The present invention describes the modification ofpolypeptides, more particularly channel proteins with a thiol reactive agent so as to introduce an azide group. The present invention further describes vesicles comprising channel proteins modified according to the invention, which upon reaction with a phosphine open up thereby releasing the content of the vesicles. The reagents, polypeptides and vesicles described in the present invention have in vivo and in vitro applications in both drug delivery and imaging.
