Manjunath D. Meti

Multi-spectroscopic investigation of the binding interaction of fosfomycin with bovine serum albumin☆

The interaction between fosfomycin (FOS) and bovine serum albumin (BSA) has been investigated effectively by multi-spectroscopic techniques under physiological pH 7.4. FOS quenched the intrinsic fluorescence of BSA via static quenching. The number of binding sites n and observed binding constant KA were measured by the fluorescence quenching method. The thermodynamic parameters ΔG0, ΔH0 and ΔS0 were calculated at different temperatures according to the van’t Hoff equation. The site of binding of FOS in the protein was proposed to be Sudlow’s site I based on displacement experiments using site markers viz. warfarin, ibuprofen and digitoxin. The distance r between the donor (BSA) and acceptor (FOS) molecules was obtained according to the Förster theory. The effect of FOS on the conformation of BSA was analyzed using synchronous fluorescence spectra (SFS), circular dichroism (CD) and 3D fluorescence spectra. A molecular modeling study further confirmed the binding mode obtained by the experimental studies.

Multi-spectral characterization & effect of metal ions on the binding of bovine serum albumin upon interaction with a lincosamide antibiotic drug, clindamycin phosphate.

The interaction of clindamycin phosphate (CP) with bovine serum albumin (BSA) is studied by using fluorescence spectra, UV-visible absorption, synchronous fluorescence spectra (SFS), CD, 3D fluorescence spectra and lifetime measurements under simulated physiological conditions. CP effectively quenched intrinsic fluorescence of BSA. The binding constants KA values are 2.540×10(5), 4.960×10(5), 7.207×10(5) L mol(-1), the number of binding sites n and corresponding thermodynamic parameters ΔG(o), ΔH(o) and ΔS(o) between CP and BSA were calculated at different temperatures. The interaction between CP and BSA occurs through dynamic quenching and the effect of CP on the conformation of BSA was also analyzed using SFS. The average binding distance r between the donor (BSA) and acceptor (CP) was determined based on Försters theory. The results of fluorescence spectra, UV-vis absorption spectra and SFS show that the secondary structure of the protein has been changed in the presence of CP.

Evaluation of the binding interaction between bovine serum albumin and dimethyl fumarate, an anti-inflammatory drug by multispectroscopic methods.

The information of the quenching reaction of bovine serum albumin with dimethyl fumarate is obtained by multi-spectroscopic methods. The number of binding sites, n and binding constants, KA were determined at different temperatures. The effect of increasing temperature on Stern-Volmer quenching constants (KD) indicates that a dynamic quenching mechanism is involved in the interaction. The analysis of thermodynamic quantities namely, ∆H° and ∆S° suggested hydrophobic forces playing a major role in the interaction between dimethyl fumarate and bovine serum albumin. The binding site of dimethyl fumarate on bovine serum albumin was determined by displacement studies, using the site probes viz., warfarin, ibuprofen and digitoxin. The determination of magnitude of the distance of approach for molecular interactions between dimethyl fumarate and bovine serum albumin is calculated according to the theory of Förster energy transfer. The CD, 3D fluorescence spectra, synchronous fluorescence measurements and FT-IR spectral results were indicative of the change in secondary structure of the protein. The influence of some of the metal ions on the binding interaction was also studied.

In vitro studies on the interaction between human serum albumin and fosfomycin disodium salt, an antibiotic drug by multi-spectroscopic and molecular docking methods

The interaction between the human serum albumin (HSA) and drug, fosfomycin disodium salt (FOS) has been studied by different spectroscopic techniques. The experimental results showed a static quenching mechanism in the interaction of FOS with HSA. The number of binding sites, n and observed binding constant Ka were measured by fluorescence quenching method. The thermodynamic parameters ΔG°, ΔH° and ΔS° were calculated according to van’t Hoff equation. The calculated distance r between FOS and the protein is evaluated according to the theory of Förster energy transfer. A change in the secondary structure of the protein was evident from the circular dichroism measurements, synchronous fluorescence and three-dimensional fluorescence spectra.

Investigation of binding behaviour of procainamide hydrochloride with human serum albumin using synchronous, 3D fluorescence and circular dichroism

Interaction of procainamide hydrochloride (PAH) with human serum albumin (HSA) is of great significance in understanding the pharmacokinetic and pharmacodynamic mechanisms of the drug. Multi-spectroscopic techniques were used to investigate the binding mode of PAH to HSA and results revealed the presence of static type of quenching mechanism. The number of binding sites, binding constants and thermodynamic parameters were calculated. The results showed a spontaneous binding of PAH to HSA and hydrophobic interactions played a major role. In addition, the distance between PAH and the Trp–214 was estimated employing the Försters theory. Site marker competitive experiments indicated that the binding of PAH to HSA primarily took place in subdomain IIA (Sudlows site I). The influence of interference of some common metal ions on the binding of PAH to HSA was studied. Synchronous fluorescence spectra (SFS), 3D fluorescence spectra and circular dichroism (CD) results indicated the conformational changes in the structure of HSA.

