Studies in hydrogen bonding: Association within small clusters of water, methanol, and ammonia molecules using Jorgensen's intermolecular pair potentials

1982 ◽  
Vol 3 (2) ◽  
pp. 219-226 ◽  
Author(s):  
George Brink ◽  
Leslie Glasser
Keyword(s):  
Hydrogen Bonding ◽  
Pair Potentials ◽  
Small Clusters

Hydrogen Bonding: From Small Clusters to Biopolymers

1999 ◽  
Vol 130 (8) ◽  
pp. 947-960 ◽  
Author(s):  
Peter Schuster ◽  
Peter Wolschann
Keyword(s):  
Hydrogen Bonding ◽  
Small Clusters

Hydrogen Bonding: From Small Clusters to Biopolymers

1999 ◽  
pp. 3-16 ◽  
Author(s):  
Peter Schuster ◽  
Peter Wolschann
Keyword(s):  
Hydrogen Bonding ◽  
Small Clusters

scholarly journals Monte Carlo Calculations of Effective Surface Tension for Small Clusters

1996 ◽  
Vol 49 (2) ◽  
pp. 425 ◽  
Author(s):  
Barbara N Hale
Keyword(s):  
Surface Tension ◽  
Monte Carlo ◽  
Free Energy ◽  
Water Clusters ◽  
Bulk Liquid ◽  
Effective Surface ◽  
Pair Potentials ◽  
Excess Surface ◽  
Metropolis Monte Carlo ◽  
Small Clusters

In this study we have calculated configurational Helmholtz free energy differences between n and n – 1 molecule water clusters and nand n – 1 atom argon clusters using classical effective atom-atom pair potentials and the Bennett–Metropolis Monte Carlo technique. When plotted versus n–1/ 3 the slope of the free energy differences yields an effective surface tension, σ. It is found that these slopes display a universal (material independent) property related to the excess surface entropy / κ per molecule (or atom), Ω. For most materials (in the bulk liquid state) the latter quantity is about 2. The results indicate that clusters as small as n = 10 display bulk surface free energy properties. The temperature dependence of the effective surface tension for the model water clusters is also investigated and is consistent with a simple scaled form, σ / κTρ2/3liquid ≈ Ω(Tc /T – 1), where Tc = 647 K and Ω = 1�9.

Computational study on small water clusters using a semiempirical valence bond approach

1999 ◽  
Vol 77 (3) ◽  
pp. 367-377 ◽  
Author(s):  
Youliang Wang ◽  
John R Gunn
Keyword(s):  
Hydrogen Bonding ◽  
Binding Energy ◽  
Water Clusters ◽  
Computational Study ◽  
Valence Bond ◽  
Energy Contribution ◽  
Stable Conformation ◽  
Small Water ◽  
Bonding Structure ◽  
Small Clusters

Small clusters of water (H2O)n, n = 3-8, are studied using a semiempirical valence bond approach to investigate the bonding energy contribution and hydrogen-bonding structure in the most stable conformation. The energy contribution was decomposed into electron pair-pair interactions and valence-bond energy for each water monomer. Our study shows that there is significant bonding difference between small clusters (n [Formula: see text] 5) of water and larger clusters (n > 5). In the larger clusters, there are structures containing tetravalent oxygen centers, which is impossible in the small clusters. The contribution to the binding energy from each H-bond varies from -4.7 kcal/mol to -7.3 kcal/mol in the water clusters considered here. The contribution of -5.9 kcal/mol per H-bond in the cubic octamer is comparable to the experimental value (-6.7 kcal/mol) of the binding energy in ice.Keywords: semi-empirical, valence bond, hydrogen bonding, water clusters.

The relationship of IGE receptor topography to signaling activity in RBL-2H3 mast cells

1991 ◽  
Vol 49 ◽  
pp. 236-237
Author(s):  
J.R. Pfeiffer ◽  
J.C. Seagrave ◽  
C. Wofsy ◽  
J.M. Oliver
Keyword(s):  
Mast Cells ◽  
Protein A ◽  
Scattered Electron ◽  
Ige Receptor ◽  
Receptor Complexes ◽  
Ige Binding ◽  
Electron Imaging ◽  
Small Clusters ◽  
Relationship Of ◽  
The Relationship

In RBL-2H3 rat leukemic mast cells, crosslinking IgE-receptor complexes with anti-IgE antibody leads to degranulation. Receptor crosslinking also stimulates the redistribution of receptors on the cell surface, a process that can be observed by labeling the anti-IgE with 15 nm protein A-gold particles as described in Stump et al. (1989), followed by back-scattered electron imaging (BEI) in the scanning electron microscope. We report that anti-IgE binding stimulates the redistribution of IgE-receptor complexes at 37“C from a dispersed topography (singlets and doublets; S/D) to distributions dominated sequentially by short chains, small clusters and large aggregates of crosslinked receptors. These patterns can be observed (Figure 1), quantified (Figure 2) and analyzed statistically. Cells incubated with 1 μg/ml anti-IgE, a concentration that stimulates maximum net secretion, redistribute receptors as far as chains and small clusters during a 15 min incubation period. At 3 and 10 μg/ml anti-IgE, net secretion is reduced and the majority of receptors redistribute rapidly into clusters and large aggregates.

Molecular architecture and functions of the neuronal cytoskeleton

1990 ◽  
Vol 48 (3) ◽  
pp. 2-3
Author(s):  
Nobutaka Hirokawa
Keyword(s):  
Major Elements ◽  
Molecular Structures ◽  
Organelle Transport ◽  
Molecular Architecture ◽  
Neuronal Morphogenesis ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
And Function ◽  
Small Clusters

In this symposium I will present our studies about the molecular architecture and function of the cytomatrix of the nerve cells. The nerve cell is a highly polarized cell composed of highly branched dendrites, cell body, and a single long axon along the direction of the impulse propagation. Each part of the neuron takes characteristic shapes for which the cytoskeleton provides the framework. The neuronal cytoskeletons play important roles on neuronal morphogenesis, organelle transport and the synaptic transmission. In the axon neurofilaments (NF) form dense arrays, while microtubules (MT) are arranged as small clusters among the NFs. On the other hand, MTs are distributed uniformly, whereas NFs tend to run solitarily or form small fascicles in the dendrites Quick freeze deep etch electron microscopy revealed various kinds of strands among MTs, NFs and membranous organelles (MO). These structures form major elements of the cytomatrix in the neuron. To investigate molecular nature and function of these filaments first we studied molecular structures of microtubule associated proteins (MAP1A, MAP1B, MAP2, MAP2C and tau), and microtubules reconstituted from MAPs and tubulin in vitro. These MAPs were all fibrous molecules with different length and formed arm like projections from the microtubule surface.

Hydrogen bonding in liquid methanol at ambient conditions and at high pressure

2000 ◽  
Vol 98 (3) ◽  
pp. 125-134 ◽  
Author(s):  
T. Weitkamp, J. Neuefeind, H. E. Fisch
Keyword(s):  
High Pressure ◽  
Hydrogen Bonding ◽  
Ambient Conditions
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