| 171. |
- Ohmer, Christopher J., et al.
(författare)
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XFEL serial crystallography reveals the room temperature structure of methyl-coenzyme M reductase
- 2022
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Ingår i: Journal of Inorganic Biochemistry. - : Elsevier BV. - 0162-0134 .- 1873-3344. ; 230, s. 111768-
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Tidskriftsartikel (refereegranskat)abstract
- Methyl-Coenzyme M Reductase (MCR) catalyzes the biosynthesis of methane in methanogenic archaea, using a catalytic Ni-centered Cofactor F430 in its active site. It also catalyzes the reverse reaction, that is, the anaerobic activation and oxidation, including the cleavage of the C-H bond in methane. Because methanogenesis is the major source of methane on earth, understanding the reaction mechanism of this enzyme can have massive implications in global energy balances. While recent publications have proposed a radical-based catalytic mechanism as well as novel sulfonate-based binding modes of MCR for its native substrates, the structure of the active state of MCR, as well as a complete characterization of the reaction, remain elusive. Previous attempts to structurally characterize the active MCR-Ni(I) state have been unsuccessful due to oxidation of the redox- sensitive catalytic Ni center. Further, while many cryo structures of the inactive Ni(II)-enzyme in various substrates bound forms have been published, no room temperature structures have been reported, and the structure and mechanism of MCR under physiologically relevant conditions is not known. In this study, we report the first room temperature structure of the MCRred1-silent Ni(II) form using an X-ray Free-Electron Laser (XFEL), with simultaneous X-ray Emission Spectroscopy (XES) and X-ray Diffraction (XRD) data collection. In celebration of the seminal contributions of inorganic chemist Dick Holm to our understanding of nickel-based catalysis, we are honored to announce our findings in this special issue dedicated to this remarkable pioneer of bioinorganic chemistry.
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| 172. |
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| 173. |
- Porth, Oliver, et al.
(författare)
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The Event Horizon General Relativistic Magnetohydrodynamic Code Comparison Project
- 2019
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Ingår i: Astrophysical Journal, Supplement Series. - : American Astronomical Society. - 1538-4365 .- 0067-0049. ; 243:2
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Tidskriftsartikel (refereegranskat)abstract
- Recent developments in compact object astrophysics, especially the discovery of merging neutron stars by LIGO, the imaging of the black hole in M87 by the Event Horizon Telescope, and high- precision astrometry of the Galactic Center at close to the event horizon scale by the GRAVITY experiment motivate the development of numerical source models that solve the equations of general relativistic magnetohydrodynamics (GRMHD). Here we compare GRMHD solutions for the evolution of a magnetized accretion flow where turbulence is promoted by the magnetorotational instability from a set of nine GRMHD codes: Athena++, BHAC, Cosmos++, ECHO, H-AMR, iharm3D, HARM-Noble, IllinoisGRMHD, and KORAL. Agreement among the codes improves as resolution increases, as measured by a consistently applied, specially developed set of code performance metrics. We conclude that the community of GRMHD codes is mature, capable, and consistent on these test problems.
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| 174. |
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| 175. |
- Rohde, L. E., et al.
(författare)
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Sacubitril/Valsartan and Sudden Cardiac Death According to Implantable Cardioverter-Defibrillator Use and Heart Failure Cause: A PARADIGM-HF Analysis
- 2020
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Ingår i: Jacc-Heart Failure. - : Elsevier BV. - 2213-1779. ; 8:10, s. 844-855
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES The purpose of this study was to investigate the effect of sacubitril/valsartan therapy on sudden cardiac death (SCD) according to the use of and eligibility for an implantable cardioverter-defibrillator (ICD), stratified by heart failure cause. BACKGROUND SCD still accounts for a significant proportion of overall mortality in heart failure with reduced ejection fraction (HFrEF). METHODS Patients enrolled in the PARADIGM-HF (Prospective Comparison of ARNI with an ACE-Inhibitor to Determine Impact on Global Mortality and Morbidity in Heart Failure) trial (n = 8,399) were evaluated to assess patterns of ICD implantation and eligibility according to clinical guidelines. The impact of ICD (adjusted for propensity of ICD implantation) and sacubitril/valsartan therapy on SCD was evaluated by using cause-specific Cox models and competing risk analysis. RESULTS At baseline, of the 7,145 patients (85%) eligible for ICD implantation, only 1,243 (15%) had an ICD. Use of ICD varied by region with the highest rates in North America (56%) and lowest in Asia-Pacific (1.7%). In a propensity score-adjusted analysis, use of an ICD was associated with a 56% lower risk of SCD in ICD-eligible patients, in both patients with ischemic (p < 0.001) and nonischemic cardiomyopathy (p = 0.02). Sacubitril/valsartan reduced SCD risk in patients with an ICD (hazard ratio [HR]: 0.49; 95% confidence interval [CI]: 0.25 to 0.99) and in those who were eligible for but did not receive an ICD (HR: 0.81; 95% CI: 0.67 to 0.98). This effect was particularly evident in nonischemic cardiomyopathy (p < 0.05), although interaction with the cause of HF was not significant (p = 0.11 in subjects using an ICD and p = 0.25 in eligible nonusers). CONCLUSIONS Use of an ICD was associated with lower rates of SCD, regardless of HF cause but was underused in most regions of the world in the PARADIGM-HF study. Sacubitril/valsartan reduced SCD risk regardless of use of an ICD or eligibility, particularly in ICD users and nonischemic cardiomyopathy. (c) 2020 Published by Elsevier on behalf of the American College of Cardiology Foundation.
