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Proceedings of the National Academy of Sciences of the United States of America

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https://www.readbyqxmd.com/read/28642348/confined-in-fiber-solidification-and-structural-control-of-silicon-and-silicon-germanium-microparticles
#1
Alexander Gumennik, Etgar C Levy, Benjamin Grena, Chong Hou, Michael Rein, Ayman F Abouraddy, John D Joannopoulos, Yoel Fink
Crystallization of microdroplets of molten alloys could, in principle, present a number of possible morphological outcomes, depending on the symmetry of the propagating solidification front and its velocity, such as axial or spherically symmetric species segregation. However, because of thermal or constitutional supercooling, resulting droplets often only display dendritic morphologies. Here we report on the crystallization of alloyed droplets of controlled micrometer dimensions comprising silicon and germanium, leading to a number of surprising outcomes...
June 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28642347/counteracting-dysfunction-of-regulatory-t-cells-in-organ-transplantation
#2
Cees van Kooten
No abstract text is available yet for this article.
June 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28642346/detergent-induced-self-assembly-and-controllable-photosensitizer-activity-of-diester-phenylene-ethynylenes
#3
Patrick L Donabedian, Matthew N Creyer, Florencia A Monge, Kirk S Schanze, Eva Y Chi, David G Whitten
Photodynamic therapy, in which malignant tissue is killed by targeted light exposure following administration of a photosensitizer, can be a valuable treatment modality but currently relies on passive transport and local irradiation to avoid off-target oxidation. We present a system of excited-state control for truly local delivery of singlet oxygen. An anionic phenylene ethynylene oligomer is initially quenched by water, producing minimal fluorescence and no measurable singlet oxygen generation. When presented with a binding partner, in this case an oppositely charged surfactant, changes in solvent microenvironment result in fluorescence unquenching, restoration of intersystem crossing to the triplet state, and singlet oxygen generation, as assayed by transient absorption spectroscopy and chemical trapping...
June 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28642345/evolution-of-nonspectral-rhodopsin-function-at-high-altitudes
#4
Gianni M Castiglione, Frances E Hauser, Brian S Liao, Nathan K Lujan, Alexander Van Nynatten, James M Morrow, Ryan K Schott, Nihar Bhattacharyya, Sarah Z Dungan, Belinda S W Chang
High-altitude environments present a range of biochemical and physiological challenges for organisms through decreases in oxygen, pressure, and temperature relative to lowland habitats. Protein-level adaptations to hypoxic high-altitude conditions have been identified in multiple terrestrial endotherms; however, comparable adaptations in aquatic ectotherms, such as fishes, have not been as extensively characterized. In enzyme proteins, cold adaptation is attained through functional trade-offs between stability and activity, often mediated by substitutions outside the active site...
June 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28637720/notch1-maintains-dormancy-of-olfactory-horizontal-basal-cells-a-reserve-neural-stem-cell
#5
Daniel B Herrick, Brian Lin, Jesse Peterson, Nikolai Schnittke, James E Schwob
The remarkable capacity of the adult olfactory epithelium (OE) to regenerate fully both neurosensory and nonneuronal cell types after severe epithelial injury depends on life-long persistence of two stem cell populations: the horizontal basal cells (HBCs), which are quiescent and held in reserve, and mitotically active globose basal cells. It has recently been demonstrated that down-regulation of the ΔN form of the transcription factor p63 is both necessary and sufficient to release HBCs from dormancy. However, the mechanisms by which p63 is down-regulated after acute OE injury remain unknown...
June 21, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634304/redox-dependent-interaction-between-thaumatin-like-protein-and-%C3%AE-glucan-influences-malting-quality-of-barley
#6
Surinder Singh, Rajiv K Tripathi, Peggy G Lemaux, Bob B Buchanan, Jaswinder Singh
Barley is the cornerstone of the malting and brewing industry. It is known that 250 quantitative trait loci (QTLs) of the grain are associated with 19 malting-quality phenotypes. However, only a few of the contributing genetic components have been identified. One of these, on chromosome 4H, contains a major malting QTL, QTL2, located near the telomeric region that accounts, respectively, for 28.9% and 37.6% of the variation in the β-glucan and extract fractions of malt. In the current study, we dissected the QTL2 region using an expression- and microsynteny-based approach...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634303/structural-characterization-of-the-rabphilin-3a-snap25-interaction
#7
Cristina Ferrer-Orta, María Dolores Pérez-Sánchez, Teresa Coronado-Parra, Cristina Silva, David López-Martínez, Jesús Baltanás-Copado, Juan Carmelo Gómez-Fernández, Senena Corbalán-García, Núria Verdaguer
Membrane fusion is essential in a myriad of eukaryotic cell biological processes, including the synaptic transmission. Rabphilin-3A is a membrane trafficking protein involved in the calcium-dependent regulation of secretory vesicle exocytosis in neurons and neuroendocrine cells, but the underlying mechanism remains poorly understood. Here, we report the crystal structures and biochemical analyses of Rabphilin-3A C2B-SNAP25 and C2B-phosphatidylinositol 4,5-bisphosphate (PIP2) complexes, revealing how Rabphilin-3A C2 domains operate in cooperation with PIP2/Ca(2+) and SNAP25 to bind the plasma membrane, adopting a conformation compatible to interact with the complete SNARE complex...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634302/structure-of-human-fe-s-assembly-subcomplex-reveals-unexpected-cysteine-desulfurase-architecture-and-acyl-acp-isd11-interactions
#8
