01733nas a2200229 4500008004100000022001400041245015100055210006900206260007900275300001000354490000700364520082100371653002501192653002201217653002601239653003201265100002101297700002201318700002001340700001901360856012401379 2006 eng d a0141-022900aStructural and active site modification studies implicate Glu, Trp and Arg in the activity of xylanase from alkalophilic Bacillus sp (NCL 87-6-10)0 aStructural and active site modification studies implicate Glu Tr a360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USAbELSEVIER SCIENCE INCcJUN a67-730 v393 a

Structural studies and residue modification using group specific reagents were used to ascertain the role of different functional groups in xylanase from alkalophilic Bacillus sp. (NCL 87-6-10). Treatment with N-bromosuccinimide resulted in fast enzyme inactivation. Reaction with Woodward's reagent K resulted in initial fast followed by slower inactivation. In both cases enzyme was protected against inactivation by the substrate, xylan. The reaction of the enzyme with phenylglyoxal has revealed one essential arginine residue at the active site. The three-dimensional structural analysis of the xylanase at 2.8 angstrom resolution also implicates involvement of Trp, and Arg residues and carboxylate groups in the binding of substrate and in the catalysis of xylanase. (c) 2005 Published by Elsevier Inc.

10aactive-site residues10aalkaline xylanase10aChemical modification10athree-dimensional structure1 aBalakrishnan, H.1 aSatyanarayana, L.1 aGaikwad, S., M.1 aSuresh, C., G. uhttps://library.ncl.res.in/content/structural-and-active-site-modification-studies-implicate-glu-trp-and-arg-activity-002249nas a2200253 4500008004100000022001400041245019300055210006900248260007900317300001400396490000700410520123900417653001601656653002401672653003201696653001601728653002601744653001101770653001501781100001701796700002601813700002601839856013001865 2007 eng d a0141-022900aActive site directed chemical modification of alpha-galactosidase from bacillus stearothermophilus (NCIM 5146): involvement of lysine, tryptophan and carboxylate residues in catalytic site0 aActive site directed chemical modification of alphagalactosidase a360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USAbELSEVIER SCIENCE INCcAPR a1312-13200 v403 a

The catalytic amino acid residues of the extracellular a-galactosidase (alpha-D-galactoside galactohydrolase; EC 3.2.1.22) from Bacillus stearothermophilus NCIM 5146 were investigated by pH dependence and chemical modification studies. These results suggested that carboxylate and a lysine residue take part in catalysis and only lysine residues were essential for substrate binding. Carbodiimide mediated chemical modification of the enzyme also supported that a carboxylate residue located in the active site act as a nucleophile base in substrate cleavage. Acylation and reductive methylation of lysine residues by acetic, citraconic anhydride and sodium borohydride suggested that four protonated lysine residues carrying positive charge on its epsilon-amino group provides the positive charge density for binding of the substrate. Additionally four tryptophan residues also found near to the active site and in a moderately hydrophobic environment. Kinetic and thermal inactivation study of modified enzyme indicated that these tryptophan residues might have a role in the catalytic site as well as in the thermal stabilization of active site conformation at higher temperature. (c) 2006 Elsevier Inc. All rights reserved.

10aActive site10aalpha-galactosidase10aBacillus stearothermophilus10acarboxylate10aChemical modification10alysine10aTryptophan1 aGote, M., M.1 aKhan, Mohammad, Islam1 aKhire, Jayant, Malhar uhttps://library.ncl.res.in/content/active-site-directed-chemical-modification-alpha-galactosidase-bacillus-stearothermophilus02163nas a2200253 4500008004100000022001400041245013100055210006900186260011700255300001000372490000600382520116900388653001601557653002201573653002601595653002701621653001501648100002401663700002001687700002601707700003101733700001501764856013001779 2009 eng d a0973-626300aInteraction of alpha-mannosidase from aspergillus fischeri with glycosidase inhibitors, metal ions and group specific reagents0 aInteraction of alphamannosidase from aspergillus fischeri with g aSECTOR A-80, SCHEME NO 54, VIJAY NAGAR, A B ROAD, INDORE, 452 010 MP, INDIAbRESEARCH JOURNAL BIOTECHNOLOGYcNOV a39-480 v43 a

