13 results on '"Divya Tiwari"'
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2. The Potential to use Chloroquine and other 4-Aminoquinoline Analogues to Modulate Persisting Inflammation in Old Age
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Stephen C. Allen and Divya Tiwari
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chemistry.chemical_compound ,chemistry ,Chloroquine ,business.industry ,4-Aminoquinoline ,medicine ,Inflammation ,medicine.symptom ,Pharmacology ,business ,medicine.drug - Published
- 2019
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3. Avoiding Antibiotic Inactivation in Mycobacterium tuberculosis by Rv3406 through Strategic Nucleoside Modification
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Divya Tiwari, Surendra Dawadi, David M. Ferguson, Dirk Schnappinger, Peter Larson, Matthew R. Bockman, Curtis A. Engelhart, and Courtney C. Aldrich
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0301 basic medicine ,medicine.drug_class ,Antitubercular Agents ,Microbial Sensitivity Tests ,Antimycobacterial ,01 natural sciences ,Substrate Specificity ,law.invention ,Mycobacterium tuberculosis ,Structure-Activity Relationship ,03 medical and health sciences ,chemistry.chemical_compound ,Minimum inhibitory concentration ,Biotin ,law ,Lipid biosynthesis ,Drug Resistance, Bacterial ,medicine ,Carbon-Nitrogen Ligases ,chemistry.chemical_classification ,DNA ligase ,Molecular Structure ,biology ,Nucleosides ,biology.organism_classification ,Molecular biology ,0104 chemical sciences ,010404 medicinal & biomolecular chemistry ,030104 developmental biology ,Infectious Diseases ,chemistry ,Recombinant DNA ,Nucleoside - Abstract
5′-[N-(d-biotinoyl)sulfamoyl]amino-5′-deoxyadenosine (Bio-AMS, 1) possesses selective activity against Mycobacterium tuberculosis (Mtb) and arrests fatty acid and lipid biosynthesis through inhibition of the Mycobacterium tuberculosis biotin protein ligase (MtBPL). Mtb develops spontaneous resistance to 1 with a frequency of at least 1 × 10–7 by overexpression of Rv3406, a type II sulfatase that enzymatically inactivates 1. In an effort to circumvent this resistance mechanism, we describe herein strategic modification of the nucleoside at the 5′-position to prevent enzymatic inactivation. The new analogues retained subnanomolar potency to MtBPL (KD = 0.66–0.97 nM), and 5′R-C-methyl derivative 6 exhibited identical antimycobacterial activity toward: Mtb H37Rv, MtBPL overexpression, and an isogenic Rv3406 overexpression strain (minimum inhibitory concentration, MIC = 1.56 μM). Moreover, 6 was not metabolized by recombinant Rv3406 and resistant mutants to 6 could not be isolated (frequency of resistance
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- 2018
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4. Discovery of Novel Muscarinic Receptor Modulators by Integrating a Natural Product Framework and a Bioactive Molecule
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Ganesh Pandey, Divya Tiwari, Shalini Dogra, Yusuf Hussain, Prem N. Yadav, and Rajesh Varkhedkar
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Agonist ,Male ,medicine.drug_class ,Drug Evaluation, Preclinical ,Molecular Conformation ,Computational biology ,Isoindoles ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,chemistry.chemical_compound ,Mice ,Structure-Activity Relationship ,Alkaloids ,Drug Discovery ,Muscarinic acetylcholine receptor ,medicine ,Structure–activity relationship ,Animals ,Humans ,Protein Isoforms ,General Pharmacology, Toxicology and Pharmaceutics ,Receptor ,Maze Learning ,Pharmacology ,Biological Products ,Natural product ,010405 organic chemistry ,Drug discovery ,Organic Chemistry ,Biological activity ,Receptors, Muscarinic ,0104 chemical sciences ,Mice, Inbred C57BL ,HEK293 Cells ,chemistry ,Metals ,Molecular Medicine ,Gephyrotoxin ,Locomotion - Abstract
Muscarinic acetylcholine receptors (mAChRs) are important therapeutic targets for several diseases of the central nervous system and periphery. However, the lack of subtype-selective ligands for these receptors is a major challenge. A novel approach involving the integration of a natural product framework with a bioactive molecule (iNPBM) by using gephyrotoxin and the isoindoline framework is demonstrated for the discovery of new and selective mAChR modulators. We established a scalable and versatile synthetic scheme to enable the synthesis of various analogues that provided the first structure-activity relationship study of this class of compounds. Pharmacological profiling of these compounds demonstrated several ligands with high affinity and selectivity for mAChRs. Specifically, RG-06 and RG-09 were found to be antagonists of M3-mAChR, whereas RG-02 was found to be an agonist at M2-mAChR. Furthermore, RG-02 exhibited salutary effects in an established pharmacological model of a cognitive deficit in mice.
