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Keywords:

anharmonic vibrational spectroscopy, isolation ft-ir, aqueous-solution, ab-initio, water complex, bonded complexes, ar matrices, conformers, alanine, potentials, Science & Technology, Physical Sciences, Chemistry, Physical, Physics, Atomic, Molecular & Chemical, Chemistry, Physics, ANHARMONIC VIBRATIONAL SPECTROSCOPY, ISOLATION FT-IR, AB-INITIO, BONDED COMPLEXES, WATER COMPLEX, CONFORMERS, AR, MOLECULES, ALANINE, MODEL, Amino Acid Transport Systems, Neutral, Binding Sites, Computer Simulation, Glycine, Models, Chemical, Models, Molecular, Molecular Conformation, Protein Binding, Spectroscopy, Fourier Transform Infrared, Static Electricity, Water, 02 Physical Sciences, 03 Chemical Sciences, 09 Engineering, Chemical Physics, 34 Chemical sciences, 40 Engineering, 51 Physical sciences

Abstract:

The H-bond interaction between glycine and H2O has been studied by a combined theoretical (DFT(B3LYP)/6-31++G**) and experimental (matrix-isolation FT-IR) methodology. The 1:1 and 1:2 complexes of the most stable conformation (I) of glycine appear to be neutral complexes which have been vibrationally characterized in detail. The higher stoichiometry complexes (glycine).(H2O)(n) with n larger than 3 are demonstrated to be zwitterionic H-bonded complexes. A set of characteristic IR absorption bands for this zwitterionic structure has been observed in low-temperature Ar matrices. This would be the first experimental IR evidence for proton transfer occurring between the NH2 and COOH groups of amino acids by a H-bonded water molecular channel in isolated conditions. (C) 2004 American Institute of Physics.