Titlebook: Hydrogen Bonding in Biological Structures; George A. Jeffrey,Wolfram Saenger Book 1991 Springer-Verlag Berlin Heidelberg 1991 DNA.Peptide.

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Metrical Aspects of Two-Center Hydrogen Bondsprimary intermolecular cohesive force between the carbohydrate molecules, water, and carboxylic acids. They occur extensively in the structures of cyclodextrins, polysaccharides, glycolipids, and glycoproteins. The O.H ··· O bonds are important in the ices, in hydrated crystal structures, and in the

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Metrical Aspects of Three- and Four-Center Hydrogen Bondsutron diffraction crystal structures, that the three-center bonds occur much more frequently than previously thought. Analyses of small molecule crystal structures indicate that an average of about one quarter of all the NH ⋯ O = C and OH ⋯ O hydrogen bonds are of the three-center type (Table 2.3).

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Intramolecular Hydrogen Bondso be formed, and when formed, they confer additional rotational stability to these conformations. They ultimately help to determine and to define the three-dimensional structures of the molecules, and are therefore involved in their functional aspects. These bonds are of major importance in the glob

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Weak Hydrogen-Bonding Interactions Formed by C-H Groups as Donors and Aromatic Rings as Acceptorslectronegative atoms as first neighbors in crystal structures. Unlike the stronger O-H · · · O or N-H · · · O bonds, the hydrogen bonds with C-H as donor will not have a major influence on molecular conformation. They occur when other packing forces and stereochemical constraints bring C-H bonds and

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Hydrogen Bonding in Carbohydratesnes and pyrimidines in the nucleic acids, with polypeptides in the glycoproteins and with lipids in the glycolipids. The simpler carbohydrates resemble water molecules in one important respect. Their primary hydrogen-bonding function comes from the hydroxyl group which can have both donor and accept

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Hydrogen Bonding in Amino Acids and Peptides: Predominance of Zwitterionss. The naturally occurring molecules are the L-enantiomers, shown in .; for chemical formulae see Fig. 19.1. D-amino acids can be synthesized and the individual L- or D-amino acids or the D,L-racemates can be crystallized. All the common amino acids have been studied by neutron or X-ray crystal stru

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Purines and Pyrimidinesnteract specifically with the enzymes involved in the metabolism of the nucleic acids and with regulatory proteins. Purines, pyrimidines, and their derivatives have been used most successfully in the investigations of biological processes and have found application in pharmacology [520, 521]. The sa

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Base Pairing in the Purine and Pyrimidine Crystal Structuresase the strength of hydrogen bonding due to .-cooperativity. This favors the formation of base-paired dimers and in some cases of trimers and tetramers. These can occur between the same bases (homo- or self-association) and between different bases (hetero-association).

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