Catálogo de publicaciones - revistas

<jats:title>Shifting frames to make more proteins</jats:title> <jats:p> Severe acute respiratory syndrome coronavirus 2 critically depends on the ribosomal frameshifting that occurs between two large open reading frames in its genomic RNA for expression of viral replicase. Programmed frameshifting occurs during translation, when the ribosome encounters a stimulatory pseudoknot RNA fold. Using a combination of cryo–electron microscopy and biochemistry, Bhatt <jats:italic>et al.</jats:italic> revealed that the pseudoknot resists unfolding as it lodges at the entry of the ribosomal messenger RNA channel. This causes back slippage of the viral RNA, resulting in a minus-1 shift of the reading frame of translation. A partially folded nascent viral polyprotein forms specific interactions inside the ribosomal tunnel that can influence the efficiency of frameshifting. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abf3546, this issue p. <jats:related-article issue="6548" page="1306" related-article-type="in-this-issue" vol="372">1306</jats:related-article> </jats:p>

<jats:title>Imaging reactions across facets</jats:title> <jats:p> Metal nanoparticles used in heterogeneous catalysis can bear different facets with different reaction kinetics. Suchorski <jats:italic>et al.</jats:italic> used field electron microscopy with high spatial (∼2 nanometers) and time (∼2 milliseconds) resolution to study hydrogen oxidation on a curved rhodium crystal that displayed individual nanofacets. They also performed field ion microscopy of the water products. Periodic formation and depletion of subsurface oxygen blocked or allowed hydrogen adsorption, respectively, and led to oscillatory kinetics that could frequency lock between facets but at different frequencies. Surface reconstructions could also induce collapse of spatial coupling of oscillations. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abf8107, this issue p. <jats:related-article issue="6548" page="1314" related-article-type="in-this-issue" vol="372">1314</jats:related-article> </jats:p>

<jats:title>A spinning quantum gas</jats:title> <jats:p> Ultracold atomic gases are very good at simulating electrons in solids but lack one essential party trick: charge. Their neutrality makes it challenging to simulate phenomena such as the quantum Hall effect, which, in the case of charged electrons, is easily induced by an external magnetic field. One way to produce a similar effect in a neutral system is to rotate it, but achieving the equivalent of strong magnetic fields remains difficult. Fletcher <jats:italic>et al.</jats:italic> rotated a gas of trapped sodium atoms, reaching a state in which the gas could be described by a single lowest Landau-level wave-function. The system is expected to be a testbed for studying the behavior of strongly interacting many-body states. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , aba7202, this issue p. <jats:related-article issue="6548" page="1318" related-article-type="in-this-issue" vol="372">1318</jats:related-article> </jats:p>

<jats:title>Capturing exotic magnetism</jats:title> <jats:p> Ferromagnetism is associated with the breaking of time-reversal symmetry, most frequently by the spin degree of freedom. Although the orbital motion of electrons can also contribute to ferromagnetism, in most materials, it is small relative to the spin contribution. Tschirhart <jats:italic>et al.</jats:italic> showed that the reverse is true in an unusual magnetic state hosted by twisted bilayer graphene. Their scanning magnetometry measurements were consistent with ferromagnetism of predominantly orbital origin. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abd3190, this issue p. <jats:related-article issue="6548" page="1323" related-article-type="in-this-issue" vol="372">1323</jats:related-article> </jats:p>

<jats:title>Suppressing nucleation over large areas</jats:title> <jats:p> Although formamidinium-based lead iodide (PbI <jats:sub>2</jats:sub> ) perovskites have a favorable bandgap and good thermal stability, the difficulty in controlling nucleation makes it difficult to grow high-quality, large-area films compared with methylammonium counterparts. Bu <jats:italic>et al.</jats:italic> show that adding <jats:italic>N</jats:italic> -methyl-2-pyrrolidone to the perovskite precursors forms an adduct with PbI <jats:sub>2</jats:sub> that promotes the formation of the desired black α-phase at room temperature. The addition of potassium hexafluorophosphate eliminated hysteresis by passivating interfacial defects and promoted long-term thermal stability at 85°C in unencapsulated devices. Large-area modules (17 square centimeters) achieved power conversion efficiencies of 20.4%. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abh1035, this issue p. <jats:related-article issue="6548" page="1327" related-article-type="in-this-issue" vol="372">1327</jats:related-article> </jats:p>

<jats:title>Really cool mirrors</jats:title> <jats:p> Cooling objects to low temperature can increase the sensitivity of sensors and the operational performance of most devices. Removing most of the thermal vibrations—or phonons—such that the object reaches its motional quantum ground state has been achieved but typically with tiny, nanoscale objects. Using the suspended mirrors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) that form a 10-kg optomechanical oscillator, Whittle <jats:italic>et al.</jats:italic> demonstrate the ability to cool such a large-scale object to nearly the motional ground state. An upgrade to LIGO with such a modification could increase its sensitivity and range to gravitational waves but also extend studies of quantum mechanics to large-scale objects. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abh2634, this issue p. <jats:related-article issue="6548" page="1333" related-article-type="in-this-issue" vol="372">1333</jats:related-article> </jats:p>

<jats:title>Probing CD4 T cell immunity to SARS-CoV-2</jats:title> <jats:p> A better understanding of CD4 <jats:sup>+</jats:sup> T cell responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial to the design of effective next-generation vaccines. Low <jats:italic>et al.</jats:italic> defined and estimated the CD4 <jats:sup>+</jats:sup> T cell repertoire of convalescent COVID-19 patients. After sorting various CD4 <jats:sup>+</jats:sup> T cell subsets, they generated numerous T cell clones that reacted to the SARS-CoV-2 spike protein. A large number of T cell clones from almost all individuals recognized a small conserved immunodominant region within the spike protein receptor-binding domain (RBD). The researchers isolated T cell clones that broadly reacted to the spike protein of other coronaviruses, providing evidence for the recall of preexisting cross-reactive memory T cells after SARS-CoV-2 infection. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abg8985, this issue p. <jats:related-article issue="6548" page="1336" related-article-type="in-this-issue" vol="372">1336</jats:related-article> </jats:p>

<jats:title>Cliff collapse</jats:title> <jats:p> Tall ice cliffs at the edges of ice sheets can collapse under their own weight in spectacular fashion, a process that can considerably hasten ice sheet mass loss. Bassis <jats:italic>et al.</jats:italic> used a dynamic ice model to demonstrate that this kind of collapse can be slowed either by upstream thinning of the ice sheet or by the resistive forces from sea ice and calved debris (see the Perspective by Golledge and Lowry). Conversely, when there is upstream ice thickening, a transition to catastrophic collapse can occur. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abf6271, this issue p. <jats:related-article issue="6548" page="1342" related-article-type="in-this-issue" vol="372">1342</jats:related-article> ; see also abj3266, p. <jats:related-article issue="6548" page="1266" related-article-type="in-this-issue" vol="372">1266</jats:related-article> </jats:p>