• Volume 11, Issue 1-4

      March 1987,   pages  1-579

    • Personal reflections

      Pakrashi P K Bhattacharyya Carl S Vestling

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    • Mammalian sulfoconjugate metabolism

      Joy Mathew A S Balasubramanian

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      Sulfoconjugates occur ubiquitously as sulfopolysaccharides, sulfolipids and sulfoproteins. A variety of sulfotransferases catalyze the sulfation process with 3’-phosphoadenosine 5’-phosphosulfate as the sulfate donor. Sulfatases that catalyze the desulfation of different sulfoconjugates are known to be deficient in a number of genetic storage disorders.

    • Metabolism of an isolated brain perfused with perfluoro blood substitute

      B Mukherji H A Sloviter

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      An unanesthetized, isolated, perfused rat brain, consisting of the skull and its contents with nearly all other tissues removed, has metabolic and electrical activity similar to that of the brain of the intact rat with its blood-brain barrier intact. Its use yielded results that are difficult or impossible to obtain fromin vitro preparations orin vivo. With the perfused brain it was shown that, mannose can completely replace glucose as metabolic substrate, that insulin has no direct effect on the brain, in the absence of added substrate glutamate is metabolized to aspartate, the brain does not metabolize ethanol, and morphine probably inhibits mitochondrial oxidative activity. Since the use of a perfluoro blood substitute to perfuse the brain avoids the optical interference caused by haemoglobin, it was possible to measure changes in the oxidation-reduction state of NADH by surface fluorometry of the cerebral cortex.

    • Radical intermediates in peroxide-dependent reactions catalyzed by cytochrome P-450

      Minor J Coon Alfin D N Vaz

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      Highly purified liver microsomal cytochrome P-450 acts as a peroxygenase in catalyzing the reaction, RH+ XOOH→ROH+XOH, Where RH represents any of a large variety of foreign or physiological substrates and ROH the corresponding product, and XOOH represents any of a series of peroxy compounds such as hydroperoxides or peracids serving as the oxygen donor and XOH the resulting alcohol or acid. Several experimental approaches in this and other laboratories have yielded results compatible with a homolytic mechanism of oxygen-oxygen bond cleavage but not with the heterolytic formation of a common iron-oxo intermediate from the various peroxides.

      Recently, we have found a new reaction, catalyzed by the reconstituted system containing the phenobarbital-inducible form of P-450, which catalyzes the reductive cleavage of hydroperoxides: XRR’C-OOH+ NADPH+H+→ XR’CO + R’H+H2O + NADP+ Thus, cumyl hydroperoxide yields acetophenone and methane, and 13-hydroperoxyoctadeca-9, 11-dienoic acid yields pentane and an as yet unidentified additional product. Since hydroperoxide reduction does not produce the corresponding alcohol, it is concluded that homolytic cleavage of the oxygen-oxygen bond occurs with rearrangement of the resulting alkoxy radical. Studies are in progress to determine how broad a role the new hydroperoxide cleavage reaction plays in the biological peroxidation of lipids.

    • Oligosaccharide structure determination of glycoconjugates using lectins

      Debkumar Basu Jyotiv Nair P S Appukuttan

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      Lectins, the divalent or polyvalent (glyco) proteins of non-immune origin of the cells agglutinate cells or other materials, that display more than one saccharide of sufficient complementarity. Lectins considered ‘identical’ in terms of mono-and disaccharide specificity can be differentiated by their ability to recognise the fine differences in more complex structures. The present review discusses the interaction of lectins with various oligosaccharides and their resultant separations due to structural variations.

    • Molecular biology of Ri-plasmid—A review

      Vilas P Sinkar Frank F White Milton P Gordon

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      Agrobacterium rhizogenes transfers a segment of its plasmid to the plant genome. The transferred DNA contains genes which are involved in the synthesis of plant hormones. These genes express in the plant cell and give rise to rooty-tumors at the infection site. Transgenic plants can be readily regenerated from the rooty-tumors and the transferred DNA is transmitted to progeny plants. High regeneration potential and sustained maintenance of transferred DNA makes the bacterium a suitable vector for plant genetic engineering. DNA sequences homologous to the transferred DNA ofAgrobacterium rhizogenes were detected in some untransformed plant species suggesting a past infection byAgrobacterium rhizogenes during evolution of some genera, notably Nicotiana.

    • Mode of action of lipoic acid in diabetes

      S S Wagh C V Natraj K K G Menon

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      Metabolic aberrations in diabetes such as hyperglycemia, ketonemia, ketonuria, reduced glycogen in tissues and reduced rates of fatty acid synthesis in the liver are corrected by the administration of lipoic acid. Dithiol octanoic acid is formed from lipoic acid by reduction and substitutes for Coenzyme A in several enzymatic reactions such as pyruvate dehydrogenase, citrate synthase, acetyl Coenzyme A carboxylase, fatty acid synthetase, and triglyceride and phospholipid biosynthesis; but not in the oxidation of fatty acids because of the slow rates of thiolysis of β-keto acyl dithioloctanoic acid. The overall effect of these changes in the key enzymic activities is seen in the increased rates of oxidation of glucose and a reduction in fatty acid oxidation in diabetes following lipoic acid administration.

    • How does cobalamin (vitamin B12) enter and traverse mammalian cells?

      Bellur Seetharam

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      This overview is intended to present recent information available on the work done in understanding the mode of entry of cobalamin into and out of mammalian cells. I have focused primarily on the uptake of cobalamin bound to 3 proteins: intrinsic factor, transcobalamin II and R-proteins. Even though the nature of these cobalamin binding proteins, and the receptors involved in the internalization of these proteins is known, a total picture on the intracellular trafficking of cobalamin and the binding proteins is far from complete.

    • Study of Salmonella endotoxin on the changes in lipid-protein interactions of membranes using Arrhenius plots of cetylcholinesterase as a tool

      M K Ray A Mitra B Mukherjee G C Chatterjee

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      Lipopolysaccharides ofSalmonella typhimurium inhibit the activity of acetylcholinesterasein vitro in both synaptosomal and erythrocyte membranes. Arrhenius plots show that the transition temperatures of membrane bound acetylcholinesterase are significantly reduced in the presence of lipopolysaccharides, and the activation energies above and below transition temperature have increased with the lowering of transition temperature. These results indicate that an alteration in the fluidity of the phospholipid layer of the membranes, may be responsible for the membrane-specific effect of lipopoly-saccharides on acetylcholinesterase activity.

    • Definition of physical integrity of synaptosomes and myelosomes by enzyme osmometry

      V Sitaramam M K Janardana Sarma

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      Isotonic requirements for synaptosomes were shown to vary with the concentration of sucrose or mannitol in the isolation medium, as well as with their differential permeability to polyols and ions. The technique of enzyme osmometry, which permits quantitation of the osmotic integrity in a heterogeneous population, was used to defined the osmotic requirements for synaptosomes and myelosomes in a variety of ionic and non-electrolyte media. Important differences, observed in the rank order of permeability of synaptosomal and myelosomal membranes to electrolyte media, were consistent with the known channel density/electrical activity of the corresponding plasma membranes.

