Additional Hydrogen Bond (additional + hydrogen_bond)

Distribution by Scientific Domains

Selected Abstracts

Herringbone array of hydrogen-bonded ribbons in 2-ethoxybenzamide from high-resolution X-ray powder diffraction

Silvina Pagola
In 2-ethoxybenzamide, C9H11NO2, the amide substituents are linked into centrosymmetric head-to-head hydrogen-bonded dimers. Additional hydrogen bonds between adjacent dimers give rise to ribbon-like packing motifs, which extend along the c axis and possess a third dimension caused by twisting of the 2-ethoxyphenyl substituent with respect to the hydrogen-bonded amide groups. The ribbons are arranged in a T-shaped herringbone pattern and cohesion between them is achieved by van der Waals forces. [source]

X-ray crystallographic analysis of the complexes of enoyl acyl carrier protein reductase of Plasmodium falciparum with triclosan variants to elucidate the importance of different functional groups in enzyme inhibition

IUBMB LIFE, Issue 6 2010
Koustav Maity
Abstract Triclosan, a well-known inhibitor of Enoyl Acyl Carrier Protein Reductase (ENR) from several pathogenic organisms, is a promising lead compound to design effective drugs. We have solved the X-ray crystal structures of Plasmodium falciparum ENR in complex with triclosan variants having different substituted and unsubstituted groups at different key functional locations. The structures revealed that 4 and 2, substituted compounds have more interactions with the protein, cofactor, and solvents when compared with triclosan. New water molecules were found to interact with some of these inhibitors. Substitution at the 2, position of triclosan caused the relocation of a conserved water molecule, leading to an additional hydrogen bond with the inhibitor. This observation can help in conserved water-based inhibitor design. 2, and 4, unsubstituted compounds showed a movement away from the hydrophobic pocket to compensate for the interactions made by the halogen groups of triclosan. This compound also makes additional interactions with the protein and cofactor which compensate for the lost interactions due to the unsubstitution at 2, and 4,. In cell culture, this inhibitor shows less potency, which indicates that the chlorines at 2, and 4, positions increase the ability of the inhibitor to cross multilayered membranes. This knowledge helps us to modify the different functional groups of triclosan to get more potent inhibitors. 2010 IUBMB IUBMB Life, 467,476, 2010 [source]

Thermal Recovery of Iodopsin from Photobleaching Intermediates,

Yasushi Imamoto
The chloride effect on the photobleaching process of iodopsin, a chicken red-sensitive cone visual pigment, was studied in detail by time-resolved low-temperature spectroscopy at ,40C to ,10C. Decay-associated difference spectra obtained by kinetic analysis using the singular value decomposition method were composed of spectra of BL-iodopsin, lumiiodopsin, metaiodopsin I, metaiodopsin II and metaiodopsin III, essentially identical to those at room temperature. In each conversion step however, iodopsin was partially regenerated, which is not observed in the bleaching process for other visual pigments or iodopsin at room temperature. Moreover, iodopsin was slowly regenerated from the bleached species. The reverse reactions were completely suppressed by substitution of lyotropic NO3, for Cl,, suggesting that Cl, binding to iodopsin interferes with light-induced cis,trans isomerization of the chromophore. It is likely that the water molecule hydrating Cl, forms the additional hydrogen bond(s), by which the protein conformational change necessary to release this steric hindrance becomes enthalpic. As progress of the bleaching process is a consequence of protein conformational change, it is suppressed at low temperatures, resulting in thermal back-isomerization. [source]

Two- and Three-Dimensional Hydrogen-Bonded Networks Built from 1,3,5-[(HO)2(O)P]3C6H3 and 4-(Dimethylamino)pyridine

Michael Mehring
Abstract Crystallisation of 3,5-bis(phosphonophenyl)phosphonic acid, 1,3,5-[(HO)2(O)P]3C6H3, from MeOH/H2O in the presence of 4-(dimethylamino)pyridine, 4-(Me2N)C5H4N, gave [1-{(HO)2(O)P}-3,5-{(HO)(O)2P}2C6H3]2,[{4-(Me2N)C5H4NH}+]2 (2) and [1,3-{(HO)2(O)P}2 -5-{(HO)(O)2P}C6H3],[4-(Me2N)C5H4NH]+ (3). Single-crystal X-ray diffraction analyses revealed a two- and a three-dimensional hydrogen-bonded network for compounds 2 and 3, respectively. Compound 2 is composed of layers which are formed by hydrogen-bonded motifs of the type R2,2(8) and R4,4(16). These motifs are connected within the layer by additional hydrogen bonds and the benzene spacer. The cation [4-(Me2N)C5H4NH]+ is located between the layers and determines the interlayer separation of approximately 6.5 . In compound 3 a layered network of the hydrogen-bonded building units R2,3(10) was observed. These units are interconnected by four additional hydrogen bonds within the network. The benzene spacer links the adjacent layers to give a three-dimensional structure. Within this network, channels with internal dimensions of ca. 8.5 11.3 2 which are occupied by the [4-(Me2N)C5H4NH]+ cations were observed. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]