Elucidation of Binding Mechanism of Photodynamic Therapeutic Agent Toluidine Blue O with Chicken Egg White Lysozyme by Spectroscopic and Molecular Dynamics Studies

The nature of binding mechanism of toluidine blue O (TBO) with chicken egg white lysozyme was studied comprehensively by various spectroscopic and computational methods. Both steady state and time‐resolved fluorescence studies unambiguously point to the prevalence of static quenching mechanism in lysozyme–TBO system. Thermodynamic parameters revealed that the association of TBO with lysozyme was a spontaneous process in which hydrophobic and hydrogen bond interactions played a pivotal role in the binding process. The secondary and tertiary conformational changes of lysozyme in the presence of TBO were unraveled using absorption, Fourier transform infrared spectroscopy (FT‐IR) and circular dichroism (CD) techniques. Molecular docking studies of lysozyme–TBO system substantiated the findings of site marker experiment and revealed TBO adjacent to Trp‐63 and Trp‐108 residues of lysozyme. Molecular dynamics (MD) simulation studies of lysozyme–TBO system indicate a stable and effective complexation of TBO with lysozyme. It is hoped that the results presented here will enable further understanding of TBO toxicity.     

One-pot synthesis of Claisen–Schmidt reaction through (E)-chalcone derivatives: Spectral studies in human serum albumin protein binding and molecular docking investigation

An efficient and environmentally benign one-pot multicomponent synthesis of E-chalcones was developed using a mild and reusable new boron nitride-sulphonic acid catalyst. The catalyst was prepared by activating the boron nitride surface with nitric acid, followed by a simple reaction with 3-mercaptopropyl trimethoxysilane. The catalyst was characterized and morphological properties were studied by Fourier transform infrared, X-ray diffraction, transmission electron spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller theory, and Raman spectroscopy techniques. The solid acid catalyst was recycled five times in a Claisen–Schmidt reaction to synthesize new chalcone derivatives, and X-ray crystallography was used to elucidate the structure of (E)-1-(anthracen-9-yl)-3-(2-(4-methylpiperazin-1-yl)quinolin-3-yl)prop-2-en-1-one. A fluorescence quench titration method was used to assess its binding ability with human serum albumin (HSA), while molecular docking was also performed to get a more detailed insight into their interaction at the binding site of HSA.     

Spectral Studies on the Cyclodextrin Inclusion Complexes of Toluidine Blue O and Meldola's Blue in Aqueous Solution

The absorption and emission spectral properties of toluidine blue O (TBO) and Meldola's blue (MDB) in the presence of cyclodextrins (CDs) were studied. Formation of 1 : 1 and 1 : 2 (CD-Dye) inclusion complexes were observed with -CD and -CD, respectively. An increase in the emission intensity was noticed in the presence of -CD due to the formation of 1 : 1 (CD-Dye) inclusion complexes. However, a decrease in the emission intensity was observed in the presence of -CD due to the formation of 1 : 2 (CD-Dye) inclusion complexes. Dimerization of dye molecules in the presence of -CD lead to a decrease in the emission intensity. The formation constants for the 1 : 1 and 1 : 2 (CD-Dye) inclusion complexes were calculated.     

Concentration Dependent Catalytic Activity of Glutathione Coated Silver Nanoparticles for the Reduction of 4-Nitrophenol and Organic Dyes

In the present study, we have synthesized glutathione modified silver nanoparticles (GSH-AgNPs) in aqueous medium and are characterized by absorption, high resolution transmission electron microscope (HR-TEM), selective area electron diffraction (SAED) pattern, dynamic light scattering (DLS), Zeta potential and Fourier transform infrared (FT-IR) spectroscopic measurements. Catalytic activity of GSH-AgNPs has been evaluated for the reduction reactions of 4-nitrophenol (4-NP), methylene blue (MB dye) and eosin Y (EY dye) in presence of sodium borohydride including the effect of catalyst concentration on the catalytic activity. Furthermore, the rate constants of reduction reactions are determined, which are linearly enhanced upon increasing the concentrations of GSH-AgNPs. It is explored that reduction reactions such as 4-NP, organic dyes by NaBH₄ in the presence of catalyst follow a pseudo first order kinetics. The catalytic reduction of 4-NP and organic dyes proceed with a faster rate even in the presence of nanomolar concentration of catalyst.     

Binding Interactions of Toluidine Blue O with Escherichia Coli DNA: Formation of Bridged Structure

The interaction(s) of Toluidine Blue O (TBO) with DNA was investigated using absorption and emission spectral methods. The binding of TBO with DNA was understood from the observed hypochromism in the absorption spectra and decrease in the emission intensity of TBO. From the absorption and emission spectral data, two binding constants were estimated for the binding of TBO with DNA. Based on the binding constant values both intercalative and electrostatic interactions of TBO with DNA were suggested. The TBO-DNA binding constant values reveal that the electrostatic interaction of TBO with DNA is weaker than the intercalative interaction. The emission quenching and salt effect studies showed that the TBO was partially intercalated with DNA. The two modes of binding between TBO and DNA may lead to the formation of bridging of a pair of DNA duplexes by TBO molecule. The electrostatic interaction is more important for the formation of the bridged structure of TBO with DNA. This was verified by studying the interaction of an anionic dye, Eosin Y (EY).     

Colorimetric determination of sulfide using chitosan-capped silver nanoparticles

Microchimica Acta - The article describes a simple method for the rapid photometric and visual detection of sulfide in water samples. Silver nanoparticles were capped with chitosan (chit-AgNPs) and...