@article { ISI:000248203200019, title = {Synthesis and evaluation of 1-deoxy-8-epi-castanospermine, 1-deoxy-8-hydroxymethyl castanospermine, and (6S,7S,8R,8aR)-8-amino-octahydroindolizine-6,7-diol}, journal = {Tetrahedron}, volume = {63}, number = {22}, year = {2007}, month = {MAY}, pages = {4756-4761}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

A short, versatile, and enantioselective synthesis of 1-deoxy-8-epi-castanospermine (5), 1-deoxy-8-hydroxymethyl castanospermine (6), and (6S,7S,8R,8aR)-8-amino-octahydroindolizine-6,7-diol (7) is achieved from a common template 12. The key step utilized is PET provoked amine radical cyclization of 11 to 12 in excellent diastereoselectivity. The exocyclic double bond at C-8 of the template is functionalized to obtain 5-7 as exclusive diastereomers. 1-Deoxy-8-epi-castanospermine exhibited inhibition of alpha- and beta-galactosidase and beta-glucosidase. Compounds 6 and 7 were found to be weak inhibitors of beta-glucosidase. (C) 2007 Elsevier Ltd. All rights reserved.

}, keywords = {1-deoxy-8-epi-castanospermine, castanospermine, Glycosidase inhibitors}, issn = {0040-4020}, doi = {10.1016/j.tet.2007.03.085}, author = {Pandey, Ganesh and Dumbre, Shrinivas G. and Pal, Sujit and Khan, Mohammad Islam and Shabab, A.} } @article { ISI:000257640400029, title = {Serine protease inhibitor from hemolymph of green mussel, perna viridis}, journal = {Bioorganic \& Medicinal Chemistry Letters}, volume = {18}, number = {14}, year = {2008}, month = {JUL}, pages = {3963-3967}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Bioactivity guided fractions of cell-free hemolymph of bacterially challenged marine mussel, Perna viridis led to the isolation of a novel quaternary alkaloid 1, which was identified by its spectral data. The isolated molecule 1 has been found to be a potent serine protease inhibitor ( SPI) showing IC(50) and K(i) values of 102.5 and 97.1-104.68 mu M, respectively. The E(t)/K(i) value of SPI is 6.3, whereas E(t)/K(m) value is 1.04. The Van{\textquoteright}t Hoff analysis showed that the value of K(i) decreases with increase in temperature, and the binding of the inhibitor is entropically driven. (c) 2008 Elsevier Ltd. All rights reserved.

}, keywords = {hemolymph, Natural product, Perna viridis, protease inhibitor}, issn = {0960-894X}, doi = {10.1016/j.bmcl.2008.06.010}, author = {Khan, M. S. and Goswami, U. and Rojatkar, S. R. and Khan, Mohammad Islam} } @article { ISI:000253896400027, title = {Steady state and time-resolved fluorescence studies of a hemagglutinin from Moringa oleifera}, journal = {Journal of Fluorescence}, volume = {18}, number = {2}, year = {2008}, month = {MAR}, pages = {479-485}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

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.

}, keywords = {ANS binding, fluorescence, Hemagglutinin, lifetime, Moringa oleifera, saccharide binding, Solute quenching}, issn = {1053-0509}, doi = {10.1007/s10895-007-0289-7}, author = {Katre, Uma V. and Suresh, C. G. and Khan, Mohammad Islam and Gaikwad, Sushama M.} } @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:000252926700002, title = {Study of papain-cystatin interaction by intensity fading MALDI-TOF-MS}, journal = {Protein Journal}, volume = {27}, number = {1}, year = {2008}, month = {JAN}, pages = {7-12}, publisher = {SPRINGER}, address = {233 SPRING STREET, NEW YORK, NY 10013 USA}, abstract = {

Intensity fading (IF) matrix assisted laser desorption ionization (MALDI) time of flight (TOF) mass spectrometry (MS ) has become an alternative screening approach for the affinity-binding analysis of proteins and peptides with molecular ligands. In this investigation an attempt has been made to study the protein ligand interaction by intensity fading (IF) MALDI-MS using papain and cystatin as model system for protein-ligand interactions. The intensity fading of cystatin was monitored using various concentration of cystatin ranging from (1 to 8.6 mu M) in presence of target protein, papain. The results indeed indicate that the intensity of cystatin decreases upon addition of papain. Furthermore, for the first time we have used IF-MALDI-MS for determining the number of binding sites for cystatin on papain by Scatchard analysis.

