The substrate compound 3 in which {TAIL ~ the one or more non proteinaceous fluorescent moiety} comprises a dye selected from {HEAD ~ a xanthene dye}, a rhodamine dye, a fluorescein dye, a cyanine dye, a phthalocyanine dye, a squaraine dye and a bodipy dye 
The substrate compound 3 in which { TAIL ~ the one or more non proteinaceous fluorescent moiety } comprises a dye selected from { HEAD ~ a xanthene dye } , a rhodamine dye , a fluorescein dye , a cyanine dye , a phthalocyanine dye , a squaraine dye and a bodipy dye
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH