Fluorescence-based continuous assay for the aspartyl protease of human immunodeficiency virus-1

5-Dimethylaminonaphthalene-1-sulfonyl-Ser-Gln-Asn-Tyr-Pro-Ile-Val-Trp (Dns-SQNYPIVW) is a fluorescent substrate for the aspartyl protease of human immunodeficiency virus-1. In intact substrate, fluorescence of Trp (λ ex 290 nm, λ em 360 nm) was 60% quenched by energy transfer to the dansyl group. Protease-catalyzed cleavage at the Tyr-Pro bond abolished the energy transfer, and the consequent increase in Trp fluorescence was used to follow the enzymatic reaction. At substrate concentrations 100 μM.