Catálogo de publicaciones - revistas

<jats:title> Lending a Hand to CO <jats:sub>2</jats:sub> Reduction </jats:title> <jats:p> Although plants and microbes have been reducing CO <jats:sub>2</jats:sub> with ease for millennia, people still find it extremely challenging. A cost-effective synthetic scheme for transforming CO <jats:sub>2</jats:sub> into fuels and commodity chemicals would be a double boon, lowering atmospheric concentration of the greenhouse gas while supplementing (and perhaps ultimately replacing) dwindling petroleum feedstocks. Toward this end, <jats:bold> Costentin <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="90" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1224581">90</jats:related-article> ) show that an iron catalyst for the electrochemical reduction of CO <jats:sub>2</jats:sub> to CO gets an efficiency boost from phenol substituents appended to the ligand framework. </jats:p>

<jats:title>Watching Supercoiled DNA</jats:title> <jats:p> The DNA double helix can undergo additional twisting, or supercoiling, that plays a role in transciption and protein binding, in part by bringing distant DNA locations together. The process forms intertwined loops, called plectonemes, and van <jats:bold> Loenhout <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="94" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1225810">94</jats:related-article> , published online 13 September; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6103" page="56" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1228656">Sheinin and Wang</jats:related-article> </jats:bold> ) visualized plectoneme dynamics of fluorescently labeled, 21-kilobase tethered DNA molecules using magnetic tweezers to apply twisting forces. Plectonemes could diffuse along the DNA, but move more rapidly if they “hopped”—nucleating a plectoneme at a new position. </jats:p>

<jats:title>A Toothy Problem</jats:title> <jats:p> Large mammalian herbivores such as horses and bison are well known to possess a complex, grinding dentition that facilitates processing of their tough, cellulose-rich plant diet. Hadrosaurid, or duck-billed, dinosaurs also possessed complex teeth, but how this was achieved has been unknown because reptiles typically possess simple teeth. <jats:bold> Erickson <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="98" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1224495">98</jats:related-article> ) show how Hadrosaurs evolved teeth composed of six tissues, which allowed for the development of tooth complexity rivaling, or exceeding, that of modern herbivorous mammals. </jats:p>

<jats:title>Grinding Out Earthquake Physics</jats:title> <jats:p> Simulating earthquakes in the lab produces events that are often orders of magnitude lower in energy than large, damaging earthquakes; thus, it is unclear how well the behavior along these simulated faults extrapolates to the physics of large earthquakes. <jats:bold> Chang <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="101" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1221195">101</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6103" page="54" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1227085"> <jats:bold>Shimamoto and Togo</jats:bold> </jats:related-article> <jats:bold /> ) used a rotary apparatus that spins in tandem at high speeds with a disc-shaped rock sample, producing energies comparable to earthquakes of magnitudes 4 to 8. Experiments using both granite and dolomite samples suggest that the weakening of slip along faults during large earthquakes is a product of intense accelerations associated with the rupture event. </jats:p>

<jats:title>Puzzling Through Gravity</jats:title> <jats:p> Much of the excitement of scientific discovery seems to get lost when science is taught as facts by lectures. <jats:bold> Granger <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="105" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1223709">105</jats:related-article> ) present a large study of outcomes comparing inquiry-based teaching with more traditional teaching methods. Over 2000 students were involved, in 125 classrooms of 4th- and 5th-graders. The classes studied space-science with a curriculum that uses models and evidence to entice students into improving their own understanding of the science. Students who were encouraged to use evidence to support their models seemed to develop improved knowledge of content. </jats:p>

