Ionic Strength Of Reaction Mixture Research Articles

A study of ribonuclease activity in venom of vietnam cobra

BackgroundRibonuclease (RNase) is one of the few toxic proteins that are present constantly in snake venoms of all types. However, to date this RNase is still poorly studied in comparison not only with other toxic proteins of snake venom, but also with the enzymes of RNase group. The objective of this paper was to investigate some properties of RNase from venom of Vietnam cobra Naja atra.MethodsKinetic methods and gel filtration chromatography were used to investigate RNase from venom of Vietnam cobra.ResultsRNase from venom of Vietnam cobra Naja atra has some characteristic properties. This RNase is a thermostable enzyme and has high conformational stability. This is the only acidic enzyme of the RNase A superfamily exhibiting a high catalytic activity in the pH range of 1–4, with pHopt = 2.58 ± 0.35. Its activity is considerably reduced with increasing ionic strength of reaction mixture. Venom proteins are separated by gel filtration into four peaks with ribonucleolytic activity, which is abnormally distributed among the isoforms: only a small part of the RNase activity is present in fractions of proteins with molecular weights of 12–15 kDa and more than 30 kDa, but most of the enzyme activity is detected in fractions of polypeptides, having molecular weights of less than 9 kDa, that is unexpected.ConclusionsRNase from the venom of Vietnam cobra is a unique member of RNase A superfamily according to its acidic optimum pH (pHopt = 2.58 ± 0.35) and extremely low molecular weights of its major isoforms (approximately 8.95 kDa for RNase III and 5.93 kDa for RNase IV).

Kinetics of proton depended oxidation of diethylthiourea with methylene green in aqueous medium

Diethylthiourea (DETU) reacts with methylene green (MG) and reduced it into leuco dye where it oxidized into smaller fragments like urea, nitrate and sulphate. The reaction was favorable in acidic condition. A direct relation in between oxidation of DETU and MG to the concentration of H+ ions was observed through typical kinetics in two acids like HCl and H2SO4. The second order with respect to HCl and the first order with respect to H2SO4 indicated the protonation of DETU with the reduction of dye. In alkaline medium, the rate of reaction decline may be due to the suppressing effects of alkali on oxidation/degradation of DETU into smaller fragments or may be attributed with the de-protonation of DETU. Influence of addition of dye into reaction mixture retarded the bleaching process and follows zero order kinetics while rate of reaction enhanced by the addition of DETU in the reaction mixture and shows ¾th order with respect to DETU. Negative effect of added different electrolytes reflects that change of ionic strength of reaction mixture have some bearing on redox reaction of MG and DETU. Reaction was monitored at elevated temperature and activation parameters were computed. The mechanisms of oxidation of DETU with reduction of dye MG were discussed. Reduction of MG into leuco dye with the fragmentation of DETU was observed in acidic condition at elevated temperature. Key words: Methylene green (MG), diethylthiourea (DETU), proton dependence, smaller fragments, redox reaction, ions.