Huifeng Zhou

Binding studies of terbutaline sulfate to calf thymus DNA using multispectroscopic and molecular docking techniques

The interaction of terbutaline sulfate (TS) with calf thymus DNA (ctDNA) were investigated by fluorescence quenching, UV-vis absorption, viscosity measurements, ionic strength effect, DNA melting experiments and molecular docking. The binding constants (Ka) of TS to ctDNA were determined as 4.92×10(4), 1.26×10(4) and 1.16×10(4) L mol(-1) at 17, 27 and 37 °C, respectively. Stern-Volmer plots suggested that the quenching of fluorescence of TS by ctDNA was a static quenching. The absorption spectra of TS with ctDNA revealed a slight blue shift and hyperchromic effect. The relative viscosity ctDNA was hardly changed by TS, and melting temperature varied slightly. For the system of TS-ctDNA, the intensity of fluorescence decreased with the increase of ionic strength. Also, the Ka for TS-double stranded DNA (dsDNA) was clearly weaker than that for TS-single stranded DNA (ssDNA). All these results revealed that the binding mode of TS with ctDNA should be groove binding. The enthalpy change and entropy change suggested that van der Waals force or hydrogen bonds was a main binding force between TS and ctDNA. Furthermore, the quantum yield of TS was measured by comparing with the standard solution. Based on the Förster energy transference theory (FRET), the binding distance between the acceptor and donor was calculated. Molecular docking showed that TS was a minor groove binder of ctDNA and preferentially bound to A-T rich regions.

Using gold nanoparticles as probe for detection of salmeterol xinafoate by resonance Rayleigh light scattering

The paper explores the method of determination of salmeterol xinafoate at nanogram level with gold nanoparticles (AuNPs) probe, to measure the intensity of resonance Rayleigh light scattering (RLS) by a common spectrofluorometer. The RLS intensity of salmeterol xinafoate was greatly enhanced by AuNPs, with the maximum scattering peak at 357 nm. The salmeterol xinafoate was determined basing on the binding of salmeterol xinafoate to AuNPs by electrostatic adsorption. Under the optimum conditions, the enhanced RLS intensity was directly proportional to the concentration of salmeterol xinafoate in the range of 0.054-6.038 μg mL(-1) with a good linear relationship (r=0.9928). The limit of detection (LOD) was 9.48 ng mL(-1). The interference tests were performed carefully. With the proposed method, the synthetic samples were analyzed satisfactorily, the recovery and RSD were 102.5-103.0% and 0.67-1.0% respectively.

Characterization of the binding of neomycin/paromomycin sulfate with DNA using acridine orange as fluorescence probe and molecular docking technique

The binding of neomycin sulfate (NS)/paromomycin sulfate (PS) with DNA was investigated by fluorescence quenching using acridine orange (AO) as a fluorescence probe. Fluorescence lifetime, FT-IR, circular dichroism (CD), relative viscosity, ionic strength, DNA melting temperature, and molecular docking were performed to explore the binding mechanism. The binding constant of NS/PS and DNA was 6.70 × 103/1.44 × 103 L mol−1 at 291 K. The values of ΔHθ, ΔSθ, and ΔGθ suggested that van der Waals force or hydrogen bond might be the main binding force between NS/PS and DNA. The results of Stern–Volmer plots and fluorescence lifetime measurements all revealed that NS/PS quenching the fluorescence of DNA–AO was static in nature. FT-IR indicated that the interaction between DNA and NS/PS did occur. The relative viscosity and melting temperature of DNA were almost unchanged when NS/PS was introduced to the solution. The fluorescence intensity of NS/PS–DNA–AO was decreased with the increase in the ionic strength. For CD spectra of DNA, the intensity of positive band at nearly 275 nm was decreased and that of negative band at nearly 245 nm was increased with the increase in the concentration of NS/PS. The binding constant of NS/PS with double-stranded DNA (dsDNA) was larger than that of NS/PS with single-stranded DNA (ssDNA). From these studies, the binding mode of NS/PS with DNA was evaluated to be groove binding. The results of molecular docking further indicated that NS/PS could enter into the minor groove in the A–T rich region of DNA.

Assembly of AuNRs and eugenol for trace analysis of eugenol using resonance light scattering technique

A new resonance light scattering (RLS) method for determining eugenol was developed using gold nanorods (AuNRs) as probes which were synthesized in our lab. The weak RLS intensity of eugenol was obviously enhanced by the use of AuNRs. All of the results from the SEM, RLS and UV spectra indicated that eugenol induced the assembly of AuNRs; thus, a new complex of AuNRs-eugenol was formed. The assembly of this new complex was achieved through a coordination bond between eugenol and AuNRs. Under optimum experimental conditions, a direct linear relationship was established between the enhancement of RLS intensity and the concentration of eugenol in the range of 0.043-10.60 μg ml(-1) (r=0.9927). Moreover, the limit of detection (LOD) was found at a nanogram level (7.28 ng ml(-1) by 3S0/S). The recovery and RSD (n=5) of three synthetic samples were 99.7-104.2% and 0.81-1.19%, respectively. The method was successfully employed for the analysis of eugenol in curry powder samples.

