Reduction by ion-milling of surface corrugation of thin amorphous carbon films for biological specimen substrates in scanning tunneling microscopy

A method is described for reducing the surface corrugation of amorphous carbon films prepared on glass or mica by electron beam evaporation. Normally, a film with a thickness of 10 nm exhibits a peak-to-valley corrugation of about 1.5 nm within an area of 200 nm/sup 2/ in STM measurements. After rotary ion-milling of the film surface in vacuum by an argon beam at low angle of incidence, the corrugation measured by STM is reduced to a value of 0.8 to 1 nm on an area of the same size. Such films were tested as substrates for metal-coated type-I collagen, a filamentous biomolecule only 1.4 nm in diameter. In STM images this molecule was much easier to identify on ion-milled substrates than it was on standard carbon or platinum-carbon film substrates. (11 References)

2D crystallization: from art to science

The techniques as well as the principles of the 2D crystallization of membrane and water-soluble proteins for electron crystallography are reviewed. First, the biophysics of the interactions between proteins, lipids and detergents is surveyed. Second, crystallization of membrane proteins in situ and by reconstitution methods is discussed, and the various factors involved are addressed. Third, we elaborate on the 2D crystallization of water-soluble proteins, both in solution and at interfaces, such as lipid monolayers, mica, carbon film or mercury surfaces. Finally, techniques and instrumentations that are required for 2D crystallization are described