ELECTRON-MICROSCOPY STUDIES OF AMPHIPHILIC SELF-ASSEMBLIES ON VITREOUS ICE

The structure of self-assemblies of amphiphiles formed at the air-aque ous solution interface can be determined by cryotransmission electron microscopy (Cryo-TEM). The method is based on fast vitrification of th e thin layer of aqueous solution covered with amphiphilic monolayer by plunging the specimen into liquid ethane at its freezing point. Durin g the process of fast cooling the aggregates maintain their two-dimens ional crystalline integrity and structure, as demonstrated by comparat ive studies involving grazing incidence X-ray diffraction (GID) at the air-solution interface, and the Cryo-TEM measurements of the same amp hiphilic systems on vitreous ice. Bright-field and dark-field images f rom the Cryo-TEM observations provide more detailed information than f rom epifluorescence and Brewster angle microscopy. Furthermore, the el ectron diffraction patterns have the additional advantage that they al low structural characterization of the crystallites almost at a molecu lar level, and furnish data on micro twinning and defects occurring be tween crystalline domains. Cryo-TEM has been applied to elucidate the structure of 2-D and 3-D self-aggregates of amphiphilic alcohols, acid s and their cadmium salts, bola-amphiphiles and mixed monolayers. Epit axial crystallization of hexagonal ice underneath the monolayer of lon g chain alcohol was also directly demonstrated by this method.