3 peptide or the y 1 nanp antibody immobilized on microtiter plates fig5 shows results of cross inhibition of 125 i labelled antibody sp3 b4 binding to synthetic peptide nanp 3 panel a or engineered antibody y1nanp panel b by y1nanp ig or peptide nanp 3 a fixed amount of 125 i labelled antibody sp3 b4 probe was mixed vol vol with decreasing amounts of the various inhibitors diluted in phosphate buffered saline ph 7 3 containing 1 bovine serum albumin and 1 tween 20 the mixture was incubated at 4 u00b0 c overnight by rocking fifty u03bcl of each mixture were incubated on individual polyvinyl microtiter wells coated with either synthetic peptide nanp 3 panel a or purified engineered y1nanp ig panel b the conditions of coating are as detailed in the legend to fig4 the following inhibitors were used purified y1nanp ig wt ig and synthetic peptides nanp 3 cdr3 and vitronectin the percentage of inhibition was calculated as follows average binding of the probe alone average binding of the probe incubated in the presence of inhibitor average binding of the probe alone u00d7 100 tests were done in duplicate fig5 shows that both the peptide and the engineered antibody efficiently inhibited the binding to both physical forms of the nanp 3 epitope i e synthetic peptide and antibody borne however whereas the y1nanp antibody was about four times more effective than the peptide itself panel a in inhibiting.