As an initial step towards using alpha-mannosidase as a target against anticancer drugs, inhibition studies of a model enzyme, class II alpha-mannosidase from Aspergillus fischeri in presence of polyhydroxy piperidine derived glycosidase inhibitors, metal ions and amino acid specific reagents were carried out to reveal the sensitivity of the enzyme. Three of the derivatives (Compound 20, 32 and 39)(11) showed competitive inhibition (K(i) =45, 48 and 235 mu M) and the binding of the inhibitors to the enzyme was entropically driven. Among the metal ions checked, Cu(++) (K(i) = 21nm) and Se(++) ions (K(i) = 32 mu M) showed noncompetitive and Co(++) (K(i) = 1.195 mM) showed competitive inhibition of the enzyme activity with insignificant change in the secondary structure of the protein. The above studies exhibit the Potential of the enzyme in studying anticancer drugs. Treatment of the enzyme with group specific reagents showed the presence of carboxylate, Arg and Cys at the active site. Substrate protection studies and kinetics of the modified enzyme confirmed the above results. Trp and His at the active site were observed to be in proximity.

10aactive-site10aalpha-Mannosidase10aChemical modification10aGlycosidase inhibitors10ametal ions1 aShashidhara, K., S.1 aGaikwad, S., M.1 aKhan, Mohammad, Islam1 aBharadwaj, Kishor, Chandra1 aPandey, G. uhttps://library.ncl.res.in/content/interaction-alpha-mannosidase-aspergillus-fischeri-glycosidase-inhibitors-metal-ions-and-001934nas a2200229 4500008004100000022001400041245014900055210006900204260009700273300001200370490000800382520099300390653002101383653002601404653002201430653002801452653002801480100002701508700001301535700002601548856013001574 2009 eng d a0944-501300aPurification and characterization of putative alkaline [Ni-Fe] hydrogenase from unicellular marine green alga, tetraselmis kochinensis NCIM 16050 aPurification and characterization of putative alkaline NiFe hydr aOFFICE JENA, P O BOX 100537, 07705 JENA, GERMANYbELSEVIER GMBH, URBAN & FISCHER VERLAGcFEB a131-1370 v1643 a

Hydrogenase enzyme from the unicellular marine green alga Tetraselmis kochinensis NCIM 1605 was purified 467 fold to homogeneity. The molecular weight was estimated to be similar to 89kDa by SDS-PAGE. This enzyme consists of two subunits with molecular masses of similar to 70 and similar to 19 kDa. The hydrogenase was found to contain 10 g atoms of Fe and 1 g of atom of Ni per mote of protein. The specific activity of hydrogen evolution was 50 mu mol H-2/mg/h of enzyme using reduced methyl viologen as an electron donor. This hydrogenase enzyme has pl value similar to 9.6 representing its alkaline nature. The absorption spectrum of the hydrogenase enzyme showed an absorption peak at 425 nm indicating that the enzyme had iron-sulfur clusters. The total of 16 cysteine residues were found per mote of enzyme under the denaturing condition and 20 cysteine residues in reduced denatured enzyme indicating that it has two disulfide bridges. (C) 2007 Published by Elsevier GmbH.

10aCharacterization10aChemical modification10aNi-Fe hydrogenase10aTetraselmis kochinensis10aUnicellular green algae1 aBhosale, Siddharth, H.1 aPant, A.1 aKhan, Mohammad, Islam uhttps://library.ncl.res.in/content/purification-and-characterization-putative-alkaline-ni-fe-hydrogenase-unicellular-marine-002268nas a2200241 4500008004100000022001400041245014300055210006900198260007500267300001200342490000700354520137800361653002601739653001701765653001301782653001101795653001401806653001801820100001601838700001701854700002601871856012901897 2010 eng d a1053-050900aSteady state and time resolved fluorescence quenching and chemical modification studies of a lectin from endophytic fungus fusarium solani0 aSteady state and time resolved fluorescence quenching and chemic a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGER/PLENUM PUBLISHERScJAN a305-3130 v203 a

The solute quenching studies of a lectin from endophytic fungus Fusarium solani were carried out using different quenchers such as acrylamide, succinimide, potassium iodide and cesium chloride. The lectin showed emission maximum at 348 nm indicating relative exposure of tryptophan. The quenchable fraction of the fluorophore was 100% with acrylamide, whereas it was only 50% with succinimide. The ionic quenchers iodide and cesium showed opposite effects at different pH. In the case of cesium, raising the pH resulted in increased quenching and accessibility of typtophan residue, while the iodide showed just opposite effect. These studies showed that the single tryptophan residue of the lectin (per monomer) is relatively exposed, and might be in the vicinity of positively charged amino acid residues. Various amino acids of the F. solani lectin were modified using different reagents to obtain information about the hemagglutinating site. The chemical modification studies suggested tyrosine residues can be modified using N-acetylimidazole, which results in complete loss of hemagglutination activity of the lectin. Kinetics of chemical modification suggested involvement of only 2 tyrosine residues. Modification of arginine, cysteine, histidine, lysine, aspartate, glutamate and tryptophan did not result in loss of hemagglutinating activity of the lectin.

