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a b s t r a c tAt the end of December 2019, a novel coronavirus, 2019-nCoV, caused an outbreak of pneumonia spreading from Wuhan, Hubei province, to the whole country of China, which has posed great threats to public health and attracted enormous attention around the world. To date, there are no clinically approved vaccines or antiviral drugs available for these human coronavirus infections. Intensive research on the novel emerging human infectious coronaviruses is urgently needed to elucidate their route of transmission and pathogenic mechanisms, and to identify potential drug targets, which would promote the development of effective preventive and therapeutic countermeasures. Herein, we describe the epidemic and etiological characteristics of 2019-nCoV, discuss its essential biological features, including tropism and receptor usage, summarize approaches for disease prevention and treatment, and speculate on the transmission route of 2019-nCoV.

Summary Coronavirus (CoV) pandemics have become a huge threat to the public health worldwide in the recent decades. Typically, severe acute respiratory syndrome CoV (SARS‐CoV) caused SARS pandemic in 2003 and SARS‐CoV‐2 caused the ongoing COVID‐19 pandemic. Both viruses are most likely originated from bats. Thus, direct or indirect interspecies transmission from bats to humans is required for the viruses to cause pandemics. Receptor utilization is a key factor determining the host range of viruses which is critical to the interspecies transmission. Angiotensin converting enzyme 2 (ACE2) is the receptor of both SARS‐CoV and SARS‐CoV‐2, but only ACE2s of certain animals can be utilized by the viruses. Here, we employed pseudovirus cell‐entry assay to evaluate the receptor‐utilizing capability of ACE2s of 20 animals by the two viruses and found that SARS‐CoV‐2 utilized less ACE2s than SARS‐CoV, indicating a narrower host range of SARS‐CoV‐2. Especially, SARS‐CoV‐2 tended not to use murine or non‐mammal ACE2s. Meanwhile, pangolin CoV, another SARS‐related coronavirus highly homologous to SARS‐CoV‐2 in its genome, yet showed similar ACE2 utilization profile with SARS‐CoV rather than SARS‐CoV‐2. Nevertheless, the actually susceptibility of these animals to the coronaviruses should be further verified by in‐vivo studies. To clarify the mechanism underlying the receptor utilization, we compared the amino acid sequences of the 20 ACE2s and found 5 amino acid residues potentially critical for ACE2 utilization, including the N‐terminal 20 th and 42 nd amino acid residues that might determine the different receptor utilization of SARS‐CoV, SARS‐CoV‐2 and pangolin CoV. Our studies enhance the understanding of receptor utilization of pandemic coronaviruses, potentially contributing to the virus tracing, intermediate host screening and epidemic prevention for pathogenic coronaviruses.

Two spin-crossover (SCO) supramolecular isomers formulated as [Fe(Mebpt){Au(CN)2}]n·xH2O (1, x = 0, and 2·H2O, x = n, MebptH = 3-(5-methyl-2-pyridyl)-5-(2-pyridyl)-1,2,4-triazole) have been successfully isolated and characterized by single-crystal X-ray crystallography, thermogravimetric analysis, differential scanning calorimetry, variable-temperature powder X-ray diffraction, and magnetic measurements. Structural analysis reveals that 1 is a two-dimensional coordination layer and 2·H2O is a one-dimensional coordination ladder structure, in which the Mebpt(-) ligands are coordinated in trans and cis bridging mode in 1 and 2·H2O, respectively. Dramatically, their SCO properties are further influenced by the octahedral coordination configuration of Fe(II). In 1, only the Fe(II) centers in trans configuration exhibit spin transition (Tc = 303 K), while in 2·H2O and the dehydrated 2, gradual two-step SCO (Tc1 = 235 K, Tc2 = 313 K) and one-step SCO behaviors (Tc = 315 K) occur, respectively.

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