We have determined the hydrogen-bond geometry in liquid water from 0 to 80 degrees C by combining measurements of the proton magnetic shielding tensor with ab initio density functional calculations. The resulting moments of the distributions of hydrogen-bond length and angle are direct measures of thermal disorder in the hydrogen-bond network. These moments, and the distribution functions that ...

molecular dynamic simulation is a powerful method that monitors all variations in the atomic level in explicit solvent. by this method we can calculate many chemical and biochemical properties of large scale biological systems. in this work all-atom molecular dynamics simulation of polyalanine (pa) was investigated in the presence of 0.224, 0.448, 0.673, 0.897 and 1.122 m of guanidinium chlorid...

            We report herein the synthesis of ¾ substituted benzene sulfonamides linked via phenyl ring to a benzothiazole moiety. The title compounds in the two series namely N-(4-(benzothiazole-2-yl) phenyl) 4- substituted benzene sulfonamides and N-(4-(benzothiazole-2-yl) phenyl) 3- substituted benzene sulfonamides were synthesized by condensing 2-(3/4-aminophenyl) benzothiazole with various...

There are 30026 symmetry-distinct ways to arrange 20 water molecules in a dodecahedral cage with nearly optimum hydrogen bond lengths and angles, analogous to the arrangements that give rise to the zero-point entropy in ice-Ih. The energy of hydrogen bond isomers in (H2O)20 , assumed to be similar in the past, differs by up to 70 kcal/mol. The isomers differ widely in their hydrogen bond length...

The Schiff base mol-ecule of the title compound, C(15)H(14)N(2)O(4)·H(2)O, adopts a trans configuration with respect to the C=N double bond; the Schiff base itself is almost planar (r.m.s. deviation for all non-H atoms = 0.040 Å). The amido N atom is the hydrogen-bond donor to the water mol-ecule, which is the hydrogen-bond donor to the hydr-oxy groups of two neighboring mol-ecules. One of the ...

Hydrogen bonds are an important contributor to free energies of biological macromolecules and macromolecular complexes, and hence an accurate description of these interactions is important for progress in biomolecular modeling. A simple description of the hydrogen bond is based on an electrostatic dipole-dipole interaction involving hydrogen-donor and acceptor-acceptor base dipoles, but the phy...

Hydrogen-bond (H-bond) dynamics in the air-water interface is studied by molecular dynamics simulations. The analysis reveals that the dynamics of breaking and forming hydrogen bonds in the air-water interface is faster than that in bulk water for the polarizable water models. This is in contrast to the results found on a protein surface. We show that the difference stems from more rapid transl...

Two polymorphs of (2-carboxyethyl)(phenyl)phosphinic acid, C(9)H(11)O(4)P, crystallize in the chiral P2(1)2(1)2(1) space group with similar unit-cell parameters. They feature an essentially similar hydrogen-bonding motif but differ slightly in their detailed geometric parameters. For both polymorphs, the unequivocal location of the hydroxy H atoms together with the expected differences in the P...

Crystals of the title compound, C(12)H(8)N(2)·C(7)H(8)O(2), were obtained during cocrystallization experiments of a compound with two hydrogen-bond donors (2-hydroxy-benzyl alcohol) with another compound containing two hydrogen-bond acceptors (phenanthroline). Unexpectedly, the two mol-ecules do not form dimers with two O-H⋯N hydrogen bonds connecting the two mol-ecules. However, one of the hyd...