Comment on "The [4Fe4S] cluster of human DNA primase functions as a redox switch using DNA charge transport"
O’Brien et al. (Research Article, 24 February 2017, eaag1789) report that the iron-sulfur cluster of primase has a redox role in enzyme activity. Their analysis is based on a partially misfolded structure of the iron-sulfur cluster domain of primase. In the correctly folded structure, two of the three tyrosines putatively involved in electron transfer, Y345 and Y347, contact the RNA/DNA helix, providing an alternative explanation for the data of O’Brien et al. (Source: ScienceNOW)
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Pellegrini, L. Tags: Biochemistry, Online Only t-comment Source Type: news
Response to Comments on "The [4Fe4S] cluster of human DNA primase functions as a redox switch using DNA charge transport"
Baranovskiy et al. and Pellegrini argue that, based on structural data, the path for charge transfer through the [4Fe4S] domain of primase is not feasible. Our manuscript presents electrochemical data directly showing charge transport through DNA to the [4Fe4S] cluster of a primase p58C construct and a reversible switch in the DNA-bound signal with oxidation/reduction, which is inhibited by mutation of three tyrosine residues. Although the dispositions of tyrosines differ in different constructs, all are within range for microsecond electron transfer. (Source: ScienceNOW)
Source: ScienceNOW - July 20, 2017 Category: Science Authors: OBrien, E., Holt, M. E., Thompson, M. K., Salay, L. E., Ehlinger, A. C., Chazin, W. J., Barton, J. K. Tags: Biochemistry, Online Only t-comment Source Type: news
Comment on "The [4Fe4S] cluster of human DNA primase functions as a redox switch using DNA charge transport"
O’Brien et al. (Research Article, 24 February 2017, eaag1789) proposed a novel mechanism of primase function based on redox activity of the iron-sulfur cluster buried inside the C-terminal domain of the large primase subunit (p58C). Serious problems in the experimental design and data interpretation raise concerns about the validity of the conclusions. (Source: ScienceNOW)
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Baranovskiy, A. G., Babayeva, N. D., Zhang, Y., Blanco, L., Pavlov, Y. I., Tahirov, T. H. Tags: Biochemistry, Online Only t-comment Source Type: news
Epigenetic plasticity and the hallmarks of cancer
Chromatin and associated epigenetic mechanisms stabilize gene expression and cellular states while also facilitating appropriate responses to developmental or environmental cues. Genetic, environmental, or metabolic insults can induce overly restrictive or overly permissive epigenetic landscapes that contribute to pathogenesis of cancer and other diseases. Restrictive chromatin states may prevent appropriate induction of tumor suppressor programs or block differentiation. By contrast, permissive or "plastic" states may allow stochastic oncogene activation or nonphysiologic cell fate transitions. Whereas many stoc...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Flavahan, W. A., Gaskell, E., Bernstein, B. E. Tags: Medicine, Diseases, Online Only review Source Type: news
Bidirectional eukaryotic DNA replication is established by quasi-symmetrical helicase loading
Bidirectional replication from eukaryotic DNA replication origins requires the loading of two ring-shaped minichromosome maintenance (MCM) helicases around DNA in opposite orientations. MCM loading is orchestrated by binding of the origin recognition complex (ORC) to DNA, but how ORC coordinates symmetrical MCM loading is unclear. We used natural budding yeast DNA replication origins and synthetic DNA sequences to show that efficient MCM loading requires binding of two ORC molecules to two ORC binding sites. The relative orientation of these sites, but not the distance between them, was found to be critical for MCM loading...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Coster, G., Diffley, J. F. X. Tags: Biochemistry, Molecular Biology reports Source Type: news
Hydraulic control of tuna fins: A role for the lymphatic system in vertebrate locomotion
The lymphatic system in teleost fish has genetic and developmental origins similar to those of the mammalian lymphatic system, which is involved in immune response and fluid homeostasis. Here, we show that the lymphatic system of tunas functions in swimming hydrodynamics. Specifically, a musculo-vascular complex, consisting of fin muscles, bones, and lymphatic vessels, is involved in the hydraulic control of median fins. This specialization of the lymphatic system is associated with fish in the family Scombridae and may have evolved in response to the demand for swimming and maneuvering control in these high-performance sp...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Pavlov, V., Rosental, B., Hansen, N. F., Beers, J. M., Parish, G., Rowbotham, I., Block, B. A. Tags: Physiology reports Source Type: news
An organic-inorganic perovskite ferroelectric with large piezoelectric response
Molecular piezoelectrics are highly desirable for their easy and environment-friendly processing, light weight, low processing temperature, and mechanical flexibility. However, although 136 years have passed since the discovery in 1880 of the piezoelectric effect, molecular piezoelectrics with a piezoelectric coefficient d33 comparable with piezoceramics such as barium titanate (BTO; ~190 picocoulombs per newton) have not been found. We show that trimethylchloromethyl ammonium trichloromanganese(II), an organic-inorganic perovskite ferroelectric crystal processed from aqueous solution, has a large d33 of 185 picocoulombs p...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: You, Y.-M., Liao, W.-Q., Zhao, D., Ye, H.-Y., Zhang, Y., Zhou, Q., Niu, X., Wang, J., Li, P.-F., Fu, D.-W., Wang, Z., Gao, S., Yang, K., Liu, J.-M., Li, J., Yan, Y., Xiong, R.-G. Tags: Physics, Applied reports Source Type: news
Tailored semiconductors for high-harmonic optoelectronics
The advent of high-harmonic generation in gases 30 years ago set the foundation for attosecond science and facilitated ultrafast spectroscopy in atoms, molecules, and solids. We explore high-harmonic generation in the solid state by means of nanostructured and ion-implanted semiconductors. We use wavelength-selective microscopic imaging to map enhanced harmonic emission and show that the generation medium and the driving field can be locally tailored in solids by modifying the chemical composition and morphology. This enables the control of high-harmonic technology within precisely engineered solid targets. We demonstrate ...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Sivis, M., Taucer, M., Vampa, G., Johnston, K., Staudte, A., Naumov, A. Y., Villeneuve, D. M., Ropers, C., Corkum, P. B. Tags: Physics reports Source Type: news
Experimentally realized mechanochemistry distinct from force-accelerated scission of loaded bonds
We report here unambiguous experimental validation of this hypothesis: Detailed kinetic measurements demonstrate that stretching phosphotriesters accelerates dissociation of the unloaded phosphorus-oxygen bond orthogonal to the pulling axis, whereas stretching organosiloxanes inhibits dissociation of the aligned loaded silicon-oxygen bonds. Qualitatively, the outcome is determined by phosphoester elongation and siloxane contraction along the pulling axis in the respective rate-determining transition states. Quantitatively, the results agree with a simple mechanochemical kinetics model. (Source: ScienceNOW)
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Akbulatov, S., Tian, Y., Huang, Z., Kucharski, T. J., Yang, Q.-Z., Boulatov, R. Tags: Chemistry reports Source Type: news
Chiral Majorana fermion modes in a quantum anomalous Hall insulator-superconductor structure
We report transport measurements that suggest the existence of one-dimensional chiral Majorana fermion modes in the hybrid system of a quantum anomalous Hall insulator thin film coupled with a superconductor. As the external magnetic field is swept, half-integer quantized conductance plateaus are observed at the locations of magnetization reversals, giving a distinct signature of the Majorana fermion modes. This transport signature is reproducible over many magnetic field sweeps and appears at different temperatures. This finding may open up an avenue to control Majorana fermions for implementing robust topological quantum...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: He, Q. L., Pan, L., Stern, A. L., Burks, E. C., Che, X., Yin, G., Wang, J., Lian, B., Zhou, Q., Choi, E. S., Murata, K., Kou, X., Chen, Z., Nie, T., Shao, Q., Fan, Y., Zhang, S.-C., Liu, K., Xia, J., Wang, K. L. Tags: Physics reports Source Type: news
Remobilization of crustal carbon may dominate volcanic arc emissions
The flux of carbon into and out of Earth’s surface environment has implications for Earth’s climate and habitability. We compiled a global data set for carbon and helium isotopes from volcanic arcs and demonstrated that the carbon isotope composition of mean global volcanic gas is considerably heavier, at –3.8 to –4.6 per mil (), than the canonical mid-ocean ridge basalt value of –6.0. The largest volcanic emitters outgas carbon with higher 13C and are located in mature continental arcs that have accreted carbonate platforms, indicating that reworking of crustal limestone is an important sourc...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Mason, E., Edmonds, M., Turchyn, A. V. Tags: Geochemistry, Geophysics reports Source Type: news
Bismuthene on a SiC substrate: A candidate for a high-temperature quantum spin Hall material
