ABSTRACT
A reliable and selective method was developed for the determination of bisphenol A (BPA) in drinks and fruit using dummy surface molecularly imprinted polymer (DSMIP) as a solid-phase extraction (SPE)-enrichment and separation sorbent coupled with high-performance liquid chromatography (HPLC). Tetrabromobisphenol A (TBBPA), whose structure is similar to BPA, was selected as a dummy template molecule. DSMIP has a higher selectivity for BPA than surface non-imprinted polymer (SNIP) when used as sorbents for SPE. Potential factors affecting the extraction efficiency, including conditioning, sample loading, washing and elution, and the breakthrough volume were optimised. Under the optimum experimental conditions, the recoveries of BPA in drinks and fruit were in the range from 98% to 105% with relative standard deviations (RSDs) below 7%, and a limit of detection (LOD) of 3 ng ml(-1). The developed extraction protocol eliminated the effect of template leakage on quantitative analysis and could be applied to the trace determination of BPA in complicated functional samples.
Subject(s)
Benzhydryl Compounds/analysis , Benzhydryl Compounds/toxicity , Food Contamination/analysis , Phenols/analysis , Phenols/toxicity , Solid Phase Extraction/methods , Beverages/analysis , Beverages/toxicity , Chromatography, High Pressure Liquid , Fruit/chemistry , Fruit/toxicity , Humans , Microscopy, Electron, Scanning , Microscopy, Electron, Transmission , Molecular Imprinting , Nanospheres/chemistry , Nanospheres/ultrastructure , Polybrominated Biphenyls/analysis , Polymers/chemistry , Silicon DioxideABSTRACT
Accumulating evidence has strongly suggested that amyloid fibrils of protein or peptide are cytotoxic. Fibrillar species appear to lead to disruption of cell membrane structures and thereby cause cell death. In this study, human erythrocytes were used as an in vitro model to examine the disruptive effect of lysozyme fibrils on the plasma membrane. Both the protofibrils and mature fibrils induced hemolysis and aggregation of erythrocytes. Treating ghost membranes with the fibrils resulted in aggregation of membrane proteins through intermolecular disulfide cross-linking. LC-ESI-MS/MS and Western blotting analysis showed that lysozyme fragments were incorporated into the aggregates of ghost membrane proteins, which suggested that thio-disulfide exchange among lysozyme and membrane proteins was triggered when the fibrils interacted with erythrocyte membranes. Metal-ion chelators, radical scavengers, and antioxidants had no effect on the amyloid-induced disulfide cross-linking. The exposure of interior hydrophobic residues and the increased level of solvent-accessible disulfides in the lysozyme fibrils are thought to be involved in membrane disruption. These results may unveil a novel pathway for the cytotoxicity of amyloid fibrils.
Subject(s)
Amyloid/physiology , Disulfides/metabolism , Erythrocyte Membrane/metabolism , Amino Acid Sequence , Amyloid/chemistry , Amyloid/genetics , Amyloid/ultrastructure , Animals , Cellular Senescence/physiology , Chickens , Cross-Linking Reagents/metabolism , Erythrocyte Membrane/chemistry , Erythrocyte Membrane/genetics , Erythrocyte Membrane/ultrastructure , Humans , Molecular Sequence Data , Muramidase/chemistry , Muramidase/genetics , Muramidase/physiology , Muramidase/ultrastructureABSTRACT
The interaction of BSA and NIC was investigated by absorption spectra, fluorescence spectroscopy and synchronous fluorescence spectroscopy. In the system of sodium phosphate dibasic-citric acid of 0.1 mol(-1) x L(-1), fluorescence titration showed that the fluorescence intensity of BSA at 342 nm was quenched when NIC was added, NIC was capable of binding with BSA to form a 1:1 complex and the quenching mechanism of BSA affected by NIC was shown to be a static quenching procedure by calculating the binding number n and binding constant K. NIC decreased the intensity of the characteristic absorption peak of BSA, showing that the binding of NIC to BSA had strong impact on protein conformation with the decrease in a-helical content of the protein. Synchronous fluorescence indicated that the binding of NIC to BSA is near tryptophan subunit.
