TEMED Enhanced Photoluminescent Imaging of Human Serum Proteins by Quantum Dots After PAGE

Polyacrylamide gel electrophoresis (PAGE) has become one of the most powerful and widely used separation techniques for complex biological samples, whose traditional detection methods include organic dye or silver staining. For simple, convenient, and ultrasensitive detection of proteins after PAGE, a novel enhanced photoluminescent (PL) imaging method was developed. Thioglycolic acid (TGA)-capped CdTe quantum dots (QDs) and the enhancer reagent tetramethylethylenediamine (TEMED) were introduced, achieving the direct detection of various proteins in native 1-DE, 2-DE and SDS-PAGE. Here we describe the general protocol of TEMED enhanced PL imaging by QDs, including materials, practical procedures, and some notes.

Size Effects on the Interaction of QDs with the Mitochondrial Membrane In Vitro

The mitochondrial toxicity induced by GSH-CdTe Quantum dots (QDs) of different sizes was investigated. The decreases in absorbance and transmission electron microscopy images show that QDs induce the swelling of mitochondria. Results of flow cytometry indicate that QDs cause a reduction of mitochondrial membrane potential (MMP). A remarkable increase in fluidity of protein regions of mitochondrial membrane is observed, whereas the lipid regions are not obviously affected. Cyclosporin A (CsA) effectively prevents the QD-induced mitochondrial swelling. On the basis of these results, it is proposed that QDs induce mitochondrial permeability transition (MPT). Moreover, with increasing QDs size, a pronounced MPT is observed. The difference between the membrane fluidity induced by QDs and Cadmium ion and the ineffective protective effects of EDTA suggests that the mitochondrial toxicity of QDs cannot be only attributed to the release of metal ion. The protective effects of HSA indicate that the interaction of QDs with pore-forming protein gives rise to the increase in membrane fluidity. This hypothesis is demonstrated by the interaction of QDs with model membranes and proteins using differential scanning calorimetry and isothermal titration microcalorimetry. In conclusion, as the size of QDs increases, the binding affinity of QDs with membrane protein increases, and therefore causes a pronounced mitochondrial damage.