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<jats:title>Handedness at the edge of a line</jats:title> <jats:p> Topological insulators are characterized by conducting boundary states. For those existing as two-dimensional (2D) materials, the boundaries are lines, the edge currents are 1D, and their two spin components flow in opposite directions. To address whether this handedness also applies to the edge states of 1D topological systems, Cheon <jats:italic>et al.</jats:italic> deposited indium atoms on the surface of silicon, where the atoms formed wires consisting of double zigzag chains. The chains underwent distortions that caused topological edge states called solitons to appear under certain conditions. The solitons came in three flavors, two of which had a definite handedness. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="182" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aaa7055">182</jats:related-article> </jats:p>

<jats:title>Accounting for surface coordination</jats:title> <jats:p> The exploration of heterogeneous catalysts using first-principles calculations can be daunting because the large number of atoms and possible surface geometries. Calle-Vallejo <jats:italic>et al.</jats:italic> describe a simpler metric for assessing optimal reactivity: a weighted average of surface coordination that includes second-nearest neighbors (see the Perspective by Stephens <jats:italic>et al.</jats:italic> ). The calculations identified three approaches for introducing cavity sites into the platinum(111) surface to improve its performance for the oxygen reduction reaction used in fuel cells. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="185" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aab3501">185</jats:related-article> , see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="164" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aad3716">164</jats:related-article> </jats:p>

<jats:title>Comparing active site reactivity</jats:title> <jats:p> Noble metal nanoparticles often exhibit behaviors distinct from atomic and bulk versions of the same material. Gold and platinum dispersed on metal oxide supports, for example, show remarkable low-temperature reactivity for carbon monoxide (CO) oxidation by oxygen or water. Ding <jats:italic>et al.</jats:italic> used infrared spectroscopy to identify CO adsorbed on isolated platinum atoms or nanoparticles dispersed on zeolite and oxide supports. Temperature-programmed desorption studies showed that CO reacted at much lower temperatures when adsorbed on nanoparticles versus on isolated metal atoms. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="189" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aac6368">189</jats:related-article> </jats:p>

<jats:title>The glacial way of wearing away</jats:title> <jats:p> The rate at which glaciers erode landscapes is an important but poorly constrained relationship. Herman <jats:italic>et al.</jats:italic> tackle this issue by considering the Franz Josef alpine glacier in New Zealand. The amount of sediment piling up at the edge of the glacier provided erosion rates, whereas remote sensing allowed for simultaneous tracking of glacial motion. The result was a nonlinear relationship, suggesting that fast glaciers are much more effective at gouging landscapes. This could explain the paradox of why long-term erosion rates are so much lower in polar regions with more permanent glaciers. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="193" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aab2386">193</jats:related-article> </jats:p>

<jats:title>A little bit of math goes a long way</jats:title> <jats:p> Children's emerging language skills are supported when their caregivers read to them at home. Math skills, however, are often relegated to the schools. Berkowitz <jats:italic>et al.</jats:italic> developed a mobile-device app designed to help caregivers bring a little bit of math into the home. Improved math skills were apparent within months for elementary school students. Improvements were most dramatic in families where the caregivers reported themselves to be anxious about math. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="196" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aac7427">196</jats:related-article> </jats:p>

<jats:title>Secondary cell walls built with speed</jats:title> <jats:p> Plant cell walls provide the cellulose that is integral for wood, cotton fiber, and many biofuels. Cellulose is synthesized outside the cell membrane by cellulose synthase enzymes. Much of the secondary cell wall, responsible for the sturdiness of wood, is formed by xylem cells embedded in the core of the plant. Watanabe <jats:italic>et al.</jats:italic> leveraged ectopic expression to bring xylem-style cellulose synthase activity to the epidermal surface of the plant (see the Perspective by Schneider and Persson). Combining this improved accessibility with fluorescent tagging showed that secondary cell walls are built faster than primary cell walls, perhaps due to increased velocity and density of cellulose synthase complexes. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="198" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aac7446">198</jats:related-article> , see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="156" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aad3200">156</jats:related-article> </jats:p>

<jats:title> <jats:italic>Striga</jats:italic> uses a hypersensitive receptor </jats:title> <jats:p> The strigolactone hormones govern plant growth and development. A nasty parasitic weed, <jats:italic>Striga</jats:italic> , senses traces of these hormones to identify its targets. After functionally characterizing several strigolactone receptors from <jats:italic>Striga</jats:italic> , Toh <jats:italic>et al.</jats:italic> solved the crystal structure of one that is especially sensitive. The structure shows an unexpectedly large ligand-binding pocket, which may explain how <jats:italic>Striga</jats:italic> manages to sense picomolar concentrations of the range of strigolactones. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="203" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aac9476">203</jats:related-article> </jats:p>

<jats:title>Is cancer immunotherapy a private affair?</jats:title> <jats:p> Immune checkpoint blockade, a relatively new cancer treatment, substantially extends the survival of a subset of patients. Previous work has shown that patients whose tumors harbor the largest number of mutations—and thus produce a large number of “neoantigens” recognized as foreign by the immune system—are most likely to benefit. Expanding on these earlier studies, Van Allen <jats:italic>et al.</jats:italic> studied over 100 patients with melanoma and found a similar correlation (see the Perspective by Gubin and Schreiber). There was no evidence, however, that specific neoantigen sequences were shared by patients who responded. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="207" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aad0095">207</jats:related-article> , see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="158" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aad4140">158</jats:related-article> </jats:p>

<jats:title>Cancer as a case of uncontrolled traffic</jats:title> <jats:p> Healthy cells are like skilled air traffic controllers. They continually move proteins to and from the cellular destinations where they are needed, usually without mishap, through an elaborate system of endomembranes. Wheeler <jats:italic>et al.</jats:italic> show that a glitch in the traffic control system can help propel a cell toward malignancy (see the Perspective by Ferguson). RAB35, a protein previously implicated in endomembrane trafficking, is a key regulator of a well-known oncogenic signaling pathway. Mutations in RAB35 found in certain human tumors aberrantly activate this pathway and cause mislocalization of a factor that promotes cell growth. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="211" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aaa4903">211</jats:related-article> , see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="162" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aad3575">162</jats:related-article> </jats:p>

<jats:title>Orchestrating a viral takeover</jats:title> <jats:p> For some pathogenic viruses, outbreaks occur when a new viral strain emerges and displaces the endemic strain. How such a takeover occurs at a molecular level, however, remains an open question. Manokaran <jats:italic>et al.</jats:italic> examined one example, the emergence of a new clade of dengue virus (DENV) that caused an outbreak in Puerto Rico in 1994. The epidemic strain produced elevated amounts of subgenomic flavivirus RNA (sfRNA), a viral noncoding RNA, relative to amounts of genomic viral RNA. sfRNA bound to and inhibited TRIM25, a protein important for activating the host's antiviral response, and so by reducing host immunity was able to increase its own fitness. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6257" page="217" related-article-type="in-this-issue" vol="350" xlink:href="10.1126/science.aab3369">217</jats:related-article> </jats:p>