| 1. |
- Abelev, Betty, et al.
(författare)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 2. |
- Agarwal, Vaibhav, et al.
(författare)
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Binding of Streptococcus pneumoniae endopeptidase O (PepO) to complement component C1q modulates the complement attack and promotes host cell adherence.
- 2014
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 289:22, s. 15833-15844
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Tidskriftsartikel (refereegranskat)abstract
- The Gram-positive species Streptococcus pneumoniae is a human pathogen causing severe local and life-threatening invasive diseases associated with high mortality rates and death. We demonstrated recently that pneumococcal endopeptidase O (PepO) is an ubiquitously expressed, multifunctional plasminogen and fibronectin binding protein facilitating host cell invasion and evasion of innate immunity. In this study we found that PepO interacts directly with the complement C1q protein, thereby attenuating the classical complement pathway and facilitating pneumococcal complement escape. PepO binds both free C1q and C1 complex in a dose-dependent manner based on ionic interactions. Our results indicate that recombinant PepO specifically inhibits the classical pathway of complement activation in both hemolytic and complement deposition assays. This inhibition is due to direct interaction of PepO with C1q, leading to a strong activation of the classical complement pathway and results in consumption of complement components. In addition, PepO binds the classical complement pathway inhibitor C4BP, thereby regulating downstream complement activation. Importantly, pneumococcal surface-exposed PepO-C1q interaction mediates bacterial adherence to host epithelial cells. Taken together, PepO facilitates C1q-mediated bacterial adherence, while its localized release consumes complement as a result of its activation following binding of C1q, thus representing an additional mechanism of human complement escape by this versatile pathogen.
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| 3. |
- Agarwal, Vaibhav, et al.
(författare)
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Enolase of Streptococcus pneumoniae Binds Human Complement Inhibitor C4b-Binding Protein and Contributes to Complement Evasion.
- 2012
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Ingår i: Journal of immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 189:7, s. 3575-3584
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pneumoniae (pneumococcus) is a pathogen that causes severe local and life-threatening invasive diseases, which are associated with high mortality rates. Pneumococci have evolved several strategies to evade the host immune system, including complement to disseminate and to survive in various host niches. Thus, pneumococci bind complement inhibitors such as C4b-binding protein (C4BP) and factor H via pneumococcal surface protein C, thereby inhibiting the classical and alternative complement pathways. In this study, we identified the pneumococcal glycolytic enzyme enolase, a nonclassical cell surface and plasminogen-binding protein, as an additional pneumococcal C4BP-binding protein. Furthermore, we demonstrated that human, but not mouse, C4BP bound pneumococci. Recombinant enolase bound in a dose-dependent manner C4BP purified from plasma, and the interaction was reduced by increasing ionic strength. Enolase recruited C4BP and plasminogen, but not factor H, from human serum. Moreover, C4BP and plasminogen bound to different domains of enolase as they did not compete for the interaction with enolase. In direct binding assays with recombinant C4BP mutants lacking individual domains, two binding sites for enolase were identified on the complement control protein (CCP) domain 1/CCP2 and CCP8 of the C4BP α-chains. C4BP bound to the enolase retained its cofactor activity as determined by C4b degradation. Furthermore, in the presence of exogenously added enolase, an increased C4BP binding to and subsequently decreased C3b deposition on pneumococci was observed. Taken together, pneumococci specifically interact with human C4BP via enolase, which represents an additional mechanism of human complement control by this versatile pathogen.
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| 4. |
- Agarwal, Vaibhav, et al.
(författare)
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Streptococcus pneumoniae endopeptidase O (PepO): a multifunctional plasminogen and fibronectin binding protein, facilitating evasion of innate immunity and invasion of host cells.
