TY - GEN A1 - Walter, Tim A1 - Collenburg, Lena A1 - Japtok, Lukasz A1 - Kleuser, Burkhard A1 - Schneider-Schaulies, Sibylle A1 - Müller, Nora A1 - Becam, Jerome A1 - Schubert-Unkmeir, Alexandra A1 - Kong, Ji Na A1 - Bieberich, Erhard A1 - Seibel, Jürgen T1 - Incorporation and visualization of azido-functionalized N-oleoyl serinol in Jurkat cells, mouse brain astrocytes, 3T3 fibroblasts and human brain microvascular endothelial cells N2 - The synthesis and biological evaluation of azido-N-oleoyl serinol is reported. It mimicks biofunctional lipid ceramides and has shown to be capable of click reactions for cell membrane imaging in Jurkat and human brain microvascular endothelial cells. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 324 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394960 ER - TY - JOUR A1 - Collenburg, Lena A1 - Walter, Tim A1 - Burgert, Anne A1 - Mueller, Nora A1 - Seibel, Juergen A1 - Japtok, Lukasz A1 - Kleuser, Burkhard A1 - Sauer, Markus A1 - Schneider-Schaulies, Sibylle T1 - A Functionalized Sphingolipid Analogue for Studying Redistribution during Activation in Living T Cells JF - The journal of immunology N2 - Sphingolipids are major components of the plasma membrane. In particular, ceramide serves as an essential building hub for complex sphingolipids, but also as an organizer of membrane domains segregating receptors and signalosomes. Sphingomyelin breakdown as a result of sphingomyelinase activation after ligation of a variety of receptors is the predominant source of ceramides released at the plasma membrane. This especially applies to T lymphocytes where formation of ceramide-enriched membrane microdomains modulates TCR signaling. Because ceramide release and redistribution occur very rapidly in response to receptor ligation, novel tools to further study these processes in living T cells are urgently needed. To meet this demand, we synthesized nontoxic, azido-functionalized ceramides allowing for bio-orthogonal click-reactions to fluorescently label incorporated ceramides, and thus investigate formation of ceramide-enriched domains. Azido-functionalized C-6-ceramides were incorporated into and localized within plasma membrane microdomains and proximal vesicles in T cells. They segregated into clusters after TCR, and especially CD28 ligation, indicating efficient sorting into plasma membrane domains associated with T cell activation; this was abolished upon sphingomyelinase inhibition. Importantly, T cell activation was not abrogated upon incorporation of the compound, which was efficiently excluded from the immune synapse center as has previously been seen in Ab-based studies using fixed cells. Therefore, the functionalized ceramides are novel, highly potent tools to study the subcellular redistribution of ceramides in the course of T cell activation. Moreover, they will certainly also be generally applicable to studies addressing rapid stimulation-mediated ceramide release in living cells. Y1 - 2016 U6 - https://doi.org/10.4049/jimmunol.1502447 SN - 0022-1767 SN - 1550-6606 VL - 196 SP - 3951 EP - 3962 PB - American Assoc. of Immunologists CY - Bethesda ER - TY - JOUR A1 - Klose, Tim A1 - Guillemoteau, Julien A1 - Vignoli, Giulio A1 - Walter, Judith A1 - Herrmann, Andreas A1 - Tronicke, Jens T1 - Structurally constrained inversion by means of a Minimum Gradient Support regularizer BT - examples of FD-EMI data inversion constrained by GPR reflection data JF - Geophysical journal international N2 - Many geophysical inverse problems are known to be ill-posed and, thus, requiring some kind of regularization in order to provide a unique and stable solution. A possible approach to overcome the inversion ill-posedness consists in constraining the position of the model interfaces. For a grid-based parameterization, such a structurally constrained inversion can be implemented by adopting the usual smooth regularization scheme in which the local weight of the regularization is reduced where an interface is expected. By doing so, sharp contrasts are promoted at interface locations while standard smoothness constraints keep affecting the other regions of the model. In this work, we present a structurally constrained approach and test it on the inversion of frequency-domain electromagnetic induction (FD-EMI) data using a regularization approach based on the Minimum Gradient Support stabilizer, which is capable to promote sharp transitions everywhere in the model, i.e., also in areas where no structural a prioriinformation is available. Using 1D and 2D synthetic data examples, we compare the proposed approach to a structurally constrained smooth inversion as well as to more standard (i.e., not structurally constrained) smooth and sharp inversions. Our results demonstrate that the proposed approach helps in finding a better and more reliable reconstruction of the subsurface electrical conductivity distribution, including its structural characteristics. Furthermore, we demonstrate that it allows to promote sharp parameter variations in areas where no structural information are available. Lastly, we apply our structurally constrained scheme to FD-EMI field data collected at a field site in Eastern Germany to image the thickness of peat deposits along two selected profiles. In this field example, we use collocated constant offset ground-penetrating radar (GPR) data to derive structural a priori information to constrain the inversion of the FD-EMI data. The results of this case study demonstrate the effectiveness and flexibility of the proposed approach. KW - Controlled source electromagnetics (CSEM) KW - Inverse theory KW - Electrical properties KW - Ground penetrating radar KW - Frequency Domain Electromagnetics KW - Inversion Y1 - 2023 U6 - https://doi.org/10.1093/gji/ggad041 SN - 0956-540X SN - 1365-246X VL - 233 IS - 3 SP - 1938 EP - 1949 PB - Oxford Univ. Press CY - Oxford ER -