HIGH-RESOLUTION ELECTRON-MICROSCOPY OF BIOLOGICAL SPECIMENS IN CUBIC ICE

Images of two biological test specimens, catalase and TMV, were recorded in cubic ice, prepared by controlled devitrification at -130 degrees C and -75 degrees C or in vitrified buffer. Cubic ice provides a rigid support for biological specimens which is stable under the electron beam to within about 1 Angstrom A as shown by images of the ice lattice. Neither catalase nor TMV were disrupted by the crystallization of vitrified water. Electron diffraction patterns of highly oriented rafts of TMV extending to 2.3 Angstrom A resolution were used to judge the quality of TMV images. Structural features at 5.75 Angstrom A (TMV) and 5.4 Angstrom A (catalase) were observed directly by optical diffraction. The reproduction of high-resolution details of TMV was better in cubic ice, and the success rate for recording good images was higher than in vitrified medium.