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Christopher M Thompson, Mohamad Kodaimati, Dana Westmoreland, Raul Calzada, Emily A Weiss
This paper describes the pH dependence of the excitonic energies and dynamics of CdS quantum dots (QDs) capped with phosphonopropionate (PPA) in water. QDs capped with PPA carry a negative charge on their surfaces upon deprotonation of PPA above pH ∼ 8.5; the resultant electric field induces large changes in the QD's optical properties. Between pH 5.6 and 12.0, an increase in pH is accompanied by a 47-meV bathochromic shift in the bandgap of the QDs and a decrease in the Stokes shift by ∼4.3 meV/pH unit...
October 6, 2016: Journal of Physical Chemistry Letters
Andreas C Scheinost, Robin Steudtner, René Hübner, Stephan Weiss, Frank Bok
The Np(V) retention by siderite, an Fe(II) carbonate mineral with relevance for the near-field of high-level radioactive waste repositories, was investigated under anoxic conditions. Batch sorption experiments show that siderite has a high affinity for aqueous Np(V)O2(+) across pH 7 to 13 as expressed by solid-water distribution coefficients, log Rd, > 5, similar to the log Rd determined for the (solely) tetravalent actinide Th on calcite, suggesting reduction of Np(V) to Np(IV) by siderite. Np L3-edge X-ray absorption near edge (XANES) spectroscopy conducted in a pH range typical for siderite-containing host rocks (7-8), confirmed the tetravalent Np oxidation state...
October 4, 2016: Environmental Science & Technology
Kamrouz Ghadimi, Jacob T Gutsche, Harish Ramakrishna, Samuel L Setegne, Kirk R Jackson, John G Augoustides, E Andrew Ochroch, Stuart J Weiss, Joseph E Bavaria, Albert T Cheung
OBJECTIVE: Metabolic acidosis after deep hypothermic circulatory arrest (DHCA) for thoracic aortic operations is commonly managed with sodium bicarbonate (NaHCO 3 ). The purpose of this study was to determine the relationships between total NaHCO 3 dose and the severity of metabolic acidosis, duration of mechanical ventilation, duration of vasoactive infusions, and Intensive Care Unit (ICU) or hospital length of stay (LOS). METHODS: In a single center, retrospective study, 87 consecutive elective thoracic aortic operations utilizing DHCA, were studied...
July 2016: Annals of Cardiac Anaesthesia
Chen Wang, Emily A Weiss
Energy transfer (EnT) of near-infrared (NIR) excitons enables applications in harvesting of solar energy and biological imaging. Fast exciton extraction from NIR-absorbing Pb-chalcogenide quantum dots (QDs) may allow utilization of the photon downconversion (multiple exciton generation) process that occurs in those QDs to amplify signal in QD-based sensors or photocurrent in QD-based photovoltaics. This paper describes subnanosecond extraction of NIR excitons from PbS QDs by adsorbed J-aggregates of cyanine dye in aqueous dispersions...
August 3, 2016: Journal of the American Chemical Society
Kai Schwedtmann, Robin Schoemaker, Felix Hennersdorf, Antonio Bauzá, Antonio Frontera, Robert Weiss, Jan J Weigand
2-Phosphanyl-substituted imidazolium salts 2-PR2(4,5-Cl-Im)[OTf] (9a,b[OTf]) (4,5-Cl-Im = 4,5-dichloro-1,3-bis(2,6-di-isopropylphenyl)-imidazolium) (a: R = Cy, b: R = Ph) are prepared from the reaction of R2PCl (R = Cy, Ph) with NHC 8 (4,5-dichloro-1,3-bis(2,6-di-isopropylphenyl)-imidazolin-2-ylidene) in the presence of Me3SiOTf. 5-Phospanyl-substituted imidazolium salts 5-PR2(2,4-Cl-Im)[OTf] (10a,b[OTf]) are obtained in quantitative yield when a slight excess of the NHC 8 is used. 5-Phosphonio-substituted imidazolium salts 5-PR2Me(2,4-Cl-Im)[OTf]2 (14a,b[OTf]2) and 5-PR2F(2,4-Cl-Im)[OTf]2 (16a,b[OTf]2) result from methylation reaction or oxidation of 10a,b[OTf] with XeF2 and subsequent fluoride abstraction...