10aChemical modification10afluorescence10aFusarium10aLectin10aQuenching10aTime-resolved1 aKhan, Feroz1 aAhmad, Absar1 aKhan, Mohammad, Islam uhttps://library.ncl.res.in/content/steady-state-and-time-resolved-fluorescence-quenching-and-chemical-modification-studies-002183nas a2200289 4500008004100000022001400041245009500055210006900150260007300219300001000292490000700302520114300309653002601452653003001478653002401508653002201532653003001554653002501584100002301609700001801632700003201650700002301682700001801705700002501723700002701748856011801775 2013 eng d a0141-813000aProbing the active site of cinnamoyl CoA reductase 1 (Ll-CCRH1) from Leucaena leucocephala0 aProbing the active site of cinnamoyl CoA reductase 1 LlCCRH1 fro aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcSEP a33-380 v603 a

Lack of three dimensional crystal structure of cinnamoyl CoA reductase (CCR) limits its detailed active site characterization studies. Putative active site residues involved in the substrate/NADPH binding and catalysis for Leucaena leucocephala CCR (Ll-CCRH1; GenBank: DQ986907) were identified by amino acid sequence alignment and homology modeling. Putative active site residues and proximal H215 were subjected for site directed mutagenesis, and mutated enzymes were expressed, purified and assayed to confirm their functional roles. Mutagenesis of S136, Y170 and K174 showed complete loss of activity, indicating their pivotal roles in catalysis. Mutant S212G exhibited the catalytic efficiencies less than 10% of wild type, showing its indirect involvement in substrate binding or catalysis. R51G, D77G, F30V and I31N double mutants showed significant changes in K-m values, specifying their roles in substrate binding. Finally, chemical modification and substrate protection studies corroborated the presence Ser, Tyr, Lys, Arg and carboxylate group at the active site of Ll-CCRH1. (c) 2013 Elsevier B.V. All rights reserved.

10aChemical modification10aCinnamoyl CoA reductase 110aDocking simulations10ahomology modeling10aSite directed mutagenesis10aSubstrate protection1 aSonawane, Prashant1 aPatel, Krunal1 aVishwakarma, Rishi, Kishore1 aSrivastava, Sameer1 aSingh, Somesh1 aGaikwad, Sushama, M.1 aKhan, Bashir, Mohammad uhttps://library.ncl.res.in/content/probing-active-site-cinnamoyl-coa-reductase-1-ll-ccrh1-leucaena-leucocephala-002756nas a2200241 4500008004100000022001400041245012900055210006900184260005700253300001400310490000800324520187300332653002402205653002602229653002002255653001902275653001602294653001802310100002002328700001902348700001902367856012802386 2015 eng d a0032-093500aCrystal structure of a plant albumin from cicer arietinum (chickpea) possessing hemopexin fold and hemagglutination activity0 aCrystal structure of a plant albumin from cicer arietinum chickp a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcMAY a1061-10730 v2413 a

Crystal structure of a reported PA2 albumin from Cicer arietinum shows that it belongs to hemopexin fold family, has four beta-propeller motifs and possesses hemagglutination activity, making it different from known legume lectins. A plant albumin (PA2) from Cicer arietinum, presumably a lectin (CAL) owing to its hemagglutination activity which is inhibited by complex sugars as well as glycoproteins such as fetuin, desialylated fetuin and fibrinogen. The three-dimensional structure of this homodimeric protein has been determined using X-ray crystallography at 2.2 in two crystal forms: orthorhombic (P2(1)2(1)2) and trigonal (P3). The structure determined using molecular replacement method and refined in orthorhombic crystal form reached R-factors R (free) 22.6 % and R (work) 18.2 % and in trigonal form had 22.3 and 17.9 % in the resolution range of 20.0-2.2 and 35.3-2.2 , respectively. Interestingly, unlike the known legume lectin fold, the structure of this homodimeric hemagglutinin belonged to hemopexin fold that consisted of four-bladed beta-propeller architecture. Each subunit has a central cavity forming a channel, inside of which is lined with hydrophobic residues. The channel also bears binding sites for ligands such as calcium, sodium and chloride ions, iodine atom in the case of iodine derivative and water molecules. However, none of these ligands seem important for the sugar recognition. No monosaccharide sugar specificity could be detected using hemagglutination inhibition. Chemical modification studies identified a potential sugar-binding site per subunit molecule. Comparison of C-alpha atom positions in subunit structures showed that the deviations between the two crystal forms were more with respect to blades I and IV. Differences also existed between subunits in two forms in terms of type and site of ligand binding.

