of the innate system Dr. Jean Mari Ruysschaert Free University of Brussels-Belgica

Structural Characterization of Heparin-induced GAPDH Protofibrils Preventing -synuclein Oligomeric Species Toxicity Dra. Rosana Chehin INSIBIO-CONICET-UNT, Tucumn, Argentina

19.30 20:30 hs CONFERENCIA 3 CONFERENCIA GREGORIO WEBER Solvent accessibility profiling in proteins Dr. Jos Mara Delfino Instituto de Qumica y Fisicoqumica, Universidad de Buenos Aires, Argentina

20.30 - 22.30 hs SESIN DE POSTERS Y CENA SNACK


_____________________________________________________

12

Jueves 4 de diciembre 8.30 - 9.30 hs SIMPOSIO 3: JVENES

INVESTIGADORES Coordinadora Dra. Silvia Antollini Synaptic gain-of-function effects of mutant CaV2.1 channels in a mouse model of familial hemiplegic migraine are due to increased basal [Ca2+] Dr. Mariano Di Guilmi IFIBYNE, UBA- CONICET

ABA-1A: a Nematode Polyprotein Allergen (NPA) of Ascaris suum. Structure and binding properties. Dra. Gisela Franchini

INIBIOLP-CONICET, Fac.de Ciencias Mdicas, Universidad de La Plata

Membrane role in the rational design of HIV fusion inhibitors Dr. Axel Hollmann

Instituto de Medicina Molecular, Faculdade

de Medicina, Universidade de Lisboa,

Portugal; Laboratory of Biointerfaces and

Biomimetic Systems- CITSE- CONICET,

Argentina


_____________________________________________________

13

Effects of nitric oxide on heart mitochondrial calcium handling Dra. Tatiana Zaobornyj

Institute of Biochemistry and Molecular

Medicine (IBIMOL, UBA-CONICET), School of

Pharmacy and Biochemistry, University of

Buenos Aires, Buenos Aires, Argentina

9.30 10:30 hs CONFERENCIA 4 PREMIO SAB

10.30 11:00 hs Caf

11.00 - 12.00 hs CONFERENCIA 5 Triatoma virus as viral model and biotechnological tool: A simple machine able to do complex tasks Dr. Diego Guerin Unidad de Biofisica (CSIC-UPV/EHU), Universidad del Pas Vasco (EHU), Leioa, Vizcaya, Espaa

12.00 - 13.00 hs CONFERENCIA 6 TRPC channels and Ca2+ entry into cells Dr. Lutz Birnbaumer Instituto de Investigaciones Biotecnolgicas (IIB-INTECH), Universidad Nacional de San Martn, Argentina

13.00 - 14.30 hs Almuerzo /Colocacin de

posters


_____________________________________________________

14

14.30 - 16.30 hs SIMPOSIO 4: MODELOS MATEMTICOS APLICADOS A SISTEMAS BIOLGICOS Coordinadora Dra. Vernica Dodero

Mathematical models for cytoskeletal transport and cellular viscoelasticity

Dr. Sebastin Bouzat Grupo de Fsica Estadstica e Interdisciplinaria, Centro Atmico Bariloche (CNEA). Argentina.

Using Machine Learning for Predictive Modeling on Systems Biology and Molecular Informatics Dr. Ignacio Ponzoni Instituto de Ciencias e Ingeniera de la Computacin, Universidad Nacional del Sur, CONICET, Baha Blanca, Argentina

Water at the nanoscale: Towards new principles and design elements for biophysics

Dr. Gustavo Appignanesi INQUISUR-UNS-CONICET and Departamento de Qumica, Universidad Nacional del Sur, Baha Blanca, Argentina.

16.30 - 17.00 hs Caf


_____________________________________________________

15

17.00 -19.00 hs SIMPOSIO 5: ESTRATEGIAS BIOFSICAS Y COMPUTACIONALES PARA EL ESTUDIO DE LA ESTRUCTURA DE PROTENAS Coordinador Dr. Marcelo Costabel How do Sco Proteins Score the COX? Dr. Alejandro Vila Instituto de Biologa molecular y Celular de Rosario y Depto. de Qca. Biol, Fac. de Cs. Bioq. y Farm, Universidad Nacional de Rosario (UNR), Argentina

On the Search of a Comprehensive Representation of Human Frataxin Dr. Javier Santos

Fundacin Instituto Leloir and IIBBA-CONICET, Argentina

Ligand binding mechanisms of bitter taste receptors: Insights from multiscale simulation approaches Dr. Alejandro Giorgetti Department of Biotechnology, University of Verona, Verona, Italy and Computational Biophysics, German Research School for Simulation Sciences, Juelich, Germany


_____________________________________________________

16

A simple model to simulate protein-membrane interactions with inclusion of electrostatics Dr. Marcos Villarreal INFIQC-Dpto Matemtica y Fsica. CONICET-Universidad Nacional de Crdoba. Argentina.

19.00 - 20.30 hs ASAMBLEA ANUAL DE LA SOCIEDAD ARGENTINA DE BIOFISICA

20.30 22:30 hs SESIN DE POSTERS Y CENA SNACK


_____________________________________________________

17

Viernes 5 de diciembre 8.30 - 10.30 hs SIMPOSIO 6: MICROSCOPA

Coordinadora Dra. La Pietrasanta

Mechanical and thermodynamic properties of lipid membranes using optical microscopy Dra. Natalia Wilke CIQUIBIC, Departamento de Qumica Biolgica, Facultad de Ciencias Qumicas, Universidad Nacional de Crdoba, Argentina

Dynamics and interactions of transcription factors in the cell nucleus through fluorescence fluctuation spectroscopy Dra. Valeria Levi Departamento de Qumica Biolgica- IQUIBICEN. Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires-Argentina

Far-field fluorescence nanoscopy of neurons Dr. Fernando Stefani Centro de Investigaciones en Bionanociencias - CIBION, CONICET, y. Departamento de Fsica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina


_____________________________________________________

18

Sistema Nacional de Microscopa: resultados y perspectivas Secretara de Articulacin Cientfico Tecnolgica Ministerio de Ciencia, Tecnologa e Innovacin Productiva

10.30 - 11.00 hs Caf

11.00 - 12.00 hs CONFERENCIA 7 Use of proteliposomes to study biomineralization process Dr. Pietro Ciancaglini Department of Chemistry, FFCLRP-USP, Brasil

12.00 - 13.00 hs CONFERENCIA 8 SACT-MinCyT Secretara de Articulacin Cientfico Tecnolgica Ministerio de Ciencia, Tecnologa e Innovacin Productiva

13.00 - 14.30 hs Almuerzo

14.30 - 16.30 hs SIMPOSIO 7: TRANSPORTADORES Y CANALES Coordinadora Dra. Cecilia Bouzat Two signaling pathways mediate presynaptic voltage gated calcium channels inhibition by two ghrelin receptor activation modes Dra. Jesica Raingo Multidisciplinary Institute of Cell Biology (IMBICE) La Plata Argentina


_____________________________________________________

19

Redox modulation of the GABAergic neurotransmission in the retina and the hippocampus Dr. Daniel Calvo INGEBI- CONICET, Buenos Aires, Argentina

Proton permeation in Ci-Hv1 voltage-gated proton channels occurs through a proton wire involving residues D160 and D222 and it is modulated by N264 Dr. Carlos Gonzlez C. Interdisc. de Neurociencias de Valparaso, Universidad de Valparaso, Chile.

The role of auxiliary 1 subunit of the BKCa channel as a tissue selective target for endogenous and exogenous substances Dr. Vernica Milesi Laboratorio de Canales Inicos, IIFP CONICET-UNLP, La Plata, Argentina.

16.30 - 17.30 hs CONFERENCIA 9 Structure-based design of new inhibitors against aggregation of amyloid -peptide and BACE-1 enzyme Dr. Ricardo Daniel Enriz Departamento de Farmacia, Universidad Nacional de San Luis, y JIMIBIO-SL (CONICET), San Luis, Argentina.