Resonance light scattering spectroscopy of procyanidin–CPB–DNA ternary system and its potential application

A new method for the determination of calf thymus DNA at nanogram level was proposed based on the enhanced resonance light scattering (RLS) signals of DNA in the presence of procyanidin and cetylpyridinium bromide dihydrate (CPB). Under the experimental conditions, the RLS intensity of DNA at 291.0 nm was greatly enhanced by procyanidin-CPB at pH 7.0. There was a good linear relationship (r=0.9993) between the enhanced RLS intensity (ΔI(RLS)) and DNA concentration of 0.0084-3.36 μg mL(-1). The limit of detection (LOD) was 2.27 ng mL(-1) (3S0/S). Three synthetic DNA samples were measured with satisfactory, and the recovery was 102.3-107.2%.

Interaction of dextromethorphan hydrobromide with DNA: multispectral, voltammetric, and molecular docking technology

DNA is the carrier of hereditary information and gene expression of proteins and enzymes, which play an extremely important role in the process of human life. In recent years, considerable attention has been paid to the study of the interaction between small molecules and DNA, especially for interpreting the functional mechanism and designing better and more effective drugs with fewer side effects (Huang, Wang, & Guo, 2010). The study of the interactions of various small molecules with DNA has been of great interest for a long time. Small molecules bind to DNA primarily through three modes: electrostatic binding, groove binding, and intercalation binding. Electrostatic binding occurs along the exterior of the DNA helix and does not possess selectivity. Groove binding is small molecules binding to the deep major groove or minor groove of the helix of DNA. Intercalation binding is small molecules intercalating into the two adjacent base pairs of DNA. The study of a drug binding to its target molecule DNA is of considerable importance. DNA-binding drugs have been reported to be able to interfere in a sequence dependent manner with biological functions such as topoisomerase activity, restriction of enzyme cleavage of DNA, protein-DNA interactions, and the activity of transcription factors, leading to alteration of gene expression. Dextromethorphan hydrobromide (DH, (+)-3-methoxy-17-methyl-(9α, 13α, 14α) -morphinan) is the isomer of levorphanol, a codeine analog. DH is an effective and widely used phenanthrene-derived antitussive drug, which has a central action on the cough center in the medulla and was used in the treatment of respiratory disorders. However, when exceeding labelspecified maximum dosages, DH acts as a dissociative hallucinogen as an N-methyl-d-aspartate receptor antagonist (Banken & Foster, 2008). Up to now, few papers on the study of interaction of DH with DNA have been reported. In this work, the interaction between DH and DNA was investigated by fluorescence (fluorescence quenching and time-resolved fluorescence), FT-IR, and CD along with viscosity measurements, DNA melting studies, voltammetric studies, and molecular docking. It might be the first report on the DH binding with DNA to our knowledge. In the absence of expensive and intricate instruments, the mode of binding of DH to DNA was inferred. Furthermore, this study does not need any probe and what it displayed was the direct interaction between DH and DNA in vitro. The work is expected to provide some useful information for better understanding the mechanism of action of DH in organism at molecular level.

Study on the interactions of mapenterol with serum albumins using multi-spectroscopy and molecular docking.

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 × 10(3) and 2.73 × 10(3) 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(+), Ca(2+), Cu(2+), Zn(2+) and Fe(3+) 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.

Micronomicin/tobramycin binding with DNA: fluorescence studies using of ethidium bromide as a probe and molecular docking analysis

Two aminoglycosides, micronomicin (MN), and tobramycin (TB), binding with DNA were studied using various spectroscopic techniques including fluorescence, UV–Vis, FT-IR, and CD spectroscopy coupled with relative viscosity and molecular docking. Studies of fluorescence quenching and time-resolved fluorescence spectroscopy all revealed that MN/TB quenching the fluorescence of DNA–EB belonged to static quenching. The binding constants and binding sites were obtained. The values of ΔH, ΔS, and ΔG suggested that van der Waals force or hydrogen bond might be the main binding force. FT-IR and CD spectroscopy revealed that the binding of MN/TB with DNA had an effect on the secondary structure of DNA. Binding mode of MN/TB with DNA was groove binding which was ascertained by viscosity measurements, CD spectroscopy, ionic strength, melting temperature (Tm), contrast experiments with single stranded (ssDNA), and double stranded DNA (dsDNA). Molecular docking analysis further confirmed that the groove binding was more acceptable result.

Characterization of the binding of paylean and DNA by fluorescence, UV spectroscopy and molecular docking techniques

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 × 10(3) , 2.74 × 10(3) and 1.74 × 10(3)  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 ΔH, ΔS and ΔG 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