    • Cell surface and other morphological changes accompanying growth inhibition in simian virus 40-transformed 3T3 mouse fibroblasts cells induced by glucocorticoids§

      Hasi R Das Robert Baratz Delano V Young

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      A number of morphological changes accompany the G2 blockage caused by glucocorticosteroids in simian virus 40-transformed 3T3 mouse fibroblasts cells. Under phase contrast microscopy dexamethasone-treated cells have darkened and raised nuclear regions with ‘lines’ running over their cytoplasmic areas. They are more resistant to trypsinization and smaller in volume. Since inhibitors of DNA and protein synthesis prevent this ‘glucocorticoid morphology’, the ‘darkening’ may be due to the accumulation of macromolecules within G2-blocked cells and the induction of a protein(s) may be needed for the morphological changes. Colchicine and cytochalasin B do not bring about the glucocorticoid morphology, suggesting that it is not due to a general de-polymerization of microtubules or microfilaments. With scanning electron microscopy treated cells show a great reduction in the amount and a re-organization of microvilli and microplicae. Granules of lead precipitate at the periphery are also clearly evident in transmission electron micrographs. These observations reveal profound morphological alterations, including cell surface changes, induced by glucocorticosteroids.

    • High affinity uptake of L-glutamate and γ-aminobutyric acid inDrosophila melanogaster

      C S Ramarao S R Acharya K S Krishnan U W Kenkare

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      Preparations having properties resembling those of synaptosomes have been isolated from whole fly homogenates ofDrosophila melanogaster using ficoll gradient floatation technique. These have been characterized by marker enzymes and electron microscopy and binding of muscarinic antagenist3H Quinuclidinyl benzilate. An uptake system for neurotransmitter, ã-Aminobutyric acid has been demonstrated in these preparations.

      A high affinity uptake system for L-glutamate has also been studied in these subcellular fractions. This uptake of glutamate is transport into an osmotically sensitive compartment and not due to binding of glutamate to membrane components. The transport of glutamate has an obligatory requirements for either sodium or potassium ions. Kinetic experiments show that two transport systems, withKm values 0.33 X 10-6M and 2.0 X 10-6M, respectively, function in the accumulation of glutamate. ATP stimulates lower affinity transport of glutamate. Inhibition of glutamate uptake by L-aspartate but not by phenylalanine and tyrosine indicates that a common carrier mediates the transport of both glutamate and aspartate. β-N-oxalyl-L-β β-diamino propionic acid and kainic acid, both inhibitors of glutamate transport in mammalian brain preparations, strongly inhibited transport of glutamate inDrosophila preparations

      Comparison with uptake of ã-aminobutyric acid and glutamate in isolated larval brain is presented to show that the synaptosome-like preparations we have isolated are rich in central nervous system derived structures, and presynaptic endings from neuromuscular junctions.

    • Coimmobilization of D-amino acid oxidase and catalase by entrapment ofTrigonopsis variabilis in radiation polymerised Polyacrylamide beads

      Ashwini Deshpande S F D’souza G B Nadkarni

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      Trigonopsis variabilis induced for D-amino acid oxidase and catalase was immobilized by entrapment in Polyacrylamide beads obtained by radiation polymerisation. Permeabilization of the cells was found to be essential for optimal activity of the enzymes in free cells. However, the process of entrapment itself was found to eliminate the permeability barrier of cells immobilized in Polyacrylamide. The two enzymes exhibited a differential response on Polyacrylamide entrapment. Thus, D-amino acid oxidase activity was stabilized to heat inactivation whereas catalase in the same cells showed a destabilization on entrapment in Polyacrylamide. The coimmobilized enzyme preparation showed an operational half life of 7–9 days after which the D-amino acid oxidase activity remained stable at a value 35–40% of that of the initial activity for a study period of 3 weeks. Coimmobilization of MnO2 was not effective in enhancing the operational life of the enzyme preparation.

    • Effect ofcis andtrans unsaturated fatty acids on the transport properties ofSalmonella typhimurium

      J K Deb R Goyal M Chakravorty

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      The transport of α-methyl-D-glucoside and two aminoacids, L-phenylalanine and L-leucine by a temperature sensitive fatty acid requiring mutant ofSalmonella typhimurium was studied under conditions of supplementation withcis or trans-unsaturated fatty acids. The results of such experiments definitely establish a relationship between the fatty acids composition of the membrane and the transport property of the cells. Cells grown in the presence of trans-unsaturated fatty acids cannot transport so efficiently as compared to the cis-unsaturated fatty acid-grown cells except linolelaidic acid, atrans-trans-unsaturated fatty acid. Protein: phospholipid ratio of the membrane also varies significantly under such conditions. The affinity of L-phenylalanine transport carrier for the substrate changes remarkably in cells grown in the presence of differentcis or trans-unsaturated fatty acids and indicate the possible role of membrane lipids in membrane assembly as well as regulation of the activity of L-phenylalanine transport system.

    • Generation of bacteriophage T3 mRNAs by post-transcriptional processing by RNase III

      Hemanta K Majumder Samit ADhya Umadas Maitra

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      The primary transcripts synthesizedin vitro from a T3 DNA template byEscherichia coli RNA polymerase and by T3 phage-specific RNA polymerase have been characterized with regard to cleavage by RNase III and the size of the products of the cleavage reaction have been compared with those ofin vivo T3 RNAs. It has been observed that the large RNA molecule synthesized invitro byEscherichia coli RNA polymerase from the early region of T3 DNA are cleaved at specific sites byEscherichia coli RNase III to produce all the early mRNAs normally observed in T3-infected cells. In contrast, evidence presented here shows that some of the late T3 mRNAs are generated as direct products of transcription of late regions of T3 DNA by T3 RNA polymerase without mediation of RNase III, while many other late T3 mRNAs are formed by RNase III cleavage of two of the high molecular weight T3 RNA polymerase transcripts. Thesein vitro data appear to be in good agreement with the observed sizes of late T3 mRNAs formedin vivo in T3-infected RNase III-deficient and RNaseIII+Escherichia coli cells.

    • Transcriptional specificity after mycobacteriophage I3 infection

      V Nagaraja K P Gopinathan

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      Transcriptional regulation following mycobacteriophage I3 infection has been investigated. For this purpose, RNA polymerase mutants (rif)of host bacterium,Mycobacterium smegmatis have been isolated and characterised. Phage growth inrifs and rifr cells in presence of rifampicin revealed the involvement of host RNA polymerase in phage genome transcription. This was confirmed by studies onin vivo RNA synthesis as well as by direct RNA polymerase assay after phage infection. Significant stimulation in RNA polymerase activity was seen following phage infection. The maximal levels were attained in about 60 min post infection and maintained throughout the phage development period. The stimulation of polymerase activity was most pronounced when the phage DNA was used as the template. RNA polymerases from uninfected and phage-infectedMycobacterium smegmatis have been purified to homogeniety. The enzyme purification was accomplished by a rapid procedure utilising affinity chromatography on rifampicin-Sepharose columns. Subunit structure analysis of the purified RNA polymerase from uninfected and phage-infected cells showed the presence of α,β, β′ and σ subunits similar to the other prokaryotic RNA polymerases. In addition, a polypeptide of 79, 000 daltons was associated with the enzyme after phage infection. The enzymes differed in their properties with respect to template specificity. Phage 13 DNA was the preferred template for the modified RNA polymerase isolated from infected cells which may account for the transcriptional switch required for phage development.

