THE DISCRIMINATION OF IGM AND IGG TYPE ANTIBODIES AND FAB' AND F(AB)(2) ANTIBODY FRAGMENTS ON AN INDUSTRIAL SUBSTRATE USING SCANNING FORCE MICROSCOPY

We have previously employed scanning force microscopy (SFM) to study a ntibody-antigen molecular interactions on microtiter wells used for en zyme linked immunosorbant assays (ELISA). Here we demonstrate the abil ity of SFM to image and discriminate different types of antibody and a ntibody fragments bound to an ELISA well surface, The samples studied include a type IgG antibody with a proportion of bound IgM and two-dim ensional films of whole IgG antibody, and Fab' and F(ab)(2) antibody f ragments. Molecular resolution is achieved in each case despite the si ze of substrate features exceeding most of the molecular dimensions ob served. Analysis of the data shows that the SFM overestimates molecula r dimensions by an approximately constant amount, which is proposed to principally result from the effects of a finite probe size and not fr om deformation of the molecular species due to the imaging forces empl oyed.