Practice question

Successful extraction of functional membrane proteins relies on preserving native fold during bilayer dissolution. Non-ionic detergents like Triton X-100, n-octyl beta-D-glucoside and n-dodecyl beta-D-maltoside possess uncharged polar heads composed of polyoxyethylene chains or sugar residues. Their aliphatic tails insert between phospholipid acyl chains disrupting lipid-lipid and lipid-protein contacts while headgroups remain non-interacting with polypeptide backbone. Mixed micelles of approximately three to five nanometers surround hydrophobic transmembrane regions, extramembranous loops remain exposed retaining secondary structure, ligand binding pockets and enzymatic active sites. Co-immunoprecipitation studies show protein-protein oligomers survive in Triton X-100. In contrast ionic detergents like sodium dodecyl sulfate bind cooperatively every two residues imparting uniform negative charge causing chain extension and random coil unfolding, destroying activity and protein interactions. Hence Triton X-100 classified as mild non-denaturing detergent preferred for raft isolation, signaling complexes and functional assays where folded state essential for downstream analysis. Preserved native state allows subsequent chromatography and functional reconstitution into liposomes for transport assays and structural studies.