Results 261 to 270 of about 196,444 (313)

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
Freeman M. Wong, Weiming Wu, James R. Keeffe   +2 more
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Low Barrier Hydrogen Bonds

Science, 1995
Proteins contain mainly weak, conventional hydrogen bonds; however, a few enzymes have low barrier hydrogen bonds (LBHBs) in transition state analog complexes. Hydrogen bonds display variations in physicochemical properties including length, spectroscopic characteristics, and strength.
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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.
George A. O'Doherty, Yanping Wang, Steven R. Kass, Alireza Shokri, Xue-Bin Wang, Xue-Bin Wang   +5 more
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Low-Barrier Hydrogen Bonds and Enzymatic Catalysis

Archives of Biochemistry and Biophysics, 2000
Short, strong (low barrier) hydrogen bonds occur when the pK values of the atoms sharing the proton are similar. The overall distance is 2.5 A or less, the deuterium fractionation factor is less than 0.5, the proton NMR chemical shift can approach 20 ppm, and deuterium or tritium substitution causes an up-field change in the chemical shift.
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Energetics of a Low Barrier Hydrogen Bond in Nonpolar Solvents

Journal of the American Chemical Society, 1996
A measure of the strength of a low barrier hydrogen bond (LBHB) in apolar organic media was obtained using synthetic molecules derived from Kemp's triacid. The structures feature unusually rigid conformations that enforce intramolecular hydrogen bonds in a dicarboxylic acid, its corresponding acid-amide and their respective conjugate bases. Analysis of
Julius Rebek, and Leticia M. Toledo, Yoko Kato   +2 more
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Absorption Wavelength Along Chromophore Low-Barrier Hydrogen Bonds

SSRN Electronic Journal, 2021
In low-barrier hydrogen bonds (H-bonds), the pKa values for the H-bond donor and acceptor moieties are nearly equal, whereas the redox potential values depend on the H+ position. Spectroscopic details of low-barrier H-bonds remain unclear. Here, we report the absorption wavelength along low-barrier H-bonds in protein environments, using a quantum ...
Keisuke Saito, Hiroshi Ishikita, Masaki Tsujimura   +2 more
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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
Michael Messina, Jeffrey E. Miller, Christopher J. Halkides, Nolan E. Dean   +3 more
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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
Perry A. Frey, John B. Tobin, Sean A. Whitt   +2 more
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The crucial role of water in shaping low-barrier hydrogen bonds

Physical Chemistry Chemical Physics, 2016
Low-barrier hydrogen bonds (LBHBs) are key components in a range of chemical processes, often appearing in metal-mediated catalytic applications.
Timothy M. Korter, Michael T. Ruggiero
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Evidence of a Low-Barrier Hydrogen Bond in the Tryptophan Synthase Catalytic Mechanism

Biochemistry, 1996
In the absence of other substrates, L-Ser reacts rapidly with the tryptophan synthase alpha 2 beta 2 bienzyme from Salmonella typhimurium at pH 7.8 and 25 degrees C to give an equilibrating mixture of species dominated by comparable amounts of the L-Ser external aldimine Schiff base, E(Aex1), and the alpha-aminoacrylate Schiff base, E(A-A).
Michael F. Dunn, Catherine A. Leja, Oscar Hur   +2 more
openaire   +3 more sources