    • Type 1 fimbriation is negatively regulated by cyclic AMP and its receptor proteinvia conjugative plasmid F inEscherichia coli K-12

      Shambhavi Subbarao Nam Prakash A V Sivaprasad Sushil Kumar

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      Expression of fimbriation was studied inEscherichia coli K-12 CA8000 HfrH, and itscya, crp and MS2 resistant mutants. The cells of cya+ crp+ parent strain were observed to be flagellated bacilli, lacking fimbriae, unable to agglutinate erythrocytes and deficient in ability to produce surface pellicle during growth in stationary culture. The cells ofcya andcrp mutants were observed to be cocci or coccobacilli devoid of flagella, having haemagglutinating activity, fimbriated and capable of producing surface pellicle in stationary cultures. The fimbriation and haemagglutinating activities were lower incya mutants grown with cAMP supplementation. Thecya andcrp mutants produced relatively small, smooth and compact colonies consisting mostly of fimbriated cells, like those of earlier described Fimσ mutants. Thecya+ crp+ MS2 resistant mutant produced large sized colonies like those of parent but was deficient in conjugal donor ability. It resembledcya andcrp mutants in haemagglutinating and fimbriation properties. Thecya andcrp mutants have been earlier shown to be deficient in several Tra functions including conjugal donor ability. It is concluded thatEscherichia coli K-12 cells express fimbriation when Tra functions of F-plasmid carried in them are not expressed either due to deficiency of active cAMP-receptor protein complex or mutation in F-plasmid or when F-plasmid is absent.

    • Stabilisation of some of the protein synthesis components in the thermophilic fungus,Humicola lanuginosa

      Anil K Joshi Joseph D Cherayil

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      The thermal stabilities of tRNA from the thermophilic fungus,Humicola lanuginose were compared with that from the mesophilic yeast,Candida utilis, by measuring the increase in the optical density with temperature. tRNAs from both the species were stable in the presence of millimolar quantities of magnesium chloride upto 50°C, the optimum growth temperature of the fungus. Aminoacyl tRNA synthetases were maximally active at 40°C under thein vitro assay conditions. They were fractionated and one species of valine tRNA synthetase was purified to homogeneity. The purified enzyme was protected against inactivation to varying degrees when preincubated with the substrates valine, tRNA and ATP as well as spermine. Protein turnover studies showed that the rate of turnover was higher at higher temperatures. It was concluded from these results that the protein synthesizing machinery of this fungus has no intrinsic stability but it is stabilised by intracellular factors. Higher rate of protein turnover also plays a role for growth at higher temperature.

    • Site-directed mutagenesis to determine essential residues of ribulose-bisphosphate carboxylase ofRhodospirillum rubrum

      Salil K Niyogi Thomas S Soper Robert S Foote Frank W Larimer Richard J Mural Sankar Mitra Eva H Lee Richard Machanoff Fred C Hartman

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      Both Lys-166 and His-291 of ribulosebisphosphate carboxylase/oxygenase fromRhodospirillum rubrum have been implicated as the active-site residue that initiates catalysis. To decide between these two candidates, we resorted to site-directed mutagenesis to replace Lys-166 and His-291 with several amino acids. All 7 of the position-166 mutants tested are severely deficient in carboxylase activity, whereas the alanine and serine mutants at position 291 are ∼40% and ∼18% as active as the native carboxylase, essentially ruling out His-291 in theRhodospirillum rubrum carboxylase (and by inference His-298 in the spinach enzyme) as a catalytically essential residue. The ability of some of the mutant proteins to undergo carbamate formation or to bind either ribulosebisphosphate or a transition-state analogue remains largely unimpaired. This implies that Lys-166 is not required for substrate binding; rather, the results corroborate the earlier postulate that Lys-166 functions as an acid-base group in catalysis or in stabilizing a transition state in the reaction pathway.

    • Purification and some properties of human DNA-O6-methylguanine methyltransferase

      Amy M Boulden Robert S Foote G Scott Fleming Sankar Mitra

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      DNA-O6-methylguanine methyltransferase was purified from the nuclear fraction of fresh human placenta using ammonium sulphate precipitation, gel filtration, affinity chromatography on DNA-cellulose and hydroxyapatite. The methyltransferase preparation was approximately 1–2% pure based on specific activity, and was free of nucleic acids. The protein reacts stoichiometrically with O6-methylguanine in DNA with apparent second-order kinetics. The human methyltransferase has a pH optimum of about 8.5, similar to that of the corresponding rat and mouse proteins. NaCl inhibits the reaction in a concentration-dependent fashion. The human protein, like the rodent andE. coli methyltransferases, needs no cofactor. While lmM MnCl2, lmM spermidine, 5mM MgCl2 and 10 mM EDTA individually do not significantly inhibit the initial rate of reaction, the protein is nearly completely inactive in 5 mM A1Cl3 or FeCl2 or 10 mM spermidine. The initial rate of reaction increases as a function of temperature at least up to 42°. The reaction is inhibited by DNA in a concentration-dependent manner, with single-stranded DNA being more inhibitory than duplex DNA.

    • Autoregulation of gene expression:rho

      Roberta Haber Sankar Adhya

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      Autoregulation of therho gene insures a controlled level of a critical gene product independent of cellular changes. We have investigated the autoregulation ofrho, the gene that encodes the transcription termination factor,rho. In a DNA dependentin vitro coupled transcription-translation system,rho represses its own synthesis, confirming the autoregulatory nature ofrho. srho is believed to perform its negative regulatory role by modulating transcription termination at an early site in the operon.

    • Structural organization of cholera toxin gene and its expression in an environmental non-pathogenic strain ofVibrio cholerae

      Uma Bhattacharyya Amit Ghosh Ranajit K Ghosh

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      Non-pathogenic, environmental strain ofVibrio cholerae, ELTOR Ogawa EW6 carries a copy of the cholera toxin gene in its chromosome. Restriction enzyme digestion followed by Southern blot analysis revealed that the structure of the cholera toxin gene in this organism is different from that found in the virulent strains. The xbaI site which has been found to be conserved in the cholera toxin of the virulent strains examined so far, is absent here. Results of the RNA dot blot analysis indicated that the cholera toxin gene in EW6 is transcribed much less efficiently compared to the cholera toxin gene present in the virulent strainVibrio cholerae classical Inaba 569B.

    • RNase F and 2′,5′-oligoA synthetase activities in mice after poly(I). poly(C) administration

      Krishna Baksi Boris Skurkovich Simon Skurkovich

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      The present study demonstrates the presence of considerable levels of 2′, 5′-oligoA synthetase activity in tissue extracts from mice. The interferon inducer, poly(I) .poly(C) , induced the synthetase activity in all the tissue extractsin vivo. Similarly, a significant amount of endonuclease RNase F activity is found to be present in these tissue extracts. But interferon induction does not seem to have any significant effect on RNase F activity.