Seth A Cory, Jonathan G Van Vranken, Edward J Brignole, Shachin Patra, Dennis R Winge, Catherine L Drennan, Jared Rutter, David P Barondeau
In eukaryotes, sulfur is mobilized for incorporation into multiple biosynthetic pathways by a cysteine desulfurase complex that consists of a catalytic subunit (NFS1), LYR protein (ISD11), and acyl carrier protein (ACP). This NFS1-ISD11-ACP (SDA) complex forms the core of the iron-sulfur (Fe-S) assembly complex and associates with assembly proteins ISCU2, frataxin (FXN), and ferredoxin to synthesize Fe-S clusters. Here we present crystallographic and electron microscopic structures of the SDA complex coupled to enzyme kinetic and cell-based studies to provide structure-function properties of a mitochondrial cysteine desulfurase...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634301/microbial-glycoside-hydrolases-as-antibiofilm-agents-with-cross-kingdom-activity
#9
Brendan D Snarr, Perrin Baker, Natalie C Bamford, Yukiko Sato, Hong Liu, Mélanie Lehoux, Fabrice N Gravelat, Hanna Ostapska, Shane R Baistrocchi, Robert P Cerone, Elan E Filler, Matthew R Parsek, Scott G Filler, P Lynne Howell, Donald C Sheppard
Galactosaminogalactan and Pel are cationic heteropolysaccharides produced by the opportunistic pathogens Aspergillus fumigatus and Pseudomonas aeruginosa, respectively. These exopolysaccharides both contain 1,4-linked N-acetyl-d-galactosamine and play an important role in biofilm formation by these organisms. Proteins containing glycoside hydrolase domains have recently been identified within the biosynthetic pathway of each exopolysaccharide. Recombinant hydrolase domains from these proteins (Sph3h from A...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634300/understanding-the-mechanical-response-of-double-stranded-dna-and-rna-under-constant-stretching-forces-using-all-atom-molecular-dynamics
#10
Alberto Marin-Gonzalez, J G Vilhena, Ruben Perez, Fernando Moreno-Herrero
Multiple biological processes involve the stretching of nucleic acids (NAs). Stretching forces induce local changes in the molecule structure, inhibiting or promoting the binding of proteins, which ultimately affects their functionality. Understanding how a force induces changes in the structure of NAs at the atomic level is a challenge. Here, we use all-atom, microsecond-long molecular dynamics to simulate the structure of dsDNA and dsRNA subjected to stretching forces up to 20 pN. We determine all of the elastic constants of dsDNA and dsRNA and provide an explanation for three striking differences in the mechanical response of these two molecules: the threefold softer stretching constant obtained for dsRNA, the opposite twist-stretch coupling, and its nontrivial force dependence...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634299/biosynthesis-of-isonitrile-lipopeptides-by-conserved-nonribosomal-peptide-synthetase-gene-clusters-in-actinobacteria
#11
Nicholas C Harris, Michio Sato, Nicolaus A Herman, Frederick Twigg, Wenlong Cai, Joyce Liu, Xuejun Zhu, Jordan Downey, Ryan Khalaf, Joelle Martin, Hiroyuki Koshino, Wenjun Zhang
A putative lipopeptide biosynthetic gene cluster is conserved in many species of Actinobacteria, including Mycobacterium tuberculosis and M. marinum, but the specific function of the encoding proteins has been elusive. Using both in vivo heterologous reconstitution and in vitro biochemical analyses, we have revealed that the five encoding biosynthetic enzymes are capable of synthesizing a family of isonitrile lipopeptides (INLPs) through a thio-template mechanism. The biosynthesis features the generation of isonitrile from a single precursor Gly promoted by a thioesterase and a nonheme iron(II)-dependent oxidase homolog and the acylation of both amino groups of Lys by the same isonitrile acyl chain facilitated by a single condensation domain of a nonribosomal peptide synthetase...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634298/analyses-of-pde-regulated-phosphoproteomes-reveal-unique-and-specific-camp-signaling-modules-in-t-cells
#12
Michael-Claude G Beltejar, Ho-Tak Lau, Martin G Golkowski, Shao-En Ong, Joseph A Beavo
Specific functions for different cyclic nucleotide phosphodiesterases (PDEs) have not yet been identified in most cell types. Conventional approaches to study PDE function typically rely on measurements of global cAMP, general increases in cAMP-dependent protein kinase (PKA), or the activity of exchange protein activated by cAMP (EPAC). Although newer approaches using subcellularly targeted FRET reporter sensors have helped define more compartmentalized regulation of cAMP, PKA, and EPAC, they have limited ability to link this regulation to downstream effector molecules and biological functions...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634297/superman-prevents-class-b-gene-expression-and-promotes-stem-cell-termination-in-the-fourth-whorl-of-arabidopsisthaliana-flowers
#13
Nathanaël Prunet, Weibing Yang, Pradeep Das, Elliot M Meyerowitz, Thomas P Jack
The molecular and genetic networks underlying the determination of floral organ identity are well studied, but much less is known about how the flower is partitioned into four developmentally distinct whorls. The SUPERMAN gene is required for proper specification of the boundary between stamens in whorl 3 and carpels in whorl 4, as superman mutants exhibit supernumerary stamens but usually lack carpels. However, it has remained unclear whether extra stamens in superman mutants originate from an organ identity change in whorl 4 or the overproliferation of whorl 3...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634296/1t-tas2-as-a-quantum-spin-liquid
#14
K T Law, Patrick A Lee
1T-TaS2 is unique among transition metal dichalcogenides in that it is understood to be a correlation-driven insulator, where the unpaired electron in a 13-site cluster experiences enough correlation to form a Mott insulator. We argue, based on existing data, that this well-known material should be considered as a quantum spin liquid, either a fully gapped [Formula: see text] spin liquid or a Dirac spin liquid. We discuss the exotic states that emerge upon doping and propose further experimental probes.
