An Oil-Based Lubrication System Based on Nanoparticular TiO2 with Superior Friction and Wear Properties

Bogunovic L, Zünkeler S, Tönsing K, Anselmetti D. An Oil-Based Lubrication System Based on Nanoparticular TiO2 with Superior Friction and Wear Properties. Tribology Letters. 2015;29(2): 59.We evaluated the performance of five different commercially available nanoparticle classes as additives for an oil-based lubrication system. While the silicon dioxide particles Aerosil® 300, RY300, and R972V tended to increase wear and friction in our 100Cr6 versus cast iron disc–disc contact, Aeroxide® P 25 and especially T 805 TiO2 nanoparticles showed superior anti-wear and anti-friction properties. The underlying tribological mechanism was investigated with optical microscopy, helium ion microscopy, and X-ray photoelectron spectroscopy. Subsequently, we formulated a stable lubrication system based on the best performing T 805 particles. Here, the base oil is a highly purified paraffin oil which was supplemented with 1 wt% T 805 TiO2 particles, 1 wt% Estisol® 242 or 1 wt% oleic acid, 0.15 wt% oleylamine, and 0.15 wt% Pluronic® RPE 2520. Superior lubrication and anti-wear properties of this formulation were demonstrated in 4-h test runs with a normal force of F N = 2.5 kN and a sliding velocity of 0.15 m/s in our disc–disc contact. Wear was significantly reduced along with a nearly 12-fold reduction in the friction coefficient, compared to the base oil (μftobase=0.155vs.μftoT805≈0.01). Using 100Cr6 disc–ball contacts, we additionally analyzed the properties of our lubrication system in the border friction regime under higher loads (F N = 0.5 kN) in 2-h runs. In particular, on the discs with lower engagement ratio, chemo-tribological protective layers were built, which protected the parts very well against wear

Binding mechanism of anti-cancer chemotherapeutic drug mitoxantrone to DNA characterized by magnetic tweezers

Kreft D, Wang Y, Rattay M, Tönsing K, Anselmetti D. Binding mechanism of anti-cancer chemotherapeutic drug mitoxantrone to DNA characterized by magnetic tweezers. Journal of Nanobiotechnology. 2018;16(1): 56.Background Chemotherapeutic agents (anti-cancer drugs) are small cytostatic or cytotoxic molecules that often bind to double-stranded DNA (dsDNA) resulting in modifications of their structural and nanomechanical properties and thus interfering with the cell proliferation process. Methods We investigated the anthraquinone compound mitoxantrone that is used for treating certain cancer types like leukemia and lymphoma with magnetic tweezers as a single molecule nanosensor. In order to study the association of mitoxantrone with dsDNA, we conducted force-extension and mechanical overwinding experiments with a sensitivity of 10−14 N. Results Using this method, we were able to estimate an equilibrium constant of association Ka ≈ 1 × 105 M−1 as well as a binding site size of n ≈ 2.5 base pairs for mitoxantrone. An unwinding angle of mitoxantrone-intercalation of ϑ ≈ 16° was determined. Conclusion Moreover, we observed a complex concentration-dependent bimodal binding behavior, where mitoxantrone associates to dsDNA as an intercalator and groove binder simultaneously at low concentrations and as a mere intercalator at high concentrations

2-Photon Laser Scanning Microscopy on Native Human Cartilage

Martini J, Tönsing K, Dickob M, Anselmetti D. 2-Photon Laser Scanning Microscopy on Native Human Cartilage. In: Proceedings of SPIE - The International Society for Optical Engineering. Vol 5860. The International Society for Optical Engineering; 2005: 16-21.Native hyaline cartilage from a human knee joint was directly investigated with laser scanning microscopy via 2-photon autofluorescence excitation with no additional staining or labelling protocols in a nondestructive and sterile manner. Using a femtosecond, near-infrared (NIR) Ti:Sa laser for 2-photon excitation and a dedicated NIR long distance objective, autofluorescence imaging and measurements of the extracellular matrix (ECM) tissue with incorporated chondrocytes were possible with a penetration depth of up to 460 µm inside the sample. Via spectral autofluorescence separation these experiments allowed the discrimination of chondrocytes from the ECM and therefore an estimate of chondrocytic cell density within the cartilage tissue to approximately 0.2-2·10 7/cm³. Furthermore, a comparison of the relative autofluorescence signals between nonarthritic and arthritic cartilage tissue exhibited distinct differences in tissue morphology. As these morphological findings are in keeping with the macroscopic diagnosis, our measurement has the potential of being used in future diagnostic applications