    • Histochemical localization of protein-polysaccharides in renal tissue

      S Saraswathi J V Tesoriero N S Vasan

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      The purpose of this study was to investigate the distribution of protein-polysaccharides in the glomerular and non-glomerular regions of the nephron. The techniques used include the digestion of kidney slices with specific polysaccharidases: neuraminidase, hyaluronidase, chondroitinase ABC, and collagenase followed by several cytochemical techniques to identify the glycosaminoglycans and glycoproteins at the light and electron microscope levels. Differential staining of hyaluronic acid and sulphated glycosaminoglycans was accomplished with Alcian Blue at pH 2.5 and pH 0.5, respectively. Sialoproteins were stained with Alcian Blue at pH 2.5. The periodic acid Schiff’s reaction technique was employed for the visualization of collagen. At the electron microscope level the polysaccharides were identified with the periodic acid-chromic acid-silver methenamine reaction. Our results indicated that the major polysaccharide components of the glomerular basement membrane were sialoproteins and collagen, with smaller amounts of hyaluronic acid and various sulphated glycosaminoglycans. Hyaluronidase digestion resulted in partial detachment of epithelial processes from the glomerular basement membrane indicating the hyaluronic acid may have a role in the stability of the attachment of these processes. Tubular basement membranes also contain sialoproteins and sulphated glycosaminoglycans but in considerably lower concentrations than the glomerular basement membrane. Bowman’s capsule appears to contain mostly sulphated glycosaminoglycans and has a lower concentration of sialoproteins and hyaluronic acid.

    • The positional specificities of the oxygenation of linoleic acid catalyzed by two forms of lipoxygenase isolated from Bengal gram (Cicer arietinum)

      Alip Borthakur B Ganesh Bhat Candadai S Ramadoss

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      The products generated from linoleic acid by the two forms of Bengal gram lipoxygenase, BGL1 and BGL2, were analysed by high-performance liquid chromatography using μ-porasil column with isooctane containing 0.5% ethanol as the solvent system. The l3-hydroperoxyoctadecadienoic acid and its 9-isomer which are known to be produced by soybean lipoxygenase-1 and the potato enzyme respectively were used as standards. The results show that BGL1 generated almost exclusively the l3-hydroperoxyoctadecadienoic acid while BGL2 produced both l3-and the 9-isomer in the ratio 21:79. The secondary keto derivatives formed in the BGL2 reaction were also separated by this technique.

    • Interaction of Cibacron Blue F3G-A and Procion Red HE-3B with sheep liver 5,10-methylenetetrahydrofolate reductase

      K Varalakshmi H S Savithri N Appaji Rao

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      Cibacron Blue F3G-A, a probe used to monitor nucleotide binding domains in enzymes, inhibited sheep liver 5,10-methylenetetrahydrofolate reductase competitively with respect to 5-methyltetrahydrofolate and NADPH. TheKi values obtained by kinetic methods and theKd value for the binding of the dye to the enzyme estimated by protein fluorescence quenching were in the range 0.9–1.2 μM. Another triazine dye, Procion Red HE-3B interacted with the enzyme in an essentially similar manner to that observed with Cibacron Blue F3G-A. These results as well as the interaction of the dye with the enzyme monitored by difference spectroscopy and intrinsic protein fluorescence quenching methods indicated that the dye was probably interacting at the active site of the enzyme by binding at a hydrophobic region.

    • Multisubstrate specifics amylase from mushroomTermitomyces clypeatus

      Anil K Ghosh Subhabrata SenGupta

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      An amylase was purified from the culture filtrate ofTermitomyces clypeatus by ammonium sulphate precipitation, DEAE-Sephadex chromatography and gel filtration on Bio-Gel P-200 column. The electrophoretically homogeneous preparation also exhibited hydrolytic activity (in a decreasing order) on amylose, xylan, amylopectin, glycogen, arabinogalactan and arabinoxylan. The enzyme had characteristically endo-hydrolytic activity on all the substrates tested and no xylose, glucose, arabinose or glucuronic acid could be detected even after prolonged enzymatic digestion of the polysaccharides. Interestingly the enzyme had similar pH optima (5.5), temperature optima (55°C), pH stability (pH 3–10) and thermal denaturation kinetics when acted on both starch and xylan (larch wood) .Km values were found to be 2.63 mg/ml for amylase and 6.25 mg/ml for xylanase activity. Hill’s plot also indicated that the enzyme contained a single active site for both activities. Hg2+ was found to be most potent inhibitor. Ca2+, a common activator for amylase activity, appeared to be an inhibitor for this enzyme. Thus it appeared that the enzyme had multisubstrate specificity acting as α-amylase on starch and also acting as xylanase on side chain oligosaccharides of xylan containing α-linked sugars.

    • Effect of N-bromosuccinimide-modification of tyrosine side chains of cardiotoxin II of the Indian cobra on biological activity

      P Shashidharan L K Ramachandran

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      The essential role of tyrosine residue(s) of cardiotoxin II in the biological activity of the toxin was evaluated using N-bromosuccinimide. N-bromosuccinimide effected oxidation of the tyrosine residues in cardiotoxin II with enhancement in absorbance at 260 nm. The influence of various solvent media such as acetate-formate buffer (pH 4.0), 0.01 N H2SO4 (pH 2.0) and Tris-HCl buffer (pH 8.5) on oxidation of tyrosine residues was exa mined. In comparison with 0.01 N H2S O4, acetate-formate buffer could prevent secondary oxidations as revealed by lower consumption of oxidant, N-bromosuccinimide, to achieve oxidation. In Tris-HCl buffer oxidation of tyrosine did not take place effectively. N-iodo-succinimide caused only limited oxidation as evident from minor increase in absorbance at 260 nm. N-chlorosuccinimide was completely ineffective. Oxidation of cardiotoxin II with 3.75 equivalents of N-bromosuccinimide tyrosine residue led to complete loss of lethal activity. However, the derivative retained the ability to protect bacterial protoplasts from lysis in solutions of low tonicity. Unlike cardiotoxin II oxidized with N-chlorosuccinimide (50 equivalents/mol of toxin) which retained lethal activity as well as the ability to protect protoplasts from lysis, performic acid-oxidized toxin had lost both the activities.

    • Differential scanning calorimetric studies of native and freeze-damaged very low density lipoproteins in hen’s egg yolk plasma

      S Mahadevan

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      Lipid thermal transition patterns of the very low density lipoproteins in native and variously treated egg yolk plasma and extracted total very low density lipoproteins lipids have been recorded by differential scanning calorimetry in the temperature range 220–300 K, after lowering the freeze endotherm of free water in the sample with ethylene glycol.

      Three distinguishable patterns of lipid endotherms, designated types 1, 2 and 3 were obtained, respectively, from (i) native very low density lipoproteins in egg yolk plasma, (ii) freeze damaged very low density lipoproteins in gelled egg yolk plasma and (iii) extracted total lipids of very low density lipoproteins dispersed in water. Protein-depleted ‘lipid core’ particles of very low density lipoproteins obtained by exhaustive proteolysis of egg yolk plasma gave type 2 lipid transition pattern suggesting similarities in its lipid association with that of the freeze damaged very low density lipoproteins. Freezing the ‘lipid cores’ of very low density lipoproteins led to phase separation and gave type 3 lipid transition pattern of water-dispersed, phase-separated total very low density lipoprotein lipids. Relative heat uptake of native very low density lipoproteins in egg yolk plasma was about 15% lower than the freeze damaged sample or of the extracted total lipids.

