Darwin, o biofísico Ken Dill 'falou e disse': as máquinas de proteínas são MÁQUINAS, não são METÁFORAS!!!

Alô ETs, disquem 0800-NASA

Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life

Schwieterman Edward W. , Kiang Nancy Y. , Parenteau Mary N. , Harman Chester E. , DasSarma Shiladitya , Fisher Theresa M. , Arney Giada N. , Hartnett Hilairy E. , Reinhard Christopher T. , Olson Stephanie L. , Meadows Victoria S. , Cockell Charles S. , Walker Sara I. , Grenfell John Lee , … Show all Authors 

Published Online:1 Jun 2018 https://doi.org/10.1089/ast.2017.1729

Source/Fonte: MovieWeb

Abstract

In the coming years and decades, advanced space- and ground-based observatories will allow an unprecedented opportunity to probe the atmospheres and surfaces of potentially habitable exoplanets for signatures of life. Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet. Aided by the universality of the laws of physics and chemistry, we turn to Earth's biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere. Considering the insights gained from modern and ancient Earth, and the broader array of hypothetical exoplanet possibilities, we have compiled a comprehensive overview of our current understanding of potential exoplanet biosignatures, including gaseous, surface, and temporal biosignatures. We additionally survey biogenic spectral features that are well known in the specialist literature but have not yet been robustly vetted in the context of exoplanet biosignatures. We briefly review advances in assessing biosignature plausibility, including novel methods for determining chemical disequilibrium from remotely obtainable data and assessment tools for determining the minimum biomass required to maintain short-lived biogenic gases as atmospheric signatures. We focus particularly on advances made since the seminal review by Des Marais et al. The purpose of this work is not to propose new biosignature strategies, a goal left to companion articles in this series, but to review the current literature, draw meaningful connections between seemingly disparate areas, and clear the way for a path forward. 

Key Words: Exoplanets—Biosignatures—Habitability markers—Photosynthesis—Planetary surfaces—Atmospheres—Spectroscopy—Cryptic biospheres—False positives. Astrobiology 18, 663–708.

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A vida, o universo, e tudo - 42 questões fundamentais

Life, the Universe, and everything—42 fundamental questions

Roland E Allen 1 and Suzy Lidström 2,3

Published 15 November 2016 • © 2016 The Royal Swedish Academy of Sciences

Physica Scripta, Volume 92, Number 1 

Focus Issue on 21st Century Frontiers

Author affiliations

1 Department of Physics and Astronomy, Texas A&M University College Station, Texas 77843, USA

2 Department of Physics and Astronomy, Uppsala University SE-75120 Uppsala, Sweden

3 Physica Scripta, Royal Swedish Academy of Sciences SE-104 05 Stockholm, Sweden

Dates

Received 5 August 2016 Accepted 24 October 2016 

Published 15 November 2016

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Peer review information

Method: Single-blind

Revisions: 1

Screened for originality? Yes

Citation

Roland E Allen and Suzy Lidström 2017 Phys. Scr. 92 012501

DOI https://doi.org/10.1088/0031-8949/92/1/012501

Source/Fonte

Abstract

In The Hitchhiker's Guide to the Galaxy, by Douglas Adams, the Answer to the Ultimate Question of Life, the Universe, and Everything is found to be 42—but the meaning of this is left open to interpretation. We take it to mean that there are 42 fundamental questions which must be answered on the road to full enlightenment, and we attempt a first draft (or personal selection) of these ultimate questions, on topics ranging from the cosmological constant and origin of the Universe to the origin of life and consciousness.

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Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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Dan Graur, o DNA "Lixo" é CRUCIAL no desenvolvimento de embriões!!!

