TF4 is designed to be a superior fluorophore alternative to ROX and Texas Red®. TF4 has (a). stronger fluorescence intensity; (b). higher conjugation yield; and (c). longer shelf life. Additionally their fluorescence is pH-independent from pH 3 to 11. These characteristics make this new dye family a superior alternative to ROX and Texas Red®. In pairing with our Tide Quencher™ 4 (TQ4), a variety of FRET peptides and nucleotides can be developed for detecting proteases and molecular beacons with enhanced sensitivity and stability.