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| 3. |
- Bombarda, F., et al.
(författare)
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Runaway electron beam control
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
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Tidskriftsartikel (refereegranskat)
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| 14. |
- Krasilnikov, A., et al.
(författare)
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Evidence of 9 Be + p nuclear reactions during 2ω CH and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas
- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:2
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Tidskriftsartikel (refereegranskat)abstract
- The intensity of 9Be + p nuclear fusion reactions was experimentally studied during second harmonic (2ω CH) ion-cyclotron resonance heating (ICRH) and further analyzed during fundamental hydrogen minority ICRH of JET-ILW hydrogen and deuterium plasmas. In relatively low-density plasmas with a high ICRH power, a population of fast H+ ions was created and measured by neutral particle analyzers. Primary and secondary nuclear reaction products, due to 9Be + p interaction, were observed with fast ion loss detectors, γ-ray spectrometers and neutron flux monitors and spectrometers. The possibility of using 9Be(p, d)2α and 9Be(p, α)6Li nuclear reactions to create a population of fast alpha particles and study their behaviour in non-active stage of ITER operation is discussed in the paper.
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| 23. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:1
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Forskningsöversikt (refereegranskat)
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| 24. |
- Eversmann, D., et al.
(författare)
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New Method for a Continuous Determination of the Spin Tune in Storage Rings and Implications for Precision Experiments
- 2015
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 115:9
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Tidskriftsartikel (refereegranskat)abstract
- A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune-defined as the number of spin precessions per turn-is given by nu(s) = gamma G (gamma is the Lorentz factor, G the gyromagnetic anomaly). At 970 MeV/c, the deuteron spins coherently process at a frequency of approximate to 120 kHz in the Cooler Synchrotron COSY. The spin tune is deduced from the up-down asymmetry of deuteron-carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the order 10(-8), and to 1 x 10(-10) for a continuous 100 s accelerator cycle. This renders the presented method a new precision tool for accelerator physics; controlling the spin motion of particles to high precision is mandatory, in particular, for the measurement of electric dipole moments of charged particles in a storage ring.
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| 25. |
- Guidoboni, G., et al.
(författare)
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How to Reach a Thousand-Second in-Plane Polarization Lifetime with 0.97-GeV/c Deuterons in a Storage Ring
- 2016
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 117:5
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Tidskriftsartikel (refereegranskat)abstract
- We observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10(-29) e cm.
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| 26. |
- Grubb, Anders, et al.
(författare)
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Synthesis of cysteine proteinase inhibitors structurally based on the proteinase interacting N-terminal region of human cystatin C
- 1990
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Ingår i: Biological Chemistry Hoppe-Seyler. - 0177-3593. ; 371:Suppl., s. 137-144
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Tidskriftsartikel (refereegranskat)abstract
- Peptides spanning the entire, or part of, the Gly4-Glu21 segment of the human cysteine proteinase inhibitor cystatin C have been synthesized. Peptides containing residues on the N-terminal side of Gly11 were rapidly cleaved by papain at the bond Gly11-Gly12 whereas a peptide starting at residue Gly11 was not, thus demonstrating 1. that the N-terminal segment of cystatin C has an amino acid sequence that would allow rapid interaction between this segment and the substrate pocket of papain and, if this interaction takes place, that 2. the cystatin C residue Gly11 would be in the P1 position, and 3. the major interaction would be between residues Arg8-Val10 and the papain substrate pocket subsites S4, S3 and S2, respectively. Several modified peptide derivatives containing either diazomethane groups or peptide bond isosters were synthesized based on the structure of the Leu9-Gly11 segment of cystatin C and tested for their cysteine proteinase inhibiting capacity. The peptidyl derivatives, t-butyloxycarbonyl-valyl-glycyl-diazomethane and benzyloxycarbonyl-leucyl-valyl-glycyl-diazomethane irreversible inhibited the cysteine proteinases papain, bovine cathepsin B and streptococcal proteinase, but did not influence the activity of serine, aspartic or metallo-proteinases.
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| 27. |
- Hempelmann, N., et al.
(författare)
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Locking the Spin Precession in a Storage Ring
- 2017
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 119:1
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Tidskriftsartikel (refereegranskat)abstract
- This Letter reports the successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97 GeV= c bunched and polarized deuteron beam in the Cooler Synchrotron (COSY) storage ring in order to control both the precession rate (approximate to 121 kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a 1 standard deviation range of sigma= 0.21 rad. The minimum possible adjustment was 3.7 mHz out of a revolution frequency of 753 kHz, which changes the precession rate by 26 mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles.
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| 28. |
- Hempelmann, N., et al.
