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The interaction of aspirin and ibuprofen with bovine serum albumin (BSA) was studied by spectrofluorimetry under simulated physiological conditions. Both aspirin and ibuprofen quenched the intrinsic fluorescence of BSA and the binding ratios obtained were 2 : 1 for aspirin–BSA and 3 : 1 for ibuprofen–BSA interactions, respectively. The thermodynamic parameters (ΔH, ΔSand ΔG) obtained from the fluorescence spectroscopy data showed that the binding of aspirin to BSA involved van der Waals interactions and hydrogen bonds. Competitive experiments using warfarin and diazepam as site markers indicated that aspirin was mainly located in the hydrophobic pocket of site II of the protein as well as to a small extent in site I. Furthermore, the competitive interaction of the aspirin and ibuprofen with BSA, which was studied with the use of the three-way excitation–emission fluorescence spectra and a parallel factor analysis (PARAFAC) chemometrics method, showed that the competitive effect of ibuprofen was stronger than that of aspirin, i.e.the former molecule replaced the aspirin from the aspirin–BSA complex. [ABSTRACT FROM AUTHOR]

This work is concerned with the research and development of methodology for analysis of complex mixtures such as pharmaceutical or food samples, which contain many analytes. Variously treated samples (swill washed, fried and scorched) of the Rhizoma atractylodis macrocephalae(RAM) traditional Chinese medicine (TCM) as well as the common substitute, Rhizoma atractylodis(RA) TCM were chosen as examples for analysis. A combined data matrix of chromatographic 2-D HPLC-DAD-FLD (two-dimensional high performance liquid chromatography with diode array and fluorescence detectors) fingerprint profiles was constructed with the use of the HPLC-DAD and HPLC-FLD individual data matrices; the purpose was to collect maximum information and to interpret this complex data with the use of various chemometrics methods e.g.the rank-ordering multi-criteria decision making (MCDM) PROMETHEE and GAIA, K-nearest neighbours (KNN), partial least squares (PLS), back propagation-artificial neural networks (BP-ANN) methods. The chemometrics analysis demonstrated that the combined 2-D HPLC-DAD-FLD data matrix does indeed provide more information and facilitates better performing classification/prediction models for the analysis of such complex samples as the RAM and RA ones noted above. It is suggested that this fingerprint approach is suitable for analysis of other complex, multi-analyte substances. [ABSTRACT FROM AUTHOR]

β-Agonists such as ractopamine (RAC) and clenbuterol (CLEN), have similar effects as anabolic steroids i.e.they promote growth of muscular tissue and reduce body fat. They have been used successfully with animals and humans but have also been banned in many countries principally, because of their serious side effects. However, their illegal use persists. Thus, their interaction with biomolecules such as bovine serum albumin (BSA) is of significance, especially the co-operative reaction of mixed ligands with the protein. Fluorescence and UV-vis spectra of complex mixtures of individual ligands, binary and ternary complexes with BSA resulted in significantly overlapping spectral profiles. Qualitative and quantitative information about the various complex ligand-protein species formed, was obtained with the resolution of the excitation-emission fluorescence three-way data matrices by chemometrics methods-MCR-ALS and PARAFAC. Individual spectra of the ligands, their binary complexes with BSA and their ternary complexes were extracted, and quantitative concentration profiles for each species in a particular interaction were constructed. Such analyses made it possible to interpret the role and behaviour of each reaction component. It was found that both ligands, RAC and CLEN, bound co-operatively in site I of the BSA. This was confirmed with the use of site markers such as warfarin (site I) and ibuprofen (site II). However, CLEN formed a 1:1 CLEN-BSA complex, while RAC formed a 2:1 RAC2-BSA binary species. Interestingly, when CLEN or RAC was added to RAC2-BSA or CLEN-BSA, respectively, ternary complexes were produced such as RAC2-BSA-CLEN. Significantly, the presence of the second ligand in such an interaction in excess, appeared to increase the affinity of the added ligand for BSA. This may have consequences on the amount of steroid required to achieve a desired tissue growth effect. [ABSTRACT FROM AUTHOR]

Three commonly used fluoroquinolone antibiotics (norfloxacin (NFX), ofloxacin (OFX) and lomefloxacin (LMFX)) were used as examples of molecules which can interact with a biomacromolecule, such as DNA, separately or in a mixture. Such interactions were investigated with the use of UV and Synchronous Fluorescence Spectroscopy (SFS). Equilibrium binding (Kap) and Stern–Volmer equilibrium (KSV) constants were extracted from these two types of spectra from interactions of DNA with single fluoroquinolones. The values of these equilibrium constants were relatively low, and this suggested that the DNA groove was the likely binding site. The complex SFS profiles obtained from the interactions of the DNA with the drug analyte mixtures were resolved, with the use of the curve resolution method, parallel factor (PARAFAC) analysis, into spectra of individual drugs. From these spectra, the (KSV) values for the individual analytes in the mixture were obtained. Also extracted were the concentrations of the individual quinolones as a function of concentration of the DNA. From a comparison of the equilibrium constants for the individual drug–DNA interaction with those obtained from the interaction with the drugs in a mixture, it was found that the binding strength of a single analyte to DNA was LMFX > NFX > OFX, but when the drug mixture was involved, this order was reversed. Importantly, it was also found that the equilibrium uptake of the drugs OFX and NFX was higher than from single drug–DNA experiments; the concentrations of LMFX did not change significantly. These observations collectively suggested that the binding of NFX and OFX to DNA is synergistically affected and that they probably share similar binding sites, while the LMFX was bound to a different site. This new important qualitative and quantitative information, which can now act as a springboard for more complex and deeper studies of the apparent synergistic effects of drug interactions with biomacromolecules, could only be obtained by the combination of three-way array SFS measurements and their interpretation by a chemometrics curve resolution method such as PARAFAC. [ABSTRACT FROM AUTHOR]