17.30 - 18.00 hs Caf


_____________________________________________________

20

18.00 - 19.00 hs CONFERENCIA 10 CONFERENCIA DE CLAUSURA Control of the levels of PIP3: Structure and Function of the lipid kinase PI3Kalpha Dr. Mario Amzel Johns Hopkins University School of Medicine, Baltimore, Estados Unidos

19.00 - 20.30 hs CIERRE DE LA REUNIN

21.00 hs CENA DE CLAUSURA

XLIII RA SAB 2014 CONFERENCIAS Y SIMPOSIOS

_____________________________________________________

21

CONFERENCIASCONFERENCIASCONFERENCIASCONFERENCIAS


_____________________________________________________

22

CONFERENCIA 1

Insertion of a transmembrane helix, and its uses in targeting tumors Donald M. Engelman Department of Molecular Biophysics and Biochemistry, Yale, The discovery that the C helix of Bacteriorhodopsin exhibits spontaneous, pH-dependent insertion to form a helix across lipid bilayers has led to the use of related peptides, pHLIPs (pH (Low) Insertion Peptides), to study peptide insertion across bilayers, to selectively target cargoes to tumors and other acidic tissues in vivo, and to deliver molecules across the plasma membranes of living cells. Because pHLIP is unfolded on the surface of a bilayer and folding is pH-triggered, we are able to begin to observe and understand the molecular events that accompany the insertion and folding of a peptide entering a bilayer. When the pH is dropped, it is found that a helix forms rapidly on the bilayer surface, followed by a slow insertion across it in several kinetically distinct steps. The exit pathway when the pH is suddenly raised is more rapid, and includes partial unfolding of the helix while still in the bilayer. Lipid composition and sequence features affect the insertion pK and pathway intermediates. pHLIPs target acidic tissues in vivo, where the transmembrane insertion stabilizes them in cells, enabling targeting of imaging and therapeutic agents. We have shown targeting of dyes, radioisotopes, nanogold and Peptide Nucleic Acids (PNAs) to tumors in mice, and will report on the use of PNAs to target the suppression of onco-micro RNAs, resulting in tumor growth inhibition in vivo


_____________________________________________________

23

CONFERENCIA 2

Dynamic Aspects of Peptide/Protein-DNA Interaction Ritzefeld, M.; Wollschlger, K.; Walhorn, V.; Anselmetti, D.; Sewald, N. Bielefeld University, Organic and Bioorganic Chemistry, Universittsstr. 25, 33615 Bielefeld, Germany, [email protected] Protein-DNA interactions are involved in many biochemical processes like replication, gene regulation and transcription. The dynamics of DNA recognition by the transcription factor PhoB from E. coli was investigated as a model system. PhoB recognizes cognate DNA sequences containing a TGTCA consensus sequence and an A/T-rich minor groove. A combined approach based on isothermal titration calorimetry (ITC), fluorescence resonance energy transfer (FRET) experiments, circular dichroism spectroscopy (CD), atomic force microscopy dynamic force spectroscopy (AFM-DFS) and surface plasmon resonance (SPR) was applied to elucidate the mechanism of protein-DNA complex formation and the impact of protein dimerization of the DNA-binding domain of PhoB (PhoBDBD). The ITC, SPR, FRET, and CD results indicate a positive cooperative binding mechanism and a decisive contribution of dimerization on the complex stability. With a combination of dynamic force spectroscopy and total internal reflection fluorescence microscopy (TIRF), we were able to identify specific bond rupture events.

1. R. Eckel et al., Biophys. J. 2003, 85, 1968. 2. R. Eckel et al., Angew. Chem. Int. Ed. 2005, 4, 3921. 3. K. Wollschlger et al., Small 2009, 5, 484. 4. M. Ritzefeld et al., Mol. Biosyst. 2011, 7, 3132. 5. M. Ritzefeld et al., Biochemistry 2013, 52, 8177.


_____________________________________________________

24

CONFERENCIA 3 Solvent accessibility profiling in proteins Gmez, G.E.1; Bernar, E.M.1; Arn, M.2, Sabeckis, L.1, Gonzlez Lebrero, M.C.1 and Delfino, J.M.1 1IQUIFIB (UBA-CONICET), Junn 956, (C1113AAD), Buenos Aires, Argentina. 2FIL, Av Patricias Argentinas 435, (C1405BWE), Buenos Aires, Argentina. Topography of proteins and their interactions can be investigated through photochemical mimicry of the aqueous solvent, an approach aimed at estimating the size and nature of the solvent accessible surface area (SASA). After reacting diazirine (DZN, the smallest CNN heterocycle) with proteins, it is possible to measure quantitatively the extent of modification (methylation) by the use of radiotracers (tritiated DZN), by metrics derived from modern mass spectrometry techniques (MALDI-TOF and ESI-MS) or by multidimensional NMR. Maximal resolution of the labeled site is achieved after fragmentation into small peptides or individual amino acids. Interestingly, the NMR approach does not demand cleavage and is potentially rich in conformational information. Predictably, methylation of amino acid side chains rules the DZN modification event. Molecular dynamics simulations highlight the distribution of the reagent onto surface components prior to photolysis. Thus, the probability of reaction at individual sites along the polypeptide reveals the map of solvent accessibility. Conformations can be distinguished corresponding to native or intermediate states, or the unfolded ensemble. Moreover, a paradigm of a peptide-protein complex (calmodulin-melittin) illustrates the value of this approach as a foot-printing technique able to pinpoint the area of interaction. One cannot overemphasize the worth of these new methods for the benefit of structural proteomics and interactomics.


_____________________________________________________

25

CONFERENCIA 5 Triatoma virus as viral model and biotechnological tool: A simple machine able to do complex tasks Gurin D. M. A. Unidad de Biofisica (CSIC-UPV/EHU), Universidad del Pas Vasco (EHU), Leioa, Vizcaya, Spain As many other small spherical and non-enveloped viruses, Triatoma virus (TrV; Dicistroviridae: Cripavirus) is built only with four capsid peptides, one single +ssRNA molecule, and several water molecules and ions. This simple macromolecular aggregate performs astonishing functions: i) assembles by itself spontaneously: ii) destroys the host membrane cell to escape; iii) its capsid supports very harsh environmental conditions during the journey to the target cell; iv) specifically binds to its receptor; v) disrupt the membrane cell to enter; vi) safely releases its genome into the cytoplasm, and finally, vii) sequesters the cell machinery to make its own progeny. Decades of study gave some clues to unravel these mechanisms, but still a great effort will be needed to understand how viruses work at atomic level. For instance, we will explain our hypothesis on how genome release may work in TrV. On the other hand, this insect virus naturally infects triatomines, the haematophagous insect vectors of Chagas disease. Also, TrV is considered as potential biological agent to control the disease's vectors. We explored in several countries some biological aspects of TrV and our results seem to support its potential as biopesticide. Moreover, TrV capsid can be used as platform to make 'fifth-generation' chimeric-VLP vaccines, as a nano carrier, and more....


_____________________________________________________

26

CONFERENCIA 6 TRPC channels and Ca2+ entry into cells. Lutz Birnbaumer, Instituto de Investigaciones Biotecnolgicas (IIB-INTECH,CONICET), Universidad Nacional de San Martin, Prov. de Buenos Aires, Argentina. TRPCs, of which there are 7, were cloned in the mid 1990s with the expectation that they would encode channels responsble for replenishment of Ca2+, not only after agonist stimulation, but also after mere depletion of stores without generation of IP3 or DAG, the latter generating a Ca2+ relase activated Ca current (Icrac), which is exquisitey Ca2+ selective.. But when expressed, TRPCs generated non-selective catin currenst with minimal selectivity of Ca2+ over Na+. In 2005 and 2006 two misisng players were discovered: STIM, resident in the ER membrane, sensing loss of Ca2+ from stores, and ORAI, resident in the plasma membrane, which upon co-expression with STIM leads to expression of large Icrac currents. Yet, store depletion also activates catin currents requiring TRPC1, and expression of low levels of ORAI in cells expressing TRPCs in stable form leads to increases in Ca2+ entry and of Icrac. Given that ORAI function had not been tested in a TRPC-null cell, we hypothesized that ORAI might be a regulator of TRPCs changing their Ca2+ selectivity. To resolve the conundrum, we set out to generate a TRPC-null mouse in which all Trpc alleles have been inactivated by classical or conditional gene targetting. Surpisingly, in May 2013 a female mouse with only disrupted Trpc genes was born and was fertile. Upon single inactivation, all our KO alleles have given interesting phenotypes, includng loss of Icrac in endotelial cell devoid of TRPC4, proving that they are disrupted. We found that MEFs from TRPC-null mice have unaltered store depletion activated Ca2+ entry, proving that ORAIs are the molecular substrate of Icrac currents. ORAI molecules in resting cells are dimers. Upon activation the ORAI dimers trimerize to form hexameric channels. It remains to be determined if ORAI dimers are regulators of TRPC channels. I thank the invaluable collaboartion of C. Dulac (Harvard, Trpc2 KO), M. Freichel/V Flockerzi (Saarland, Trpc4 KO) and Joel Abramowitz (NIEHS).