      Treatments which prevented aggregation and gelation of very low density lipoproteins in egg yolk plasma during frozen storage, namely with additives such as glycerol or NaCl, gave subsequent lipid transition pattern intermediate between type 1 and 2, indicating that while very low density lipoprotein aggregation is prevented, additives do not altogether prevent changes in lipid association in these particles.

    • Amphomycin: A tool to study protein N-glycosylation

      Dipak Kumar Banerjee

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      Radio-labelled amphomycin (3H-amphomycin) forms a complex with dolichylmonophosphate in presence of Ca2+. Complex formation has also been documented with retinylmonophosphate and perhydromonoeneretinylmonophosphate. Analysis of the space-filling model suggested both fatty acylated aspartic acid residue at the N-terminus of the lipopeptide and phosphate head group of dolichylmonophosphate are necessary for the complex formation. The binding ability of amphomycin is then utilized to localize dolichylmonophosphate in the microsomal membrane. Studies with microsomal membranes from hen oviduct suggested that dolichylmonophosphate is located in the cytoplasmic side of the membrane.

    • Are the proteinase inhibitory activities in lenticular tissues real?

      S Swaminathan T N Pattabiraman

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      The possibility of proteinase inhibitory activities in lenses measured with synthetic substrates being spurious, due to the effective competition of lens proteins as substrates for the target enzymes, was investigated. Goat, sheep and human cataractous lens proteins were found to be poor substrates for trypsin, elastase and papain compared to casein or bovine serum albumin. Further, the inhibition of elastase catalyzed hydrolysis of succinyl trialanyl p-nitroanilide by casein (500 μg, 53%) and albumin (500 μg, 49%) and of trypsin-catalyzed hydrolysis of benzoyl argininep-nitroanilide by albumin (1 mg, 24%) were significant only at high protein concentrations. These data indicated that the relatively high antielastase and antitryptic activities observed in human cataractous lenses were real. On the other hand, coincident lens protein hydrolysis elevating the true antitryptic and antielastase activities in goat and sheep lenses (that have low activities) could not be ruled out The lesser papain inhibitory activities observed in lenses when albumin was used as substrate compared to activities with benzoyl arginine p-nitroanilide as substrate, appeared to be partly due to lens protein hydrolysis masking the actual inhibition in the former method. Preincubation of goat, sheep and human lens extracts with trypsin for 1 h resulted in complete loss of antitryptic and antielastase activity except in the case of human lens antielastase activity which underwent 50% loss. Papain inhibitory activity was fully stable. Similar papain treatment caused loss of 80–100% of antielastase activity and 45–55% loss of antitryptic activity.

    • Physicochemical ProPerties and binding-site amino acid residues of galactoside-binding Protein of human Placenta

      Madhusoodhan P Nambiar Debkumar Basu P S Appukuttan

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      The galactose-binding lectin of human Placenta has been Purified to homogeneity by affinity chromatograPhy on asialo-fetuin column. The Protein, extractable from the tissue only with lactose is aPParently membrane-bound. Molecular weight determination of native Protein and subunit indicated a dimer of l3.4 kDa subunits. Inhibition of haemagglutination with various saccharides indicate that thiodigalactoside is the best inhibitor followed by lactose. However,P-nitroPhenyl-and 1-O-methyl derivatives of galactose showed that α-anomers inhibited slightly better than β-anomer. Modification of amino acid residues indicated involvement of arginine, lysine and histidine residues at the saccharidebinding site. Cysteine residue modificatioin also abolished haemagglutinating activity. Amino acid comPosition of the lectin is also Presented.

    • Effect of chemical modification on struture and activity of glucoamylase fromAspergillus candidus andRhizopus species

      B C Shenoy A G Appu Rao M R Raghavendra Rao

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      The histidine, tyrosine, tryPtoPhan and carboxyl grouPs in the enzyme glucoamylase fromAsPergillus Candidus andRhizoPus sPecies were modified using grouP sPecific reagents. Treatment of the enzyme with diethylPyrocarbonate resulted in the modification of 0.3 and 1 histidine residues with only a slight loss in activity (10% and 35%) of glucoamylase fromAsPergillus candidus andRhizoPus sPecies resPectively. Modification of tyrosine either by N-acetylimidazole or [I125]-leads to a Partial loss of activity. Under denaturing conditions, maltose did not helP in Protecting the enzyme against tyrosine modification or inactivation. Treatment with 2-Hydroxy-5-nitro benzyl bromide in the Presence of urea, Photooxidation at PH 9.0, N-bromosuccinamide at PH 4.8 resulted in a comPlete loss of activity. However, the results of exPeriments in the Presence of maltose and at PH 4.8 Photooxidation and N-bromosuccinamide treatment suggested the Presence of two tryPtoPhan residues at the active site. There was a comPlete loss of enzyme activity when 10 and 28 carboxyl grouPs fromAsPergillus candidus andRhizoPus, resPectively were modified. Modification in the Presence of substrate maltose, showed at least two carboxyl grouPs were Present at the active site of enzyme and that only one active center seems to be involved in breaking ally 3 tyPes of α-glucosidic linkages namely α-1, 4, α-1, 6 and α-l, 3.

    • Effect of alkaline PH on sunflower 11S Protein

      G Sripad M S Narasinga Rao

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      The effect of alkaline PH on sunflower 1 1S Protein has been monitored by the techniques of ultracentrifugation, Polyacrylamide gel electroPhoresis, turbidity, viscosity, ultraviolet absorPtion sPectra and fluorescence sPectra. Both ultracentrifugation and Polyacrylamide gel electroPhoresis show the dissociation of the Protein with increase in PH. Turbidity values decrease with PH while viscosity increases. With increase in PH absorbance of the Protein solution increases and there is a red shift in the absorPtion maximum. Fluorescence quenching and a red shift in the emission maximum are also observed. Both dissociation and denaturation of the Protein occur. Analysis of turbidity, viscosity and fluorescence data suggests that aPParently denaturation follows dissociation.

    • Resolution of DNA polymerase-α-primase complex and primase free

      Ira Simet Satyajit Ray Subhash Basu

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      DNA Polymerase-α from embryonic chicken brain was resolved on DEAE-cellulose into 3 comPonent activities that remained distinct uPon rechromatograPhy. Product formation by each activity required exogenously added temPlate-Primer DNA, all 4 deoxynucleoside triPhosPhates, and a divalent metal cation. Each form incorPorated [3H]-dTTP or [3H]-dCTP into a high molecular weight Product that was identified as DNA by its chromatograPhic behavior and its sensitivity to DNase. High ionic strength, N-ethylmaleimide, and the Polymerase-α-sPecific inhibitor aPhidicolin inhibited each activity; the aPParentKi value of aPhidicolin was 3.0 μM in each case. Based on these results, the 3 activities were identified as multiPle forms of DNA Polymerase-α . ExPeriments using embryonic chicken brains of various ages indicated that Polymerase-α1, and Polymerase-α3 reached maximal activity in 9-day-old embryos, while Polymerase-α2 activity was elevated at a slightly later develoPmental stage. Using Poly (dC) as temPlate, high Primase activity was detected in Polymerase-α1, fractions.

