Results of irradiating chick embryos during incubation with very low doses of penetrating radiation

The weight of chick embryos and their organs increases and the mortality rate of embryos decreases under chronic gamma-irradiation during incubation with very low doses the dose-rate being 7.5 times as high as that of natural radiation background.     

A comparative study of sphingolipids in transplanted melanomas with high and low metastatic activity

The content of sphingolipids in M3 and B16/F10 melanomas with a high metastatic potential and in Claudmanís and B16/F1 melanomas with a low metastatic potential was studied. It was shown that the content of total lipid-bound sialic acids and ganglioside GM3 in melanomas with a high metastatic potential is considerably higher than that in melanomas with a low metastatic potential. On the other hand, the ceramide to glucosylceramide molar ratio is higher in melanomas with a low metastatic potential.     

Isolation of ribosomes from Escherichia coli by chromatography on methyl-albumin-kieselgel.

The present communication shows that ribosomes isolated by differential centrifugation retain their composition and biological activity during subsequent methyl-albumin-kieselgel (MAK)-chromatography. The data obtained were used to develop a novel chromatographic procedure for the isolation of ribosomes from E. coli lysates. It could be demonstrated that purified preparations of active ribosomes can be obtained by MAK-chromatography avoiding ultracentrifugation.     

Biogeochemical approaches to assessment of East Asian ecosystem sensitivity to acid depositon

We used the critical load (CL) concept to calculate ecosystem response to acid deposition in East Asia. The calculation of critical loads to assess the sensitivity of ecosystems to acidic deposition was made using a biogeochemical approach, which took into consideration both rates of biogeochemical cycling and temperature responses. On the basis of these data the soil-biogeochemical mapping has been carried out for the area of East Asia and the CL values for acid-forming compounds have been calculated using modified steady-state mass balance (SSMB) equations. In the north-eastern ecosystems of the Asian part of Russia these values of critical loads for N [CL(N)] and S [CL(S)] compounds are shown to be less than in Europe due to peculiarities of climate, soil and vegetation. The minimum values of both CL(N) and CL(S) are <50 eq/ha/yr (which occur in 8.3% and 40.5% of this area for N and S, correspondingly) and the maximum values are >300 eq/ha/yr. These values are occasionally lower than for corresponding European ecosystems. For the south-eastern ecosystems of the northern part of Thailand the minimum values are <200 eq/ha/yr and maximum values are >700 eq/ha/yr. The minimum CL values (<200 eq/ha/yr) occur in more than 75% of the studied Thai area.     

Nature of the intermediate compound formed during catalysis by pepsin]

The applicability of the free energies linearity principle to catalysis by pepsin may indicate that the mechanism of formation of a covalent pepsin intermediate with the second (amine or alcohol) part of the hydrolyzed substrate is a true one. The choice has been made from consideration of three possible types of mechanisms covalent binding, complex with a nonionized NH2-group and the absence of an activated intermediate.     

Submergence of Micrococcus lysodeikticus F1-ATPase into the hydrophobic phase of the membrane, using 2,4,6-trinitrobenzosulfonate and 12-0-(azidoformyl) stearic acid methyl ester

The accessibility of F1-ATPase from Micrococcus lysodeikticus in solution and in the membrane for the specific water-soluble NH2-group reagent, 2,4,6-trinitrobenzosulfonate (TNBS), was studied. Incubation of the soluble factor F1 with 50 mM TNBS pH 8.3 results in incorporation of 58.6 +/- 4.4 trinitrophenyl residues per mole of enzyme. At the same time F1-ATPase isolated from TNBS-pretreated membranes contains 27.2 +/- 2.0 TNP-residues per mole of enzyme. It is assumed that the different accessibility of F1-ATPase for TNBS in solution and in the membrane is due to incorporation of F1-ATPase into the membrane. Study of membrane F1-ATPase interaction with the radioactive lipid-soluble photoreactive label, 12-0-(azidoformyl) stearic acid methyl ester demonstrated that F1-ATPase does not immediately interact with the lipid phase of the membrane. It is suggested that membrane F1-ATPase may be enveloped by hydrophobic proteins.     

Possible relationship of mechanisms of Mn2+ oxidation and formation of plant photosystem II manganese cluster.

The mechanisms of Mn2+ cation oxidation in alkaline, neutral and slightly acidic media were studied. In all cases, the Mn2+ oxidation resulted in the formation of the structure[see text]. The formal resemblance and differences in the Mn2O3 structure and Klein's model of the Mn cluster of PS II were noted. The necessity of the primary ligation of Mn2+ cations was discussed for both the decrease in the Mn2+ oxidation potential and the stability of the Mn2O3 structure. It was supposed that Mn2O3 is an initial block for the assembly of the inorganic core of the photosynthetic water-oxidizing complex.