}, keywords = {intensity fading, MALDI, papain-cystatin, protein-ligand interaction, Scatchard plot}, issn = {1572-3887}, doi = {10.1007/s10930-007-9102-3}, author = {Shabab, M. and Kulkarni, Mahesh J. and Khan, Mohammad Islam} } @article { ISI:000257424800017, title = {Synthesis of polyhydroxy piperidines and their analogues: a novel approach towards selective inhibitors of alpha-glucosidase}, journal = {Organic \& Biomolecular Chemistry}, volume = {6}, number = {14}, year = {2008}, month = {JAN}, pages = {2587-2595}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Various polyhydroxy piperidine azasugars have been synthesized from precursors 18a and 18b, obtained in both enantiomeric forms from D-ribose. Out of these polyhydroxy piperidine azasugars, 22, 39 and 20 were found to be potent as well as selective inhibitors of a-glucosidase with K(i) values ranging as low as 1.07 mu M, 16.4 mu M, and 88.2 mu M, respectively. Replacement of the hydroxy methylene moiety of 19 (K(i) 33\% at 1 mM) by an amino methylene moiety (32, K(i) 36.8 mu M) showed a remarkable increase in the activity (almost 30 times). Furthermore, increasing the lipophilicity of 33 by N-alkylation with a dodecyl group (36) showed a three-fold enhancement in the activity (K(i) 217 mu M to K(i) 72.3 mu M).

}, issn = {1477-0520}, doi = {10.1039/b804278k}, author = {Pandey, Ganesh and Bharadwaj, Kishor Chandra and Khan, Mohammad Islam and Shashidhara, K. S. and Puranik, Vedavati G.} } @article { ISI:000268481500018, title = {Synthesis of polyfunctional quinolizidine alkaloids: development towards selective glycosidase inhibitors}, journal = {Organic \& Biomolecular Chemistry}, volume = {7}, number = {16}, year = {2009}, month = {JUN}, pages = {3300-3307}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A highly divergent route to a variety of quinolizidine alkaloids is described. The enantiomeric precursors 22a and 22b utilized for the synthesis of these alkaloids were constructed stereospecifically from the PET cyclization of the corresponding acetylene tethered alpha-trimethylsilyl amine moieties 21a and 21b, respectively, both of which were synthesised from D-ribose. The polyhydroxy quinolizidine alkaloid 7 was found to be a selective inhibitor of alpha-galactosidase with Ki 83.9 mu M. The amine analogs 18, 12 and 10 are found to be selective and potent inhibitors of alpha-glucosidase with Ki 28, 120 and 140 mu M, respectively.

}, issn = {1477-0520}, doi = {10.1039/b907007a}, author = {Pandey, Ganesh and Grahacharya, Debasish and Shashidhara, K. S. and Khan, Mohammad Islam and Puranik, Vedavati G.} } @article { ISI:000274401600036, title = {Steady state and time resolved fluorescence quenching and chemical modification studies of a lectin from endophytic fungus fusarium solani}, journal = {Journal of Fluorescence}, volume = {20}, number = {1}, year = {2010}, month = {JAN}, pages = {305-313}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

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.

}, keywords = {Chemical modification, fluorescence, Fusarium, Lectin, Quenching, Time-resolved}, issn = {1053-0509}, doi = {10.1007/s10895-009-0556-x}, author = {Khan, Feroz and Ahmad, Absar and Khan, Mohammad Islam} }