(författare)
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Phase measurement for driven spin oscillations in a storage ring
- 2018
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Ingår i: Physical Review Accelerators and Beams. - : American Physical Society. - 2469-9888. ; 21:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the first simultaneous measurement of the horizontal and vertical components of the polarization vector in a storage ring under the influence of a radio frequency (rf) solenoid. The experiments were performed at the Cooler Synchrotron COSY in Julich using a vector polarized, bunched 0.97 GeV/c deuteron beam. Using the new spin feedback system, we set the initial phase difference between the solenoid field and the precession of the polarization vector to a predefined value. The feedback system was then switched off, allowing the phase difference to change over time, and the solenoid was switched on to rotate the polarization vector. We observed an oscillation of the vertical polarization component and the phase difference. The oscillations can be described using an analytical model. The results of this experiment also apply to other rf devices with horizontal magnetic fields, such as Wien filters. The precise manipulation of particle spins in storage rings is a prerequisite for measuring the electric dipole moment (EDM) of charged particles.
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| 29. |
- Johansson, L, et al.
(författare)
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A peptidyl derivative structurally based on the inhibitory center of cystatin C inhibits bone resorption in vitro
- 2000
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Ingår i: Bone. - 1873-2763. ; 26:5, s. 451-459
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Tidskriftsartikel (refereegranskat)abstract
- Human cystatin C is a cysteine proteinase inhibitor belonging to the cystatin superfamily, which previously has been shown to inhibit bone resorption in bone organ culture. The aminoterminal segment, Arg8-Leu9-Val10-Gly11 (RLVG), of the single polypeptide chain of cystatin C constitutes an essential part of its inhibitory center. In the present study, the effect of benzyloxycarbonyl-Arg8-Leu9-Val10-Gly11-diazomethane (Z-RLVG-CHN2) on bone resorption in vitro was compared with the effects of cystatin C and calcitonin. Bone resorption was assessed by the release of 45Ca and 3H from mouse calvarial bones prelabeled with [45Ca]CaCl2 and [3H]-proline, respectively. Z-RLVG-CHN2 concentration-dependently inhibited the release of 45Ca and 3H in bones stimulated by parathyroid hormone (PTH), with half-maximal inhibition obtained at 1 μmol/L. The inhibitory actions of Z-RLVG-CHN2 and cystatin C were persistent, whereas action induced initially by calcitonin was lost with time. The inhibition caused by Z-RLVG-CHN2 and cystatin C on PTH-stimulated 45Ca release was observed after 6 h, whereas inhibition by calcitonin was seen already after 2 h. In contrast, the inhibitory effects of Z-RLVG-CHN2 and cystatin C, as well as that of calcitonin, on 3H release was seen already after 2 h. Z-RLVG-CHN2, in which the reactive carboxyterminal diazomethane was substituted by nonreactive groups [−OH, −NH2, or −N(CH3)2], resulted in peptidyl derivatives, which, in contrast to Z-RLVG-CHN2 and cystatin C, inhibited neither cysteine proteinases nor bone resorption. In contrast to wild-type cystatin C, recombinant human cystatin C with Gly substitutions for residues Arg8, Leu9, Val10, and Trp106, and with low or nonexistent affinity for cysteine proteinases, did not display any inhibitory effect on bone resorption. These data strongly indicate that Z-RLVG-CHN2 inhibits bone resorption in vitro by a mechanism that seems primarily to be due to an inhibition of bone matrix degradation via cysteine proteinases. The data also corroborate the hypothesis that cystatin C inhibits bone resorption by virtue of its cysteine proteinase inhibitory capacity.
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| 30. |
- Kozak, M, et al.
(författare)
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Expression of a selenomethionine derivative and preliminary crystallographic studies of human cystatin C
- 1999
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Ingår i: Acta Crystallographica. Section D: Biological Crystallography. - 1399-0047. ; 55:11, s. 1939-1942
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Tidskriftsartikel (refereegranskat)abstract
- Human cystatin C, a protein with amyloidogenic properties and a potent inhibitor of papain-like mammalian proteases, has been produced in its full-length form by recombinant techniques and crystallized in two polymorphic forms: cubic and tetragonal. A selenomethionyl derivative of the protein, obtained by Escherichia coli expression and with complete Met→Se-Met substitution confirmed by mass spectrometry, amino-acid analysis and X-ray absorption spectra, was crystallized in the cubic form. A truncated variant of the protein, lacking ten N-terminal residues, has also been crystallized. The crystals of this variant are tetragonal and, like the two polymorphs of the full-length protein, contain multiple copies of the molecule in the asymmetric unit, suggesting oligomerization of the protein.
