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Chtcheglova L.A.,Center for Advanced Bioanalysis | Hinterdorfer P.,Center for Advanced Bioanalysis | Hinterdorfer P.,Johannes Kepler University
Journal of Molecular Recognition | Year: 2011

Determining the landscape of specific binding sites on biological samples with high spatial accuracy (in the order of several nanometres) is an important task in many fields of biological science. During the past five years, dynamic recognition imaging (e.g. simultaneous topography and recognition (TREC) imaging) has proven to be a powerful technique in biophysical research. This technique becomes an indispensable tool for high-resolution receptor mapping as it has been successfully demonstrated on different biomolecular model systems. In these studies, the topographical imaging of receptor molecules is combined with molecular recognition by their cognate ligands bound to the atomic force microscope (AFM) tip via a flexible and distensible tether. In this review, we describe the principles of TREC imaging and provide a flavour of its recent application on endothelial cells. © 2011 John Wiley & Sons, Ltd.

Neundlinger I.,Johannes Kepler University | Poturnayova A.,Slovak Academy of Sciences | Karpisova I.,Comenius University | Rankl C.,Agilent Technologies | And 6 more authors.
Biophysical Journal | Year: 2011

Thrombin aptamer binding strength and stability is dependent on sterical parameters when used for atomic force microscopy sensing applications. Sterical improvements on the linker chemistry were developed for high-affinity binding. For this we applied single molecule force spectroscopy using two enhanced biotinylated thrombin aptamers, BFF and BFA immobilized on the atomic force microscopy tip via streptavidin. BFF is a dimer composed of two single-stranded aptamers (aptabody) connected to each other by a complementary sequence close to the biotinylated end. In contrast, BFA consists of a single DNA strand and a complementary strand in the supporting biotinylated part. By varying the pulling velocity in force-distance cycles the formed thrombin-aptamer complexes were ruptured at different force loadings allowing determination of the energy landscape. As a result, BFA aptamer showed a higher binding force at the investigated loading rates and a significantly lower dissociation rate constant, k off, compared to BFF. Moreover, the potential of the aptabody BFF to form a bivalent complex could clearly be demonstrated. © 2011 Biophysical Society.

Mahut M.,University of Vienna | Haller E.,University of Vienna | Ghazidezfuli P.,University of Vienna | Leitner M.,Johannes Kepler University | And 6 more authors.
Angewandte Chemie - International Edition | Year: 2012

Recognizing pDNA supercoils: Differently supercoiled species of the same plasmid DNA can be separated by topology-selective chromatography. Two-dimensional HPLC proved that the supercoiling changes during fermentation. Thus, a new quality criterium might help to optimize the effectivity of future genetic drugs and vaccines. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oh Y.J.,Johannes Kepler University | Sekot G.,University of Vienna | Sekot G.,Austrian Center of Industrial Biotechnology | Duman M.,Johannes Kepler University | And 6 more authors.
Journal of Molecular Recognition | Year: 2013

Tannerella forsythia is among the most potent triggers of periodontal diseases, and approaches to understand underlying mechanisms are currently intensively pursued. A ~22-nm-thick, 2D crystalline surface (S-) layer that completely covers Tannerella forsythia cells is crucially involved in the bacterium-host cross-talk. The S-layer is composed of two intercalating glycoproteins (TfsA-GP, TfsB-GP) that are aligned into a periodic lattice. To characterize this unique S-layer structure at the nanometer scale directly on intact T. forsythia cells, three complementary methods, i.e., small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and single-molecular force spectroscopy (SMFS), were applied. SAXS served as a difference method using signals from wild-type and S-layer-deficient cells for data evaluation, revealing two possible models for the assembly of the glycoproteins. Direct high-resolution imaging of the outer surface of T. forsythia wild-type cells by AFM revealed a p4 structure with a lattice constant of ~9.0 nm. In contrast, on mutant cells, no periodic lattice could be visualized. Additionally, SMFS was used to probe specific interaction forces between an anti-TfsA antibody coupled to the AFM tip and the S-layer as present on T. forsythia wild-type and mutant cells, displaying TfsA-GP alone. Unbinding forces between the antibody and wild-type cells were greater than with mutant cells. This indicated that the TfsA-GP is not so strongly attached to the mutant cell surface when the co-assembling TfsB-GP is missing. Altogether, the data gained from SAXS, AFM, and SMFS confirm the current model of the S-layer architecture with two intercalating S-layer glycoproteins and TfsA-GP being mainly outwardly oriented. © 2013 John Wiley & Sons, Ltd.

Oh Y.J.,Johannes Kepler University | Hubauer-Brenner M.,Center for Advanced Bioanalysis | Hinterdorfer P.,Johannes Kepler University | Hinterdorfer P.,Center for Advanced Bioanalysis
Journal of Nanoscience and Nanotechnology | Year: 2015

In this study, the physical properties of transition metal oxide surfaces were examined using scanning probe microscopic (SPM) techniques for elucidating the antimicrobial activity of molybdenum trioxide (MoO3), tungsten trioxide (WO3), and zinc oxide (ZnO) embedded into the polymers thermoplastic polyurethane (TPU) and polypropylene (PP). We utilized atomic force microscopy (AFM) in the contact imaging mode and its derivative single-pass Kelvin probe force microscopy for investigating samples that were presumably identical in their compositions, but showed different antimicrobial activity in bacterial adhesion tests. Our results revealed that surfaces with larger roughness and higher surface potential variation showed stronger antimicrobial activities compared to smoother and homogeneously charge-distributed surfaces. In addition, capacitance gradient (dC/dZ) measurements were performed to elucidate the antimicrobial activity arising from the different dielectric behavior of the transition metal oxides in this heterogeneous polymer surface. We found that the nano-scale exposure of transition metal oxides on polymer surfaces provided strong antimicrobial effects. Applications arising from our studies will be useful for public and healthcare environments. Copyright © 2015 American Scientific Publishers All rights reserved.

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