@article { ISI:000253563900018, title = {Structure-activity relationship of a hemagglutinin from Moringa oleifera seeds}, journal = {International Journal of Biological Macromolecules}, volume = {42}, number = {2}, year = {2008}, month = {MAR}, pages = {203-207}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The hemagglutinin from the seeds of Moringa oleifera (MoL) agglutinates human as well as rabbit erythrocytes; the affinity for the latter is almost 250 times more than that for the former. MoL was inhibited by glycoproteins namely thyroglobulin, fetuin and holotransferin indicating the complex sugar specificity of the lectin. The protein is a homodimer with molecular mass of 14 kDa, subunits (7.1 kDa) linked by the disulfide bond(s). The secondary structure elements of MoL area-helix, 28\%; beta-sheet, 23\%; turn 20\% and unordered 28\%. While the activity and secondary structure were not affected at extreme pH and high temperature, they were drastically affected in presence of dithiothreitol at and above pH 7.0, indicating that disulfide linkages hold the active conformation of the protein. (C) 2007 Elsevier B.V. All rights reserved.

}, keywords = {disulfide linkages, Moringa oleifera hemagglutinin, Secondary structure}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2007.10.024}, author = {Katre, Uma V. and Suresh, C. G. and Khan, Mohammad Islam and Gaikwad, Sushama M.} } @article { ISI:000264484400007, title = {Comparative studies of two araceous lectins by steady state and time-resolved fluorescence and CD spectroscopy}, journal = {Journal of Fluorescence}, volume = {19}, number = {2}, year = {2009}, month = {MAR}, pages = {239-248}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

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.

}, keywords = {Araceae lectins, Denaturation, fluorescence, Lifetime spectroscopy, Secondary structure}, issn = {1053-0509}, doi = {10.1007/s10895-008-0409-z}, author = {Dharker, Poorva N. and Gaikwad, Sushama M. and Suresh, C. G. and Dhuna, Vikram and Khan, Mohammad Islam and Singh, Jatinder and Kamboj, Sukhdev Singh} } @article { ISI:000291061500032, title = {Conformational transitions in ariesaema curvatum lectin: characterization of an acid induced active molten globule}, journal = {Journal of Fluorescence}, volume = {21}, number = {2}, year = {2011}, month = {MAR}, pages = {753-763}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Biophysical characterization of a lectin from Ariesaema curvatum (ACL) was carried out using steady state as well as time resolved fluorescence and CD spectroscopy under various denaturing conditions. An intermediate with altered tryptophan microenvironment was detected in the phase diagram, which exibited pronounced secondary structure and hemagglutinating activity in presence of 0.25 M Gdn-HCl. An acid induced molten- globule like structure possessing activity and higher thermostability was detected. Transition to the molten globule state was reversible in nature. The lectin retained hemagglutinating activity even after incubation at 95 A degrees C. Both chemical and thermal unfolding of the lectin were found to consist of multistate processes. Fluorescence quenching of ACL was strong with acrylamide and KI. The single tryptophan was found to be surrounded by high density of the positively charged amino acid residues as shown by a ten fold higher K(sv) for KI compared to that for CsCl. The average lifetime of tryptophan fluorescence increased from 1.24 ns in the native state to 1.72 ns in the denatured state.

}, keywords = {Araceae, Fluorescence lifetime, Hemagglutinin, Molten globule, Secondary structure, Thermostability, Unfolding}, issn = {1053-0509}, doi = {10.1007/s10895-010-0766-2}, author = {Sharma, Urvashi and Gaikwad, Sushama M. and Suresh, C. G. and Dhuna, Vikram and Singh, Jatinder and Kamboj, Sukhdev Singh} }