Zhou et al. reported the discovery of RmYN02, a strain closely related to SARS-CoV-2, which is claimed to contain a natural PAA amino acid insertion at the S1/S2 junction of the spike protein at the same position of the PRRA insertion that has created a polybasic furin cleavage site in SARS-CoV-2. The authors support with their findings the theory that the furin cleavage site insertion present in SARS-CoV-2 is natural. Because no nucleotide alignment with closely related strains of the region coding for the supposed insertion is provided by Zhou et al., we have applied several alignment algorithms to search for the most parsimonious alignments. We conclude that RmYN02 does not contain an insertion at the S1/S2 junction when compared to its closest relatives at the nucleotide level, but rather a 6-nucleotide deletion and that the claimed PAA insertion is more likely to be the result of mutations. A close examination of RmYN02 sequencing records and assembly methods is wishful. In conclusion, SARS-CoV-2, with its 12-nucleotide insertion at the S1/S2 junction remains unique among its sarbecovirus relatives. Recently, Zhou et al. [1] reported the discovery of a novel coronavirus strain RmYN02, which the authors claim to contain a natural PAA amino acid insertion at the S1/S2 junction of the spike protein at the same position of the PRRA insertion that has created a polybasic furin cleavage site in severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2).

SummaryThe unprecedented epidemic of pneumonia caused by a novel coronavirus, HCoV-19, in China and beyond has caused public health concern at a global scale. Although bats are regarded as the most likely natural hosts for HCoV-191,2, the origins of the virus remain unclear. Here, we report a novel bat-derived coronavirus, denoted RmYN02, identified from a metagenomics analysis of samples from 227 bats collected from Yunnan Province in China between May and October, 2019. RmYN02 shared 93.3% nucleotide identity with HCoV-19 at the scale of the complete virus genome and 97.2% identity in the 1ab gene in which it was the closest relative of HCoV-19. In contrast, RmYN02 showed low sequence identity (61.3%) to HCoV-19 in the receptor binding domain (RBD) and might not bind to angiotensin-converting enzyme 2 (ACE2). Critically, however, and in a similar manner to HCoV-19, RmYN02 was characterized by the insertion of multiple amino acids at the junction site of the S1 and S2 subunits of the Spike (S) protein. This provides strong evidence that such insertion events can occur in nature. Together, these data suggest that HCoV-19 originated from multiple naturally occurring recombination events among those viruses present in bats and other wildlife species.

No abstract

van der Waals (vdW) heterostructures are receiving great attentions due to their intriguing properties and potentials in many research fields. The flow of charge carriers in vdW heterostructures can be efficiently rectified by the interlayer coupling between neighboring layers, offering a rich collection of functionalities and a mechanism for designing atomically thin devices. Nevertheless, nonuniform contact in larger-area heterostructures reduces the device efficiency. In this work, ion irradiation had been verified as an efficient technique to enhance the contact and interlayer coupling in the newly developed graphene/WSe 2 heterostructure with a large area of 10 mm × 10 mm. During the ion irradiation process, the morphology of monolayer graphene had been modified, promoting the contact with WSe 2 . Experimental evidence of the tunable interlayer electron transfer are displayed by investigation of photoluminescence and ultrafast absorption of the irradiated heterostructure. Besides, we have found that in graphene/WSe 2 heterostructure, graphene serves as a fast channel for the photoexcited carriers to relax in WSe 2 , and the nonlinear absorption of WSe 2 could be effectively tuned by the carrier transfer process in graphene, enabling specific optical absorption of the heterostructure in comparison with separated graphene or WSe 2 . On the basis of these new findings, by applying the ion beam modified graphene/WSe 2 heterostructure as a saturable absorber, Q-switched pulsed lasing with optimized performance has been realized in a Nd:YAG waveguide cavity. This work paves the way toward developing novel devices based on large-area heterostructures by using ion beam irradiation.

Optical nanothermometers have attracted a lot of attentions due to their non-contact and precise measurement with high spatial resolution at the micro- and nanoscale. They can apply for various types...