Quantifying Efficiency of Remote Excitation for Surface-Enhanced Raman Spectroscopy in Molecular Junctions.

Surface-enhanced Raman spectroscopy (SERS) is enabled by local surface plasmon resonances (LSPRs) in metallic nanogaps. When SERS is excited by direct illumination of the nanogap, the background heating of the lattice and electrons can prevent further manipulation of the molecules. To overcome this issue, we report SERS in electromigrated gold molecular junctions excited remotely: surface plasmon polaritons (SPPs) are excited at nearby gratings, propagate to the junction, and couple to the local nanogap plasmon modes. Like direct excitation, remote excitation of the nanogap can generate both SERS emission and an open-circuit photovoltage (OCPV). We compare the SERS intensity and the OCPV in both direct and remote illumination configurations. SERS spectra obtained by remote excitation are much more stable than those obtained through direct excitation when the photon count rates are comparable. By statistical analysis of 33 devices, the coupling efficiency of remote excitation is calculated to be around 10%, consistent with the simulated energy flow.

Porcine deltacoronavirus resists antibody neutralization through cell-to-cell transmission.

ABSTRACTPorcine deltacoronavirus (PDCoV) is an emerging enteric coronavirus that has been reported to infect a variety of animals and even humans. Cell-cell fusion has been identified as an alternative pathway for the cell-to-cell transmission of certain viruses, but the ability of PDCoV to exploit this transmission model, and the relevant mechanisms, have not been fully elucidated. Herein, we provide evidence that cell-to-cell transmission is the main mechanism supporting PDCoV spread in cell culture and that this efficient spread model is mediated by spike glycoprotein-driven cell-cell fusion. We found that PDCoV efficiently spread to non-susceptible cells via cell-to-cell transmission, and demonstrated that functional receptor porcine aminopeptidase N and cathepsins in endosomes are involved in the cell-to-cell transmission of PDCoV. Most importantly, compared with non-cell-to-cell infection, the cell-to-cell transmission of PDCoV was resistant to neutralizing antibodies and immune sera that potently neutralized free viruses. Taken together, our study revealed key characteristics of the cell-to-cell transmission of PDCoV and provided new insights into the mechanism of PDCoV infection.

Porcine deltacoronavirus uses heparan sulfate as an attachment receptor.

Porcine deltacoronavirus (PDCoV) is a newly emerging swine enteropathogenic coronavirus with extensive tissue tropism and cross-species transmission potential. Heparan sulfate (HS) is a complex polysaccharide ubiquitously expressed on cell surfaces and the extracellular matrix and acts as an attachment factor for many viruses. However, whether PDCoV uses HS as an attachment receptor is unclear. In this study, we found that treatment with heparin sodium or heparinase Ⅱ significantly inhibited PDCoV binding and infection among LLC-PK1 and IPI-2I cells. Attenuation of HS sulfuration by sodium chlorate also impeded PDCoV binding and infection. Moreover, we demonstrated that HS functioned independently of amino peptidase N (APN), a functional PDCoV receptor, in PDCoV infection. Molecular docking revealed that the S1 subunit of the PDCoV spike protein might be a putative region for HS binding. Taken together, these results firstly confirmed that HS is an attachment receptor for PDCoV infection, providing new insight into better understanding the mechanisms of PDCoV-host interactions.