A LINE1-Nucleolin Partnership Regulates Early Development and ESC Identity

Michelle Percharde, Chih-Jen Lin, Yafei Yin, Juan Guan, Gabriel A. Peixoto, Aydan Bulut-Karslioglu 6, Steffen Biechele, Bo Huang, Xiaohua Shen, Miguel Ramalho-Santos 7, 8

6 Present address: Max Planck Institute for Molecular Genetics, Berlin, Germany

7 Present address: Lunenfeld-Tanenbaum Research Institute and Department of Molecular Genetics, University of Toronto, Toronto, ON M5T 3H7, Canada

8 Lead Contact

Publication stage: In Press Corrected Proof

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DOI: https://doi.org/10.1016/j.cell.2018.05.043

Article Info

Publication History

Published: June 21, 2018 Accepted: May 17, 2018

Received in revised form: March 20, 2018 Received: August 12, 2017

In these two two-cell mouse embryos, the surface of the embryos is outlined in orange, the DNA in the nucleus is indicated in blue and the activity of the LINE-1 gene is indicated via bright red spots.

Ramalho-Santos lab/UCSF - Source/Fonte

Highlights

• LINE1 RNA is abundant and nuclear in mouse ESCs and pre-implantation embryos

• LINE1 knockdown inhibits ESC self-renewal and induces transition to a 2C state

• LINE1 RNA recruits Nucleolin/Kap1 to repress Dux and activate rRNA synthesis

• In embryos, LINE1 inhibition causes persistence of the 2C program and impairs ZGA

Summary

Transposable elements represent nearly half of mammalian genomes and are generally described as parasites, or “junk DNA.” The LINE1 retrotransposon is the most abundant class and is thought to be deleterious for cells, yet it is paradoxically highly expressed during early development. Here, we report that LINE1 plays essential roles in mouse embryonic stem cells (ESCs) and pre-implantation embryos. In ESCs, LINE1 acts as a nuclear RNA scaffold that recruits Nucleolin and Kap1/Trim28 to repress Dux, the master activator of a transcriptional program specific to the 2-cell embryo. In parallel, LINE1 RNA mediates binding of Nucleolin and Kap1 to rDNA, promoting rRNA synthesis and ESC self-renewal. In embryos, LINE1 RNA is required for Dux silencing, synthesis of rRNA, and exit from the 2-cell stage. The results reveal an essential partnership between LINE1 RNA, Nucleolin, Kap1, and peri-nucleolar chromatin in the regulation of transcription, developmental potency, and ESC self-renewal.

Keywords:

LINE1, retrotransposons, Nucleolin, Kap1, Dux, MERVL, hypertranscription, rRNA, 2-cell stage, ESCs

Source/Fonte: Cell

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Darwin, mais complexidade - mensagens encriptadas em processos biológicos: mero acaso, fortuita necessidade ou design inteligente?

Transient N-6-Methyladenosine Transcriptome Sequencing Reveals a Regulatory Role of m6A in Splicing Efficiency

Annita Louloupi5, Evgenia Ntini5, Thomas Conrad, Ulf Andersson Vang Ørom6

5These authors contributed equally

6Lead Contact

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DOI: https://doi.org/10.1016/j.celrep.2018.05.077 |

Article Info

Publication History

Published: June 19, 2018 Accepted: May 23, 2018

Received in revised form: April 30, 2018 Received: January 10, 2018

User License

Creative Commons Attribution – NonCommercial – NoDerivs (CC BY-NC-ND 4.0)

Source/Fonte: Ulf Andersson Vang Ørom 

Highlights

•A time-resolved high-resolution picture of m6A on nascent RNA transcripts

•m6A is deposited at nascent RNA and in introns

•m6A deposition at splice-junctions increases splicing kinetics

•High m6A levels in introns is associated with slow and alternative splicing

Summary

Splicing efficiency varies among transcripts, and tight control of splicing kinetics is crucial for coordinated gene expression. N-6-methyladenosine (m6A) is the most abundant RNA modification and is involved in regulation of RNA biogenesis and function. The impact of m6A on regulation of RNA splicing kinetics is unknown. Here, we provide a time-resolved high-resolution assessment of m6A on nascent RNA transcripts and unveil its importance for the control of RNA splicing kinetics. We find that early co-transcriptional m6A deposition near splice junctions promotes fast splicing, while m6A modifications in introns are associated with long, slowly processed introns and alternative splicing events. In conclusion, we show that early m6A deposition specifies the fate of transcripts regarding splicing kinetics and alternative splicing.

