Monte Carlo Simulations of Ag2+and Ag2in Aqueous Solution

2002 ◽  
Vol 106 (46) ◽  
pp. 12022-12030 ◽  
Author(s):  
Vincent Dubois ◽  
Pierre Archirel
Keyword(s):  
Aqueous Solution ◽  
Monte Carlo ◽  
Monte Carlo Simulations

Molecular recognition XIV. Monte Carlo simulation of the hydration of the combining site of a Lectin

1994 ◽  
Vol 72 (2) ◽  
pp. 463-470 ◽  
Author(s):  
H. Beierbeck ◽  
L. T. J. Delbaere ◽  
M. Vandonselaar ◽  
R. U. Lemieux
Keyword(s):  
Aqueous Solution ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Driving Force ◽  
Water Structure ◽  
Intermolecular Forces ◽  
Water Molecules ◽  
Polar Regions ◽  
Amino Acid Residues ◽  
Time Requirements

Monte Carlo simulations of the hydration of the combining sites of the divalent lectin IV of Griffonia simplicifolia were carried out using the X-ray structure of the native lectin at 2.15 Å resolution. The regions of the combining sites are identical shallow polyamphiphilic cavities with a surface area of approximately 240 Å2 and an average depth of only about 2.2 Å. To reduce the CPU time requirements for Monte Carlo simulations of the hydration of the combining site of the native lectin, a fragment of the protein structure was examined that contained only 62 of the 243 amino acid residues and was present in both of the two subunits of the protein. This portion of the lectin, which encompassed the combining site and its immediate surroundings, was examined, employing 250 water molecules to near symmetrically cover an area of about 370 Å2 over and about the combining site with a density of 1 at 300 K. As was previously found in similar studies of the hydration of the Lewis b tetrasaccharide, the nonpolar regions are much less densely hydrated than the adjacent polar regions. This situation is considered to arise because of the hydrogen-bonding requirement for water molecules to bridge over nonpolar regions of varying dimensions. It is expected, therefore, that the association of complementary hydrophilic surfaces in aqueous solution must involve, in addition to the establishment of the usual intermolecular forces of attraction, a collapse of water structure over "flickering cavities" for return to bulk. This collapse can be expected to contribute to the driving force for association both through a decrease in enthalpy (higher density) and through an increase in entropy (greater disorder). This property of hydrated polyamphiphilic surfaces may contribute importantly to the driving force of all associations in aqueous solution since virtually all organic molecules are polyamphiphilic in character.

Monte Carlo Simulations of Lysozyme Self-Association in Aqueous Solution

2001 ◽  
Vol 105 (48) ◽  
pp. 12189-12195 ◽  
Author(s):  
Fredrik Carlsson ◽  
Martin Malmsten ◽  
Per Linse
Keyword(s):  
Aqueous Solution ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Self Association

Low-voltage EDS of magnesium ferrite Dendrites in a FEG-SEM

1996 ◽  
Vol 54 ◽  
pp. 478-479
Author(s):  
Matthew T. Johnson ◽  
Ian M. Anderson ◽  
Jim Bentley ◽  
C. Barry Carter
Keyword(s):  
Monte Carlo ◽  
Quantitative Analysis ◽  
Monte Carlo Simulations ◽  
Cross Section ◽  
Spatial Resolution ◽  
Low Voltage ◽  
Magnesium Ferrite ◽  
X Ray ◽  
Interaction Volume ◽  
Ferrite Spinel

Energy-dispersive X-ray spectrometry (EDS) performed at low (≤ 5 kV) accelerating voltages in the SEM has the potential for providing quantitative microanalytical information with a spatial resolution of ∼100 nm. In the present work, EDS analyses were performed on magnesium ferrite spinel [(MgxFe1−x)Fe2O4] dendrites embedded in a MgO matrix, as shown in Fig. 1. spatial resolution of X-ray microanalysis at conventional accelerating voltages is insufficient for the quantitative analysis of these dendrites, which have widths of the order of a few hundred nanometers, without deconvolution of contributions from the MgO matrix. However, Monte Carlo simulations indicate that the interaction volume for MgFe2O4 is ∼150 nm at 3 kV accelerating voltage and therefore sufficient to analyze the dendrites without matrix contributions.Single-crystal {001}-oriented MgO was reacted with hematite (Fe2O3) powder for 6 h at 1450°C in air and furnace cooled. The specimen was then cleaved to expose a clean cross-section suitable for microanalysis.

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