Synthesis of unnatural amino acids and their spectroscopic applications

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The thesis contains a total of 5 Chapters including one Introduction Chapter (Chapter-1). Each chapter contains their individual introduction, experimental and reference sections. In short, Chapter-1 is a critical review of applications of UNAAs in genetic incorporation, site specific protein modification and fluorophoric unnatural amino acids in sensing. Chapter-2 elaborates the synthesis of triazolyl, thiocyanyl, and isothiocyanyl unnatural amino acids via “click‟‟ chemistry, nucleophilic substitution reaction and via decomposition of dithiocarbamic acids salts respectively. Our design concept is focused on possible site specific incorporation of triazolyl amino acids, isothiocyanyl and thiocyanyl amino acids as a new class of side chain modified sulfur-containing amino acids. Chapter-3 describes the application of isothiocyanyl alanine (NCSAla) in the synthesis of thioureayl alanines and then to aminotetrazolyl alanine as other new classes of unnatural amino acids. Our design concept exploited the electrophilicity of –NCS functionality. Chapter-4 deals with isothiocyanyl alanine/lysine as solvatochromic IR responsive probes for possible probing of local structures and electrostatic microenvironment of a short peptide containing NCSAla/ NCSLys with the help of distinct infrared absorption property of –NCS functionality. The electrophilicity of NCSAla and NCSLys in a short tri-/hexa-peptides have further been exploited to label covalently with chromophoric/fluorophoric amine and detail conformational study has been carried out in order to monitor conformational changes. Chapter-5 describes application of fluorescent pyrenylthioureayl alanine amino acid in sensing of Hg2+ and Cu2+ ions in semi aqueous medium
Supervisor: Subhendu Sekhar Bag