Multispectroscopic and molecular docking studies on DNA binding of guaifenesin drug.

The interaction mechanism of guaifenesin drug; (RS)-3-(2-methoxyphenoxy)propane-1,2-diol; and calf thymus DNA was characterized by multiple spectroscopic and molecular docking approaches. The changes in drug electronic absorption with increasing DNA concentration and also the observed significant quenching of guaifenesin emission in the presence of DNA proved the complex formation between guaifenesin and DNA during the interactions. Both the binding constant and thermodynamic parameters for the interaction have been calculated in 283, 298, and 310 K at pH 7.4. The results Δ H 0 = 17.87 kJ/mol and Δ S 0 = 143.31 J/mol.K confirmed the role of hydrophobic force in the guaifenesin-DNA interaction. Circular dichroism study showed that guaifenesin causes decrease in the negative band of CT-DNA and at the same time the positive band increases which indicated the transition of DNA conformation from B to A. KI quenching experiment specifies that guaifenesin binds to DNA via nonintercalative mode. The competitive studies based on known Hoechst 33258 and methylene blue probes proved the groove binding mode in guaifenesin-DNA adduct. Further, full agreement of molecular docking simulation with the experimental results of binding constant and interaction mode, support high accuracy of the results.

Fabrication of a novel naltrexone biosensor based on a computationally engineered nanobiocomposite.

A computationally engineered impedimetric naltrexone (NLT) biosensor based on immobilization of bovine serum albumin (BSA) onto fullerene-C60/glassy carbon electrode (FLR/GCE) has been developed using initial characterization by computational methods and complementing them by experimental ones. Computational results showed that BSA hydrophobically binds to FLR which is energetically favorable and leads to the spontaneous formation of the stable nanobiocomposite and also showed that interaction of NLT with BSA is mainly driven by hydrogen bonding and hydrophobic interactions. Besides complementing the computational studies, experimental results showed that addition of FLR to the surface of the electrode facilitated electron transfer reactions, and also showed that the presence of BSA inhibits the interfacial electron transfer in some extent due to the non-conductive properties of BSA. The presence of NLT may form a negatively charged electroactive complex with BSA which repels the negatively charged redox probe and decelerates interfacial electron transfer leading to obvious faradaic impedance change. The faradaic impedance responses were linearly related to naltrexone concentration between 0.1 nM and 80 nM and limit of detection (LOD) was calculated to be 0.01 nM 3Sb/b. Finally, the proposed biosensor was successfully applied to determination of NLT in urine samples of both healthy and addict volunteers.