<jats:title>Gut, Heal Thyself</jats:title> <jats:p> Foods, drugs, and pathogens all represent possible threats to our guts on a daily basis. Fortunately, the gut is quite good at repairing itself—but how? Working in mice, <jats:bold> Miyoshi <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="108" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1223821">108</jats:related-article> , published online 6 September; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6103" page="51" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1229414">Barrett</jats:related-article> </jats:bold> ) selectively injured intestinal crypts containing intestinal stem cells and observed therepair process. The noncanonical Wnt ligand, Wnt5a, was required for crypt regeneration. Wnt5a inhibited intestinal stem cell proliferation, which paradoxically promoted regeneration of crypt tissue. </jats:p>

<jats:title>Plant Anti-Insect Armaments</jats:title> <jats:p> Because individual plants are unable to relocate, they are subject to extreme selection by the insects feeding upon them. One means by which plants suppress herbivory is to produce toxic compounds to deter feeding (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6103" page="50" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1228893">Hare</jats:related-article> </jats:bold> ). <jats:bold> Agrawal <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="113" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1225977">113</jats:related-article> ) compared pesticide–treated or untreated evening primroses. Over 5 years of pesticide treatment, the production of defensive chemicals in the fruit reduced and flowering times shifted, and the primrose's competitive ability against dandelions improved. <jats:bold> Züst <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="116" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1226397">116</jats:related-article> ) examined large-scale geographic patterns in a polymorphic chemical defense locus in the model plant <jats:italic>Arabidopsis thaliana</jats:italic> and found that it is matched by changes in the relative abundance of two specialist aphids. Thus, herbivory has strong and immediate effects on the local genotypic composition of plants and traits associated with herbivore resistance. </jats:p>

<jats:title>Plant Anti-Insect Armaments</jats:title> <jats:p> Because individual plants are unable to relocate, they are subject to extreme selection by the insects feeding upon them. One means by which plants suppress herbivory is to produce toxic compounds to deter feeding (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6103" page="50" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1228893">Hare</jats:related-article> </jats:bold> ). <jats:bold> Agrawal <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="113" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1225977">113</jats:related-article> ) compared pesticide–treated or untreated evening primroses. Over 5 years of pesticide treatment, the production of defensive chemicals in the fruit reduced and flowering times shifted, and the primrose's competitive ability against dandelions improved. <jats:bold> Züst <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="116" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1226397">116</jats:related-article> ) examined large-scale geographic patterns in a polymorphic chemical defense locus in the model plant <jats:italic>Arabidopsis thaliana</jats:italic> and found that it is matched by changes in the relative abundance of two specialist aphids. Thus, herbivory has strong and immediate effects on the local genotypic composition of plants and traits associated with herbivore resistance. </jats:p>

<jats:title>Of Microbes and Cancer</jats:title> <jats:p> Inflammation is a well-established driver of tumorigenesis. For example, patients with inflammatory bowel disease have an elevated risk of developing colorectal cancer (CRC). Whether the gut microbiota also contributes to the development of CRC is less well understood. <jats:bold> Arthur <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="120" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1224820">120</jats:related-article> , published online 16 August; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6103" page="52" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1229905"> <jats:bold>Schwabe and Wang</jats:bold> </jats:related-article> </jats:bold> ) now show that the microbiota does indeed promote tumorigenesis in an inflammation-driven model of CRC in mice. Although germ-free mice were protected against developing cancer, colonization of mice with <jats:italic>Escherichia coli</jats:italic> was sufficient to drive tumorigenesis. </jats:p>

<jats:title>Regulating Opioid Responses</jats:title> <jats:p> Different drugs of abuse are thought to highjack similar reward systems in the brain using common mechanisms. However, <jats:bold> Koo <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="124" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1222265">124</jats:related-article> ) now observe that some of the neural mechanisms that regulate opiate reward can be both different and even opposite to those that regulate reward by stimulant drugs. While knockdown of brain-derived neurotrophic factor (BDNF) in the ventral tegmental area in mice antagonized the response to cocaine, the same manipulation strengthened the potential of opiates to increase dopamine neuron excitability. Optogenetic stimulation of dopaminergic terminals in the nucleus accumbens could counteract the effects of BDNF on morphine reward blockade. </jats:p>