Spatial Structure of the Acth-(6-9)-PGP Molecule

The spatial structure of ACTH-(6-9)-PGP molecule has been investigated using theoretical conformational analysis method. Amino acid sequence of the N-terminal pentapeptide fragment of His-Phe-Arg-Trp-Pro of this molecule conforms to the fragment 6-9 of ACTH hormone. Calculations of conformational states of this molecule are carried out regarding nonvalent, electrostatic and torsional interactions and the energy of hydrogen bonds. The spatial structure of the His-Phe-Arg-Trp-Pro-Gly-Pro molecule was estimated on the low–energy conformations of the N-terminal tetrapeptide fragment His-Phe-Arg-Trp and C-terminal tripeptide fragment Pro-Gly-Pro of this molecule. It is shown that the spatial structure of heptapeptide molecule can be presented by 11 low-energy forms of the main chain. The low–energy conformations of this molecule, the values of dihedral angles of the backbone and side chains of the amino acid residues were founded and the energies of intra- and inter-residual interactions were determined.

Qualitative Analysis of Clustering in Aqueous Alcohol Solutions

The specific features of clustering in the aqueous solutions of monohydric alcohols with concentrations higher than that at the peculiar point are discussed. Clustering is a result of the formation of hydrogen bonds between water and alcohol molecules, the energy of which some-what exceeds the energy of hydrogen bonds in the water-water and alcohol-alcohol molecular pairs. Elementary clusters are assumed to be formed, whose composition is fixed at the solution concentrations lower than that at the peculiar point and changes according to a certain law at higher concentrations. The solution clustering degree was determined as a function of the solution concentration and the temperature.

Структура и колебательные свойства гидратов оксианионных кристаллов из первых принципов

Structural parameters and IR spectra of hydrates of lithium and sodium perchlorates, calcium sulfate hydrate (gypsum), and lithium nitrate hydrate are calculated ab initio using the density functional theory. The bond lengths in the water molecules are established as functions of length and energy of hydrogen bonds. The relationship between lengths of intra-anionic and hydrogen bonds is considered. The splitting of intramolecular vibrations of water is highlighted. The stretching vibration frequency of water is determined as a function of length and energy of hydrogen bonds. The combined (mixed) vibrations of anions and molecules of water with frequencies below 1400 cm^–1 are feasible as well.

A Thermodynamic Study of Methane Hydrates Formation In Glass Beads

Natural gas hydrates are non-stoichiometry compounds, in which the molecules of gas are trapped in crystalline cells consisting of water molecules retained by energy of hydrogen bonds. The experiments of Methane hydrate formation are performed at constant temperature in a reactor filled with various sizes of glass beads and water. Methane gas was fed into the reactor at various initial pressures. Equilibrium condition was reached when the system pressure did not change. The experimental results showed that the size of the glass beads gave very small effect on the equilibrium pressure of methane hydrate formation, so the effect could be neglected. In this study, the equation of Langmuir constant was Ci,CH4=(1/RT)exp[A+(B/T)] with the values of A and B for small cages were 6.8465 and 18.0342. The values of A and B for large cages were 7.7598 and 18.0361