Visualization of Dynamic Sub-microsecond Changes in Membrane Potential

Direct observation of rapid membrane potential changes is critical to understand how complex neurological systems function. This knowledge is especially important when stimulation is achieved through an external stimulus meant to mimic a naturally occurring process. To enable exploration of this dynamic space, we developed an all-optical method for observing rapid changes in membrane potential at temporal resolutions of ～25 ns. By applying a single 600-ns electric pulse, we observed sub-microsecond, continuous membrane charging and discharging dynamics. Close agreement between the acquired results and an analytical membrane-charging model validates the utility of this technique. This tool will deepen our understanding of the role of membrane potential dynamics in the regulation of many biological and chemical processes within living systems.     

Application of green analytical chemistry to a green chemistry process: Magnetic resonance and Raman spectroscopic process monitoring of continuous ethanolic fermentation

Compact ¹H NMR and Raman spectrometers were used for real-time process monitoring of alcoholic fermentation in a continuous flow reactor. Yeast cells catalyzing the sucrose conversion were immobilized in alginate beads floating in the reactor. The spectrometers proved to be robust and could be easily attached to the reaction apparatus. As environmentally friendly analysis methods, ¹H NMR and Raman spectroscopy were selected to match the resource- and energy-saving process. Analyses took only a few seconds to minutes compared to chromatographic procedures and were, therefore, suitable for real-time control realized as a feedback loop. Both compact spectrometers were successfully implemented online. Raman spectroscopy allowed for faster spectral acquisition and higher quantitative precision, NMR yielded more resolved signals thus higher specificity. By using the software Matlab for automated data loading and processing, relevant parameters such as the ethanol, glycerol, and sugar content could be easily obtained. The subsequent multivariate data analysis using partial linear least-squares regression type 2 enabled the quantitative monitoring of all reactants within a single model in real time.     

Stabilization and scale-up of photosynthesis-driven ω-hydroxylation of nonanoic acid methyl ester by two-liquid phase whole-cell biocatalysis

Photoautotrophic organisms are promising hosts for biocatalytic oxyfunctionalizations because they supply reduction equivalents as well as O₂ via photosynthetic water oxidation. Thus far, research on photosynthesis-driven bioprocesses mainly focuses on strain development and the proof of principle in small-scale biocatalytic reaction setups. This study investigates the long-term applicability of the previously developed cyanobacterial strain Synechocystis sp. PCC 6803_BGT harboring the alkane monooxygenase system AlkBGT catalyzing terminal alkyl group oxyfunctionalization. For the regiospecific ω-hydroxylation of nonanoic acid methyl ester (NAME), this biocatalyst showed light intensity-independent hydroxylation activity and substantial hydrolysis of NAME to nonanoic acid. Substrate mass transfer limitation, substrate hydrolysis, as well as reactant toxicity were overcome via in situ substrate supply by means of a two-liquid phase system. The application of diisononyl phthalate as organic carrier solvent enabled 1.7-fold increased initial specific activities (5.6 ± 0.1 U/g_CDW) and 7.6-fold increased specific yields on biomass (3.8 ± 0.1 mmol_H-NAME/g_CDW) as compared with single aqueous phase biotransformations. Finally, the whole-cell biotransformation system was successfully scaled from glass tubes to a stirred-tank photobioreactor. This is the first study reporting the application of the two-liquid phase concept for efficient phototrophic whole-cell biocatalysis.     

Regional Activation of Myosin II in Cancer Cells Drives Tumor Progression via a Secretory Cross-Talk with the Immune Microenvironment

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Direct comparison of four methods to construct xylem vulnerability curves: Differences among techniques are linked to vessel network characteristics

During periods of dehydration, water transport through xylem conduits can become blocked by embolism formation. Xylem embolism compromises water supply to leaves and may lead to losses in productivity or plant death. Vulnerability curves (VCs) characterize plant losses in conductivity as xylem pressures decrease. VCs are widely used to characterize and predict plant water use at different levels of water availability. Several methodologies for constructing VCs exist and sometimes produce different results for the same plant material. We directly compared four VC construction methods on stems of black cottonwood (Populus trichocarpa), a model tree species: dehydration, centrifuge, X‐ray–computed microtomography (microCT), and optical. MicroCT VC was the most resistant, dehydration and centrifuge VCs were intermediate, and optical VC was the most vulnerable. Differences among VCs were not associated with how cavitation was induced but were related to how losses in conductivity were evaluated: measured hydraulically (dehydration and centrifuge) versus evaluated from visual information (microCT and optical). Understanding how and why methods differ in estimating vulnerability to xylem embolism is important for advancing knowledge in plant ecophysiology, interpreting literature data, and using accurate VCs in water flux models for predicting plant responses to drought.     

Hair Mineral and Trace Element Content in Children with Down’s Syndrome

Biological Trace Element Research - Chronic exposure to lead causes disruption to energy production mechanisms and tissue damage, in particular through its binding to thiol groups and competition...