Trace cobalt speciation in bacteria and at enzymic active sites using emission Mössbauer spectroscopy.

57Co emission Mössbauer spectroscopy (EMS) allows the chemical state of cobalt, as influenced by its coordination environment, to be monitored in biological samples at its physiological (trace) concentrations. To draw attention to EMS as a valuable tool for speciation of cobalt in biocomplexes, the process of cobalt(II) metabolism in cells of the plant growth-promoting rhizobacterium Azospirillum brasilense Sp245 was investigated using EMS of 57CoII-doped bacterial cells. EMS measurements also showed 57CoII-activated glutamine synthetase (GS, a key enzyme of nitrogen metabolism, isolated from this bacterium) to have two different cobalt(II) forms at its active sites, in agreement with data available on other bacterial GSs. Chemical after-effects following electron capture by the nucleus of the parent 57CoII during the 57Co-->57Fe transition, which contribute to the formation of a stabilised daughter 57FeIII component along with the nucleogenic 57FeII forms, are also briefly considered.

[Dosimetric basis of mean fractionation in the irradiation of bone metastases in breast cancer]. / Dozimetricheskoe obosnovanie srednego fraktsionirovaniia pri obluchenii kostnykh metastazov raka molochnoi zhelezy.

Proceeding from the drawing of maps with biologically isoeffective percentage doses the authors provide a dosimetric substantiation of gamma-beam irradiation of different parts of the bony skeleton using the following irradiation scheme: a single dose of 4 Gy, 5-6 fractions daily. It has been shown that to choose a therapeutic plan in the utilization of a nonstandard scheme of fractionation, the calculation of the TDF factor by Orton's tables is safe and illustrative. By way of example are given maps of isoeffective doses used in the irradiation of bone metastases in breast cancer patients with metastases to different parts of the skeleton.