Intramolecular Hydrogen Bonds in Amino Acids.

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Amino acids, besides being the building blocks of peptides and proteins, are of special interest to structural chemistry. The reason of this special interest is the fact that amino acids form zwitterions H_3N^+-X-COO^- in the solid state and in polar media, but neutral molecules H_2N-X-COOH in the gas phase or in matrix isolation. Link: Zwitterion to neutral conversion, animation for gamma-aminobutyric acid.)

Amino acids form very stable crystals that, under atmospheric pressure, in most cases decompose before melting. Experimental studies of the neutral form therefore require sophisticated techniques. Quantum chemical calculations, in contrast, deal with isolated molecules in vacuo and require additional concepts to treat any effects of the molecular environment. Quantum chemical calculations are therefore an ideal tool for the study of neutral amino acids.

The following pages give selected results of an ab initio study of omega-amino acids (glycine, beta-alanine, gamma-aminobutyric acid, ...). Each page is devoted to a single amino acid and contains several illustrative pictures of relevant conformers. Although most of the information is contained in the text, so that a text-only browser is basically sufficient, these pictures will help in understanding. Therefore, if your browser can load pictures, you might want to turn that option on. The bottom of each page provides links for forward and backward browsing and, in the center entry, an interface to the literature data base of the Institute of Physical and Theoretical Chemistry. Activation of this interface produces an up-to-date list of publications and theses that relate to the specific compound.

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