ABSTRACT
The pandemic of coronavirus disease 2019 (COVID-19) is changing the world like never before. This crisis is unlikely contained in the absence of effective therapeutics or vaccine. The papain-like protease (PLpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays essential roles in virus replication and immune evasion, presenting a charming drug target. Given the PLpro proteases of SARS-CoV-2 and SARS-CoV share significant homology, inhibitor developed for SARS-CoV PLpro is a promising starting point of therapeutic development. In this study, we sought to provide structural frameworks for PLpro inhibitor design. We determined the unliganded structure of SARS-CoV-2 PLpro mutant C111S, which shares many structural features of SARS-CoV PLpro. This crystal form has unique packing, high solvent content and reasonable resolution 2.5 Å, hence provides a good possibility for fragment-based screening using crystallographic approach. We characterized the protease activity of PLpro in cleaving synthetic peptide harboring nsp2/nsp3 juncture. We demonstrate that a potent SARS-CoV PLpro inhibitor GRL0617 is highly effective in inhibiting protease activity of SARS-CoV-2 with the IC
ABSTRACT
OBJECTIVE:To establish a method for determination of trace platinum in zolpidem tartrate. METHODS:Graphite furnace atomic absorption spectrometry(GFAAS)was adopted for direct determination after dissolving sample in 1% Hydrochloric acid solution. Horizontal platform graphite tube was performed with detection wavelength of 244.79 nm,slit width of 0.2 nm and current intensity of hollow cathode lamp of 6 mA. The mode of background correction was zeeman effect,the peak height was used as measurement pattern,and the injection volume was 20 μl. RESULTS:The linear range of platinum was 0-100 ng/ml(r=0.999 0);RSDs of precision and reproducibility tests were no more than 2.0%;recovery was 97.78%-103.07%(RSD=1.6%,n=9);the detection limit was 1.48 ng/ml. CONCLUSIONS:This method is simple and rapid with good precision and accuracy,and can be applied for the determination of trace platinum in zolpidem tartrate.