The glycoprotein spike (S) on the surface of SARS-CoV-2 is a determinant for viral invasion and host immune response. Herein, we characterized the site-specific N-glycosylation of S protein at the level of intact glycopeptides. All 22 potential N-glycosites were identified in the S-protein protomer and were found to be preserved among the 753 SARS-CoV-2 genome sequences. The glycosites exhibited glycoform heterogeneity as expected for a human cell-expressed protein subunit. We identified masses that correspond to 157 N-glycans, primarily of the complex type. In contrast, the insect cell-expressed S protein contained 38 N-glycans, completely of the high-mannose type. Our results revealed that the glycan types were highly determined by the differential processing of N-glycans among human and insect cells, regardless of the glycosites’ location. Moreover, the N-glycan compositions were conserved among different sizes of subunits. Our study indicate that the S protein N-glycosylation occurs regularly at each site, albeit the occupied N-glycans were diverse and heterogenous. This N-glycosylation landscape and the differential N-glycan patterns among distinct host cells are expected to shed light on the infection mechanism and present a positive view for the development of vaccines and targeted drugs.

SummaryThe glycoprotein spike (S) on the surface of SARS-CoV-2 is a determinant for viral invasion and host immune response. Herein, we characterized the site-specific N-glycosylation of S protein at the level of intact glycopeptides. All 22 potential N-glycosites were identified in the S-protein protomer and were found to be preserved among the 753 SARS-CoV-2 genome sequences. The glycosites exhibited glycoform heterogeneity as expected for a human cell-expressed protein subunits. We identified masses that correspond to 157 N-glycans, primarily of the complex type. In contrast, the insect cell-expressed S protein contained 38 N-glycans, primarily of the high-mannose type. Our results revealed that the glycan types were highly determined by the differential processing of N-glycans among human and insect cells. This N-glycosylation landscape and the differential N-glycan patterns among distinct host cells are expected to shed light on the infection mechanism and present a positive view for the development of vaccines and targeted drugs.

Metal complexes have been widely investigated as promising electrocatalysts for CO2 reduction. Most of the current research efforts focus mainly on ligands based on pyrrole subunits, and the reported activities are still far from satisfactory. A novel planar and conjugated N4‐macrocyclic cobalt complex (Co(II)CPY) derived from phenanthroline subunits is prepared herein, and it delivers high activity for heterogeneous CO2 electrocatalysis to CO in aqueous media, and outperforms most of the metal complexes reported so far. At a molar loading of 5.93×10−8 mol cm−2, it exhibits a Faradaic efficiency of 96 % and a turnover frequency of 9.59 s−1 towards CO at −0.70 V vs. RHE. The unraveling of electronic structural features suggests that a synergistic effect between the ligand and cobalt in Co(II)CPY plays a critical role in boosting its activity. As a result, the free energy difference for the formation of *COOH is lower than that with cobalt porphyrin, thus leading to enhanced CO production.

A ubiquitous herpesvirus that establishes life-long infection, the Epstein-Barr virus (EBV) has yielded little insight into how a single agent in general accord with its host can produce diverse pathologies ranging from oral hairy leukoplakia to nasopharyngeal carcinoma, from infectious mononucleosis to Hodgkin's disease (HD) and Burkitt's lymphoma. Its pathogenesis is further confounded by the less than total association of virus with histologically similar tumors. In other viral systems, defective (interfering) viral genomes are known to modulate outcome of infection, with either ameliorating or intensifying effects on disease processes initiated by prototype strains. To ascertain whether defective EBV genomes are present in HD, we examined paraffin-embedded tissue from 56 HD cases whose EBV status was first determined by cytohybridization for nonpolyadenylated EBV RNAs (EBERs). Using both standard polymerase chain reaction (PCR) and PCR in situ hybridization, we successfully amplified sequences that span abnormally juxtaposed BamHI W and Z fragments characteristic of defective heterogeneous (het) EBV DNA from 10 of 32 (31%) EBER-positive tumors. Of 24 EBER-negative HD, 8 yielded PCR products indicating presence of het EBV DNA. Two of these contained defective EBV in the apparent absence of the prototype virus. Of the 42 tumors analyzed for defective EBV by both PCR techniques, there was concordance of results in 38 (90%). Detection of defective EBV genomes with the potential to disrupt viral gene regulation suggests one mechanism for pathogenic diversity that may also account for loss of prototypic EBV from individual tumor cells.

The construction of isolated metal sites represents a promising approach for electrocatalyst design toward the efficient electrochemical conversion of carbon dioxide (CO2). Herein, Fe‐doped graphitic carbon nitride is rationally prepared by a simple adsorption method and is used as template to construct isolated FeN4 sites through a confined pyrolysis strategy, which avoids the agglomeration of metal atoms to particles during the synthesis process and thus provides abundant active sites for the CO2 reduction reaction. The isolated FeN4 sites lower the energy barrier for the key intermediate in the CO2 reduction process, leading to the enhanced selectivity for CO production with a faradaic efficiency of up to 93%.