Decoration of specific sites on freeze-fractured membranes

Abstract

Fracturing under ultrahigh vacuum (UHV, P ≤ 10-9 Torr) produces membrane fracture faces devoid of contamination. Such clean surfaces are a prerequisite for studies of interactions between condensing gases and distinct regions of a surface. For the study of water condensation, a device has been developed which enables production of pure water vapor and controlled variation of its partial pressure in an UHV freeze-fracture apparatus. Experimerits with yeast plasmalemma fracture faces, produced at -196°C and exposed to pure water vapor before replication, resulted in a "specific decoration" with ice crystals of those pits in the extraplasrnic face where the corresponding particles of the plasmic face had been removed. Because water condenses as discrete ice crystals which resemble intramembrane particles, ice crystals might easily be misinterpreted as actual membrane structures. At low specimen temperature (T ≤ -110°C) the structural features of membrane fracture faces produced under high vacuum (P - 10 4 Torr) should, therefore, be interpreted with caution. © 1978, Rockefeller University Press., All rights reserved.