[Study of conformation transitions in proteins by tryptophan fluorescence and phosphorescence at low temperatures]. / Issledovanie konformatsionnykh perekhodov v belkakh po triptofanovoi fluorestsentsii i fosforestsentsii pri nizkikh temperaturakh.

The well-known conformational changes in proteins containing a single tryptophan residue, such as pH-induced N-->F transition in human serum albumin, pH-induced acidic transition in cod parvalbumin, and KCl-induced tetramerization of bee venom melittin were monitored by changes in low temperature phosphorescence and fluorescence spectra suggesting two independent series of normal components. Parameters of low temperature tryptophan luminescence were sensitive to chromophore environment. A correlation of changes of some spectral parameters with accessibility of tryptophan to water was revealed, however, spectral changes mainly depend on specific interactions of the chromophore with its environment.

[Analytical description of electron-vibrational protein spectra]. / Analiticheskoe opisanie élektronno-kolebatel'nykh spelktrov belkov.

Electron-vibrational spectra of phosphorescence and fluorescence of tryptophan residues in proteins at 77 K are best approximated by theoretical curves computed according to a model which suggests the existence of two independent series of Gaussian vibrational components. Each series contains one type of vibrations. Phosphorescence and fluorescence spectra of proteins with various localizations of their single tryptophan residue were fitted by a curve computed according to this model. The results obtained show that the phosphorescence band of tryptophan residues in proteins seems to contain two types of vibrations with frequencies 650-800 cm-1 and 1350-1500 cm-1. Since the substitution of H2O by D2O does not change the frequencies of both vibrations in the phosphorescence spectra of human serum albumin, melittin and tryptophan in 1 M KCl, it is reasonable to suggest that the 1350-1500 cm-1 series corresponds to the W5 type vibrations (B19a type of vibrations of benzene ring). The 650-800 cm-1 series"can be identified with W18 type of vibrations (breathing vibrations of indole ring). Phosphorescence parameters of tryptophan residues in proteins correlate with their fluorescence parameters.

[Kinetics of dissociation of parvalbumin complexes with calcium and magnesium ions]. / Kinetika dissotsiatsii kompleksov parval'bumina s ionami kal'tsiia i magniia.

Dissociation kinetics of parvalbumin complexes with calcium and magnesium ions were studied by means of stopped-flow method employing intrinsic protein fluorescence registration. In the temperature range from 10 to 30 degrees C the kinetic curves of Ca2+ and Mg2+ dissociation are best fitted with a sum of two exponential terms, each term is ascribed to a dissociation process in one of two bindings sites of parvalbumin. Dissociation rate constants in this temperature range increase from 0.03 to 0.8 s-1 and from 0.18 to 5 s-1 for Ca2+, and from 0.9 to 4.5 s-1 and from 4 to 33 s-1 for Mg2+. Parvalbumin equilibrium binding constants of Ca2+ and Mg2+ were also measured in the same temperature range. It makes possible to estimate the rate constants of association of Ca2+ and Mg2+. In the case of Ca2+ the rate of association approaches the diffusion controlled limit.