Electro-oxidation and Determination of Procainamide at Glassy Carbon Electrode and its Analytical Applications

Abstract An electrochemical method has been described for the voltammetric oxidation and determination of an antiarrhythmic drug, procainamide (PAH), at a glassy carbon electrode by using cyclic and differential pulse voltammetry (DPV) in phosphate buffer solution under physiological condition, i.e., pH = 7.0. The oxidation process was shown to be irreversible over the pH range studied. PAH undergoes two electron and one proton change and is a diffusion controlled process. The anodic peak current varied linearly with PAH concentration in the range 2.0 × 10-4 to 5.0 × 10-6 M with a limit of detection (LOD) of 1.966 × 10-6 M and limit of quantification (LOQ) 6.554 ×10-6 M. High percentage recovery and study of excipients showed that the method is free from the interferences of the commonly used excipients in the formulations of drug. The proposed method offered advantages of accuracy and time saving as well as simplicity of reagents and apparatus. This method can be employed in clinical analysis, quality control and routine determination of drugs in pharmaceutical formulations.

Osmium(VIII) catalyzed oxidation of an antibiotic drug chloramphenicol by hexacyanoferrate(III) in aqueous alkaline medium: A mechanistic approach

The kinetics of osmium(VIII) catalyzed oxidation of antibiotic drug chloramphenicol by hexacyanoferrate(III) in aqueous alkaline medium was studied spectrophotometrically at 25 ◦ C. The reaction between chloramphenicol and hexacyano- ferrate(III) in alkaline medium exhibits 1:2 stoichiometry (CHP:HCF(III)). The reaction is first order in (HCF(III)) and (Os(VIII)) and apparently less than unit order in (CHP) and (OH − ) under the experimental conditions. The main oxidation products were identified by TLC and characterized by GCMS, IR, and 1 H NMR spectra. The active species for the catalyst and oxidant have been identified. Probable mechanism are proposed and discussed. The activation parameters with respect to the slow step of the mechanism were computed and thermodynamic quantities are calculated.

Anodic Voltammetric Behavior of Lincomycin and its Electroanalytical Determination in Pharmaceutical Dosage form and Urine at Gold Electrode

Abstract The anodic voltammetric behavior of an antibiotic drug, lincomycin hydrochloride (LIN) at gold electrode (GE) has been investigated using cyclic and linear sweep voltammetry. The dependence of the current on pH, concentration and scan rate were investigated to optimize the experimental conditions for the determination of lincomycin. The anodic peak was characterized and the process was adsorption-controlled. The number of electrons transferred in the oxidation process was calculated. In the range of 8.0×10−6 to 1.0×10−4 M, the current measured by linear sweep voltammetry presents a good linear property as a function of the concentration of lincomycin with a detection limit of 1.7×10−7 M with good selectivity and sensitivity. The proposed method was successfully applied to lincomycin determination in pharmaceutical dosage form and in urine as a real sample. This method can be employed in clinical analysis, quality control and routine determination of drugs in pharmaceutical formulations.

A spectroscopic investigation of kinetics and mechanism of ruthenium(III)-catalyzed oxidation of N-(2-hydroxyethyl)phthalimide by cerium(IV) in aqueous sulphuric acid and sulphate media

Abstract The oxidation of N-(2-hydroxyethyl)phthalimide with cerium(IV) with a small amount of ruthenium(III) present as a catalyst has been studied by spectrophotometric means. The spectroscopic study has been carried out in aqueous H2SO4 and media at constant ionic strength of I = 1.60 mol dm−3. Stoichiometric analysis shows that one mole of NHEP reacts with two moles of cerium(IV). The oxidation products were identified by IR and GC–MS. Orders with respect to substrate, oxidant, ruthenium(III) and acid concentrations were determined. Increase in sulphuric acid concentration increases the rate. Effect of ionic strength and solvent polarity of the medium on the rate of the reaction was studied. The added product, cerium(III), has no significant effect on the rate of reaction. The active species of oxidant in sulphate medium and catalyst are and [Ru(H2O)6]3+. Based on the experimental results a suitable mechanism is proposed. The activation parameters and the thermodynamic quantities are also determined and discussed.

Voltammetric oxidation of carbenicillin and its electro analytical applications at gold electrode

Abstract The electrochemical oxidation of carbenicillin disodium salt (CDS) at gold electrode has been investigated for the first time using cyclic, linear sweep, and differential pulse voltammetric techniques. The dependence of the current on pH, concentration, and scan rate were investigated to optimize the experimental conditions for the determination of carbenicillin. The anodic peak was characterized and process was adsorption-controlled. The number of electrons transferred in the oxidation was calculated. A differential pulse voltammetry method with good precision and accuracy was developed for the determination of carbenicillin. The anodic peak current varied linearly with carbenicillin concentration in the range 1.0 × 10−4 M to 5.0 × 10−6 M with a limit of detection (LOD) of 6.859 × 10−7 M and limit of quantification (LOQ) of 2.286 × 10−6 M. This method can be employed in clinical analysis, quality control, and routine determination of drugs in pharmaceutical analysis.