Results 251 to 260 of about 207,343 (281)

Strong, Low-Barrier Hydrogen Bonds May Be Available to Enzymes

Biochemistry, 2014
The debate over the possible role of strong, low-barrier hydrogen bonds in stabilizing reaction intermediates at enzyme active sites has taken place in the absence of an awareness of the upper limits to the strengths of low-barrier hydrogen bonds involving amino acid side chains. Hydrogen bonds exhibit their maximal strengths in isolation, i.e., in the
Jacob D, Graham, Allyson M, Buytendyk, Di, Wang, Kit H, Bowen, Kim D, Collins   +4 more
openaire   +2 more sources

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 ...
Masaki Tsujimura, Keisuke Saito, Hiroshi Ishikita   +2 more
openaire   +1 more source

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

Are Short, Low-Barrier Hydrogen Bonds Unusually Strong?

Accounts of Chemical Research, 2010
In a symmetric hydrogen bond (H-bond), the hydrogen atom is perfectly centered between the two donor atoms. The energy diagram for hydrogen motion is thus a single-well potential, rather than the double-well potential of a more typical H-bond, in which the hydrogen is covalently bonded to one atom and H-bonded to the other.
openaire   +2 more sources

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
Yoko Kato, Leticia M. Toledo, Julius Rebek   +2 more
openaire   +1 more source

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, Angels González-Lafont, José M Lluch   +2 more
exaly   +2 more sources

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
openaire   +2 more sources

Low-barrier hydrogen bonds:Abinitio and DFT investigation

Journal of Computational Chemistry, 1998
High-level ab initio and DFT molecular orbital calculations have been used to investigate the physical properties of a model low-barrier hydrogen bond (LBHB) system: formic acid–formate anion. In the gas phase, it is found that the hydrogen bond formed is extraordinarily short and strong [ca.
Ganesh A. Kumar, Yongping Pan, C. Jay Smallwood, Michael A. McAllister   +3 more
openaire   +1 more source

Low-Barrier Hydrogen Bond between Phosphate and the Amide Group in Phosphopeptide

Journal of the American Chemical Society, 2005
As 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, Yan-Mei, Li, Wei, Wei, Guo-Shi, Wu, Yu-Fen, Zhao, Kenji, Kanazawa, Tadashi, Nemoto, Hiroshi, Nakanishi   +7 more
openaire   +2 more sources

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
openaire   +1 more source