Increase in osmotolerance of Rhizobium fredii soybean isolate BD32 by the proB proA operon of Escherichia coli.

The proB proA operons (which are blocked by the feedback inhibition of proline production) of Escherichia coli wild type or with the mutation proBosm, blocking feedback inhibition effect of proline production, were cloned in a broad host range shuttle vector pVA 12-2. The hybrid plasmids pLVA(proB+A+) and pNSA(proBosm proA), were transferred into a low level osmotolerance Rhizobium fredii strain BD32. Both types of transconjugants were characterised by increased osmotolerance in a minimal medium supplied with 0.4-0.8 M NaCl but in the case of pNSA the effect was more significant. The strain BD32/pNSA had an increased level of intracellular proline concentration. Practical application of the increase in Rhizobium resistance to the stress factors is discussed.

The solid-state catalytic synthesis of tritium labeled amino acids, peptides and proteins.

New catalytic reaction between a solid bioorganic compound and activated spillover tritium (ST), based on High-temperature Solid-state Catalytic Isotopic Exchange (HSCIE) was examined. The HSCIE mechanism and determination of the reactivity of hydrogen atoms in amino acids, peptides and proteins was investigated. Quantum mechanical calculations of the reactivity of hydrogen atoms in amino acids in the HSCIE reaction were done. The carbon atom with a greater proton affinity undergoes a greater exchange of hydrogen for tritium in HSCIE. The electrofilic nature of spillover hydrogen in the reaction of HSCIE was revealed. The isotope exchange between ST and the hydrogen of the solid organic compound proceeds with a high degree of configuration retention at the carbon atoms. The HSCIE reaction enables to synthesize tritium labeled proteins with a specific activity of 20-30 mCi/mg and kept biological activity.