Search

A sensitive resonance Rayleigh light scattering (RLS) assay for alpinetin was developed based on alpinetin‐modified gold nanorods (AuNRs). Alpinetin could interact with AuNRs and formed a new assembly by electrostatic attraction. In pH 7.4 Tris–HCl buffer solution, the assembly of alpinetin–AuNRs showed a sensitive RLS signal. Under optimum conditions, the magnitude of enhanced RLS intensity (ΔIRLS) was proportional to the concentration of alpinetin over the range 0.027–3.24 μg ml−1, with a detection limit of 1.79 ng ml−1 (by 3σ). The developed RLS method was successfully applied to the detection of alpinetin in real or synthesized samples. Alpinetin recoveries were 90.4–108.7% with an RSD of 0.82–2.9% (n = 5) for Alpinia katsumadai samples, and 95.1–103.7% with an RSD of 0.28–3.9% (n = 5) for synthesized samples. The results showed that this new approach was convenient, reliable and sensitive. [ABSTRACT FROM AUTHOR]

A highly sensitive method for the detection of 6-mercaptopurine (MP) by resonance Rayleigh light scattering (RLS) method was developed. Gold nanoparticles (AuNPs) were synthesized by a modified seed method and characterized using transmission electron microscopy (TEM). AuNPs were bound to MP via covalent bonding to form the MP-AuNPs complex, which increased the RLS intensity of MP at 347 nm (increased by 65.7%). Under optimum conditions, the magnitude of the enhanced RLS intensity for MP-AuNPs was proportional to MP concentration in the range 0.0681-1.702 μg mL−1. The linear regression equation was represented as follows: Δ I RLS = 9.31 + 82.42 c ( r = 0.9948). The limit of detection (LOD, 3σ) was 3.32 ng mL−1. The system was applied successfully to detect MP in pharmaceuticals. MP recoveries were 99.9-101.7% with a relative standard deviation (RSD) ( n = 5) of 0.59-0.77% for three synthetic samples, and 97.5-110.0% with an RSD of 0.98-2.10% ( n = 5) for tablet samples. [ABSTRACT FROM AUTHOR]

The interaction of paylean (PL) with calf thymus DNA (ctDNA) was investigated using fluorescence spectroscopy, UV absorption, melting studies, ionic strength, viscosity experiments and molecular docking under simulated physiological conditions. Values for the binding constant Ka between PL and DNA were 5.11 × 103, 2.74 × 103 and 1.74 × 103 L mol-1 at 19, 29 and 39°C respectively. DNA quenched the intrinsic fluorescence of PL via a static quenching procedure as shown from Stern-Volmer plots. The relative viscosity and the melting temperature of DNA were basically unchanged in the presence of PL. The fluorescence intensity of PL-DNA decreased with increasing ionic strength. The value of Ka for PL with double-stranded DNA (dsDNA) was larger than that for PL with single-stranded DNA (ssDNA). All the results revealed that the binding mode was groove binding, and molecular docking further indicated that PL was preferentially bonded to A-T-rich regions of DNA. The values for Δ H, Δ S and Δ G suggested that van der Waals forces or hydrogen bonding might be the main acting forces between PL and DNA. The binding distance was determined to be 3.37 nm based on the theory of Förster energy transference, which indicated that a non-radiation energy transfer process occurred. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The interactions of mapenterol with bovine serum albumin (BSA) and human serum albumin (HSA) have been investigated systematically using fluorescence spectroscopy, absorption spectroscopy, circular dichroism (CD) and molecular docking techniques. Mapenterol has a strong ability to quench the intrinsic fluorescence of BSA and HSA through static quenching procedures. At 291 K, the binding constants, Ka, were 1.93 × 103 and 2.73 × 103 L/mol for mapenterol-BSA and mapenterol-HAS, respectively. Electrostatic forces and hydrophobic interactions played important roles in stabilizing the mapenterol-BSA/has complex. Using site marker competitive studies, mapenterol was found to bind at Sudlow site I on BSA/HSA. There was little effect of K+, Ca2+, Cu2+, Zn2+ and Fe3+ on the binding. The conformation of BSA/HSA was changed by mapenterol, as seen from the synchronous fluorescence spectra. The CD spectra showed that the binding of mapenterol to BSA/HSA changed the secondary structure of BSA/HSA. Molecular docking further confirmed that mapenterol could bind to Sudlow site I of BSA/HSA. According to Förster non-radiative energy transfer theory (FRET), the distances r0 between the donor and acceptor were calculated as 3.18 and 2.75 nm for mapenterol-BSA and mapenterol-HAS, respectively. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]