    • A single form of metallothionein is Present in both heavy metal induced and neonatal chicken liver

      T Chakraborty I B Maiti B B Biswas

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      MultiPlicity of metallothionein and their genes in higher animals are documented extensively in recent literature. In contrast, chicken liver Produced aPParently a single form of metallothionein uPon heavy metal exPosure. This Protein was Purified by gel filtration and ion exchange chromatograPhy and another technique based on heat treatment and acetone fractionation, followed by ion exchange chromatograPhy. In adult uninduced chicken liver the Presence of metallothionein was below the detection limit. But, like mammalian system, chicken liver was found to contain high amount of metallothionein at neonatal stage. This naturally occurring neonatal chicken hePatic metallothionein was Purified and comPared with the heavy metal induced adult hePatic metallothionein. The biochemical and immunobiological comParative analysis of adult and neonatal hePatic metallothionein showed identical characteristics. The neonatal metaltothionein exPressed naturally was a zinc metallothionein and unlike few other mammalian neonatal metallothionein did not contain any coPPer. Metallothionein was undectable in unfertilized eggs, in early embryos, and in Postnatal chicken, from 4 weeks after birth. The highest level of this naturally occurring neonatal metallothionein was found in 1–4 day old neonatal liver, which was about 1.5% of the total cytosolic Protein. This is the first rePorted evidence for the Presence of ontogenically modulated exPression of metallothionein in avian system. Possible biological role of neonatal metallothionein and their cellular interactions has been discussed.

    • Increase in hepatic ubiquinone on administration of diethylhexyl phthalate to the rat

      Nandini Nair C K Ramakrishna Kurup

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      It is shown for the first time that the content of ubiquinone of liver increases (2.5 fold) on dietary administration of the widely-used industrial Plasticizer diethylhexyl Phthalate to the rat. The increase is localized almost entirely in mitochondria in which the concentration of the quinone Per mg Protein is 1.7 times the control. IncorPoration of the radioactive Precursor (acetate) reveals that the biosynthesis of ubiquinone is increased in the livers of Plasticizer-administered animals. The rate of degradation is not altered.

    • Effect of mitogenic factors extracted from fetal lung fibroblasts on the in vitro growth of melanocytes obtained from normal and vitiligo subjects

      Manoj Mojamdar Neelu Puri Abburi Ramaiah

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      The effects of growth factors extracted from a newly established fetal lung fibroblast cell line (PMR-GF) on the melanocytes cultured from the Perilesional and dePigmented skins of vitiligo subjects and from normal healthy donors have been investigated. Melanocytes from normal subjects grown in the Presence of 10 ng/ml of 12-0-tetradecanoyl Phorbol l3-acetate and 10-11 M cholera toxin grew exPonentially immediately after seeding the ePidermal cell susPensions. Exogenous addition of PMR-GF to these cells enhanced their growth rates. The Perilesional skin melanocytes of vitiligo subjects in most cases did not manifest any growth when cultured in the Presence of 12-0-tetradecanoyl Phorbol l3-acetate and cholera toxin. PMR-GF induced a brief burst of growth in these cells after a lag of 15 days. Vitiligo lesions gave rise to a few unPigmented dendritic cells that did not manifest any growth in the Presence or absence of PMR-GF. MorPhologically the Perilesional skin melanocytes of most vitiligo subjects, when cultured in 12-0-tetradecanoyl Phorbol l3-acetate and cholera toxin, aPPeared to be larger and hyPer-melanotic as comPared to those of normal individuals. In the Presence of PMR-GF these melanocytes aPPeared to be normal in size and less hyPermelanotiC. Our results indicate that the melanocytes from vitiligo subjects are defective and thus the basic defect in vitiligo could be with the melanocytes themselves.

    • Glycosaminoglycans in human fetal liver in relation to water and electrolytes

      Chameli Ganguly K L Mukherjee

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      The acidic mucoPolysaccharides secreted into the extracellular sPace are thought to Play many imPortant functions amongst which are binding of water and electrolytes on the Polyanionic glycosaminoglycans. Characteristically these comPonents undergo continuous changes during growth and develoPment of the fetuses. RelationshiPs of the concentrations of glycosaminoglycans to the water and PrinciPal electrolytes at different Periods of gestation were studied in human fetuses. It was found that during growth of the human fetuses there was a Progressive decrease in water, thiocyanate sPace, total sodium content and glycosaminoglycans. However the decrease of glycosaminoglycans was greater than the rate of decrease of the other constituents. Hence mucoPolysaccharides were thought to Play more imPortant roles than just binding of water and cations.

    • Antigenic components of human glioblastoma multiforme and rat C6 glioma using monoclonal antibodies

      Ela Sharma Kulvinder S Kochhar Shail K Sharma

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      With whole U87MG cells used as antigenic stimulant, two clones 1A5G6 and 1D3A3 secreted monoclonal antibodies which gave intense staining in monolayer cultures of the cells as ascertained by indirect immunofluorescence. Antibodies from clone 1A5G6 stained both the cytoplasm and the processes, and that from clone 1D3A3 stained only the cytoplasm and not the processes. 1A5G6 elicited no cross-reactivity towards human fetal and adult brain and lungs, liver, kidney or spleen, mouse neuroblastoma and melanoma, rat C6 glioma, neuroblastoma X glioma hybrid and normal rat kidney cells. It gave 58–60% cross reactivity with the human neuroblastoma and T-cell leukemia cells. The antigenic comPonent has been identified to be a membrane protein of molecular weight 25–30 kilodaltons by immunoblotting. Using C6 glioma cells as antigenic stimulant 19 clones which were positive for C6 glioma cells, but negative for rat liver cells as inferred by indirect immunofluorescence were selected. Antibodies secreted by all these gave positive reaction towards normal rat kidney and fetal rat kidney cells in culture. Distinct identity of these clones were ascertained by discernible staining patterns in indirect immunofluorescence on C6 glioma cells.

    • Scavenging of superoxide radical by ascorbic acid

      Anuradha Nandi I B Chatterjee

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      Using acetaldehyde and xanthine oxidase as the source of suPeroxide radical, the second order rate constant for the reaction between ascorbic acid and superoxide radical was estimated to be 8.2 X 107 M-1 s-1. In rats, the average tissue concentration of ascorbic acid was of the order of 10-3 M and that of superoxide dismutase was of the order of 10-6 M. So, taking together both the rate constants and the tissue concentrations, the efficacy of ascorbic acid for scavenging superoxide radical in animal tissues appears to be better than that of suPeroxide dismutase. The significance of ascorbic acid as a scavenger of superoxide radical has been discussed from the point of view of the evolution of ascorbic acid synthesizing capacity of terrestrial vertebrates.

    • Alteration of the acyl chain composition of free fatty acids, acyl coenzyme A and other liPids by dietary polyunsaturated fats

      M Renuka Prasad Brenda Culp William E M Lands

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      Dietary alterations were used to demonstrate selective handling of fatty acids during their redistributionin vivo. Differences in the mol Per cent of individual acyl chains in the non-esterified fatty acid, acyl-coenzyme A and PhosPholiPid fractions reflected a result of relative Precursor abundance combined with enzymic selectivities. Selective distributions were observed in the utilization of individual acyl chains between 16:0 and 18:0, 18:1 and 18:2, and among 20:3, 20:4 and 20:5, 22:6 by ligase(s), hydrolase(s) and acyl-transferases.

