Thiolation of preformed liposomes with iminothiolane

Abstract
Preformed phosphatidylethanolamine‐containing liposomes were thiolated with 2‐iminothiolane (Traut's reagent) and subsequently activated by mixed disulfide formation with 5,5′‐dithiobis(2‐nitrobenzoic acid). Up to 65% of amino groups of the outer liposomal lamella, corresponding to 230 SH‐groups per vesicle, were modified. Covalent attachment of thiolated α‐chymotrypsin to these thiol‐liposomes via S‐S bridges yielded a protein/lipid ratio of 3.6 × 10−4 mol enzyme/mol lipid.