@article { ISI:000254697200009, title = {Purification and characterization of a T-antigen specific lectin from the coelomic fluid of a marine invertebrate, sea cucumber (Holothuria scabra)}, journal = {Fish \& Shellfish Immunology}, volume = {24}, number = {4}, year = {2008}, month = {APR}, pages = {450-458}, publisher = {ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD}, address = {24-28 OVAL RD, LONDON NW1 7DX, ENGLAND}, abstract = {

A novel lectin was purified from the coelomic fluid of the sea cucumber Holothuria scabra (HSL), subjected to bacterial challenge. HSL is a monomeric glycoprotein of molecular mass 182 kDa. The lectin is highly thermostable as it retains full activity for 1 h at 80 degrees C. Further, the hemagglutination activity of HSL is unaffected by pH in the range 2-11. Unlike other lectins purified from marine invertebrates, the hemagglutination activity of HSL does not require any divalent metal ions. The affinity profile of HSL was studied by a combination of hemagglutination inhibition and fluorescence spectroscopy. HSL binds to desialylated glycoproteins, Me alpha Gal, T-antigen and T (alpha-ser)-antigen with a distinction between beta 1-4 and beta 1-3 linkages. Me alpha-T-antigen was a potent ligand having highest affinity (K-a 8.32 x 10(7) M-1). Monosaccharide binding is enthalphically driven while disaccharide binding involves both entropic and enthalpic contributions. (c) 2008 Elsevier Ltd. All rights reserved.

}, keywords = {Fluorescence spectroscopy, Holothuria scabra, Lectin, marine invertebrate, Thermodynamic properties}, issn = {1050-4648}, doi = {10.1016/j.fsi.2008.01.002}, author = {Gowda, Nagaraj M. and Goswami, Usha and Khan, Mohammad Islam} } @article { ISI:000323401200004, title = {Synthesis and fluorescence properties of a full set of extended RNA base analogues}, journal = {Indian Journal of Chemistry Section A-Inorganic Bio-Inorganic Physical Theoretical \& Analytical Chemistry}, volume = {52}, number = {8-9, SI}, year = {2013}, month = {AUG}, pages = {1004-1013}, publisher = {NATL INST SCIENCE COMMUNICATION-NISCAIR}, address = {DR K S KRISHNAN MARG, PUSA CAMPUS, NEW DELHI 110 012, INDIA}, abstract = {

The synthesis and photophysical characterization of a complete set of fluorescent RNA base analogues derived by conjugating benzofuran moiety at the 5- and 8-positions of pyrimidine and purine bases, respectively, are described. Benzofuran-modified pyrimidine and purine ribonucleoside analogues exhibit Contrasting fluorescence properties. Pyrimidine analogues are moderately emissive with emission maximum in the visible region, and importantly, are highly sensitive to solvent polarity and Viscosity changes. On the other hand, purine analogues are highly emissive and are minimally affected by solvation. and viscosity effects. Thorough photophysical analysis reveals that the pyrimidine and purine ribonucleosides displaying distinct and-probe-like fluorescence properties could be useful in designing nucleic acid based biophysical tools to study nucleic acid structure and function.

}, keywords = {Environment sensitive probes, Fluorescence probes, Fluorescence spectroscopy, Nucleic acids, Ribonucleoside analogues}, issn = {0376-4710}, author = {Sabale, Pramod M. and Nuthanakanti, Ashok and Srivatsan, Seergazhi G.} } @article {47344, title = {pH-dependent protein stability switch coupled to the perturbed pKa of a single ionizable residue}, journal = {Biophysical Chemistry}, volume = {274}, year = {2021}, month = {JUL}, pages = {106591}, type = {Article}, abstract = {

The contribution of electrostatic interactions in protein stability has not been fully understood. Burial of an ionizable amino acid inside the hydrophobic protein core can affect its ionization equilibrium and shift its pKa differentially in the native (N) and unfolded (U) states of a protein and this coupling between the folding/ unfolding cycle and the ionization equilibria of the ionizable residue can substantially influence the protein stability. Here, we studied the coupling of the folding/unfolding cycle with the ionization of a buried ionizable residue in a multi-domain protein, Human Serum Albumin (HSA) using fluorescence spectroscopy. A pHdependent change in the stability of HSA was observed in the near native pH range (pH 6.0-9.0). The protonation-deprotonation equilibrium of a single thiol residue that is buried in the protein structure was identified to give rise to the pH-dependent protein stability. We quantified the pKa of the thiol residue in the N and the U states. The mean pKa of the thiol in the N state was upshifted by 0.5 units to 8.7 due to the burial of the thiol in the protein structure. Surprisingly, the mean pKa of the thiol in the U state was observed to be downshifted by 1.3 units to 6.9. These results indicate that some charged residues are spatially proximal to the thiol group in the U state. Our results suggest that, in addition to the N state, electrostatic interactions in the U state are important determinants of protein stability.

}, keywords = {electrostatic interactions, Fluorescence spectroscopy, Thermodynamic stability, Unfolded proteins}, issn = {0301-4622}, doi = {10.1016/j.bpc.2021.106591}, author = {Mishra, Prajna and Patni, Divya and Jha, Santosh Kumar} }