Superhalogen and Superacid

A superhalogen $\rm{F@C_{20}(CN)_{20}}$ and a corresponding Br{\o}nsted superacid were designed and investigated on DFT and DLPNO-CCSD(T) levels of theory. Calculated compounds have outstanding electron affinity and deprotonation energy, respectively. We consider superacid $\rm{H[F@C_{20}(CN)_{20}]}$ to be able to protonate molecular nitrogen. The stability of these structures is discussed, while some of the previous predictions concerning Br{\o}nsted superacids of record strength are doubted.Comment: 11 pages (main paper), 32 pages (supporting information), 10 figures, 10 tables, 62 reference

Thermodynamic and Kinetic Aspects of Two- and Three-Electron Redox Processes Mediated by Nitrogen Atom Transfer

Treatment of (meso-tetra-p-tolylporphyrinato)manganese(V) nitride, (TTP)Mn==N, with (octaethylporphyrinato) manganese(II), Mn(OEP), in toluene leads to the reversible transfer of the nitrido ligand between the two metal complexes to form (OEP)Mn Nand Mn(TTP). The net result is a formal three-electron reduction of (TTP)MnvN to (TTP)Mn11• This occurs with a second-order rate constant of (5.6 ± 1.2) X 103 M-1 s-1 to form an equilibrium mixture with K~ = 1.2 ± 0.5 at 20 °C. The thermodynamic and activation parameters for this process are t:.H0 = 2.0 ± 0.2 kcalfmol, t:.S = 7 .I ± 0.6 calfmol·K, t:.H* = 9.4 ± 0.7 kcal/mol, and t:.S* = -10 ± 2 cal/mol·K. In THF at 20 °C, the equilibrium constant is 1.8 ± 0.2 and the rate constant drops to 2.3 ± 0.3 M-1 s-1• When a manganese(III) porphyrin complex is used as a reductant, reversible nitrogen atom transfer still occurs but mediates a formal two-electron process. At 22 °C, the exchange process between (TTP)MnCI and (OEP)Mn==N produces (TTP)Mn==N and (OEP)MnCI with a second-order rate constant of 0.010 ± 0.007 M-1 s-1 (t:.H* = 19 ± 2 kcal/mol and t:.S* = -3 ± 6 cal/mol·K) and forms an equilibrium mixture with Keq = 24.3 ± 3.3 (t:.H 0 = -7.0 ± 0.6 kcal/mol and t:.S 0 = -17 ± 2 cal/mol·K). Evidence for the formation of a binuclear wnitrido intermediate is presented for both processes. For the two-electron redox reaction, kinetic studies and mechanistic probes support a pathway which involves an initial chloride dissociation from the Mn(III) complex. Nitrogen atom transfer subsequently occurs between the Mn==N complex and the four-coordinate Mn(III) cationic species

Landsat-7 ETM+ Radiometric Calibration Status

Now in its 17th year of operation, the Enhanced Thematic Mapper + (ETM+), on board the Landsat-7 satellite, continues to systematically acquire imagery of the Earth to add to the 40+ year archive of Landsat data. Characterization of the ETM+ on-orbit radiometric performance has been on-going since its launch in 1999. The radiometric calibration of the reflective bands is still monitored using on-board calibration devices, though the Pseudo-Invariant Calibration Sites (PICS) method has proven to be an effect tool as well. The calibration gains were updated in April 2013 based primarily on PICS results, which corrected for a change of as much as -0.2%/year degradation in the worst case bands. A new comparison with the SADE database of PICS results indicates no additional degradation in the updated calibration. PICS data are still being tracked though the recent trends are not well understood. The thermal band calibration was updated last in October 2013 based on a continued calibration effort by NASA/Jet Propulsion Lab and Rochester Institute of Technology. The update accounted for a 0.31 W/sq m/ sr/micron bias error. The updated lifetime trend is now stable to within + 0.4K

A role of OCRL in clathrin-coated pit dynamics and uncoating revealed by studies of Lowe syndrome cells

