Catálogo de publicaciones - revistas

<jats:p> Highlights from the <jats:italic>Science</jats:italic> family of journals </jats:p>

<jats:p>Editors’ selections from the current scientific literature</jats:p>

<jats:title>Perseverance images of a delta on Mars</jats:title> <jats:p> The Perseverance rover landed in Jezero crater, Mars, in February 2021. Earlier orbital images showed that the crater contains an ancient river delta that was deposited by water flowing into a lake billions of years ago. Mangold <jats:italic>et al</jats:italic> . analyzed rover images taken shortly after landing that show distant cliff faces at the edge of the delta. The exposed stratigraphy and sizes of boulders allowed them to determine the past lake level and water discharge rates. An initially steady flow transitioned into intermittent floods as the planet dried out. This history of the delta’s geology provides context for the rest of the mission and improves our understanding of Mars’ ancient climate. —KTS </jats:p>

<jats:title>Sponges and evolutionary origins</jats:title> <jats:p> Sponges represent our distant animal relatives. They do not have a nervous system but do have a simple body for filter feeding. Surveying the cell types in the freshwater sponge <jats:italic>Spongilla lacustris</jats:italic> , Musser <jats:italic>et al</jats:italic> . found that many genes important in synaptic communication are expressed in cells of the small digestive chambers. They found secretory machinery characteristic of the presynapse in small multipolar cells contacting all other cells and also the receptive apparatus of the postsynapse in the choanocytes that generate water flow and digest microbial food. These results suggest that the first directed communication in animals may have evolved to regulate feeding, serving as a starting point on the long path toward nervous system evolution. —BAP </jats:p>

<jats:title>Big molecules build small</jats:title> <jats:p> Actinomycete bacteria are prolific producers of bioactive small molecules such as polyketide antibiotics. These molecules are built by the addition of short carbon units to a growing, protein-tethered chain, either iteratively as in fatty acid synthesis or in a modular fashion by a hand-off from one distinct enzyme complex to the next. Bagde <jats:italic>et al</jats:italic> . and Cogan <jats:italic>et al</jats:italic> . report structures of polyketide synthase modules in action, taking advantage of antibody stabilization of one of the domains. Both groups visualized multiple conformational states and an asymmetric arrangement of domains, providing insight into how these molecular assembly machines transfer substrates from one active site to another. —MAF </jats:p>

<jats:title>Big molecules build small</jats:title> <jats:p> Actinomycete bacteria are prolific producers of bioactive small molecules such as polyketide antibiotics. These molecules are built by the addition of short carbon units to a growing, protein-tethered chain, either iteratively as in fatty acid synthesis or in a modular fashion by a hand-off from one distinct enzyme complex to the next. Bagde <jats:italic>et al</jats:italic> . and Cogan <jats:italic>et al</jats:italic> . report structures of polyketide synthase modules in action, taking advantage of antibody stabilization of one of the domains. Both groups visualized multiple conformational states and an asymmetric arrangement of domains, providing insight into how these molecular assembly machines transfer substrates from one active site to another. —MAF </jats:p>

<jats:title>Careful choreography for a ketone shift</jats:title> <jats:p> Chemists devote tremendous effort to the precise placement of oxygens in molecular frameworks. Wu <jats:italic>et al</jats:italic> . report a convenient method to shift the oxygen in a carbonyl group to an adjacent carbon center. After activation of the oxygen to an alkenyl triflate, cooperative catalysis by palladium and norbornene adds nitrogen to the neighboring carbon while displacing the triflate with hydride. Hydrolysis then produces the desired shifted ketone. The protocol is well suited to late-stage variation of complex molecules during drug optimization. —JSY </jats:p>

<jats:title>Easy aryl reductions</jats:title> <jats:p> The Birch reduction has been widely used for more than half a century to achieve partial reduction of aryl rings by alkali metals at just two diametrically opposed carbon sites. However, the conditions require condensation of caustic gaseous ammonia. A variation developed soon afterward by Benkeser used safer liquid ethylene diamine but was prone to overreduction. By diluting ethylene diamine in tetrahydrofuran solvent, Burrows <jats:italic>et al</jats:italic> . now obtain selectivities comparable to Birch conditions but without the need for condensed ammonia. —JSY </jats:p>

<jats:title>Spontaneous chemistry on aerosol surface</jats:title> <jats:p> Interfacial redox chemistry plays an important role in the formation of gas molecules and aerosol particles. However, the characterization of such heterogeneous processes is challenging, and they are often omitted in chemical kinetics models. Using ambient-pressure x-ray photoelectron spectroscopy combined with molecular dynamics simulations, Kong <jats:italic>et al</jats:italic> . discovered spontaneous redox chemistry promoted by the surface at the first stages of the solvation process on a typical inorganic aerosol surface of ammonium sulfate (see the Perspective by Ruiz-Lopez). Several unexpected species have been identified as being possible products of a sulfate-reducing ammonium oxidation reaction, and this may help to resolve some of the enduring conundrums of atmospheric chemistry. The present results could also be useful for the development of wastewater treatments and other industrial technologies. —YS </jats:p>

<jats:title>Asymmetric carbon coupling at boron</jats:title> <jats:p> The Matteson reaction produces carbon–carbon bonds by coupling halocarbons such as widely available dichloromethane with an alkyl substituent on boron. Sharma <jats:italic>et al</jats:italic> . report asymmetric catalysis of this reaction. Their catalyst, derived from a chiral thiourea, a boronic ester, and an alkyl lithium base, appears to accelerate a chloride abstraction step through its lithium center. The product, still bearing a chloride, can be further modified through stereospecific displacement to generate a wide variety of trisubstituted chiral centers. —JSY </jats:p>