http://nopr.niscair.res.in/handle/123456789/3475 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/3731 Title: Inhibition of the hexokinase/hexose transporter region in the glycosomal membrane of bloodstream Trypanosoma brucei by oligomycin and digitonin <br/> <br/>Authors: Njogu, Muturi R; Kiaira, Job K <br/> <br/>Abstract: Glycolysis in bloodstream T. brucei is the sole source of energy and remains a favourable chemotherapeutic target. In furtherance of this, an attempt has been made to understand better the contribution of glucose, fructose, mannose and glycerol to the energy charge of these parasites incubated in the presence of oligomycin, salicyhydroxamic acid (SHAM) and digitonin. Their cellular energy charge, when catabolizing glucose was 0.860, and under inhibition by oligomycin (10 μg), SHAM (2 mM) or oligomycin plus SHAM, 0.800, 0.444 and 0.405, respectively. Oligomycin inhibited the rate of catabolism of glucose, mannose and fructose up to 80%. The inhibition could not be alleviated by uncouplers, such as 2,4-dinitrophenol or permeabilization of the membranes by digitonin. Glucose-6-phosphate and other phosphorylated glycolytic intermediates, such as fructose-6-phosphate were catabolized by the permeabilized parasites in the presence of oligomycin, implying that except hexokinase, all the other glycolytic enzymes were active. Glucose oxidation was stimulated by low concentrations of digitonin (up to 4 μg), but at higher concentrations, it was significantly inhibited (up to 90% inhibition at 10 μg). Apparently, the inhibitory effects of oligomycin and digitonin were confined to glucose uptake and hexokinase catalysis. The above observations suggest that the hexose transporter and the enzyme hexokinase might be functionally-linked in the glycosomal membrane and oligomycin inhibits the linkage, by using a mechanism not linked to the energy charge of the cell. Digitonin at concentrations higher than 4 μg disrupted the membrane, rendering the complex in-operative. A hexokinase/hexose transporter complex in the glycosomal membrane is envisaged. <br/> <br/>Page(s): 329-332 Sun, 28 Nov 2004 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/3730 Title: Determination of serum triglycerides using lipase, glycerol kinase, glycerol-3-phosphate oxidase and peroxidase co-immobilized onto alkylamine glass beads <br/> <br/>Authors: Kalia, Vandana; Pundir, Chandra S <br/> <br/>Abstract: A method for determination of serum triglycerides (Tgs) using lipase, glycerol kinase, glycerol-3-phosphate oxidase and peroxidase co-immobilized onto alkylamine glass beads (pore diameter 55 nm) through glutaralde¬hyde coupling was developed and evaluated. The minimum detection limit of the method was 0.54 mM. The analytical recovery of added triolein in the serum was 97.55±1.5% (mean ± S.D.). The mean value of serum Tgs, determined by the present method showed a good correlation (r=0.984) with the Bayer’s kit method, employing free enzymes. The within and between batch coefficients of variation (CV) were <2.25% and <1.35% respectively. No significant loss of activity was observed, when co-immobilized enzymes were reused for about 200 times and stored at 4°C in distilled water. The cost of Tg determination for 200 serum samples was less, as compared with Bayer’s kit method. <br/> <br/>Page(s): 326-328 Sun, 28 Nov 2004 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/3729 Title: Phonon dispersion in polyinosinic acid <br/> <br/>Authors: Srivastava, Seema; Srivastava, Shinoo; Khan, Irfan Ali; Pandey, M K; Gupta, V D <br/> <br/>Abstract: A study of the normal modes of vibration and their dispersion in polyinosinic acid [poly (I)] along the helix axis based on Urey-Bradley force field is reported. It leads to a better interpretation of Raman and FTIR spectra. A comparison of dispersion curves of poly (I) with poly (G) has been made. Characteristic features of dispersion curves, such as regions of high density-of-states, repulsion and character mixing are discussed. Predictive value of heat capacity as a function of temperature is reported. <br/> <br/>Page(s): 311-321 Sun, 28 Nov 2004 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/3728 Title: Partial purification, characterization and properties of two isoforms of glutamine synthetase from Pennisetum glaucum L. leaves <br/> <br/>Authors: Ghosh, Shilpi <br/> <br/>Abstract: Two isozymes of glutamine synthetase GS₁ and GS₂ were partially purified from Pennisetum glaucum leaves by ion-exchange and gel filtration chromatography and their kinetic and regulatory properties were studied using semisynthetase assay of GS. Mg²⁺ was the most effective cation for activity of both the isozymes; however, it could be efficiently replaced by Co ²⁺.The pH optima for GS₁ and GS₂ were 7.0 and 8.0, respectively. GS₁ exhibited maximum activity at 42ºC, with activation energy of 18 KJ mol^-1 and a Q₁₀ of 3.0, whereas GS₂ showed maximum activity at 50ºC, with activation energy of 40 KJ mol^-1 and Q₁₀ of 2.25. GS₁ was more thermostable than GS₂. The K_m value for Mg²⁺ of GS₁ was 2-fold higher than GS₂; however, these isozymes did not differ much in their affinity for other substrates. Alanine, serine and glycine lowered GS₁ and GS₂ activities, whereas cysteine enhanced their activities with a more pronounced effect on GS₂. Serine inhibited the activity of both the isoforms in a competitive-manner, whereas alanine was a non-competitive inhibitor, with respect to glutamate. AMP and ADP were competitive inhibitor with respect to ATP for both the isozymes. <br/> <br/>Page(s): 288-293 Sun, 28 Nov 2004 22:58:59 GMT