Mutations in the inositol 5-phosphatase OCRL cause Lowe syndrome and Dent's disease. Although OCRL, a direct clathrin interactor, is recruited to late-stage clathrin-coated pits, clinical manifestations have been primarily attributed to intracellular sorting defects. Here we show that OCRL loss in Lowe syndrome patient fibroblasts impacts clathrin-mediated endocytosis and results in an endocytic defect. These cells exhibit an accumulation of clathrin-coated vesicles and an increase in U-shaped clathrin-coated pits, which may result from sequestration of coat components on uncoated vesicles. Endocytic vesicles that fail to lose their coat nucleate the majority of the numerous actin comets present in patient cells. SNX9, an adaptor that couples late-stage endocytic coated pits to actin polymerization and which we found to bind OCRL directly, remains associated with such vesicles. These results indicate that OCRL acts as an uncoating factor and that defects in clathrin-mediated endocytosis likely contribute to pathology in patients with OCRL mutations

Interplay of Protein and DNA Structure Revealed in Simulations of the lac Operon

The E. coli Lac repressor is the classic textbook example of a protein that attaches to widely spaced sites along a genome and forces the intervening DNA into a loop. The short loops implicated in the regulation of the lac operon suggest the involvement of factors other than DNA and repressor in gene control. The molecular simulations presented here examine two likely structural contributions to the in-vivo looping of bacterial DNA: the distortions of the double helix introduced upon association of the highly abundant, nonspecific nucleoid protein HU and the large-scale deformations of the repressor detected in low-resolution experiments. The computations take account of the three-dimensional arrangements of nucleotides and amino acids found in crystal structures of DNA with the two proteins, the natural rest state and deformational properties of protein-free DNA, and the constraints on looping imposed by the conformation of the repressor and the orientation of bound DNA. The predicted looping propensities capture the complex, chain-length-dependent variation in repression efficacy extracted from gene expression studies and in vitro experiments and reveal unexpected chain-length-dependent variations in the uptake of HU, the deformation of repressor, and the folding of DNA. Both the opening of repressor and the presence of HU, at levels approximating those found in vivo, enhance the probability of loop formation. HU affects the global organization of the repressor and the opening of repressor influences the levels of HU binding to DNA. The length of the loop determines whether the DNA adopts antiparallel or parallel orientations on the repressor, whether the repressor is opened or closed, and how many HU molecules bind to the loop. The collective behavior of proteins and DNA is greater than the sum of the parts and hints of ways in which multiple proteins may coordinate the packaging and processing of genetic information. © 2013 Czapla et al

Hydrated electron generation by excitation of copper localized surface plasmon resonance

Hydrated electrons are important in radiation chemistry and chargetransfer reactions, with applications that include chemical damage of DNA, catalysis, and signaling. Conventionally, hydrated electrons are produced by pulsed radiolysis, sonolysis, two-ultraviolet-photon laser excitation of liquid water, or photodetachment of suitable electron donors. Here we report a method for the generation of hydrated electrons via single-visible-photon excitation of localized surface plasmon resonances (LSPRs) of supported sub-3 nm copper nanoparticles in contact with water. Only excitations at the LSPR maximum resulted in the formation of hydrated electrons, suggesting that plasmon excitation plays a crucial role in promoting electron transfer from the nanoparticle into the solution. The reactivity of the hydrated electrons was confirmed via proton reduction and concomitant H2 evolution in the presence of a Ru/ TiO2 catalyst

Calibration of Tethered Particle Motion Experiments

The Tethered Particle Motion (TPM) method has been used to observe and characterize a variety of protein-DNA interactions including DNA loping and transcription. TPM experiments exploit the Brownian motion of a DNA-tethered bead to probe biologically relevant conformational changes of the tether. In these experiments, a change in the extent of the bead’s random motion is used as a reporter of the underlying macromolecular dynamics and is often deemed sufficient for TPM analysis. However, a complete understanding of how the motion depends on the physical properties of the tethered particle complex would permit more quantitative and accurate evaluation of TPM data. For instance, such understanding can help extract details about a looped complex geometry (or multiple coexisting geometries) from TPM data. To better characterize the measurement capabilities of TPM experiments involving DNA tethers, we have carried out a detailed calibration of TPM magnitude as a function of DNA length and particle size. We also explore how experimental parameters such as acquisition time and exposure time affect the apparent motion of the tethered particle. We vary the DNA length from 200 bp to 2.6 kbp and consider particle diameters of 200, 490 and 970 nm. We also present a systematic comparison between measured particle excursions and theoretical expectations, which helps clarify both the experiments and models of DNA conformation

