Counterion-dependent excitonic spectra of tetra(p-carboxyphenyl)porphyrin aggregates in acidic aqueous solution

The interaction of 2-hydroquinone-5,10,15,20-tetra(p-hydroxyphenyl)porphyrin with surfactants: solubilization and J-aggregates

J-aggregates of 2-hydroquinone-5,10,15,20-tetra(p-hydroxyphenyl)porphyrin (HQTHPP) induced by N-lauroyl sarcosine (SKL) in aqueous neutral solutions have been studied by optical absorption, fluorescence, and resonance light-scattering spectroscopies. As SKL concentration increases, the spectra evolve to reveal the presence of four independent species with relative concentration. The most important species is J-aggregates. The J-aggregates have two strong exciton bands corresponding to the B-band and Q-bands of HQTHPP monomers, and are found to be stable when the surfactant concentration is below 8.0 mmol/L. But above 8.0 mmol/L, the J-aggregates dissolve gradually into another species: porphyrin monomers. The total fluorescence of HQTHPP is quenched due to the aggregate formation. A strong and sharply peaked resonance light-scattering signal (>1800 counts/s, centered at 490 nm) is observed just slightly to the red of the J-aggregate absorption maximum. In the case of cetyltrimethyl-ammonium bromide, increasing surfactant concentrations have only shown to favor solubilization of porphyrin monomers. Evidently, the nature of polar headgroups of surfactants influences the tendency of THPP to aggregate.

pH-Dependent reversible transformation of TPPS4 anchored on mesoporous TiO2 film between monomers and J-aggregates

Protonated TPPS4 monomer and its J-aggregate were formed simultaneously from TPPS4 adsorbed through its sulfonic acid groups on TiO2 porous film by decreasing the pH of the surrounding water and this behavior on TiO2 film can be reversibly repeated depending on pH, indicating a flexible and stable arrangement of TPPS4 through chemical bonds between the sulfonic acid groups and the TiO2 surface.

Protein analysis with tetra-substituted sulfonated cobalt phthalocyanine by the technique of Rayleigh light scattering

This is the first report of cobalt-tetrasulfonatophthalocyanine (CoTSPc) as a probe of Rayleigh light scattering (RLS) to determine proteins at nanogram levels. A highly sensitive method has been developed for the determination of proteins by the light scattering technique on a common spectrofluorimeter, based on the fact that the weak RLS of CoTSPc can be greatly enhanced in the presence of proteins. Under optimum conditions, the linear ranges of the calibration curves were 0.10-34.3 microg x mL(-1) for both human serum albumin and bovine serum albumin, with detection limits of 15.5 and 13.9 ng x mL(-1), respectively. Moreover, there is almost no interference of any amino acids and metal ions. The method has been applied to the direct determination of total proteins in human serum samples, and the results were satisfactory with clinical data provided.

Resonance light scattering imaging detection of proteins with α,β,γ,δ-tetrakis(p-sulfophenyl)porphyrin

A resonance light scattering (RLS) imaging technique was introduced to measure the light scattering of aggregation species induced by proteins, and thus a method of detecting proteins in the range of picograms was proposed. In acidic medium, J-aggregation of alpha,beta,gamma,delta-tetrakis(p-sulfophenyl)porphyrin (TPPS(4)) in the presence of proteins occurs, resulting in strong RLS signals characterized at 490 nm. Under the excitation of a 488-nm light beam of argon ion laser source, the scattered light of single J-aggregation species could be observed with a common microscope, and the images could be captured with a cooled charge-coupled device camera. Data analysis for the digital images showed that the counts of aggregate species in the detection focus plane are proportional to the concentration of proteins in picograms. When 1.0 x 10(-7)M TPPS(4) was employed, 0.01-210 ng/ml bovine serum albumin and human serum albumin could be detected with limits of detection lower than 10 pg/ml (3 sigma). Three human blood serum samples were satisfactorily detected with relative standard deviations lower than 3.04%.