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Hydrogen bond

About: Hydrogen bond is a research topic. Over the lifetime, 57701 publications have been published within this topic receiving 1306326 citations.


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Journal ArticleDOI
24 Jun 1994-Science
TL;DR: Several examples of enzymatic reactions that appear to use this principle are presented, and a weak hydrogen bond in the enzyme-substrate complex in which the pKa's do not match can become a strong, low-barrier one if the p Ka's become matched in the transition state or enzyme-intermediate complex.
Abstract: Formation of a short (less than 2.5 angstroms), very strong, low-barrier hydrogen bond in the transition state, or in an enzyme-intermediate complex, can be an important contribution to enzymic catalysis. Formation of such a bond can supply 10 to 20 kilocalories per mole and thus facilitate difficult reactions such as enolization of carboxylate groups. Because low-barrier hydrogen bonds form only when the pKa's (negative logarithm of the acid constant) of the oxygens or nitrogens sharing the hydrogen are similar, a weak hydrogen bond in the enzyme-substrate complex in which the pKa's do not match can become a strong, low-barrier one if the pKa's become matched in the transition state or enzyme-intermediate complex. Several examples of enzymatic reactions that appear to use this principle are presented.

1,007 citations

Journal ArticleDOI

995 citations

Journal ArticleDOI
07 Oct 1994-Science
TL;DR: The structure of a protein triple helix has been determined by x-ray crystallographic studies of a collagen-like peptide containing a single substitution of the consensus sequence, which adopts a triple-helical structure that confirms the basic features determined from fiber diffraction studies on collagen.
Abstract: The structure of a protein triple helix has been determined at 1.9 angstrom resolution by x-ray crystallographic studies of a collagen-like peptide containing a single substitution of the consensus sequence. This peptide adopts a triple-helical structure that confirms the basic features determined from fiber diffraction studies on collagen: supercoiling of polyproline II helices and interchain hydrogen bonding that follows the model II of Rich and Crick. In addition, the structure provides new information concerning the nature of this protein fold. Each triple helix is surrounded by a cylinder of hydration, with an extensive hydrogen bonding network between water molecules and peptide acceptor groups. Hydroxyproline residues have a critical role in this water network. The interaxial spacing of triple helices in the crystal is similar to that in collagen fibrils, and the water networks linking adjacent triple helices in the crystal structure are likely to be present in connective tissues. The breaking of the repeating (X-Y-Gly)n pattern by a Gly-->Ala substitution results in a subtle alteration of the conformation, with a local untwisting of the triple helix. At the substitution site, direct interchain hydrogen bonds are replaced with interstitial water bridges between the peptide groups. Similar conformational changes may occur in Gly-->X mutated collagens responsible for the diseases osteogenesis imperfecta, chondrodysplasias, and Ehlers-Danlos syndrome IV.

994 citations

Journal ArticleDOI
TL;DR: In this paper, the authors derived the thermodynamic parameters of liquid water by means of a statistical thermodynamic treatment, based on the ''flickering cluster'' model proposed by Frank and Wen.
Abstract: The thermodynamic parameters of liquid water are derived by means of a statistical thermodynamic treatment, based on the ``flickering cluster'' model proposed by Frank and Wen. Various models proposed for the structure of liquid water are reviewed, and the advantages of the Frank—Wen model are pointed out. The hydrogen‐bonded ice‐like clusters of H2O molecules in equilibrium with non‐hydrogen‐bonded liquid are described quantitatively in terms of the molecular species participating in different numbers of hydrogen bonds in the clusters. Equations expressing the mole fractions of the various species in terms of the average cluster size are derived. The partition function derived for the description of liquid water is based on a distribution of the H2O molecules over five energy levels, corresponding to four, three, two, one, and no hydrogen bonds per molecule. The most probable values of the average cluster size, the mole fraction of non‐hydrogen‐bonded water, and the thermodynamic parameters are obtained ...

991 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20232,352
20224,647
20211,701
20201,599
20191,598
20181,668