Results 271 to 280 of about 202,648 (320)
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The strength of a low-barrier hydrogen bond in water
Tetrahedron Letters, 2002Abstract 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 +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, 2003Recent 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 +3 more
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Low-Barrier Hydrogen Bond between Phosphate and the Amide Group in Phosphopeptide
Journal of the American Chemical Society, 2005As the conversion between the monoionic (1) and diionic (2) form of the phosphate occurs, the phosphorylated peptides or proteins can not only cause the formation of a hydrogen bond between the phosphate group and the amide group but also change the strength of the hydrogen bond to form low-barrier hydrogen bonds (LBHBs). This reversible protonation of
Jin-Tang, Du +7 more
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A Low-Barrier Hydrogen Bond in the Catalytic Triad of Serine Proteases
Science, 1994Spectroscopic 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, S A, Whitt, J B, Tobin
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The low-barrier hydrogen bond in enzymic catalysis
2010Publisher Summary This chapter describes the various aspects of the low-barrier hydrogen bond in enzymic catalysis. Hydrogen bonds come in a continuum of bond lengths and strengths. The first examples of enzymatic reactions where low-barrier hydrogen bonds played a role involved enolization of the substrate to change the p K of a key group in the ...
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Evidence of a Low-Barrier Hydrogen Bond in the Tryptophan Synthase Catalytic Mechanism
Biochemistry, 1996In 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).
O, Hur, C, Leja, M F, Dunn
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Transient low-barrier hydrogen bond in the photoactive state of green fluorescent protein
Physical Chemistry Chemical Physics, 2015A transient low-barrier hydrogen bond has been found directly after photoexcitation using quantum dynamics to study the excited-state process in GFP.
Marc Nadal-Ferret +3 more
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X-Ray Photoelectron Spectroscopy of Porphycenes: Charge Asymmetry Across Low-Barrier Hydrogen Bonds
Angewandte Chemie, 2001It is ironic that although it is typically a technique that "sees" all elements other than hydrogen atoms, X-ray photoelectron spectroscopy (XPS) acts as a sensitive probe of low-barrier hydrogen bonds, as seen in a study of free-base tetrapyrroles.
Abhik, Ghosh +3 more
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Unraveling Low‐Barrier Hydrogen Bonds in Complex Systems with a Simple Quantum Topological Criterion
Chemistry – A European Journal, 2011The importance of low-barrier hydrogen bonds (LBHBs) in enzyme catalysis has remained a controversial topic. LBHBs are defined as protons that are delocalized between two heavy atoms. Since the 1990s LBHBs have been proposed to play a crucial role in several enzyme-catalytic pathways by stabilizing transition states or reaction intermediates.
Chaudret, Robin +3 more
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Low-Barrier Hydrogen Bond in the Catalytic Triad of Serine Enzymes
1998Acetylcholinesterase (AChE) and chymotrypsin are serine enzymes whose catalytic mechanism involves a nucleophilic attack (serine) and a general acid-base moiety (histidine). The incipient imidiazolium which is formed as a result of the nucleophilic attack by serine is stabilized by the negatively charged carboxylate (Glu or Asp).
Rohit Medhekar +4 more
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