July 28, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Dmitri V Konarev, Alexey V Kuzmin, Yoshiaki Nakano, Salavat S Khasanov, Manabu Ishikawa, Akihiro Otsuka, Hideki Yamochi, Gunzi Saito, Rimma N Lyubovskaya
The interaction of Sn(IV)Cl2Pc with an excess of NaBPh4 in the presence of fullerenes C60 and C70 provides complete dissolution of Sn(IV)Cl2Pc and the formation of blue solutions from which the crystals of [SnPhPc(2-)](+)(BPh4)(-)·C6H14 () or [SnPhPc˙(3-)]·C6H4Cl2 () were selectively isolated. According to the optical spectra, salt contains dianionic Pc(2-) macrocycles, whereas macrocycles are reduced to form the Pc˙(3-) radical trianions in . As a result, the phthalocyanine macrocycle is dianionic in , and the positive charge of Sn(IV) is compensated by the Ph(-), Pc(2-), and BPh4(-) anions in this compound...
June 28, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Tatsuki Sugi, Yan Fen Ma, Tadakimi Tomita, Fumi Murakoshi, Michael S Eaton, Rama Yakubu, Bing Han, Vincent Tu, Kentaro Kato, Shin-Ichiro Kawazu, Nishith Gupta, Elena S Suvorova, Michael W White, Kami Kim, Louis M Weiss
UNLABELLED: Toxoplasma gondii is an obligate intracellular apicomplexan parasite that infects warm-blooded vertebrates, including humans. Asexual reproduction in T. gondii allows it to switch between the rapidly replicating tachyzoite and quiescent bradyzoite life cycle stages. A transient cyclic AMP (cAMP) pulse promotes bradyzoite differentiation, whereas a prolonged elevation of cAMP inhibits this process. We investigated the mechanism(s) by which differential modulation of cAMP exerts a bidirectional effect on parasite differentiation...
2016: MBio
Matthias Sendler, Sandrina Maertin, Daniel John, Maria Persike, F Ulrich Weiss, Burkhard Krüger, Thomas Wartmann, Preshit Wagh, Walter Halangk, Norbert Schaschke, Julia Mayerle, Markus M Lerch
Pancreatitis is associated with premature activation of digestive proteases in the pancreas. The lysosomal hydrolase cathepsin B (CTSB) is a known activator of trypsinogen, and its deletion reduces disease severity in experimental pancreatitis. Here we studied the activation mechanism and subcellular compartment in which CTSB regulates protease activation and cellular injury. Cholecystokinin (CCK) increased the activity of CTSB, cathepsin L, trypsin, chymotrypsin, and caspase 3 in vivo and in vitro and induced redistribution of CTSB to a secretory vesicle-enriched fraction...
July 8, 2016: Journal of Biological Chemistry
Wolfram Adlassnig, Yasmin S Weiss, Stefan Sassmann, Georg Steinhauser, Florian Hofhansl, Nils Baumann, Irene K Lichtscheidl, Ingeborg Lang
Historic mining in the Eastern Alps has left us with a legacy of numerous spoil heaps hosting specific, metal tolerant vegetation. Such habitats are characterized by elevated concentrations of toxic elements but also by high irradiation, a poorly developed substrate or extreme pH of the soil. This study investigates the distribution of vascular plants, mosses and lichens on a copper spoil heap on the ore bearing Knappenberg formed by Prebichl Layers and Werfener Schist in Lower Austria. It serves as a model for discriminating between various ecological traits and their effects on vegetation...
