Patent ID: 7662644

Claim:
A method for detecting binding of an antibody to an antigen which comprises reacting an antibody with an antigen and detecting an antibody-antigen complex, wherein the antibody is conjugated to a fluorescent compound of the formula: wherein: each m is separately an integer ranging from 1-3; n is an integer ranging from 0 to 5; R 8 , R 11 and R 12 are separately CO, SO 2 , C═C(CN) 2 , S, O or C(CH 3 ) 2 ; each R 13 is alkyl, branched alkyl or heterocyclic ring derivatized with charged groups to enhance water solubility and enhance photostability; each R 9 and R 10 is separately an alkyl chain derivatized with charged groups to enhance water solubility or with reactive groups for conjugation to other molecules.