[Structural-functional research on polymyxins. 1H-NMR spectra of polymyxin B and its shortened analog].

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.