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Author: Katterle, M. ×

Publications Search Results

Now showing 1 - 10 of 23
  • Publication
    MIP Thermistor
    ( 2013)
    Rajkumar, R.
    ;
    Athikomrattanakul, U.
    ;
    Lettau, K.
    ;
    Katterle, M.
    ;
    Danielsson, B.
    ;
    Warsinke, A.
    ;
    Gajovic-Eichelmann, N.
    ;
    Scheller, F.W.
  • Publication
    Water coordinated zinc dioxo-chlorin and porphyrin self-assemblies as chlorosomal mimics: Variability of supramolecular interactions
    ( 2012)
    Jesorka, A.
    ;
    Holzwarth, A.R.
    ;
    Eichhöfer, A.
    ;
    Reddy, C.M.
    ;
    Kinoshita, Y.
    ;
    Tamiaki, H.
    ;
    Katterle, M.
    ;
    Naubron, J.-V.
    ;
    Balaban, T.S.
    Semisynthetic zinc chlorins are shown for the first time to self-assemble in the absence of an intrinsic hydroxy group, which is always present in the chlorosomal bacteriochlorophylls (BChl's) c, d and e. Instead, the presently studied compounds have carbonyl groups. These cannot function as hydrogen bond donating groups. However due to interspacing water molecules bound to the zinc ion, double hydrogen bonding can occur to adjacent tetrapyrrolic macrocycles equipped with carbonyl recognition groups. Solution studies comprising UV-Vis absorption, electronic circular dichroism (ECD) and FT-IR show that different aggregates are formed in hydrated solvents in comparison to dry nonpolar solvents. Single crystal X-ray studies show variable supramolecular interactions either with interspacing water molecules coordinating the Zn ion within a porphyrin or with the 172 carbonyl group of a chlorin ligating the Zn ion. Our findings have implications for a minimalistic design of se lf-assembling chromophores, which can act as efficient light-harvesting units.
  • Publication
    Preparation and characterization of novel molecularly imprinted polymers based on thiourea receptors for nitrocompounds recognition
    ( 2011)
    Athikomrattanakul, U.
    ;
    Katterle, M.
    ;
    Gajovic-Eichelmann, N.
    ;
    Scheller, F.W.
    Molecularly imprinted polymers (MIPs) for the recognition of nitro derivatives are prepared from three different(thio)urea-bearing functional monomers. The binding capability of the polymers is characterized by a batch binding experiment. The imprinting factors and affinity constants (K) of the imprinted polymers exhibit the same tendency as the binding constants (K-a) of the functional monomers to the target substance in solution. Not only nitrofurantoin is efficiently bound by these MIPs but also a broad spectrum of other nitro compounds is bound with at the intermediate level, addressing that these (thio)urea-based monomers can be utilized to prepare a family of MIPs for various nitro compounds, which can be applied as recognition elements in separation and analytical application.
  • Publication
    Benzoboroxole-modified nanoparticles for the recognition of glucose at neutral pH
    ( 2011)
    Schumacher, S.
    ;
    Katterle, M.
    ;
    Hettrich, C.
    ;
    Paulke, B.-R.
    ;
    Pal, A.
    ;
    Hall, D.G.
    ;
    Scheller, F.W.
    ;
    Gajovic-Eichelmann, N.
    Benzoboroxole modified nanoparticles were prepared starting from a polystyrene-covinylbenzylchloride latex by nucleophilic substitution with 6-amino-1-hydroxy-2,1-benzoxaborolane. It is known that benzoboroxole binds to saccharides at pH 7.4 due to the intramolecular coordination of a hydroxyl group coordinating as a donor group, which compensates the electron deficiency of the boron. These benzoboroxole modified nanoparticles were tested with regard to their aqueous saccharide binding ability utilizing Alizarin Red S as a reporter dye. Consequently, the pH value was chosen to be 7.4 as the targeted key feature. It was shown that the binding of fructose as well as glucose can be determined by UV-Vis spectroscopy in a concentration range from 20 mM to 400 mM which is of clinical relevance. The binding constants determined by the analysis of competitive binding for the benzoboroxole modified nanoparticles were 2354 M-1 for fructose and 580 M-1 for glucose. Furthermore, the temperature stability up to 121 °C of these nanoparticles was tested and it could be shown that 95% of the initial binding capacity could be conserved.
