DNA encoded peptide library for SARS-CoV-2 3CL protease covalent inhibitor discovery and profiling.

Covalent protease inhibitors serve as valuable tools for modulating protease activity and are essential for investigating the functions of protease targets. These inhibitors typically consist of a recognition motif and a covalently reactive electrophile. Substrate peptides, featuring residues capable of fitting into the substrate pockets of proteases, undergo chemical modification at the carbonyl carbon of the P1 residue with an electrophile and have been widely applied in the development of covalent inhibitors. In this study, we utilized a DNA-encoded peptide library to replicate peptide binder sequences and introduced a vinyl sulfone warhead at the C-termini to construct the DNA-encoded peptide covalent inhibitor library (DEPCIL) for targeting cysteine proteases. Screening results toward 3CL protease demonstrated the efficacy of this library, not only in identifying protease inhibitors, but also in discovering amino acids that can conform to aligned protease pockets. The identified peptide sequences provide valuable insight into the amino acid preferences within substrate binding pockets, and our novel technology is indicative of the potential for similar strategies to discover covalent inhibitors and profile binding preferences of other proteases.

Acetone fractionation: a simple and efficient method to improve the performance of lignin for dye pollutant removal.

In this work, it was found that the adsorption capacity of lignin to cationic dye (methylene blue, MB) from aqueous solution could be significantly improved by simple acetone fractionation. The removal efficiency of MB by acetone insoluble kraft lignin (AIKL) was 10 times that of unfractionated kraft lignin (KL). And the maximum capacity of AIKL could reach up to 623.4 mg g-1. And the high removal rate could be achieved even at low concentrations. The effects of ionic strength, temperature, adsorbent dosage were systematically investigated. Adsorption kinetics showed the adsorption behavior obeyed the pseudo-second-order kinetic model. The equilibrium data was more consistent with the Langmuir isotherm model. Thermodynamic analyses proved that the adsorption was a spontaneous and endothermic physisorption process. In addition, the reasons for the enhanced adsorption effect by fractionation were clarified based on characterization by FT-IR. The enhancement of π-π interaction between AIKL and MB caused by fractionation plays an important role in the adsorption process.