Imaging of biological macromolecules on mica in humid air by scanning electrochemical microscopy

Imaging of DNA, keyhole limper hemocyanin, mouse monoclonal IgG. and glucos e oxidase on a mica substrate has been accomplished by scanning electrochem ical microscopy with a tungsten tip. The technique requires the use of a hi gh relative humidity to form a thin film of water on the mica surface that allows electrochemical reactions to take place at the tip and produce a far adaic current (approximate to 1 pA) that can be used to control tip positio n. The effect of relative humidity and surface pretreatment with buffer sol utions on the ionic conductivity of a mica surface was investigated to find appropriate conditions for imaging. Resolution of the order of 1 nm was ob tained.