Talukdar, Sangita2015-09-232023-10-192015-09-232023-10-192014ROLL NO. 10612246https://gyan.iitg.ac.in/handle/123456789/513Supervisor: Subhendu Sekhar BagThis dissertation entitled SYNTHESIS AND STUDIES ON THE PHOTOPHYSICAL PROPERTIES OF UNNATURAL TRIAZOLYL AND TETRAZOLYL NUCLEOSIDES AND THE APPLICATIONS OF TRIAZOLYL NUCLEOSIDES THEREOF is an embodiment of research aimed towards: the synthesis and photophysical studies of (a) triazolyl and (b) tetrazolyl donor/acceptor aromatic nucleosides, (c) the study of charge transfer complexation (among triazolyl donor/acceptor aromatic nucleosides) mediated DNA duplex stabilization, (d) the study of abasic site stabilization by a triazolyl donor/acceptor aromatic nucleoside and (e) the studies on the dual mechanism to exciplex formation in a chimeric DNA duplex containing an unnatural triazolyl nucleoside paired against a non-nucleoside base surrogate, oxopyrenyl-serinol. Towards this journey several novel unnatural fluorescent/non-fluorescent triazolyl and tetrazolyl donor/acceptor aromatic nucleosides were synthesized, their photophysical properties were evaluated and the biophysical properties of two triazolyl nucleosides were investigated. The thesis contains a total of 6 Chapters including one Review Chapter (Chapter 1). Each chapter contains their individual experimental and reference sections. In short, Chapter 1 is a review of some important unnatural nucleoside base surrogates and their applications. Chapter 2 deals with the synthesis and photophysical properties of some new unnatural triazolyl donor-acceptor nucleosides generated via chemistry. Our design concept was based on the hypothesis that a pair of such donor/acceptor nucleoside might involve in p-stacking as well as in photophysical interaction leading to stabilization of DNA duplex if such nucleosides can be incorporated into short oligonucleotide sequences. Synthesis and studies on the photophysical property of donor-acceptor unnatural tetrazolyl nucleosides are the contents of Chapter 3. Chapter 4 deals with the application of a pair of donoacceptor triazolyl nucleoside to the stabilization of DNA duplexes via charge transfer/p-p stacking interaction. We have shown that ground state charge transfer complexation force among triazolyl unnatural donor-acceptor nucleobase pair (TPhenBDo : TNBBAc ) is good enough to stabilize a DNA duplex.enCHEMISTRYThesis