CoV Protease Substrate-1 TF5, 1000tests

This FRET-based peptide substrate from STEMCELL Technologies is designed for the detection of protease activity from coronaviruses. It targets the coronavirus main protease, also known as 3CLpro, which regulates the CoV replication complex. The substrate consists of a 14-amino-acid sequence (KTSAVLQSGFRKME) flanked by Tide Quencher™ 5 (TQ5) at the N-terminus and Tide Fluor™ 5 (TF5) at the C-terminus. While the peptide is intact, favourable energetic overlap of the TF5 excited state and the TQ5 absorption leads to efficient intramolecular fluorescence quenching of TF5 by TQ5. Upon cleavage by CoV proteases, the TF5 fragment dissociates from TQ5 and its fluorescence is restored, providing a signal that is directly correlated to CoV protease activity.

The product is supplied lyophilized from a dimethylformamide (DMF) solution using vacuum drying, with a stated purity of ≥ 95%. Its spectral 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 lyophilized product is stable at -20°C and should be protected from prolonged exposure to light, remaining stable until the expiry date printed on the label.

Before opening, the vial should be centrifuged and the contents reconstituted in DMSO without vortexing. For a working solution, dilute the substrate 1 in 200 in 20 mM Tris buffer (pH 7.5) or a buffer of choice, and use 50 μL per assay in a 96-well plate. Single-use aliquots should be prepared and stored at -20°C, avoiding repeated freeze-thaw cycles. The product is for research use only and is not intended for human or animal diagnostic or therapeutic uses.