September 1, 2016: Science of the Total Environment
L Bassin, B Weiss, G Cranney, D Gimpel, P Gilhooly, R Smith, Z Akhunji, P Grant, H Wolfenden
INTRODUCTION: American Heart Association (AHA) guidelines recommend mitral valve repair for myxomatous mitral regurgitation whenever possible to prevent LV dysfunction and early mortality. Here we review our early operative outcomes with mitral valve repair for myxomatous mitral regurgitation. METHODS: We collected data from 586 consecutive patients that underwent mitral repair for myxomatous disease at the Prince Henry and Prince of Wales Hospitals Sydney between 1997 and 2012...
August 2016: Heart, Lung & Circulation
Chutima Thongkaew, Benjamin Zeeb, Monika Gibis, Jörg Hinrichs, Jochen Weiss
The effect of pH change on the morphology of whey protein isolate (WPI)-pectin dispersions obtained from phase-separated systems after mild shear was studied. The purpose of this study was to examine the impact of mixing speed on the initial particle size of biopolymer complexes and their structure morphology after sequentially changing the pH. Therefore, solutions of WPI and pectin were combined at pH 6.1, allowed to phase separate and were then mildly homogenized at 50, 100, and 150 rpm, respectively, to form a dispersion containing differently sized WPI droplets in a surrounding pectin-rich phase...
May 2016: Journal of Food Science
Alexia Viguier, Cecile Boyer, Christophe Chassenieux, Lazhar Benyahia, Jérôme Guicheux, Pierre Weiss, Gildas Rethore, Taco Nicolai
Interpenetrated gels of biocompatible polysaccharides alginate and silanized hydroxypropyl methyl cellulose (Si-HPMC) have been studied in order to assess their potential as scaffolds for the regeneration of human tissues. Si-HPMC networks were formed by reduction of the pH to neutral and alginate networks were formed by progressive in situ release of Ca(2+). Linear and non-linear mechanical properties of the mixed gels at different polymer and calcium concentrations were compared with those of the corresponding single gels...
May 2016: Journal of Materials Science. Materials in Medicine
Stefan Datz, Christian Argyo, Michael Gattner, Veronika Weiss, Korbinian Brunner, Johanna Bretzler, Constantin von Schirnding, Adriano A Torrano, Fabio Spada, Milan Vrabel, Hanna Engelke, Christoph Bräuchle, Thomas Carell, Thomas Bein
Effective and controlled drug delivery systems with on-demand release and targeting abilities have received enormous attention for biomedical applications. Here, we describe a novel enzyme-based cap system for mesoporous silica nanoparticles (MSNs) that is directly combined with a targeting ligand via bio-orthogonal click chemistry. The capping system is based on the pH-responsive binding of an aryl-sulfonamide-functionalized MSN and the enzyme carbonic anhydrase (CA). An unnatural amino acid (UAA) containing a norbornene moiety was genetically incorporated into CA...
April 21, 2016: Nanoscale
Oksana Gerlits, Troy Wymore, Amit Das, Chen-Hsiang Shen, Jerry M Parks, Jeremy C Smith, Kevin L Weiss, David A Keen, Matthew P Blakeley, John M Louis, Paul Langan, Irene T Weber, Andrey Kovalevsky
Neutron crystallography was used to directly locate two protons before and after a pH-induced two-proton transfer between catalytic aspartic acid residues and the hydroxy group of the bound clinical drug darunavir, located in the catalytic site of enzyme HIV-1 protease. The two-proton transfer is triggered by electrostatic effects arising from protonation state changes of surface residues far from the active site. The mechanism and pH effect are supported by quantum mechanics/molecular mechanics (QM/MM) calculations...
April 11, 2016: Angewandte Chemie
Kritika Mohan, Gregory A Weiss
Long fascinating to biologists, viruses offer nanometer-scale benchtops for building molecular-scale devices and materials. Viruses tolerate a wide range of chemical modifications including reaction conditions, pH values, and temperatures. Recent examples of nongenetic manipulation of viral surfaces have extended viruses into applications ranging from biomedical imaging, drug delivery, tissue regeneration, and biosensors to materials for catalysis and energy generation. Chemical reactions on the phage surface include both covalent and noncovalent modifications, including some applied in conjunction with genetic modifications...
