Conformational interpretation of intramolecular electron transfer in Met5-enkephalins between Tyr and Met(S:.Br) radical.

Mean distances between C beta atoms of redox centers and mean values of the exponentially distance dependent rate constants for intramolecular electron transfer, (k), in aqueous solution were calculated for Met5-enkephalin and its D-Ala2 analogue using the molecular mechanics and Monte Carlo techniques. The ratio of (k) values thus obtained proved similar to that determined experimentally for intramolecular electron transfer accompanying Met(S:.Br)----TyrO.

Conformational aspects of antiviral activity of deoxyguanosine acyclic analogues.

Conformational possibilities of a series of deoxyguanosine analogues possessing or lacking antiviral activity were evaluated using methods of the molecular mechanics. Comparison of the spatial structures of acyclic analogues with one another and with the spatial structures of deoxyguanosine demonstrates restricted conformational mobility for compounds devoid of activity. The level of sterically allowed superposition of functional groups from the acyclic moieties of analogues and the corresponding atomic centres of deoxyribose could serve as a criterion of activity.

Dynamic space structure of the Leu-enkephalin molecule in DMSO solution.

The dynamical space structure of the Leu-enkephalin molecule in DMSO solution was described combining the ROE measurements and Monte Carlo energy calculations. The statistical weights for possible Leu-enkephalin conformers were estimated by comparing the NMR-experimental parameters and the same parameters average over statistical samples of molecular structures obtained by Monte Carlo techniques for every low-energy conformer. The statistical weight estimations reveal that the Leu-enkephalin molecule in DMSO solution is apparently represented by a mixture of at least two peptide backbone conformers with the mean statistical weight values of 70% and 30%.

Combined use of spectroscopic and energy calculation methods for the determination of peptide conformation in solution.

This paper describes the combined use of energy calculations and spectroscopic data for the determination of peptide conformations in solution. The approach involves (i) experimental measurements of spectroscopic parameters for a molecule, (ii) calculation of these parameters for low-energy conformers previously determined with regard to local fluctuations in conformation and (iii) a random search for statistically weighted combinations of conformers which provide a good agreement between the calculated and experimental data. The above approach was used to study the conformation of a spin-labelled angiotensin molecule (SL-AT).

The space structure of a conformationally labile oligopeptide in solution: angiotensin.

The paper describes a new approach to the problem of space structure description for conformationally labile molecules existing in solution as a set of different conformers in dynamic equilibrium. In such a case the "average" model derived exclusively from physico-chemical data represents a virtual structure devoid of physical sense. The proposed approach involves the selection of statistical weights wi for molecular conformers in solution by combined use of spectroscopic data and energy calculations (including the Monte-Carlo technique).