02046nas a2200265 4500008004100000022001400041245009700055210006900152260007500221300001200296490000700308520112300315653001601438653001701454653001801471653001301489653002101502653002301523653002101546100001901567700001901586700002601605700002501631856012401656 2008 eng d a1053-050900aSteady state and time-resolved fluorescence studies of a hemagglutinin from Moringa oleifera0 aSteady state and timeresolved fluorescence studies of a hemagglu a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGER/PLENUM PUBLISHERScMAR a479-4850 v183 a

The saccharide binding and conformational characterization of a hemagglutinin, a low molecular weight protein from the seeds of Moringa oleifera was studied using steady state and time resolved fluorescence. The lectin binds sugars LacNAc (K-a = 1380 M-1) and fructose (K-a = 975 M-1), as determined by the fluorescence spectroscopy. It has a single tryptophan per monomer which is exposed on the surface and is in a strong electropositive environment as revealed by quenching with iodide. Quenching of the fluorescence by acrylamide involved both static (K-s = 0.216 M-1) and collisional (K-sv= 8.19 M-1) components. The native protein showed two different lifetimes, tau(1) (1.6 ns) and tau(2) (4.36 ns) which decrease and get converted into a single one, (2.21 ns) after quenching with 0.15 M acrylamide. The bimolecular quenching constant, k(q) was 7.55 x 10(11) M-1 s(-1). ANS binding studies showed that the native protein has exposed hydrophobic patches which get further exposed at extreme acidic or alkaline pH. However, they get buried in the interior of the protein in presence of 1 M GdnHCl or urea.

10aANS binding10afluorescence10aHemagglutinin10alifetime10aMoringa oleifera10asaccharide binding10aSolute quenching1 aKatre, Uma, V.1 aSuresh, C., G.1 aKhan, Mohammad, Islam1 aGaikwad, Sushama, M. uhttps://library.ncl.res.in/content/steady-state-and-time-resolved-fluorescence-studies-hemagglutinin-moringa-oleifera-002108nas a2200277 4500008004100000022001400041245011500055210006900170260007500239300001200314490000700326520110400333653002001437653001701457653001701474653002601491653002401517100002401541700002501565700001901590700001801609700002601627700002001653700002701673856013001700 2009 eng d a1053-050900aComparative studies of two araceous lectins by steady state and time-resolved fluorescence and CD spectroscopy0 aComparative studies of two araceous lectins by steady state and  a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGER/PLENUM PUBLISHERScMAR a239-2480 v193 a

Transitions in the tryptophan microenvironment and secondary structure of two monocot lectins from Sauromatum guttatum and Arisaema tortuosum under different denaturing conditions were studied by steady state and time resolved fluorescence and CD spectroscopy. The lectins exist as tetramers with a single tryptophan residue estimated per monomer, present in a polar environment. Quenching with ionic quenchers showed predominantly electropositive environment for tryptophan residues. Acrylamide had maximum quenching effect. A decrease in KI quenching due to lectin denaturation indicated redistribution of charges as a result of possible conformational change. The two values for lifetimes of tryptophanyl population (1.2-1.4 and 6.3-6.4 ns) reduced substantially on quenching or denaturation. Similarly, both the lectins showed a drastic loss of secondary structure in 5 M Gdn-HCl or 6 M Urea or at pH 2.0 and below. For the first time araceous lectins, like legume lectins are shown to bind adenine. The presence of a compact structure at alkaline pH 10.0-12.0 was observed in CD spectra.

10aAraceae lectins10aDenaturation10afluorescence10aLifetime spectroscopy10aSecondary structure1 aDharker, Poorva, N.1 aGaikwad, Sushama, M.1 aSuresh, C., G.1 aDhuna, Vikram1 aKhan, Mohammad, Islam1 aSingh, Jatinder1 aKamboj, Sukhdev, Singh uhttps://library.ncl.res.in/content/comparative-studies-two-araceous-lectins-steady-state-and-time-resolved-fluorescence-and-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-0