[Structure-functional studies of polymyxins. (1)-NMR analysis of polymyxin B and M conformation]. / Strukturno-funktsional'nye issledovaniia polimiksinov. (1)IaMR-analiz konformatsii polimiksinov B i M.

Spatial structures of two polymyxin antibiotics are compared by means of one- and two-dimensional 1H NMR spectroscopy. Cyclic parts of polymyxins B and M contain a system of hydrogen bonds including two beta-turns, however, the analysis of coupling constants 3JHN-C alpha H demonstrated that torsional angles phi of peptide bonds of the residues forming beta-turns in polymyxin M depend on the type of the anion. An increase in lability of the polymyxin M cyclic part in comparison with polymyxin B correlated with the selective cleavage of the peptide bond Dab8-Dab9 of this antibiotic with subtilisin. A similar correlation was found for a short analogue of polymyxin B, a cycloheptapeptide.

[Structural and functional investigation of polymyxins. Structure and biological properties of polymyxin M analogs]. / Strukturno-funktsional'nye issledovaniia polimiksinov. Struktura i biologicheskie svoistva analogov polimiksina M.

The effect of proteinases of plant and microbial origin on polymyxin M was studied. It was shown that this antibiotic was absolutely stable to the effect of papain and ficin. On hydrolysis with subtilisin there formed polymyxin decyclized analogs not described earlier. Their isolation, purification and biological activity are described. The structure of these compounds was assessed by one- and two-dimensional 1H NMR spectroscopy. The role of various functional groups, their space orientation and impact on antimicrobial activity of the compounds are discussed.

[Structural and functional research on polymyxins. 1H NMR analysis of the conformation of polymyxin M in water]. / Strukturno-funktsional'nye issledovaniia polimiksinov. 1H-IaMR-analiz konformatsii polimiksina M v vode.

Spatial structure of polypeptide antibiotic polymyxin M in water was studied by one-and two-dimensional (COSY, COSY-45, RELAY) H NMR spectroscopy. Analysis of the signal spectral parameters revealed two intramolecular hydrogen bonds in the cyclic part of the molecule which was analogous to the structure of polymyxin B. However, configuration of both the beta-turns in the polymyxin M structure differed from that of the detected earlier beta-turns in the structure of polymyxin B.

[Structural-functional research on polymyxins. 1H-NMR spectra of polymyxin B and its shortened analog]. / Strukturno-funktsional'nye issledovaniia polimiksinov. 1H-IaMR spektry polimiksina B i ego ukorochennogo analoga.

Polymyxin B and its shortened analog were studied comparatively by 1H-NMR spectroscopy. Analysis of the signal chemical shifts, constants of spin-spin interaction of 3J HN-C alpha H and temperature coefficients of the NH signal chemical shifts revealed absolute structural identity of both molecules cyclic parts. This proved that there was no conformative interaction between the cyclic and linear parts of the polymyxin B molecule. Comparison of the results with the data on the biological activity showed that the hydrophobic N-end moiety of the polymyxin B molecule played a specific role in its antibacterial effect and toxicity.

[Spin-labeling studies on interaction of phospholipase A2 from cobra poison with phospholipid membranes]. / Izuchenie vzaimodeistviia fosfolipazy A2 iz iada kobry s organizovannymi poverkhnostiami fosfolipidov metodom spinovykh zondov.

Phospholipase A2 interactions with phospholipid liposomes and vesicles were studied by using unhydrolysed spin-labeling 2-alkyl phosphatidylcholine. These interactions have polar nature. Phospholipase A2 hydrolyses only the neighbouring phospholipid monolayer. The hydrophobic layer of liposomes is not permeable for the enzyme. Phospholipase A2 are attached to lysophosphatidylcholine after hydrolysis and it stabilizes the structure of vesicles. The stabilizing effect of the enzyme makes the vesicles unpermeable for Na+, Cl-ions and protons. Moreover, the phospholipase A2 prevents the phospholipid exchange between the vesicles and their fusion.

[Phospholipase spin-labeled phospholipids interactions]. / Vzaimodeistvie fosfolipazy iz Iada kobry so spin-mechenymi fosfolipidami.

Enzyme-substrate interaction of phospholipase A2 (Naja naja oxiana) with phospholipids has been studied. Spin-labeled palmitic and stearic acids, 1-O-spin-labeled acyl-, 2-O-spin-labeled acylphosphatidyl choline and spin-labeled phosphatidyl-myo-inositol were used for this purpose. This method did not reveal hydrofobic fat-protein interaction. Phospholipase interacts only with the near lipid monolayer of liposomes and vesicles. Being formed lysophosphatidyl choline and fat acids lead to destruction of vesicles, but phospholipase renders stabilization effect.