Results 181 to 190 of about 240,874 (239)

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).
O, Hur, C, Leja, M F, Dunn
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Low barrier hydrogen bonds in sterically modified Schiff bases

Journal of the Chemical Society, Perkin Transactions 2, 2002
Five derivatives of an ortho-hydroxy Schiff base (2-(N-alkyl-α-iminoethyl)phenols) with very short intramolecular hydrogen bonds (dO(H)⋯N ≤ 2.500 A) were synthesised. The crystal structures were determined. The steric repulsion of the substituted methyl group results in an unusual strengthening of the hydrogen bonds, decreasing the barrier for the ...
Aleksander Filarowski, Aleksander Koll, Tadeusz Glowiak   +2 more
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Low barrier hydrogen bonds within salicylate mono-anions

Tetrahedron, 2001
Abstract Progressive incorporation of electron-withdrawing substituents into the aromatic ring of salicylic acid selectively acidifies the ArOH group, until the intrinsic pKa values of the ArOH and ArCO2H groups become matched, as in the case of 3-chloro-5-nitrosalicylic acid.
William L. Mock, Layne A. Morsch
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ChemInform Abstract: Low‐Barrier Hydrogen Bonds and Enzymic Catalysis.

ChemInform, 1994
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
W. W. CLELAND, M. M. KREEVOY
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A Low-Barrier Hydrogen Bond in Subtilisin:  ¹H and ¹⁵N NMR Studies with Peptidyl Trifluoromethyl Ketones

Biochemistry, 1996
Christopher J. Halkides, Yong Wu, Christopher J L Murray   +2 more
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The low-barrier hydrogen bond in enzymic catalysis

2010
Publisher 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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Are There Really Low-Barrier Hydrogen Bonds in Proteins? The Case of Photoactive Yellow Protein

Journal of the American Chemical Society, 2014
For a long time, low-barrier hydrogen bonds (LBHBs) have been proposed to exist in many enzymes and to play an important role in their catalytic function, but the proof of their existence has been elusive. The transient formation of an LBHB in a protein system has been detected for the first time using neutron diffraction techniques on a photoactive ...
Marc, Nadal-Ferret, Ricard, Gelabert, Miquel, Moreno, José M, Lluch   +3 more
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Spectral Signatures of Proton-Transfer Dynamics at the Cusp of Low-Barrier Hydrogen Bonding

The Journal of Physical Chemistry Letters, 2018
Despite their importance in diverse chemical and biochemical processes, low-barrier hydrogen bonds remain elusive targets to classify and interpret spectroscopically. Here the correlated nature of hydrogen bonding and proton transfer in the low-barrier regime has been probed for the ground and excited electronic states of 6-hydroxy-2-formylfulvene by ...
Zachary N. Vealey, Lidor Foguel, Patrick H. Vaccaro   +2 more
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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 ...
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Hydrogen bonding in complexes of carboxylic acids with 1-alkylimidazoles: steric and isotopic effects on low barrier hydrogen bonding

Journal of the Chemical Society, Perkin Transactions 2, 1999
The nature of hydrogen bonding within intermolecular complexes of carboxylic acids and 1-methylimidazole (1-MeIm), 1-n-butylimidazole (1-BuIm), and 1-tert-butylimidazole (1-t-BuIm) in chloroform was characterized by Fourier transform infrared spectroscopy. Earlier spectroscopic studies indicated that carboxylic acid–1-MeIm complexes are of three types:
Constance S. Cassidy, Laurie A. Reinhardt, W. Wallace Cleland, Perry A. Frey   +3 more
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