Verfahren zur Stabilisierung eines Laserstrahls (Beam Point Stabilizer)

Anselmetti D, Sischka A, Tönsing K. Verfahren zur Stabilisierung eines Laserstrahls (Beam Point Stabilizer). 2006

Beam Point und Beam Profile Stabilizer

Anselmetti D, Sischka A, Tönsing K. Beam Point und Beam Profile Stabilizer. 2007

Fundamentals of electroporative delivery of drugs and genes

Neumann E, Kakorin S, Tönsing K. Fundamentals of electroporative delivery of drugs and genes. BIOELECTROCHEMISTRY AND BIOENERGETICS. 1999;48(1):3-16.Electrooptical and conductometrical relaxation methods have given a new insight in the molecular mechanisms of the electroporative delivery of drug-like dyes and genes (DNA) to cells and tissues. Key findings are: (1) Membrane electroporation (ME) and hence the electroporative transmembrane transport of macromolecules are facilitated by a higher curvature of the membrane as well as by a gradient of the ionic strength across charged membranes, affecting the spontaneous curvature. (2) The degree of pore formation as the primary field response increases continuously without a threshold field strength, whereas secondary phenomena, such as a dramatic increase in the membrane permeability to drug-like dyes and DNA (also called electropermeabilization), indicate threshold field strength ranges. (3) The transfer of DNA by ME requires surface adsorption and surface insertion of the permeant molecule or part of it. The diffusion coefficient for the translocation of DNA (M-r approximate to 3.5 x 10(6)) through the electroporated membrane is D-m = 6.7 x 10(-13) cm(2) s(-1) and D-m for the drug-like dye Serva Blue G (M-r approximate to 854) is D-m = 2.0 x 10(-12) cm(2) s(-1). The slow electroporative transport of both DNA and drugs across the electroporated membrane reflects highly interactive (electro-) diffusion, involving many small pores coalesced into large, but transiently occluded pores (DNA). The data on mouse B-cells and yeast cells provide directly the flow and permeability coefficients of Serva blue G and plasmid DNA at different electroporation protocols. 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. The theory presents further useful tools for the optimization of the ME techniques in biotechnology and medicine, in particular in the new field of electroporative delivery of drugs (electrochemotherapy) and of DNA transfer and gene therapy. (C) 1999 Elsevier Science S.A. All rights reserved

Membrane electroporation and electromechanical deformation of vesicles and cells

Neumann E, Kakorin S, Tönsing K. Membrane electroporation and electromechanical deformation of vesicles and cells. FARADAY DISCUSSIONS. 1998;111:111-125.Analysis of the reduced turbidity (Delta T-/T-0) and absorbance (Delta A(-)/A(0)) relaxations of unilamellar lipid vesicles, doped with the diphenylhexatrienyl - phosphatidylcholine (beta-DPH pPC) lipids in high-voltage rectangular electrical field pulses, demonstrates that the major part of the turbidity and absorbance dichroism is caused by vesicle elongation under electric Maxwell stress. The kinetics of this electrochemomechanical shape deformation (time constants 0.1 less than or equal to tau/mu s less than or equal to 3) is determined both by the entrance of water and ions into the bulk membrane phase to form local electropores, and by the faster processes of membrane stretching and smoothing of thermal undulations. Moreover, the absorbance dichroism indicates local displacements of the chromophore relative to the membrane normal in the held. The slightly slower relaxations of the chemical turbidity (Delta T+/T-0) and absorbance (Delta A(+)/A(0)) modes are both associated with the entrance of solvent into the interface membrane/medium, caused by the alignment of the dipolar lipid head groups in one of the leaflets at the pole caps of the vesicle bilayer. In addition, (Delta T+/T-0) indicates changes in vesicle shape and volume. The results for lipid vesicles provide guidelines for the analysis of electroporative deformations of biological cells

Electroporative fast pore-flickering of the annexin V-lipid surface complex, a novel gating concept for ion transport

