Current Research at BITS, Pilani, K.K. Birla Goa Campus, INDIA
PANIWAER project video
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Synthesis of macrocyclic ligands and metal complex: Activators in advanced oxidation process and antimicrobial agents.
Interestingly, tetrazamacrocyclic ligands were reported to produce stable nickel (III) state. The detailed spectroscopic investigations reveal that the Ni(III) state in a tetradentate macrocyclic ligand is stabilized by coordination of two extra ligands at the axial sites, forming a tetragonal distorted octahedral complex. Importantly, several nickel(II) macrocyclic complexes are reported to act as catalysts involving oxidation processes and formation of trivalent nickel state.
Currently we are involved in the synthesis of new ligands and metal complexes and investigate their use for activating oxidising agents such as persulphate.
Recently, we have reported the activation of persulphate by nickel(II) hexazamacrocyclic complex and its ability to degrade the recalcitrant dye Malachite green.
The project involves extensive use of HPLC, GC, LC-MS and characterization of newly obtained conjugates and ligands. Students will be exposed to the Synthetic strategies and purification methods done in the wet chemistry lab, and DNA damage and antimicrobial studies of these new compounds.
Synthesis of photo-active molecules, nanoparticles and Bio-conjugation.
We are involved in the synthesis and characterization of new photo-isomerisable azo-benzene derivatives, and photo-labile functional groups like ortho-nitrobenzyl derivatives and Investigation on the conjugation of these photoactive derivatives with important drugs, and peptides. We are also involved in the synthesis and characterization of nanoparticles and their conjugation to important biomolecules. DNA damage, and Biological activity of these new conjugate are explored.
(I) Research Work done at Nara Institute of Science and Technology and Kyoto Pharmaceutical University. (Supported by Japan Society for the promotion of Science and Takeda Science Foundation, Takeda Pharmaceuticals, Japan).
I was primarily involved in the synthesis of azobenzene based peptide bioconjugates for designing artificial nucleases. Metal binding peptides were attached to azobenzene based chromophores and indispensable characteristics like facile photo isomerisability and structural difference between the trans and cis isomers were explored. Metal-peptide-Azobenzene conjugates showed DNA cleavage activity and investigation on photo- control of DNA cleavage activities by these conjugates are in progress. I was also involved in the development of water-soluble photocleavable protective groups and its application for design of tumor-targeting paclitaxel prodrugs. Chemical modification of proteins (myoglobin mutants) with photo-active organic groups (nitrobenzyl derivatives, azobenzene derivatives), to photo-control the structure and functions of proteins. Proteins modified with photo-active molecules were characterized by LC-MS techniques and other spectroscopic techniques.
(II) Research work done at the Department of Chemical Sciences, TATA INSTITUTE OF FUNDAMENTAL RESARCH (TIFR), MUMBAI, INDIA.
My research was focused on the Electrospray ionization mass spectrometry (ESI-MS) of proteins. We observed that the maximum positive charge state of the gaseous protein ions is directly related to the number of free surface exposed basic groups (lysine, arginine and histidine) whereas the maximum negative charge state is related to the number of free surface exposed acidic groups (aspartic acid and glutamic acid) of the protein. The free surface exposed basic groups or acidic groups are those which are not involved in any interaction with surrounding amino acids residues and have high propensity to carry formal positive or negative charge. Information on the free surfaced exposed basic groups or acidic groups of proteins were obtained from the x-ray crystal structures. Thus, we have shown a direct correlation of the crystal structure of proteins with the maximum positive and negative charge-states of gaseous protein ions produced by electrospray ionization.
I was also involved in the studies on ESI-MS of Cytochrome P450cam to probe the tertiary structural changes on heme dissociation, and Chemical modification of lysine residues of cytochrome c by acylation reaction to identify the nucleophilic character of various lysine residues in cytochrome c. Specific acylation of the lysine residues of cytochrome c was identified by Collision Induced Dissociation mass spectrometry of the tryptic digest of cytochrome c.
(III) Doctoral Research work at School of Chemistry, Department of Inorganic Chemistry, and National Centre for Ultra fast Processes, UNIVERSITY OF MADRAS, CHENNAI, INDIA.
My doctoral thesis focus on the synthesis and photochemistry of nickel(II) azamacrocyclic complexes. Nitrogen rich azamacrocyclic ligand (nitrogen rich cyclic molecules) and its nickel complexes were synthesized. Photooxidation of nickel(II) azamacrocyclic complexes, resulted in the formation of stable trivalent nickel macrocycles. Time resolved nanosecond laser flash photolysis of the nickel(II) azamacrocylces revealed the transient hydrated electron absorption features, on UV excitation of the of nickel(II) azamacrocyclic complexes. The investigation enlightened that nickel(II) azamacrocyclic complexes posses Charge-transfer to solvent absorption character in the UV region.