Estimation of Inactivation time for the SARS-CoV-2 virus from the UV biometer in South Korea.

The coronavirus disease 2019 (COVID-19) is a result of the infection by "severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and has caused various social and economic effects over the globe. As the SARS-CoV-2 is effectively inactivated by the exposure to the UV-B radiation (shorter than 315 nm), the exposure time for inactivation of the SARS-CoV-2 was estimated using the broadband UV observation instrument over 11 observation sites in South Korea. For the limitation of the UV biometer, which has limited spectral information, the coefficient for conversion from the erythemal UV (EUV) to the radiation for virus inactivation was adopted before estimating the inactivation time. The inactivation time of SARS-CoV-2 is significantly dependent on seasonal and diurnal variations due to the temporal variations of surface incident UV irradiance. The inactivation times in summer and winter were around 10 and 50 min, respectively. The inactivation time was unidentified during winter afternoons due to the weak spectral UV solar radiation in winter. As the estimation of inactivation time using broadband observation includes the uncertainty due to the conversion coefficient and the error due to the solar irradiance, the sensitivity analysis of the inactivation time estimation was also conducted by changing the UV irradiance.

ACPT gene is inactivated in mammalian lineages that lack enamel or teeth.

Loss of tooth or enamel is widespread in multiple mammal lineages. Although several studies have been reported, the evolutionary mechanisms of tooth/enamel loss are still unclear. Most previous studies have found that some tooth-related genes have been inactivated in toothless and/or enamel-less mammals, such as ENAM, ODAM, C4orf26, AMBN, AMTN, DSPP, etc. Here, we conducted evolutionary analyses on ACPT playing a key role in amelogenesis, to interrogate the mechanisms. We obtained the ACPT sequences from 116 species, including edentulous and enamel-less mammals. The results shows that variant ORF-disrupting mutations were detected in ACPT coding region among nine edentulous baleen whales and three enamel-less taxa (pygmy sperm whale, aardvark, nine-banded armadillo). Furtherly, selective pressure uncovered that the selective constraints have been relaxed among all toothless and enamel-less lineages. Moreover, our results support the hypothesis that mineralized teeth were lost or degenerated in the common ancestor of crown Mysticeti through two shared single-base sites deletion in exon 4 and 5 of ACPT among all living baleen whales. D N/d S values on transitional branches were used to estimate ACPT inactivation records. In the case of aardvark, inactivation of ACPT was estimated at ~23.60-28.32 Ma, which is earlier than oldest aardvark fossil record (Orycteropus minutus, ~19 Ma), suggesting that ACPT inactivation may result in degeneration or loss of enamel. Conversely, the inactivation time of ACPT estimated in armadillo (~10.18-11.30 Ma) is later than oldest fossil record, suggesting that inactivation of ACPT may result from degeneration or loss of enamel in these mammals. Our findings suggested that different mechanisms of degeneration of tooth/enamel might exist among toothless and enamel-less lineages during evolution. Our study further considered that ACPT is a novel gene for studying tooth evolution.

Physicochemical characterization of the staphylolytic LysK enzyme in complexes with polycationic polymers as a potent antimicrobial.

Staphylococcus aureus causes many serious visceral, skin, and respiratory diseases. About 90% of its clinical strains are multi-drug resistant, but the use of bacteriophage lytic enzymes offers a viable alternative to antibiotic therapy. LysK, the phage K endolysin, can lyse S. aureus when purified and exposed externally. It has been investigated in its complexes with polycationic polymers (poly-l-lysines (PLLs) of molecular weights 2.5, 9.6, and 55.2 kDa and their block copolymers with polyethylene glycol PLL10-PEG114, PLL30-PEG114, and PLL30-PEG23) as a basis for creating active and stable antimicrobial. Complexing with polycationic PLLs produces a stabilizing effect on LysK due to structure ordering in its molecules and break-down of aggregates as a result of electrostatic interaction. The stability of LysK in the presence of PLL-PEG block copolymers improves by both electrostatic and hydrophobic mechanisms. Complexes of LysK with 2.5, 9.6, 55.2 kDa poly-l-lysines and PLL30-PEG114 have demonstrated sufficient stability at the temperatures of physiological activity (37 °C) and storage (4 °C and 22 °C).