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| 31. |
- Lerner, Ulf H, et al.
(författare)
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Cysteine proteinases in osteoclast function and recruitment
- 2004
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Ingår i: Biological Mechanisms of Tooth Movement and Craniofacial Adaptation. - Boston, Massachusetts, USA : Harvard Society for the Advancement of Orthodontics. - 0963204750 ; , s. 227-227
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 32. |
- Nilsson, M., et al.
(författare)
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Prevention of domain swapping inhibits dimerization and amyloid fibril formation of cystatin C. Use of engineered disulfide bridges, antibodies, and carboxymethylpapain to stabilize the monomeric form of cystatin C
- 2004
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 279:23, s. 24236-24245
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Tidskriftsartikel (refereegranskat)abstract
- Amyloidogenic proteins like cystatin C and prion proteins have been shown to form dimers by exchange of subdomains of the monomeric proteins. This process, called "three-dimensional domain swapping," has also been suggested to play a part in the generation of amyloid fibrils. One variant of cystatin C, L68Q cystatin C, is highly amyloidogenic, and persons carrying the corresponding gene suffer from massive cerebral amyloidosis leading to brain hemorrhage and death in early adult life. The present work describes the production of two variants of wild type and L68Q cystatin C with disulfide bridges at positions selected to inhibit domain swapping without affecting the biological function of the four cystatin C variants as cysteine protease inhibitors. The capacity of the four variant proteins to form dimers was tested and compared with that of wild type and L68Q cystatin C. In contrast to the latter two proteins, all four protein variants stabilized by disulfide bridges were resistant toward the formation of dimers. The capacity of the two stabilized variants of wild type cystatin C to form amyloid fibrils was investigated and found to be reduced by 80% compared with that of wild type cystatin C. In an effort to investigate whether exogenous agents could also suppress the formation of dimers of wild type and L68Q cystatin C, a monoclonal antibody or carboxymethylpapain, an inactivated form of a cysteine protease, was added to systems inducing dimerization of wild type and L68Q cystatin C. It was observed that catalytic amounts of both the monoclonal antibody and carboxymethylpapain could suppress dimerization.
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| 33. |
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| 34. |
- Rodziewicz-Motowidlo, S, et al.
(författare)
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Checking the conformational stability of cystatin C and its L68Q variant by molecular dynamics studies: Why is the L68Q variant amyloidogenic?
- 2006
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Ingår i: Journal of Structural Biology. - : Elsevier BV. - 1095-8657 .- 1047-8477. ; 154:1, s. 68-78
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Tidskriftsartikel (refereegranskat)abstract
- Human L68Q cystatin C is one of the known human amyloidogenic proteins. In its native state it is a monomer with alpha/beta structure. Experimental evidence suggests that L68Q variant associates into dimeric intermediates and that the dimers subsequently self-assemble to form amyloid deposits and insoluble fibrils. Details of the pathway of L68Q mutant amyloid formation are unclear; however, different experimental approaches with resolutions at molecular level have provided Some clues. Probably, the stability and flexibility of monomeric L68Q variant play essential roles in the early steps of amyloid formation; thus, it is necessary to characterize early conformational changes of L68Q cystatin C monomers. In this paper, we demonstrate the possibility that the differences between the monomeric forms of wild-type (wt) cystatin C and its L68Q variant are responsible for higher tendency of the L68Q cystatin C amyloidogenesis. We started our studies with the simulations of wt and L68Q cystatin C monomers. Nanosecond time scale molecular dynamics simulations at 308 K were performed using AMBER7.0 program, The results show that the structure of the L68Q monomer was changed, relative to the wt cystatin C structure. The results support earlier speculation that the L68Q point mutation would easily lead to dimer formation. (c) 2006 Published by Elsevier Inc.
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| 35. |
- Saleev, A., et al.
(författare)
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Spin tune mapping as a novel tool to probe the spin dynamics in storage rings
- 2017
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Ingår i: Physical Review Accelerators and Beams. - : American Physical Society. - 2469-9888. ; 20:7
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Tidskriftsartikel (refereegranskat)abstract
- Precision experiments, such as the search for electric dipole moments of charged particles using storage rings, demand for an understanding of the spin dynamics with unprecedented accuracy. The ultimate aim is to measure the electric dipole moments with a sensitivity up to 15 orders in magnitude better than the magnetic dipole moment of the stored particles. This formidable task requires an understanding of the background to the signal of the electric dipole from rotations of the spins in the spurious magnetic fields of a storage ring. One of the observables, especially sensitive to the imperfection magnetic fields in the ring is the angular orientation of stable spin axis. Up to now, the stable spin axis has never been determined experimentally, and in addition, the JEDI collaboration for the first time succeeded to quantify the background signals that stem from false rotations of the magnetic dipole moments in the horizontal and longitudinal imperfection magnetic fields of the storage ring. To this end, we developed a new method based on the spin tune response of a machine to artificially applied longitudinal magnetic fields. This novel technique, called spin tune mapping, emerges as a very powerful tool to probe the spin dynamics in storage rings. The technique was experimentally tested in 2014 using polarized deuterons stored in the cooler synchrotron COSY, and for the first time, the angular orientation of the stable spin axis at two different locations in the ring has been determined to an unprecedented accuracy of better than 2.8 mu rad.