_____________________________________________________

27

CONFERENCIA 7 Use of proteliposomes to study biomineralization process Ciancaglini Pa, Simo AMSa, Bolean Ma, Hoylaerts MFb and Milln JLc aDepartment of Chemistry, FFCLRP-USP, Brazil; bCenter for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium; cSanford Childrens Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA, USA

During endochondral bone formation, chondrocytes and osteoblasts are responsible for the synthesis and mineralization of the extracellular matrix through a carefully orchestrated process, believed to initiate within membrane-invested matrix vesicles (MVs) at the sites of initiation of hydroxyapatite (HA) deposition and end with bone mineral propagation onto the collagenous scaffold. Acidic phospholipids and other MV components are thought to nucleate these intravesicular nanocrystals1. As we strive to understand the physiological interplay between TNAP, PHOSPHO1, NPP1, and other important MV-associated enzymes and channeling proteins in the initiation of biomineralization, we must keep in mind the microenvironment in which these proteins function, which can have a profound effect on their biological properties, since phospholipids play an important role in the initiation of the biomineralization process. The ability of synthetic or natural vesicles to mimic the organizational structure and function of biomembranes makes these structures an advantageous and convenient experimental model to help us advance our understanding of MV-mediated calcification2. The proteoliposome system provides a means of reconstituting lipid vesicles that will function like MVs3-5. Proteoliposomes can be manufactured using different methods and with controlled lipid and protein composition, electrolytes and sizes, representing a convenient experimental model to mimic the organizational structure and function of natural biomembranes and to reproduce some essential features of the biomineralization process2,6 1. Milln, Calcif. Tissue Int. 93(4):299-306. (2013). 2. Ciancaglini et al., Biophys. Rev. 4: 67-81 (2012). 3. Simo et al., J. Biol. Chem.285(10):7598-7609 (2010).

4. Bolean et al., Biophy. Chem. 152:74-79 (2010). 5. Bolean et al., Biophy. Chem. 158:111-118 (2011). 6. Ciancaglini et al., J. Bone Miner. Res. 25(4):716-723 (2010)


_____________________________________________________

28

CONFERENCIA 8 Control of the levels of PIP3: Structure and Function of the lipid kinase PI3Kalpha S.B. Gabelli b, Michelle Miller a, Ignacia Echeverria a, Yunlong Liu a, B. Vogelstein c, and L M. Amzel a a Department of Biophysics and Biophysical Chemistr.,bDepartment of Medicine and cLudwig Center for Cancer Genetics and Therapeutics and Howard Hughes Medical Institutions, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Phosphatidylinositide-3-kinase- (PI3K) is a lipid kinase that catalyzes the phosphorylation of PIP2 to produce PIP3 in response to phosphorylated receptor tyrosine kinases (RTK) or their substrates. The increased levels of PIP3 initiate a number of signaling pathways by recruiting other kinases, such as Akt, to the plasma membrane. The enzyme is composed of two subunits, p110 and p85, each comprising five domains. PI3K is frequently mutated in many cancer types and the mutations increase PI3K kinase activity leading to increased tumor cell survival, cell motility, cell metabolism, and cell cycle progression. Several atomic resolution structures of the enzyme reveal that the enzyme has a complex architecture in which each domain interacts with several domains of the same or the other subunit. The structural and other data show that physiological activation, as well as activation by some oncogenic mutations, involves relief of autoinhibition by dislodging the inhibitory nSH2 domain of the regulatory subunit p85 from its inhibitory position. Computational studies show that most of these effects involve, in addition to structural changes, modifications of the dynamics of the protein that alter the relative stabilities of the different states accessible to the enzyme. Recent progress toward determining the mechanism of activation benefited from two developments: the determination of the structure PI3K bound to short chain phosphoinositides, and the characterization of the conformations accessible to the activation loop in molecular dynamics simulations.


_____________________________________________________

29

SIMPOSIOSSIMPOSIOSSIMPOSIOSSIMPOSIOS


_____________________________________________________

30

SIMPOSIO 2 Regulation of Voltage gated sodium channels by Calmodulin Gabelli SB, Boto A, Halperin Kuhns V, Bianchet MA, Farinelli F, Aripirala S. Yodder J, Jakoncic J, Tomaselli GF, Amzel LM. a Structural Enzymology and Thermodynamics Group. Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N Wolfe St, WBSB 608, Baltimore, Maryland 21205, USA; bDivision of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. cDepartment of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA. dDepartment of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA. eBrookhaven National Laboratory, National Synchrotron Light Source, Upton, NY 11973 Voltage gated sodium channel are responsible for the rapid upstroke of action potential in tissues such as the heart, skeletal muscle and the brain (VGSC). VGSC fast and long inactivation are regulated by channel interacting proteins (CIP). We determined the structure of the complex of the cytoplasmic portion of a VGSC (Nav1.5; CTNav1.5) with a CIP, calmodulin (CaM), and Mg

2+ and show that both CaM lobes interact with the CTNav1.5. Based on the conformational differences between this structure and that of an inactivated complex, we propose that this structure represents a non-inactivated state of the CTNav1.5, i.e., the state that is poised for activation. Site-specific mutagenesis and patch clamp recordings further support the importance of the interactions identified. The dimerization of the Nav1.5 elucidates the effect of some dominant negative disease mutations and provides unique insights into the physiological activation and the pathophysiology of VGSC channels


_____________________________________________________

31

SIMPOSIO 2 Sterols in membranes: structural features that rule the interaction with phospholipids Wenz, JJ Instituto de Investigaciones Bioqumicas de Baha Blanca, Universidad Nacional del Sur, Camino La Carrindanga Km 7, B8000FWB Baha Blanca, Argentina. Tel +54(291)4861201. [email protected] The relationship between sterol structure and the effects on membrane properties is still controversial. This study introduces a multivariate analysis that relates the molecular structure with the activity of sterols on phospholipid bilayers. Chemical structures were encoded by using binary variables reporting on the presence/absence of substituents in the pentaneperhydrophenanthrene. The sterol activity was encoded regarding physical properties affected in sterol-containing membranes. By means of Principal Coordinates Analysis, the sterol population was grouped into five well-defined clusters according to structural similarities/differences. An examination of the sterol distribution between clusters revealed that a hydroxyl group at C3 and an 8-10 carbon chain at C17 are common in sterols having rigidifying, molecular ordering/condensing effects and/or a raft promoting ability. In contrast, sterol containing a keto group at C3, a C4-C5-double bond, and polar groups or a short alkyl side-chain at C17 (3 to 7 atoms) are mostly present in sterols having opposite effects. Combined with Logistic Regression, these approaches conclude that the most important structural features affecting the physical properties of sterol-containing mixtures were the presence of an 8-10 carbon C17 isoalkyl side-chain, followed by a hydroxyl group at C3 and a C5-C6 double bond. Finally, a simple structure-based Logistic Regression model that predicts the activity of sterols is proposed.


_____________________________________________________

32

SIMPOSIO 2 Lipid and protein aggregates activate receptors of the innate system. J-M Ruysschaert and C. Lonez Free University of Brussels-Belgium- [email protected] Toll-like receptors are major members of the Pattern Recognition Receptors (PRRs) from the innate immune system, which recognize bacterial or viral components. It was suggested that those receptors, that usually recognized molecular patterns characteristic of pathogens, are activated by lipid and protein ligands aggregated into particles and structurally different from the natural ligands. We will illustrate this aspect with two examples related to nanoparticles and neurodegenerative diseases (1,2) It is hard to believe that molecules which are so different from natural ligands do activate receptors the same way natural ligands do. How lipid and protein aggregates made of a large number of molecules activate pattern recognition receptors is still unknown but it is very likely that it proceeds via a mechanism quite different from what has been described so far for monomeric natural ligands. Implications in nanotechnologies(3) and nanomedicine will be briefly discussed.

