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)

Scanning tunneling microscopy of insulators and biological specimens based on lateral conductivity of ultrathin water films

Scanning tunneling microscopy is based on the flow of an electrical current and thus cannot be used to directly image insulating material. It has been found, however, that a very thin film of water (about one monolayer) adsorbed to a surface exhibits a surprisingly high conductivity that is sufficient to allow scanning tunneling microscope imaging at currents below 1 picoampere. Hydrophilic insulators, such as glass and mica, can thus be imaged in humid air. The same is true for biological specimens deposited on such surfaces, as demonstrated by the scanning tunneling microscope imaging of plasmid DNA on mica. [References: 19

The complete Corynebacterium glutamicum ATCC 13032 genome sequence and its impact on the production of L-aspartate-derived amino acids and vitamins

Kalinowski J, Bathe B, Bartels D, et al. The complete Corynebacterium glutamicum ATCC 13032 genome sequence and its impact on the production of L-aspartate-derived amino acids and vitamins. Journal of Biotechnology. 2003;104(1-3):5-25.The complete genomic sequence of Corynebacterium glutainicum ATCC 13032, well-known in industry for the production of amino acids, e.g. of L-glutamate and L-lysine was determined. The C glutamician genome was found to consist of a single circular chromosome comprising 3 282 708 base pairs. Several DNA regions of unusual composition were identified that were potentially acquired by horizontal gene transfer, e.g. a segment of DNA from C diphtheriae and a prophage-containing region. After automated and manual annotation, 3002 protein-coding genes have been identified, and to 2489 of these, functions were assigned by homologies to known proteins. These analyses confirm the taxonomic position of C glutamicum as related to Mycobacteria and show a broad metabolic diversity as expected for a bacterium living in the soil. As an example for biotechnological application the complete genome sequence was used to reconstruct the metabolic flow of carbon into a number of industrially important products derived from the amino acid L-aspartate. (C) 2003 Elsevier B.V. All rights reserved