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.

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%.

[Spatial structure of angiotensin in an aqueous solution].

The spatial structure of spin-labeled angiotensin in aqueous solution wa investigated with the combined use of NMR, fluorescence spectroscopy and energy calculation including Monte-Carlo techniques. The calculated mean values of molecular parameters were compared with the experimental ones. The calculated and experimental mean values were regarded as statistically indistinguishable when the corresponding mean values occurred within the 95% confidence limit.

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).

[Synthesis, biological activity and conformation of enkephalin analogs structurally related to kyotorphin].

[D-Arg2,Leu5]Enkephalin and two series of its N-terminal short-chain analogues with a free and modified C-terminal carboxylic group, viz. amides and ethyl esters of tri- and tetrapeptides, were synthesized in solution and by solid-phase method. Their analgesic activity, assayed by the "tail pinch" method following intracisternal and intravenous administration to mice, was compared with activity of enkephalins and morphine.

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).

Equilibrium of conformers in solution: spin-labelled angiotensin.

The number of structural parameters were determined for spin-labelled angiotensin in aqueous solution with the use of fluorescence spectroscopy and 1H NMR relaxation induced by the spin label. At the same time all measured parameters were estimated theoretically by means of energy calculations and Monte-Carlo techniques. The matching procedure for experimental and computational data allows one to suggest a dynamic equilibrium between conformers of the molecule in aqueous solution and to estimate the values of their weights.

[Conformation of the enkephalin cycloanalog Lys-Tyr-Gly-Gly-Phe-Leu-].

The spatial structure of an enkephaline cycloanalogue Lys-Tyr-Gly-Gly-Phe-Leu--has been investigated by means of energy calculations, fluorescence and CD-spectroscopy. Despite the high conformational mobility of the cycloanalogue, little resemblance exists between its and parent peptide's low-energy structures. Conformational factors for possible mechanisms of interaction between specific enkephalin receptors and cycloanalogue are discussed.