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New for March 1
Applied Physical Sciences
Classical geometries unfurl from multicomponent shells
Cell Biology
How cancer cells taint normal cells
Chemistry
Carbonaceous meteorite releases ammonia,precursor for life
Medical Sciences
Placental immune protein helps fight vaginal infection
Microbiology
Hybrid influenza viruses may have pandemic potential
Recent Highlights
Applied Biological Sciences, Chemistry
Nanopillars illuminate cells’ interior
Applied Physical Sciences
Living glass
Cell Biology
Glioblastoma cells form their own vascular cells
Chemistry, Biophysics and Computational Biology
A clue to plants’ efficient solar power
Developmental Biology
Paternal immune molecules can spur fetal development
Evolution
Draft genomes of three ant species
Medical Sciences
Wounding may induce stem cells to trigger cancer
Microbiology
Combinatorial labeling illuminates microbial communities
Neuroscience
Brain region may reinforce moderate drinking
A computer model of nanopillar illumination.
"Vertical nanopillars for highly localized
fluorescence imaging"
by Chong Xie, Lindsey Hanson, Yi Cui, and
Bianxiao Cui
The light source used for fluorescent microscopy is
the sample itself, which fluoresces with visible light in response to electromagnetic excitation. Neighboring molecules can blur the target signal, so
high-resolution imaging requires the observation of a
very small volume. Chong Xie et al. propose an alternative to existing imaging techniques, which rely on highly confined standing light waves called evanescent waves to limit the illumination volume, but do not allow light to penetrate deep enough into cells to image the cell interior. The authors used arrays of vertical nanopillars—tiny posts of quartz that protrude from a layer of platinum metal like telephone posts rising from a sidewalk—to create points of light that can penetrate and illuminate cells for imaging in vitro and in vivo. The nanopillars rely on evanescent waves to restrict background noise, but light emitted vertically from the pillars decays more slowly, the authors report, allowing the light to pass through the plasma membrane into the cell’s interior. The researchers plated monkey and rat cells on the nanopillar arrays and observed that the cells survived and divided normally, and that live cells grew toward the nanopillars and engulfed them. Furthermore, the authors found that chemically modified nanopillars simultaneously recruited and illuminated targeted proteins inside live cells, which allowed the authors to observe complex cell behavior at high resolution. —
Applied Physical Sciences
Classical geometries unfurl from multicomponent shells |
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Viral capsids and other naturally occurring molecular shells spontaneously fold into regular geometric shapes, such as 20-sided icosahedra. Elastic theory governs the formation of shells formed from a single structural unit, such as a protomer in the case of capsids, but the formation of shells from multiple units is less understood. Graziano Vernizzi et al. explored the formation of multicomponent microscopic shells that buckle into various other multifaceted polyhedral shapes. The onset of faceting in icosahedra depends on the radius of the shell, its bending rigidity, and the material’s stiffness. Based on these parameters and standard simulations to determine the lowest-energy configurations, the authors formulated a generalized elastic model for inhomogeneous shells with two components. They discovered that both regular and irregular polyhedra, including some classical shapes such as dodecahedra, octahedra, and icosahedra, as well as their truncated forms, arose spontaneously in the inhomogeneous shells. The lowest-energy configuration leapt from one polyhedral form to the next, depending on the relative fraction of the two components. This work, the researchers say, predicts a family of polyhedral shells previously unseen in naturally occurring systems and may help researchers design nano- or microcontainers with specific shapes and symmetries. — F.A.
Cellular shells (Left) resembling inhomogeneous coassembled polyhedra shells (Right).
"Platonic and Archimedean geometries in multicomponent elastic membranes"
by Graziano Vernizzi, Rastko Sknepnek, and Monica Olvera de la Cruz
Applied Physical Sciences
Living glass
Glass-like migrating epithelial cell layer.
"Glass-like dynamics of collective
cell migration"
by Thomas E. Angelini, et al.
[Abstract] OPEN ACCESS ARTICLE
The movement of cells en masse plays crucial roles in wound healing, embryonic development, and cancer metastasis. As increasingly dense cells in a layer reach confluence, the cell sheet begins to flow like a fluid; yet, the movement of single cells is constrained by neighboring cells. Thomas Angelini et al. are among the few researchers who have analyzed how the movement of single cells contributes to the collective movement of cell sheets. The authors fashioned a laboratory mock-up of biological tissue from a polyacrylamide gel containing collagen. The authors then grew a confluent sheet of canine kidney cells on the gel and studied a range of physical properties related to the movements of single cells and of the sheet. Collective cell movement, the authors report, is reminiscent of the dynamic process by which supercooled liquids and colloids transform into a glass-like state. Below a threshold cell density, confluent cells flow like a fluid; above the threshold, the cell sheet behaves like glass. In addition, changes in the dynamics of cell division and single cell deformation within the cell sheet also evoke the fluid-to-glass transition. The findings could help researchers better understand the dynamics of biological processes like wound healing where similar physical forces are at play, the authors suggest. — P.N.
