Central Part Of Structure Research Articles

Molecular designing of organic conductor based upon the model of polypyrrole

The electronic structure and properties of polypyrrole (p-Pyr) based substituting by the group of pyrazine (Pyz) and their model compounds were studied by the density functional theory (DFT) at the B3LYP level with 6-31G* basis set. The bond length, the topological analyses and nucleus-independent chemical shifts (NICS) were analyzed and correlated with the electronic properties. The bond length of all compounds is reduced with the increase in the degree of polymerization, and the band gap of these compounds is decreased. The change of NICS shows that the conjugation degree in central section of the polymeric axis is stronger than that in outer section, and the structure of central part was close to quinoid structure in polymers. The theoretical results suggest that the band gap of p-Pyz (polymer of Pyz) (0.37 eV) is much smaller than the band gap of polypyrrole (1.84 eV). The narrow band gap, large HOMO and LUMO bandwidths and small effective masses make p-Pyz have a remarkable elevation of the conductivity, so it may be considered as a very good candidate for conducting material.

Recognition of protein complexation based on hydrophobicity distribution.

The identification of the surface area able to generate the protein-protein complexation ligand and ion ligation is critical for the recognition of the biological function of particular proteins. The technique based on the analysis of the irregularity of hydrophobicity distribution is used as the criterion for the recognition of the interaction regions. Particularly, the exposure of hydrophobic residues on the surface of protein as well as the localization of the hydrophilic residues in the hydrophobic core is treated as potential area ready to interact with external molecules. The model based on the "fuzzy oil drop" approach treating the protein molecule as the drop of hydrophobicity concentrated in the central part of structure with the hydrophobicity close to zero on the surface according to 3-dimensional Gauss function. The comparison with the observed hydrophobicy in particular protein reveals some irregularities. These irregularities seem to represent the aim-oriented localization.