TY - JOUR A1 - Göbel, Gero A1 - Dietz, T. A1 - Lisdat, Fred T1 - Biosensor based on an oxygen reducing bilirubin oxidase electrode JF - Procedia Chemistry N2 - An oxygen reducing electrode made of bilirubin oxidase and multi-walled carbon nanotubes (BOD-MWCNT-Au electrode) is coupled to enzymes catalysing oxygen-consuming reactions such as glucose oxidase (GOD) to result in a membrane-free bienzyme electrode. The feasibility of such a molecularly assembled system stabilized by covalent linkage has been demonstrated. The electrochemical characterisation of the bienzyme electrode reveals sensitivity to the enzyme substrate. The results indicate that the BOD-electrode provides a suitable platform for sensing analytes for which oxidases of high activity are available. KW - bienzyme sensor KW - bilirubin oxidase KW - carbon nanotube KW - membran-free KW - mediator-less Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-6237 SN - 1876-6196 VL - 1 IS - 1 SP - 273 EP - 276 ER - TY - GEN A1 - Boyadzhiev, Marin A1 - Langenstraßen, Rainer A1 - Evtimova, Rozeta A1 - Nenkova, Sanchi A1 - Behrendt, Gerhard T1 - Development of Branched Aromatic Polyester Polyols from PET T2 - Wissenschaftliche Beiträge 2007 N2 - Diese Arbeit befasst sich mit einer neuen Klasse verzweigter aromatischer Polyesterpolyole (APP), die auf PET-Abfällen basieren und für die Herstellung hochwertiger Polyurethane entwickelt wurden. Dieses Ziel wurde durch eine modifizierte Umesterung von PET durch eine Glykolmischung mit einem geringen Anteil Triolen erreicht. Es wurde eine Reihe verzweigter APP mit Hydroxylzahlen im Bereich von 260 bis 380 mg KOH/g und Hydroxyl-Funktionalitäten zwischen 2,00 und 2,30 erhalten. Die Viskosität der Produkte steigt im Bereich der Funktionalität von 2,03 bis 2,12 geringfügig und darüber stärker an. Für jede Reihe der APP mit Hydroxylzahlen von 260, 320 bzw. 380 mg KOH/g wurde bezüglich der Viskosität, der Langzeitstabilität und der Hydroxyl-Funktionalität ein Eigenschaftsoptimum gefunden. APP mit höherer Hydroxyl-Funktionalität können zur Herstellung von Polyurethan-Gießharzen und jene mit niedrigeren Hydroxylzahlen für Beschichtungen, z. B. von Leder, verwendet werden. N2 - This paper is directed to the development of a new type of branched aromatic polyester polyols (APP) based on PET wastes designed to produce high quality polyurethanes (PUR). To this end, a modifi ed transesterification of PET by a glycol mixture was used and simultaneously small amounts of triols were incorporated into the reaction mixture. By this method, a series of branched APP’s with hydroxyl numbers in the range of 260 to 380 mg KOH/g and hydroxyl functionalities between 2.00 and 2.30 was received. The viscosity of the products increased slowly with the functionality in the range of 2.03 to 2.12 and sharper beyond this value. An optimum of properties was found in each series of APP with hydroxyl numbers of 260, 320, and 380 mg KOH/g, resp. with respect of viscosity, long term stability and hydroxyl functionality. APP with a higher hydroxyl functionality are useful to produce cast polyurethane resins, those with lower hydroxyl numbers for coatings, e. g. of leather. KW - Aromatische Polyesterpolyole KW - PET-Abfall KW - APP Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus-389 SN - 0949-8214 VL - 12 SP - 11 EP - 16 ER - TY - JOUR A1 - Dimitrov, Kiril A1 - Herzog, Michael A1 - Nenkova, Sanchi T1 - Fe3O4 Modification of Microcrystalline Cellulose for Composite Materials JF - American Journal of Chemistry N2 - A new synthesis method for producing cellulose ferrite micro- and nano- composites was developed and new material properties were studied. Microcrystalline cellulose was modified with a mixture of Fe+2/Fe+3 to produce surface bonded nanoparticles magnetite (Fe3O4). Optimal conditions were determined. Microsized hematite (Fe2O3) was mixed with microcrystalline cellulose and used as a reference. The magnetite modified microcrystalline cellulose and hematite filled microcrystalline cellulose were used together with polyurethane prepolymer. New composite crosslinked conductivity materials based on the magnetite modified microcrystalline or hematite filled microcrystalline cellulose and polyurethane were developed. Morphology, crystalline properties, water absorption and electro conductivity of these materials were