SCANNING-TUNNELING-MICROSCOPY OF MONOCLONAL IMMUNOGLOBULIN-G

A mouse monoclonal IgG(1) was studied by scanning tunneling microscopy . The immunoglobulin solution was deposited onto freshly cleaved mica, dried and rotary shadowed with platinum and carbon. Several images of IgG molecules were obtained. The overall features (approximate size, symmetry) remained apparent under the metal coating film. Imaging unco ated IgG was more difficult. However several images of IgG deposited o n graphite consistent with the known structure were obtained. A defini te improvement in image quality was observed when the tunneling curren t was reduced from 50, to 30 and 4 pA. Short treatment of graphite by glow discharge was tested to improve adsorption of the hydrophilic IgG molecules. The technique may be useful but transforms the atomically flat graphite surface into carbon grains which make difficult the loca lization of the deposited molecules.