1. Lonez C, Vandenbranden M, Ruysschaert JM.-Adv Drug Deliv Rev. 2012,64,1749-58

2. Gustot A, Raussens V, Dehousse M, Dumoulin M, Bryant CE, Ruysschaert JM, Lonez C.-Cell Mol Life Sci. 2013 Aug;70(16):2999-3012

3. Lonez C, Bessodes M, Scherman D, Vandenbranden M, Escriou V, Ruysschaert JM. Nanomedicine. 2014 -10(4):775-82


_____________________________________________________

33

SIMPOSIO 2 Structural Characterization of Heparin-induced GAPDH Protofibrils Preventing -synuclein Oligomeric Species Toxicity Csar vila1, Clarisa Torres-Bugeau1, Leandro Barbosa2, Elisa Morand Sales2, Mohand Ouidja3,4, Sergio Socas3, M. Soledad Celej5, Rita Raisman-Vozari3, Dulce Papy-Garcia4, Rosangela Itri2, and Rosana N. Chehn1, 1INSIBIO-CONICET-UNT(Tucumn) Argentine.2IFUSP (So Paulo) Brazil.3INSERM-CRICM, ICM, Thrapeutique Exprimentale de la neurodgnrescence (Paris) France.4CRRET, Universit Paris Est Crteil, France.5 CIQUIBIC, CONICET-UNT (Crdoba) Argentine. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional enzyme associated to neurodegenerative diseases. In a previous work, we showed that glycosaminoglycans-induced GAPDH prefibrilar species accelerates the conversion of -synuclein to fibrils. However, it remained to be determined whether the interplay among glycosaminoglycans, GAPDH and -synuclein has a role in pathological states. Here we demonstrate that the toxic effect exerted by -synuclein oligomers in dopaminergic cell culture is abolished in the presence of GAPDH prefibrilar species. Structural analysis of prefibrilar GAPDH performed by Small angle X-ray scattering, showed a particle compatible with a protofibril. Using biocomputational techniques we obtained the first all-atom model of the GAPDH protofibril, which was validated by cross-linking coupled to mass spectrometry experiments. Since GAPDH can be secreted outside the cell where glycosaminoglycans are present, it seems plausible that GAPDH protofibrils could be assembled in the extracellular space kidnapping -synuclein toxic oligomers. Thus, the role of GAPDH protofibrils in neuronal proteostasis must be considered. The data reported herein could open alternative ways in development of therapeutic strategies against synucleinopathies like Parkinsons disease.


_____________________________________________________

34

SIMPOSIO 3 Synaptic gain-of-function effects of mutant CaV2.1 channels in a mouse model of familial hemiplegic migraine are due to increased basal [Ca2+]i. Di Guilmi MN1; Gonzlez Inchauspe C1; Forsythe I2; van den Maagdenberg A3; Borst JG4; Uchitel OD1. 1IFIBYNE, UBA- CONICET, Buenos Aires, Arg.; 2MRC Tox. Unit, U.Leicester, Leicester. UK.;

3 Dep. of Hum Gen & Neurolog and Dep. of Neurol, Leiden U., Leiden, The Netherlands, 4 Dep. of Neurosc, Erasmus MC, Rotterdam, The Netherlands. Specific missense mutations in the CACNA1A gene, which encodes a subunit of voltage-gated CaV2.1 channels, are associated with familial hemiplegic migraine type 1 (FHM1), a rare monogenic subtype of common migraine with aura. We used transgenic knock-in (KI) mice harboring the human pathogenic FHM1 mutation S218L to study presynaptic Ca2+ currents and EPSCs in the MNTB-calyx of Held synapse. Whole-cell patch-clamp recordings of presynaptic terminals from S218L KI mice showed a strong shift of the calcium current I-V curve to more negative potentials, leading to an increase in basal [Ca2+]i, increased levels of spontaneous transmitter release, faster recovery from synaptic depression, and enhanced synaptic strength despite smaller action-potential-elicited Ca2+ currents. This synaptic phenotype may explain the misbalance between excitation and inhibition in neuronal circuits resulting in a persistent hyperexcitability state and other migraine-relevant mechanisms such as an increased susceptibility to cortical spreading depression.


_____________________________________________________

35

SIMPOSIO 3 ABA-1A: a Nematode Polyprotein Allergen (NPA) of Ascaris suum. Structure and binding properties. Franchini,GR1; Blgamo JA1, Kennedy, MW2; Smith, BO2 and Crsico, B1 1 INIBIOLP-CONICET, Fac.de Ciencias Mdicas, Universidad de La Plata, Argentina .

2 Institute of Biomedical & Life Sciences, University of Glasgow, United Kingdom

The acquisition and transport of lipids from their hosts is crucial to parasitic helminths, being the proteins and receptors involved in lipid transport and exchange potential targets for chemo- and immunotherapy. Among helminth lipid binding proteins (LBPs), the polyprotein allergens/antigens of nematodes (NPAs) represent a novel class of lipid binding proteins which has been described exclusively in nematodes. NPAs are small, helix-rich proteins, and have no known structural counterparts in other phyla. The biochemical activity of the NPA of A. suum was first described as a binding protein for small lipids such as fatty acids and retinoids. Recently, the structure of a single unit of the polyprotein array (ABA-1A) has been solved in the presence of saturating concentration of oleic acid describing two binding sites. In the present project we are working with ABA-1A in the absence of the ligand (apo- form) and its atomic structure is under analysis employing NMR spectroscopy, for which high quality data have already been obtained and full structure calculation is in progress. In order to obtain more information about the structural perturbations due to ligand binding; an oleic acid titration of ABA-1A monitored by NMR spectroscopy was performed. Briefly, it was possible to distinguish two binding events according to the nature of the perturbations observed. Additionally, as a first attempt to determine the natural ligands bound by this protein a lipidomic analysis was done using recombinant ABA-1A without the delipidation step.


_____________________________________________________

36

SIMPOSIO 3 Membrane role in the rational design of HIV fusion inhibitors Axel Hollmann1,2, Marcelo T. Augusto1, Susana Gregrio1, Pedro M. Matos1, Matteo Porotto3, Antonello Pessi4, Miguel A. R. B. Castanho1 and Nuno C. Santos1 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Portugal; 2Laboratory of Biointerfaces and Biomimetic Systems- CITSE- CONICET, Argentina. 3 Weill Medical College, Cornell University, New York, USA; 4PeptiPharma, Rome, Italy. The Human Immunodeficiency Virus type 1 (HIV-1) is a highly pathogenic and evasive virus, for which no cure has yet been achieved. Fusion of viral and host cell membranes is a crucial step in virus infectivity, therefore the development of viral entry inhibitors has great advantages since they prevent the release of the viral content into the host cell. In this work, we found that boosting membrane affinity of the established HIV fusion inhibitors C34 and enfuvirtide, by conjugation with lipid moieties, results in a dramatic increase of their antiviral activity. We demonstrated, by fluorescent partition, dipole potential assays and surface pressure assays, that these novel fusion inhibitors have membranotropic behavior towards biomembrane model systems and human blood cells membranes. The ability that these peptides have to bind to cell membranes facilitates the delivery of the peptides to this confined environment, as some peptide is already locally present. Beside the ability of membranes to concentrate the inhibitors locally, their role in the presentation of the peptide in the proper orientation for gp41 binding should also be considered. In this context, we also evaluated the location of the different peptides in the membrane, using aqueous and lipophilics quenchers. Overall, the results of this study offer a rational basis for the design of improved viral fusion inhibitors, since they suggest that maximizing antiviral activity requires finding the proper balance of membrane affinity and exposure of the peptide moiety. Moreover, we offer an experimental strategy to guide the development of the structure-activity relationship (SAR) towards this goal.


_____________________________________________________

37

SIMPOSIO 3 Effects of nitric oxide on heart mitochondrial calcium handling Zaobornyj T.1, Sivakumaran V.2, ORourke B.2 1Institute of Biochemistry and Molecular Medicine (IBIMOL, UBA-CONICET), School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina;

2Institute of Molecular Cardiobiology, School of Medicine, The Johns Hopkins University, Baltimore, USA Mitochondria provide the cells with both the energy and with the signals that command cell death and survival. Indeed, mitochondria are involved in the production of reactive oxygen species and in Ca2+ handling. The aim of this work was to evaluate heart mitochondrial function, in order to establish the effects of NO and Ca2+ in energy metabolism. Guinea pig heart mitochondria were exposed to NO released from GSNO and SNAP. Mitochondrial NO production, and Ca2+ uptake were followed simultaneously using a spectrofluorometer. Isolated mitochondria O2 consumption was assessed using an extracellular flux analyzer. Energized mitochondria were submitted to Ca2+ pulses (10 M) up to a final concentration of 80-100 M (200-450 nmol/mg protein), showing no significant alterations in matrix volume and . In the presence of NO donors (25 to 100 M), Ca2+ uptake was slower and extramitochondrial Ca2+ concentration increased. When single 50 M Ca2+ pulses were added, mitochondria treated with NO donors showed a decreased Ca2+ accumulation rate (40-50%) with an IC50 of 400 M (180 nM NO). The addition of L-arginine or NOS inhibitors to control mitochondria produced changes in Ca2+ uptake and in DAF-FM signal. State 4 O2 uptake was not modified by NO. The addition of Ca2+ to the medium produced a 20% enhancement in state 4-O2 consumption and this effect was abolished by NO. These results suggest that Ca2+ and NO act as signals that coordinate cytosolic workload and mitochondrial energy metabolism.


