• P Balaram

      Articles written in Journal of Chemical Sciences

    • Solubilization of bilirubin by cholate micelles. Spectroscopic and gel permeation studies

      Kasturi Lahiri Puranam P Balaram

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      The interactions of bilirubin with bile salts have been studied using fluorescence, circular dichroism and1H NMR methods. Enhancement of bilirubin fluorescence and induction of optical activity in bilirubin in the presence of cholate has been observed. Fluorescence enhancement is pronounced above the critical micelle concentration, while induced CD bands are detectable even in the premicellar region. Dehydrocholate and deoxycholate did not cause a fluorescence increase, but induced CD bands were observed for bilirubin in these cases. Gel permeation chromatography on Sephadex G-50 yielded a single bilirubin-cholate species at alkaline pH, while two species were obtained at neutral pH.1H NMR and CD spectral characterizations of these complexes are reported. A 4∶1 cholate-bilirubin mixture has been analysed by difference (nuclear Overhauser effect) NOE spectroscopy. Observation of strong, negative NOE, both intermolecular and intramolecular leads to the conclusion that specific methyl groups on bilirubin and cholate are proximal in the mixed micelle.

    • Non-protein amino acids in peptide design

      S Aravinda N Shamala Rituparna S Roy P Balaram

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      An overview of the use of non-protein amino acids in the design of conformationally well-defined peptides, based on work from the author’s laboratory, is discussed. The crystal structures of several designed oligopeptides illustrate the useα-aminoisobutyric acid (Aib) in the construction of helices, D-amino acids in the design of helix termination segments andDPro-Xxx segments for nucleating ofβ-hairpin structures.β- andγ-amino acid residues have been used to expand the range of designed polypeptide structures.

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