Analysis of peptide and F4 mutant bindings to the proximal jejunal cells. We incubated the bowel segments of the jejunum in peptides and rF4 strains (SE5000 carrying PBR322-faeG of F4ab, F4ac and F4ad). A, B Confocal microscopy images. We measured the binding activities of peptides with amino acid mutations (green, FITC labelled) and F4 FaeG mutants in the proximal jejunum of piglets using confocal microscopy. We tested the F4 strains in these cells by using monoclonal antibody against F4 and anti-mouse Dylight 594 secondary antibody (1:200 dilution, red). Segments with non-binding peptide (NP control) or SE5000 strain as the control.