_____________________________________________________

38

SIMPOSIO 4 Mathematical models for cytoskeletal transport and cellular viscoelasticity Bouzat, S. Grupo de Fsica Estadstica e Interdisciplinaria, Centro Atmico Bariloche (CNEA). Argentina. CONICET. Argentina Molecular motors use the energy from ATP hydrolysis to move cargoes of radius 100-1000 nm along the cytoeskeletal filaments. For instance, the motor proteins kinesin and dynein drive cargo transport along microtubules, while myosin motors move on actin filaments. Due to the fact that the cytoplasm is a complex environment which is crowded by polymers and macromolecules, the motors have to overcome viscous and elastic responses from the medium. In this contribution we present a general model for active cargo transport inside cells [1,2]. It combines a Langevin description of the cargo motion with a Monte Carlo dynamics ruling the motor stepping, binding and unbinding processes. We also show the way in which the elastic responses of the medium can be taken into account [3]. This is done by considering a Generalized Langevin equation for the cargo motion or, equivalently, by introducing virtual environmental particles which interact harmonically with the cargo [3,4]. We discuss some of the modeling results in connexion with recent experiments in the literature.

1- A. Kunwar and A. Mogilner. Phys. Biol. 7 (2010) 016012. 2- S. Bouzat and F. Falo. Phys.Biol. 8 (2011) 066010 . 3- S. Bouzat. Phys. Rev. E. 89 (2014) 062707. 4- I. Goychuk, V. O. Kharchenko and R. Metzler. PLoS ONE 9

(2014), e91700.


_____________________________________________________

39

SIMPOSIO 4 Using Machine Learning for Predictive Modeling on Systems Biology and Molecular Informatics Ponzoni, I Instituto de Ciencias e Ingeniera de la Computacin (Universidad Nacional del Sur, CONICET) The use of machine learning methods for predictive modeling in life sciences is growing during last decades. In this lecture, we will present the development of different computational strategies based in these approaches in the context of Molecular Informatics and Systems Biology. The first part of this lecture is related to the development of quantitative structureactivity relationship (QSAR) models. These models play a central role in several industrial applications, such as drug discovery and design of new materials. The design of QSAR/QSPR models requires to solve several mathematical problems. For dealing with these issues, we are working in the design of computational methodologies based on machine learning and visual analytics for assisting experts in the design of new QSAR/QSPR models. The second application presented in this talk is related with the field of Systems Biology. We will focus on gene regulation and the ways that transcriptome data can be used to unravel the complex relationships between genes and pathways. In particular, we will describes the main topics that must be considered in the field of association rule mining for reverse engineering of biological networks and some techniques currently available in the literature.

1. Ponzoni I., Nueda M.J., Tarazona S., Gtz S., Montaner D., Dussaut J.S., Dopazo J., Conesa A. Pathway network inference from gene expression data, BMC Systems Biology, 8(S2):S7, 2014.

2. Soto, A.J., Vazquez, G.E., Strickert, M., Ponzoni, I. Target-driven subspace mapping methods and their applicability domain estimation, Molecular Informatics, 30:779789, 2011.


_____________________________________________________

40

SIMPOSIO 4 Water at the nanoscale: Towards new principles and design elements for biophysics Appignanesi, G. A. INQUISUR-UNS-CONICET and Depart.de Qumica, Universidad Nacional del Sur, Baha Blanca. A full comprehension of the behavior of water, the matrix of life, at the nanoscale would be essential in order to understand biology at a molecular level. In biological organization, water acts as a mediator between complex surfaces that associate by means of non-covalent interactions, producing nanoconfined environments where descriptions borrowed from the bulk might be useless and, thus, the development of a new intuition is demanded. For instance, as two hydrophobic surfaces in aqueous solution approach each other to a nanometric separation, the thermodynamic properties of the hydration water are affected to the point to produce the "drying" that triggers hydrophobic collapse. Also, a ligand is expected to replace easily removable hydration water in order to bind to a protein. Thus, the knowledge of how different nanoconfinement conditions affect the local hydrophobicity and modulate non-covalent interactions is of great significance both to understand and predict the behavior of biological systems and to emulate them in bioengineering efforts based on rational design. In this talk we shall present some preliminary studies aimed at identifying generalizable principles towards a picture of nanoconfined water of interest in biophysics. First, we will focus on model systems studying a number of properties such as water density fluctuations. We shall investigate generic contexts with controlled chemistry and geometry in order to determine how chemical topology and topography define the local hydrophobicity. We also aim at determining the context-dependence and the (possibly non-additive) mutual interplay between different non-covalent interactions, attentive to the detection of design elements of general validity. Finally, we shall also tackle more specific contexts such as protein binding, the rational design of small molecules predecessors of disruptive drugs and membrane hydration.


_____________________________________________________

41

SIMPOSIO 5 How do Sco Proteins Score the COX? Morgada MN1, Abriata LA2 and Vila AJ1 1Laboratorio de Metaloprotenas, Instituto de Biologa molecular y Celular de Rosario (IBR-CONICET), Depto. de Qca. Biol, Fac. de Cs. Bioq. y Farm, Universidad Nacional de Rosario (UNR), Argentina. 2Swiss Federal Institute of Technology, cole Polytechnique Fdrale de Lausanne (EPFL), Switzerland The dinuclear copper center CuA is the electron entry point of the cytochrome c oxidase (COX) and the correct assembly of this metal center is essential for the function of the complex and thus for the survival of the cell. Following the copper transfer reactions using NMR, our group proposed a mechanism for the insertion of the copper ions to the CuA center of bacterial COX. Bacterial Sco, despite its ability to bind copper ions, keeps the cysteines from the CuA center in the reduced state thus the copper ions can be transferred from a periplasmic metallochaperone (PCuAC). In the case of humans, biochemical studies shown several proteins involved in the assembly of COX. Two of the identified proteins, Sco1 and Sco2 are directly involved in the formation of the CuA center in subunit II (COX II) and structural studies showed that both proteins can act as metallochaperones or as thiol-disulphur oxidoreductases since both proteins has two Cys residues in their copper biding site. The unavailability of the soluble domain of an eukaryotic COX II has stalled further investigation but using a model of the eukaryotic oxidase (COX II*), we have been able to assess the function of these Sco proteins finding that Sco1 act as copper transfer protein while Sco2 is crucial in the maintenance of the cysteines redox state homeostasis.


_____________________________________________________

42

SIMPOSIO 5 On the Search of a Comprehensive Representation of Human Frataxin Aran M1, Faraj SE, Gallo M1, Noguera ME2, Gonzlez Lebrero R1, Roman EA1 and Javier Santos1 1Fundacin Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405, 2IQUIFIB, Universidad de Buenos Aires, Junn 956, 1113AAD, Buenos Aires. Friedreichs ataxia (FRDA) is a neurodegenerative disease linked to a deficiency of frataxin (FXN), a protein involved in iron-sulfur cluster biosynthesis. Human FXN contains a folded Cterminal domain starting at residue 90 with / topology followed by a C-terminal region (CTR) that packs against the proteins core. We have investigated the impact of the alteration of the CTR on the stability, internal dynamics and folding dynamics of FXN. The pathological mutation L198R yields a global destabilization and a significant and highly localized alteration of dynamics, mainly involving residues that are in contact with L198 in wild-type FXN. Variant FXN90195, which is closely related to the FRDAassociated mutant FXN81193, preserves its native-like structure. However, the truncation of the CTR results in an extreme decrease of global stability and alteration of protein dynamics over a vast range of timescales, including regions far from the CTR. Moreover, both mutants exhibit an important deficiency in iron-binding, suggesting coupling dynamics between the CTR and the acidic ridge (helix 1, loop1, strand 1) involved in iron binding. The increased sensitivity to proteolysis observed in vitro, the reduced ability to bind iron, and the enhanced tendency to aggregate exhibited by the truncated variant may explain why the alteration of the CTR causes FRDA. The alteration of the dynamics and stability of FXNL198R is in line with the rapid disease progression observed in patients carrying this mutation. Folding kinetic experiments firmly suggest that the change in global stability observed in CTR mutations is most probably caused by a native-state destabilization than by a change in the stability of the transition state ensembles. These results contribute to understanding how stability and activity are linked to protein motions, and might be valuable for the design of target-specific binders to control local protein motions for stability and activity enhancement.

