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BackgroundThe recent outbreak of infections by the 2019 novel coronavirus (2019-nCoV), the third zoonotic CoV has raised great public health concern. The demand for rapid and accurate diagnosis of this novel pathogen brought significant clinical and technological challenges. Currently, metagenomic next-generation sequencing (mNGS) and reverse-transcription PCR (RT-PCR) are the most widely used molecular diagnostics for 2019-nCoV. Methods2019-nCoV infections were confirmed in 52 specimens by mNGS. Genomic information was analyzed and used for the design and development of an isothermal, CRISPR-based diagnostic for the novel virus. The diagnostic performance of CRISPR-nCoV was assessed and also compared across three technology platforms (mNGS, RT-PCR and CRISPR) Results2019-nCoVs sequenced in our study were conserved with the Wuhan strain, and shared certain genetic similarity with SARS-CoV. A high degree of variation in the level of viral RNA was observed in clinical specimens. CRISPR-nCoV demonstrated a near single-copy sensitivity and great clinical sensitivity with a shorter turn-around time than RT-PCR. ConclusionCRISPR-nCoV presents as a promising diagnostic option for the emerging pathogen.
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The objective of this work was studying the effects of combined chlorine on the physicochemical properties and the structure of shellac. Bleached shellacs with different chlorine content were prepared by means of elimination reaction which sodium ethoxide was used as nucleophilic reagent. Then polymerization time and iodine value characterizing the quality of shellac were tested for investigating the relationship between the physicochemical properties and chlorine. The mechanism of dechlorination of shellac was analyzed, and the structures of products were characterized with the aid of ultraviolet spectrophotometer. It was demonstrated that the polymerization time become long and the value of double bond become large with the decrease of chlorine combined in shellac molecule, and that the properties of shellac with low chlorine content had been improved. The structure of shellac obtained by means of dechlorination was different from that of product without dechlorination.