10aBeta-propeller fold10aChemical modification10aChickpea lectin10aComplex sugars10aPA2 albumin10aSugar binding1 aSharma, Urvashi1 aKatre, Uma, V.1 aSuresh, C., G. uhttps://library.ncl.res.in/content/crystal-structure-plant-albumin-cicer-arietinum-chickpea-possessing-hemopexin-fold-and-002858nas a2200265 4500008004100000022001400041245013400055210006900189260000800258300001200266490000800278520193200286653002302218653002602241653002002267653002402287653002602311100002502337700001802362700000502380700002202385700003002407700002802437856012702465 2019 eng d a0014-305700aAromatic polyesters containing pendant azido groups: synthesis, characterization, chemical modification and thermal cross-linking0 aAromatic polyesters containing pendant azido groups synthesis ch cJUL a180-1890 v1163 a

A partially bio-based bisphenol containing pendant azido group viz., 4,4'-(5-azidopentane-2,2-diyl) diphenol (AZBPA) was synthesized starting from 4,4'-bis (4-hydroxyphenyl) pentanoic acid. AZBPA was reacted with isophthaloyl chloride (IPC), terephthaloyl chloride (TPC) and a mixture of IPC/TPC (50:50 mol%) by phase transfer-catalyzed interfacial polycondensation route to obtain aromatic polyesters containing pendant azido groups. Copolyesters containing pendant azido groups were also synthesized by polycondensation of different molar proportions of AZBPA and commercially available 4,4'-(1-phenylethane-1,1-diyl) diphenol (BPA-AP) with IPC. Inherent viscosities and number average molecular weights of (co)polyesters were in the range 0.85-1.64 dL/g and 58,900-190,400, respectively, indicating the formation of reasonably high molecular weight polymers. Tough, transparent, and flexible films could be cast from chloroform solutions of these polyesters. X-Ray diffraction analysis showed that (co)polyesters were amorphous in nature. (Co)polyesters were characterized using FT-IR, H-1 NMR spectroscopy, XRD, TGA and DSC analysis. The chemical modification of a representative copolyester containing pendant azido groups was carried out quantitatively using copper-catalyzed azide-alkyne cycloaddition (CuAAC) with two alkynes viz., phenyl acetylene (PA) and ethynyl-4-nitrobenzene (ENB). Additionally, (co)polyesters containing pendant azido groups were thermally cross-linked (170 degrees C/12 h) leading to the formation of network structures based on azide to nitrene decomposition and subsequent reactions on polyester backbone. The selected cross-linked polyesters were characterized by stress-strain measurements. The cross-linked polymers exhibited higher tensile strength and Young's modulus and lower % elongation at break compared to corresponding pristine polyesters containing pendant azido groups.

10aAromatic polyester10aChemical modification10aClick chemistry10aPendant azido group10aThermal cross-linking1 aNagane, Samadhan, S.1 aVerma, Savita1 a1 aSane, Prakash, S.1 aDhanmane, Sushilkumar, A.1 aWadgaonkar, Prakash, P. uhttps://library.ncl.res.in/content/aromatic-polyesters-containing-pendant-azido-groups-synthesis-characterization-chemical02465nas a2200253 4500008004100000022001400041245010100055210006900156260000900225300001400234490000700248520158800255653002701843653001601870653002001886653002601906100002201932700002501954700002101979700002502000700002602025700002802051856013202079 2019 eng d a0887-624X00aNew cardo bisphenol monomer containing pendant azido group and the resulting aromatic polyesters0 aNew cardo bisphenol monomer containing pendant azido group and t cJUL  a1516-15260 v573 a

