@article{DraudeKoersgenPelsteretal.2015,
  author    = {Draude, Felix and K{\"o}rsgen, Martin and Pelster, Andreas and Schwerdtle, Tanja and M{\"u}thing, Johannes and Arlinghaus, Heinrich F.},
  title     = {Characterization of freeze-fractured epithelial plasma membranes on nanometer scale with ToF-SIMS},
  series = {Analytical \& bioanalytical chemistry},
  volume    = {407},
  journal   = {Analytical \& bioanalytical chemistry},
  number    = {8},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {1618-2642},
  doi       = {10.1007/s00216-014-8334-2},
  pages     = {2203 -- 2211},
  year      = {2015},
  abstract  = {Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to characterize the freeze-fracturing process of human epithelial PANC-1 and UROtsa cells. For this purpose, phosphatidylcholine, sphingomyelin, phosphatidylethanolamine, and phosphatidylserine standard samples were investigated to find specific signals with both high specificity and signal intensity. The results were used to investigate single cells of subconfluent cell layers prepared with a special silicon wafer sandwich preparation technique. This freeze-fracturing technique strips cell membranes off the cells, isolating them on opposing silicon wafer substrates. Criteria were found for defining regions with stripped off cell membranes and, on the opposing wafer, complementary regions with the remaining cells. Measured ethanolamine/choline and serine/choline ratios in these regions clearly showed that in the freeze-fracturing process, the lipid bilayer of the plasma membrane is split along its central zone. Accordingly, only the outer lipid monolayer is stripped off the cell, while the inner lipid monolayer remains attached to the cell on the opposing wafer, thus allowing detailed analysis of a single lipid monolayer. Furthermore, it could be shown that using different washing procedures did not influence the transmembrane lipid distribution. Under optimized preparation conditions, it became feasible to detect lipids with a lateral resolution of approximately 100 nm. The data indicate that ToF-SIMS would be a very useful technique to study with very high lateral resolution changes in lipid composition caused, for example, by lipid storage diseases or pharmaceuticals that interfere with the lipid metabolism.},
  language  = {en}
}
@article{RomeroVianaKienelSachse2012,
  author    = {Romero-Viana, Lidia and Kienel, Ulrike and Sachse, Dirk},
  title     = {Lipid biomarker signatures in a hypersaline lake on Isabel Island (Eastern Pacific) as a proxy for past rainfall anomaly (1942-2006 AD)},
  series = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences},
  volume    = {350},
  journal   = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences},
  number    = {18},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0031-0182},
  doi       = {10.1016/j.palaeo.2012.06.011},
  pages     = {49 -- 61},
  year      = {2012},
  abstract  = {Isabel Lake is a hypersaline crater-lake on Isabel Island, Mexico, situated in the eastern tropical Pacific, an area highly sensitive to hydrological changes. Today, annual rainfall mostly occurs during the wet season, from June to October, when the northern edge of the Intertropical Convergence Zone (ITCZ) extends over the island. In order to evaluate the potential of sedimentary lipid biomarker signatures as a proxy of past hydro-climatic variability we have performed a calibration analysis comparing changes in biomarker distribution in the upper 16 cm of the sediment core with a regional instrumental data set. Annual laminations present in the sediment sequence allow for precise chronological control (1942-2006), More than 80 different lipid compounds were identified in the sediment and could be assigned to three major groups of source organisms: (1) algal populations; (2) a mixed community of ciliates, bacteria and cyanobacteria; and (3) photosynthetic sulfur bacteria. We found that the observed changes in the. relative contribution of the different lipid biomarkers to the sediment record were determined by the regional rainfall variability over the last 65 years. The planktonic community of Isabel Lake was highly sensitive to salinity fluctuations related to rainfall variability; seasonal precipitation results in freshwater input into the lake, driving an annual algal bloom and a relative decrease in the abundance of the more halotolerant populations of (cyano) bacteria and ciliates. Consequently, the concentration ratio between the two most abundant biomarkers in the Isabel Lake sediments, n-alkyl diols and tetrahymanol (which we define as the DiTe index), representing algal and ciliate planktonic populations, respectively, was significantly correlated with the seasonal rainfall anomaly (r = 0.68, p < 0.01). We propose that the DiTe index is a proxy of changes in the aquatic ecosystem of Isabel Lake and, by extension, regional hydrological changes in a sensitive climatic area of the eastern tropical Pacific.},
  language  = {en}
}