Quantitative evaluation of mechanosensing of cells on dynamically tunable hydrogels

Thin hydrogel films based on an ABA triblock copolymer gelator [where A is pH-sensitive poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) and B is biocompatible poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC)] were used as a stimulus-responsive substrate that allows fine adjustment of the mechanical environment experienced by mouse myoblast cells. The hydrogel film elasticity could be reversibly modulated by a factor of 40 via careful pH adjustment without adversely affecting cell viability. Myoblast cells exhibited pronounced stress fiber formation and flattening on increasing the hydrogel elasticity. As a new tool to evaluate the strength of cell adhesion, we combined a picosecond laser with an inverted microscope and utilized the strong shock wave created by the laser pulse to determine the critical pressure required for cell detachment. Furthermore, we demonstrate that an abrupt jump in the hydrogel elasticity can be utilized to monitor how cells adapt their morphology to changes in their mechanical environment.     

Structural,Magnetic and Catalytic Properties of a New Vacancy Ordered Perovskite Type Barium Cobaltate BaCoO2.67

A new vacancy ordered, anion deficient perovskite modification with composition of BaCoO_2.67 (Ba₃Co₃O₈□₁) has been prepared via a two-step heating process. Combined Rietveld analysis of neutron and X-ray powder diffraction data shows a novel ordering of oxygen vacancies not known before for barium cobaltates. A combination of neutron powder diffraction, magnetic measurements, and density functional theory (DFT) studies confirms G-type antiferromagnetic ordering. From impedance measurements, the electronic conductivity of the order of 10⁻⁴ S cm⁻¹ is determined. Remarkably, the bifunctional catalytic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is found to be comparable to that of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3–y, confirming that charge-ordered anion deficient non-cubic perovskites can be highly efficient catalysts.     

Insight into Signal Response of Protein Ions in Native ESI-MS from the Analysis of Model Mixtures of Covalently Linked Protein Oligomers

Native ESI-MS is increasingly used for quantitative analysis of biomolecular interactions. In such analyses, peak intensity ratios measured in mass spectra are treated as abundance ratios of the respective molecules in solution. While signal intensities of similar-size analytes, such as a protein and its complex with a small molecule, can be directly compared, significant distortions of the peak ratio due to unequal signal response of analytes impede the application of this approach for large oligomeric biomolecular complexes. We use a model system based on concatenated maltose binding protein units (MBPn, n = 1, 2, 3) to systematically study the behavior of protein mixtures in ESI-MS. The MBP concatamers differ from each other only by their mass while the chemical composition and other properties remain identical. We used native ESI-MS to analyze model mixtures of MBP oligomers, including equimolar mixtures of two proteins, as well as binary mixtures containing different fractions of the individual components. Pronounced deviation from a linear dependence of the signal intensity with concentration was observed for all binary mixtures investigated. While equimolar mixtures showed linear signal dependence at low concentrations, distinct ion suppression was observed above 20 μM. We systematically studied factors that are most often used in the literature to explain the origin of suppression effects. Implications of this effect for quantifying protein–protein binding affinity by native ESI-MS are discussed in general and demonstrated for an example of an anti-MBP antibody with its ligand, MBP.

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Detecting exposure-dependent changes of liver detoxification capacity of children in a formerly high-loaded industrial area with a 15N-labelled diagnostic tool

The effect of remediation activities in formerly high-loaded industrial areas is measured conventionally in terms of decreased toxic loads. It is more difficult to investigate the effect on physiological parameters of the people living there. A non-invasive 15N-based organ function test, the [15N]methacetin urine test, was adapted to environmental-medical purposes for the detection of small deviations from the norm-range hepatic detoxification capacity. Parallel to the measurement of region-specific external exposure (especially by tri- and tetrachloro ethylene) and of the corresponding internal load (urinary trichloro acetic acid), the hepatic mono oxygenation capacity was determined. The study cohort consisted of 35 kindergarten children who were 3.3+/-0.5 years old at the beginning of the study. They lived in a high-polluted industrial village (n = 23) and in a non-polluted control village close by (n = 12), respectively. Children living in the polluted area were exposed a 2.3 times higher load and showed detoxification capacities 6% lower than the children in the control area. Improvement of the environmental situation led to exposure data decreasing by 70%, which is also reflected in smaller internal load and improved liver detoxification of the children in the polluted area. Then, between loaded and control area the mean hepatic detoxification was no longer significantly different (0.6%). The study shows that chronic low-dose exposure can disturb a hepatic function and that thereafter the capacity is recovered quickly in children. The stable isotope-based test is suited to characterize a health effect of multicomponent exposure by bioeffect monitoring within the framework of screening and testing the remediation efficiency.     

Novel stabilization mechanism on polar surfaces: ZnO(0001)-Zn

The (1x1) terminated (0001)-Zn surface of wurtzite ZnO was investigated with scanning tunneling microscopy. The surface is characterized by the presence of nanosized islands with a size-dependent shape and triangular holes with single-height, O-terminated step edges. It is proposed that the resulting overall decrease of the surface Zn concentration stabilizes this polar surface. Ab initio calculations of test geometries predict triangularly shaped reconstructions over a wide range of oxygen and hydrogen chemical potentials. The formation of these reconstructions appears to be electrostatically driven.