May 20, 2016: ACS Chemical Biology
Hana McFeeters, Venu Gopal Vandavasi, Kevin L Weiss, Leighton Coates, Robert L McFeeters
Perdeuterated peptidyl-tRNA hydrolase 1 from Pseudomonas aeruginosa was crystallized for structural analysis using neutron diffraction. Crystals of perdeuterated protein were grown to 0.15 mm(3) in size using batch crystallization in 22.5% polyethylene glycol 4000, 100 mM Tris pH 7.5, 10%(v/v) isopropyl alcohol with a 20-molar excess of trilysine as an additive. Neutron diffraction data were collected from a crystal at room temperature using the MaNDi single-crystal diffractometer at Oak Ridge National Laboratory...
March 2016: Acta Crystallographica. Section F, Structural Biology Communications
A Wannhoff, T Hippchen, C S Weiss, K Friedrich, C Rupp, C Neumann-Haefelin, M Dollinger, C Antoni, U Stampfl, P Schemmer, W Stremmel, K H Weiss, B Radeleff, H A Katus, D N Gotthardt
BACKGROUND: Transjugular intrahepatic portosystemic shunt (TIPSS) cause haemodynamic changes in patients with cirrhosis, yet little is known about long-term cardiopulmonary outcomes. AIM: To evaluate the long-term cardiopulmonary outcome after TIPSS. METHODS: We evaluated cardiopulmonary parameters including echocardiography during long-term follow-up after TIPSS. Results at 1-5 years after TIPSS were compared to those of cirrhotic controls...
May 2016: Alimentary Pharmacology & Therapeutics
D Martel, A Guerra, P Turek, J Weiss, B Vileno
In the field of solar fuel cells, the development of efficient photo-converting semiconductors remains a major challenge. A rational analysis of experimental photocatalytic results obtained with material in colloïdal suspensions is needed to access fundamental knowledge required to improve the design and properties of new materials. In this study, a simple system electron donor/nano-TiO2 is considered and examined via spin scavenging electron paramagnetic resonance as well as a panel of analytical techniques (composition, optical spectroscopy and dynamic light scattering) for selected type of nano-TiO2...
April 1, 2016: Journal of Colloid and Interface Science
Stephen C Jensen, Stephanie Bettis Homan, Emily A Weiss
This paper describes the use of cadmium sulfide quantum dots (CdS QDs) as visible-light photocatalysts for the reduction of nitrobenzene to aniline through six sequential photoinduced, proton-coupled electron transfers. At pH 3.6-4.3, the internal quantum yield of photons-to-reducing electrons is 37.1% over 54 h of illumination, with no apparent decrease in catalyst activity. Monitoring of the QD exciton by transient absorption reveals that, for each step in the catalytic cycle, the sacrificial reductant, 3-mercaptopropionic acid, scavenges the excitonic hole in ∼5 ps to form QD(•-); electron transfer to nitrobenzene or the intermediates nitrosobenzene and phenylhydroxylamine then occurs on the nanosecond time scale...
February 10, 2016: Journal of the American Chemical Society
Éva Gráczer, Tamás Szimler, Anita Garamszegi, Petr V Konarev, Anikó Lábas, Julianna Oláh, Anna Palló, Dmitri I Svergun, Angelo Merli, Péter Závodszky, Manfred S Weiss, Mária Vas
The key active site residues K185, Y139, D217, D241, D245, and N102 of Thermus thermophilus 3-isopropylmalate dehydrogenase (Tt-IPMDH) have been replaced, one by one, with Ala. A drastic decrease in the kcat value (0.06% compared to that of the wild-type enzyme) has been observed for the K185A and D241A mutants. Similarly, the catalytic interactions (Km values) of these two mutants with the substrate IPM are weakened by more than 1 order of magnitude. The other mutants retained some (1-13%) of the catalytic activity of the wild-type enzyme and do not exhibit appreciable changes in the substrate Km values...
January 26, 2016: Biochemistry
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