The 3CL Protease (T21I, S144A) (SARS-CoV-2) Assay Kit is a 96-well homogeneous fluorogenic assay designed to measure the activity of T21I, S144A mutated 3CL Protease for screening and profiling applications, with no time-consuming washing steps. 3CL inhibitor GC376 is also included as a control.

Figure 1: Illustration of the principle behind the 3CL protease assay.
The 3CL Protease Substrate is an internally quenched 14-mer fluorogenic peptide (DABCYL-KTSAVLQSGFRKME-EDANS). When the donor (EDANS) and acceptor (DABCYL) fluorophores are in close proximity the energy emitted from EDANS is quenched by DABCYL (intact substrate). Upon proteolysis by 3CL, the peptide substrate is cleaved between the glutamine and serine residues to generate the highly fluorescent peptide fragment (SGFRKME-EDANS). The fluorescence intensity increases proportionally to the activity of 3CL. More information on the substrate, including MW and structure, can be found on our website (BPS Bioscience #79952).