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Liquid-liquid phase separation (LLPS) mediated formation of membraneless organelles has been proposed to coordinate biological processes in space and time. Previously, the formation of phase-separated droplets was described as a unique property of HP1��. Here, we demonstrate that the positive net charge of the intrinsically disordered hinge region (IDR-H) of HP1 proteins is critical for phase separation and that the exchange of four acidic amino acids is sufficient to confer LLPS properties to HP1��. Surprisingly, the addition of mono-nucleosomes promoted H3K9me3-dependent LLPS of HP1�� which could be specifically disrupted with methylated but not acetylated H3K9 peptides. HP1�� mutants defective in H3K9me3 binding were less efficient in phase separationin vitro and failed to accumulate at heterochromatin in vivo. We propose that multivalent interactions of HP1�� with H3K9me3-modified nucleosomes via its chromodomain and dimerization via its chromoshadow domain enable phase separation and contribute to the formation of heterochromatin compartments in vivo.

Water soluble organic compounds (WSOC) account for a large proportion of aerosols and play a critical role in various atmospheric chemical processes. In order to investigate the primary sources and secondary production of WSOC in downtown Beijing, the day and night PM2.5 samples in January (winter), April (spring), July (summer) and October (autumn) of 2017 were collected and analyzed for WSOC and organic tracers in this study. WSOC showed the highest concentration in winter and comparable levels in the other seasons, and dominated by its hydrophobic fraction (HULIS-C). Some typical organic tracers were chosen to evaluate the emission strength and secondary formation for the major sources of WSOC. According to the diurnal patterns and correlation coefficients with the key influencing factors, most SOA tracers were closely related to gaseous photooxidation in summer, but mainly generated via aqueous-phase processing in other seasons. These organic tracers were applied into the positive matrix factorization (PMF) model to calculate the source contributions of WSOC as well as its hydrophobic and hydrophilic portions. The secondary sources contributed over 50 % to WSOC, with higher contributions in summer (75.7 %) and winter (67.7 %), and the largest contributor was aromatic SOC. Besides, the source apportionment results under different pollution levels suggested that controlling biomass burning and the aromatic precursors would be effective to reduce WSOC during the haze episodes in cold seasons. The possible formation mechanisms of the total secondary organic carbon (SOC) as well as hydrophobic and hydrophilic SOC were also explored in this study. The aqueous-phase process appeared to dominate in the SOC formation in winter and spring, while gas-phase photooxidation played a dominant role in summer. Besides, the gaseous photooxidation played a major role in the generation of hydrophobic SOC, whereas aqueous-phase reactions posed vital effects on the formation of hydrophilic SOC.

Silver-based high-conductivity coatings are used in many advanced manufacturing equipment and components, and existing coatings require high-temperature curing. This paper studies the effects of different curing agents on the electrical properties of low-temperature curing (&lt, 100 °C) conductive coatings, and analyzes the effects of different curing temperatures and curing time on the surface resistance, square resistance and resistivity of conductive coatings. The response surface method in Design Expert was used to construct the model, and the curing thermodynamics of different curing agents were analyzed by DSC. It was found that curing agents with lower Tm and activation energy, higher pre-exponential factor and more flexible segments are beneficial to the preparation of highly conductive coatings.

Water soluble organic carbon (WSOC) in atmospheric aerosols may pose significant impacts on haze formation, climate change, and human health. This study investigated the distribution characteristics and sources of WSOC in Beijing based on the diurnal PM1, PM2.5 and PM10 samples collected during haze episodes in winter and early spring of 2017. The haze episode in winter showed elevated level of WSOC, around three times of that in spring. WSOC was enriched in PM2.5 in winter while the proportions in both finer (0–1 μm) and coarse particles (2.5–10 μm) increased in spring. Several organic tracers were carefully selected and measured to demonstrate the sources and formation mechanism of WSOC. Most of the identified organic tracers showed similar seasonal variation, diurnal change and size distributions with WSOC, while the biogenic secondary organic aerosol (SOA) tracer cis-pinonic acid was an obvious exception. Based on the distribution characteristics of the secondary organic tracers and their correlation patterns with key influencing factors, the importance of the gas-phase versus aqueous-phase oxidation processes on SOA formation was explored. The gas-phase photochemical oxidation was weakened during haze episodes, whereas the aqueous-phase oxidation became the major pathway of SOA formation, especially in winter, at night and for the coarser particles. Secondary sources accounted for more than 50 % of WSOC in both winter and spring. Biomass burning was not the dominant source of WSOC in Beijing during haze episodes. Primary sources showed greater influence on finer particles while secondary sources became more important for coarser particles during haze episode in winter. SOC estimated by the OC-EC method, WSOC-levoglucosan method, and PMF-based methods were comparable, and the potential errors for different SOC estimation methods were discussed.

SUMMARY DNA modifications undergo genome-wide changes during development, play a central role in epigenetic gene regulation, and preserve genome stability. Ten-eleven translocation (TET) proteins catalyze the oxidation of 5-methylcytosine (5mC) and are implicated in DNA demethylation and the regulation of gene expression (Chen et al., 2013; Ficz et al., 2011; Ito et al., 2011; Khoueiry et al., 2017; Koh et al., 2011; Pfaffeneder et al., 2011; Szwagierczak et al., 2010; Tahiliani et al., 2009; Vella et al., 2013; Williams et al., 2011; Wu et al., 2011; Xiong et al., 2016). However, the degree to which the gene regulatory effects of TET proteins depend on catalytic functions and the extent to which oxidative cytosine modifications represent intermediates of active DNA demethylation or serve as stable epigenetic marks still remains unclear. Here, we dissect the stage-specific catalytic and non-catalytic contributions of TET1 to the regulation of the methylome and transcriptome in the transition from naïve to primed pluripotency. Whereas non-catalytic functions of TET1 prevent the premature exit from pluripotency, we find that the catalytic activity of TET1 is necessary for the expression of the naïve pluripotency marker DPPA3 (STELLA/PGC7)(Hayashi et al., 2008). DPPA3 in turn binds and displaces UHRF1 from nuclear methylation sites to the cytoplasm, thereby impairing the recruitment and activity of the maintenance DNA methyltransferase DNMT1. Collectively, our work delineates catalytic and non-catalytic functions of TET1, uncovers the mechanism of TET1-governed DNA demethylation, and reveals the mechanistic basis by which DPPA3 antagonizes global DNA methylation.