CruzQuench™ 5 azide is designed to be a superior quencher to Cy5, TF5 and Cy5.5. TQ5 has (a). much stronger absorption; (b). much higher quenching efficiency; and (c). versatile reactive forms with desired solubility for labeling oligonucleotides and peptides. This TQ5 product is reactive to alkynes, and useful for click chemistry.