Fluorescence enhancement of the protein–curcumin–sodium dodecyl benzene sulfonate system and protein determination

Quantitative determination of proteins based on strong fluorescence enhancement in curcumin-chitosan-proteins system

We found that the fluorescence intensity of curcumin (CU) can be highly enhanced by protein bovine serum albumin (BSA) and human serum albumin (HSA) in the presence of chitosan (CTS). Based on this finding, a new fluorimetric method to determine the concentration of protein was developed. Under optimized conditions, the enhanced intensities of fluorescence are quantitatively in proportion to the concentrations of protein in range of 0.007-100 μg·mL(-1) for BSA and 0.004-100 μg·mL(-1) for HSA at 426 nm excitation, and 0.007-100 μg·mL(-1) for BSA and 0.01-100 μg·mL(-1)for HSA at 280 nm excitation, while corresponding qualitative detection limits (S/N = 3) can lower to 3.96, 2.46, 4.56, 9.20 ng·mL(-1), respectively. The method has been successfully used for the determination of HSA in real samples. Based on resonance light scattering and UV-visible absorption spectroscopic analysis, mechanism studies suggested that the highly enhanced fluorescence of CU was resulted from synergic effects of favorable hydrophobic microenvironment provided by BSA and CTS and efficient intermolecular energy transfer between BSA and CU. Protein BSA may bind to CTS through hydrogen bonds, which causes the protein conformation to convert from β-fold to α-helix. CU can combine with the BSA-CTS complex through its center carbonyl carbon, and CTS plays a key role in promoting the energy transfer process by shortening the distance between BSA and CU.

Investigation on the interaction of tetrachloride fluorescein–bovine serum albumin-β-cyclodextrin and the determination of protein by flow injection analysis

In this paper, a simple and sensitive flow injection analysis (FIA) for the determination of protein with spectroscopic probe was developed. This method was based on the investigation of the interaction of tetrachloride fluorescein (2,4,5,7-tetrachloro-3,6-fluorandiol)-bovine serum albumin (BSA), the coupling reaction of protein with tetrachloride fluorescein (TCFS) which was used as a spectroscopic probe in the presence of beta-cyclodextrin (beta-CD). The interaction mechanism and the main factors affecting the determination were investigated in details. Under the optimum conditions, the linear range and detection limit were 0.0-28.0 microg mL(-1) and 0.76 microg mL(-1), respectively. The proposed method has been used to determine albumin in serum albumin with satisfactory results.