[Combined effect of Pb2+ and divalent mental complexes on superprecipation and ATPase activity of myometrial actomyosin]. / Sochetanoe deistvie Pb2+ i kompleksonov dvukhvalentnykh metallov na superpretsipitatsiiu i ATP-aznuiu aktivnost aktomiozina miometriia.

The inhibiting effect of Pb2+ (0.1-1.0 mM) on superprecipitation and ATPase activity of myometrium actomyosin has been shown. It is found out that of 11 studied chelators of bivalent cations only monosodium salt of 4-guanidino-1-hydroxybutyliden-1.1-bisphosphonic acid can efficiently renews the value of superprecipitation and ATPase activity of actomyosin in presence of lead ions. It is supposed that this renewal is underlied by binding of guanidin group of Pb ions.

[The influence of diphosphonic analogues of inorganic pyrophosphate on activity of RNA-polymerases from the calf thymus]. / Vliianie difosfonovykh analogov neorganicheskogo pirofosfata na aktivnost' rnk-polimeraz iz timusa telenka.

Diphosphonic analogues of inorganic pyrophosphate (PPi): methylene-, oxyethylidene-, aminomethylenediphosphonic acids as well as phosphonacetic, imidodiphosphoric bis- (phosphonomethyl)-phosphonic acids and methylenediphosphonic and phosphonic acid monoanhydrides were studied for their effect on the RNA-synthesizing activity of thymocytes. DNA-dependent RNA-polymerases I and II from the calf thymus nuclei were used for these studies. The analogues and PPi under study are shown to be inhibitors of both RNA-polymerases in nuclei from calf thymus and of purified RNA-polymerase II, which is more sensitive to the effect of diphosphonates. Methylenediphosphonic acid is the strongest inhibitor among the studied analogues, and imidodiphosphoric and phosphonacetic acids are the weakest inhibitors. Inhibition of purified RNA-polymerase II by diphosphonates has a complex character and includes both interaction of the PPi analogues with enzymes and chelating by them of Mn ions which are cofactors for RNA polymerase.