Labeling of immobilized proteins using dipyrrometheneboron difluoride dyes

A kit for detection of poly(amino acids) immobilized on a solid surface, said kit comprising:

• a. a dipyrrometheneboron difluoride dye of the formula:
• wherein each of R1 through R7 are independently selected from the group consisting of H, halogen, -L-Rx, and substituted or unsubstituted C1-C6 alkyl, aryl, arylethenyl, arylbutadienyl, and heteroaryl;
• provided that one or more of R1 through R7 is H,
• two or more of R1 through R7 is nonhydrogen, and
• only one of R1 through R7 is -L-Rx, where L is a spacer having 1-24 nonhydrogen atoms and Rx is a maleimide or a succinimidyl ester of a carboxylic acid;
• such that the dipyrrometheneboron difluoride dye has an absorption maximum between 495 nm and 640 nm;
• b. a specific binding pair member that contains a label and that selectively binds to a target that is its complementary binding pair.