Kirpal S. Bisht

Bio: Kirpal S. Bisht is an academic researcher from University of South Florida. The author has contributed to research in topics: Lipase & Candida antarctica. The author has an hindex of 26, co-authored 137 publications receiving 3360 citations. Previous affiliations of Kirpal S. Bisht include University of Massachusetts Lowell & University of Massachusetts Boston.

How Well Should the Active Site and the Specific Recognition Be Defined for Proficient Catalysis? – Effective and Cooperative Polyphenol/Catechol Oxidation and Oxidative DNA Cleavage by a Copper(II)‐Binding and H‐Bonding Copolymer

Abstract: Despite the mainly inhomogeneous and unstructured nature of linear polymers, the CuII complex of a vinylpyridine-acrylamide copolymer exhibits very efficient 2-electron catalysis toward the oxidation of catechol and derivatives to form quinones with and without 80 mM (0.27 %) H2O2, showing remarkable (0.114–2.67) × 105 and (2.83–9.60) × 104-fold rate enhancements, respectively, in terms of first-order rate constant relative to auto-oxidation of the substrates in an aqueous environment under mild conditions. Metal-binding profiles suggest the presence of cooperativity in the catalysis. The oxidation catalysis is inhibited by the di-copper tyrosinase specific kojic acid. Moreover, electron paramagnetic resonance spectra reveal magnetic interaction of the CuII ions. On the basis of the results, the catalysis by this CuII-polymer seems to be consistent with the mechanism of type-3 di-copper oxidases. This complex also shows effective single- and double-stranded DNA cleavage in the presence of 1.0 % H2O2. These studies suggest this CuII-polymer complex can serve as a unique “chemical nuclease” and a versatile chemical system for further exploration of Cu–oxygen chemistry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The Jak2 small molecule inhibitor, G6, reduces the tumorigenic potential of T98G glioblastoma cells in vitro and in vivo.

Abstract: Glioblastoma multiforme (GBM) is the most common and the most aggressive form of primary brain tumor. Jak2 is a non-receptor tyrosine kinase that is involved in proliferative signaling through its association with various cell surface receptors. Hyperactive Jak2 signaling has been implicated in numerous hematological disorders as well as in various solid tumors including GBM. Our lab has developed a Jak2 small molecule inhibitor known as G6. It exhibits potent efficacy in vitro and in several in vivo models of Jak2-mediated hematological disease. Here, we hypothesized that G6 would inhibit the pathogenic growth of GBM cells expressing hyperactive Jak2. To test this, we screened several GBM cell lines and found that T98G cells express readily detectable levels of active Jak2. We found that G6 treatment of these cells reduced the phosphorylation of Jak2 and STAT3, in a dose-dependent manner. In addition, G6 treatment reduced the migratory potential, invasive potential, clonogenic growth potential, and overall viability of these cells. The effect of G6 was due to its direct suppression of Jak2 function and not via off-target kinases, as these effects were recapitulated in T98G cells that received Jak2 specific shRNA. G6 also significantly increased the levels of caspase-dependent apoptosis in T98G cells, when compared to cells that were treated with vehicle control. Lastly, when T98G cells were injected into nude mice, G6 treatment significantly reduced tumor volume and this was concomitant with significantly decreased levels of phospho-Jak2 and phospho-STAT3 within the tumors themselves. Furthermore, tumors harvested from mice that received G6 had significantly less vimentin protein levels when compared to tumors from mice that received vehicle control solution. Overall, these combined in vitro and in vivo results indicate that G6 may be a viable therapeutic option against GBM exhibiting hyperactivation of Jak2.

The combinatorial synthesis of bicyclic privileged structures or privileged substructures

Abstract: Privileged substructures are of potentially great importance in medicinal chemistry. These scaffolds are characterized by their ability to promiscuously bind to a multitude of receptors through a variety of favorable characteristics. This may include presentation of their substituents in a spatially defined manner and perhaps also the ability to directly bind to the receptor itself, as well as exhibiting promising characteristics to aid bioavailability of the overall molecule. It is believed that some privileged substructures achieve this through the mimicry of common protein surface elements that are responsible for binding, such as β- and gamma;-turns. As a result, these structures represent a promising means by which new lead compounds may be identified.

Synthesis of polycaprolactone: a review

Abstract: Polycaprolactone (PCL) is an important polymer due to its mechanical properties, miscibility with a large range of other polymers and biodegradability. Two main pathways to produce polycaprolactone have been described in the literature: the polycondensation of a hydroxycarboxylic acid: 6-hydroxyhexanoic acid, and the ring-opening polymerisation (ROP) of a lactone: e-caprolactone (e-CL). This critical review summarises the different conditions which have been described to synthesise PCL, and gives a broad overview of the different catalytic systems that were used (enzymatic, organic and metal catalyst systems). A surprising variety of catalytic systems have been studied, touching on virtually every section of the periodic table. A detailed list of reaction conditions and catalysts/initiators is given and reaction mechanisms are presented where known. Emphasis is put on the ROP pathway due to its prevalence in the literature and the superior polymer that is obtained. In addition, ineffective systems that have been tried to catalyse the production of PCL are included in the electronic supplementary information for completeness (141 references).