[Assessment of the composition and structure of covalent complexes of superoxide dismutase with aldehyde dextran by analytical ultracentrifugation].

Superoxide dismutase was covalently coupled wih aldehyde dextran, a polymeric carrier of molecular mass of 70 kDa. Modification produced an increase in the enzyme thermostability. Modified preparations retained a high specific activity.

[Emission spectroscopic determination of the 15N in the ammonia and amino acids isolated from biological material].

A procedure for preparation of samples is described for emission-spectroscopic estimation of 15N in ammonia, glutamic aspartic acids, leucine and glycine using 15N-analyzer NOI-5. The assay involved separation of ammonia and amino acids by means of ion exchange chromatography, degradation of amino acids to ammonia its isolation by microdiffusion from buffers and subsequent reduction of ammonia to nitrogen. Amount of nitrogen in the samples was about 20 mg.

[Neutralization of ammonia in cardiac muscle].

The pathways of ammonia neutralization in the rat heart muscle were traced with nitrogen-15 isotope. The effect of ammonia concentration in the perfusate on its utilization by the myocardium was investigated over the range of 1.6--3.

[Urea synthesis in the myocardium].

Urea synthesis was studied in the isolated rat heart-perfused with ammonium chloride (10 mM), mixtures of ammonium chloride (10 mM) and 1-aspartic acid (10 mM), 1-ornithine (2.5 mM), 1-arginine (10mM), 1-glutamine (10 mM), 1-alanine (10 mM), 1-leucine (5 mM) and pyruvate (5mM). Ammonium chloride and 1-arginine are the most effective activators of urea synthesis, while 1-leucine and pyruvate produce an inhibitory action.

[Modification of a method of determining 15N in biological material].

A method is described for preparation of nitrogen samples and estimation of 15N concentration in free amino acids and urea, isolated from heart muscle, using mass-spectometric analysis. Components of the tissue extracts were separated at the preparative scale; amino acids and urea were desalted by means of ion exchange chromatography. CHN-analyzer was used to measure content of nitrogen in urea and amino acids.