Cytotoxic Rhodium(III) and Iridium(III) Polypyridyl Complexes: Structure–Activity Relationships,Antileukemic Activity,and Apoptosis Induction

Whereas the cytostatic agents mer‐[RhX₃(DMSO)(pp)] (X=Cl, Br; pp=phen, dpq) are considerably more potent than their facial isomers, this order is reversed for the analogous kinetically more inert Ir^III polypyridyl complexes. The complexes induce specific apoptotic cell death in leukemia and lymphoma cells via the intrinsic mitochondrial pathway and cause negligible necrotic damage.

     

Generation of Rho Zero Cells: Visualization and Quantification of the mtDNA Depletion Process

Human mitochondrial DNA (mtDNA) is located in discrete DNA-protein complexes, so called nucleoids. These structures can be easily visualized in living cells by utilizing the fluorescent stain PicoGreen^®. In contrary, cells devoid of endogenous mitochondrial genomes (ρ⁰ cells) display no mitochondrial staining in the cytoplasm. A modified restriction enzyme can be targeted to mitochondria to cleave the mtDNA molecules in more than two fragments, thereby activating endogenous nucleases. By applying this novel enzymatic approach to generate mtDNA-depleted cells the destruction of mitochondrial nucleoids in cultured cells could be detected in a time course. It is clear from these experiments that mtDNA-depleted cells can be seen as early as 48 h post-transfection using the depletion system. To prove that mtDNA is degraded during this process, mtDNA of transfected cells was quantified by real-time PCR. A significant decline could be observed 24 h post-transfection. Combination of both results showed that mtDNA of transfected cells is completely degraded and, therefore, ρ⁰ cells were generated within 48 h. Thus, the application of a mitochondrially-targeted restriction endonuclease proves to be a first and fast, but essential step towards a therapy for mtDNA disorders.     

Autonomous Ultrafast Self‐Healing Hydrogels by pH‐Responsive Functional Nanofiber Gelators as Cell Matrices

The synthesis of hybrid hydrogels by pH‐controlled structural transition with exceptional rheological properties as cellular matrix is reported. “Depsi” peptide sequences are grafted onto a polypeptide backbone that undergo a pH‐induced intramolecular O–N–acyl migration at physiological conditions affording peptide nanofibers (PNFs) as supramolecular gelators. The polypeptide–PNF hydrogels are mechanically remarkably robust. They reveal exciting thixotropic behavior with immediate in situ recovery after exposure to various high strains over long periods and self‐repair of defects by instantaneous reassembly. High cytocompatibility, convenient functionalization by coassembly, and controlled enzymatic degradation but stability in 2D and 3D cell culture as demonstrated by the encapsulation of primary human umbilical vein endothelial cells and neuronal cells open many attractive opportunities for 3D tissue engineering and other biomedical applications.     

Regulating self-organized collaborative learning: the importance of homogeneous problem perception,immediacy and intensity of strategy use

Very often, university students deliberately form self-organized study groups, e.g. to study collaboratively for an upcoming exam. Yet, very little is known about what regulation problems such self-organized study groups encounter during their learning process and how they try to cope with these problems. Therefore, this study investigates how completely self-organized groups (i.e., non-guided groups outside the classroom that form without external impulse) regulate their collaborative learning process when faced with different kinds of regulation problems. More specifically, we tested the hypotheses that members of self-organized study groups are more satisfied with their group learning experience (a) the more homogeneous their problem perceptions are within their group, (b) the more they apply immediate (rather than non-immediate) strategies to remedy their regulation problems, and (c) the more frequently they apply regulation strategies. In a longitudinal study, N?=?122 students, voluntarily studying for their exams in N?=?52 groups, were asked to indicate the types of problems they experienced, the types of strategies they used to tackle those problems, and their satisfaction with their group learning experience after each of their self-organized study meetings. Hierarchical linear modeling confirmed all hypotheses. Qualitative analysis of two selected groups’ self-reported situational data provided additional insights about the mechanisms that may have contributed to the results. Our study provides important directions for future research, including the recommendation to identify the processes by which groups (a) can reach homogeneity of problem perceptions and (b) coordinate the choice of appropriate strategies within the group.

