Total internal reflection resonance light scattering at solid/liquid interfaces.

Total internal reflection (TIR) technique is an interface-specific tool and resonance light scattering (RLS) is of high sensitivity. The combination of both approaches is introduced into the solid/liquid interface for the first time. The behaviors of mixture of TPPS and BSA at the interface have been studied with total internal reflection resonance light scattering (TIR-RLS). The preliminary experimental results indicate that TIR-RLS is a good approach to study the interaction and distinguish the states of macromolecules at the solid/liquid interface.

Adsorption of a protein-porphyrin complex at a liquid-liquid interface studied by total internal reflection synchronous fluorescence spectroscopy.

Interfacial analysis has attracted more and more attention owing to its fundamental and biological importance. Total internal reflection fluorescence (TIRF) spectroscopy is a useful method to study interfacial properties. The synchronous scanning fluorescence technique provides a selective tool to analyze a specific component in a complex system. The interaction and adsorption of bovine serum albumin (BSA) and meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) at toluene-water interface were studied successfully by the coupling technique of total internal reflection synchronous fluorescence (TIRSF). New methods are provided for the determination of the critical micelle concentration (cmc), apparent adsorption equilibrium constant (K(ad)) and maximum amount of adsorption (f(max)) at the liquid-liquid interface. The results indicated that BSA could adsorb onto the toluene-water interface as a complex of BSA-TPPS in a ratio of 1:1 ratio based on Langmuir adsorption isothermal model. The cmc, apparent K(ad) and f(max) for BSA at pH 3.1 were determined to be 1.0 x 10(-4) mol L(-1), 1.15 x 10(5) L mol(-1) and 1.14 x 10(-9) mol cm(-2), respectively.

Total internal reflection fluorescence spectroscopy for investigating the adsorption of a porphyrin at the glass/water interface in the presence of a cationic surfactant below the critical micelle concentration.

Total internal reflection fluorescence (TIRF) spectroscopy was used to investigate the adsorption behavior of meso-tetrakis(p-sulfonatophenyl)porphyrin (TPPS) at the glass/water interface in the presence of a cationic surfactant (cetyltrimethylammonium bromide, CTAB) far below the critical micelle concentration. The adsorption model of TPPS at the glass/water interface in the presence of low concentration of CTAB was proposed, which was different from the adsorption of TPPS in the presence of micelles of CTAB at the glass/water interface. TPPS and CTAB did not form stable complex at the interface in dilute system. The interfacial species of TPPS were analyzed by comparing the spectra of TPPS at the glass/water interface and in the aqueous phase. The influences of the TPPS concentration, the CTAB concentration, and the pH values on the interfacial fluorescence spectra and intensities were studied. It was demonstrated that electrostatic interaction and hydrophobicity performed an important role on the adsorption of TPPS in the presence of CTAB. The different effects of TPPS concentration on the adsorption behaviour of TPPS at different pH were observed for the first time. It was found that the adsorption isotherms of TPPS at glass/water interface could fit Freundlich equation at pH 7.1.

Fluorescence spectral properties of rhodamine 6G at the silica/water interface.

In this work, total internal reflection synchronous fluorescence spectroscopy (TIRSF) is applied successfully to investigate rhodamine 6G (R6G) at the silica/water interface. In comparison with the bulk spectra, 5 nm red shift is observed in the interface spectra, which is mainly due to the limitation of freedom of rotational movement of R6G molecules at the interface. The increase of R6G concentration induces the self-quenching of adsorbate at the interface. The dependence of interfacial fluorescence on the acidity and ionic strength was studied. Both the acidity and ionic strength affect the adsorptive behaviors of R6G at the silica/water interface.

[Determination of protein with TPPS by total internal reflection synchronous fluorescence spectroscopy].

A new method of quantitative determination for serum albumin in aqueous solution has been developed by measuring total internal reflection synchronous fluorescence at the solid/liquid interface. The combination of bovine serum album in (BSA) and mesotetrakis (4-sulphonatophenyl) porphyrin (TPPS) adsorbed onto the glass surface produced a synchronous fluorescence signal at 421 nm. At pH 4.25, the signal intensity of BSA adsorbed on the interface was proportional to the BSA concentration in bulk solution. The linear range of 1.0-8.0 microg x mL(-1) and the detection limit of 0.94 microg x mL(-1) were obtained. The human serum samples were determined with satisfactory results.