Anti-MRSA agent 3

Cytotoxicity assays are usually based on the assessment of cell membrane damage, which can also be indirectly detected by measuring cell viability. Detection methods include MTT assay, CKK-8 assay, LDH assay and ATP assay, etc.

Live/dead viability and cytotoxicity staining assays are based on the simultaneous detection of intracellular esterase activity in metabolically active (viable) cells and membrane integrity loss in non-viable cells. In commonly used dual-staining approaches, membrane-permeant fluorogenic substrates are converted by intracellular esterases into fluorescent products in live cells, while impermeant DNA-binding dyes selectively enter cells with compromised plasma membranes and label nucleic acids in dead or dying cells, enabling discrimination between viable and non-viable populations by fluorescence microscopy or flow cytometry.

Southern blot is a DNA hybridization assay used to detect a defined DNA sequence within restriction-digested or otherwise fragmented genomic DNA. The method separates DNA fragments by agarose gel electrophoresis, transfers the size-resolved DNA pattern onto a solid support, denatures the DNA to permit base pairing, and detects fragments that hybridize with a complementary labeled probe; the readout is a band, smear, or fragment-size distribution corresponding to the target sequence and its restriction-fragment context. The assay reflects sequence presence, restriction fragment length, gene copy pattern, structural rearrangement, insertion or deletion affecting restriction sites, and some repeat-length or terminal restriction fragment applications when the experimental design links the probe to those genomic features. Classic applications include Southern blot-based telomere terminal restriction fragment analysis and minisatellite-based DNA fingerprinting, which illustrate how the same

The following protocol uses the MTT colorimetric assay as a classic literature-established method for assessing cell viability/metabolic activity in cultured mammalian cells. MTT[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] is reduced by metabolically active cells to a colored formazan product; the amount of formazan is quantified spectrophotometrically and provides an indirect measure of metabolically active viable cells. Importantly, MTT reduction reflects cellular oxidoreductase/metabolic activity rather than an absolute direct count of living cells, so changes in cellular metabolism can alter the signal independently of cell number.