[The effect of chronic UVB-radiation on the nitrogen-fixing capability of soils in a field experiment]. / Deistvie khronicheskogo UF-izlucheniia zony B na azotfiksiruiushchuiu sposobnost' pochv v usloviiakh polevogo éksperimenta.

The effect of chronic UV-B-irradiation on the nitrogen-fixing ability of soil was studied in a field experiment. In the study, LER-40 lamps were used as a source of additional UV-B-irradiation with respect to natural illumination (the irradiation level = 0.34, 0.49 and 0.77 W/m2). Nitrogen-fixation was measured by gas chromatography. The experimental results were treated by bifactorial analysis of variance. It was found that chronic UV-B-irradiation affected the nitrogen-fixing ability of soil during the observation period (June-August). At soil UV-B-irradiation of 0.34 and 0.49 W/m2 the nitrogen-fixation intensity increased by 17 and 9%, respectively, and at soil UV-B-irradiation of 0.77 W/m2 it decreased by 13%, when compared to untreated controls.

[Examination of the action of effectors after storing glutamine synthetase from the fodder yeast Candida tropicalis at room temperature]. / Issledovanie kharaktera deistviia effektorov posle vyderzhivaniia gliutaminsintetazy kormovykh drozhzhei pri komnatnoi temperature.

The pattern of action of effectors (AMP, IMP, CMP, anthranilic acid, tryptophane, alanine, glutamine, glycine, histidine) and glutamine synthetase (GS) extracted from the fodder yeast Candida tropicalis and stored at room temperature for 1.5-2 hrs was examined. As regards the action of effectors on GS after its exposure at room temperature, they can be subdivided into four groups: 1) the effector loses completely its inhibitory effect (glutamine, CMP, anthranilic acid in the synthetase reaction); 2) the inhibitory effect on the enzyme increases (AMP, IMP, anthranilic acid in the transferase reaction); 3) at low concentrations of the effector the peak of activation appears (tryptophane, GMP, alanine, glycine); 4) at low concentrations of the enzyme two peaks of activation appear (histidine). Similar results were obtained with the purified preparation of GS.

[Thermostability of glutamine synthetase in Candida tropicalis feed yeasts in Mg-, Mn- and Co-activated systems]. / Termostabil'nost' glutaminsintetazy u kormovykh drozhzhei Candida tropicalis v Mg-, Mn- i Co-aktiviruemoi sistemakh.

The thermostability of glutamine synthetase of Candida tropicalis was studied in systems activated by Mg, Mn and Co. The enzyme was found to be very thermolabile. Its thermostability depended on the nature of a bivalent cation used in the reaction mixture. Metals stabilized the enzyme since preincubation with metal cations increased the thermostability of glutamine synthetase. Purification of the enzyme preparation increased the stabilizing action of bivalent cations (Mg2+, Mn2+, Co2+).

[Effect of p-chloromercuribenzoate on glutamine synthetase in the food yeast Candida tropicalis]. / Vliianie p-khlormerkuribenzoata na glutaminsintetazu kormovykh drozhzhei Candida tropicalis.

The effect of p-CMB on the activity of glutamine synthetase in the fodder yeast Candida tropicalis was studied in the synthetase reaction in Mg-, Mn-, and Co-activated systems and in the transferase reaction. The activity of glutamine synthetase was inhibited by pCMB, the degree of inhibition depending on the presence of bivalent cations of metals. Preliminay incubation of the enzyme with p-CMB stimulated the action of the latter, whereas metals increased the stability of the enzyme to pCMB. If the enzyme preparation was purified, it became more susceptible to the action of p-CMB. The transferase activity was also inhibited by p-CMB but to a less extent that the synthetase reaction.