     

Singlet oxygen microscope: from phase-separated polymers to single biological cells

The lowest excited electronic state of molecular oxygen, singlet molecular oxygen (a1Deltag), is an intermediate in many chemical and biological processes. Tools and methods have been developed to create singlet-oxygen-based optical images of heterogeneous samples that range from phase-separated polymers to biological cells. Such images provide unique insight into a variety of oxygen-dependent phenomena, including the photoinitiated death of cells.     

Dielectric spectroscopy on melt processed polycarbonate—multiwalled carbon nanotube composites

Complex permittivity and related AC conductivity measurements in the frequency range between 10⁻⁴ and 10⁷ Hz are presented for composites of polycarbonate (PC) filled with different amounts of multiwalled carbon nanotubes (MWNT) varying in the range between 0.5 and 5 wt%. The composites were obtained by diluting a PC based masterbatch containing 15 wt% MWNT by melt mixing using a Micro Compounder. From DC conductivity measurements it was found that for samples processed at a mixing screw speed of 150 rpm for 5 min, the percolation occurs at a threshold concentration (p_c) between 1.0 and 1.5 wt% MWNT. For concentrations of MWNT near the percolation threshold, the processing conditions (screw speed and mixing time) were varied. The differences in the dispersion of the MWNT in the PC matrix could be detected in the complex permittivity and AC conductivity spectra, and have been explained by changes in p_c. The AC conductivity and permittivity spectra are discussed in terms of charge carrier diffusion on percolation clusters and resistor-capacitor composites.     

Erschließung eines Marmorkarstvorkommens als mitteltiefer Erdwärmesondenspeicher im Tuxertal,Tirol

Borehole heat exchangers can be economically beneficial for meeting heating and cooling demands of houses or buildings. In karst aquifers development of thermal storage and exchange systems may be problematic in terms of groundwater protection and storage design, due to possibly high groundwater velocities. The new development of the Hochstegen marble unit in the Tux Valley (Zillertal, Austria) was designed in two stages for the requested cooling and heating demands. An enhanced geothermal response test was completed using optical frequency domain reflectometry in an exploration drillhole. Additional studies focussing on local geology and hydrology were also conducted. Geothermal parameters obtained at precise depths allowed differentiating between conductive and convective heat flow and were correlated with the lithostratigraphically-conditioned karst characteristics. The borehole heat exchanger field was developed with nine 400 m deep dual U?shaped tube probes in 2013 for 1 GWh/a extraction and 400 MWh/a induction. Along with borehole geophysics and geothermal response tests, the study has provided relevant geothermal data for improving storage design and exploration.     

Ausbreitung und Vermischung geogener,kohlendioxidführender Thermalsole in oberflächennahem Grundwasser,Bad Nauheim

Anomalous high temperatures, salt contents and carbon dioxide concentrations were detected in shallow groundwater in the famous Art Deco ensemble, Sprudelhof. A carbon dioxide lifted thermal brine is discharged by ancient wells down to 180 m deep. Since 1856, the well installation had been operated without any changes and a low level of maintenance. During the last centuries, however, numerous anthropogenic interventions in the Sprudelhof’s underground led to changes of the natural brine system, as well as mixing, dilution and expansion processes in the near-surface aquifers. Recently, the thermal brine has been escaping from the well bore by uncontrolled means, contaminating the shallow underground. Corrosion of the casings has allowed the natural mixing system to reactivate. A groundwater monitoring network containing Duo-wells, allows independent samplings of the liquid and gaseous phases. Coinciding brine-groundwater mixing ratios were calculated for the two uppermost aquifers, as well as a gradient for increasing electric conductivities with depth.