TY - JOUR A1 - Brietzke, Thomas Martin A1 - Dietz, Thomas A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Bois, Juliana A1 - Kelm, Harald A1 - Reh, Manuel A1 - Schmitz, Markus A1 - Koerzdoerfer, Thomas A1 - Leimkühler, Silke A1 - Wollenberger, Ulla A1 - Krueger, Hans-Joerg A1 - Holdt, Hans-Jürgen T1 - The 1,6,7,12-Tetraazaperylene Bridging Ligand as an Electron Reservoir and Its Disulfonato Derivative as Redox Mediator in an Enzyme-Electrode Process JF - Chemistry - a European journal N2 - The homodinuclear ruthenium(II) complex [{Ru(l-N4Me2)}(2)(-tape)](PF6)(4) {[1](PF6)(4)} (l-N4Me2=N,N-dimethyl-2,11-diaza[3.3](2,6)-pyridinophane, tape=1,6,7,12-tetraazaperylene) can store one or two electrons in the energetically low-lying * orbital of the bridging ligand tape. The corresponding singly and doubly reduced complexes [{Ru(l-N4Me2)}(2)(-tape(.-))](PF6)(3) {[2](PF6)(3)} and [{Ru(l-N4Me2)}(2)(-tape(2-))](PF6)(2) {[3](PF6)(2)}, respectively, were electrochemically generated, successfully isolated and fully characterized by single-crystal X-ray crystallography, spectroscopic methods and magnetic susceptibility measurements. The singly reduced complex [2](PF6)(3) contains the -radical tape(.-) and the doubly reduced [3](PF6)(2) the diamagnetic dianion tape(2-) as bridging ligand, respectively. Nucleophilic aromatic substitution at the bridging tape in [1](4+) by two sulfite units gave the complex [{Ru(l-N4Me2)}(2){-tape-(SO3)(2)}](2+) ([4](2+)). Complex dication [4](2+) was exploited as a redox mediator between an anaerobic homogenous reaction solution of an enzyme system (sulfite/sulfite oxidase) and the electrode via participation of the low-energy *-orbital of the disulfonato-substituted bridging ligand tape-(SO3)(2)(2-) (E-red1=-0.1V versus Ag/AgCl/1m KCl in water). KW - electrochemistry KW - enzyme catalysis KW - N-ligands KW - redox-active ligands KW - ruthenium Y1 - 2017 U6 - https://doi.org/10.1002/chem.201703639 SN - 0947-6539 SN - 1521-3765 VL - 23 SP - 15583 EP - 15587 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kielb, Patrycja A1 - Sezer, Murat A1 - Katz, Sagie A1 - Lopez, Francesca A1 - Schulz, Christopher A1 - Gorton, Lo A1 - Ludwig, Roland A1 - Wollenberger, Ursula A1 - Zebger, Ingo A1 - Weidinger, Inez M. T1 - Spectroscopic Observation of Calcium-Induced Reorientation of Cellobiose Dehydrogenase Immobilized on Electrodes and its Effect on Electrocatalytic Activity JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - Cellobiose dehydrogenase catalyzes the oxidation of various carbohydrates and is considered as a possible anode catalyst in biofuel cells. It has been shown that the catalytic performance of this enzyme immobilized on electrodes can be increased by presence of calcium ions. To get insight into the Ca2+-induced changes in the immobilized enzyme we employ surface-enhanced vibrational (SERR and SEIRA) spectroscopy together with electrochemistry. Upon addition of Ca2+ ions electrochemical measurements show a shift of the catalytic turnover signal to more negative potentials while SERR measurements reveal an offset between the potential of heme reduction and catalytic current. Comparing SERR and SEIRA data we propose that binding of Ca2+ to the heme induces protein reorientation in a way that the electron transfer pathway of the catalytic FAD center to the electrode can bypass the heme cofactor, resulting in catalytic activity at more negative potentials. KW - cellobiose dehydrogenase KW - electron transfer KW - enzyme catalysis KW - spectroelectrochemistry KW - surface-enhanced vibrational spectroscopy Y1 - 2015 U6 - https://doi.org/10.1002/cphc.201500112 SN - 1439-4235 SN - 1439-7641 VL - 16 IS - 9 SP - 1960 EP - 1968 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Herter, Susanne A1 - McKenna, Shane M. A1 - Frazer, Andrew R. A1 - Leimkühler, Silke A1 - Carnell, Andrew J. A1 - Turner, Nicholas J. T1 - Galactose Oxidase Variants for the Oxidation of Amino Alcohols in Enzyme Cascade Synthesis JF - ChemCatChem : heterogeneous & homogeneous & bio- & nano-catalysis ; a journal of ChemPubSoc Europe N2 - The use of selected engineered galactose oxidase (GOase) variants for the oxidation of amino alcohols to aldehydes under mild conditions in aqueous systems is reported. GOase variant F-2 catalyses the regioselective oxidation of N-carbobenzyloxy (Cbz)-protected 3-amino-1,2-propanediol to the corresponding -hydroxyaldehyde which was then used in an aldolase reaction. Another variant, M3-5, was found to exhibit activity towards free and N-Cbz-protected aliphatic and aromatic amino alcohols allowing the synthesis of lactams such as 3,4-dihydronaphthalen-1(2H)-one, 2-pyrrolidone and valerolactam in one-pot tandem reactions with xanthine dehydrogenase (XDH) or aldehyde oxidase (PaoABC). KW - aldehyde oxidase KW - amino alcohols KW - cascade reactions KW - enzyme catalysis KW - lactams Y1 - 2015 U6 - https://doi.org/10.1002/cctc.201500218 SN - 1867-3880 SN - 1867-3899 VL - 7 IS - 15 SP - 2313 EP - 2317 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Sun, Zhiyong A1 - Glebe, Ulrich A1 - Charan, Himanshu A1 - Böker, Alexander A1 - Wu, Changzhu T1 - Enzyme-Polymer Conjugates as Robust