Expanding on our strategy to synthesize aromatic step-growth polymers containing pendant clickable azido groups via functional monomer approach, we have now designed and synthesized a new cardo bisphenol, viz., 2-(2-azidoethyl)-3, 3-bis(4-hydroxyphenyl) isoindolin-1-one (PPH-N-3). PPH-N-3 was conveniently synthesized starting from commercially available phenolphthalein by a three-step route in an overall yield of 65% using simple organic transformations. Aromatic (co)polyesters bearing pendant azido groups were synthesized by low-temperature solution polycondensation of PPH-N-3 or different molar ratios of PPH-N-3 and bisphenol-A (BPA) with aromatic diacid chlorides in dry dichloromethane in the presence of triethylamine (TEA) as a base. The formation of medium to reasonably high-molecular-weight (co)polyesters was evidenced from intrinsic viscosity and number-average molecular-weight measurements that were in the range 0.52-0.85 dL/g and 16,700-28,200, respectively. Tough, transparent, and flexible films could be cast from chloroform solutions of these (co)polyesters. (Co)polyesters were characterized using FTIR, H-1 NMR, C-13 NMR spectroscopy, XRD, and TGA. The thermal curing reaction of (co)polyesters involving decomposition of azido groups was studied by DSC analysis. The chemical modification of a representative copolyester containing pendant azido groups was carried out quantitatively using catalyst-free azide-maleimide cycloaddition reaction with two maleimides, namely, N-methylmaleimide and N-hexylmaleimide. (c) 2019 Wiley Periodicals, Inc.

10aaromatic (co)polyester10aazido group10acardo bisphenol10aChemical modification1 aMaher, Deepak, M.1 aNagane, Samadhan, S.1 aJadhav, Uday, A.1 aSalunkhe, Pravin, H.1 aTawade, Bhausaheb, V.1 aWadgaonkar, Prakash, P. uhttps://library.ncl.res.in/content/new-cardo-bisphenol-monomer-containing-pendant-azido-group-and-resulting-aromatic-polyesters02543nas a2200253 4500008004100000022001400041245012700055210006900182260000800251300001200259490000700271520162900278653002701907653002601934653002401960653002501984653002902009100002502038700002202063700001802085700002602103700002802129856013202157 2022 eng d a1060-132500aPendant propargyloxy-functionalized aromatic (co)polycarbonates: synthesis, thermal crosslinking and chemical modification0 aPendant propargyloxyfunctionalized aromatic copolycarbonates syn cNOV a752-7630 v593 a

A bisphenol monomer bearing pendant propargyloxy group viz, 1, 1-bis (4-hydoxyphenyl)-1-(4 `-propargyloxyphenyl) ethane (BPP) was synthesized starting from commercially available 1, 1, 1-tris (4-hydroxyphenyl) ethane (THPE) by mono O-propargylation reaction using propargyl bromide. A new series of pendant propargyloxy-functionalized aromatic (co)polycarbonates was synthesized by low-temperature solution polycondensation of BPP or different molar ratios of BPP and bisphenol-A with triphosgene in dichloromethane in the presence of triethylamine. The formation of reasonably high molecular weight (co)polycarbonates was confirmed by inherent viscosity (0.52-0.83 dL/g) and gel permeation chromatography (M-n 37,000-69,800 g/mol, polystyrene standards) measurements. C-13 NMR spectral studies supported formation of random copolycarbonates in copolymerization of BPP and BPA with triphosgene. The 10% weight loss temperature (T-10) values of (co)polycarbonates, determined by thermogravimetric analysis under nitrogen atmosphere, were in the range 427-438 degrees C indicating their good thermal stability. The glass transition temperature (T-g) values of (co)polycarbonates were observed in the range 147-152 degrees C. The crosslinking ability of (co)polycarbonates involving pendant propargyloxy groups leading to formation of networked structure was evaluated via non-isothermal curing studies by DSC. As a proof-of-concept, the post-modification of a representative polycarbonate bearing pendant propargyloxy groups with 1-octane thiol as a model compound via thiol-yne click reaction was briefly studied.

10aAromatic polycarbonate10aChemical modification10apropargyloxy groups10athermal crosslinking10athiol-yne click reaction1 aNagane, Samadhan, S.1 aMaher, Deepak, M.1 aVerma, Savita1 aTalanikar, Aniket, A.1 aWadgaonkar, Prakash, P. uhttps://library.ncl.res.in/content/pendant-propargyloxy-functionalized-aromatic-copolycarbonates-synthesis-thermal-crosslinking