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Hydrogen bond
About: Hydrogen bond is a research topic. Over the lifetime, 57701 publications have been published within this topic receiving 1306326 citations.
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TL;DR: Amino acid ionic liquids dissolved native amino acids, despite water-free conditions, and are soluble in various organic solvents, such as chloroform.
Abstract: We first succeeded in synthesizing ionic liquids from 20 natural amino acids. Amino acid ionic liquids dissolved native amino acids, despite water-free conditions. Furthermore, these ionic liquids are soluble in various organic solvents, such as chloroform. Effects of acidity, hydrogen bonding ability, and steric factors on the properties of these ionic liquids were analyzed as the function of side groups.
1,101 citations
TL;DR: In this article, the potential functions were developed for use in computer simulations of liquid alcohols and other molecules with hydroxyl groups, based on earlier work for liquid hydrocarbons and required introduction of few new parameters.
Abstract: Intermolecular potential functions have been developed for use in computer simulations of liquid alcohols and other molecules with hydroxyl groups. The functions are based on earlier work for liquid hydrocarbons and required introduction of few new parameters. Optimization of the parameters involved studids of hydrogen-bonded complexes and Monte Carlo simulations for liquid methanol. Further application then consisted of Monte Carlo simulations for liquid methanol, ethanol, 1-propanol, 2-propanol, and 2-methyl-2-propanol at 25 O C and 1 atm. Extensive thermodynamic and structural results are reported for the liquid alcohols and are compared with experimental data. The excellent accord between simulation and experiment is remarkable in view of the simple form and facile parametrization of the potential functions. The five liquid alcohols all feature winding hydrogen-bonded chains with averages of close to two hydrogen bonds per molecule. The hydrogen bonding is also found to have interesting effects on the torsional energy surfaces for molecules in the liquids. Most striking is a narrowing of the conformational energy wells for rotation about the C-0 bonds.
1,059 citations
1,051 citations
TL;DR: A mechanism for GTP hydrolysis involving mainly Gln61 and Glu63 as activating species for in‐line attack of water as well as a mechanism for rate enhancement by GAP is proposed.
Abstract: The crystal structure of the H-ras oncogene protein p21 complexed to the slowly hydrolysing GTP analogue GppNp has been determined at 1.35 A resolution. 211 water molecules have been built into the electron density. The structure has been refined to a final R-factor of 19.8% for all data between 6 A and 1.35 A. The binding sites of the nucleotide and the magnesium ion are revealed in high detail. For the stretch of amino acid residues 61-65, the temperature factors of backbone atoms are four times the average value of 16.1 A2 due to the multiple conformations. In one of these conformations, the side chain of Gln61 makes contact with a water molecule, which is perfectly placed to be the nucleophile attacking the gamma-phosphate of GTP. Based on this observation, we propose a mechanism for GTP hydrolysis involving mainly Gln61 and Glu63 as activating species for in-line attack of water. Nucleophilic displacement is facilitated by hydrogen bonds from residues Thr35, Gly60 and Lys16. A mechanism for rate enhancement by GAP is also proposed.
1,042 citations
1,018 citations