CoV Protease Substrate-1 TF5, 100tests

This FRET-based peptide substrate from STEMCELL Technologies is designed for the detection of coronavirus protease activity. It can be cleaved by the 3CLpro coronavirus main protease, which regulates the CoV replication complex and is a potential target for therapeutic applications. The 14-amino-acid sequence KTSAVLQSGFRKME carries a Tide Quencher™ 5 (TQ5) quencher at the N-terminus and a Tide Fluor™ 5 (TF5) donor at the C-terminus. In the intact peptide, intramolecular FRET efficiently quenches TF5 fluorescence; cleavage by CoV proteases dissociates the donor from the quencher, restoring fluorescence that is directly correlated to protease activity.

Reported photophysical properties include an excitation wavelength of 649 nm, an emission wavelength of 664 nm, a cutoff of 660 nm, and an extinction coefficient of 250,000 cm⁻¹M⁻¹. The predicted molecular mass is 3620.33 kDa, and purity is ≥ 95%. The product is supplied lyophilized from a dimethylformamide (DMF) solution prepared by vacuum drying.

For storage, the substrate is stable at -20 °C when protected from prolonged exposure to light and remains stable until the expiry date on the label. Before use, the vial should be centrifuged and reconstituted in DMSO without vortexing. Single-use aliquots should be prepared and stored at -20 °C, avoiding repeated freeze-thaw cycles. For assays, the substrate is diluted 1 in 200 in 20 mM Tris buffer (pH 7.5) or another suitable buffer, with 50 µL of substrate solution used per well in a 96-well plate. The product is intended for research use only.