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| 36. |
- Stachowiak, K, et al.
(författare)
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Effect of antisense peptide binding on the dimerization of human cystatin C - gel electrophoresis and molecular modeling studies
- 2004
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Ingår i: Acta Biochimica Polonica. - 0001-527X. ; 51:1, s. 153-160
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Tidskriftsartikel (refereegranskat)abstract
- Human cystatin C (HCC) shows a tendency to dimerize. This process is particularly easy in the case of the L68Q HCC mutant and might lead to formation of amyloid deposits in brain arteries of young adults. Our purpose was to find ligands of monomeric HCC that can prevent its dimerization. Eleven antisense peptide ligands of monomeric HCC were designed and synthesized. The influence of these ligands on HCC dimerization was studied using gel electrophoresis and molecular modeling methods. The results suggest that all the designed peptides interact with monomeric HCC facilitating its dimerization rather than preventing it.
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| 37. |
- Wieczerzak, Ewa, et al.
(författare)
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Azapeptides structurally based upon inhibitory sites of cystatins as potent and selective inhibitors of cysteine proteases
- 2002
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 1520-4804 .- 0022-2623. ; 45:19, s. 4202-4211
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Tidskriftsartikel (refereegranskat)abstract
- A series of azapeptides as potential inhibitors of cysteine proteases were synthesized. Their structures, based on the binding center of cystatins, contain an azaglycine residue (Agly) in place of the evolutionarily conserved glycine residue in the N-terminal part of the enzyme binding region of cystatins. Incorporation of Agly should lead to deactivation of the acyl-enzyme complex formed against nucleophilic attack by water molecules in the final step of peptide bond hydrolysis. The majority of synthesized azapeptides shows high inhibitory potency toward the investigated cysteine proteases, papain, cathepsin B, and cathepsin K. One of them, Z-Arg-Leu-Val-Agly-Ile-Val-OMe (compound 17), which contains in its sequence the amino acid residues from the N-terminal binding segment as well as the hydrophobic residues from the first binding loop of human cystatin C, proved to be a highly potent and selective inhibitor of cathepsin B. It inhibits cathepsin B with a K-i value of 0.088 nM. To investigate the influence of the structure of compound 17 for its inhibitory properties, we determined its conformation by means of NMR studies and theoretical calculations. The Z-Arg-Leu-Val-Agly fragment, covalently linked to Cys29 of cathepsin B, was also developed and modeled, in the catalytic pocket of the enzyme, through a molecular dynamics approach, to analyze ligand-protein interactions in detail. Analysis of the simulation trajectories generated using the AMBER force field provided us with atomic-level understanding of the conformational variability of this inhibitor, which is discussed in the context of other experimental and theoretical data.
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| 38. |
- Wieczerzak, E, et al.
(författare)
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Novel azapeptide inhibitors of cathepsins B and K. Structural background to increased specificity for cathepsin B
- 2005
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Ingår i: Journal of Peptide Research. - : Wiley. - 1397-002X .- 1399-3011. ; 66:S1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- We have designed and synthesized a new series of azapeptides which act as potential inhibitors of cathepsin B and/or cathepsin K. Their structures are based upon the inhibitory sites of natural cysteine protease inhibitors, cystatins. For the synthesized azapeptides, the equilibrium constants for dissociation of inhibitor-enzyme complex, K-i, were determined. Comparison of these values indicated that all of the azainhibitors act much stronger toward cathepsin B. Z-Arg-Leu-His-Agly-Ile-Val-OMe (7) proved to be approximately 500 times more potent for cathepsin B than for cathepsin K. To be able to explain the obtained experimental values we used the molecular dynamics procedures to analyze the interactions between cathepsin B and compound 7. We also determined the structure of the most potent and selective cathepsin B azainhibitor by means of NMR studies and theoretical calculations. In this report, we describe SAR studies of azapeptide inhibitors indicating the influence of the conformational flexibility of the examined compounds on inhibition of cathepsins B and K.
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| 39. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:9
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Tidskriftsartikel (refereegranskat)
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