Patent ID: 8101655

Claim:
A fluorescent dye comprising a xanthene-derived fluorophore having the formula (I) wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are independently selected from H, alkyl, alkoxy, alcohol, ether, alkenyl, alkenoxy, aryl, alkaryl, aralkyl and amido, except that R 1 , R 4 and/or R 5 is not H when bonded to Y, Y 1 and/or Y 2 respectively; X is either O − or S − ; and, at least one of Y, Y 1 , Y 2 , Y 3 , Y 4 and Y 5 is a group for covalently bonding the dye, optionally through the use of a coupling agent, to a target molecule, and is otherwise H.