A biosensor 18 in which {HEAD ~ the first second receptor moieties} are {TAIL ~ Fab fragments} which recognize different antigenic determinants 
are
A biosensor 18 in which { HEAD ~ the first second receptor moieties } are { TAIL ~ Fab fragments } which recognize different antigenic determinants
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH