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While the capsid of viruses in the Alphachrysovirus genus is built of subunits of a single coat protein, the capsid of viruses grouped in the Betachrysovirus genus may consist of subunits of two different proteins. For four of these betachrysoviruses, the detected molecular weights of the putative coat proteins differ from the sizes deduced from the nucleic acid sequence. The origin of these modifications remained unclear and it was hypothesized that the coat proteins undergo unspecific degradation. In our study, we show that these modifications are based on processing steps performed by unknown factors present in extracts of several eukaryotic organisms. Furthermore, we show that the C-terminal domain of P3 is fully degraded after capsid processing and particle assembly. • Coat proteins from FgV-ch9 are processed by eukaryotic factors. • The C-terminus of P3 of FgV-ch9 is fully degraded during processing. • Eukaryotic factors are processing P3 of the related betachrysovirus FodV1. [ABSTRACT FROM AUTHOR]

The non-linear relationship between particle sulfate and SO 2 is still unclear. Continuous observations were conducted in a typical city in Northern China from 2017 to 2020. SO 2 concentration continually decreased, however, the SO 4 2− concentration and the sulfur oxidation ratio increased in 2018–2019. The major reason might be the variations of sulfate formation by the aqueous-phase reactions, especially for the O 2 + TMI oxidation (oxygen catalyzed by transition-metal ions). Particle pH, SO 2 , and Mn concentration were the main factors affecting the O 2 + TMI reaction rate. Sensitivity analysis indicated that the decrease of the O 2 + TMI reaction rate caused by SO 2 or Mn concentration dropping by half can only offset the increased rate caused by a 0.1 unit decrease in particle pH. Considering the actual atmospheric environment in Northern China, if the particle pH continues to drop, the slow decline of SO 2 and Mn concentration may not prevent the increase in the O 2 + TMI oxidation rate. In addition to meteorological parameters, the concentrations of SO 4 2−, crustal elements, and total ammonium were the primary factors for the decrease in particle pH in the past 3 years. Therefore, the impact of pH on sulfate formation must be considered when controlling dust and ammonia emissions. [Display omitted] • Changes in O 2 + TMI reaction rates partly explained the non-linear relationship between SO 4 2− and SO 2 ; • If the pH continues to drop, the slow decline of SO 2 and Mn may not offset the increase in the O 2 + TMI oxidation rate. • The concentrations of SO 4 2−, crustal elements and total ammonium were the primary factors for the decrease in particle pH. [ABSTRACT FROM AUTHOR]