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- 2018
5. Efficient access to enantiopure 1,3-disubstituted isoindolines from selective catalytic fragmentation of an original desymmetrized rigid overbred template
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Rajesh Varkhedkar, Ganesh Pandey, and Divya Tiwari
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Models, Molecular ,Meso compound ,Organic Chemistry ,Carboxylic Acids ,Esters ,Stereoisomerism ,Isoindoline ,Isoindoles ,Amides ,Amino Alcohols ,Biochemistry ,Desymmetrization ,Catalysis ,chemistry.chemical_compound ,Enantiopure drug ,chemistry ,Nucleophile ,Amide ,Organic chemistry ,Sulfhydryl Compounds ,Physical and Theoretical Chemistry - Abstract
An efficient and scalable synthesis of various enantiopure 1,3- disubstituted isoindolines is reported. The base catalyzed nucleophilic fragmentation of a rigid overbred template is established with various substrates to afford the corresponding 1,3-disubstituted isoindoline ester, amide, thioate, 1,3-amino alcohol and isoindolylcarboxylic acid. The crucial rigid overbred template is synthesized in an optically pure form in multigram scale by asymmetric desymmetrization of the corresponding meso compound.
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- 2015
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6. Bisubstrate Inhibitors of Biotin Protein Ligase in Mycobacterium tuberculosis Resistant to Cyclonucleoside Formation
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Dirk Schnappinger, Daniel J. Wilson, Christopher L. Seiler, Courtney C. Aldrich, Divya Tiwari, and Ce Shi
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chemistry.chemical_classification ,DNA ligase ,biology ,Organic Chemistry ,Lipid metabolism ,biology.organism_classification ,Biochemistry ,Microbiology ,Multiple drug resistance ,Mycobacterium tuberculosis ,chemistry.chemical_compound ,Biotin ,chemistry ,Biotinylation ,Lipid biosynthesis ,Drug Discovery ,Adenylylation - Abstract
Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis, is the leading cause of bacterial infectious disease mortality. Biotin protein ligase (BirA) globally regulates lipid metabolism in Mtb through the posttranslational biotinylation of acyl coenzyme A carboxylases (ACCs) involved in lipid biosynthesis and is essential for Mtb survival. We previously developed a rationally designed bisubstrate inhibitor of BirA that displays potent enzyme inhibition and whole-cell activity against multidrug resistant and extensively drug resistant Mtb strains. Here we present the design, synthesis, and evaluation of a focused series of inhibitors, which are resistant to cyclonucleoside formation, a key decomposition pathway of our initial analogue. Improved chemical stability is realized through replacement of the adenosyl N-3 nitrogen and C-5′ oxygen atom with carbon as well as incorporation of a bulky group on the nucleobase to prevent the required syn-conformation necessary for proper alignment of N-...
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- 2013
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7. Ammonia sensing using lossy mode resonances in a tapered optical fibre coated with porphyrin-incorporated titanium dioxide
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Seung-Woo Lee, Stephen W. James, Ralph P. Tatam, Sergiy Korposh, Kevin Mullaney, and Divya Tiwari
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Optical fiber ,Materials science ,business.industry ,chemistry.chemical_element ,engineering.material ,law.invention ,Core (optical fiber) ,Wavelength ,chemistry.chemical_compound ,Optics ,Coating ,chemistry ,law ,Titanium dioxide ,engineering ,Optoelectronics ,business ,Refractive index ,Deposition (law) ,Titanium - Abstract
The development of an ammonia sensor, formed by the deposition of a functionalised titanium dioxide film onto a tapered optical fibre is presented. The titanium dioxide coating allows the coupling of light from the fundamental core mode to a lossy mode supported by the coating, thus creating lossy mode resonance (LMR) in the transmission spectrum. The porphyrin compound that was used to functionalise the coating was removed from the titanium dioxide coating upon exposure to ammonia, causing a change in the refractive index of the coating and a concomitant shift in the central wavelength of the lossy mode resonance. Concentrations of ammonia as small as 1ppm was detected with a response time of less than 1min. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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- 2016
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8. Impact of Zr/Ti ratio in the PZT on the photoreduction of silver nanoparticles
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Qi Zhang, Steve Dunn, and Divya Tiwari
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Materials science ,Aqueous solution ,Band gap ,Mechanical Engineering ,Inorganic chemistry ,Analytical chemistry ,Condensed Matter Physics ,Silver nanoparticle ,Silver nitrate ,chemistry.chemical_compound ,Band bending ,chemistry ,Mechanics of Materials ,General Materials Science ,Thin film ,Stoichiometry ,Deposition (law) - Abstract
Silver nanoparticle deposition from an aqueous solution of silver nitrate onto the surface of PZT thin films of stoichiometric compositions PbZr0.3Ti0.7O3 and PbZr0.52Ti0.48O3 has been investigated. The impact of Zr/Ti ratio on the photochemical properties of PZT is shown by the preferential growth of silver nanoparticles onto the surface. Photoreduction of silver occurs on both c+ and c− domains on PbZr0.52Ti0.48O3 whereas it occurs only on c+ domains on a PbZr0.3Ti0.7O3 surface. The difference in deposition pattern is attributed to difference in magnitude of spontaneous polarization, effective hole concentration and band gap of the two samples which impacts shape and width of space charge layer in the two samples resulting in a change in band bending at the surface.
