Development of a direct and sensitive detection method for DNA-binding proteins based on electrophoretic mobility shift assay and iodoacetamide derivative labeling

Modification-free amperometric biosensor for the detection of wild-type p53 protein based on the in situ formation of silver nanoparticle networks for signal amplification

Sensitive and accurate quantification of wild-type p53 protein is of great importance for biological research and clinical diagnosis. Herein, a modification-free amperometric biosensor was proposed for sensitive detection of wild-type p53 protein by the signal amplification of silver nanoparticles (AgNPs) networks formed in situ on electrode surface. Double-stranded DNA (dsDNA) probe containing two consensus sites was immobilized on gold electrode surface to capture wild-type p53 protein. The cysteine thiol and amine groups on the exterior of the protein allowed for the attachment of bare AgNPs through the AgS or AgN interactions. Meanwhile, benzene-1,4-dithiol (BDT) molecules in solution triggered the assembly of more AgNPs on electrode surface through the AgS interactions, thus leading to the in situ formation of AgNPs networks for signal amplification. The target at the concentration as low as 0.1 pM can be readily determined. This method was further applied to determine wild-type p53 protein in spiked human serum and cell lysates with satisfactory results. Moreover, the biosensor is regenerative and does not require the modification of AgNPs with recognition element for signal readout. The modification-free strategy can potentially be applied to develop novel biosensors for detection of other biological macromolecules.

Sensitive chemiluminescence detection of wild-type p53 protein captured by surface-confined consensus DNA duplexes

A novel chemiluminescence (CL) biosensor for sensitive detection of wild-type p53 protein has been proposed. The wild-type p53 protein in solution was captured by highly specific consensus double-stranded (ds) oligonucleotides (ODNs) preimmobilized onto a gold plate. The cysteine residues on the exterior of the wild-type p53 molecules were then derivatized with N-biotinoyl-N'-(6-maleimidohexanoyl) hydrazide (biotin-Mi) for the attachment of streptavidin-horseradish peroxidase (SA-HRP) complex. The attached HRP molecules could catalyze the CL reaction between luminol and H2O2, producing an enhanced CL signal. The CL intensity was dependent on the surface coverage of the HRP molecules, which was related to the concentration of wild-type p53 protein. Under the optimal experimental conditions, the CL intensity increased linearly with the concentration of wild-type p53 protein from 0.01 to 0.5nM. The detection limit was estimated to be 3.8pM. The proposed method has been successfully utilized for the assay of wild-type p53 protein in normal and cancer cell lysates. The sensing protocol is sensitive, cost-effective, and holds great promise for clinical diagnosis.

Differential effects of iodoacetamide and iodoacetate on glycolysis and glutathione metabolism of cultured astrocytes

Iodoacetamide (IAA) and iodoacetate (IA) have frequently been used to inhibit glycolysis, since these compounds are known for their ability to irreversibly inhibit the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). However, the consequences of a treatment with such thiol reagents on the glutathione (GSH) metabolism of brain cells have not been explored. Exposure of astroglia-rich primary cultures to IAA or IA in concentrations of up to 1 mM deprived the cells of GSH, inhibited cellular GAPDH activity, lowered cellular lactate production and caused a delayed cell death that was detectable after 90 min of incubation. However, the two thiol reagents differed substantially in their potential to deprive cellular GSH and to inhibit astrocytic glycolysis. IAA depleted the cellular GSH content more efficiently than IA as demonstrated by half-maximal effects for IAA and IA that were observed at concentrations of about 10 and 100 μM, respectively. In contrast, IA was highly efficient in inactivating GAPDH and lactate production with half-maximal effects observed already at a concentration below 100 μM, whereas IAA had to be applied in 10 times higher concentration to inhibit lactate production by 50%. These substantial differences of IAA and IA to affect GSH content and glycolysis of cultured astrocytes suggest that in order to inhibit astrocytic glycolysis without substantially compromising the cellular GSH metabolism, IA – and not IAA – should be used in low concentrations and/or for short incubation periods.

Electrophoretic mobility shift assays for the analysis of DNA-protein interactions

Electromobility shift assay is a simple, efficient, and rapid method for the study of specific DNA-protein interactions. It relies on the reduction in the electrophoretic mobility conferred to a DNA fragment by an interacting protein. The technique is suitable to qualitative, quantitative, and kinetic analyses. It can also be used to analyze conformational changes.