The fluorescence enhancement of the protein adsorbed on the surface of Ag nanoparticle.

The fluorescence enhancement of the BSA adsorbed on the surface of Ag nanoparticles is reported, where non-fluorescent collagen is used as the separator between the BSA and Ag nanoparticles. The study indicates that Ag nanoparticles can enhance the fluorescence of the BSA, especially the fluorescence of the tyrosine residues with lower quantum. Three types of Ag nanoparticles are evaluated including Ag island film, Ag colloids and fractal Ag electrode. Of them Ag island film is the best. The investigation suggests that the fluorescence enhancement of the BSA is related to the adsorption of the BSA on the surface of Ag island film through the hydrophobic interaction, while the collagen can promote the adsorption of the BSA on the surface of Ag island film and change its conformation, resulting in the interaction between BSA and Ag island film.

Fluorescence enhancement effect of morin-nucleic acid-L-cysteine-capped nano-ZnS system and the determination of nucleic acid.

It is found that L-cysteine-capped nano-ZnS can further enhance the fluorescence intensity of the morin-nucleic acid system. Under optimum conditions, the enhanced intensity of fluorescence is proportional to the concentration of nucleic acid in the range of 7.0 x 10(-8)-1.0 x 10(-5) g mL(-1) for fish sperm DNA (fsDNA) and 9.0 x 10(-8)-5.0 x 10(-6) g mL(-1) for yeast RNA (yRNA). The corresponding detection limits (S/N = 3) are 2.0 x 10(-8) g mL(-1) and 4.0 x 10(-8) g mL(-1), respectively. The interaction mechanisms of morin-nucleic acid-L-cysteine-capped nano-ZnS system are studied by multiple techniques. It is considered that there exists synergistic effects of groove binding and electrostatic interaction between morin, L-cysteine-capped nano-ZnS and nucleic acid, and the complex of morin-L-cysteine-capped nano-ZnS-nucleic acid is formed.

Study on the interaction between oxolinic acid aggregates and protein and its analytical application.

It was found that oxolinic acid (OA) at high concentration can self-assemble into nano- to micro-meter scale OA aggregates in Tris-HCl (pH 7.48) buffer solution. The nanoparticles of OA were adopted as fluorescence probes in the quantitative analysis of proteins. Under optimum conditions, the fluorescence quenching extent of nanometer scale OA aggregates was in proportion to the concentration of albumins in the range of 3.0x10(-8) to 3.0x10(-5) g mL(-1) for bovine serum albumin (BSA) and 8.0x10(-8) to 8.0x10(-6) g mL(-1) for human serum albumin (HSA). The detection limits (S/N=3) were 3.4x10(-9) g mL(-1) for BSA, and 2.6x10(-8) g mL(-1) for HSA, respectively. Samples were satisfactorily determined. The interaction mechanism of the system was studied using fluorescence, UV-vis, resonance light scattering (RLS) and transmission electron microscope (TEM) technology, etc., indicating that the nonluminescent complex was formed between serum albumin molecular and OA, to disaggregate the self-association of OA, which resulted in the dominated static fluorescence quenching in the system.

Investigation of the interaction between curcumin and nucleic acids in the presence of CTAB.

It is found that nucleic acid can enhance the resonance light scattering (RLS) enhancement effect of curcumin (CU) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The investigation indicates that in BR (pH 4.3) buffer, both the positive CTAB and negative yeast RNA (yRNA) combine and form a positive large association, then which is bound on the two carbon atoms of the carbonyls of CU through hydrogen bond and hydrophobic force and form CU-CTAB-yRNA ternary complex, resulting in the RLS enhancement of this system. Based on it, a sensitive method for determination of nucleic acids at ngml(-1) is established.