Effect of indometofen on the survival and bone marrow hemopoiesis of mice exposed to acute external gamma- or X-ray irradiation

The purpose of the study is evaluation of radioprotective effectiveness of indometofen at its prophylactic administration in conditions of acute irradiation. Evaluation of radioprotective efficiency was performed by studying the 30-day survival rate, life expectancy, structure of deathly irradiated mice, and bone marrow hemopoiesis using methods of endogenous and exogenous colony formation. The prophylactic application of indometofen at doses 30 mg/kg for 5 days before irradiation has been observed to protect mice against radiation death induced by gamma or X-ray exposures at doses LD(50-70/30), increasing their survival rate by 16-44%, and reduce severity of post radiation disorders of bone marrow hemopoiesis.     

On the kinetics of voltage formation in purple membranes of Halobacterium salinarium.

The kinetics of the bacteriorhodopsin photocycle, measured by voltage changes in a closed membrane system using the direct electrometrical method (DEM) of Drachev, L.A., Jasaitus, A.A., Kaulen, A.D., Kondrashin, A.A., Liberman, E.A., Nemecek, I.B., Ostroumov, S.A., Semenov, Yu, A. & Skulachev, V.P. (1974) Nature 249, 321-324 are sixfold slower than the kinetics obtained in optical studies with suspensions of purple membrane patches. In this study, we have investigated the reasons for this discrepancy. In the presence of the uncouplers carbonyl cyanide m-chlorophenylhydrazone or valinomycin, the rates in the DEM system are similar to the rates in suspensions of purple membrane. Two alternative explanations for the effects of uncouplers were evaluated: (a) the 'back-pressure' of the Deltamicro;H+ slows the kinetic steps leading to its formation, and (b) the apparent difference between the two systems is due to slow major electrogenic events that produce little or no change in optical absorbance. In the latter case, the uncouplers would decrease the RC time constant for membrane capacitance leading to a quicker discharge of voltage and concomitant decrease in photocycle turnover time. The experimental results show that the primary cause for the slower kinetics of voltage changes in the DEM system is thermodynamic back-pressure as described by Westerhoff, H.V. & Dancshazy, Z. (1984) Trends Biochem. Sci. 9, 112-117.     

Interrelations of M-intermediates in bacteriorhodopsin photocycle.

The photocycles of the wild-type bacteriorhodopsin and the D96N mutant were investigated by the flash-photolysis technique. The M-intermediate formation (400 nm) and the L-intermediate decay (520 nm) were found to be well described by a sum of two exponents (time constants, tau 1 = 65 and tau 2 = 250 microseconds) for the wild-type bR and three exponents (tau 1 = 55 microseconds, tau 2 = 220 microseconds and tau 3 = 1 ms) for the D96N mutant of bR. A component with tau = 1 ms was found to be present in the photocycle of the wild-type bacteriorhodopsin as a lag-phase in the relaxation of photoresponses at 400 and 520 nm. In the presence of Lu3+ ions or 80% glycerol this component was clearly seen as an additional phase of M-formation. The azide effect on the D96N mutant of bR suggests that the 1-ms component is associated with an irreversible conformational change switching the Schiff base from the outward to the inward proton channel. The maximum of the difference spectrum of the 1-ms component of D96N bR is located at 404 nm as compared to 412 nm for the first two components. We suggest that this effect is a result of the alteration of the inward proton channel due to the Asp96-->Asn substitution. Proton release measured with pyranine in the absence of pH buffers was identical for the wild-type bR and D96N mutant and matched the M-->M' conformational transition. A model for M rise in the bR photocycle is proposed.     

Homogeneous Cl. perfringens alpha-anatoxin: its physicochemical and immunogenic properties]

The authors present a method of obtaining relatively homogeneous preparations of alpha-toxoid of Cl. perfringens, type A, including the primary conception of the alpha-toxin proteins, their chromatography on DEAE-cellulose, fractionation with (NH4)2SO4, detoxication, with the subsequent gel-filtration through sephadex and isoelectric focussing. Sedimentation coefficient of the preparation proved to be 3.8 S, isoelectric point-4.83 +/- 0.07. In studying the immunogenic properties of alpha-toxoid in experiments on guinea pigs and rabbits their high immunogenicity, exceeding that of the industrial toxoid 8- and 6-fold, respectively, was established. Homogeneous preparations of alpha-toxoid provided intense anti-microbial immunity. Interlinear differences in the levels of the immune response of inbred mice, highly-reactive (BALB/c) and low-reactive (C57BL/6) to alpha-toxoid, reached 20-fold; in combination with the high immunogenicity of this antigen for mice this permits to recommend it for immunogenic studies.     