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- 2009
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9. ChemInform Abstract: Efficient Access to Enantiopure 1,3-Disubstituted Isoindolines from Selective Catalytic Fragmentation of an Original Desymmetrized Rigid Overbred Template
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Ganesh Pandey, Divya Tiwari, and Rajesh Varkhedkar
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chemistry.chemical_compound ,Enantiopure drug ,chemistry ,Fragmentation (mass spectrometry) ,Substrate (chemistry) ,General Medicine ,Isoindoline ,Combinatorial chemistry ,Catalysis - Abstract
The preparation of the asymmetric substrate (I) is elaborated and its KOtBu-catalyzed conversion into enantiopure cis-1,3-disubstituted isoindoline carboxylates.
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- 2015
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10. A high-sensitivity chemical sensor based on titania coated optical-fiber long period grating for ammonia sensing in water
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Stephen W. James, Ralph P. Tatam, Seung-Woo Lee, Sergiy Korposh, and Divya Tiwari
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Optical fiber ,Materials science ,Inorganic chemistry ,Analytical chemistry ,Nanoparticle ,chemistry.chemical_element ,engineering.material ,Cladding (fiber optics) ,law.invention ,chemistry.chemical_compound ,Optical coating ,Adsorption ,chemistry ,Coating ,law ,Titanium dioxide ,engineering ,Titanium - Abstract
Two highly sensitive ammonia sensors, formed by depositing coatings composed of titanium dioxide (TiO2) onto the cladding of an optical fibre sensing platform, are evaluated. A long period grating (LPG) of period 111 μm was fabricated in the core of an optical fibre so that the LPG operates at or near the phase matching turning point (PMTP). The first coating that was investigated was composed of TiO2 nanoparticles deposited by liquid phase deposition. The sensor showed high sensitivity and allowed low concentrations of ammonia in water (0.01 ppm) to be detected with a response time of less than 60 sec. The second coating was composed of TiO2 with subsequent layers of poly (allyamine hydrochloride) (PAH), and SiO2 nanospheres infused with a sensitive element composed of porphine. The ammonia adsorption to the porphine compound led to the changes in the LPG’s transmission spectrum and allowed 0.1 ppm of ammonia in water to be detected with a response time of less than 60 sec.
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- 2015
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11. Influence of annealing on the photochemical deposition of silver onto PZT thin films under UV irradiation
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Divya Tiwari and Steve Dunn
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Aqueous solution ,Volatilisation ,Materials science ,Annealing (metallurgy) ,PZT ,Silver nanoparticle ,Silver nitrate ,chemistry.chemical_compound ,chemistry ,Photochemical deposition ,Chemical engineering ,Materials Chemistry ,Ceramics and Composites ,Defects ,Irradiation ,Composite material ,Thin film - Abstract
Silver nanoparticle deposition from an aqueous solution of 0.01 M silver nitrate solution onto the c + domain of PZT (30/70) thin films has been investigated for samples annealed at a variety of temperatures from 530 to 690 °C. The impact of annealing was to increase the deposition of photoreduced silver on the surface. When the PZT samples were annealed in air at temperatures ranging from 530 to 690 °C the silver deposition increased by more than 200%. The increase in the deposition of the silver is attributed to increase in the defect concentration due to the volatilisation of components from the PZT, most importantly PbO. Variations in the Pb concentration of the sample are measured using EDX and show a marked change, reduction in Pb, with annealing temperature.
