Patent ID: 7157575

Claim:
A compound of the formula (I): wherein: one of X and Y is a fluorescent donor moiety or a membrane-permeant derivative thereof, and the other is a quencher moiety, an acceptor fluorophore moiety or a membrane-permeant derivative thereof; R′ is H; R″ is selected from the group consisting of H, physiologically acceptable metal, ammonium cations, —CHR 2 OCO(CH 2 ) n CH 3 , —CHR 2 OCOC(CH 3 ) 3 , acylthiomethyl, acyloxy-alpha-benz, delta-butyrolactonyl, methoxycarbonyloxymethyl, phenyl, methylsulphinylmethyl, betamorpholinoethyl, dialkylaminoethyl, and dialkylaminocarbonyloxymethyl, in which R 2 is selected from the group consisting of H and lower alkyl; A is selected from the group consisting of S, SO, and SO 2 , Z′ is —(CH 2 ) n —NR 2 CO—(CH 2 ) m —; and Z″ is —S(CH 2 ) n —; n is an integer from 0 to 5; m is an integer from 0 to 4.