Low cetyltrimethylammonium bromide concentrations induce reversible amorphous aggregation of tobacco mosaic virus and its coat protein at room temperature

Ordered and amorphous protein aggregation causes numerous diseases. Tobacco mosaic virus coat protein for many decades serves as the classical model of ordered protein aggregation ("polymerization"). It was also found to be highly prone to heat-induced amorphous aggregation and the rate of this aggregation could be easily manipulated by changes in solution ionic strength and temperature. Here, we report that rapid amorphous aggregation of this protein can be induced at 25 degrees C in phosphate buffer by low micromolar (start at about 15 microM) concentrations of cationic surfactant cetyltrimethylammonium bromide. At equilibrium four surfactant molecules bound to the protein subunit. As judged by circular dichroism and fluorescence spectroscopy data, the coat protein molecules retained their native structure upon the cetyltrimethylammonium bromide induced aggregation. No aggregation was observed at the higher surfactant concentrations (above 300 microM). Micromolar concentrations of anionic surfactant sodium dodecylsulfate rapidly reversed the cetyltrimethylammonium bromide induced aggregation of the coat protein due to formation of mixed surfactant-surfactant micelles. Cetyltrimethylammonium bromide (100-300 microM) also induced the reversible intact tobacco mosaic virus virion aggregation. The possible liability to the cetyltrimethylammonium bromide induced amorphous aggregation of other ordered aggregate-producing proteins has been discussed.     

The sodium cycle. III. Vibrio alginolyticus resembles Vibrio cholerae and some other vibriones by flagellar motor and ribosomal 5S-RNA structures

An electron microscopic study of the basal bodies of the Vibrio albinolyticus flagellum revealed a four-disc structure. The diameters of the two discs localized closer to the cytoplasmic membrane proved to be about 2-fold shorter than those of the two others. In this respect the basal body of V. alginolyticus resembles very much that of V. cholerae described by Ferris and co-workers. The sequence of the V. alginolyticus ribosomal 5S-RNA showed that it is similar to those of V. cholerae, V. harveyi and some other vibriones. On the basis of the 5S-RNA sequences, a dendrogram of prokaryotes is presented. It confirmed the suggestion that V. alginolyticus is a typical representative of Vibrionaceae rather than a 'monster' greatly differing from other vibriones. Possible evolutionary relation of various bacterial species possessing the primary Na+ pumps is discussed.     

An investigation of the electrochemical cycle of bacteriorhodopsin analogs with the modified ring

5,6-Epoxy-, 4-methoxy-, 4-hydroxy-, and 3,4-dehydrobacteriorhodopsins can generate delta psi coupled to a photochemical cycle with intermediate M. The kinetics of delta psi comprises three main electrogenic phases: the fast small negative, the microsecond, and the millisecond positive phases. The photocycle efficiency is lower in all the analogs. The photocycle is modified insignificantly only in 3,4-dehydrobacteriorhodopsin. In the other pigments the decay of the flash-induced bleaching in the chromophore main absorption band is slower than the decay of M or long-wave intermediates, especially in the 4-hydroxy analog. In the latter analog, such distinctions, according to delta pH measurements, are partly due to deceleration of the decay of the novel intermediate (P). In 5,6-epoxybacteriorhodopsin, at all wavelengths, the decay of the intermediates takes seconds upon M formation. According to our and literature data, no bacteriorhodopsin analogs are known to have a cycle which preserves the M-intermediate and does not transport a proton.     

Activity of penicillin acylase from E. coli in the reversed-micelle system AOT--H2O--octane

The behavior of a penicillin acylase from E. coli was studied in the reversed-micelle system AOT--H2O--octane. Kinetic studies of the enzymatic hydrolysis of the m-carboxy-p-nitroanilide of phenylacetic acid, titration of the penicillin acylase active site with an irreversible specific inhibitor (phenylmethylsulfonyl fluoride), sedimentation analysis at different hydration degrees, and chemical modification showed that the enzyme loses no more than 20% of its initial activity during 3-4 h in the reversed-micelle systems of different hydration degrees and retains its catalytically active structure.     

Investigation by focused laser beam scanning of the photoelectric activity of bacteriorhodopsin-containing lipid bilayers.

The photoelectric activity of different parts of lipid bilayer containing bacteriorhodopsin was investigated by moving a small actinic light spot across the Plateau-Gibbs border and the bimolecular part of this reconstituted model membrane. The results give direct evidence that bacteriorhodopsin incorporated into the bimolecular region of the lipid membrane is responsible for the photoelectric activity of this system. A technique for scanning the photoelectric activity of a modified bimolecular lipid membrane is described in detail.     

C(13)-substituted bacteriorhodopsin analogs

13-Ethyl-, 13-isopropyl-, 13-tert-butyl-, 13-phenyl-, 13-alpha-naphthyl-, and 13-demethyl-retinals were synthesized and incubated with bacterioopsin (bO) to give the corresponding bacteriorhodopsin (bR) analogs. The capability of the 13-tert-butyl- and 13-alpha-naphthyl-bRs to exist and to photocycle shows that apparently around C(13) of the chromophore there lies a large enough cavity. A study of the light-induced conversions of the artificial pigments prepared has shown that the introduction at position 13 of the chromophore of the hydrocarbon substituents bulkier than that of the natural bR diminished the amplitudes of the electric photoresponses. Bulky C(13)-substituents or absence of substitution at that position decelerated the relaxation of the M-intermediates and disturbed the 13-cis-in equilibrium all-trans-isomerization.