Results 161 to 170 of about 230,876 (232)

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
Y. Kato, A. Toledo, J. Rebek
semanticscholar   +3 more sources

The low barrier hydrogen bond (LBHB) proposal revisited: The case of the Asp ··· His pair in serine proteases

Proteins: Structure, Function, and Bioinformatics, 2004
Claudia Schütz, Arieh Warshel
openalex   +2 more sources

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

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
Kit H. Bowen, Di Wang, Jacob D. Graham, Kim D. Collins, Allyson M. Buytendyk   +4 more
openaire   +2 more sources

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.
Chin-Hui Yu, Timm Lankau
openaire   +2 more sources

The Deuterium Isotope Effect on the NMR Signal of the Low-Barrier Hydrogen Bond in a Transition- State Analog Complex of Chymotrypsin

Biochemical and Biophysical Research Communications - BBRC, 2000
Constance S. Cassidy, Jing Lin, Perry A. Frey   +2 more
openalex   +2 more sources

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
openaire   +2 more sources

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.
openaire   +3 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.
openaire   +3 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 ...
Keisuke Saito, Hiroshi Ishikita, Masaki Tsujimura   +2 more
openaire   +2 more sources

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
openaire   +3 more sources