NISCAIR Online Periodicals Repository Collection: IJBB Vol.46(5) [October 2009]

Effect of mercury ion on the stability of the lipid-protein complex of isolated chloroplasts

Mon, 28 Sep 2009 22:58:59 GMT

Title: Effect of mercury ion on the stability of the lipid-protein complex of isolated chloroplasts

Authors: Panda, Sunakar; Panda, Sumita

Abstract: Mercury is known to interact with different parts of living systems causing serious biochemical and physiological disorder. In order to know the effect of mercury (Hg²⁺) ion on chloroplasts, the cell free organelle are incubated in an isotonic buffer medium in presence of mercury ion. The metal ion is found to induce membrane lipid peroxidation, loss of photosynthetic pigments and degradation of proteins. Such degradation brings about a drastic modification of lipid-protein organization of chloroplasts as reflected from a blue shift of absorption peaks and lowering of chlorophyll-a fluorescence intensity. The detrimental effect of Hg²⁺ ion has been explained in terms of direct binding with lipid-protein complex of photosynthetic membrane. Such a binding of metal ion exposes the lipid-protein complex for an easier entry and attack of reactive oxygen species (ROS) generated during incubation of chloroplasts in light and dark, thereby resulting in higher disorganization, which is evident from cation- induced changes in absorption and emission characteristics of the organelle.

Page(s): 405-408

Partial purification and some properties of -amylase from Bacillus subtilis KIBGE-HAS

Mon, 28 Sep 2009 22:58:59 GMT

Title: Partial purification and some properties of -amylase from Bacillus subtilis KIBGE-HAS

Authors: Bano, Saeeda; Qader, Shah Ali Ul; Aman, Afsheen; Azhar, Abid

Abstract: An extracellular -amylase from Bacillus subtilis KIBGE-HAS was partially purified by ultrafiltration and ammonium sulphate precipitation with 19.2-fold purification and specific activity of 4195 U/mg. The enzyme showed relatively high thermostability and retained 62% of its activity when kept at 70°C for 15 min. -Amylase was highly stable at -18°C and loss of activity was very low during stability study. Metal ions like Mn²⁺, Ca²⁺,Co²⁺, K⁺, Mg²⁺, and Fe³⁺ activated the enzyme, while Hg²⁺ Ba²⁺, Cu²⁺, Na⁺ and Al³⁺ strongly inhibited the activity. The α-amylase was highly stable in various surfactants and detergents. In the presence of surfactants such as SDS and Triton X-100 the enzyme activity was found 2.9 and 1.8-fold higher respectively than control. The non-ionic detergents (Tween 20 and Tween 80) exhibited slightly inhibitory effect on the enzyme activity.

Page(s): 401-404

Analysis of comparative efficiencies of different transformation methods of E. coli using two common plasmid vectors

Mon, 28 Sep 2009 22:58:59 GMT

Title: Analysis of comparative efficiencies of different transformation methods of E. coli using two common plasmid vectors

Authors: Roychoudhury, Aryadeep; Basu, Supratim; Sengupta, Dibyendu N

Abstract: The efficiencies of different transformation methods of E. coli DH5_αstrain, induced by several cations like Mg²⁺, Mn²⁺, Rb⁺ and especially Ca²⁺, with or without polyethylene glycol (PEG) and dimethyl sulfoxide (DMSO) were compared using the two commonly used plasmid vectors pCAMBIA1201 and pBI121. The widely used calcium chloride (CaCl₂) method appeared to be the most efficient procedure, while rubidium chloride (RbCl) method was the least effective. The improvements in the classical CaCl₂ method were found to further augment the transformation efficiency (TR)_E for both the vectors like repeated alternate cycles of heat shock, followed by immediate cold, at least up to the third cycle; replacement of the heat shock step by a single microwave pulse and even more by double microwave treatment and administration of combined heat shock-microwave treatments. The pre-treatment of CaCl₂-competent cells with 5% (v/v) ethanol, accompanied by single heat shock also triggered the (TR)_E, which was further enhanced, when combined heat shock-microwave was applied. The minor alterations or improved approaches in CaCl₂ method suggested in the present study may thus find use in more efficient E. coli transformation.

Page(s): 395-400

Kinetics of oxidation of adenosine by tert-butoxyl radicals: Protection and repair by chlorogenic acid

Mon, 28 Sep 2009 22:58:59 GMT

Title: Kinetics of oxidation of adenosine by tert-butoxyl radicals: Protection and repair by chlorogenic acid

Authors: Vijayalakshmi, G; Adinarayana, M; Rao, P Jayaprakash

Abstract: The rates of oxidation of adenosine and chlorogenic acid by tert-butoxyl radicals (t-BuO^-) were studied by measuring the absorbance of adenosine at 260 nm and chlorogenic acid at 328 nm spectrophotometrically. t-BuO^- radicals were generated by the photolysis of tert-butyl hydroperoxide (t-BuOOH) in presence of tert-butyl alcohol to scavenge OH^.radicals. The rates and the quantum yields() of oxidation of chlorogenic acid by t-BuO^-radicals were determined in the absence and presence of varying concentrations of adenosine. An increase in the concentration of adenosine was found to decrease the rate of oxidation of chlorogenic acid, suggesting that adenosine and chlorogenic acid competed for t-BuO^. radicals. From competition kinetics, the rate constant of chlorogenic acid reaction with t-BuO^- was calculated to be 3.20 10⁹ dm³ mol^-1 s^-1. The quantum yields (_expt) were calculated from the experimentally determined rates of oxidation of chlorogenic acid under different experimental conditions. Assuming that chlorogenic acid acts as a scavenger of t-BuO^- radicals only, the quantum yields (_cal) were theoretically calculated. _expt and _cal values suggested that chlorogenic acid not only protected adenosine from t-BuO^- radicals, but also repaired adenosine radicals, formed by the reaction of adenosine with t-BuO^-radicals.

Page(s): 389-394