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Katja Tönsing

Bio: Katja Tönsing is an academic researcher from Bielefeld University. The author has contributed to research in topics: Optical tweezers & Vesicle. The author has an hindex of 9, co-authored 25 publications receiving 245 citations.

Papers
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TL;DR: In this article, the authors examined the subcellular localization of the Arabidopsis (Arabidopsis thaliana) HMGB2/3 and HMGB4 proteins, revealing that, in addition to a prominent nuclear localization, they can also be detected also in the cytoplasm.
Abstract: High mobility group (HMG) proteins of the HMGB family are chromatin-associated proteins that as architectural factors are involved in the regulation of transcription and other DNA-dependent processes. HMGB proteins are generally considered nuclear proteins, although mammalian HMGB1 can also be detected in the cytoplasm and outside of cells. Plant HMGB proteins studied so far were found exclusively in the cell nucleus. Using immunofluorescence and fluorescence microscopy of HMGB proteins fused to the green fluorescent protein, we have examined the subcellular localization of the Arabidopsis (Arabidopsis thaliana) HMGB2/3 and HMGB4 proteins, revealing that, in addition to a prominent nuclear localization, they can be detected also in the cytoplasm. The nucleocytoplasmic distribution appears to depend on the cell type. By time-lapse fluorescence microscopy, it was observed that the HMGB2 and HMGB4 proteins tagged with photoactivatable green fluorescent protein can shuttle between the nucleus and the cytoplasm, while HMGB1 remains nuclear. The balance between the basic amino-terminal and the acidic carboxyl-terminal domains flanking the central HMG box DNA-binding domain critically influences the nucleocytoplasmic distribution of the HMGB proteins. Moreover, protein kinase CK2-mediated phosphorylation of the acidic tail modulates the intranuclear distribution of HMGB2. Collectively, our results show that, in contrast to other Arabidopsis HMGB proteins such as HMGB1 and HMGB5, the HMGB2/3 and HMGB4 proteins occur preferentially in the cell nucleus, but to various extents also in the cytoplasm.

38 citations

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TL;DR: Two novel variants of the intermediate filament protein desmin, encoded by the gene DES, are identified with a broad spectrum of cardiomyopathies with a striking frequency of arrhythmias and sudden cardiac deaths and model variants of codon 120 indicated that ionic interactions contribute to this filament formation defect.
Abstract: Background—The intermediate filament protein desmin is encoded by the gene DES and contributes to the mechanical stabilization of the striated muscle sarcomere and cell contacts within the cardiac ...

38 citations

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TL;DR: A versatile and high precision three-dimensional optical tweezers setup with minimal optical interference to measure small forces and manipulate single molecules in the vicinity of a weak reflective surface is introduced.
Abstract: We introduce a versatile and high precision three-dimensional optical tweezers setup with minimal optical interference to measure small forces and manipulate single molecules in the vicinity of a weak reflective surface. Our tweezers system integrates an inverted optical microscope with a single IR-laser beam that is spatially filtered in an appropriate way to allow force measurements in three dimensions with remarkably high precision when operated in backscattered light detection mode. The setup was tested by overstretching a lambda-DNA in x and z directions (perpendicular and along the optical axis), and by manipulating individual lambda-DNA molecules in the vicinity of a nanopore that allowed quantitative single molecule threading experiments with minimal optical interference.

31 citations

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TL;DR: Extent and rate of ME, compared at the same induced transmembrane voltage, were found to decrease both with increasing vesicle radius and with increasing protein concentration, suggesting that electric pore formation is induced by ionic interfacial polarization.
Abstract: The method of membrane electroporation (ME) has been used as an analytical tool to quantify the effect of membrane curvature on transient electric pore for-mation, and on the adsorption of the protein annexin V (Mr = 35,800) to the outer surface of unilamellar lipid vesicles (of radii 25 ≤ a/nm ≤ 200). Relaxation kinetic studies using optical membrane probes of the diphenylhexatriene type suggest that electric pore formation is induced by ionic interfacial polarization causing entrance of the (more polarizable) water into the lipid bilayer membrane yielding (hydrophobic and hydrophilic) pore states with a mean stationary pore radius rp=0.35 (±0.05) nm. Extent and rate of ME, compared at the same induced transmembrane voltage, were found to decrease both with increasing vesicle radius and with increasing protein concentration. This `inhibitory' effect of annexin V is apparently allosteric and saturates at about [ANT]sat = 4 µm annexin V for vesicles of a = 100 nm at 1 mm total lipid concentration, 0.13 mm total Ca2+ concentration and at T = 293 K. Data analysis in terms of Gibbs area-difference-elasticity energy suggests that the bound annexin V reduces the gradient of the lateral pressure across the membrane. At [ANT]sat, about 20% of the vesicle surface is covered by the bound protein, but it is only 0.01% of the surface of the outer lipid leaflet in which a part of the protein, perhaps the aromatic residue of the tryptophan (W 187), is inserted. Insertion leads to a denser packing of the lipid molecules in the outer membrane leaflet. As a consequence, the radius of the electropores in the remaining membrane part, not covered by annexin V decreases (rp/nm = 0.37, 0.36 and 0.27) with increasing adsorption of the protein ([ANT] = 0, 2 and 4 µm, respectively).

28 citations

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TL;DR: Binding analysis of the intercalative binding of Triostin A to lambda-DNA reveals an exponential dependence of the association constant on the applied external force as well as a decreasing binding site size.

28 citations


Cited by
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01 May 2005

2,648 citations

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TL;DR: The present state of the investigations concerning the different steps in the reversible electropermeabilization process is described and the different hypotheses, which were proposed to give a molecular description of the membrane events, are critically discussed.

552 citations

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TL;DR: This expert consensus statement provides the clinician with guidance on evaluation and management of ACM and includes clinically relevant information on genetics and disease mechanisms.

439 citations

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TL;DR: The physico-chemical theory of ME and electroporative transport in terms of time-dependent flow coefficients has been developed to such a degree that analytical expressions are available to handle curvature and ionic strength effects on ME and transport.

395 citations

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TL;DR: Frequency-domain analysis yields an insight into the dependence of the voltage inducement on the electric and geometric parameters characterizing the cell and its vicinity, and it is shown that at sufficiently high field frequencies, for a range of parameter values the voltage induced on the organelle membrane can indeed exceed the voltage inducing on the cell membrane.

289 citations