Seminar Title
Supramolecular Polymers and Gels of Guanosine and Peptide Conjugates
Seminar Type
Progress Seminar
Speaker Name
Nihar Sahu ( Rollno : 520cy1002)
Speaker Type
Chemistry Seminar Room
Date & Time
05 Jun 2023 3:30 PM
Dr. Bimalendu Adhikari

Biological processes involve highly specific interactions but commonly lie away from covalent chemistry. Such interactions introduced a new field of study, supramolecular chemistry, which involves non-covalent interactions, which are weaker in nature but enable a tremendous opportunity to form functional material. Due to their specificity and reversibility, such materials show stimuli-responsiveness, adaptation to the environment, and self-healing properties. In this regard, one extensively studied biomolecule is guanosine. Guanosine forms various supramolecular structures by its multiple hydrogen bond donor-acceptor units, and one of the most studied architectures is a tetrameric structure stabilized by a metal ion called Guanosine Quartets. However, these supramoleular polymers are mostly labile and weak in nature and the resulting gels are often associated with low lifetime and mechanical stability. To address this issue, herein attempts have been made to synthesize very strong and efficient supramolecular polymer gels of G-quadruplex, (G4.M+)n with the expectation of exploring new properties and functionalities. The design principle also involves the creation of a hydrogel with an inbuilt responsive G-quartet. Toward this aim, we have introduced the coinage metal copper(I) ion to form a G-Quartet, where the soft-soft interaction between copper and carbonyl oxygen of guanosine will lead to the formation of a robust hydrogel with inbuilt redox responsiveness owing to the redox chemistry of copper ion. Henceforth, we optimized the supramolecular polymerization process leading to gelation, forming a thermoset polymer with redox responsiveness, which was characterized using UV-Vis, CD, TEM, FESEM, and Rheological studies. Moreover, peculiar faster gelation at higher temperatures was observed, suggesting an entropy-driven supramolecular polymerization process. In order to probe the molecular arrangement in the G-Cu(I) polymer, we have synthesized a lipophilic guanosine molecule capable of forming a G-quadruplex-based crystal, which in turn will help the understanding of such strong supramolecular gel of G-Cu(I) system. Next, spontaneous syneresis of the G-Cu(I) hydrogel over time and swelling of the freeze-dried G-Cu(I) gel were observed, which is not typical for gel which are being explored in details currently. The thesis also aims to utilize the Cu(I) ion-induced exceptionally higher stability of G-quadruplex formation in naturally occurring covalent DNA aptamers. We also plan to synthesize guanosine-peptide conjugates to combine the higher-order structures of DNA and proteins to make novel bioconjugates, where the aromatic core unit of guanosine forms a columnar G-quadruplex by &pi- &pi stacking and peptides form beta-sheet structure by intermolecular hydrogen bonds, improving G-quadruplex stability and incorporating functionality into the biomaterials.