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634295/population-genomic-inference-of-the-strength-and-timing-of-selection-against-gene-flow
#15
Simon Aeschbacher, Jessica P Selby, John H Willis, Graham Coop
The interplay of divergent selection and gene flow is key to understanding how populations adapt to local environments and how new species form. Here, we use DNA polymorphism data and genome-wide variation in recombination rate to jointly infer the strength and timing of selection, as well as the baseline level of gene flow under various demographic scenarios. We model how divergent selection leads to a genome-wide negative correlation between recombination rate and genetic differentiation among populations...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634294/hidden-electrostatic-basis-of-dynamic-allostery-in-a-pdz-domain
#16
Amit Kumawat, Suman Chakrabarty
Allosteric effect implies ligand binding at one site leading to structural and/or dynamical changes at a distant site. PDZ domains are classic examples of dynamic allostery without conformational changes, where distal side-chain dynamics is modulated on ligand binding and the origin has been attributed to entropic effects. In this work, we unearth the energetic basis of the observed dynamic allostery in a PDZ3 domain protein using molecular dynamics simulations. We demonstrate that electrostatic interaction provides a highly sensitive yardstick to probe the allosteric modulation in contrast to the traditionally used structure-based parameters...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634293/intrinsic-map-dynamics-exploration-for-uncharted-effective-free-energy-landscapes
#17
Eliodoro Chiavazzo, Roberto Covino, Ronald R Coifman, C William Gear, Anastasia S Georgiou, Gerhard Hummer, Ioannis G Kevrekidis
We describe and implement a computer-assisted approach for accelerating the exploration of uncharted effective free-energy surfaces (FESs). More generally, the aim is the extraction of coarse-grained, macroscopic information from stochastic or atomistic simulations, such as molecular dynamics (MD). The approach functionally links the MD simulator with nonlinear manifold learning techniques. The added value comes from biasing the simulator toward unexplored phase-space regions by exploiting the smoothness of the gradually revealed intrinsic low-dimensional geometry of the FES...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634292/monte-carlo-sampling-for-stochastic-weight-functions
#18
Daan Frenkel, K Julian Schrenk, Stefano Martiniani
Conventional Monte Carlo simulations are stochastic in the sense that the acceptance of a trial move is decided by comparing a computed acceptance probability with a random number, uniformly distributed between 0 and 1. Here, we consider the case that the weight determining the acceptance probability itself is fluctuating. This situation is common in many numerical studies. We show that it is possible to construct a rigorous Monte Carlo algorithm that visits points in state space with a probability proportional to their average weight...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634291/rhodium-metalloinsertor-binding-generates-a-lesion-with-selective-cytotoxicity-for-mismatch-repair-deficient-cells
#19
Julie M Bailis, Alyson G Weidmann, Natalie F Mariano, Jacqueline K Barton
The DNA mismatch repair (MMR) pathway recognizes and repairs errors in base pairing and acts to maintain genome stability. Cancers that have lost MMR function are common and comprise an important clinical subtype that is resistant to many standard of care chemotherapeutics such as cisplatin. We have identified a family of rhodium metalloinsertors that bind DNA mismatches with high specificity and are preferentially cytotoxic to MMR-deficient cells. Here, we characterize the cellular mechanism of action of the most potent and selective complex in this family, [Rh(chrysi)(phen)(PPO)](2+) (Rh-PPO)...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28634290/geospatial-analysis-of-nonmedical-vaccine-exemptions-and-pertussis-outbreaks-in-the-united-states
#20
Carlin Aloe, Martin Kulldorff, Barry R Bloom
Because of increased numbers of recorded pertussis cases in the United States, this study sought to understand the role of nonmedical vaccine exemptions and waning immunity may have had on the resurgence of pertussis in the United States at the community level. We used geospatial scan statistics, SaTScan, version 9.4, to analyze nonmedical vaccine exemptions of children entering kindergarten in 2011 and 2012 and reported pertussis cases in 2012 for children in age groups 5 years and younger and 10 to 14 years...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
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