Hydrogen bond

About: Hydrogen bond is a research topic. Over the lifetime, 57701 publications have been published within this topic receiving 1306326 citations.

Molecular Dynamics Study of the Structure and Dynamics of the Hydration Shell of Alkaline and Alkaline-Earth Metal Cations

Abstract: Molecular dynamics simulations of hydrated alkaline and alkaline-earth metal cations at room temperature (T = 300 K) were carried out using the CHARMM22 force field. Dynamic and static properties of systems containing one ion and 123 or 525 water molecules were investigated by analysis of trajectories of 1 ns duration and compared to experimental and theoretical results. In addition, the size and the direction of the elementary motions of both the ions and the water molecules were investigated on the scale of the integration time step of 1 fs. Comparison between systems of different size revealed that for the larger system the diffusion coefficient and the number of hydrogen bonds were increased. Radial pair distribution functions and coordination numbers are in good agreement with X-ray and neutron scattering data. The diffusion coefficient D of bulk TIP3P water in a system with 528 water molecules was by one-fourth higher than the experimental value. Minor differences of approximately 10% between experi...

C‒H‒O Hydrogen Bonding in Crystals

Abstract: An overview is given on C–H···O hydrogen bonding in the solid state. Following a short survey of the early literature, the general properties of C–H···O bonding are discussed. The structural characteristics and some physical consequences of C–H···O bonds are described. A number of special systems are discussed in greater detail; these include water acceptors, inclusion complexes, and some biological structures.

Quantitative classification of covalent and noncovalent H-bonds.

Abstract: The covalent nature of interactions within various hydrogen bonded molecular aggregates has been characterized by the two entirely different computational methods: Bader analysis of the electron density and variation-perturbation partitioning of the intermolecular interaction energy. Analysis of 34 complexes representing different types of hydrogen bonds indicates that the proton-acceptor distance ∼1.8 A and the ratio of delocalization and electrostatic terms ∼0.45 constitutes approximately a borderline between covalent and noncovalent hydrogen bonds. The latter ratio could be used to characterize quantitatively the degree of the covalent nature of transition state interactions with active site residues, a quantity essential for an enzyme catalytic activity.

Studies on the Reversible Aggregation of Cysteine-Capped Colloidal Silver Particles Interconnected via Hydrogen Bonds

Abstract: The surface modification of aqueous silver colloidal particles with the amino acid cysteine and the cross-linking of the colloidal particles in solution is described. Capping of the silver particles with cysteine is accomplished by a thiolate bond between the amino acid and the nanoparticle surface. The silver colloidal particles are stabilized electrostatically by ionizing the carboxylic acid groups of cysteine. Aging of the cysteine-capped colloidal solution leads to aggregation of the particles via hydrogen bond formation between amino acid molecules located on neighboring silver particles. The aggregation is reversible upon heating the solution above 60 °C. The rate of cross-linking of the silver particles via hydrogen bond formation may be accelerated by screening the repulsive electrostatic interactions between the particles using salt. The process of aggregation and heat-induced dispersion of the particles has been studied by UV−vis spectroscopy, laser light scattering, and transmission electron mi...