Seetharamappa Jaldappagari

The effect of anti-tubercular drug, ethionamide on the secondary structure of serum albumins: a biophysical study.

Serum albumin (SA) is the principal extra cellular protein with higher concentration in the blood plasma and acts as a carrier for many drugs to different molecular targets. The present work is designed to investigate the mechanism of interaction between the protein and an anti-tubercular drug, ethionamide (ETH) at the physiological pH by different molecular spectroscopic techniques viz., fluorescence, UV absorption, CD and FTIR. The interaction of SA with ETH was studied by following the quenching of intrinsic fluorescence of protein by ETH at different temperatures. The Stern-Volmer quenching constant, binding constant and the binding site numbers were calculated from fluorescence results. The results indicated the presence of static quenching mechanism in both HSA-ETH and BSA-ETH systems. The distances of separation between the acceptor and donor were calculated based on the theory of fluorescence resonance energy transfer and were found to be 2.35 nm and 2.18 nm for HSA-ETH and BSA-ETH systems, respectively. The conformational changes in protein were confirmed from UV absorption, CD and FTIR spectral data. Displacement experiments with different site probes revealed that the site I was the main binding site for ETH in protein. Effect of some metal ions was also investigated.

Probing the binding of fluoxetine hydrochloride to human serum albumin by multispectroscopic techniques

The interaction between human serum albumin (HSA) and fluoxetine hydrochloride (FLX) have been studied by using different spectroscopic techniques viz., fluorescence, UV-vis absorption, circular dichroism and FTIR under simulated physiological conditions. Fluorescence results revealed the presence of static type of quenching mechanism in the binding of FLX to HSA. The values of binding constant, K of FLX-HSA were evaluated at 289, 300 and 310 K and were found to be 1.90x10(3), 1.68x10(3) and 1.45x10(3) M(-1), respectively. The number of binding sites, n was noticed to be almost equal to unity thereby indicating the presence of a single class of binding site for FLX on HSA. Based on the thermodynamic parameters, DeltaH(0) and DeltaS(0) nature of binding forces operating between HSA and FLX were proposed. Spectral results revealed the conformational changes in protein upon interaction. Displacement studies indicated the site I as the main binding site for FLX on HSA. The effect of common ions on the binding of FLX to HSA was also investigated.

Bioactive Mechanism of Interaction Between Anthocyanins and Macromolecules Like DNA and Proteins

Anthocyanins are the largest group of naturally occurring phytochemicals, and impart the rich colors ranging from red to violet and blue to fruits, vegetables and other plants. These are the glycosides of polyhydroxy and polymethoxy derivatives of 2-phenylbenzopyrylium or flavylium salts. The interest in anthocyanins has increased immensely during the past decade due to their array of healthily beneficial phytochemicals. Anthocyanins can protect against health damage by some types of harmful oxidants through different mechanisms. The purpose of this article is to review the biological activities of anthocyanins and the interactions of anthocyanins with DNA and protein.

Interactions of polyphenols with plasma proteins: insights from analytical techniques.

Phenolic compounds are commonly found in natural sources like plant-based foods and beverages. These compounds have received much attention due to their unique biological properties. Polyphenols possess a significant binding affinity for serum albumins which are known to be principal extracellular proteins with a high concentration in blood plasma. They act as carriers of several drugs to different molecular targets. This review summarizes the salient features of the reported work on polyphenol-protein interactions by analytical methods viz., chromatography, circular dichroism, fluorescence spectroscopy (steady state and time resolved), light scattering, equilibrium dialysis, differential scanning calorimetry, UV-vis spectroscopy, isothermal calorimetry, MALDI-TOF mass spectrometry, size exclusion chromatography, capillary electrophoresis, electrospray ionization mass spectrometry, FT-IR, molecular modelling, HPLC, NMR, cyclic voltammetry etc. Polyphenol-serum albumin interaction studies assume significance from the view point of pharmacokinetics and pharmacodynamics.

Eco-friendly reduced graphene oxide for the determination of mycophenolate mofetil in pharmaceutical formulations

Graphene oxide (GO) was synthesized and characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). GO was then electrochemically reduced and used for electrochemical study of mycophenolate mofetil (MMF). The electrochemically reduced graphene oxide (ERGO) film on glassy carbon electrode (GCE) showed enhanced peak current for electrooxidation of MMF. MMF exhibited two irreversible oxidation peaks at 0.84 V (peak a1) and 1.1 V (peak a2). Effects of accumulation time, pH and scan rate were studied and various electrochemical parameters were calculated. A differential pulse voltammetric method was developed for the determination of MMF in bulk samples and pharmaceutical formulations. Linear relationship was observed between the peak current and concentration of MMF in the range of 40 nM–15 μM with a limit of detection of 11.3 nM. The proposed method is simple, sensitive and inexpensive and, hence, could be readily adopted in clinical and quality control laboratories.

Spectroscopic and computational approaches to unravel the mode of binding between a isoflavone, biochanin-A and calf thymus DNA

In the present study, attempt was made to explore the interaction between biochanin-A (BioA) and calf thymus DNA (ctDNA) by employing fluorescence spectroscopy, absorption spectroscopy, circular dichroism (CD), DNA melting studies, viscosity measurements, and molecular modeling methods. A well-known fluorescence probe, acridine orange (AO) was used in the present study in order to enhance the emission intensity of weakly fluorescent ctDNA. Quenching in emission intensity of ctDNA-AO system was observed in the presence of different concentrations of BioA, suggesting that BioA has interacted with ctDNA. The hyperchromic effect observed upon the addition of BioA in the absorption spectra of ctDNA-AO without any shift in its absorption maximum revealed that BioA was bound to ctDNA through groove mode of binding. Further the groove mode of binding of BioA to ctDNA was confirmed by DNA melting studies, viscosity measurements, and molecular docking studies. The results of fluorescence measurements that were carried out at different temperature indicated that the BioA has quenched the emission intensity of ctDNA-AO through static mode of quenching mechanism. Thermodynamic parameters revealed that the BioA-ctDNA-AO system was stabilized by van der Waals forces and hydrogen bonding. The effect of binding of BioA on the conformation of ctDNA was examined by circular dichroism studies.