TY  - JOUR
A1  - Staab, Torsten E. M.
A1  - Lotter, Frank
A1  - Mühle, Uwe
A1  - Elsayed, Mohamed
A1  - Petschke, Danny
A1  - Schubert, Thomas
A1  - Ibrahim, Alaa M.
A1  - Krause-Rehberg, Reinhard
A1  - Kieback, Bernd
T1  - The decomposition process in high-purity Al-1.7 at.% Cu alloys with trace elements: preservation of quenched-in vacancies by In, Sn and Pb influencing the ​θ′formation
JF  - Journal of Materials Science
N2  - Aluminium-copper alloys of the 2xxx type receive their excellent mechanical properties by the formation of copper-rich precipitates during hardening. Size, distribution and crystal structure of the formed precipitates determine the final strength of those alloys. Adding traces of certain elements, which bind to vacancies, significantly influences the decomposition behaviour, i.e. the diffusion of the copper atoms. For high-purity ternary alloys (Al-1.7 at.% Cu-X), we investigate the interaction of copper and trace element atoms (X=In, Sn, and Pb) with quenched-in vacancies by Positron Annihilation Lifetime Spectroscopy (PALS). By employing Vickers microhardness, Differential Scanning Calorimetry (DSC) and Small Angle X-Ray Scattering (SAXS) we obtain a comprehensive picture of the decomposition process: opposite to predicted binding energies to vacancies by ab-initio calculations we find during ageing at room and elevated temperature a more retarded clustering of copper in the presence of In rather than for Sn additions, while Pb, having the highest predicted binding to vacancies, shows nearly no retarding effect compared to pure Al-Cu. If the latter would be due to a limited solubility of lead, it had to be below 2 ppm. Transmission Electron Microscopy (TEM) as imaging method complements our findings. Annealing the quenched Al-1.7 at.% Cu-X-alloys containing 100 ppm In or Sn at 150∘C leads to finely distributed θ′-precipitates on the nanoscale, since due to the trace additions the formation temperature of θ′ is lowered by more than 100∘C. According to TEM small agglomerates of trace elements (In, Sn) may support the early nucleation for the θ′-precipitates.
KW  - Aluminium-copper
KW  - alloys
KW  - trace elements
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-269103
SN  - 1573-4803
VL  - 56
IS  - 14
ER  - 
TY  - JOUR
A1  - Schmid, Rafael
A1  - Schmidt, Sonja K.
A1  - Hazur, Jonas
A1  - Detsch, Rainer
A1  - Maurer, Evelyn
A1  - Boccaccini, Aldo R.
A1  - Hauptstein, Julia
A1  - Teßmar, Jörg
A1  - Blunk, Torsten
A1  - Schrüfer, Stefan
A1  - Schubert, Dirk W.
A1  - Horch, Raymund E.
A1  - Bosserhoff, Anja K.
A1  - Arkudas, Andreas
A1  - Kengelbach-Weigand, Annika
T1  - Comparison of hydrogels for the development of well-defined 3D cancer models of breast cancer and melanoma
JF  - Cancers
N2  - Bioprinting offers the opportunity to fabricate precise 3D tumor models to study tumor pathophysiology and progression. However, the choice of the bioink used is important. In this study, cell behavior was studied in three mechanically and biologically different hydrogels (alginate, alginate dialdehyde crosslinked with gelatin (ADA–GEL), and thiol-modified hyaluronan (HA-SH crosslinked with PEGDA)) with cells from breast cancer (MDA-MB-231 and MCF-7) and melanoma (Mel Im and MV3), by analyzing survival, growth, and the amount of metabolically active, living cells via WST-8 labeling. Material characteristics were analyzed by dynamic mechanical analysis. Cell lines revealed significantly increased cell numbers in low-percentage alginate and HA-SH from day 1 to 14, while only Mel Im also revealed an increase in ADA–GEL. MCF-7 showed a preference for 1% alginate. Melanoma cells tended to proliferate better in ADA–GEL and HA-SH than mammary carcinoma cells. In 1% alginate, breast cancer cells showed equally good proliferation compared to melanoma cell lines. A smaller area was colonized in high-percentage alginate-based hydrogels. Moreover, 3% alginate was the stiffest material, and 2.5% ADA–GEL was the softest material. The other hydrogels were in the same range in between. Therefore, cellular responses were not only stiffness-dependent. With 1% alginate and HA-SH, we identified matrices that enable proliferation of all tested tumor cell lines while maintaining expected tumor heterogeneity. By adapting hydrogels, differences could be accentuated. This opens up the possibility of understanding and analyzing tumor heterogeneity by biofabrication.
KW  - breast cancer
KW  - melanoma
KW  - biofabrication
KW  - hydrogel
KW  - tumor heterogeneity
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-211195
SN  - 2072-6694
VL  - 12
IS  - 8
ER  - 
TY  - JOUR
A1  - Esken, Jens
A1  - Goris, Tobias
A1  - Gadkari, Jennifer
A1  - Bischler, Thorsten
A1  - Förstner, Konrad U.
A1  - Sharma, Cynthia M.
A1  - Diekert, Gabriele
A1  - Schubert, Torsten
T1  - Tetrachloroethene respiration in Sulfurospirillum species is regulated by a two‐component system as unraveled by comparative genomics, transcriptomics, and regulator binding studies
JF  - MicrobiologyOpen
N2  - Energy conservation via organohalide respiration (OHR) in dehalogenating Sulfurospirillum species is an inducible process. However, the gene products involved in tetrachloroethene (PCE) sensing and signal transduction have not been unambiguously identified. Here, genome sequencing of Sulfurospirillum strains defective in PCE respiration and comparative genomics, which included the PCE‐respiring representatives of the genus, uncovered the genetic inactivation of a two‐component system (TCS) in the OHR gene region of the natural mutants. The assumption that the TCS gene products serve as a PCE sensor that initiates gene transcription was supported by the constitutive low‐level expression of the TCS operon in fumarate‐adapted cells of Sulfurospirillum multivorans. Via RNA sequencing, eight transcriptional units were identified in the OHR gene region, which includes the TCS operon, the PCE reductive dehalogenase operon, the gene cluster for norcobamide biosynthesis, and putative accessory genes with unknown functions. The OmpR‐family response regulator (RR) encoded in the TCS operon was functionally characterized by promoter‐binding assays. The RR bound a cis‐regulatory element that contained a consensus sequence of a direct repeat (CTATW) separated by 17 bp. Its location either overlapping the −35 box or 50 bp further upstream indicated different regulatory mechanisms. Sequence variations in the regulator binding sites identified in the OHR gene region were in accordance with differences in the transcript levels of the respective gene clusters forming the PCE regulon. The results indicate the presence of a fine‐tuned regulatory network controlling PCE metabolism in dehalogenating Sulfurospirillum species, a group of metabolically versatile organohalide‐respiring bacteria.
KW  - genomics
KW  - organohalide respiration
KW  - RNA sequencing
KW  - tetrachloroethene
KW  - transcriptomics
KW  - two‐component system
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225754
VL  - 9
IS  - 12
ER  -