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- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Grant, MA, et al.
(författare)
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The metal-free and calcium-bound structures of a gamma-carboxyglutamic acid-containing contryphan from Conus marmoreus, glacontryphan-M
- 2004
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 279:31, s. 32464-32473
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Tidskriftsartikel (refereegranskat)abstract
- Glacontryphan-M, a novel calcium-dependent inhibitor of L-type voltage-gated Ca2+ channels expressed in mouse pancreatic beta-cells, was recently isolated from the venom of the cone snail Conus marmoreus (Hansson, K., Ma, X., Eliasson, L., Czerwiec, E., Furie, B., Furie, B. C., Rorsman, P., and Stenflo, J. ( 2004) J. Biol. Chem. 278, 32453-32463). The conserved disulfide-bonded loop of the contryphan family of conotoxins including a D-Trp is present; however, unique to glacontryphan-M is a histidine within the intercysteine-loop and two gamma-carboxy-glutamic acid (Gla) residues, formed by post-translational modification of glutamic acid. The two calcium-binding Gla residues are located in a four residue N-terminal extension of this contryphan. To better understand the structural and functional significance of these residues, we have determined the structure of glacontryphan-M using two-dimensional H-1 NMR spectroscopy in the absence and presence of calcium. Comparisons of the glacontryphan-M structures reveal that calcium binding induces structural perturbations within the Gla-containing N terminus and the Cys(11)-Cys(5)-Pro(6) region of the intercysteine loop. The backbone of N-terminal residues perturbed by calcium, Gla(2) and Ser(3), moves away from the His(8) and Trp(10) aromatic rings and the alignment of the D-Trp(7) and His(8) aromatic rings with respect to the Trp(10) rings is altered. The blockage of L-type voltage-gated Ca2+ channel currents by glacontryphan-M requires calcium binding to N-terminal Gla residues, where presumably histidine and tryptophan may be accessible for interaction with the channel. The backbone Calpha conformation of the intercysteine loop of calcium-bound glacontryphan-M superimposes on known structures of contryphan-R and Vn (0.83 and 0.66 Angstrom, respectively). Taken together these data identify that glacontryphan-M possesses the canonical contryphan intercysteine loop structure, yet possesses critical determinants necessary for a calcium-induced functionally required conformation.
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| 4. |
- Kang, J, et al.
(författare)
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Total chemical synthesis and NMR characterization of the glycopeptide tx5a, a heavily post-translationally modified conotoxin, reveals that the glycan structure is alpha-D-Gal-(1 -> 3)-alpha-D-GalNAc
- 2004
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 271:23-24, s. 4939-4949
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Tidskriftsartikel (refereegranskat)abstract
- The 13-amino acid glycopeptide tx5a (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* = 6-bromotryptophan and Thr* = Gal-GalNAc-threonine), isolated from Conus textile, causes hyperactivity and spasticity when injected intracerebral ventricularly into mice. It contains nine post-translationally modified residues: four cysteine residues, two gamma-carboxyglutamic acid residues, and one residue each of 6-bromotryptophan, 4-trans-hydroxyproline and glycosylated threonine. The chemical nature of each of these has been determined with the exception of the glycan linkage pattern on threonine and the stereochemistry of the 6-bromotryptophan residue. Previous investigations have demonstrated that tx5a contains a disaccharide composed of N-acetylgalactosamine (GalNAc) and galactose (Gal), but the interresidue linkage was not characterized. We hypothesized that tx5a contained the T-antigen, beta-D-Gal-(1-->3)-alpha-D-GalNAc, one of the most common O-linked glycan structures, identified previously in another Conus glycopeptide, contalukin-G. We therefore utilized the peracetylated form of this glycan attached to Fmoc-threonine in an attempted synthesis. While the result-ing synthetic peptide (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* =6-bromotryptophan and Thr* = beta-D-Gal-(1-->3)-alpha-D-GalNAc-threonine) and the native peptide had almost identical mass spectra, a comparison of their RP-HPLC chromatograms suggested that the two forms were not identical. Two-dimensional H-1 homonuclear and C-13-H-1 heteronuclear NMR spectroscopy of native tx5a isolated from Conus textile was then used to determine that the glycan present on tx5a indeed is not the aforementioned T-antigen, but rather alpha-D-Gal-(1-->3)-alpha-D-GalNAc.
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