Cell Biology
How cancer cells taint normal cells |
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Cancer cells often ferry cancer-related signaling proteins from cell to cell by packaging them into transport vesicles called oncosomes, thus contributing to cancer progression. Until recently, the question of whether healthy cells near a tumor can become cancerous upon exposure to these vesicles has remained unexplored. Marc Antonyak et al. isolated oncosomes shed by aggressive breast cancer and brain tumor cells and added them to normal mouse fibroblast cells cultured in laboratory dishes. The oncosomes boosted the ability of the normal cells to grow in a culture medium containing sparse nutrients, enhancing the cells’ survival and inducing oncogenic transformation. Strikingly, when breast cancer cells treated with a growth-blocking chemical were injected with normal mouse fibroblasts into mice, a majority of the mice developed tumors. In contrast, control mice injected with the growth-arrested breast cancer cells alone failed to form tumors, suggesting that oncosomes from cancer cells can endow normal fibroblasts with cancer-causing potential. By performing proteomic analysis on the oncosomes, the authors found that an enzyme called transglutaminase and an extracellular matrix protein called fibronectin are crucial to the oncosomes’ cancer-causing ability. The authors suggest that the growth of a tumor might depend not only on the proliferation of cancer cells but also on the exposure of healthy cells in the tumor’s surroundings to oncosomes. — P.N.
Oncosomes on a cancer cell.
"Cancer cell-derived microvesicles induce transformation by transferring tissue transglutaminase and fibronectin
to recipient cells"
by Marc A. Antonyak, et al.
Chemistry
Carbonaceous meteorite releases ammonia, precursor for life |
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Previous studies have proposed that extraterrestrial bodies such as comets or meteorites may have seeded the Earth with the elements that all organisms share. Researchers have identified diverse
organic materials within carbonaceous chondrites (CC)—primitive asteroid fragments that may carry
a pristine record of the early solar system—but the origin of the nitrogen used to create Earth’s first biomolecules remains unclear. Sandra Pizzarello et al. determined the molecular composition of insoluble carbonaceous material within an Antarctic CC known as the GRA 95229 meteorite by treating material from the meteorite with water at high temperature and pressure, conditions that the researchers suggest may mimic the environment of early Earth. The researchers analyzed the resulting compounds in a mass spectrometer and found that the treated powders emitted ammonia, an important component of complex biological molecules, such as amino acids and DNA, into the surrounding water. Additional analysis of the nitrogen atoms within the emitted ammonia indicated that the atomic isotope did not match those currently found on Earth. The authors suggest that abundant ammonia emissions from meteorites such as GRA 95229 may have aided Earth's molecular evolution and the beginning of life. — J.M.
 | Scientists attempt to recover meteorites from glaciers in Antarctica. Image courtesy of Linda Welzenbach (Smithsonian Institution, Washington); Antarctic Search for Meteorites Program, Case Western Reserve University, NASA, NSF, and the Smithsonian Institution.
"Abundant ammonia in primitive asteroids and the case for a possible exobiology"
by Sandra Pizzarello, Lynda B. Williams, Jennifer Lehman, Gregory P. Holland, and Jeffery L. Yarger
Chemistry, Biophysics and Computational Biology
A clue to plants’ efficient solar power
Chlorophyll binding sites (red, blue) in the CP29 light harvesting complex.
"Solving structure in the CP29 light harvesting complex with polarization-phased 2D electronic spectroscopy"
by Naomi S. Ginsberg, et al.
An artificial photosynthesis device that mimics green plants could theoretically provide a renewable source of electrical energy and help to scrub carbon dioxide from the air. But because photosynthetic reactions unfold quickly and the molecules are difficult to image, significant gaps remain in researchers’ understanding of the process. Naomi Ginsberg et al. studied the CP29 light harvesting complex, a combination of chlorophyll pigments and proteins that allows plants to collect, conduct, and quench electronic energy. Using 2D electronic spectroscopy, the authors determined the relative angles between separated electric charges in CP29 pigments. The authors then probed the CP29 complex with ultra-fast light pulses under three different polarization conditions, and measured how the complex absorbed and re-emitted the energy. By combining individual spectra, the authors disentangled closely-spaced absorption energies and identified the electronic dynamics that shaped the signals. Unlike previous measurements, the authors report that the results reveal the structural details of a highly complex system without the need for theoretical modeling or crystallography. The results could provide the basis for additional studies on CP29, and the technique could be used to address outstanding questions about structure-function relationships in other electronically-coupled systems, according to the authors. — J.M.
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