This Week in Science

Science  06 Feb 2015:
Vol. 347, Issue 6222, pp. 623
  1. Thermal Measurement

    Plasmons can map temperature on the nanoscale

    1. Phil Szuromi

    False-color temperature map of 80-nm-thick, 100-nm-wide serpentine aluminium

    CREDIT: MECKLENBURG ET AL.

    Determining temperature on small length scales can be challenging: Direct probes can alter sample temperature, and radiation probes are limited by the wavelength of the light used. Mecklenberg et al. show how the bulk plasmon resonance of aluminum can be used to map the temperature on the nanoscale with transmission electron microscopy (see the Perspective by Colliex). Many other metals and semiconductors also have plasmon resonances that could also be used for temperature imaging.

    Science, this issue p. 629; see also p. 611

  2. Exoplanet Dynamics

    Can't keep hot sides hot and cold sides cold?

    1. Margaret M. Moerchen

    On Earth, we're accustomed to cycles of day and night, which drive a complex thermal relationship between the ground and atmosphere. Some exoplanets very close to their stars aren't so lucky and are generally assumed to be locked by tides into hemispheres of unchanging day and night. The thick atmosphere of Venus is thought to keep it from the same fate, but Leconte et al. present models showing that even a much sparser atmosphere may suffice for lower-mass stars. The non-instantaneous thermal response of the planet (when the hottest time of day is after noon) may speed up or slow down the planet. Such thermal tides may be important in assessing potential extraterrestrial habitable zones.

    Science, this issue p. 632

  3. Noncovalent Assembly

    Popping open one by one into polymers

    1. Jake Yeston

    We rarely board airplanes by joining the back of a single well-ordered line. More often, we jostle around in one of several bulging crowds that merge haphazardly near the gate. Roughly speaking, these processes are analogous to the chain growth and step growth mechanisms of polymer assembly at the molecular level. Kang et al. present a strategy to link molecular building blocks through hydrogen bonding in accord with the well-controlled chain growth model. The molecules start out curled inward, as they engage in internal hydrogen bonding, until an initiator pulls one open; that molecule is then in the right conformation to pull a partner into the growing chain, poising it to pull in yet another, and so forth down the line.

    Science, this issue p. 646

  4. Ecological Feedbacks

    Termites can stabilize tropical grasslands

    1. Andrew M. Sugden

    Spotty vegetation patterns in tropical savannas and grasslands can be a warning sign of imminent desertification. However, Bonachela et al. find that termites can also produce spotty patterns. Their theoretical study, confirmed by field data from Kenya, shows that patterns produced by termite mounds are not harbingers of desertification. Indeed, the presence of termites buffers these ecosystems against climate change.

    Science, this issue p. 651

  5. Transplantation

    Long-term tracking of transplanted T cells

    1. Angela Colmone

    Clinical trials can be an untapped source of experimental data that can be leveraged to explore both basic and pathological biology in humans. Biasco et al. took advantage of two different gene therapy trials for inherited immunodeficiency to track T cell fate over the long term in humans. They find that the recently described T memory stem cells are able to persist and preserve their precursor potential in human recipients for up to 12 years after genetic correction and infusion into patients. The safety and long-term survival of these cells not only strengthen our knowledge of human immunology but are also encouraging for adoptive immunotherapy.

    Sci. Transl. Med. 7, 273ra13 (2015).

  6. Addiction Therapy

    Reversing cocaine-evoked behavior in mice

    1. Peter Stern

    Therapeutic optogenetic protocols are highly effective at reversing symptoms in animal models of neuropsychiatric disease. However, translating these protocols into the clinic is challenging because we have not yet made the technical leap required to perform effective optogenetic stimulation in primates. Creed et al. tested whether it would be possible to circumvent these challenges by avoiding the problem altogether. They adjusted an existing therapeutic approach—deep brain stimulation—to mimic an effective optogenetic stimulation protocol to treat a mouse model of cocaine addiction.

    Science, this issue p. 659

  7. Plant Development

    Genetic control of stem cell fate in plant roots

    1. Pamela J. Hines

    Arabidopsis embryo seedling

    PHOTO: BRIAN CRAWFORD/UCSD

    Without roots, most plants cannot thrive. Crawford et al. have now unearthed the robust control systems that build roots. Signaling by the plant hormone auxin triggers three genes that control the development of stem cells forming the root. With this trio of genes, any one of which can do the job, root development is backed up with fail-safe controls. The team could use the same system of controls to sprout roots in the wrong places, making roots instead of shoots.

    Science, this issue p. 655

  8. Hot Response

    Bacterial infection breaks the lymph node barrier

    1. Kristen L. Mueller

    During infections, lymph nodes are command central. Fragments from invading pathogens enter lymph nodes through the lymph. There, specialized cells called subcapsular sinus (SCS) macrophages capture these antigens and use them to initiate humoral immunity. Despite being such important players, Gaya et al. report that in mice, infection throws these organized sentinels into disarray (see the Perspective by Buzsaki). Disrupting SCS macrophages had important consequences: Bacterially infected mice could not respond as efficiently to a subsequent viral infection.

