IMMOBILIZING BIOMOLECULES FOR SCANNING FORCE MICROSCOPY BY EMBEDDING IN CARBON

To investigate biomolecules with a scanning force microscope, the biomolecules must be immobilized on a flat, smooth substrate. Therefore the biomolecules were deposited on freshly cleaved mica and overcoated with a thick layer of carbon. The carbon layer, including the embedded biomolecules, was peeled off the mica and its underside was imaged with a scanning force microscope. The method was tested with DNA. It could be shown that (1) DNA stayed in the carbon during the peel-off process; (2) DNA was easy to identify in the flat substrate; (3) the bare DNA could be imaged at high forces without destroying it; and (4) scanning the biomolecules in liquids was possible. An advantage of the technique is that it allows freeze-drying, thus avoiding structural changes caused by air-drying. The replica/anchoring technique was also used to prepare flat, conducting substrates, which might be suitable for scanning tunneling microscopy. © 1993 Academic Press. All rights reserved.