. S. Tomar initiated her scientific career while she was doing her Masters in the Dept of Biophysics, AIIMS by studying the structural aspects of a disintegrin protein from saw scaled viper (Acta Crystallogr D Biol Crystallogr., 2000; J. Mol. Biol., 2004). During her doctoral studies at Purdue University, she studied structural and functional aspects of replication proteins from alphaviruses and illustrated a novel TATase activity of alphavirus RNA dependent RNA polymerase (J. Virol., 2006). After her Ph.D. in 2006, she joined the Department of Biotechnology, IIT Rorokee in 2006 as a Lecturer and in very short period because of her outstanding academic and research record she has been promoted to associate professor. At IIT Roorkee she has established her own research group with focus on investigating the structural and functional aspects of the key replication enzymes of human pathogens such as viral proteases, capsid and viral polymerases of infectious plus-strand RNA viruses including Chikungunya virus. Recently her group has developed and reported a FRET based chikungunya virus protease inhibitor screening assay (Nature Sci. Rep. 2015). Their group was the first one to determine and report the structure of trans-active capsid protease from alphaviruses i.e. Aura virus (J. Virol. 2014). Her group is also focusing on targeting the virus budding cycle by investigating the protein-protein interaction between the viral capsid and the viral glycoproteins. Structural investigations of the capsid protein from Aura virus and its complex with an inhibitor molecule were done by her group that have shed light on the critical protein-protein molecular contacts that are important for virus budding (PLoS ONE, 2012). Her group has also successfully characterized the enzymatic activity of Sindbis virus capping enzyme having methylase and guanylyltransferase activity essential for capping of the viral genome (Protein expr. purif. 2011). Additionally, her group is involved SAR studies of polyamine biosynthesis pathway enzymes. With the combination of molecular biology, site-directed mutagenesis, enzyme kinetics and in silco studies, her group has shown that ODC, in E. histolytica is active in the dimeric form (PLoS Negl Trop Dis. 2012). Later, by making the C-terminal truncations in the EhODC enzyme the group was successful in crystallizing and determining the atomic structure for EhODC enzyme. Structural analysis of EhODC in her lab revealed adaptive mutations in and around the active site of EhODC that lead to DFMO drug resistance (PLoS One. 2013). The above mentioned original contributions from S. Tomar's laboratory may assist in the discovery and development of specific drug molecules to combat these infectious parasites.

Antiviral drug discovery: Chikungunya virus is arthropod-borne, enveloped, positive-sense, single-stranded RNA virus. It belongs to the genus alphavirus that includes nearly 31 members that are causative agents of a range of serious human and livestock diseases. Infection in humans leads cause fever, rash, encephalitis, eye blindness and polyarthritis. In some cases infection by alphavirus such as Venezuelan equine encephalitis virus (VEEV) and Estern equine encephalitis virus (EEEV) leads to ~33% mortality rates. The other virus members of the genus alphavirus include Sindbis virus (SINV), Aura virus and Semliki Forest virus (SFV). Due to frequent epidemic outbreaks of CHIKV in the last decade in the Indian subcontinent, it is considered to be a reemerging pathogen and a potential public health threat. Currently, no antiviral drug or vaccine is available against alphaviruses. Our research group strives to understand the structural and functional mechanism of virus specific enzymes and viral components, develop inhibitor screening assays that are used for identification alphavirus specific inhibitors that can be further rationally developed for antiviral therapies. The 5′ two-third of the alphavirus genome encodes four virus specific replication enzymes (nsP1, nsP2, nsP3 and nsP4), which carry out essential functions during replication of virus in the host cell. The other one-third of the viral genome codes for structural proteins viz. capsid protein (CP), E3, E2, 6K, and E1. In the past, our laboratory has established biochemical assays and characterized the methyltransferase activity of the capping enzymes nsP1 and the viral polymerase activity of nsP4 from Chikungunya virus and Sindbis virus. We have developed an inhibitor screening assay for viral cysteine protease and have reported its structure. nsP2 carries out the indispensable function of cleaving the nsP1234 polyprotein into functional replication components and is an excellent drug target for chikungunya. Based on the structure of nsP2 protease our lab identified and characterized geometric and pharmacophore peptidomimetics inhibitors of the enzyme. We have structurally and functionally analyzed the multifunctional capsid protein (CP) of alphavirus. CP along with making structural component of virus capsid, acts as a serine protease. CP undergoes autocatalytic cleavage to release itself from the rest of the polyprotein. We developed a fluorescence resonance energy transfer (FRET)-based proteolytic assay for high throughput screening (HTS) of inhibitors against this protein. Our group was first to demonstrate it trans-protease activity. We have successfully produced and purified recombinant capsid proteins of Aura virus (AVCP) and Chikungunya virus (CVCP) and also crystallised these proteins. Structures have revelaed that CP contains a hydrophobic pocket through which it is proposed to interact with the viral glycoproteins during virus budding. This pocket has been targeted for therapeutic intervention by blocking it with heterocyclic molecules such as dioxane, piperazine, picolinic acid etc. Piperazine, a drug which was earlier used as anti-histamines and anti-depressants was also validated as potential antiviral in cell-culture based studies. This report of viral inhibition by piperazine has been highlighted in media and all leading national news papers like The Hindu, HT, TOI etc. The project is being continued and efficacy of the drug to inhibit the virus in animal model (mice) is being tested Nutraceutical Drug Discovery and Therapy: Drug resistance on the rise motivates prospective research toward discovery of new bioactive substances from nature and discovery of new application of known drug molecules. The main aim is to identify novel molecules or discover novel bioactivity of existing molecules and characterize these phytomolecules for understanding their properties for antimicrobial and antiviral potency. The antiviral and antibacterial properties of botanicals/phytomolecules such as protease inhibitors, chitinase, lectins, and chitinase-like proteins have immense potential for use in therapeutic interventions and as biopesticides to control infectious disease vectors like mosquitoes. Our group has successfully isolated and characterized phytomolecules like Tamarind Kunitz-type-dual-inhibitor (TKI), chitinase, chi-like lectins, chitinase-like proteins, 11S globulin and 2S albumin. Techniques like various column chromatography, protein estimation, carbohydrate binding, sugar specificities etc are employed to study the potential antimicrobial proteins and molecules. Chitinase-like proteins (CLPs) show fungicidal, insecticidal, antiviral, antiproliferative and mitogenic characteristics. Chitinase and chitinase like protein have been tested as potential antiviral agents against cikungunya and dengue viruses in my laboratory and will be soon patented. The work on tamarind Kunitz proteinase inhibitor, 2S albumin and medicinal plant extract and known food supplements is being carried out in our lab for testing the potency of antiviral and antibacterial