CruzFluor sm™ 1 CPG 500 Å is designed to have a much stronger absorption and fluorescence intensity, a much less environment sensitive and pH independent fluorescence from pH 3-11 when compared to EDANS. When peptides and nucleotides are labeled with CruzFluor sm™ 1 they exhibit a much stronger fluorescence and higher sensitivity when compared to those labeled with EDANS. These improved properties of CruzFluor sm™ 1 makes it an excellent substitute to EDANS. A diverse mixture of FRET peptides and nucleotides can be developed for detecting proteases and molecular beacons with increased stability and sensitivity when combined with CruzQuench™ 1. The CruzFluor™ family of products are a fluorescent labeling dye series that spans the full visible spectrum, and are useful to conjugate to nucleic acids, proteins and antibodies. The CruzFluor™ dyes are strong reagents for amine modification because they are incorporated with succinimidyl esters, which have a very strong ability to develop amide bonds that are as stable if not identical to the bonds found on a natural peptide.