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Reddy R.N.,Rational Labs Pvt. Ltd. | Anipindi N.R.,Andhra University
Oxidation Communications | Year: 2011

The kinetics of ruthenium(III)-catalysed oxidation reaction of bis(2,2′,6′,2″-terpyridine)iron(II) by bromate in acetate buffers in the pH range 3.6-5.6 was studied spectrophotometrically. The reaction exhibits first order each in [substrate], [oxidant] and [ruthenium(III)]. Hydrogen ion has no significant effect and ionic strength increases the rate of the reaction. A suitable mechanism has been proposed to explain the kinetic data.

Reddy K.V.,C S R Sarma College | Satyanarayana T.,P.A. College | Anipindi N.R.,Andhra University | Reddy R.N.,Andhra University | Reddy R.N.,Rational Labs Pvt. Ltd.
Oxidation Communications | Year: 2011

The kinetics and mechanism of Ag(I)-catalysed oxidation of bis(2,2′,6′,2″terpyridine)iron(II) by persulphate in acetate buffers in the pH range 3.6-5.6 were studied by spectrophotometric method. The reaction follows first order with respect to the substrate and the oxidant. The rate of the reaction increases with [Ag(I)] and the order with respect to [Ag(I)] is fractional. Hydrogen ion and terpyridine have no significant effect on the rate. Ionic strength decreases the rate of the reaction indicating that the rate-limiting step is between ions of opposite charges. It was also observed that the reaction in acetate buffers is appreciably catalysed by silver(I) and the role of the catalyst has been indicated to be either via the Ag(I)/Ag(II) redox cycle or the intermediate complex of Ag(I)-peroxyacid. A suitable mechanism was proposed and the specific rate constants were evaluated.

The kinetics of oxidation of tris(1,10-phenanthroline)iron(II) and tris(2,2'-bipyridine)iron(II) by chromium(VI) in the presence of 1,10-phenanthroline and 2,2'-bipyridine has been studied in sulphuric acid medium. The order of the reaction is unity both in substrate, oxidant and fractional with hydrogen ion. The catalyst (2,2'-bipyridine/1,10-phenanthroline) accelerates the reaction and the order with respect to [catalyst] is fractional. All these reactions follow the Michaelis-Menton behaviour and rate increases with ionic strength. All the reactions obey the following rate law and a generalised mechanism was proposed: rate = k[Cr(VI)]T K1 K 2 [catalyst] [H+]}/1 + K1 [catalyst] + K 1K2 [catalyst][H+] [Fe(L)3 2+].

Aparoy P.,University of Hyderabad | Reddy R.N.,Rational Labs Pvt. Ltd. | Guruprasad L.,University of Hyderabad | Reddanna P.,University of Hyderabad
Letters in Drug Design and Discovery | Year: 2010

Acidic mammalian chitinase (AMCase) is a potential target for inflammatory disorders, including Th2-driven diseases such as asthma, allergy, atopic dermatitis and allergic rhinitis. AMCase, along with human chitotriosidase (HCHT) are the two human chitinases that are enzymatically active. In this study, a comparative analysis of AMCase (PDB id. 3FY1) was done with that of HCHT (PDB id.1WAW) and Aspergillus fumigatus chitinase (PDB id.1W9U) to identify differences in the binding site topology and interacting residues. Argadin, a natural inhibitor of chitinases, was docked into the active site of AMCase. All the proteins have the DXDXE motif, like other family 18 chitinases. There is a crucial difference in the stacking interactions in chitinases. The chitinase of Aspergillus fumigatus (AfchiB1) is unique in having Phe251 compared to Trp in others at the same position. Arg269 forms strong hydrogen bonds with argadin in HCHT and AfchiB1 but not in AMCase. Many crucial differences between the binding sites of AMCase and HCHT were identified. As AMCase has aroused considerable interest as the major target for the discovery of anti-asthma agents, these differences at the binding site of AMCase may be exploited for selective inhibitor design. The binding affinities, deter- mined based on energy minimization studies, suggest a lower affinity of argadin for AMCase when compared to that for HCHT and AfchiB1. © 2010 Bentham Science Publishers Ltd.

Rathore R.S.,University of Hyderabad | Reddy R.N.,Rational Labs Pvt. Ltd. | Kondapi A.K.,University of Hyderabad | Reddanna P.,University of Hyderabad | And 2 more authors.
Theoretical Chemistry Accounts | Year: 2012

A quantum mechanics (QM)/molecular mechanics (MM)-based free energy perturbation (FEP) method, developed recently, provides most accurate estimation of binding affinities. The validity of the method was evaluated for a large set of diverse inhibitors for fructose 1,6-bisphosphatase (FBPase), a target enzyme for type-II diabetes mellitus. The validation set comprises of 22 important structurally different mutations. The calculated relative binding free energies using the QM/MM-based FEP method reproduce the experimental values with exceptional precision of less than ±0.5 kcal/mol. The CPU requirements for QM/MM-based FEP are about fivefold greater than conventional FEP methods, but it is superior in accuracy of predictions. In addition, the QM/MM-based FEP method eliminates the need for time-consuming development of MM force field parameters, which are frequently required for novel inhibitors described by MM. Future automation of the method and parallelization of the code for 128/256/512 cluster computers is expected to enhance the speed and increase its use for drug design and lead optimization. The present application of QM/MM-based FEP method for structurally diverse set of analogs serves to enhance the scope of FEP method and demonstrate the utility of QM/MM-based FEP method for its potential in drug discovery. © 2012 Springer-Verlag.

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