      The variations in the mol Per cent of linoleate Present in the acyl-coenzyme A fraction of liver relative to that in the non-esterified fatty acids suggested anin vivo regulation of the level of linoleoyl-coenzyme A that influenced the synthesis of both arachidonoyl-coenzyme A and lipids.

      The greater abundance of eicosaPentaenoic acid in the free fatty acid fraction relative to that in the acyl-coenzyme A fraction may increase the ability of dietary 20: 5n-3 to be an effective inhibitor of the synthesis of Prostaglandins derived from 20:4n-6.

    • Importance of determining viability ofMycobacterium leprae inside macrophages—anin vitro method using uracil

      Sunanda Vejare P R Mahadevan

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      It has been demonstrated thatMycobacterium leprae, are caPable of taking uP uracil and incorPorating it into trichloroacetic acid-insoluble materials, both as free susPension of bacteria, as well as when they are inside the macrophages, a host cell for theirin vivo survival. Same amount of bacteria show better incorPoration inside macroPhages than as free bacterial susPension. Both tyPes of incorPoration are inhibited by rifamPicin an antileProsy drug and an RNA synthesis inhibitor. Thus uracil uPtake byMycobacterium lePrae inside macroPhages has been used for standardising a raPidin vitro viability assay for the leProsy causing bacteria.

    • In vitro effects of gossypol on testicular lactic dehydrogenase-X and other dehydrogenases

      N Giridharan Mahtab S Bamji M N Madhyastha

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      Thein vitro inhibition of several rat testis dehydrogenases by gossyPol was examined. Inclusion of the coenzyme (substrate for NADP+-isocitrate dehydrogenase) in the Preincubation mixture containing the enzyme and gossyPol, Protected the enzymes against inhibition by gossyPol. Lactic dehydrogenase-X was amongst the least Protected enzymes. This, couPled with its lowKi for gossyPol makes it one of the most vulnerable target enzymesin vivo for gossyPol action.

      The inhibition kinetics for lactic dehydrogenase-X were comPetitive when NADH was Present during Preincubation, but non-comPetitive when the coenzyme was excluded during Preincubation. In the latter condition, the enzyme seems to undergo Progressive inactivation with time causing a nonreversible tyPe of inhibition.

    • Conformational and ion-binding properties of cyclolinopeptide A isolated from linseed

      D Chatterji M B Sankaram D Balasubramanian

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      The conformation of the cyclic nonaPePtide from linseed, cyclolinoPePtide A in methanol and in acetonitrile has been elucidated by one-and two-dimensional nuclear magnetic resonance. The molecule is folded in a β-turn conformation. CyclolinoPePtide A interacts and weakly comPlexes with Tb3+ (a Ca2+ mimic ion) with the metal ion Positioned Proximally to the Phe residue, but with no substantial structural alteration uPon metal binding. CyclolinoPePtide A is also seen to aid the translocation of Pr3+ (another Ca2+ mimic) across unilamellar liPosomes. However, cyclolinoPePtide A does not Phase transfer or act as an ionoPhore of calcium ion myself. ExPeriments using lanthanide ions thus do not necessarily indicate any ionoPhoretic ability of the comPlexone towards calcium ions.

    • Spectroscopic studies on the interaction of bilirubin with symmetrical alkyl diamines

      Kasturi Lahiri Puranam P Balaram

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      The interactions of symmetrical alkyldiamines with bilirubin-IX α have been examined in dichloromethane and dioxane solutions, by visible region difference sPectroscoPy and florescence methods. In dioxane solutions a clear difference is observed between the comPlexes of the shorter chain diamines (number of sPacer methylene grouPs (n ≤4) ) and the longer chain diamines (n ≥6) . The variations in sPectral features with diamine chain length are less Pronounced in dichloromethane. The sPectroscoPic results are consistent with the occurrence of distinct bilirubin conformations dePending uPon the solvent and the geometry of the interacting recePtor. Based on molecular modelling two conformations are ProPosed. A ‘ridge-tile’ model similar to that observed in crystals is favoured for binding to the longer diamines, while a ‘quasi-cyclic’ structure is Preferred for interaction with the short chain diamines.

    • Reactivity of glycoconjugate in membrane system II: Can a neutral glycolipid function as lectin receptor in the presence of gangliosides in plasma membrane?

      S K Podder A Chakraborti K Vijayalakshmi P Lalit Kumar Singh

      More Details Abstract Fulltext PDF

      To examine how surface Potential controls the reactivity of glycoconjugates at cell surface, the interaction of galactose-sPecific lectinse.g. peanut agglutinin,Ricinus cummunis agglutinin with liPosomes bearing asialo GM1 were studied in the Presence of varying amount of ganglioside mixture, GMn. The Presence of 5% GMn causes comPlete slowing down of PreciPitin reaction and thereby make carbohydrate moiety of asialo GM1 comPletely inaccessiblei.e. ‘cryPtic’. In contrast the Presence of 1–2% GMn enhances the aPParent rate and amPlitude of the PreciPitin reaction as surface Potential becomes more negative. The relevance of the findings has been discussed in relation to the exPression and involvement of the cell-surface sialic acid residues during develoPment and differentiation.

    • Mechanism of protein synthesis inhibition by vaccinia viral core and reversal of this inhibition by reticulocyte peptide chain initiation factors

      Debopam Chakrabarti Kolluru V A Ramaiah Ananda L Roy Milan Bagchi Naba K Gupta

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      Vaccinia viral core inhibits protein synthesis in heme-supplemented reticulocyte lysate. A reticulocyte cell suPernatant factor, which reversed Protein synthesis inhibition in heme-deficient reticulocyte lysate also reversed vaccinia viral core induced Protein synthesis inhibition in heme-suPPlemented reticulocyte lysate. Significant inhibition reversal activity was also observed with a partially purified eukaryotic initiation factor-2 PreParation and this activity was lost uPon further Purification of eukaryotic initiation factor-2.The ribosomal salt-wash factor Co-eukaryotic initiation factor-2 which like reticulocyte suPernatant factor contains guanine nucleotide exchange factor activity, was comPletely inactive. Vaccinia viral core induced detectable level of eukaryotic initiation factor-2 α-subunit phosphorylation when incubated in the heme-supplemented reticulocyte lysate. This lysate preparation contains guanine nucleotide exchange factor activity. However, when the same reticulocyte lysate was previously incubated with the vaccinia viral core, the guanine nucleotide exchange factor activity during subsequent incubation was almost comPletely inhibited.

    • Effect of proteolytic digestion on the function of vesicular stomatitis virus ribonucleoprotein complex

      A K Banerjee J Roy D J Chattopadhyay

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      The nucleocaPsid Protein (49 Kd) of vesicular stomatitis virus is tightly bound to the genome rendering the latter transcriPtionally comPetent. Controlled digestion with chymotryPsin removed a 12 Kd PePtide from the comPlex. The resulting comPlex failed to serve as temPlate for genome transcriPtionin vitro when the Polymerase comPonents L and NS Proteins were added. A temPlate-associated Protein kinase activity was also lost uPon chymotryPsin treatment. However, the cleaved nucleocaPsid Protein (37 Kd) was still caPable of binding tightly with the genome temPlate and retained the ePitoPe recognized by a monoclonal antibody. These results suggest that the nucleocaPsid Protein Possesses seParate domains that mediate binding to Polymerase comPlex and maintain the structural integrity of the template.

