Results 251 to 260 of about 84,757 (292)

The strength of a low-barrier hydrogen bond in water

Tetrahedron Letters, 2002
Abstract There are large differences between the acidity of the enol of the acyclic diketone, 2,4-pentanedione and those of two cyclic diketones, 1,3-cyclopentanedione and 1,3-cyclohexanedione. Computational studies have demonstrated that these differences are largely due to the strength of the internal low-barrier hydrogen bond (LBHB) in the enol of
James R Keeffe, Freeman M Wong
exaly   +2 more sources

Low-barrier hydrogen bonds in proteins

Crystallography Reviews, 2013
Hydrogen bonding interactions are one of the most important chemical interactions among materials, especially biological materials, which help confer specificity, which is crucial for their efficient functioning. Recently, low-barrier hydrogen bonds (LBHBs) have been proposed to play a critical role in enzyme catalysis.
Samarth Hegde, Amit Das, Ramakrishna V Hosur   +2 more
exaly   +2 more sources

A low-barrier hydrogen bond in the catalytic triad of serine proteases

Science, 1994
Spectroscopic properties of chymotrypsin and model compounds indicate that a low-barrier hydrogen bond participates in the mechanism of serine protease action. A low-barrier hydrogen bond between Nδ1 of His 57 and the β-carboxyl group of Asp 102 in chymotrypsin can facilitate the formation of
P A Frey, Perry A Frey
exaly   +3 more sources

Characterization of a low barrier hydrogen bond in the active site of chymotrypsin

Journal of Molecular Structure, 2002
Abstract The possibility of strong hydrogen bonding in aqueous solutions is supported by spectroscopic and chemical properties of proton sponges and internally strained dicarboxylic acid monoanions in aqueous and aqueous/acetone solutions. A species of low barrier hydrogen bond (LBHB) in aqueous solutions is the downfield proton in transition state ...
Perry A Frey
exaly   +2 more sources

Theoretical Study of the Low-Barrier Hydrogen Bond in the Hydrogen Maleate Anion in the Gas Phase. Comparison with Normal Hydrogen Bonds

Journal of the American Chemical Society, 1997
Relative strengths of normal and low-barrier hydrogen bonds (LBHBs) in the gas phase were analyzed by means of quantum-mechanical and thermodynamic calculations on the mesaconic/citraconic and several maleic/fumaric cis/trans isomerization equilibria. All geometries were fully optimized with correlation effects included via second-order Moller−Plesset ...
Mireia Garcia Viloca, JOSÉ M Lluch, Angels González-Lafont   +2 more
exaly   +2 more sources

Follow the Protons:  A Low-Barrier Hydrogen Bond Unifies the Mechanisms of the Aspartic Proteases

Accounts of Chemical Research, 2001
Seven proton transfers in five steps participate in a catalytic turnover of an aspartic protease. The Rosetta Stone for elucidating their role is a low-barrier hydrogen bond that holds the two aspartic carboxyls in a coplanar conformation. The proton of this bond shuttles between oxygens during chemical steps via hydrogen tunneling, unlike in previous ...
D B Northrop, Dexter B Northrop
exaly   +3 more sources

Low-Barrier Hydrogen Bonds and Enzymic Catalysis

Science, 1994
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 ...
W W, Cleland, M M, Kreevoy
openaire   +2 more sources

Hydrogen-Bond Networks: Strengths of Different Types of Hydrogen Bonds and An Alternative to the Low Barrier Hydrogen-Bond Proposal

Journal of the American Chemical Society, 2013
We report quantifying the strengths of different types of hydrogen bonds in hydrogen-bond networks (HBNs) via measurement of the adiabatic electron detachment energy of the conjugate base of a small covalent polyol model compound (i.e., (HOCH2CH2CH(OH)CH2)2CHOH) in the gas phase and the pKa of the corresponding acid in DMSO.
Alireza, Shokri, Yanping, Wang, George A, O'Doherty, Xue-Bin, Wang, Steven R, Kass   +4 more
openaire   +2 more sources

On the Possibility of Detecting Low Barrier Hydrogen Bonds with Kinetic Measurements

Journal of Chemical Information and Computer Sciences, 2003
Recent experimental evidence has pointed to the possible presence of a short, strong hydrogen bond in the enzyme-substrate transition states in some biochemical reactions. To date, most experimental measures of these short, strong hydrogen bonds have monitored their equilibrium properties. In this work we show that kinetic measurements can also be used
Nolan E. Dean, Jeffrey E. Miller, Christopher J. Halkides, Michael Messina   +3 more
openaire   +2 more sources