- 2013
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 288:10, s. 6849-6863
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pneumoniae infections remain a major cause of morbidity and mortality worldwide. Therefore a detailed understanding and characterization of the mechanism of host cell colonization and dissemination is critical in order to gain control over this versatile pathogen. Here we identified a novel 72 kDa pneumococcal protein endopeptidase O (PepO), as a plasminogen and fibronectin binding protein. Using a collection of clinical isolates, representing different serotypes, we found PepO to be ubiquitously present both at the gene and at the protein level. In addition, PepO protein was secreted in a growth-phase dependent manner to the culture supernatants of the pneumococcal isolates. Recombinant PepO bound human plasminogen and fibronectin in a dose-dependent manner and plasminogen did not compete with fibronectin for binding PepO. PepO bound plasminogen via lysine residues and the interaction was influenced by ionic strength. Moreover, upon activation of PepO bound plasminogen by urokinase-type plasminogen activator, generated plasmin cleaved complement protein C3b thus assisting in complement control. Furthermore, direct binding assays demonstrated the interaction of PepO with epithelial and endothelial cells that in turn blocked pneumococcal adherence. Moreover, a pepO-mutant strain showed impaired adherence to and invasion of host cells compared to their isogenic wild-type strains. Taken together, the results demonstrated that PepO is ubiquitously expressed plasminogen and fibronectin binding protein, which plays role in pneumococcal invasion of host cells and aids in immune evasion.
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| 5. |
- Blom, Anna, et al.
(författare)
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Streptococcus pneumoniae phosphoglycerate kinase is a novel complement inhibitor affecting the membrane attack complex formation.
- 2014
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 289:47
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Tidskriftsartikel (refereegranskat)abstract
- The Gram-positive bacterium Streptococcus pneumoniae is a major human pathogen that causes infections ranging from acute otitis media to life-threatening invasive disease. Pneumococci have evolved several strategies to circumvent the host immune response, in particular the complement attack. The pneumococcal glycolytic enzyme phosphoglycerate kinase (PGK) is both secreted and bound to the bacterial surface and simultaneously binds plasminogen and its activator tPA. In the present study, we demonstrate that PGK has an additional role in modulating the complement attack. PGK interacted with the membrane attack complex (MAC) components C5, C7 and C9, thereby blocking the assembly and membrane insertion of MAC resulting in significant inhibition of the hemolytic activity of human serum. Recombinant PGK interacted in a dose-dependent manner with these terminal pathway proteins, and the interactions were ionic in nature. In addition, PGK inhibited C9 polymerization both in the fluid phase and on the surface of sheep erythrocytes. Interestingly, PGK bound several MAC proteins simultaneously. While C5 and C7 had partially overlapping binding sites on PGK, C9 did not compete with either one for PGK binding. Moreover, PGK significantly inhibited MAC deposition via both the classical and alternative pathway at the pneumococcal surface. Additionally, upon activation plasmin(ogen) bound to PGK cleaved the central complement protein C3b thereby further modifying the complement attack. In conclusion, our data demonstrate for the first time, to our knowledge, a novel pneumococcal inhibitor of the terminal complement cascade aiding complement evasion by this important pathogen.
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| 6. |
- Fischer Hübner, Simone, 1963-, et al.
(författare)
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Human-Computer Interaction
- 2011
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Ingår i: Digital privacy. - Berlin, Heidelberg : Springer. - 9783642190490 ; , s. 569-595
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Bokkapitel (refereegranskat)
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| 7. |
- Mitzner, Rolf, et al.
(författare)
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L-Edge X-ray Absorption Spectroscopy of Dilute Systems Relevant to Metalloproteins Using an X-ray Free-Electron Laser
- 2013
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185 .- 1948-7185. ; 4:21, s. 3641-3647
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Tidskriftsartikel (refereegranskat)abstract
- L-edge spectroscopy of 3d transition metals provides important electronic structure information and has been used in many fields. However, the use of this method for studying dilute aqueous systems, such as metalloenzymes, has not been prevalent because of severe radiation damage and the lack of suitable detection systems. Here we present spectra from a dilute Mn aqueous solution using a high-transmission zone-plate spectrometer at the Linac Coherent Light Source (LCLS). The spectrometer has been optimized for discriminating the Mn L-edge signal from the overwhelming 0 K-edge background that arises from water and protein itself, and the ultrashort LCLS X-ray pulses can outrun X-ray induced damage. We show that the deviations of the partial-fluorescence yield-detected spectra from the true absorption can be well modeled using the state-dependence of the fluorescence yield, and discuss implications for the application of our concept to biological samples.
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| 8. |
- Schreck, Simon, et al.
(författare)
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Reabsorption of Soft X-Ray Emission at High X-Ray Free-Electron Laser Fluences
- 2014
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:15, s. 153002-
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Tidskriftsartikel (refereegranskat)abstract
- We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.
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