    Science, this issue p. 667; see also p. 612

  9. Cancer

    Targeting Wnt signaling in lymphoma

    1. Wei Wong

    Although several human cancers show increased activity of the Wnt/β-catenin signaling pathway, tumors may lack mutations that would account for the increase. Walker et al. found that the transcription factor FOXP1 enhanced the transcription of Wnt-regulated target genes by binding to and promoting the acetylation of β-catenin. Patients with diffuse large B cell lymphomas over-expressing FOXP1 have a poor prognosis, and diffuse large B cell lymphoma cells with high FOXP1 levels were sensitive to Wnt inhibitors. Xenografted tumors in mice were smaller when they lacked FOXP1 or when Wnt signaling was blocked.

    Sci. Signal. 8, ra12 (2015).

  10. Education

    Assessing the value of undergraduate research

    1. Pamela J. Hines

    Undergraduate research experiences often engender enthusiasm in the students involved, but how useful are they in terms of enhancing student learning? Linn et al. review studies that focus on the effectiveness of undergraduate research programs. Undergraduate research experiences in a class were distinguished from those involving individualized participation in a research program. Mentoring emerges as both an important component of a successful experience and a target for improvement.

    Science, this issue 10.1126/science.1261757

  11. Infectious Disease

    Where will H5 flu viruses travel to next?

    1. Julia Fahrenkamp-Uppenbrink

    Avian influenza viruses can cause severe illness and even death in domestic poultry. In the past two decades, a particular group of viruses termed H5 viruses have caused repeated outbreaks after first emerging in China. In a Perspective, Verhagen et al. trace the recent spread of these viruses, particularly the H5N8 virus that was detected in North America in December 2014. Based on the pattern of spread, the authors argue that the virus may be spread by wild birds as they migrate via Russia to Europe, America, and beyond. The viruses currently constitute a low health threat for humans, but given the unpredictable nature of influenza viruses, they should be monitored closely.

    Science, this issue p. 616

  12. DNA Nanotechnology

    DNA control of bonding interactions

    1. Marc S. Lavine

    Colloidal particles have been used as atom mimics and are often connected together using complementary DNA strands. Rogers and Manoharan controlled the strength of the colloidal “bond” by using a set of competing strand displacement reactions. They capitalized on the reversible chemical equilibrium between the DNA strands connecting different particles to control the temperature dependence of the equilibrium state.

    Science, this issue p. 639

  13. Expression Profiling

    Single-cell expression analysis on a large scale

    1. Valda Vinson

    To understand why cells differ from each other, we need to understand which genes are transcribed at a single-cell level. Several methods measure messenger RNA (mRNA) expression in single cells, but most are limited to relatively low numbers of cells or genes. Fan et al. labeled each mRNA molecule in a cell with both a cellular barcode and a molecular barcode. Further analysis did not then require single-cell technologies. Instead, the labeled mRNA from all cells was pooled, amplified, and sequenced, and the gene expression profile of individual cells was reconstructed based on the barcodes. The technique successfully revealed heterogeneity across several thousand blood cells.

    Science, this issue 10.1126/science.1258367

  14. Metallurgy

    Screw dislocations: A hard case to crack

    1. Marc S. Lavine

    The motion of dislocations or defects in a metal influences its strength and toughness. If these defects can be “pinned” by adding alloying elements, it should be possible to create a stronger alloy. It was thought that there shouldn't be much of an interaction between screw dislocations and any alloying elements. However, Yu et al. show that for α-Ti, the profound hardening effect of oxygen is due to the strong interactions with the core of the dislocations. First-principles calculations reveal that distortion of the interstitial sites at the dislocation core creates a very strong but short-range repulsion for oxygen atoms.

    Science, this issue p. 635

  15. Carbon Radicals

    Catching a glimpse of the elusive QOOH

    1. Jake Yeston

    It's straightforward to write down the net combustion reaction: Oxygen reacts with hydrocarbons to form water and carbon dioxide. The details of how all the bonds break and form in succession are a great deal more complicated. Savee et al. now report direct detection of a long-postulated piece of the puzzle, a so-called QOOH intermediate. This structure results from bound oxygen stripping a hydrogen atom from carbon, leaving a carbon-centered radical behind. The study explores the influence of the hydrocarbon's unsaturation on the stability of QOOH, which has implications for both combustion and tropospheric oxidation chemistry.

    Science, this issue p. 643

  16. Protein Evolution

    Exploring the limits of protein sequence space

    1. Guy Riddihough

    Exploring the variability of individual functional proteins is complicated by the vast number of combinations of possible amino acid sequences. Podgornaia and Laub take on this challenge by analyzing four amino acids critical for the interaction between two signaling proteins in Escherichia coli. They build all the possible 160,000 variants of one of the two proteins and find that over 1650 are functional. Even though there can be very high variability in the composition of the interface between the two proteins, there are nonetheless strong context-dependent constraints for some amino acids, which suggests why many functional variants are not seen in nature.

    Science, this issue p. 673

  17. Genomic Variation

    How genetics affect phenotypic variation

    1. Laura L. Zahn

    How an individual looks depends on their genes, genetic variation, and interactions with the environment. However, the path from genotype to phenotype remains murky. Battle et al. examine how an individual's genetic variation affects expression of RNA, ribosome occupancy, and protein levels. They find that RNA expression and ribosome occupancy are generally correlated. However, in contrast, protein levels appear not to depend on RNA levels or ribosome occupancy. Protein levels are thus regulated by posttranscriptional mechanisms.

    Science, this issue p. 664