  • Publication
    Label-free detection of enhanced saccharide binding at pH 7.4 to nanoparticulate benzoboroxole based receptor units
    ( 2011)
    Schumacher, S.
    ;
    Katterle, M.
    ;
    Hettrich, C.
    ;
    Paulke, B.-R.
    ;
    Hall, D.G.
    ;
    Scheller, F.W.
    ;
    Gajovic-Eichelmann, N.
    Nanoparticles modified with either 6-amino-1-hydroxy-2,1-benzoxaborolane (3-aminobenzoboroxole) or 3-aminophenylboronic acid were prepared by nucleophilic substitution of a styrene-co-DVB-co-vinylbenzylchloride latex (25 nm). Isothermal titration calorimetry (ITC) was used as a label-free detection method for the analysis of the binding between monosaccharides and these two differently derivatized nanoparticle systems at pH 7.4. Because ITC reveals, thermodynamical parameters such as the changes in enthalpy H, free energy G, and entropy S, possible explanations for the higher binding constants can be derived in terms of entropy and enthalpy changes. In case of the modified nanoparticles, the free energy of binding is dominated by the entropy term. This shows that interfacial effects, besides the intrinsic affinity, lead to a higher binding constant compared with the free ligand. The highest binding constant was found for fructose binding to the benzoboroxole modified na noparticles: Its value of 1150 M-1 is twice as high as for the free benzoboroxole and five times as high as with phenylboronic acid or 3-aminophenylboronic acid. In contrast to the binding of fructose to free boronic acids, which is an enthalpically driven process, the binding of fructose to the modified nanoparticles is dominated by the positive entropy term.
  • Publication
    Molecular imprinting of fructose using a polymerizable benzoboroxole: Effective complexation at pH 7.4
    ( 2011)
    Schumacher, S.
    ;
    Grüneberger, F.
    ;
    Katterle, M.
    ;
    Hettrich, C.
    ;
    Hall, D.G.
    ;
    Scheller, F.W.
    ;
    Gajovic-Eichelmann, N.
    Covalent molecularly imprinted polymers against d-fructose employing 5-methacrylamido-2-hydroxymethylphenylboronic acid as functional monomer and trimethylpropane trimethacrylate (TRIM) as the crosslinking agent were prepared by a conventional radical bulk polymerization (MIP-BX(Fru)). Batch binding studies for fructose in aqueous buffers containing 10% methanol revealed that the binding capability of MIP-BX(Fru) is paramount compared to a MIP prepared with vinylphenylboronic acid MIP-BA(Fru). Especially, at the biological important pH-value of 7.4 the rebinding of fructose to the MIP-BX(Fru) is with 60 nmol per mg polymer about 3.2 higher compared to the MIP-BA(Fru). A pinacol imprinted polymer was also investigated and showed in case of MIP-BX still an imprinting of 1.7 at pH 7.4 whereas MIP-BA did not show a difference. Cross-reactivity studies at pH 7.4 show the shape-selectivity of the MIP-BX(Fru) in the order of l-fructose, sorbitol, glucose and sucrose.
  • Publication
    Membrane protrusion coarsening and nanotubulation within giant unilamellar vesicles
    ( 2011)
    Wegrzyn, I.
    ;
    Jeffries, G.D.M.
    ;
    Nagel, B.
    ;
    Katterle, M.
    ;
    Gerrard, S.R.
    ;
    Brown, T.
    ;
    Orwar, O.
