A Photoresponsive Glycosidase Mimic and Active Site Mimics of other Hydrolytic Enzymes

Samanta, Mousumi (2016) A Photoresponsive Glycosidase Mimic and Active Site Mimics of other Hydrolytic Enzymes. PhD thesis, Indian Institute of Science Education and Research Kolkata.

PDF (PhD thesis of Mousumi Samanta (10RS013)) Mousumi_Samanta_Thesis.pdf - Submitted Version Restricted to Repository staff only Download (4MB)

Abstract

This thesis deals with synthesis and studies of the activity of some enzyme active site mimics. Chapter 1 deals with the general introduction on this area of research, background and present scenario of the related work based on recent literature. Chapter 2 comprises of the synthesis of azobenzene-3,3‟-dicarboxylic acid and studies of glycosidase activity in its E and Z forms. The two carboxylic acid groups in the E form deprotonate simultaneously but in case of Z form it occurs in a stepwise fashion. The mono anionic form of the Z isomer acts as an efficient glycosidase mimic at pH 5.8. The mechanism of the reaction proceed via a general acidgeneral base catalysed mechanism. This is the first example of photomodulated glycosidase mimic. Chapter 3 deals with studies of glycosidase activity of a histidine based bipodal ligand. The ligand was found to act as an efficient glucosidase mimic, and displayed a bell-shaped pHrate profile via a general acid-base catalysed mechanism. The mechanism of the reaction was also elucidated. In chapter 4, we demonstrate the phophodiester bond cleavage by a histidine based bipodal catalyst. Similar to the one observed with ribonuclease A, the catalyst can hydrolyse the phosphodiester bonds through a general acidgeneral base catalysed mechanism where one of imidazole ring (Im) which is in the deprotonated form acts as a general base and the other protonated imidazole ring (ImH+) acts as a general base. In all these work, supramolecular association of the substrate with the enzyme active site mimics take place. In Chapter 5, a binding site mimic of an organic cation based on the cation-π interaction was explored. The cation studied was a lysinium cation, and the recetor was based on a tryptophan based bipodal receptor molecule. The positively charged lysine exhibit the cation-π interaction through aromatic box formation. The interaction between the tryptophan residue and the cationic side chain of lysine was studied in details by one and two-dimension NMR methods and emission spectra.

Actions (login required)

View Item