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A Via Láctea é duas vezes maior do que os cientistas pensavam

A&A 612, L8 (2018)

Letter to the Editor

Disk stars in the Milky Way detected beyond 25 kpc from its center

M. López-Corredoira1,2, C. Allende Prieto1,2, F. Garzón1,2, H. Wang3,4, C. Liu3,4 and L. Deng3,4

1 Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain 

2 Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain 

3 Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China 

4 University of Chinese Academy of Sciences, Beijing 100012, PR China 

Received: 22 February 2018 Accepted: 5 April 2018

Source/Fonte: NASA

Abstract

Context. The maximum size of the Galactic stellar disk is not yet known. Some studies have suggested an abrupt drop-off of the stellar density of the disk at Galactocentric distances R ≳ 15 kpc, which means that in practice no disk stars or only very few of them should be found beyond this limit. However, stars in the Milky Way plane are detected at larger distances. In addition to the halo component, star counts have placed the end of the disk beyond 20 kpc, although this has not been spectroscopically confirmed so far. Aims. Here, we aim to spectroscopically confirm the presence of the disk stars up to much larger distances.

Methods. With data from the LAMOST and SDSS-APOGEE spectroscopic surveys, we statistically derived the maximum distance at which the metallicity distribution of stars in the Galactic plane is distinct from that of the halo populations.

Results. Our analysis reveals the presence of disk stars at R > 26 kpc (99.7% C.L.) and even at R > 31 kpc (95.4% C.L.).

Key words: Galaxy: structure – Galaxy: disk – Galaxy: abundances

© ESO 2018

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O mais antigo mamífero do Brasil viveu na era dos dinossauros

A Late Cretaceous mammal from Brazil and the first radioisotopic age for the Bauru Group

Mariela C. Castro, Francisco J. Goin, Edgardo Ortiz-Jaureguizar, E. Carolina Vieytes, Kaori Tsukui, Jahandar Ramezani, Alessandro Batezelli, Júlio C. A. Marsola, Max C. Langer

Published 30 May 2018. DOI: 10.1098/rsos.18048

Abstract

In the last three decades, records of tribosphenidan mammals from India, continental Africa, Madagascar and South America have challenged the notion of a strictly Laurasian distribution of the group during the Cretaceous. Here, we describe a lower premolar from the Late Cretaceous Adamantina Formation, São Paulo State, Brazil. It differs from all known fossil mammals, except for a putative eutherian from the same geologic unity and Deccanolestes hislopi, from the Maastrichtian of India. The incompleteness of the material precludes narrowing down its taxonomic attribution further than Tribosphenida, but it is larger than most coeval mammals and shows a thin layer of parallel crystallite enamel. The new taxon helps filling two major gaps in the fossil record: the paucity of Mesozoic mammals in more northern parts of South America and of tribosphenidans in the Cretaceous of that continent. In addition, high-precision U-Pb geochronology provided a post-Turonian maximal age (≤87.8 Ma) for the type stratum, which is overlain by the dinosaur-bearing Marília Formation, constraining the age of the Adamantina Formation at the site to late Coniacian–late Maastrichtian. This represents the first radioisotopic age for the Bauru Group, a key stratigraphic unit for the study of Cretaceous tetrapods in Gondwana.

KEYWORDS

Tribosphenida enamel reduction Bauru Basin South America U-Pb geochronology mesozoic

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O formato da água: a estrutura e ligação de hidrogênio nos limites da estabilidade da água líquida

Structure and hydrogen bonding at the limits of liquid water stability

Flaviu Cipcigan, Vlad Sokhan, Glenn Martyna & Jason Crain

Scientific Reports volume 8, Article number: 1718 (2018) | Download Citation

How water molecules are arranged in the liquid around a central reference molecule. The white areas show high-density "shells" while the orange area shows regions where no water molecules can reside.