- Published
- 2009
12. A charge reversal differentiates (p)ppGpp synthesis by monofunctional and bifunctional Rel proteins
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Vinay Kumar Nandicoori, Divya Tiwari, Balaji Prakash, Dimple Rananaware, and Mathew Sajish
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Circular dichroism ,DNA polymerase ,Stereochemistry ,Stringent response ,Amino Acid Motifs ,Molecular Sequence Data ,Guanosine ,Metal Binding Site ,DNA-Directed DNA Polymerase ,Biochemistry ,Catalysis ,Ligases ,chemistry.chemical_compound ,Escherichia coli ,Streptococcus equi ,Nucleotide ,Magnesium ,Amino Acid Sequence ,Bifunctional ,Molecular Biology ,Polymerase ,DNA Primers ,chemistry.chemical_classification ,Ions ,Binding Sites ,biology ,Dose-Response Relationship, Drug ,Sequence Homology, Amino Acid ,Cell Biology ,Gene Expression Regulation, Bacterial ,Mycobacterium tuberculosis ,chemistry ,Metals ,biology.protein - Abstract
A major regulatory mechanism evolved by microorganisms to combat stress is the regulation mediated by (p)ppGpp (the stringent response molecule), synthesized and hydrolyzed by Rel proteins. These are divided into bifunctional and monofunctional proteins based on the presence or absence of the hydrolysis activity. Although these proteins require Mg(2+) for (p)ppGpp synthesis, high Mg(2+) was shown to inhibit this reaction in bifunctional Rel proteins from Mycobacterium tuberculosis and Streptococcus equisimilis. This is not a characteristic feature in enzymes that use a dual metal ion mechanism, such as DNA polymerases that are known to carry out a similar pyrophosphate transfer reaction. Comparison of polymerase Polbeta and Rel(Seq) structures that share a common fold led to the proposal that the latter would follow a single metal ion mechanism. Surprisingly, in contrast to bifunctional Rel, we did not find inhibition of guanosine 5'-triphosphate, 3'-diphosphate (pppGpp) synthesis at higher Mg(2+) in the monofunctional RelA from Escherichia coli. We show that a charge reversal in a conserved motif in the synthesis domains explains this contrast; an RXKD motif in the bifunctional proteins is reversed to an EXDD motif. The differential response of these proteins to Mg(2+) could also be noticed in fluorescent nucleotide binding and circular dichroism experiments. In mutants where the motifs were reversed, the differential effect could also be reversed. We infer that although a catalytic Mg(2+) is common to both bifunctional and monofunctional proteins, the latter would utilize an additional metal binding site formed by EXDD. This work, for the first time, brings out differences in (p)ppGpp synthesis by the two classes of Rel proteins.
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- 2007
13. Bisubstrate Adenylation Inhibitors of Biotin Protein Ligase from Mycobacterium tuberculosis
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Dirk Schnappinger, Helena I. Boshoff, Clifton E. Barry, Paul A. Sibbald, Benjamin P. Duckworth, Courtney C. Aldrich, Divya Tiwari, Barry C. Finzel, and Todd W. Geders
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Coenzyme A ,Clinical Biochemistry ,Antitubercular Agents ,Microbial Sensitivity Tests ,Biology ,Crystallography, X-Ray ,Biochemistry ,Protein biotinylation ,Article ,Substrate Specificity ,Structure-Activity Relationship ,03 medical and health sciences ,Enzyme activator ,chemistry.chemical_compound ,Bacterial Proteins ,Biotin ,Lipid biosynthesis ,Drug Resistance, Bacterial ,Drug Discovery ,Carbon-Nitrogen Ligases ,Enzyme Inhibitors ,Molecular Biology ,030304 developmental biology ,Pharmacology ,chemistry.chemical_classification ,0303 health sciences ,DNA ligase ,Binding Sites ,030306 microbiology ,Mycobacterium tuberculosis ,General Medicine ,Protein Structure, Tertiary ,3. Good health ,Pyruvate carboxylase ,Enzyme Activation ,Kinetics ,chemistry ,Drug Design ,Biotinylation ,Thermodynamics ,Molecular Medicine - Abstract
SummaryThe mycobacterial biotin protein ligase (MtBPL) globally regulates lipid metabolism in Mtb through the posttranslational biotinylation of acyl coenzyme A carboxylases involved in lipid biosynthesis that catalyze the first step in fatty acid biosynthesis and pyruvate coenzyme A carboxylase, a gluconeogenic enzyme vital for lipid catabolism. Here we describe the design, development, and evaluation of a rationally designed bisubstrate inhibitor of MtBPL. This inhibitor displays potent subnanomolar enzyme inhibition and antitubercular activity against multidrug resistant and extensively drug resistant Mtb strains. We show that the inhibitor decreases in vivo protein biotinylation of key enzymes involved in fatty acid biosynthesis and that the antibacterial activity is MtBPL dependent. Additionally, the gene encoding BPL was found to be essential in M. smegmatis. Finally, the X-ray cocrystal structure of inhibitor bound MtBPL was solved providing detailed insight for further structure-activity analysis. Collectively, these data suggest that MtBPL is a promising target for further antitubercular therapeutic development.
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