Mihaela Balu, Amaan Mazhar, Carole K. Hayakawa, Richa Mittal, Tatiana B. Krasieva, Karsten König, Vasan Venugopalan, Bruce J. Tromberg. We employ a clinical multiphoton microscope to monitor in vivo and noninvasively the changes in reduced nicotinamide adenine dinucleotide (NADH) fluorescence of human epidermal cells during arteri....

Richard A. Gray, David N. Mashburn, Veniamin Y. Sidorov, John P. Wikswo. The measurement, quantitative analysis, theory, and mathematical modeling of transmembrane potential and currents have been an integral part of the field of electrophysiology since its inception. ....

Functional and evolutionary insight from the crystal structure of rubella virus protein E1

Nature 493, 7433 (2013). doi:10.1038/nature11741

Authors: Rebecca M. DuBois, Marie-Christine Vaney, M. Alejandra Tortorici, Rana Al Kurdi, Giovanna Barba-Spaeth, Thomas Krey & Félix A. Rey

Little is known about the three-dimensional organization of rubella virus, which causes a relatively mild measles-like disease in children but leads to serious congenital health problems when contracted in utero. Although rubella virus belongs to the same family as the mosquito-borne alphaviruses, in many respects it is more similar to other aerosol-transmitted human viruses such as the agents of measles and mumps. Although the use of the triple MMR (measles, mumps and rubella) live vaccine has limited its incidence in western countries, congenital rubella syndrome remains an important health problem in the developing world. Here we report the 1.8 Å resolution crystal structure of envelope glycoprotein E1, the main antigen and sole target of neutralizing antibodies against rubella virus. E1 is the main player during entry into target cells owing to its receptor-binding and membrane-fusion functions. The structure reveals the epitope and the neutralization mechanism of an important category of protecting antibodies against rubella infection. It also shows that rubella virus E1 is a class II fusion protein, which had hitherto only been structurally characterized for the arthropod-borne alphaviruses and flaviviruses. In addition, rubella virus E1 has an extensive membrane-fusion surface that includes a metal site, reminiscent of the T-cell immunoglobulin and mucin family of cellular proteins that bind phosphatidylserine lipids at the plasma membrane of cells undergoing apoptosis. Such features have not been seen in any fusion protein crystallized so far. Structural comparisons show that the class II fusion proteins from alphaviruses and flaviviruses, despite belonging to different virus families, are closer to each other than they are to rubella virus E1. This suggests that the constraints on arboviruses imposed by alternating cycles between vertebrates and arthropods resulted in more conservative evolution. By contrast, in the absence of this constraint, the strictly human rubella virus seems to have drifted considerably into a unique niche as sole member of the Rubivirus genus.

Planetary system disruption by Galactic perturbations to wide binary stars

Nature 493, 7432 (2013). doi:10.1038/nature11780

Authors: Nathan A. Kaib, Sean N. Raymond & Martin Duncan

Nearly half the exoplanets found within binary star systems reside in very wide binaries with average stellar separations greater than 1,000 astronomical units (one astronomical unit (au) being the Earth–Sun distance), yet the influence of such distant binary companions on planetary evolution remains largely unstudied. Unlike their tighter counterparts, the stellar orbits of wide binaries continually change under the influence of the Milky Way’s tidal field and impulses from other passing stars. Here we report numerical simulations demonstrating that the variable nature of wide binary star orbits dramatically reshapes the planetary systems they host, typically billions of years after formation. Contrary to previous understanding, wide binary companions may often strongly perturb planetary systems, triggering planetary ejections and increasing the orbital eccentricities of surviving planets. Although hitherto not recognized, orbits of giant exoplanets within wide binaries are statistically more eccentric than those around isolated stars. Both eccentricity distributions are well reproduced when we assume that isolated stars and wide binaries host similar planetary systems whose outermost giant planets are scattered beyond about 10 au from their parent stars by early internal instabilities. Consequently, our results suggest that although wide binaries eventually remove the most distant planets from many planetary systems, most isolated giant exoplanet systems harbour additional distant, still undetected planets.