Source/Fonte: IBM RESEARCH / THILO STOEFERLE

Abstract

Liquid water exhibits unconventional behaviour across its wide range of stability – from its unusually high liquid-vapour critical point down to its melting point and below where it reaches a density maximum and exhibits negative thermal expansion allowing ice to float. Understanding the molecular underpinnings of these anomalies presents a challenge motivating the study of water for well over a century. Here we examine the molecular structure of liquid water across its range of stability, from mild supercooling to the negative pressure and high temperature regimes. We use a recently-developed, electronically-responsive model of water, constructed from gas-phase molecular properties and incorporating many-body, long-range interactions to all orders; as a result the model has been shown to have high transferability from ice to the supercritical regime. We report a link between the anomalous thermal expansion of water and the behaviour of its second coordination shell and an anomaly in hydrogen bonding, which persists throughout liquid water’s range of stability – from the high temperature limit of liquid water to its supercooled regime.

Acknowledgements

This work was supported by the NPL Strategic Research programme and the STFC Hartree Centre’s Innovation Return on Research programme. FSC acknowledges the Scottish Doctoral Training Centre in Condensed Matter Physics, the NPL Postgraduate Institute and EPSRC for funding under an Industrial CASE studentship. We acknowledge use of Hartree Centre, EPCC and NPL computational resources.

Author information

Affiliations

IBM Research UK, Hartree Centre, Daresbury, WA4 4AD, United Kingdom

Flaviu Cipcigan & Jason Crain

STFC Daresbury Laboratory, Daresbury, WA4 4AD, United Kingdom

Vlad Sokhan

IBM T. J. Watson Research Center, Yorktown Heights, New York, 10598, USA

Glenn Martyna

Contributions

F.S.C., V.P.S., G.J.M., J.C. designed research. F.S.C., V.P.S. conducted research. F.S.C., V.P.S., G.J.M., J.C. analysed and interpreted the results. All authors reviewed the manuscript.

Competing Interests

The authors declare that they have no competing interests.

Corresponding author

Correspondence to Flaviu Cipcigan.

About this article

Publication history

Received 13 October 2017 Accepted 14 December 2017

Published 29 January 2018

DOI https://doi.org/10.1038/s41598-017-18975-7

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Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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A água, quem diria, são dois líquidos!

Diffusive dynamics during the high-to-low density transition in amorphous ice

Fivos Perakis, Katrin Amann-Winkel, Felix Lehmkühler, Michael Sprung, Daniel Mariedahl, Jonas A. Sellberg, Harshad Pathak, Alexander Späh, Filippo Cavalca, Daniel Schlesinger, Alessandro Ricci, Avni Jain, Bernhard Massani, Flora Aubree, Chris J. Benmore, Thomas Loerting, Gerhard Grübel, Lars G. M. Pettersson, and Anders Nilsson

PNAS August 1, 2017. 114 (31) 8193-8198; published ahead of print June 26, 2017. https://doi.org/10.1073/pnas.1705303114

Edited by Pablo G. Debenedetti, Princeton University, Princeton, NJ, and approved May 31, 2017 (received for review March 31, 2017)

Source/Fonte: New Scientist

Significance

The importance of a molecular-level understanding of the properties, structure, and dynamics of liquid water is recognized in many scientific fields. It has been debated whether the observed high- and low-density amorphous ice forms are related to two distinct liquid forms. Here, we study experimentally the structure and dynamics of high-density amorphous ice as it relaxes into the low-density form. The unique aspect of this work is the combination of two X-ray methods, where wide-angle X-ray scattering provides the evidence for the structure at the atomic level and X-ray photon-correlation spectroscopy provides insight about the motion at the nanoscale, respectively. The observed motion appears diffusive, indicating liquid-like dynamics during the relaxation from the high-to low-density form.

Abstract

Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid–liquid transition in the ultraviscous regime.

liquid–liquid transitionglass transitionamorphous iceX-ray photon-correlation spectroscopysupercooled water

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