Mais uma hipótese sobre a origem da vida: modelos de precursores potenciais de células resistem às condições simuladas da Terra primitiva

Impact of wet-dry cycling on the phase behavior and compartmentalization properties of complex coacervates

Hadi M. Fares, Alexander E. Marras, Jeffrey M. Ting, Matthew V. Tirrell & Christine D. Keating 

Nature Communications volume 11, Article number: 5423 (2020)

Abstract

Wet-dry cycling on the early Earth is thought to have facilitated production of molecular building blocks of life, but its impact on self-assembly and compartmentalization remains largely unexplored. Here, we investigate dehydration/rehydration of complex coacervates, which are membraneless compartments formed by phase separation of polyelectrolyte solutions. Solution compositions are identified for which tenfold water loss results in maintenance, disappearance, or appearance of coacervate droplets. Systems maintaining coacervates throughout the dehydration process are further evaluated to understand how their compartmentalization properties change with drying. Although added total RNA concentrations increase tenfold, RNA concentration within coacervates remains steady. Exterior RNA concentrations rise, and exchange rates for encapsulated versus free RNAs increase with dehydration. We explain these results in light of the phase diagram, with dehydration-driven ionic strength increase being particularly important in determining coacervate properties. This work shows that wet-dry cycling can alter the phase behavior and protocell-relevant functions of complex coacervates.

FREE PDF GRATIS: Nature Communications Sup. Info.

Editores de revistas científicas não devem contribuir para politizar a ciência!

 Science journal editors shouldn’t contribute to politicizing science

By GENEVIEVE P. KANTER OCTOBER 23, 2020

Source/Fonte: Samuel Corum - Getty Images

When the editors of some of the world’s leading science journals agree on something, it is generally safe to assume that they are correct. So when prominent journals like Science, Nature, and the New England Journal of Medicine recently published editorials excoriating President Trump’s deadly bungling of the pandemic response and suppression of scientific activity, the editors accurately spotlighted the troubling deficiencies of the current administration.

But in advocating against or endorsing a presidential candidate, these editors made a grave error. In taking this extraordinary step, they made themselves vulnerable to charges of bias, overstepped their roles as science editors, and succumbed to the politicization of science that they and many other scientists find so alarming.

At first glance, these appear to be similar to run-of-the-mill newspaper endorsements. This analogy, however, is not quite right. At a newspaper, there is a wall between the news operation and the editorial office. It exists to prevent biases of the editorial staff from influencing news reporting. No such wall exists for science journals. The editors who write the editorials are the same ones who evaluate manuscripts and make the final decisions on whether to publish them.

There’s another problem: This political advocacy unnecessarily invites allusions to cronyism, echoing a less savory time when wealthy newspaper owners used their editorial pages to extol the merits of their political chums. Indeed, because of fears surrounding the appearance of undue influence and bias, many newspapers in recent years have abandoned political endorsements.

Read more here: STAT News

Transporte de membranas - elevadores condutores para o interior e exterior das células: mero acaso, fortuita necessidade ou design inteligente?

Structural basis for the reaction cycle of DASS dicarboxylate transporters

David B Sauer, Noah Trebesch, Jennifer J Marden, Nicolette Cocco, Jinmei Song, Akiko Koide, Shohei Koide, Emad Tajkhorshid Is a corresponding author, Da-Neng Wang Is a corresponding author

Skirball Institute of Biomolecular Medicine, New York University School of Medicine, United States; Department of Cell Biology, New York University School of Medicine, United States; NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, United States; Perlmutter Cancer Center, New York University School of Medicine, United States; Department of Medicine, New York University School of Medicine, United States; Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, United States

Research Article Sep 1, 2020

Abstract

Citrate, α-ketoglutarate and succinate are TCA cycle intermediates that also play essential roles in metabolic signaling and cellular regulation. These di- and tricarboxylates are imported into the cell by the divalent anion sodium symporter (DASS) family of plasma membrane transporters, which contains both cotransporters and exchangers. While DASS proteins transport substrates via an elevator mechanism, to date structures are only available for a single DASS cotransporter protein in a substrate-bound, inward-facing state. We report multiple cryo-EM and X-ray structures in four different states, including three hitherto unseen states, along with molecular dynamics simulations, of both a cotransporter and an exchanger. Comparison of these outward- and inward-facing structures reveal how the transport domain translates and rotates within the framework of the scaffold domain through the transport cycle. Additionally, we propose that DASS transporters ensure substrate coupling by a charge-compensation mechanism, and by structural changes upon substrate release.

FREE PDF GRATIS: eLIFE