Authors are listed in alphabetical order. Correspondence: [email protected]. Thanks to UBACyT, CONICET and ANPCyT.


_____________________________________________________

43

SIMPOSIO 5 Ligand binding mechanisms of bitter taste receptors: Insights from multiscale simulation approaches Giorgetti, Alejandro Computational Biophysics, German Research School for Simulation Sciences, Juelich, Germany and Department of Biotechnology, University of Verona, Verona, Italy Sensing chemicals present in the food is of fundamental importance for the survival of the species. Life evolved a host of mechanisms to communicate chemical information from the environment to elicit cellular responses that provide an advantage in avoiding or seeking the chemical signatures of foods, mates, toxins, etc. In particular, mammals during evolution have been prevented from ingesting toxic compounds because of their strong bitter taste. This protection mechanism has been carried out by a family of 25 bitter taste receptors (TAS2Rs). A characterization of the mechanisms underlying their function is lacking. Here I will present our studies on the interaction of TAS2R38 [1] with two of its agonists. Indeed, by using a combination of homology models together with docking [2], molecular mechanics/coarse-grained (MM/CG) simulations [3] and experimental data, we were able to provide a detailed description of the ligand-binding site in the receptors, satisfying site-directed mutagenesis experiments [4]. Our approach could be used for other GPCRs with direct applications in drug design.

1. Biarns X.;et al., PLoS ONE 5(8): e12394 (2010). 2. Sandal, M et al. Plos ONE. 8(9): e74092 (2013) 3. Legube M, et al.. PLoS ONE 7(10): e47332 (2012). 4. Marchiori et al. PLoS ONE 8(5): e64675. (2013)


_____________________________________________________

44

SIMPOSIO 5 A simple model to simulate protein-membrane interactions with inclusion of electrostatics. Villarreal MA 1, Emperador A2,3, Sfriso P2,3, Leiva EPM1, Orozco M2,3,4,5. 1INFIQC-Dpto Matemtica y Fsica. CONICET-Universidad Nacional de Crdoba. Argentina. 2Institute for Research in Biomedicine, Barcelona, Spain. 3Joint IRB-BSC Program in Computational Biology, Barcelona, Spain. 4Barcelona Supercomputing Center, Barcelona, Spain. 5Department of Biochemistry and Molecular Biology, University of Barcelona, Spain. We present a minimalistic model to describe protein-membrane interactions with inclusion of electrostatics. One bead per aminoacid is used to describe protein structure, centered in the alpha carbon position. Structure-based potentials were used to model particle-particle interactions within the protein. The lipid bilayer is represented as five slabs, which account for the water phase, the lipid headgroup, and the membrane interior. The interaction of the protein with the membrane is modeled with two terms. One is based on lipid-water partition coefficients and the exposed surface area of each amino acid, while the second term accounts for the electrostatic interaction with charged residues only. Both interaction potentials are modeled with discrete changes in energy, and therefore can be used in discrete molecular dynamics simulations (DMD). Here we present the calibration of the model against experimental data of binding constants, and also selected applications of the model.


_____________________________________________________

45

SIMPOSIO 6 Mechanical and thermodynamic properties of lipid membranes using optical microscopy Wilke, N Centro de Investigaciones en Qumica Biolgica de Crdoba (CIQUIBIC). Departamento de Qumica Biolgica, Facultad de Ciencias Qumicas, Universidad Nacional de Crdoba. E-mail: [email protected] Depending of the conditions and of the mixture, lipid membranes may show phase segregation with a fluid phase and a denser phase coexisting in the film. The distribution of the phases (texture of the membrane) depends of the line tension, the electrostatic repulsion and of curvature effects of each phase, while the amount of each phase depends of the energy of mixing of the lipids and of the proportions of them in the mixture. The relative amount of the phases and the manner in which they distribute modulates the compressibility and the apparent viscosity of the membrane. In this presentation, we will discuss how the line tension, electrostatic interaction and phase diagram of lipid mixtures can be determined using optical microscopy. The membrane was studied by pasive two-particle rheology and manipulating the film with electrical fields. Results found with different models of biomembranes are compared and the effect of two phases on the mechanical properties of the film is also described. The molecular determinants for the line tension in a system are discussed along with the possibility of its modulation with linactants. Acknowledgements: SecyT-UNC, CONICET and FonCyT (PICT 2012-0344)


_____________________________________________________

46

SIMPOSIO 6 Dynamics and interactions of transcription factors in the cell nucleus through fluorescence fluctuation spectroscopy Levi, V. Departamento de Qumica Biolgica- IQUIBICEN. Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires-Argentina Fluorescence fluctuation spectroscopy (FFS) methods are powerful techniques to explore the dynamical organization of cells. These methods are based on analyzing the fluorescence intensity fluctuations caused by molecules moving through the observation volume of confocal or two-photon excitation microscopes. The quantitative analysis of these fluctuations provides important clues regarding the mobility of the molecules and their interactions with other species. In this talk, we show applications of different FFS-based methods to explore relevant aspects of the mechanisms of action of transcription factors (TFs). First, we demonstrate the utility of fluorescence correlation spectroscopy (FCS) for measuring the dynamics of the TFs Oct4, Sox2 and Cdx2 involved in embryonic development at the level of a single cell in early mouse embryos. The combination of Monte Carlo simulations with photoactivatable FCS allowed us to distinguish specific and non-specific DNA binding of TFs and track their dynamics during embryonic development. In another example of application of FFS methods, we studied the mechanism of action of the glucocorticoid receptor (GR) though number and brightness analysis (N&B). Glucocorticoids bind to GR, a ligand-dependent transcription factor, and regulate gene expression directly by binding to DNA or indirectly by modulating the activity of other transcription factors. It is currently accepted that the direct pathway is mostly responsible for glucocorticoids side-effects and that the oligomerization state of the GR determines which pathway (direct or indirect) will prevail. Our analyses allowed us to directly measure the oligomerization state of GR and thus to test this established model.


_____________________________________________________

47

SIMPOSIO 6 Far-field fluorescence nanoscopy of neurons Bordenave, M Centro de Investigaciones en Bionanociencias - CIBION, CONICET, Godoy Cruz 2390, C1425FQD Buenos Aires. Departamento de Fsica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. Far-field fluorescence nanoscopy methodologies, also known as super-resolution fluorescence microscopy are the future of fluorescence based visualization. This family of techniques include wide-field and scanning methods, such as PALM/STORM and STED, respectively, and provide spatial resolutions of 20-80 nm maintaining the low invasivity of fluorescence microscopy. In this contribution I will first present the fundamental concepts of fluorescence nanoscopy and describe the most popular methodologies, remarking their comparative advantages and limitations. Secondly, I will present the fluorescence nanoscopy facilities at CIBION, which are available through the Sistema Nacional de Microscopa and finally, I will give some examples of the biological questions being currently addressed with nanoscopy in our group: i) Restructuring of citoesqueleton of growth cones and initial axon segments during the neuronal polarization process (in collaboration with the group of Alfredo Cceres - INIMEC, CONICET), and ii) restructuring of pre- and post-synapse regulated by Nedd8 (in collabotation with the group of Damin Refojo - IBIOBA, CONICET).


_____________________________________________________

48

SIMPOSIO 7 Two signaling pathways mediate presynaptic voltage gated calcium channels inhibition by two ghrelin receptor activation modes. Jesica Raingo. Electrophysiology Laboratory. Multidisciplinary Institute of Cell Biology (IMBICE) La Plata Buenos Aires Argentina [email protected] Growth hormone secretagogue receptor type 1a (GHSR1a) has the highest constitutive activity of any G protein coupled receptor (GPCR). GHSR1a mediates the orexigenic effects of the gut-derived hormone ghrelin. It is a therapeutic target of anti-obesity drugs and of several eating disorder treatments. GHSR1a is present at presynaptic terminals in the hypothalamus and it regulates neuronal activity, but the mechanism of its actions remains poorly understood. Presynaptic voltage gated calcium channels, CaV2.1 and CaV2.2, control neurotransmitter release and their activities are modulated by GPCRs. Here we show that constitutive as well as agonist-dependent GHSR1a activation triggers a strong impairment of both CaV2.1 and CaV2.2 currents. Constitutive GHSR1a activity reduces CaV2 currents by a Gi/o-dependent mechanism that involves persistent reduction in channel numbers in the plasma membrane, whereas, ghrelin-dependent GHSR1a inhibition is reversible and involves altered CaV2 current gating via a Gq-dependent pathway. Thus we show that GHSR1a differentially inhibits CaV2 channels by Gi/o or Gq pathways depending on whether GHSR1a activation is constitutive or ghrelin-dependent respectively, and probably impacting on neuronal activity.


