The importance of six theoretically calculated molecular parameters in the antigibberellin (retardant) activity of quaternary ammonium salts is studied using regression analysis. A bioassay system based on cell culture of fungus Gibberella fujikuroi is used to determine the activity. In the case of N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium chloride (choline) and N,N,N-triethyl-N-(2-hydroxyethyl)ammonium chloride (N,N,N-triethylcholine) derivatives with linear structure, the polarizability, proton acceptor activity, and lipophilicity of these compounds exert the largest effect on the antigibberellin activity. The antigibberellin activity of more sterically hindered N,N-dialkylpiperidinium salts was mainly defined by the steric parameter, while the polarizability, proton acceptor activity, and (through them) lipophilicity exert a lesser effect. Other parameters are of minor importance for the three groups of compounds studied. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 6; see also http://www.maik.ru.

Gibberella↗

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Modeling the open and closed forms of GABAA receptor: analysis of ligand-receptor interactions for the GABA-binding site.

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Amino Acid Sequence↗

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[Computer-aided prediction of the mutagenic activity substituted polycyclic compounds].

The relationship between mutagenic activity and chemical structure was studied for 54 polycyclic compounds using two approaches: multiple linear regression analysis and artificial neural networks. Structural fragments, quantum chemical indices, and hydrophobicity (octanol-water partition coefficient) were used as descriptors (properties of the molecules introduced in the model). Both linear regression equations and nonlinear relationships obtained with the help of a neural network were shown to accurately predict mutagenic activity for the compounds structurally similar to those in the training sample. The introduction of experimentally selected descriptors is substantiated to verify the proposed mechanism of related compounds mutagenic activity.

Heterocyclic Compounds, 3-Ring↗

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[Effect of mineralocorticoid analogs on Na(+),K(+)-dependent ATPase].

The effect of 42 steroids of the 20-ketopregnane series with heterocycles fused in positions 16 alpha and 17 alpha on the activity of Na+,K(+)-activated ATPase from pig kidney was studied. It was shown that the studied compounds could be divided into two groups. The compounds from the first group stimulate the ATPase at low concentrations (1 x 10(-8)-1 x 10(-7) M) and inhibit it at high concentrations (1 x 10(-4) M). The second group of compounds stimulated the sodium pump at either concentration. This is explained by the cooperative action of the ATPase tetramer: after the reaction of its first binding site with the ligand, the tetramer changes the conformation and specificity of its other binding sites. Computer analysis of this series of compounds was carried out and a mathematical model of the dependence of their activities on the structure of their substituents was obtained with a high correlation coefficient and a satisfactory predictive power. This confirmed the structural similarity of the studied compounds with respect to their interaction with the ATPase binding sites. The method of descriptor analysis that was applied in this study is a new variant of approximation; it is based on the use of symbol variables as descriptors.

Algorithms↗