Publications by authors named "Shekhar Kumar"

In the current study, optimal supercritical fluid extract (SFE) of Lagerstroemia speciosa (LS) leaves at pressure 29.59 MPa (MPa), temperature 89.50 °C and extraction time 53.

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Metal dipyrrinato complexes of 4d and 5d metals have distinctive features such as high absorption coefficients in the visible section and room temperature phosphorescence in the red region. This work demonstrates the light-assisted oxidation of organic compounds employing rhenium(I)dipyrrinato complexes as catalysts. The heavy atom effect in rhenium(I)dipyrrinato complexes leads to the formation of long-lived triplet excited states, and these complexes can generate singlet oxygen in excellent yields (up to 84 %).

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Potent and selective inhibition of the structurally homologous proteases of coagulation poses challenges for drug development. Hematophagous organisms frequently accomplish this by fashioning peptide inhibitors combining exosite and active site binding motifs. Inspired by this biological strategy, we create several EXACT inhibitors targeting thrombin and factor Xa de novo by linking EXosite-binding aptamers with small molecule ACTive site inhibitors.

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Covalent organic frameworks (COFs) are an outstanding platform for heterogeneous photocatalysis. Herein, we synthesized a pyrene-based two-dimensional C[double bond, length as m-dash]C linked π-conjugated COF Knoevenagel condensation and anchored Ni(ii)-centers through bipyridine moieties. Instead of traditional dual metallaphotoredox catalysis, the mono-metal decorated Ni@Bpy-spc-COF interlocked the catalysis mediated by light and the transition metal.

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Coagulation cofactors profoundly regulate hemostasis and are appealing targets for anticoagulants. However, targeting such proteins has been challenging because they lack an active site. To address this, we isolate an RNA aptamer termed T18.

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To understand the role of substrate plasminogen kringles in its differential catalytic processing by the streptokinase - human plasmin (SK-HPN) activator enzyme, Fluorescence Resonance Energy Transfer (FRET) model was generated between the donor labeled activator enzyme and the acceptor labeled substrate plasminogen (for both kringle rich Lys plasminogen - LysPG, and kringle less microplasminogen - µPG as substrates). Different steps of plasminogen to plasmin catalysis i.e.

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A strictly aerobic, haloalkali-tolerant, Gram-stain-positive, non-motile, rod-shaped bacterium, designated strain SMB4, was isolated from a water sample collected from Sambhar salt lake, Rajasthan, India. Growth occurred at 25-50 °C, 4-12 % (w/v) NaCl and pH of 5-9. Strain SMB4 was positive for β-galactosidase, oxidase, catalase and urease activities.

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A novel Gram-stain-positive, rod-shaped, motile, spore-forming, strictly aerobic, alkali- and halo- tolerant bacterium, designated strain AK72, was isolated from a water sample collected from Sambhar salt lake, Rajasthan, India. The colony appears circular, shiny, smooth, translucent or slightly pale in colour and convex with an entire margin after 48 h incubation at 37 °C with pH 9. Growth of the bacterium occurred at 10-42 °C (optimum, 25-37 °C), at salinities of 0.

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Unfractionated heparin (UFH), the standard anticoagulant for cardiopulmonary bypass (CPB) surgery, carries a risk of post-operative bleeding and is potentially harmful in patients with heparin-induced thrombocytopenia-associated antibodies. To improve the activity of an alternative anticoagulant, the RNA aptamer 11F7t, we solved X-ray crystal structures of the aptamer bound to factor Xa (FXa). The finding that 11F7t did not bind the catalytic site suggested that it could complement small-molecule FXa inhibitors.

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Unlabelled: The Mycobacterium tuberculosis exported repetitive protein (RvErp) is a crucial virulence-associated factor as determined by its role in the survival and multiplication of mycobacteria in cultured macrophages and in vivo Although attempts have been made to understand the function of Erp protein, its exact role in Mycobacterium pathogenesis is still elusive. One way to determine this is by searching for novel interactions of RvErp. Using a yeast two-hybrid assay, an adenylyl cyclase (AC), Rv2212, was found to interact with RvErp.

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Streptokinase (SK) is an efficient thrombolytic agent that dissolves fibrin blood clots with clinical efficiency comparable to the high priced drug, tissue plasminogen activator (tPA). However, being of bacterial origin, its major drawbacks are its potentially high antigenicity, and relatively short circulating half-life (approximately 10-15 min). In the present investigation, an attempt has been made to address both these shortcomings by site-specific pegylation, and to obtain longer lasting thrombolytics, which are consistent with clinical requirements.

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With the goal of identifying hitherto unknown surface exosites of streptokinase involved in substrate human plasminogen recognition and catalytic turnover, synthetic peptides encompassing the 170 loop (CQFTPLNPDDDFRPGLKDTKLLC) in the beta-domain were tested for selective inhibition of substrate human plasminogen activation by the streptokinase-plasmin activator complex. Although a disulfide-constrained peptide exhibited strong inhibition, a linear peptide with the same sequence, or a disulfide-constrained variant with a single lysine to alanine mutation showed significantly reduced capabilities of inhibition. Alanine-scanning mutagenesis of the 170 loop of the beta-domain of streptokinase was then performed to elucidate its importance in streptokinase-mediated plasminogen activation.

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