Neumann E, Siemens PM, Tönsing K. Electroporative fast pore-flickering of the annexin V-lipid surface complex, a novel gating concept for ion transport. BIOPHYSICAL CHEMISTRY. 2000;86(2-3):203-220.In contact with lipid bilayers and Ca2+-ions, the intracellular protein human annexin V (wild-type), M-r= 35 800, forms two types of cation-selective channels for the transport of Ca2+-, K+-, Na+- and Mg2+-ions, depending on the protein concentration [AN]. Type (I) channel events are large and predominant at high values [AN] greater than or equal to (K) over bar= 5 nM at 296 K. At 50 mM Ca2+, symmetrical on both membrane sides, AN added at the cis side, the conductance is g(Ca)(I)= 22 +/- 2 pS and at symmetrical 0.1 M K+-conditions: g(K)(I) = 32 +/- 3 pS, associated with two mean open-times (1)(I)= 0.68 +/- 0.2 ms and (2)(1)= 31 +/- 2 ms. Monoclonal anti-AN antibodies added to the trans-side first increase the mean open-times and then abolish the channel activity, suggesting that type (I) channels refer to a membrane spanning protein complex, probably a trimer T, which at [AN] > K changes its membrane organization to a higher oligomer, probably to the side-by-side double-trimer T,. The smaller type (II) channel events are predominant at low [AN]less than or equal to (K) over bar and refer to the (electroporative) adsorption complex of the monomer. The conductances gi(II) for symmetrical concentrations depend non-linearly on the voltage U-m= U-ext + U-AN, where U-AN = 0.02 +/- 0.002 V is the electrostatic contribution of the Ca2+-AN complex and U-ext the externally applied voltage. There is only one mean open-time (0)(II) which is voltage-dependent according to a functional of b (.) U-m(2) where b = 113.9 +/- 15 V-2, yielding an activation Gibbs free energy of G(a) = RT (.) B (.) U-m(2). The conformational flicker probability f(i)(II) in g(i)(II) = g(i)(0)(II) (.) Gamma(i) (.) f(i)(II) is non-linearly voltage-dependent according to a functional of a (.) U-m(2). The Nernst term Gamma(i) refers to asymmetrical ion concentrations. From a = 50 V-2, independent of the ion type, we obtain f(i)(0)(II)=0.03 +/- 0.002 and the conductances for the fully open-channel states: g(Ca)(0)(II)= 69 +/- 3 pS (0.05 M Ca2+) and g(K)(0)(II)= 131 +/- 5 pS (1.2 M K+). From the electroporation term a = pi[r(p)(2)]epsilon(0)(epsilon(w)-epsilon(m))/(2 kTd) we determine the mean pore radius of the complex in its fully open state as (r) over bar(p) = 0.86 +/- 0.05 mm. The adsorbed annexin V (Ca2+) monomer appears to electrostatically facilitate the electric pore formation at the contact interface between the protein and the lipid phase. The complex rapidly flickers and thus limits the ion transport in a voltage-dependent manner. (C) 2000 Elsevier Science B.V. All rights reserved

Compact microscope-based optical tweezers system for molecular manipulation

Sischka A, Eckel R, Tönsing K, Ros R, Anselmetti D. Compact microscope-based optical tweezers system for molecular manipulation. Review of scientific instruments. 2003;74(11):4827-4831.A compact single beam optical tweezers system for force measurements and manipulation of individual double-stranded deoxyribonucleic acid (DNA) molecules was integrated into a commercial inverted optical microscope. A maximal force of 150 pN combined with a force sensitivity of less than 0.5 pN allows measurements of elastic properties of single molecules which complements and overlaps the force regime accessible with atomic force microscopy (AFM). The manipulation and measurement performance of this system was tested with individual [lambda]-DNA molecules and renders new aspects of dynamic forces phenomena with higher precision in contrast to AFM studies. An integrated liquid handling system with a fluid cell allows investigation of the force response of individual DNA molecules in the presence of DNA binding agents. Comparison of YOYO-1-, ethidium bromide intercalated DNA, and distamycin-A complexed DNA revealed accurate and reproducible differences in the force response to an external load. This opens the possibility to use it as a single molecule biosensor to investigate DNA binding agents and even to identify molecular binding mechanisms

Physik selbstständig erfahren: das teutolab-Physik an der Universität Bielefeld

Tönsing K, Göbel C, Anselmetti D. Physik selbstständig erfahren: das teutolab-Physik an der Universität Bielefeld. Naturwissenschaften im Unterricht - Physik. 2005;16(90):26-27