Binding Topologies of Amino Acid Binary Systems by Infrared Multiphoton Dissociation (IRMPD) Spectroscopy

Abstract

Studies of amino acids are essential because they are one of the building blocks of larger biomolecules, and it is crucial for us to understand how they interact with each other to fulfill all these various biological functions in our daily life. One interesting and noticeable fact from previous studies is that the amino acids found in proteins almost always possess only the left-handed configuration. When an enantiomer of a chiral molecule shows a stronger interaction with one enantiomer of another chiral molecule than with its mirror image, chirality recognition is observed. In the past few decades, gas phase rotational and vibrational spectroscopies have been used to investigate non-covalent interactions in chiral molecular aggregates and in particular homochiral and heterochiral molecular pairs. Among them, infrared multiphoton dissociation (IRMPD) spectroscopy is a powerful spectroscopic technique for its high detection sensitivity and its capability to access larger chiral molecular systems without the complications in solution, while providing structural information. The following chapters include detailed work using IRMPD spectroscopy to determine the conformational and energetic relationship of the proton bound homochiral and heterochiral serine-asparagine and valine-asparagine dimers, as well as whether chirality recognition could be observed between the binary systems of interest. How the non-covalent inter/intra-molecular interactions affect the preferred binary structures, in particular the role of a polar or a non-polar sidechain, is also investigated.