CruzQuench™ 6 maleimide is designed to be a superior quencher to Cy5.5, TF6 and Alexa Fluor 680. TQ6 has (a). much stronger absorption; (b). much higher quenching efficiency; and (c). versatile reactive forms with desired solubility for labeling oligonucleotides and peptides. This TQ2 product is used for post-labeling of thiol-modified oligonucleotides and cysteine-containing peptides.