A range of optical reporters is prepared by electrostatic interactions between a cationic conjugated oligoelectrolyte (COE) and dye-labeled single-stranded DNAs (ssDNA). Proteins perturb the optical properties of these aggregates, and generate unique fluorescence resonance energy transfer (FRET) patterns that allow protein discrimination. Two different signatures can be obtained, depending on whether the fluorescence intensity of the COE or the ssDNA-bound dye is observed.