Nirmatrelvir (PF-07321332) is a nitrile-bearing small-molecule inhibitor that, in combination with ritonavir, is used to treat infections by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Nirmatrelvir interrupts the viral life cycle by inhibiting the SARS-CoV-2 main protease (M pro ), which is essential for processing viral polyproteins into functional nonstructural proteins. We report studies which reveal that derivatives of nirmatrelvir and other M pro inhibitors with a nonactivated terminal alkyne group positioned similarly to the electrophilic nitrile of nirmatrelvir can efficiently inhibit isolated M pro and SARS-CoV-2 replication in cells. Mass spectrometric and crystallographic evidence shows that the alkyne derivatives inhibit M pro by apparent irreversible covalent reactions with the active site cysteine (Cys145), while the analogous nitriles react reversibly. The results highlight the potential for irreversible covalent inhibition of M pro and other nucleophilic cysteine proteases by alkynes, which, in contrast to nitriles, can be functionalized at their terminal position to optimize inhibition and selectivity, as well as pharmacodynamic and pharmacokinetic properties.

The two SARS‐CoV‐2 proteases, i. e . the main protease (M pro ) and the papain‐like protease (PL pro ), which hydrolyze the viral polypeptide chain giving functional non‐structural proteins, are essential for viral replication and are medicinal chemistry targets. We report a high‐throughput mass spectrometry (MS)‐based assay which directly monitors PL pro catalysis in vitro . The assay was applied to investigate the effect of reported small‐molecule PL pro inhibitors and selected M pro inhibitors on PL pro catalysis. The results reveal that some, but not all, PL pro inhibitor potencies differ substantially from those obtained using fluorescence‐based assays. Some substrate‐competing M pro inhibitors, notably PF‐07321332 (nirmatrelvir) which is in clinical development, do not inhibit PL pro . Less selective M pro inhibitors, e. g . auranofin, inhibit PL pro , highlighting the potential for dual PL pro /M pro inhibition. MS‐based PL pro assays, which are orthogonal to widely employed fluorescence‐based assays, are of utility in validating inhibitor potencies, especially for inhibitors operating by non‐covalent mechanisms.

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Finding the location of the mobile phone is one of the important features of the 3G mobile communication system. Many valuable locationbased services can be enabled by this new feature. Telecommunication managers and engineers are often puzzled by location terminologies and techniques as well as how to implement them, since location systems are not natural evolution from past generations of telecommunication systems. In this paper, we discuss briefly why locating mobile phone becomes a hot topic and what technologies are being studied. We then describe and clarify the latest standards issues surrounding the positioning methods specified for 3G systems. These include cell-ID-based, assisted GPS, and TDOAbased methods, such as OTDOA, E-OTD, and A-FLT.

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