Pickering Interfacial Biocatalysts for Efficient Biotransformations and One-Pot Cascade Reactions JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - Despite the rapid development of Pickering interfacial catalysis (PIC) at liquid-liquid interfaces with chemocatalysts, the use of unstable biocatalysts at emulsion interfaces remains a technical challenge. Herein, we present a Pickering interfacial biocatalysis (PIB) platform based on robust and recyclable enzyme-polymer conjugates that act as both catalytic sites and stabilizers at the interface of Pickering emulsions. The conjugates were prepared by growing poly(N-isopropylacrylamide) on a fragile enzyme, benzaldehyde lyase, under physiological conditions. The mild in situ conjugation process preserved the enzyme structure, and the conjugates were used to emulsify a water-organic two-phase system into a stable Pickering emulsion, leading to a significantly larger interfacial area and a 270-fold improvement in catalytic performance as compared to the unemulsified two-phase system. The PIB system could be reused multiple times. Conjugates of other enzymes were also fabricated and applied for cascade reactions. KW - biphasic catalysis KW - cascade reactions KW - enzyme catalysis KW - enzyme-polymer conjugates KW - Pickering interfacial catalysis Y1 - 2018 U6 - https://doi.org/10.1002/anie.201806049 SN - 1433-7851 SN - 1521-3773 VL - 57 IS - 42 SP - 13810 EP - 13814 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Bauch, Marcel A1 - Böttcher, Dominique A1 - Bornscheuer, Uwe T. A1 - Linker, Torsten T1 - Enzymatic Cleavage of Aryl Acetates JF - ChemCatChem : heterogeneous & homogeneous & bio- & nano-catalysis ; a journal of ChemPubSoc Europe N2 - Seven enzymes have been screened for the cleavage of aryl acetates. Phenyl and naphthyl acetates react with lipases and esterases, whereas the sterically demanding anthracene acetate gave a conversion only with porcine liver esterase and esterase 2 from Bacillus subtilis (BS2). These two enzymes have been employed on a preparative (0.5 mmol) scale and afforded cleavage products in 91 and 94% yields, even for anthracene acetate. Thus, this method is superior to chemical cleavage with catalytic amounts of sodium methoxide (Zemplen conditions), which gave only low conversions. Finally, regioselectivity has been achieved with an anthracene bisacetate, in which an ethyl group controls the cleavage of the first acetate. This indicates that steric interactions play a crucial role in the enzymatic cleavage of aryl acetates, which might be interesting for future applications or the development of enzyme inhibitors. KW - arenes KW - enzyme catalysis KW - regioselectivity KW - steric hindrance KW - substituent effects Y1 - 2016 U6 - https://doi.org/10.1002/cctc.201600678 SN - 1867-3880 SN - 1867-3899 VL - 8 SP - 2853 EP - 2857 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Neumann, Bettina A1 - Kielb, Patrycja A1 - Rustam, Lina A1 - Fischer, Anna A1 - Weidinger, Inez M. A1 - Wollenberger, Ulla T1 - Bioelectrocatalytic Reduction of Hydrogen Peroxide by Microperoxidase-11 Immobilized on Mesoporous Antimony-Doped Tin Oxide JF - ChemElectrChem N2 - The heme-undecapeptide microperoxidase-11 (MP-11) was immobilized on mesoporous antimony-doped tin oxide (ATO) thin-film electrodes modified with the positively charged binding promotor polydiallyldimethylammonium chloride. Surface concentrations of MP-11 of 1.5 nmol cm(-2) were sufficiently high to enable spectroelectrochemical analyses. UV/Vis spectroscopy and resonance Raman spectroscopy revealed that immobilized MP-11 adopts a six-coordinated low-spin conformation, as in solution in the presence of a polycation. Cathodic reduction of hydrogen peroxide at potentials close to +500mV versus Ag/AgCl indicates that the reaction proceeds via a Compound I-type like intermediate, analogous to natural peroxidases, and confirms mesoporous ATO as a suitable host material for adsorbing the heme-peptide in its native state. A hydrogen peroxide sensor is proposed by using the bioelectrocatalytic properties of the MP-11-modified ATO. KW - electrochemistry KW - enzyme catalysis KW - mesoporous materials KW - microperoxidase KW - spectroelectrochemistry Y1 - 2017 U6 - https://doi.org/10.1002/celc.201600776 SN - 2196-0216 VL - 4 IS - 4 SP - 913 EP - 919 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Kunz, Oliver T1 - Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C-2-symmetric building block: a strategy for the synthesis of decanolide natural products JF - Beilstein journal of organic chemistry N2 - Starting from the conveniently available ex-chiral pool building block (R,R)-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i) a site-selective cross metathesis, (ii) a highly diastereoselective extended tethered RCM to furnish a (Z,E)-configured dienyl carboxylic acid and (iii) a Ru-lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation. KW - dienes KW - enzyme catalysis KW - lactones KW - metathesis KW - natural products KW - ruthenium Y1 - 2013 U6 - https://doi.org/10.3762/bjoc.9.289 SN - 1860-5397 VL - 9 SP - 2544 EP - 2555 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt, Main ER -