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| 176. |
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| 177. |
- Senapathi, Deepa, et al.
(författare)
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Wild insect diversity increases inter-annual stability in global crop pollinator communities
- 2021
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954 .- 0962-8452. ; 288:1947
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Tidskriftsartikel (refereegranskat)abstract
- While an increasing number of studies indicate that the range, diversity and abundance of many wild pollinators has declined, the global area of pollinator-dependent crops has significantly increased over the last few decades. Crop pollination studies to date have mainly focused on either identifying different guilds pollinating various crops, or on factors driving spatial changes and turnover observed in these communities. The mechanisms driving temporal stability for ecosystem functioning and services, however, remain poorly understood. Our study quantifies temporal variability observed in crop pollinators in 21 different crops across multiple years at a global scale. Using data from 43 studies from six continents, we show that (i) higher pollinator diversity confers greater inter-annual stability in pollinator communities, (ii) temporal variation observed in pollinator abundance is primarily driven by the three-most dominant species, and (iii) crops in tropical regions demonstrate higher inter-annual variability in pollinator species richness than crops in temperate regions. We highlight the importance of recognizing wild pollinator diversity in agricultural landscapes to stabilize pollinator persistence across years to protect both biodiversity and crop pollination services. Short-term agricultural management practices aimed at dominant species for stabilizing pollination services need to be considered alongside longer term conservation goals focussed on maintaining and facilitating biodiversity to confer ecological stability.
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| 178. |
- Simon, Philipp S., et al.
(författare)
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Capturing the sequence of events during the water oxidation reaction in photosynthesis using XFELs
- 2023
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Ingår i: FEBS Letters. - : John Wiley & Sons. - 0014-5793 .- 1873-3468. ; 597:1, s. 30-37
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Tidskriftsartikel (refereegranskat)abstract
- Ever since the discovery that Mn was required for oxygen evolution in plants by Pirson in 1937 and the period-four oscillation in flash-induced oxygen evolution by Joliot and Kok in the 1970s, understanding of this process has advanced enormously using state-of-the-art methods. The most recent in this series of innovative techniques was the introduction of X-ray free-electron lasers (XFELs) a decade ago, which led to another quantum leap in the understanding in this field, by enabling operando X-ray structural and X-ray spectroscopy studies at room temperature. This review summarizes the current understanding of the structure of Photosystem II (PS II) and its catalytic centre, the Mn4CaO5 complex, in the intermediate Si (i = 0–4)-states of the Kok cycle, obtained using XFELs.
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| 179. |
- Swamy, P. B., et al.
(författare)
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Reduced look ahead orthogonal matching pursuit
- 2014
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Ingår i: 2014 20th National Conference on Communications, NCC 2014. - : IEEE Computer Society. - 9781479923618 ; , s. 6811329-
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Konferensbidrag (refereegranskat)abstract
- Compressed Sensing (CS) is an elegant technique to acquire signals and reconstruct them efficiently by solving a system of under-determined linear equations. The excitement in this field stems from the fact that we can sample at a rate way below the Nyquist rate and still reconstruct the signal provided some conditions are met. Some of the popular greedy reconstruction algorithms are the Orthogonal Matching Pursuit (OMP), the Subspace Pursuit (SP) and the Look Ahead Orthogonal Matching Pursuit (LAOMP). The LAOMP performs better than the OMP. However, when compared to the SP and the OMP, the computational complexity of LAOMP is higher. We introduce a modified version of the LAOMP termed as Reduced Look Ahead Orthogonal Matching Pursuit (Reduced LAOMP). Reduced LAOMP uses prior information from the results of the OMP and the SP in the quest to speedup the look ahead strategy in the LAOMP. Monte Carlo simulations of this algorithm deliver promising results.
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| 180. |
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