Results 261 to 270 of about 84,757 (292)

Turning Low Barrier Hydrogen Bonds on and Off

Journal of the Chinese Chemical Society, 2010
AbstractThe hydrogen bond in the [HDihH‐Fda]+ ion (HDih: 4,5‐dihydro‐1H‐imidazole, Fda: 1‐fluoro‐N,N‐dimethylmethaneamine) can be an ordinary single well hydrogen bond (HB) or a low barrier hydrogen bond (LBHB) depending on the orientation of the CH2F group in the Fda molecule.
Timm Lankau, Chin‐Hui Yu
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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 ...
Masaki Tsujimura, Keisuke Saito, Hiroshi Ishikita   +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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Low-barrier hydrogen bond plays key role in active photosystem II — A new model for photosynthetic water oxidation [PDF]

Biochimica Et Biophysica Acta - Bioenergetics, 2007
The function and mechanism of TyrZ in active photosystem II (PSII) is one of the long-standing issues in the study of photosynthetic water oxidation. Based on recent investigations on active PSII and theoretical studies, a new model is proposed, in which
Chunxi Zhang
exaly   +2 more sources

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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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.
Michael T, Ruggiero, Timothy M, Korter
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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
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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.
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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
Yoko Kato, Leticia M. Toledo, Julius Rebek   +2 more
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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
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