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Ajax Group. Joshua P. Layfield Jordan C. Vincent Desiree M. Bates Ashley K. Tucker Sara E. Ray Ron C. Estler. Mechanism of Ionization in Matrix-Assisted Laser Desorption Ionization (MALDI): How does proton transfer occur. http://pslc.ws/mactest/maldi.htm. MALDI Overview. - PowerPoint PPT Presentation
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Mechanism of Ionization in Matrix-Mechanism of Ionization in Matrix-Assisted Laser Desorption Ionization Assisted Laser Desorption Ionization
(MALDI):(MALDI):How does proton transfer occurHow does proton transfer occurAjax Group
http://pslc.ws/mactest/maldi.htm
Joshua P. Layfield Jordan C. VincentDesiree M. Bates Ashley K. Tucker
Sara E. Ray Ron C. Estler
MALDI OverviewMALDI Overview•MALDI is a soft ionization technique that has revolutionized high-molecular weight mass spectrometry •Technique used to measure the molecular weights of a number of systems
•Proteins•Polysaccharides •Glyco-lipids•Synthetic Polymers
•Nobel Prize Awarded to Fenn and Tanaka in 2002 for the development of soft ionization techniques
http://www.magnet.fsu.edu/education/tutorials/tools/ionization_maldi.html
AdvantagesAdvantages Used for Disease Used for Disease
DiagnosisDiagnosis Able to Ionize Large Able to Ionize Large
moleculesmolecules Accurate / Rapid Accurate / Rapid
AnalysisAnalysis Fast TechniqueFast Technique
MALDI OverviewMALDI OverviewDisadvantagesDisadvantages
Lack of ReproducibilityLack of Reproducibility– Sample Hot SpotsSample Hot Spots
Lack of proper Matrix Lack of proper Matrix MoleculesMolecules
Poor Fundamental Poor Fundamental Understanding of the Understanding of the MechanismMechanism
Lack of Rational Lack of Rational DesignDesign
Cluster IonizationCluster Ionization– Ionization occurs after desorption Ionization occurs after desorption
from the matrix from the matrix – Proton transfer occurs in the gas-Proton transfer occurs in the gas-
phase or in small matrix clustersphase or in small matrix clusters
Proposed MechanismsProposed Mechanisms
PhotoionzationPhotoionzation– Multiple matrix molecule photon Multiple matrix molecule photon
absorptionabsorption– Energy transferred to the analyte in Energy transferred to the analyte in
the solid-phase or the gas-phasethe solid-phase or the gas-phase
Proposed MechanismsProposed Mechanisms
MethodsMethods Run a MD canonical Run a MD canonical
simulation (CHARMM) to simulation (CHARMM) to determine the general determine the general structure of the matrix structure of the matrix protein interactionsprotein interactions
Optimize the structures of Optimize the structures of potentially relevant potentially relevant matrix/analyte matrix/analyte conformations using conformations using electronic structure theoryelectronic structure theory
Study the energetics of the Study the energetics of the proton transfer reactions proton transfer reactions using intrinsic-reaction-using intrinsic-reaction-coordinate electronic coordinate electronic structure studies for a test structure studies for a test set of amino acid/benzoic set of amino acid/benzoic acid derivativesacid derivatives
Future ChallengesFuture Challenges Move beyond pure molecular mechanicsMove beyond pure molecular mechanics Investigate other possibilities for matrix Investigate other possibilities for matrix
moleculesmolecules Move beyond the gas phase for the MD Move beyond the gas phase for the MD
simulationssimulations Testing new matrix molecules for Testing new matrix molecules for
predictive recommendations to predictive recommendations to experimentalists experimentalists
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