Editors' Choice

Science  26 Aug 2016:
Vol. 353, Issue 6302, pp. 883
  1. Development

    Microtubule sliding during Drosophila development

    1. Valda Vinson

    Kinesin-driven microtubule sliding contributes to cytoplasmic streaming in the Drosophila oocyte.

    PHOTO: WEN LU, JOSHUA Z. RAPPOPORT AND VLADIMIR I. GELFAND (NORTHWESTERN UNIVERSITY)

    The motor protein kinesin carries cargo to locations in the cell by moving along microtubules. Kinesin-1 can also move microtubules relative to each other. Winding et al. show that it does this by using its motor domain to move along one microtubule while using a second domain to bind another microtubule. They constructed a kinesin-1 mutant that was deficient in microtubule binding but able to bind and transport other cargo and a second mutant that was able to slide microtubules but could not transport cargo. Using these mutants, they demonstrated that microtubule sliding is important in axon and dendrite outgrowth during nervous system development. In addition, Lu et al. used the mutants to show that microtubule sliding contributes to cytoplasmic streaming, which is important in distributing RNA and proteins in Drosophila oocytes.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1520244113 and 10.1073/pnas.1522424113 (2016).

  2. Optics

    An integrated route to frequency combs

    1. Ian S. Osborne

    A frequency comb is a light source that provides a spectrum of precisely spaced wavelengths, the range of which can sometimes span over an octave. Such a light source can find a broad range of applications in spectroscopy, sensing, metrology, and communication. There are considerable efforts under way to generate such combs “on chip” by using microresonator cavities, thus providing the possibility of an integrated optics approach whereby the technology can be shrunk. Pu et al. report one such approach based on an AlGaAs-on-insulator platform. With the AlGaAs platform well developed in terms of processing and the material's optical properties well understood, the demonstration of such an approach could prove useful for the widespread commercialization of frequency comb technology.

    Optica 3, 823 (2016).

  3. Paleoecology

    Climate change and megafaunal extinction

    1. Andrew M. Sugden

    Wooly mammoths survived on St. Paul Island in the Bering Sea for thousands of years after other populations went extinct.

    CREDIT: FUNKMONK/WIKICOMMONS

    Woolly mammoths went extinct on the Asian and North American mainlands at the end of the last glaciation 13 to 14 thousand years ago. However, small relict populations are known to have survived for several thousand more years on the Beringian islands between the two continents. Graham et al. used a suite of paleoenvironmental proxy data to determine that the final extinction of mammoths on St. Paul Island occurred 5600 ± 100 years ago. There is no evidence of human occupation on St. Paul at that time, so hunting can be ruled out as a cause of the mammoths' disappearance from the island. Instead, their demise was caused by climate change and rising sea level acting synergistically to deplete freshwater resources.

    Proc. Natl. Acad. Sci. USA 10.1073/pnas.1604903113 (2016).

  4. Psychology

    Slow-motion state of mind

    1. Guy Riddihough

    Memory is fallible and therefore a potentially unreliable source of information in a court of law. Much better would be video evidence of a crime. Caruso et al. show that this is not always so, however. Watching surveillance video of a shooting during an attempted robbery in slow-motion replay gave viewers a stronger impression that the shooter fired with the intent to kill, compared with watching it at regular-speed playback. This effect on perception of premeditation was reduced, though not eliminated, by viewing the video at both regular and slow-motion speed, but it was not mitigated simply by indicating elapsed time.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1603865113 (2016).

    Watching surveillance video in slow motion increases perception of an intent to kill.

    CREDIT: HARRIS COUNTY SHERRIF'S OFFICE VIA HOUSTON CHRONICLE/ ASSOCIATED PRESS
  5. Piezoelectrics

    Making vibration sensors noble

    1. Brent Grocholski

    Piezoelectric materials produce an electrical current in response to mechanical stress, making them exceptional vibration sensors and actuators. Piezoelectric materials tend to be oxides, the most common example being quartz (SiO2). Stenner et al. show that the nanoporous gold impregnated with electrolyte solution produces an exceptionally large electrical charge in response to stress. The electrical response to strain comes from the charge polarization of internal interfaces. The distinct mechanism for generating a charge from traditional piezoelectrics suggests that other nanoporous metals may also be useful for electromechanical coupling applications.

    Adv. Funct. Mater. 10.1002/adfm.201600938 (2016).

  6. Materials Chemistry

    A framework for drug delivery

    1. Phil Szuromi

    Metal-organic frameworks (MOFs) are attractive candidates for drug delivery if they can be formed from low-toxicity materials. Levine et al. noted that olsalazine, a low-toxicity anti-inflammatory drug used in treatment of gastrointestinal diseases, is tolerated in multigram doses and structurally related to the ligands used to create M-MOF-74. One-dimensional hexagonal pore structures with diameters of 2.7 nm were formed from olsalazine and dications such as Mg2+ or Fe2+. These materials not only displayed a high capacity for H2 adsorption, but they could also be loaded with model drugs such as phenethylamine. Pressed pellets of the Mg-based material released 50% of the olsalazine and 95% of the phenethylamine after 3 hours in phosphate-buffered saline, suggesting applications for multidrug delivery.

    J. Am. Chem. Soc. 10.1021/jacs.6b03523 (2016).

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