C-Laurdan spectrophotometry reveals higher membrane order for FusMidp-vesicle as compared with the TGN/E. Immunoisolated membranes were stained with C-Laurdan and subsequently analyzed by fluorescence spectrophotometry. The GP is a relative measure for membrane order (see Materials and methods). FusMidp-vesicles (red bar) exhibited a higher GP value than the TGN/E (blue bar; n = 3 independent experiments; mean estimate ± SD).