Let us assume that we are working with a vesicle created from a biological membrane and wish to determine whether the various proteins are integral or peripheral and exposed to which side of the membrane (for the simplicity, we will further assume that there are no free proteins in the internal space in the vesicle-only proteins which are associated with the membrane are present. The following results have been obtained.

a. SDS electrophoresis of the intact membrane reveals the presence of 5 proteins having molecular weights of 6, 15, 30, 45,and 80 kDa.

b. If the membranes are treated with NaCl and then centrifuged, proteins having molecular weights of 6, and 30 kDa are found in the supernatant while the remaining proteins are found in the pellet.

c. If the membranes are sonicated (a process which opens the vesicle) in the presence of NaCl and then centrifuged, proteins having molecular weights of 6, 15, 30 kDa are found in the supernatant and the reminder in the pellet.

d. Treatment of the intact membranes with (Carbon-14-isotopic labeled trinitrobenzenesulfonate (TNBS) results in incorporation of radioactivity into the proteins having molecular weights of 6, 30, 45, and 80 kDa.

e. Sonication in presence of Carbon-14-isotopic labeled TNBS results in incorporation of radioactivity into proteins having molecular weights of 6, 15, 30, 45, and 80 kDa.

f. If the intact membranes are first treated with nonradioactive TNBS and the resulting product sonicated in the presence of Carbon-14-isotopic labeled TNBS, proteins having molecular weight of 15, and 45 kDa are found to contain radioactivity.