_____________________________________________________

49

SIMPOSIO 7 Redox modulation of the GABAergic neurotransmission in the retina and the hippocampus. Calvo, D.J. INGEBI CONICET y-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system and its actions are mediated by two receptor classes: ionotropic (GABAA) and metabotropic (GABAB). GABAA receptors are ligand-gated chloride channels that belong to the superfamily of Cys-loop receptors which also include the nicotinic acetylcholine, glycine and serotonin 5HT3A receptors. Heteromeric and homomeric GABAA receptor variants can be assembled from a great diversity of subunit subtypes (1-6, 1-3, 1-3, , , , , 1-3). Studies from our lab revealed that the extra and intracellular levels of ascorbic acid in the retina regulate the function of tonic (GABAA1) and phasic (GABAA122) receptors expressed in bipolar cells. We have also demonstrated that tonic GABAA1 receptors are sensitive to endogenous redox agents such as ascorbic acid, glutathione, reactive oxygen species and reactive nitrogen species. The aminoacidic residues which act as targets for redox agents were identified using site directed mutagenesis and receptor expression in oocytes. Preliminary results indicate that responses mediated by tonic and phasic GABAergic receptors in the hippocampus are also subject to redox modulation. Taken together our results suggest that inhibitory neurotransmission mediated by ionotropic GABA receptors is modulated by multiple pathways involving redox signaling.


_____________________________________________________

50

SIMPOSIO 7 Proton permeation in Ci-Hv1 voltage-gated proton channels occurs through a proton wire involving residues D160 and D222 and it is modulated by N264. Amaury Pupo1,2, David Baez-Nieto1, Ester Otarola1, Osvaldo Yaez3, Ariela Vergara-Jaque3, Wendy Gonzalez3, Karen Castillo1, Gustavo Contreras1, Ramn Latorre1, Carlos Gonzalez1. 1Centro Interdisciplinario de Neurociencia de Valparaiso. Universidad de Valparaiso, Chile. 2Doctorado en Ciencias, mencin Neurociencias. Universidad de Valparaiso. 3Universidad de Talca, Chile. Hv1 channels are integral membrane proteins with the capacity to selectively permeate protons in a voltage and pH dependent manner. As Hv1 lacks a pore domain, permeation must occur through the voltage-sensing domain. Previous reports propose a permeation pathway consisting in an stable water wire which allows proton to permeate by a Grotthuss mechanism. Our molecular dynamics simulations do not support the formation of such stable water wires throughout all the channel pore, existing a dry zone around residue N264. Mutations in position 222 and 264 affects single channel conductance (determined by non-stationary noise analysis) and selectivity, suggesting that both residues are involved in the permeation pathway. Quantum dynamics simulations performed in our models of Ci-Hv1 wt and mutants suggest that permeation occur through a proton wire involving residues D160 and D222, a process modulated by N264. Supported by Beca de Doctorado Nacional para Extranjeros de Conicyt (A.P), FONDECYT Grants 1110430 (R.L.), 1120802 (C.G.); ANILLO Grant ACT1104 (C.G.); Postdoctoral Fellowships 3140590 (G.F.C.). CINV is a Millennium Institute.


_____________________________________________________

51

SIMPOSIO 7 The role of auxiliary 1 subunit of the BKCa channel as a tissue selective target for endogenous and exogenous substances Milesi V. Laboratorio de Canales Inicos, IIFP CONICET-UNLP, La Plata, Argentina. BKCa channel is activated by membrane depolarization and intracellular Ca2+ concentration. It is a tetramer of pore-forming -subunits (encoded by KCNMA1 gene, also named Slo1) and can be associated with one of four auxiliary -subunits codified by KCNMB1-4 genes. Each one of these subunits confers distinctive functional and pharmacological properties of the resulting channel complex. Differential expression of -subunits could explain the diversity of functions and regulations on BKCa channel among diverse tissues and cells, and could be used to obtain a tissue-selective BKCa channel activation, using the auxiliary subunit as a specific molecular target. An example of this is the activation of BKCa channels by lithocholate, which is only observed in presence of 1-subunit. Using patch-clamp technique on isolated human vascular smooth muscle cells (VSMCs), we showed that arachidonic acid (AA), a physiologically relevant 20-carbon omega-6 polyunsaturated fatty acid, increases the open probability (Po) of BKCa channel tenfold, mainly by a reduction of closed dwell times and also induces a left-shift in Po versus voltage curves without modifying their steepness. Furthermore, AA accelerates the kinetics of the voltage channel activation by a fourfold reduction in latencies to first channel opening. When AA was tested on BKCa channel expressed in HEK cells with or without the 1-subunit, activation only occurs in the presence of the 1-subunit. Understanding the molecular basis of the interactions of the and subunits in relation to the selective action of endogenous and exogenous substances define another novel physiological modulation point to the role that the BKCa channel plays in each tissue.

XLIII RA SAB 2014 POSTERS

_____________________________________________________

52

POSTERS

XLIII RA SAB 2014 BIOENERGETICS AND ELECTRONIC TRANSFER

_____________________________________________________

53

BIOENERGETICS

AND ELECTRONIC

TRANSFER


_____________________________________________________

54

BET-1] Inhibition of mitochondrial complex III by NO involves ubisemiquinone formation Iglesias, D.E; Bombicino, SS; Valdez, L.B; Boveris, A Institute of Biochemistry and Molecular Medicine (IBIMOL; UBA-CONICET), Physical Chemistry Division, School of Pharmacy and Biochemistry, University of Buenos Aires, Junn 956, C1113AAD, Buenos Aires, Argentina. The effect of NO on mitochondrial complex III was studied using bovine heart-submitochondrial particles (SMP). GSNO (25-500 M) and SPER-NO (2.5-30 M) inhibited complex II-III activity (222 4 nmol/min.mg protein) in a concentration dependent manner, and produced a hyperbolic increase in O2

- production rate (up to 1.3 0.1 nmol/min.mg protein). Considering that complex III produces O2

- by autoxidation of ubisemiquinone (UQH), the aim of this work was to evaluate through EPR the formation of UQH as a result of NO interaction with complex III. In the presence of succinate, SMP showed an EPR signal at g~1.99 that could be attributed to UQH implicated in the Q cycle. This signal was 42% increased by antimycin addition. The incubation of SMP with antimycin plus myxothiazol avoided the UQH formation. The UQH signal was completely absent if the SMP were previously denatured. In the presence of 500 M GSNO (~1.3 M NO) or 20 M SPER-NO (~1.0 M NO), the EPR signal was increased by 33% and 34%, respectively. When GSNO plus mixothiazol were simultaneously added to the reaction medium, the signal was not observed, similarly to the effect observed by the addition of antimycin plus myxothiazol. The EPR spectra obtained under N2 atmosphere were similar to the ones obtained in air saturated conditions, suggesting that UQH signal is not caused by NOx species on complex III area. In conclusion, NO inhibits the ubiquinone-cytochrome b area leading to an UQH steady-state concentration enhancement which, in turn, increases O2

- production rate


_____________________________________________________

55

BET-2] Complex I functionally interacts with mitochondrial nitric oxide synthase (mtNOS) Bombicino, S.S; Iglesias, D.E; Zaobornyj, T; Boveris, A; Valdez L.B. Institute of Biochemistry and Molecular Medicine (IBIMOL; UBA-CONICET), Physical Chemistry Division, School of Pharmacy and Biochemistry, University of Buenos Aires, Junn 956, C1113AAD, Buenos Aires, Argentina. The functional association between complex I and mitochondrial nitric oxide synthase (mtNOS) was studied. Bovine heart phosphorylating electron transfer particles (ETPH-Mg2+) showed a NAD+ reductase activity of 13.6 0.7 nmol/min.mg protein, sustained by reversed electron flow of the respiratory chain, at expenses of ATP when succinate was added. This activity was inhibited by rotenone (88%), oligomycin (98%) and m-CCCP (93%). ETPH-Mg2+ produced NO at a rate of 0.79 0.06 nmol NO/min.mg protein by the classic NOS reaction. In the presence of 0.5 mM MgCl2 and 0.3 mM KCN and of the compounds needed to carry out the reverse electron flow, ETPH-Mg2+ produced 0.46 0.03 nmol NO/min.mg protein by electron transfer from complex I to mtNOS. Rotenone inhibited (80%) mtNOS activity supported by reversed electron flow, but that inhibitor did not reduce the activity of isolated nNOS, indicating that the inhibitory effect of rotenone on NO production by ETPH-Mg2+ is due to an electron flow blockage and not to a direct action on mtNOS structure. A heart mitochondrial fraction enriched in complex I was recognized by anti-nNOS antibodies. Altogether, the data obtained in ETPH-Mg2+ suggest that complex I interacts physically and functionally with mtNOS. Electrons from reversed electron flow or from complex I reductants support NO production, in agreement with the dependences of mtNOS activity on mitochondrial metabolic state and on membrane potential.


