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  • 1
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: The pyrite-type high-pressure form of FeOOH Nature 547, 7662 (2017). doi:10.1038/nature22823 Authors: Masayuki Nishi, Yasuhiro Kuwayama, Jun Tsuchiya & Taku Tsuchiya Water transported into Earth’s interior by subduction strongly influences dynamics such as volcanism and plate tectonics. Several recent studies have reported hydrous minerals to be stable at pressure and temperature conditions representative of Earth’s deep interior, implying that surface water may be transported as far as the core–mantle boundary. However, the hydrous mineral goethite, α-FeOOH, was recently reported to decompose under the conditions of the middle region of the lower mantle to form FeO2 and release H2, suggesting the upward migration of hydrogen and large fluctuations in the oxygen distribution within the Earth system. Here we report the stability of FeOOH phases at the pressure and temperature conditions of the deep lower mantle, based on first-principles calculations and in situ X-ray diffraction experiments. In contrast to previous work suggesting the dehydrogenation of FeOOH into FeO2 in the middle of the lower mantle, we report the formation of a new FeOOH phase with the pyrite-type framework of FeO6 octahedra, which is much denser than the surrounding mantle and is stable at the conditions of the base of the mantle. Pyrite-type FeOOH may stabilize as a solid solution with other hydrous minerals in deeply subducted slabs, and could form in subducted banded iron formations. Deep-seated pyrite-type FeOOH eventually dissociates into Fe2O3 and releases H2O when subducted slabs are heated at the base of the mantle. This process may cause the incorporation of hydrogen into the outer core by the formation of iron hydride, FeHx, in the reducing environment of the core–mantle boundary.
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    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Allelic reprogramming of 3D chromatin architecture during early mammalian development Nature 547, 7662 (2017). doi:10.1038/nature23263 Authors: Zhenhai Du, Hui Zheng, Bo Huang, Rui Ma, Jingyi Wu, Xianglin Zhang, Jing He, Yunlong Xiang, Qiujun Wang, Yuanyuan Li, Jing Ma, Xu Zhang, Ke Zhang, Yang Wang, Michael Q. Zhang, Juntao Gao, Jesse R. Dixon, Xiaowo Wang, Jianyang Zeng & Wei Xie In mammals, chromatin organization undergoes drastic reprogramming after fertilization. However, the three-dimensional structure of chromatin and its reprogramming in preimplantation development remain poorly understood. Here, by developing a low-input Hi-C (genome-wide chromosome conformation capture) approach, we examined the reprogramming of chromatin organization during early development in mice. We found that oocytes in metaphase II show homogeneous chromatin folding that lacks detectable topologically associating domains (TADs) and chromatin compartments. Strikingly, chromatin shows greatly diminished higher-order structure after fertilization. Unexpectedly, the subsequent establishment of chromatin organization is a prolonged process that extends through preimplantation development, as characterized by slow consolidation of TADs and segregation of chromatin compartments. The two sets of parental chromosomes are spatially separated from each other and display distinct compartmentalization in zygotes. Such allele separation and allelic compartmentalization can be found as late as the 8-cell stage. Finally, we show that chromatin compaction in preimplantation embryos can partially proceed in the absence of zygotic transcription and is a multi-level hierarchical process. Taken together, our data suggest that chromatin may exist in a markedly relaxed state after fertilization, followed by progressive maturation of higher-order chromatin architecture during early development.
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  • 3
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Phase separation drives heterochromatin domain formation Nature 547, 7662 (2017). doi:10.1038/nature22989 Authors: Amy R. Strom, Alexander V. Emelyanov, Mustafa Mir, Dmitry V. Fyodorov, Xavier Darzacq & Gary H. Karpen Constitutive heterochromatin is an important component of eukaryotic genomes that has essential roles in nuclear architecture, DNA repair and genome stability, and silencing of transposon and gene expression. Heterochromatin is highly enriched for repetitive sequences, and is defined epigenetically by methylation of histone H3 at lysine 9 and recruitment of its binding partner heterochromatin protein 1 (HP1). A prevalent view of heterochromatic silencing is that these and associated factors lead to chromatin compaction, resulting in steric exclusion of regulatory proteins such as RNA polymerase from the underlying DNA. However, compaction alone does not account for the formation of distinct, multi-chromosomal, membrane-less heterochromatin domains within the nucleus, fast diffusion of proteins inside the domain, and other dynamic features of heterochromatin. Here we present data that support an alternative hypothesis: that the formation of heterochromatin domains is mediated by phase separation, a phenomenon that gives rise to diverse non-membrane-bound nuclear, cytoplasmic and extracellular compartments. We show that Drosophila HP1a protein undergoes liquid–liquid demixing in vitro, and nucleates into foci that display liquid properties during the first stages of heterochromatin domain formation in early Drosophila embryos. Furthermore, in both Drosophila and mammalian cells, heterochromatin domains exhibit dynamics that are characteristic of liquid phase-separation, including sensitivity to the disruption of weak hydrophobic interactions, and reduced diffusion, increased coordinated movement and inert probe exclusion at the domain boundary. We conclude that heterochromatic domains form via phase separation, and mature into a structure that includes liquid and stable compartments. We propose that emergent biophysical properties associated with phase-separated systems are critical to understanding the unusual behaviours of heterochromatin, and how chromatin domains in general regulate essential nuclear functions.
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Don’t pay prizes for published science Nature 547, 7662 (2017). doi:10.1038/547137a China and other countries should look again at how they pay bonuses and allocate grants that are based on individual research papers.
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  • 5
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Proposed US public-health chief is a champion for women and children Nature 547, 7662 (2017). doi:10.1038/547137b In sharp contrast to President Trump, Brenda Fitzgerald has put maternal and child health at the heart of her policies.
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  • 6
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Panda diplomats, smuggled relics and a nuclear-weapons treaty Nature 547, 7662 (2017). http://www.nature.com/doifinder/10.1038/547142a The week in science: 7–13 July 2017.
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  • 7
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Why planetary scientists want better fake space dirt Nature 547, 7662 (2017). http://www.nature.com/doifinder/10.1038/nature.2017.22228 Author: Alexandra Witze Artificial soils that mimic the surfaces of the Moon, Mars and asteroids are hard to make — and often miss the mark.
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  • 8
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Massive database of 182,000 leaves is helping predict plants' family trees Nature 547, 7662 (2017). http://www.nature.com/doifinder/10.1038/nature.2017.22230 Author: Heidi Ledford The technique could be used on everything from flowers to cells to examine the factors that influence the shapes of plant parts.
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  • 9
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Snyder replies Nature 547, 7662 (2017). doi:10.1038/nature22804 Author: Carolyn W. Snyder Replying toG. A.Schmidtet al. Nature547, http://dx.doi.org/10.1038/nature22803 (2017)The Earth system sensitivity (ESS) summarizes the feedback behaviour of Earth’s climate system and includes ice sheets, vegetation and dust as internal feedbacks. This definition of the ESS is
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  • 10
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    Nature Publishing Group (NPG)
    In: Nature
    Publication Date: 2017-07-13
    Description: Precision measurement: Sensing past the quantum limit Nature 547, 7662 (2017). doi:10.1038/547164a Authors: Christopher G. Baker & Warwick P. Bowen Quantum physics ultimately constrains how well sensors of position, speed and acceleration can perform. A hybrid quantum system that avoids these constraints could give rise to improved sensor technologies. See Letter p.191
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