Landsat-7 ETM+: 12 years On-Orbit Reflective-Band Radiometric Performance

The Landsat-7 ETM+ sensor has been operating on orbit for more than 12 years and characterizations of its performance have been ongoing over this period. In general, the radiometric performance of the instrument has been remarkably stable: (1) Noise performance has degraded by 2% or less overall, with a few detectors displaying step changes in noise of 2% or less, (2) Coherent noise frequencies and magnitudes have generally been stable, though the within-scan amplitude variation of the 20kHz noise in bands 1 and 8 disappeared with the failure of the scan line corrector and a new similar frequency noise (now about 18kHz) has appeared in two detectors in band 5 and increased in magnitude with time, (3) Bias stability has been better than 0.25 DN out of a normal value of 15 DN in high gain, (4) Relative gains, the differences in response between the detectors in the band, have generally changed by 0.1% or less over the mission, with the exception of a few detectors with a step response change of 1% or less and (5) Gain stability averaged across all detectors in a band, which is related to the stability of the absolute calibration, has been more stable than the techniques used to measure it. Due to the inability to confirm changes in the gain (beyond a few detectors that have been corrected back to the band average), ETM+ reflective band data continues to be calibrated with the pre-launch measured gains. In the worst case some bands may have changed as much as 2% in uncompensated absolute calibration over the 12 years

Impact of Fractional Flow Reserve Derived from Coronary Computed Tomography Angiography on Heart Team Treatment Decision-Making in Patients with Multivessel Coronary Artery Disease: Insights from the SYNTAX III REVOLUTION Trial

Background: Fractional flow reserve (FFR) is a reliable tool for the functional assessment of coronary stenoses. FFR computed tomography (CT) derived (FFRCT) has shown to be accurate, but its clinical usefulness in patients with complex coronary artery disease remains to be investigated. The present study sought to determine the impact of FFRCT on heart team's treatment decision-making and selection of vessels for revascularization in patients with 3-vessel coronary artery disease. Methods: The trial was an international, multicenter study randomizing 2 heart teams to make a treatment decision between percutaneous coronary interventions and coronary artery bypass grafting using either coronary computed tomography angiography or conventional angiography. The heart teams received the FFRCT and had to make a treatment decision and planning integrating the functional component of the stenoses. Each heart team calculated the anatomic SYNTAX score, the noninvasive functional SYNTAX score and subsequently integrated the clinical information to compute the SYNTAX score III providing a treatment recommendation, that is, coronary artery bypass grafting, percutaneous coronary intervention, or equipoise coronary artery bypass grafting-percutaneous coronary intervention. The primary objective was to determine the proportion of patients in whom FFRCT changed the treatment decision and planning. Results: Overall, 223 patients were included. Coronary computed tomography angiography assessment was feasible in 99% of the patients and FFRCT analysis in 88%. FFRCT was available for 1030 lesions (mean FFRCT value 0.64\ub113). A treatment recommendation of coronary artery bypass grafting was made in 24% of the patients with coronary computed tomography angiography with FFRCT. The addition of FFRCT changed the treatment decision in 7% of the patients and modified selection of vessels for revascularization in 12%. With conventional angiography as reference, FFRCT assessment resulted in reclassification of 14% of patients from intermediate and high to low SYNTAX score tertile. Conclusions: In patients with 3-vessel coronary artery disease, a noninvasive physiology assessment using FFRCT changed heart team's treatment decision-making and procedural planning in one-fifth of the patients