Lomonosov Moscow State UniversityPhysics Department
SPECIFIC INTERACTION OF ALBUMIN
MOLECULES IN WATER SOLUTION,
CONTAINING SILICON NANOPARTICLES
AT DIFFERENT NET CHARGE OF PROTEIN
Ksenia A. Anenkova, Galina P. Petrova,Lubov A. Osminkina, Konstantin P. Tamarov.
Bovine Serum Albumin (BSA) Mesoporous Silicon
nanoparticles (MP-Si nanoparticles)
Molecular weight – 65 kDa
Characteristic sizes – 4*4*14 nm
Isoelectric point pH 4.9
Albumin molecules realize transport
function and maintenance of colloid-
osmotic pressure in blood.
Owing to their biological compatibility
with living tissues and ability of fast
removal from the organism, the silicon
nanoparticles may be used as
photosensitisers in photodynamic therapy
of cancer and as drug delivery systems.
Experimental setup
Fig.1. Autocorrelation function of
scattered light
g(1)(t) is first order field correlation function, g(2)(t) is second order intensity auto-correlation function, accumulated by correlator during the experiment
Fundamental formula:
In case of a poly-dispersed solution :
Main parameters: laser’s wavelength 647nm, power P=25mW
Fig.2. pH dependence of the scattering centers translation
diffusion coefficient in BSA water solution
B=V 1M 22 ( Z 24m3
+β222
−β232 m3
4+ 2β33m3 ) D t=D0 {1+ (2BM− [η ] ) c }
According to Scatchar theory nonlinear character of dependence at fig.1 is described by next formula where B is the second virial coefficien in the expansion for free energy, known as coefficient of intermolecular interaction
Fig.3. pH dependence of the scattering centers translation
diffusion coefficient in mesoporous silicon nanoparticles water
solution
Mesoporous silicon nanoparticles are hydrophilic. Due to this property a
water shell is formed around them. This leads to a partial shielding of particles
net charge. Therefore, the shape of dependence at fig.3 is more smooth.
Fig.4. pH dependence of the scattering centers translation diffusion
coefficient in mesoporous silicon nanoparticles + BSA water solution
Images of MP-Si nanoparticles, obtained by TEM
In water solution MP-Si nanoparticles
exist as clusters with sizes ranging from
100 nm to 1 mm.
Ultrasonic treatment, followed by
filtration, allows us to select the desired
particles size.
136.42нм
tD
kTR
6
Comparison of the results obtained
by dynamic light scattering with TEM
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1
2
3
IR spectrometer Bruker IFS 66v/S
IR spectroscopy is widely used to determine the composition of porous silicon layers.
Technical
characteristics:
Scanning range:
7500 – 370 сm-1
Resolution: 0.25 сm-1
Evacuating the
measuring chamber to 3
mbar
Fig.5. IR transmission spectrum for Mp-Si nanoparticles
in the range from 800 to 2500 сm-1
• SiH3 antisymmetric deformation vibrations 877сm-1
• SiO stretching vibrations in Si-O-Si 1064сm-1
• SiH stretching vibrations in O3-SiH 2266сm-1
•Amide-I (С=O stretching vibrations ) 1650 cm-1
•Amide-II (CN stretching vibrations and NH deformational vibrations) 1520 cm -1
•COO- 1390 cm-1
•Amide-III (CN stretching vibrations and NH rotating) 1220-1330 cm-1
Fig.6. IR transmission spectrum for BSA in the range from 800 to 2000 сm -1
What are we looking for in the IR-spectrum BSA+MP-Si nanoparticles?
Fig.7. IR transmission spectra for BSA and BSA+lead acetate in the range from 800 to 2000 сm-1
We are looking for amide-I and amide-II bands frequencies shifts. This shifts detect
secondary structural changes caused by interaction of nanoparticles and protein.
The examples of such shifts for system BSA+ lead acetate are shown at fig.7 For this
system is well known that there is an interaction between BSA macromolecules and
lead acetate.
Fig.8. IR transmission spectrum for BSA+Mp-Si nanoparticles in the range
from 800 to 1800 сm-1
There is no any shifts of amide-I or amide-II bands in BSA+MP-Si nanoparticles system
compared to pure protein. So it means that there is no interaction in this system.
Hydrophilic properties of MP-Si nanoparticles can explain the absence of interaction
between the nanoparticles’ surface OH groups and CO groups of BSA
The absence of OH- CO groups interaction also can be explained by unsufficient for stable
bond amount of H on the surface of particles
Conclusions:
• The investigation of molecular parameters of serum albumin in water
solution by DLS method has shown that the addition of nanoparticles
does not change the mobility of the scattering particles within the
experimental error.
• In the obtained IR spectra is not observed shift to short wave area,
characteristic for the formation of hydrogen bonds between the
carbonyl groups of the protein and the OH groups on the silicon
nanoparticles surface (shoulder 1650 for C = O stretching vibrations)
• Present results show that there is no interaction between albumin
molecules and silicon nanoparticles in the investigated systems.
Thank you for your attention!If you have any questions, I will gladly answer them by e-mail