Practice question

Detergent physicochemical properties determine permeabilization without denaturation. Triton X-100 tert-octylphenyl polyethoxyethanol consists of hydrophobic tert-octylphenol moiety and hydrophilic polyoxyethylene chain averaging nine to ten units, conferring CMC near zero point two four millimolar, aggregation number about one hundred to one fifty and micellar weight around ninety kilodalton. It partitions efficiently into phospholipid bilayers increasing permeability to macromolecules like antibodies and substrates, forming mixed micelles that solubilize lipids while protein-protein electrostatic contacts and hydrophobic core packing of soluble domains remain undisturbed because headgroup uncharged does not bind backbone cooperatively. SDS anionic twelve-carbon sulfate displays low CMC but strong cooperative binding unfolding helices and beta sheets into rodlike micelles. Sodium deoxycholate bile salt anionic steroid forms smaller micelles relatively harsh. For gentle permeabilization preserving enzyme activity, antigenicity and protein complexes, Triton X-100 remains laboratory standard, explaining identification as membrane-permeable non-denaturing detergent distinct from ionic denaturants used for SDS-PAGE. Quantitative assessment of protein activity after extraction confirms retention of ligand binding and catalytic turnover essential for biochemical characterization.