Binding of triclosan to human serum albumin: insight into the molecular toxicity of emerging contaminant.

PURPOSE: The interaction between triclosan (TCS) and human serum albumin (HSA) was investigated in order to obtain the binding mechanism, binding constant, the type of binding force, the binding distance between the donor and acceptor, and the effect of TCS on the conformation change of HSA. METHODS: A HSA solution was added to the quartz cell and then titrated by successive addition of TCS. The fluorescence quenching spectra and synchronous spectra were recorded with the excitation and emission slits of the passage of band set at 10 and 20 nm. Three-dimensional fluorescence spectra of HSA were recorded before and after the addition of TCS. The capillary electrophoresis was conducted with the pressure injection mode at 0.5 psi for 5 s, separation under 25 kV, and detection at 214 nm. RESULTS: Fluorescence data indicated the fluorescence quenching of HSA by TCS was static quenching, and the quenching constants (K ( a )) were 1.14 × 10(5), 8.75 × 10(4), 6.67 × 10(4), and 5.00 × 10(4) at 293, 298, 303, and 309 K, respectively. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the interaction were calculated to be -37.9 kJ mol(-1) and 32.6 J mol(-1) K(-1). The binding distance between TCS and tryptophan residues of HSA was obtained to be 1.81 nm according to Fǒrster nonradioactive energy transfer theory. The UV-Vis absorption spectroscopy, the synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, and circular dichroism spectroscopy revealed the alterations of HSA secondary structure in the presence of TCS. Finally, the interaction between TCS and HSA was further confirmed by capillary electrophoresis. CONCLUSIONS: TCS was bound to HSA to form the TCS-HSA complex, with the binding distance of 1.81 nm. Hydrophobic interaction and hydrogen bond were dominated in the binding. TCS could change the secondary conformation of HSA. This work provides an insight into noncovalent interaction between emerging pollutants and protein, helping to elucidate the toxic mechanism of such pollutants.

Bis(µ-4-bromo-benzoato)-κO,O':O';O:O,O'-bis-[µ-1,3-bis-(pyridin-4-yl)propane-κN:N']bis-[(4-bromo-benzoato-κO,O')cadmium].

The dinuclear complex, [Cd(2)(C(7)H(4)BrO(2))(4)(C(13)H(14)N(2))(2)], lies on a twofold rotation axis crossing midway between the two metal atoms. The Cd(II) cation is seven-coordinated with a geometry that can be considered as distorted penta-gonal bipyramidal, with the N atom of the N-heterocyclic units occupying the apical sites and the O atoms of the 4-bromo-benzoate units in the equatorial plane. The middle methyl-ene group of the 1,3-bis-(4-pyrid-yl)propane ligands is located outside of the twofold rotation axis and consequently is disordered over two sites around this symmetry element with fixed occupancies factors of 0.5.

Investigation on the interaction of prulifloxacin with human serum albumin: a spectroscopic analysis.

The interaction between prulifloxacin (PUFX) and human serum albumin (HSA) was investigated under simulated physiologic conditions with fluorescence spectra. The fluorescence quenching process of HSA may be mainly governed by a static quenching mechanism. The apparent binding constant K(b) between PUFX and HSA at different temperatures were 2.08+/-1.04, 2.74+/-0.50, and 4.98+/-1.61x10(8) l/mol. The thermodynamic parameters, with a negative value of DeltaG(0), revealed that the binding is a spontaneous process. A binding distance R of 1.19 nm between donor and acceptor was obtained from the Forster energy transfer theory.

Investigation on interaction of prulifloxacin with pepsin: a spectroscopic analysis.

The interaction between prulifloxacin, a kind of new oral taking antibiotic and pepsin, a kind of enzyme in the stomach has been investigated in vitro under a simulated physiological condition by different spectroscopic methods. The intrinsic fluorescence of pepsin was strongly quenched by prulifloxacin. This effect was rationalized in terms of a static quenching procedure. The binding parameters have been evaluated by fluorescence quenching methods. The negative value of DeltaG(0) reveals that the binding process is a spontaneous process. The binding distance R between donor (pepsin) and acceptor (prulifloxacin) was obtained according to the Förster's resonance energy transfer theory and found to be 0.95 nm. The results obtained herein will be of biological significance in pharmacology and clinical medicine.

[Spectrophotometric determination of deoxyribonucleic acid by its quenching effect on acridine orange].

Based on the reaction of acridine orange with deoxyribonucleic acid (DNA), and under the optimized condition, a novel method to determine the DNA was developed with the spectrophotometry. The absorbance of acridine orange at the maximum absorption wavelength of 444 nm responded to the concentration of DNA negatively with excellent linearity. It has an upper linear limit concentration of 8.0 microg x mL(-1) and a detection limit of 0.12 microg x mL(-1) with the correlation coefficient of 0.999 8. The method is simple, rapid and sensitive, and could be applied to sample assay satisfactorily. Finally, the reaction mechanism is discussed.

[Study on determination of trace nitrite and reaction mechanism by two-wavelength negative absorption-catalytic spectrophotometry].

A new method was proposed for the determination of trace nitrite by two wavelength negative absorption catalytic spectrophotometry based on the catalysis of nitrite on the oxidation fading reaction of acridine orange by potassium bromate in phosphoricacid medium. The additive value of negative absorbances at two wavelengths was linear to the nitrite concentration in the range of 1.0 x 10(-5)-5.0 x 10(-7) mol x L(1). The method has been used to the determination of nitrite in environment water sample with satisfactory

[Multi-wavelength negative absorption fading spectrophotometry to determine trace nitrite and it's mechanism].

Using negative absorption rectifyingtechniquie, the authors investigated spectra of the reaction of nitrite with acridine yellow in 1.0 mol x dm(-3) (1 dm = 10 cm = 0.1 m) hydrochloric medium. The authors established the new dynamics method of mensuratiog trace nitrous acid radical by the negative absorption undertint spectrophotometry at multi-wavelengths, based on the linear relation between the negative absorbance value or the AT value of absorbance sum and the nitrous acid radical concetration in a certain range. The linear range was 7.2 x 10(-6) -3.6 x 10(-4) mol x dm(-3), RSD was 1.06%-3.12%, and CV (recovery) was 98.00%-100.20%. In application to the determination of nitrite in environmental water sample, satisfactory result was abtained with high accuracy, better selectivity and common ions ceasing to effect measuring. According to the change in the absorption peak value in the reactive system,the liquor acidity, the different order for added reagent, liquor temperature, reactive time, acid kind etc., the authors believe that the reaction of acridine yellow with mitrite is diazotization-coupling, under the condition of feasible pH value, temperature, and additive order of midium.

[Studies on the interaction between RNA with methyl violet and determination of RNA by spectrophotometry].

An analytical method for the determination of ribonucleic acid was established by spectrophotometry. At maximum absorption wavelength for methyl violet in the B-R buffer solution, and under the best conditions, the degree of decrease of the absorbance was linear with the amount of ribonucleic Acid. It was a new and preferable approach for the determination of ribonucleic Acids. The method with the linearity range was 1.0 to 8.0 microg x mL(-1) and the detection limit was 0.52 microg x mL(-1), and the correlation coeffient was 0.9999. This method was simple, rapid, and selective. So it was satisfactory to the application for the determination of ribonucleic Acid. The reaction mechanism was electrostatic interaction to make molecular association of RNA with methyl violet, to go on antiion permutation and bonded reaction of concert.