    • Role of B-ring of colchicine in its binding to Zn(II)-induced tubulin-sheets

      Asok Banerjee Sankar N Maity Sukla Ray Chaudhuri B Bhattacharyya

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      Colchicine-tubulin dimer comPlex, a Potent inhibitor of normal microtubule assembly undergoes extensive self-assembly in the Presence of 1 X 10-4 M zinc sulPhate. Polymers assembled from colchicine-tubulin dimer comPlexes are sensitive to cold.

      Although colchicine can be accomodated within the Polymeric structure, the drug cannot bind to tubulin subunits in the intact Polymers. This is evidenced by the fact that (a) the colchicine binding activity of tubulin is lost when allowed to Polymerize with zinc sulPhate, (b) the loss in colchicine binding could be Prevented by Preincubation of tubulin with 1 X 10-3 M CaCl2 or 1 X 10-5 M vinblastine sulPhate and finally (c) no loss in colchicine binding activity is found when tubulin is kePt at a concentration far below the critical concentration for Polymerization. Unlike colchicine, its B-ring analogues desacetamido colchicine (devoid of the B-ring subtituent) and 2-methoxy-5-(2′, 3′, 4′-trimethoxyPhenyl) troPone (devoid of the B-ring) can bind to tubulin subunits in the intact Polymers.

      Thus we conclude that the colchicine binding domain on the tubulin molecule is mostly (if not comPletely) exPosed in the Zn(II) -induced Polymers and the B-ring substituent Plays a major role in determining the binding ability of a colchicine analogue to tubulin in the intact Zn(II) -induced sheets.

    • Binding of 4-methyl umbelliferyl-α-D-glucoPyranoside to Vicia faba lectin: Fluorescence-quenching studies

      Pradip K Datta Pranab S Basu Tapash k Datta

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      On binding toVicia faba lectin, the fluorescence of 4-methylumbelliferyl-α-D-glucoPyranoside was quantitatively quenched showing that the interaction of 4-methylumbelliferyl-α-D-glucoPyranoside took Place in a binding environment. The binding of the fluorescent sugar was saccharide sPecific as evidenced by the reversal of 4-methylumbelliferyl-α-D-glucoPyranoside fluorescence quenching by D-fructose. The association constant,Ka, values for the 4-methylumbelliferyl-α-D-glucoPyranoside was determined by comPetition study emPloying reversal of fluorescence quenching of 4-methylumbelliferyl-α-D-glucoPyranoside by D-fructose. TheKa value obtained for D-fructose was 1.07 ±0.03 X 104 M-1 and for 4-methylumbelliferyl-α-D-glucoPyranoside was 1.60 ±0.05 X 104 M-1 at 15°C. TheKa values of 2.51 ±0.06 X 104M-1, l.26 ±0.02 X 104 M-1 and 0.56 ±0.01 X 104M-1, resPectively at 10°, 20° and 30°C were obtained from the ChiPman equation. The relative fluorescence quenching, ΔFa, at infinite concentration of the free saccharide sites ofVicia faba lectin [P′] was 93.5% at 30°C and the binding constant for 4-methylumbelliferyl-α-D-glucoPyranoside lectin interaction as derived by Yank and Hanaguchi equation was 0.63 ±0.01 X 104M-1.

    • Abnormal erythrocyte membrane phospholipid organisation in chronic myeloid leukaemia

      A Kumar S Daniel S S Agarwal C M Gupta

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      The membrane phospholipid organisation in the red cells of humans suffering from chronic myeloid leukaemia has been analysed using the amino-group labelling reagent trinitrobenzenesulphonic acid and the fluid-sensing fluorophore, Merocyanine 540. Unlike the normal human erythrocytes, trinitrobenzenesulphonic acid in intact chronic myeloid leukaemia erythrocytes modified about 30% phosphatidylserine, under controlled conditions. Also, the chronic myeloid laukaemia red cells, but not the normal cells, were found to bind the fluorescent dye Merocyanine 540. These results demonstrate that loss of the transmembrane phospholipid asymmetry in chronic myeloid leukaemia erythrocytes is accompanied by an enhancement in the outer surface fluidity and, therefore, suggest that the red cells membrane phase-state asymmetry originates probably from the asymmetric arrangements of phospholipids across the membrane bilayer.

    • Immobilization ofKluyvera citrophila penicillins acylase on controlled-pore ceramics

      A M Bodhe C Sivaraman

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      Penicillin acylase was purified fromKluyvera citrophila and immobilized on glutaraldehyde derivatives of silanized controlled-pore ceramics. The behaviour of the enzyme attached to TiO2, Al2O3 and SiO2 in the hydrolytic reaction are compared with that of the native enzyme as well as of the enzyme bound to CNBr-activated Sepharose 4B. The enzyme immobilized on TiO2 shows an efficiency of about 95% on the basis of protein bound. The penicillin acylase attached to SiO2, unlike the enzyme immobilized on TiO2, Al2O3 and Sepharose looses activity markedly in every cycle of use.

    • Conformational change of L7/L12 stalk in the different functional states of 50S ribosomes

      Debabrata Dash Subodh Mahanti Debi P Burma

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      Conformational change of 50S ribosomes takes place during protein synthesis. The primary change is most likely in the secondary or tertiary structure of rRNA in the L7/L12 stalk region. In order to throw further light on this conformational change, the change in fluorescence of tight couple 50S ribosomes on conversion to loose couple 50S ribosomes containing 5-(iodoacetamido ethyl)-aminonaphthalene-l-sulphonic acid-labelled L7/L12, following the treatment with elongation factor-G and 5′-guanylyl methylene diphosphate was measured. It was enhanced in agreement with the results reported earlier. Further, the quenching of fluorescence of 50S ribosomes containing 5-(iodoacetamido ethyl)-aminonaphthalene-1-sulphonic acid-labelled L7/L12 by acrylamide was studied. The quenching is more in case of loose couples. On conversion of loose couple 50S ribosomes to tight couple ones the quenching becomes less whereas the reverse happens on conversion of tight couple 70S ribosomes to loose couples. These results indicate the conformational change of L7/L12 stalk in the different functional states of 50S ribosomes.

    • Arginine decarboxylase is a component activity of the multifunctional enzyme putrescine synthase in cucumber seedlings

      G L Prasad P R Adiga

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      A homogenous PreParation of Putrescine synthase, the versatile multifunctional enzyme involved in agmatine →Putrescine conversion inCucumis sativus was found to catalyze enzymatic decarboxylation of arginine also. Similarly, the Purified arginine decarboxylase mediated the comPonent as well as the comPlete set of couPled reactions harboured by Putrescine synthase. Both the enzyme PreParations exhibited identical electroPhoretic and chromatograPhic behaviour and were immunologically indistinguishable. All the enzymic activities are stabilized concurrently by feeding arginine to the intact seedlings. Therefore, it is concluded that the multifunctional Putrescine synthase inCucumis sativus seedlings also harbours arginine decarboxylase activity unlike its counterPart inLathyrus sativus.

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