Binding of E. coli expressing P pili and type 1 pili in SPR assay.
Each type of bacteria (P pili-black line and type 1 pili-gray line) was injected into the flow chambers five times and washed with buffer at pH 7.0 between each injection. P-piliated bacteria were thereafter exposed to three injections of low pH buffer (3.5). The sensogram shows the difference in response between the galabiose-coated and the BSA-coated cells. Large arrows indicate start of injection and short arrows indicate end of injections. The alternating levels during injections of buffer with pH 3.5 originate from different index of refractions for the two buffer solutions (pH 3.5 and 7, respectively).