    ;
    Jesorka, A.
    Hydrophobic side groups on a stimuli-responsive polymer, encapsulated within a single giant unilamellar vesicle, enable membrane attachment during compartment formation at elevated temperatures. We thermally modulated the vesicle through implementation of an IR laser via an optical fiber, enabling localized directed heating. Polymer-membrane interactions were monitored using confocal imaging techniques as subsequent membrane protrusions occurred and lipid nanotubes formed in response to the polymer hydrogel contraction. These nanotubes, bridging the vesicle membrane to the contracting hydrogel, were retained on the surface of the polymer compartment, where they were transformed into smaller vesicles in a process reminiscent of cellular endocytosis. This development of a synthetic vesicle system containing a stimuli-responsive polymer could lead to a new platform for studying inter/intramembrane transport through lipid nanotubes.
  • Publication
    Ionic Topochemical Tuned Biosensor Interface
    ( 2010)
    Nagel, B.
    ;
    Gajovic-Eichelmann, N.
    ;
    Scheller, F.W.
    ;
    Katterle, M.
    Two new hydrophilic, poly(ethylene glycol) (PEG)-based redox copolymers bearing electrochemically active ferrocene (Fc) and thiol/disulfide anchoring functionalities were synthesized. These copolymers are shown to adsorb on gold surfaces causing polymeric self-assembled monolayers (pSAMs) that possess triple functions: "redox-active", "ionic-tunable", and "bio-inert". Both immobilized polymers showed redox potentials at +400 mV (Ag|AgCl), and facilitate the electrocatalytical oxidation of NADH. Additionally, interfacial architecture of the polymers is affected by an increase in Ca2+ concentration, which leads to an amplification of the electrochemical response. The electrode current, measured for NADH-oxidation, increased by 80% after addition of 10 mM Ca2+ ions. Considering the Ca2+ influence on the heterogeneous electron transfer a structural model of the immobilized polymers is proposed based on the strong chelating abilitiy of noncyclic PEG moieties.
  • Publication
    Direct electrochemistry and spectroelectrochemistry of osmium substituted horseradish peroxidase
    ( 2009)
    Loew, N.
    ;
    Wollenberger, U.
    ;
    Scheller, F.W.
    ;
    Katterle, M.
    In this contribution the substitution of the central protoporphyrin IX iron complex of horseradish peroxidase by the respective osmium porphyrin complex is described. The direct electrochemical reduction of the Os containing horseradish peroxidase (OsHRP) was achieved at ITO and modified glassy carbon electrodes and in combination with spectroscopy revealed the three redox couples (OsHRP)-H-III/(OsHRP)-H-IV, (OsHRP)-H-IV/(OsHRP)-H-V and (OsHRP)-H-V/(OsHRP)-H-VI. The midpoint potentials differ dependent on the electrode material used with E-1/2 (Os-III/IV) of -0.4 V (ITO) and -0.25 V (GC), E-1/2 (Os-IV/V) of -0.16 V (ITO) and +0.10 V (GC), and E-1/2 (Os-V/VI)of +018 V (ITO), respectively Moreover, with immobilised OsHRP the direct electrocatalytic reduction of hydrogen peroxide and tert-butyl hydroperoxide was observed. In comparison to electrodes modified with native HRP the sensitivity of the OsHRP-electrode for tert-butyl hydroperoxide is higher.
  • Publication
    Synthetic receptors for neutral nitro derivatives
    ( 2009)
    Athikomrattanakul, U.
    ;
    Promptmas, C.
    ;
    Katterle, M.
    Different arylurea-based receptors with similar Substitution pattern and one guanidine-based receptor were synthesised and Studied concerning their binding capability towards the title functional group; Specific binding Of neutral nitro groups is revealed with relatively high binding constants in DMSO ranging from 470 to 1370 M (1) for urea and 730-990 M (1) for guanidine-based binding partners.