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| 2. |
- Fey, Holger, et al.
(författare)
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Isolation of highly active photosystem II core complexes with a His-tagged Cyt b559 subunit from transplastomic tobacco plants
- 2008
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier BV. - 0005-2728 .- 1879-2650. ; 1777:12, s. 1501-9
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Tidskriftsartikel (refereegranskat)abstract
- Photosystem II (PSII) is a huge multi-protein-complex consisting, in higher plants and green algae, of the PS II core and the adjacent light harvesting proteins. In the study reported here, N-terminal His-tags were added to the plastome-encoded α-subunit of cytochrome b559, PsbE, in tobacco plants, thus facilitating rapid, mild purification of higher plant PSII. Biolistic chloroplast transformation was used to replace the wildtype psbE gene by His-tagged counterparts. Transgenic plants did not exhibit an obvious phenotype. However, the oxygen evolution capacity of thylakoids prepared from the mutants compared to the wildtype was reduced by 10–30% depending on the length of the His-tag, although Fv/Fm values differed only slightly. Homoplasmic F1 plants were used to isolate PSII cores complexes. The cores contained no detectable traces of LHC or PsaA/B polypeptides, but the main core subunits of PSII could be identified using immunodetection and mass spectroscopy. In addition, Psb27 and PsbS were detected. The presence of the former was presumably due to the preparation method, since PSII complexes located in the stroma are also isolated. In contrast to previous reports, PsbS was solely found as a monomer on SDS-PAGE in the PSII core complexes of tobacco.
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| 5. |
- Fischer, Hubertus, et al.
(författare)
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Reconstruction of millennial changes in dust emission, transport and regional sea ice coverage using the deep EPICA ice cores from the Atlantic and Indian Ocean sector of Antarctica
- 2007
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X. ; 260, s. 340-354
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Tidskriftsartikel (refereegranskat)abstract
- Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring inAntarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate ofchanges in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosolsource. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes inthe glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of theSouthern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of theatmospheric dust concentration changes in Antarctica, while factor 5–10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. Dust emissions, hence environmentalconditions in Patagonia, were very similar during the last two glacials and interglacials, respectively, despite 2–4 °C warmertemperatures recorded in Antarctica during the penultimate interglacial than today. 2–3 times higher sea salt fluxes found in bothice cores in the glacial compared to the Holocene are difficult to reconcile with a largely unchanged transport intensity and thedistant open ocean source. The substantial glacial enhancements in sea salt aerosol fluxes can be readily explained assuming sea iceformation as the main sea salt aerosol source with a significantly larger expansion of (summer) sea ice in the Weddell Sea than inthe Indian Ocean sector. During the penultimate interglacial, our sea salt records point to a 50% reduction of winter sea icecoverage compared to the Holocene both in the Indian and Atlantic Ocean sector of the SO. However, from 20 to 80 ka beforepresent sea salt fluxes show only very subdued millennial changes despite pronounced temperature fluctuations, likely due to thelarge distance of the sea ice salt source to our drill sites.
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- Steffensen, Jörgen Peder, et al.
(författare)
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High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years
- 2008
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 321, s. 680-684
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Tidskriftsartikel (refereegranskat)abstract
- The last two abrupt warmings at the onset of our present warm interglacial period, interrupted bythe Younger Dryas cooling event, were investigated at high temporal resolution from the NorthGreenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitationmoisture source, switched mode within 1 to 3 years over these transitions and initiated a moregradual change (over 50 years) of the Greenland air temperature, as recorded by stable waterisotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasingGreenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of theIntertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphereatmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture sourcetemperature from one year to the next.
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| 7. |
- Toenjes, Anke, et al.
(författare)
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Genetic variation in GPR133 is associated with height: genome wide association study in the self-contained population of Sorbs
- 2009
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 18:23, s. 4662-4668
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Tidskriftsartikel (refereegranskat)abstract
- Recently, associations of several common genetic variants with height have been reported in different populations. We attempted to identify further variants associated with adult height in a self-contained population (the Sorbs in Eastern Germany) as discovery set. We performed a genome wide association study (GWAS) (similar to 390 000 genetic polymorphisms, Affymetrix gene arrays) on adult height in 929 Sorbian individuals. Subsequently, the best SNPs (P < 0.001) were taken forward to a meta-analysis together with two independent cohorts [Diabetes Genetics Initiative, British 1958 Birth Cohort, (58BC, publicly available)]. Furthermore, we genotyped our best signal for replication in two additional German cohorts (Leipzig, n = 1044 and Berlin, n = 1728). In the primary Sorbian GWAS, we identified 5 loci with a P-value < 10(-5) and 455 SNPs with P-value < 0.001. In the meta-analysis on those 455 SNPs, only two variants in GPR133 (rs1569019 and rs1976930; in LD with each other) retained a P-value at or below 10(-6) and were associated with height in the three cohorts individually. Upon replication, the SNP rs1569019 showed significant effects on height in the Leipzig cohort (P = 0.004, beta = 1.166) and in 577 men of the Berlin cohort (P = 0.049, beta = 1.127) though not in women. The combined analysis of all five cohorts (n = 6,687) resulted in a P-value of 4.7 x 10(-8) (beta = 0.949). In conclusion, our GWAS suggests novel loci influencing height. In view of the robust replication in five different cohorts, we propose GPR133 to be a novel gene associated with adult height.
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| 8. |
- Traversi, Rita, et al.
(författare)
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Sulfate spikes in the deep layers of EPICA-Dome C Ice Core: Evidence of glaciological artifacts
- 2009
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:23, s. 8737-8743
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Tidskriftsartikel (refereegranskat)abstract
- A detailed ionic component record was performed on EPICA Dome C ice core (East Antarctica) to a depth of 3190 m using Ion Chromatography and Fast Ion Chromatography (FIC). At depths greater than 2800 m, the sulfate profile shows intense, sharp spikes which are not expected due to the smoothing of sulfate peaks by diffusion processes. Moreover, these spikes show an "anomalous" chemical composition (e.g., unusually low acidity, high Mg2+ concentration and high Mg2+/Ca2+ ratio). These peaks and the surrounding layers also exhibit good Mg2+ vs SO42- and Cl- vs Na+ correlations through both glacial and interglacial periods. Furthermore, the high-resolution analysis of two horizontally contiguous ice sections showed that some fraction of the impurities are characterized by a heterogeneous distribution. Altogether, these results suggest the occurrence of long-term postdepositional processes involving a rearrangement of impurities via migration in the vein network, characterized by sulfuric acidity and leading to the formation of soluble particles of magnesium sulfate salts, along with ionic association of ions in the liquid films along boundaries. This evidence should be taken into consideration when inferring information on for rapid climatic and environmental changes from ice core chemical records at great depths. At Dome C, the depth threshold was found to be 2800 m.
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