Matrix-Assisted Laser Desorption Ionization for Systems of Large Complexity Modeled by Molecular Dynamics

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Akos Vertes of George Washington University and Robert Johnson of the University of Virginia are supported by a grant from the Theoretical and Computational Chemistry Program to pursue molecular dynamics simulations of matrix-assisted laser desorption ionization. They will simulate ablation of small macromolecular guests from small molecule host matrices and water ice matrices. The simulations will employ realistic large-molecule systems with newly derived force fields, and small-molecule systems with more accurate anharmonic potentials. The effects of selected infrared excitation, charge states, excitation density, and external electric fields will be investigated.The most accurate spectroscopic methods depend on the subject molecules being in the gas phase. Large biomolecules are difficult-to-impossible to evaporate since they tend to decompose before reaching high temperatures. A recent experimental technique called matrix-assisted laser desorption ionization bypasses this problem by embedding large molecules into an easy-to-evaporate matrix that can be excited by pulsed laser radiation. This method provides unprecedented accuracy in the molecular mass determination of large proteins. Despite the advantages of this method, knowledge of the underlying processes is lagging. Improved understanding of the basic phenomena involved will help extend the capabilities of this technique to important new classes of biomolecules.