Detection of an increase in fluorescent signal indicates {TAIL ~ the presence} of the enzyme in {HEAD ~ the sample} 
Detection of an increase in fluorescent signal indicates { TAIL ~ the presence } of the enzyme in { HEAD ~ the sample }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD