Prof. Sandeep Verma

Organic Chemistry

  • Designation : Adjunct Professor
  • Phone : +91 (512) 2597643
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Profile Details

    Nucleobase polymers:

    We have recently introduced a novel paradigm for heterogeneous catalyst design by developing polymeric templates based on 9-allyl/9-(4-vinylbenzyl) nucleobase frameworks. These insoluble templates, when coordinated to metal ions, display significant rate enhancements for the hydrolysis of activated phosphate esters, conform to classical Michaelis-Menten kinetics with high turnover numbers. Interestingly, one copper-containing adenylated template displayed a remarkable enzyme-like activity of oxygen insertion between an aromatic C-H bond; an activity reminiscent of hydroxylase/oxidase protein enzymes that catalyze biosynthesis of tyrosine and catecholamines. We are currently applying the knowledge of nucleobase polymer catalysis to other interesting chemical and biochemical reactions. A representative example of the design of polymeric matrix is shown underneath.

    Metal-nucleobase interactions:

    Nucleic acids offer a versatile platform for metal ion coordination resulting in stabilization of higher order superstructures. The constituent heterocyclic nucleobases are bestowed with suitably predisposed metal ion binding sites, which are invoked for the generation of interesting supramolecular structural paradigms. The occurrence of nucleic acid/nucleobase architectures also holds great significance in the cellular milieu where motifs such as guanine(G)-quartets and adenosine platforms, are implicated for a variety of biological functions. We recently reported that 9-allyladenine afforded a 3N coordinated, silver tethered macrocyclic tetraplex, which exhibited aggregative ordering on graphite surface and luminescent properties. This unusual coordination mode, resemblance to biological purine quartets and the presence of silver-mediated helical motifs represents an interesting example of metal-nucleobase interaction, with possible application for the construction of architectures mimicking biological assemblies and metal-organic frameworks.

    Ordered peptide aggregates:

    We are currently involved in understanding structural aspects of ordered biological assemblies as observed during amyloidogenic protein aggregation. We have recently initiated investigations concerning potential role of conserved peptide motifs in biologically interesting proteins, such as prion protein (PrPc) and V3 loop of HIV-1, as �hot-spots� for aggregation. Aggregational behavior is studied using truncated peptide constructs which are aged for a given period of time followed by morphological evaluation of structures so formed by several microscopic techniques. In this context, we have been able to demonstrate aggregation in peptide segments derived from conserved octarepeat motif of prion protein and conserved hexapeptide motif in V3 loop of HIV-1. We have observed time-dependent aggregation leading to the formation of spherical pre-fibrillar structures, eventually culminating into persistent length fibrils. Such synthetic studies, coupled with morphological evaluation, offer an attractive design paradigm for enforcing aggregation in functional peptide segments and it may serve as a model to probe structural basis of protein agglomeration and related phenomenon.

    • S. G. Srivatsan, Sandeep Verma. Synthetic dephosphorylation reagents: Rate enhancement of phosphate monoester hydrolysis by Cu(II)-metalated adenine nucleobase polymers. Chem. Commun. 2000, 515-516.

    • S. G. Srivatsan, Sandeep Verma. Nucleobase containing metalated polymeric resins as artificial phosphodiesterases: Kinetics of hydrolysis, pH dependence and catalyst recycling. Chem. Eur. J. 2001, 7, 828-833.

    • S.G Srivatsan, Masood Parvez, Sandeep Verma. Modeling of prebiotic catalysis with adenylated polymeric templates: Crystal structure studies and kinetic characterization of template-assisted phosphate ester hydrolysis. Chem. Eur. J. 2002, 8, 5184-5191.

    • C. Madhavaiah, Sandeep Verma. Reusable photonuclease: Plasmid scission by a uranyl ion impregnated adenine homopolymer in the presence of visible light and sunlight. Chem. Commun. 2003, 800-801.

    • C. Madhavaiah, Sandeep Verma. Self-aggregation of a reverse bis peptide conjugate derived from the unstructured region of the prion protein. Chem. Commun. 2004, 638-639.

    • K. Krishna Prasad, C. S. Purohit, Alok Jain, R. Sankararamakrishnan, Sandeep Verma. Enforcing solution phase nanoscopic aggregation in a palindromic tripeptide. Chem. Commun. 2005, 2564-2566.

    • C. S. Purohit, Sandeep Verma. A Luminescent Silver-Adenine Metallamacrocyclic Quartet. J. Am. Chem. Soc. 2006, 128, 400-401.

    • S. Ghosh, M. Reches, E. Gazit, Sandeep Verma. Bioinspired design of nano-cages by self-assembling triskelion peptide elements. Angew. Chem., Int. Ed. 2007, 46, 2002-2004 (Highlighted on the inside cover; Covered by The Telegraph, Kolkata).

    • S. Ghosh, Sandeep Verma. Phased fiber growth in a peptide conjugate: Aggregation and disaggregation studies. J. Phys. Chem. B 2007, 111, 3750-3757.

    • C. S. Purohit, Sandeep Verma. Patterned deposition of a mixed-coordination adenine-silver helicate, containing a p-stacked metallacycle, on graphite surface. J. Am. Chem. Soc. 2007, 129, 3488-3489.

    • S. Ghosh, S. K. Singh, Sandeep Verma. Self-assembly and potassium ion triggered disruption of peptide-based soft structures. Chem. Commun. 2007, 2296-2298.

    • C. S. Purohit, A. K. Mishra, Sandeep Verma. Four-stranded coordination helices containing silver-adenine (purine) metallaquartets. Inorg. Chem. 2007, 46, 8493-8495.

    • S. Ghosh, A. Mukherjee, P. J. Sadler, Sandeep Verma. Periodic iron nanomineralization in human serum transferrin fibrils. Angew. Chem., Int. Ed. 2008, 47, 2217-2221 (Highlighted on the inside cover; Marked as Very Important Paper; News & Views in: Nature India; C&E News; EurekAlert; The Telegraph, Kolkata; The Times, UK).

    • K. B. Joshi, Sandeep Verma. Ditryptophan conjugation triggers morphing of biotin fibers to soft spherical structures. Angew. Chem., Int. Ed. 2008, 47, 2860-2863.

    • J. Kumar, C. S. Purohit, Sandeep Verma. Directing spatial disposition of ferrocene around homoadenine tetrads. Chem. Commun. 2008, 2526-2528.

    • J. Kumar, Sandeep Verma. Silver-adenine metallamacrocyclic hexamer. Inorg. Chem. 2009, 48, 6350-6352.

    • P. Singh, J. Kumar, F. Maria Toma, J. Raya, M. Prato, B. Fabre, Sandeep Verma, A. Bianco. Synthesis and characterization of nucleobase-carbon nanotube hybrids. J. Am. Chem. Soc. 2009, 131, 13555-13562.

    • M. D. Pandey, A. K. Mishra, V. Chandrasekhar, Sandeep Verma. Silver-guided excimer emission in an adenine-pyrene conjugate: Fluorescence lifetime and crystal studies. Inorg. Chem. 2010, 49, 2020-2022.

    • Sandeep Verma, A. K. Mishra, J. Kumar. The many facets of adenine: Coordination, crystal patterns and catalysis. Acc. Chem. Res. 2010, 43, 79-91.

    • A. K. Mishra, Sandeep Verma. Decanuclear copper framework supported by a tripodal adenine ligand. Inorg. Chem. 2010, 49, 3691-3693.

    • R. K. Prajapati, J. Kumar, Sandeep Verma. Silver-catalyzed intramolecular cyclization of 9-propargyladenine via N3 alkylation. Chem. Commun. 2010, 46, 3312-3314.

    • K. B. Joshi, K. Vijaya Krishna, Sandeep Verma. Self-assembled morphologies from C2- and C3-symmetric synthetic biotin conjugates. J. Org. Chem. 2010, 75, 4280-4283.

    • K. B. Joshi, Venkatesh. V., Sandeep Verma. Biotin interaction with human erythrocytes: Contact on membrane surface and formation of self-assembled fibrous structures. Chem. Commun. 2010, 46, 3890-3892.

    • A. K. Barman, Sandeep Verma. Sunlight mediated disruption of peptide-based soft structures decorated with gold nanoparticles. Chem. Commun. 2010, 46, 6992-6994.

    • A. K. Mishra, Sandeep Verma. Interconnected trimeric, pentameric and hexameric metallacycles in a singular silver-adenine framework. Inorg. Chem. 2010, 49, 8012-8016.

    • N. Nagapradeep, Sandeep Verma. Characterization of an unprecedented organomercury adduct via Hg(II)-mediated cyclization of N9-propargylguanine. Chem. Commun. 2011, 47, 1755-1757.

    • P. Singh, F. Maria Toma, J. Kumar, Venkatesh, V., J. Raya, M. Prato, Sandeep Verma, A. Bianco. Carbon nanotube-nucleobase hybrids: Nanorings from uracil-modified single-walled carbon nanotubes. Chem. -Eur. J. 2011, 17, 6772-6780.

    • R. K. Prajapati, Sandeep Verma. Adenine coordination around a Cu6I6 core. Inorg. Chem. 2011, 50, 3180-3182.

    • P. Singh, G. Lamanna, C. Menard-Moyon, F. Maria Toma, E. Magnano, F. Bondino, M. Prato, Sandeep Verma, A. Bianco. Adenine functionalization tailors the formation of efficient catalytic silver nanoparticles on carbon nanotubes. Angew. Chem., Int. Ed. 2011, 50, 9893-9897.

    • P. Singh, Venkatesh, V., Nagapradeep, N., Sandeep Verma, A. Bianco. G-quartet type self-assembly of guanine-functionalized singled walled carbon nanotubes. Nanoscale 2012, 4, 1972-1974.

    • P. Singh, C. Menard-Moyon, J. Kumar, B. Fabre, Sandeep Verma, A. Bianco. Nucleobase-pairing triggers the self-assembly of uracil-ferrocene on adenine functionalized multi-walled carbon nanotubes. Carbon 2012 (DOI: 10.1016/j.carbon.2011.10.037).

    • J. Kumar, P. Kanoo, T. K. Maji, Sandeep Verma. Water-absorbing silver-adenine interpenetrated framework. CrystEngComm 2012 (DOI: 10.1039/C2CE06625D).