_____________________________________________________

56

BET-3] Effects of nitric oxide on heart mitochondrial calcium handling Zaobornyj T.1, Sivakumaran V.2, ORourke B.2 1Institute of Biochemistry and Molecular Medicine (IBIMOL, UBA-CONICET), School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina; 2Institute of Molecular Cardiobiology, School of Medicine, The Johns Hopkins University, Baltimore, USA. Mitochondria provide the cells with both the energy and with the signals that command cell death and survival. Indeed, mitochondria are involved in the production of reactive oxygen species and in Ca2+ handling. The aim of this work was to evaluate heart mitochondrial function, in order to establish the effects of NO and Ca2+ in energy metabolism. Guinea pig heart mitochondria were exposed to NO released from GSNO and SNAP. Mitochondrial NO production, and Ca2+ uptake were followed simultaneously using a spectrofluorometer. Isolated mitochondria O2 consumption was assessed using an extracellular flux analyzer. Energized mitochondria were submitted to Ca2+ pulses (10 M) up to a final concentration of 80-100 M (200-450 nmol/mg protein), showing no significant alterations in matrix volume and . In the presence of NO donors (25 to 100 M), Ca2+ uptake was slower and extramitochondrial Ca2+ concentration increased. When single 50 M Ca2+ pulses were added, mitochondria treated with NO donors showed a decreased Ca2+ accumulation rate (40-50%) with an IC50 of 400 M (180 nM NO). The addition of L-arginine or NOS inhibitors to control mitochondria produced changes in Ca2+ uptake and in DAF-FM signal. State 4 O2 uptake was not modified by NO. The addition of Ca2+ to the medium produced a 20% enhancement in state 4-O2 consumption and this effect was abolished by NO. These results suggest that Ca2+ and NO act as signals that coordinate cytosolic workload and mitochondrial energy metabolism.

XLIII RA SAB 2014 ENZYMOLOGY

_____________________________________________________

57

ENZYMOLOGY


_____________________________________________________

58

EZ-1] Effect of CHAPS and Tween-20 on the measurement of enzymatic activity of dengue virus's NS3 Cababie LA1, Incicco JJ1, Gebhard LG2, Gamarnik AV2, Gonzlez-Lebrero RM1, Kaufman SB1 1Instituto de Quimica y Fisicoquimica Biologicas y Deperatemento de Quimica Biologicas, Facultad de Farmacia y Bioquimica, Universidad de Buenos Aires, Argentina 2Fundacion Instituto Leloir-Consejo Nacional de investigaciones Cientificas y Tecnicas, Ciudad de Buenos Aires, Argentina The dengue virus's NS3 protein is a helicase that catalyzes the hydrolysis of ATP and couples the free energy of this reaction to drive translocation on single strands and unwinding double strands of RNA. A frequent experimental problem encountered working with enzymes is the loss of specific catalytic activity when this measurement is performed at low enzyme concentrations. Therefore we examined whether the presence of detergents in the reaction medium during activity measurements is able to overcome this difficulty. We will present experimental results which show that two detergents of different chemical nature such as CHAPS (3 - [(3-Cholamidopropyl) dimethylammonio] -1- propanesulfonate) and Tween 20 (Polyoxyethylene (20) sorbitan monolaurate) keep the catalytic activity constant regardless of the concentration enzyme used. With grants from Universidad de Buenos Aires (UBACyT), CONICET, and ANPCyT


_____________________________________________________

59

EZ-2] Productive Induced Metastability (PIM): a new concept compatible with 50 years of history in the study of the allosteric regulation mechanisms. Montes de Oca J.M.1, Rodriguez-Fris A1., Appignanesi G.A1. 1Seccin Fisicoqumica, INQUISUR-UNS-CONICET-Departamento de Qumica, Universidad Nacional del Sur, Avda. Alem 1253, 8000 Baha Blanca, Argentina

Already in the middle of the last century, Lumry R., Eyring, Biltonen and others reported that allosteric signaling is an activated process that requires the presence of structural or mobile defects to change the free energy of the protein and promote the ligated state. In particular, Lumry refers to the distortions of the H-bonds and local structures as the driving forces of "fluctuating enzymes"1,2.In this study, we elucidate the allosteric binding modality by unraveling a local structural motif that promotes association with the ligand. We specifically show that allosteric modulators promote a local metastable state that is stabilized upon association. The induced conformational change generates a local enrichment of the protein in the so-called dehydrons3, which are solvent exposed backbone hydrogen bonds. These structural deficiencies that are inherently sticky are not present in the Apo form and constitute a local metastable state that promotes the association with the ligand. In other words, we find that the allosterically activated conformation of the enzyme could not prevail in the ensemble of conformations of the Apo form of the enzyme because of the inherent instability of the packing defects (the Lumry "mobile defects"). Therefore the allosteric ligand acts protecting these exposed Interaction from water, thus turning the active state into the most stable configuration. This productive induced metastability4 (PIM) is likely to translate into a general molecular design concept.

1. Lumry R & Eyring H (1954) Conformational changes in proteins, J. Phys. Chem. 58, 110-120.

2. Lumry, R., The new paradigm for protein research, in Gregory R B (ed.), Protein-solvent interactions, Marcel Dekker, Inc. New York (1995).

3. Fernndez A, Transformative Concepts for Drug Design: Target Wrapping (Springer, Heidelberg, 2010).

4. Montes de Oca J., Rodriguez-Fris A., Appignanesi G. and Fernndez A. Productive induced metastability in allosteric modulation of kinase function, FEBS J ,281, 30793091 (2014).

XLIII RA SAB 2014 LIPIDS AND BIOMEMBRANES

_____________________________________________________

60

LIPIDS AND

BIOMEMBRANES


_____________________________________________________

61

LBM-1] Surface Properties of Insulin-DPPC/POPC mixed Langmuir monolayers. Grasso E.J, Oliveira R.G, Maggio B. Centro de Investigaciones en Qumica Biolgica de Crdoba (CIQUIBIC-CONICET), Dpto. de Qumica Biolgica, Facultad de Ciencias Qumicas, Universidad Nacional de Crdoba. Pabelln Argentina, Ciudad Universitaria, X5000HUA, Crdoba, Argentina.

The surface properties of the binary mixed Langmuir monolayers of Insulin and DPPC (dipalmitoylphosphatidylcholine) and POCP (palmitoyloleylphosphatidylcholine) spread at the air-water interface was studied. Pure and mixed monolayers were spread on Zn2+ containing solutions. Miscibility and interactions between the components were studied on the basis of the analysis of the surface pressure-mean molecular area isotherms, surface compressional modulus and plots of mean molecular area and surface potential versus mole fraction of Insulin. Our results indicate that the intermolecular interactions between Insulin and DPPC/POPC depend on both the monolayer state and the structural characteristics of Insulin at the interface, which is strongly influenced by the Zn2+ ions in the subphase (1). Brewster angle microscopy was applied to describe the surface topography of the monolayers. We concluded that Insulin forms mixed surfaces with DPPC/POPC at all the mole fraction studied.

1 Grasso EJ et al. Colloids and Surfaces B. 2014, 219.


_____________________________________________________

62

LBM-2] Detection of lipid bilayer formation in macroporous Silicon by EPR spectroscopy Len X.a, Forzani L.b, Garcs F.b, Rodi P.M.d, Osorio E.b, Koropecki R.R.b,c, Gennaro A.M.b,d a Centro de Investigacin en Dispositivos Semiconductores, Universidad Autnoma de Puebla CIDS-ICUAP, 14 sur y Av. San Claudio, San Manuel, 72570 Puebla, Mxico. b Instituto de Fsica del Litoral (CONICET-UNL), Gemes 3450, 3000 Santa Fe, Argentina. c Facultad de Ingeniera Qumica, UNL, Santiago del Estero 2829, 3000 Santa Fe, Argentina. d Facultad

Documents

biofisica.org.ar.ca1.toservers.combiofisica.org.ar.ca1.toservers.com/reunion2014/files/... · 2014-12-04 · XLIII RA – SAB 2014 COMISIONES Y COMITÉS _____________________________________________________