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Figure 4. Electron micrograph of membrane
vesicles. Vesicles prepared by osmotic lysis are virtually devoid of soluble
cytoplasmic proteins. Thus, all of the enzymatic activity associated with
the vesicles is a property of the cytoplasmic membrane. Vesicles prepared by
osmotic lysis are approximately 1µ in diameter, and if they are handled
gently, each bacterial cell gives rise to one vesicle (i.e., they are
analogous to red cell ghosts). However, mechanical stress during preparation
may lead to pinching off of smaller sealed vesicles. Once frozen in liquid
nitrogen, vesicles are stable for an indefinite period of time.
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