Qiulan Zhang

Molecular spectroscopic studies on the interaction between Ractopamine and bovine serum albumin

To investigate the interaction between Ractopamine (RAC), an animal growth promoter, and bovine serum albumin (BSA), three spectroscopic approaches (fluorescence, UV-vis and FT-IR) and three different experiments (two mole-ratio and a Jobs methods) were used to monitor the biological kinetic interaction procedure. The Stern-Volmer quenching constants K(SV), the binding constants K(a), and the number of binding sites n at 298, 301 and 304 K were evaluated by molecular spectroscopic approaches. The values of enthalpy (-13.47 kJ mol(-1)) and entropy (78.39 J mol(-1)K(-1)) in the reaction indicated that RAC bound to BSA mainly by electrostatic and hydrophobic interaction. The site markers competitive experiments indicated that the binding of RAC to BSA primarily took place in site I. The spectra data matrix was further investigated with multivariate curve resolution-alternating least squares (MCR-ALS), and the concentration profiles and the pure spectra for three species (BSA, RAC and RAC-BSA) existed in the kinetic interaction procedure, as well as the apparent equilibrium constants, were obtained.

Combined voltammetric and spectroscopic analysis of small molecule–biopolymer interactions: The levodopa and serum albumin system

An analytical method was researched for the simultaneous determination of reactants and products during the binding of important small molecules such as levodopa (LD) with biopolymers such as bovine serum albumin (BSA). Voltammetry and fluorescence spectroscopy were used to obtain the analytical profiles from different reactant mixtures as a function of concentration. This enabled the extraction of the equilibrium constants (K(SV)) which are reported for the first time. Voltammetric results supported the formation of the LD-BSA complex but not that with dopamine. Further information of the LD-BSA system was unattainable because the measured composite profiles could not be extracted. New information was obtained when the extended data matrix was resolved by the MCR-ALS method. The previously unavailable extracted voltammogram profile of LD-BSA complex indicated that the complex was electroactive; this was unexpected if the LD-BSA system was in its folded state, and hence, it was suggested that the protein must be unfolded. The observation that the drug:BSA stoichiometry was 3:1, i.e. (levodopa)(3)-BSA, supported this suggestion; these results were obtained from the MCR-ALS extracted concentration profiles for the three reaction components.

Competitive Interactions of Ionic Surfactants with Salbutamol and Bovine Serum Albumin: A Molecular Spectroscopy Study with Implications for Salbutamol in Food Analysis

The effect of ionic surfactants, sodium dodecyl sulfate (SDS) and N-cetyl-N,N,N-trimethylammonium bromide (CTAB), on the interaction between β-agonist salbutamol (SAL) and bovine serum albumin (BSA) was investigated with the use of fluorescence spectroscopy (FLS) and chemometrics methods [multivariate curve resolution-alternating least-squares (MCR-ALS) and parallel factor analysis algorithm (PARAFAC)]. It was found that the binding constant of SAL to BSA in the presence of CTAB was much larger than that without this ligand. The ligand/BSA stoichiometry was 4:1, that is, (CTAB)4-BSA, and was 2:1 with the ligand, that is, (SAL)2-BSA. These results were obtained from the concentration profiles extracted by MCR-ALS for all three reactants. Quantitative information on the complex CTAB-BSA-SAL species was obtained with the resolution of the excitation-emission fluorescence three-way data matrices by PARAFAC. This research has implications for the analysis of SAL in food and might be performed in laboratories associated with organizations such as the U.S. Food and Drug Administration (FDA) and the International Olympic Committee (IOC).

Binding Interaction of Dopamine with Bovine Serum Albumin: A Biochemical Study

ABSTRACT The binding interaction of bovine serum albumin (BSA) with dopamine was studied by different spectroscopic techniques, and a fluorescence quenching mechanism was associated with this process. Estimated thermodynamic parameters indicated the presence of hydrogen bonding and van der Walls forces between dopamine and BSA. The microenvironment of the protein-binding site was studied by the synchronous fluorescence, FT-TR, and three-way fluorescence techniques in the presence of dopamine, and changes in conformation were indicated within the binding cavity. This study provides useful information on the transportation and distribution of dopamine in proteins.

Analysis of Complex Molecular Systems: The Impact of Multivariate Analysis for Resolving the Interactions of Small Molecules with Biopolymers – a Review

This review is focused on the impact of chemometrics for resolving data sets collected from investigations of the interactions of small molecules with biopolymers. These samples have been analyzed with various instrumental techniques, such as fluorescence, ultraviolet–visible spectroscopy, and voltammetry. The impact of two powerful and demonstrably useful multivariate methods for resolution of complex data—multivariate curve resolution–alternating least squares (MCR–ALS) and parallel factor analysis (PARAFAC)—is highlighted through analysis of applications involving the interactions of small molecules with the biopolymers, serum albumin, and deoxyribonucleic acid. The outcomes illustrated that significant information extracted by the chemometric methods was unattainable by simple, univariate data analysis. In addition, although the techniques used to collect data were confined to ultraviolet–visible spectroscopy, fluorescence spectroscopy, circular dichroism, and voltammetry, data profiles produced by other techniques may also be processed. Topics considered including binding sites and modes, cooperative and competitive small molecule binding, kinetics, and thermodynamics of ligand binding, and the folding and unfolding of biopolymers. Applications of the MCR–ALS and PARAFAC methods reviewed were primarily published between 2008 and 2013.

The use of DNA self-assembled gold nano-rods for novel analysis of lead and/or mercury in drinking water

A novel, uncomplicated method for the analysis of lead (Pb2+) and mercury (Hg2+) ions has been developed with the use of gold nano-rods (AuNRs), which were combined with ssDNA. The AuNR–ssDNA assembly was stabilized by electrostatic interactions. The ssDNA has a random coil structure, which was changed to G-quartet and hairpin-like structures after binding with Pb2+ and Hg2+ ions, respectively. The bonding with lead and mercury caused the ssDNA assembled AuNRs (ssDNA–AuNRs) to disperse, and this increased the surface plasmon resonance (SPR) absorption of the AuNRs. Changes in the UV-vis spectral intensities allowed the selective detection of Pb2+ and Hg2+ ions at concentrations as low as 19.8 nM and 3.2 nM, respectively. Linear correlations were observed between the UV-vis spectra and the Pb2+ and Hg2+ analytes in the concentration ranges of 25–250 nM (R2 = 0.9971) for Pb2+ and 4–40 nM (R2 = 0.9956) for Hg2+, respectively. The literature suggests that the novel method is another example in which the ssDNA–AuNR assembly has been used for trace analysis of Pb2+ and Hg2+.