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Lifetime distribution analysis were performed to study the influence of Leu configura­tion in position 5 on changes of the peptide chain of cyclic analogues of enkephalins con­taining a fluorescence donor and acceptor in different solvents. The configuration change of Leu5 in all the analogues of enkephalins studied which contain donor-acceptor pairs has no apparent influence on Trp lifetime distributions. In contrast, there is a significant solvent effect on the shape of lifetime distribution.
Continuing our studies on proctolin (Arg-Tyr-Leu-Pro-Thr) we performed the syn­thesis and biological evaluation of 52 analogues substituted in position 2, 3, 4, and 5 of the peptide chain. The peptides were bioassayed for cardiotropic activity in vitro on Tenebrio molitor and myotropic activity on foregut of Schistocerca gregaria. Twenty analogues retained 20-80% of proctolin activity.
Congo red and a group of structurally related dyes long used to stain amyloid proteins are known to associate in water solutions. The self-association of some dyes belonging to this group appears particularly strong. In water solutions their molecules are arranged in ribbon-like micellar forms with liquid crystalline properties. These compounds have recently been found to form complexeswith some native proteins in a non-standard way. Gaps formed by the local distribution of β-sheets in proteins probably represent the receptor sites for these dye ligands. They may result from higher structural instability in unfolding conditions, but also may appear as long range cooperative fluctuations generated by ligand binding. Immunoglobulins G were chosen as model binding proteins to check the mechanism of binding of these dyes. The sites of structural changes generated by antigen binding in antibodies, believed to act as a signal propagated to distant parts of the molecule, were assumed to be suitable sites for the complexation of liquid-crystalline dyes. This assumption was confirmed by proving that antibodies engaged in immune complexation really do bind these dyes; as expected, this binding affects their function by significantly enhancing antigen binding and simultaneously inhibiting C1q attachment. Binding of these supramolecular dyes by some other native proteins including serpins and their natural complexes was also shown. The strict dependence of the ligation properties on strong self-assembling and the particular arrangement of dye molecules indicate that supramolecularity is the feature that creates non-standard protein ligands, with potential uses in medicine and experimental science.
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Antinociceptive effect of MAS MT in rats

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MAS MT is a myotropic decapeptide isolated from Manduca sexta. This peptide exerts stimulatory effect on insects heart-beat frequency. The present study was undertaken in order to determine a probable antinociceptive effect in rats of native synthetic decapeptide, MAS MT-I and its two analogs, heptapeptides MAS MT-II and MAS MT-III. All these peptides were applied directly into the lateral brain ventricle (icv) at three doses: 10, 25 and 50 nmol. The analgesic (antinociceptive) effect was evaluated by a tail immersion test. It was found that two doses of MAS MT-I: 25 and 50 nmol induced significant antinociceptive effect, while MAS MT-II and MAS MT-III exert a less antinociceptive effect in comparison with native MAS MT-I. Prior icv administration of naloxone, an opioid antagonist weakly blocked MAS MT-I effect. We conclude that antinociceptive effect of MAS MT-I in rats is not mediated by central opioid system.
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