Molecules, arranging

The first molecular dynamics simulations of a lipid bilayer which used an explicit representation of all the molecules was performed by van der Ploeg and Berendsen in 1982 [van dei Ploeg and Berendsen 1982]. Their simulation contained 32 decanoate molecules arranged in two layers of sixteen molecules each. Periodic boundary conditions were employed and a xmited atom force potential was used to model the interactions. The head groups were restrained using a harmonic potential of the form ... 

The three-dimensional structure of protein molecules can be experimentally determined by two different methods, x-ray crystallography and NMR. The interaction of x-rays with electrons in molecules arranged in a crystal is used to obtain an electron-density map of the molecule, which can be interpreted in terms of an atomic model. Recent technical advances, such as powerful computers including graphics work stations, electronic area detectors, and... 

Ice, seen floating on the water in the painting, has its water molecules arranged in an open hexagonal pattern. This is a result of hydrogen bonding. The large portion of open space in the structure explains why ice floats on water. 

Regions of high electron concentration—bonds to atoms and lone pairs attached to a central atom in a molecule— arrange themselves in such a way as to minimize mutual repulsions. 

Fig. 1. The structure of gas hydrates containing a hydrogen-bonded framework of 46 water molecules. Twenty molecules, arranged at the comers of a pentagonal dodecahedron, form a hydrogen-bonded complex about the comers of the unit cube, and another 20 form a similar complex, differently oriented, about the centre of the cube. In addition there are six hydrogen-bonded water molecules, one of which is shown in the bottom face of the cube. In the proposed structure for water additional water molecules, not forming hydrogen bonds, occupy the centres of the dodecahedra, and...

Salts of fatty acids are classic objects of LB technique. Being placed at the air/water interface, these molecules arrange themselves in such a way that its hydrophilic part (COOH) penetrates water due to its electrostatic interactions with water molecnles, which can be considered electric dipoles. The hydrophobic part (aliphatic chain) orients itself to air, because it cannot penetrate water for entropy reasons. Therefore, if a few molecnles of snch type were placed at the water surface, they would form a two-dimensional system at the air/water interface. A compression isotherm of the stearic acid monolayer is presented in Figure 1. This curve shows the dependence of surface pressure upon area per molecnle, obtained at constant temperature. Usually, this dependence is called a rr-A isotherm. 

Under normal conditions, sulfur forms yellow crystals. The ciystals consist of individual Sg molecules, with the eight sulfur atoms of each molecule arranged in a puckered ring. 

In the hexagonal ice crystal, each molecule is linked to four others. The molecules arrange themselves as stacks of hexagonal rings. 

Table I. Evolved Gases From 2 MeV He+ Irradiation of 0.9 nm Palladium Acetate Film. Molecules arranged in order of decreasing abundance within each group...

The use and reactions of glyoxal as a fixative have been reviewed extensively.3334 Glyoxal is the second smallest aldehyde, being like two formaldehyde molecules arranged back-to-back (Fig. 12.8, left). It too forms hydrates with water, the most common of which is 1,3-dioxolane (Fig. 12.8, right). 

The solvent species, H20, is a very polar molecule. The water molecules arrange themselves around the ions so that the slightly positive ends of the water molecules point toward the negative ions, and the slightly negative ends of the water molecules point toward the positive ions. 

Consider a monolayer of water molecules arranged in a square lattice with a lattice constant of 3 A. The dipole moment of a single molecule is 6.24 x 10 30 C m. (a) Calculate the potential drop across the monolayer if all dipole moments are parallel and perpendicular to the lattice plane, (b) If the potential drop across the layer is 0.1 V, what is the average angle of the dipole moment with the lattice plane ... 

It is safer in many instances to assume the solvated proton has the formula unit [H(H20)4]+, with four water molecules arranged tetrahedrally around a central proton, the proton being stabilized by a lone pair from each oxygen atom. 

The variable hardness in this work is the local hardness as given by the basic theory [2]. The electronic chemical potential in this work is a property if a given molecule (arrangement of nuclei) is also of the approximate wave function used to describe it. This does not represent an equilibrium system. The variation of the chemical potential is a consequence. 

When polymorphism occurs, the molecules arrange themselves in tv/o or more different v/ays in the crystal either they may be packed differently in the crystal lattice, or there may be differences in the orientation or the conformation of the molecules at the lattice site. These variations cause differences in X-ray diffraction patterns of the polymorphs and this technique is one of the main methods in detecting them. The polymorphs have different physical and chemical properties. 

Mesophase that has the molecules arranged in layers with a well-defined layer spacing or periodicity. 

A crystal is made up of repeating units called unit cells. Each unit cell in the crystal has the same number of atoms or molecules arranged in a pattern that repeats regularly in three-dimensions (Fig. 4.6). It is the regularity or periodicity that makes a crystal diffract X-rays, while it is the content of the unit cell that gives a crystal its unique diffraction pattern. Furthermore, the degree to which all unit cells and their content have the same orientation in a crystal is directly proportional to its diffraction resolution. 

The structure of these spherites is uncertain Bradford assumes that they consist of a regular crystalline growth formed by multiple twinning of minute crystals. Scherrer s examination of gold sols, however, has revealed the fact that the crystal interference lines are well developed when the particle contains as few as eighty molecules arranged in the cube lattice, a spherite of OTju. diameter would probably show crystalline properties even if excessive twinning has taken place. 

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