The main protease (M pro ) of severe acute respiratory syndrome coronavirus (SARS-CoV) plays an essential role in the extensive proteolytic processing of the viral polyproteins (pp1a and pp1ab), and it is an important target for anti-SARS drug development. It was found that SARS-CoV M pro exists in solution as an equilibrium of both monomeric and dimeric forms, and the dimeric form is the enzymatically active form. However, the mechanism of SARS-CoV M pro dimerization, especially the roles of its N-terminal seven residues (N-finger) and its unique C-terminal domain in the dimerization, remain unclear. Here we report that the SARS-CoV M pro C-terminal domain alone (residues 187 to 306; M pro -C) is produced in Escherichia coli in both monomeric and dimeric forms, and no exchange could be observed between them at room temperature. The M pro -C dimer has a novel dimerization interface. Meanwhile, the N-finger deletion mutant of SARS-CoV M pro also exists as both a stable monomer and a stable dimer, and the dimer is formed through the same C-terminal-domain interaction as that in the M pro -C dimer. However, no C-terminal domain-mediated dimerization form can be detected for wild-type SARS-CoV M pro . Our study results help to clarify previously published controversial claims about the role of the N-finger in SARSCoV M pro dimerization. Apparently, without the N-finger, SARS-CoV M pro can no longer retain the active dimer structure; instead, it can form a new type of dimer which is inactive. Therefore, the N-finger of SARS-CoV M pro is not only critical for its dimerization but also essential for the enzyme to form the enzymatically active dimer.

Today, polyurethanes are effectively not recycled and are made principally from nonrenewable, fossil-fuel-derived resources. This study provides the first high-resolution material flow analysis of polyurethane flows through the U.S. economy, tracking back to fossil fuels and covering polyurethane-relevant raw materials, trade, production, manufacturing, uses, historical stocks, and waste management. According to our analysis, in 2016, 2900 thousand tonnes (kt) of polyurethane were produced in the United States and 920 kt were imported for consumption, 2000 kt entered the postconsumer waste streams, and 390 kt were recycled and returned to the market in the form of carpet underlayment. The domestic production of polyurethane consumed 1100 kt of crude oil and 1100 kt of natural gas. With the developed polyurethane flow map, we point out the limitation of the existing mechanical recycling methods and identify that glycolysis, a chemical recycling method, can be used to recycle the main components of postconsumer polyurethane waste. We also explore how targeting biobased pathways could influence the supply chain and downstream markets of polyurethane and reduce the consumption of fossil fuels and the exposure to toxic precursors in polyurethane production.

bCefquinome is a cephalosporin with broad-spectrum antibacterial activity, including activity against Staphylococcus aureus. The objective of our study was to examine the in vivo activity of cefquinome against S. aureus strains by using a neutropenic mouse thigh infection model. Cefquinome kinetics and protein binding in infected neutropenic mice were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In vivo postantibiotic effects (PAEs) were determined after a dose of 100 mg/kg of body weight in mice infected with S. aureus strain ATCC 29213. The animals were treated by subcutaneous injection of cefquinome at doses of 2.5 to 320 mg/kg of body weight per day divided into 1, 2, 3, 6, or 12 doses over 24 h. Cefquinome exhibited time-dependent killing and produced in vivo PAEs at 2.9 h. The percentage of time that serum concentrations were above the MIC (%T >MIC ) was the pharmacokinetic-pharmacodynamic (PK-PD) index that best described the efficacy of cefquinome. Subsequently, we employed a similar dosing strategy by using increasing total cefquinome doses that increased 4-fold and were administered every 4 h to treat animals infected with six additional S. aureus isolates. A sigmoid maximum effect (E max ) model was used to estimate the magnitudes of the ratios of the %T that the free-drug serum concentration exceeded the MIC (%T >fMIC ) associated with net bacterial stasis, a 0.5-log 10 CFU reduction from baseline, and a 1-log 10 CFU reduction from baseline; the respective values were 30.28 to 36.84%, 34.38 to 46.70%, and 43.50 to 54.01%. The clear PAEs and potent bactericidal activity make cefquinome an attractive option for the treatment of infections caused by S. aureus. Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is an important human pathogen that is also an emerging concern in veterinary medicine and animal agriculture. All known mammalian species, including common laboratory rodent and rabbit species, are susceptible to colonization with S. aureus. MRSA has been shown to have a prevalence of 39% and 24.9% in pigs in the Netherlands (1) and Canada (2), respectively, and 28% in veal calves in the Netherlands (3). A Canadian study identified MRSA in 6.3% of ground pork and 5.6% of ground beef but in 32% and 45% of positive pork and beef samples, respectively (4). Some samples of commercially sold meat products in Japan were also found to harbor MRSA strains (5). Because of its ability to colonize a wide range of species, S. aureus can be readily transmitted from one species to another, including from humans to animals and vice versa. Moreover, a majority of S. aureus isolates are resistant to various antimicrobial agents (6), and thus, there are limited antimicrobial options for treatment; accordingly, there is a growing need for more potent antimicrobials to attack these resistant pathogens. Cefquinome (formerly HR 111V) is a fourth-generation cephalosporin developed solely for veterinary use. It displays antimicrobial activities in vitro and in vivo agains...

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SARS coronavirus main protease (M pro ) plays an essential role in the extensive proteolytic processing of the viral polyproteins (pp1a and pp1ab), and it is an important target for anti-SARS drug development. We have reported that both the M pro C-terminal domain alone (M pro -C) and the N-finger deletion mutant of M pro (M pro -D7) exist as a stable dimer and a stable monomer (Zhong et al., J Virol 2008; 82:4227-4234). Here, we report structures of both M pro -C monomer and dimer. The structure of the M pro -C monomer is almost identical to that of the C-terminal domain in the crystal structure of M pro . Interestingly, the M pro -C dimer structure is characterized by 3D domain-swapping, in which the first helices of the two protomers are interchanged and each is enwrapped by four other helices from the other protomer. Each folding subunit of the M pro -C domain-swapped dimer still has the same general fold as that of the M pro -C monomer. This special dimerization elucidates the structural basis for the observation that there is no exchange between monomeric and dimeric forms of M pro -C and M pro -D7.