Amphipols

Amphipols (a portmanteau of amphiphilic polymers) are a class of amphiphilic polymers designed to keep membrane proteins soluble in water without the need for detergents, which are traditionally used to this end but tend to be denaturing.^[1] Amphipols adsorb onto the hydrophobic transmembrane surface of membrane proteins thanks to their hydrophobic moieties and keep the complexes thus formed water-soluble thanks to the hydrophilic ones.^[2] Amphipol-trapped membrane proteins are, as a rule, much more stable than detergent-solubilized ones, which facilitates their study by most biochemical and biophysical approaches.^[3][4][5] Amphipols can be used to fold denatured membrane proteins to their native form^[6][7] and have proven particularly precious in the field of single-particle electron cryo-microscopy (cryo-EM; see e.g. ^[8][9]).The properties and uses of amphipols and other non-conventional surfactants are the subject of a book by Jean-Luc Popot.^[10]