Quantum spin Hall materials hold the promise of revolutionary devices with dissipationless spin currents but have required cryogenic temperatures owing to small energy gaps. Here we show theoretically that a room-temperature regime with a large energy gap may be achievable within a paradigm that exploits the atomic spin-orbit coupling. The concept is based on a substrate-supported monolayer of a high–atomic number element and is experimentally realized as a bismuth honeycomb lattice on top of the insulating silicon carbide substrate SiC(0001). Using scanning tunneling spectroscopy, we detect a gap of ~0.8 electron vo...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Reis, F., Li, G., Dudy, L., Bauernfeind, M., Glass, S., Hanke, W., Thomale, R., Schäfer, J., Claessen, R. Tags: Materials Science reports Source Type: news
Photoinduced decarboxylative borylation of carboxylic acids
The conversion of widely available carboxylic acids into versatile boronic esters would be highly enabling for synthesis. We found that this transformation can be effected by illuminating the N-hydroxyphthalimide ester derivative of the carboxylic acid under visible light at room temperature in the presence of the diboron reagent bis(catecholato)diboron. A simple workup allows isolation of the pinacol boronic ester. Experimental evidence suggests that boryl radical intermediates are involved in the process. The methodology is illustrated by the transformation of primary, secondary, and tertiary alkyl carboxylic acids as we...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Fawcett, A., Pradeilles, J., Wang, Y., Mutsuga, T., Myers, E. L., Aggarwal, V. K. Tags: Chemistry reports Source Type: news
Highly elastic binders integrating polyrotaxanes for silicon microparticle anodes in lithium ion batteries
Lithium-ion batteries with ever-increasing energy densities are needed for batteries for advanced devices and all-electric vehicles. Silicon has been highlighted as a promising anode material because of its superior specific capacity. During repeated charge-discharge cycles, silicon undergoes huge volume changes. This limits cycle life via particle pulverization and an unstable electrode-electrolyte interface, especially when the particle sizes are in the micrometer range. We show that the incorporation of 5 weight % polyrotaxane to conventional polyacrylic acid binder imparts extraordinary elasticity to the polymer networ...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Choi, S., Kwon, T.-w., Coskun, A., Choi, J. W. Tags: Chemistry reports Source Type: news
Ratchet-like polypeptide translocation mechanism of the AAA+ disaggregase Hsp104
Hsp100 polypeptide translocases are conserved members of the AAA+ family (adenosine triphosphatases associated with diverse cellular activities) that maintain proteostasis by unfolding aberrant and toxic proteins for refolding or proteolytic degradation. The Hsp104 disaggregase from Saccharomyces cerevisiae solubilizes stress-induced amorphous aggregates and amyloids. The structural basis for substrate recognition and translocation is unknown. Using a model substrate (casein), we report cryo–electron microscopy structures at near-atomic resolution of Hsp104 in different translocation states. Substrate interactions ar...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Gates, S. N., Yokom, A. L., Lin, J., Jackrel, M. E., Rizo, A. N., Kendsersky, N. M., Buell, C. E., Sweeny, E. A., Mack, K. L., Chuang, E., Torrente, M. P., Su, M., Shorter, J., Southworth, D. R. Tags: Biochemistry r-articles Source Type: news
Cash for carbon: A randomized trial of payments for ecosystem services to reduce deforestation
We evaluated a program of payments for ecosystem services in Uganda that offered forest-owning households annual payments of 70,000 Ugandan shillings per hectare if they conserved their forest. The program was implemented as a randomized controlled trial in 121 villages, 60 of which received the program for 2 years. The primary outcome was the change in land area covered by trees, measured by classifying high-resolution satellite imagery. We found that tree cover declined by 4.2% during the study period in treatment villages, compared to 9.1% in control villages. We found no evidence that enrollees shifted their deforestat...
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Jayachandran, S., de Laat, J., Lambin, E. F., Stanton, C. Y., Audy, R., Thomas, N. E. Tags: Ecology, Economics r-articles Source Type: news
Fringe on the brink: Intertidal reefs at risk
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Andrades, R., Joyeux, J.-C., Gasparini, J. L., Reis-Filho, J. A., Macieira, R. M., Giarrizzo, T. Tags: letters Source Type: news
Promote scientific integrity via journal peer review data
Source: ScienceNOW - July 20, 2017 Category: Science Authors: Lee, C. J., Moher, D. Tags: Science and Policy p-forum Source Type: news