characterized. The physical properties of these materials were characterized by different analytical methods: SEM, XRD, water absorption and electrical resistance. KW - microcrystalline cellulose KW - magnetite KW - SEM KW - XRD Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9651 SN - 2165-8781 VL - 3 IS - 5 SP - 140 EP - 147 ER - TY - JOUR A1 - Feifel, Sven Christian A1 - Stieger, Kai Ralf A1 - Kapp, Andreas A1 - Weber, Dennis A1 - Allegrozzi, Marco A1 - Piccioli, Mario A1 - Turano, Paola A1 - Lisdat, Fred T1 - Insights into Interprotein Electron Transfer of Human Cytochrome c Variants Arranged in Multilayer Architectures by Means of an Artificial Silica Nanoparticle Matrix JF - ACS Omega N2 - The redox behavior of proteins plays a crucial part in the design of bioelectronic systems. We have demonstrated several functional systems exploiting the electron exchange properties of the redox protein cytochrome c (cyt c) in combination with enzymes and photoactive proteins. The operation is based on an effective reaction at modified electrodes but also to a large extent on the capability of self-exchange between cyt c molecules in a surface-fixed state. In this context, different variants of human cyt c have been examined here with respect to an altered heterogeneous electron transfer (ET) rate in a monolayer on electrodes as well as an enhanced self-exchange rate while being incorporated in multilayer architectures. For this purpose, mutants of the wild-type (WT) protein have been prepared to change the chemical nature of the surface contact area near the heme edge. The structural integrity of the variants has been verified by NMR and UV–vis measurements. It is shown that the single-point mutations can significantly influence the heterogeneous ET rate at thiol-modified gold electrodes and that electroactive protein/silica nanoparticle multilayers can be constructed with all forms of human cyt c prepared. The kinetic behavior of electron exchange for the mutant proteins in comparison with that of the WT has been found altered in some multilayer arrangements. Higher self-exchange rates have been found for K79A. The results demonstrate that the position of the introduced change in the charge situation of cyt c has a profound influence on the exchange behavior. In addition, the behavior of the cyt c variants in assembled multilayers is found to be rather similar to the situation of cyt c self-exchange in solution verified by NMR. Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-6753 SN - 2470-1343 VL - 1 IS - 6 SP - 1058 EP - 1066 ER - TY - JOUR A1 - Rangelova, Nadezhda A1 - Radev, Lachezar A1 - Nenkova, Sanchi A1 - Salvado, Isabel Miranda A1 - Vas Fernandes, Maria A1 - Herzog, Michael T1 - Methylcellulose/SiO2 hybrids: sol-gel preparation and characterization by XRD, FTIR and AFM JF - Central European Journal of Chemistry N2 - Methylcellulose (MC) / SiO2 organic / inorganic hybrid materials have been prepared from MC and methyltriethoxysilane or ethyltrimethoxysilane, and characterized by XRD, FTIR and AFM. XRD showed peak shifts. FTIR shows intermolecular hydrogen bonding between MC and SiO2. AFM depicts surface roughness which depends on the silica precursor and MC content. Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9636 SN - 2391-5420 VL - 9 IS - 1 SP - 112 EP - 118 ER - TY - JOUR A1 - Lobstein, Susanne A1 - Zinn, Steffen A1 - Minieri, Marilena A1 - Foitzik, Andreas T1 - Sample Analysis for Novel Medical Applications JF - Materials Science Forum N2 - The sample preparation for biological and chemical probes involves following a strict workflow to eliminate any contamination to the sample beforehand. Furthermore, it is time consuming and must be carried out by trained personnel such as a nurse or other supervisors, making it therefore expensive. The development of novel sample preparation techniques paired with modern sample analysis systems is focused on improving the operability while keeping a constant quality of results. This is important to analyse samples, which cannot be determined with current screening conditions. The analysis of analytes is required to receive a more detailed picture of the patient and to fully understand its complexity. Possible samples for in-depth analysis of chemical origin can be cholesterol or glucose. More complex samples, such as blood or saliva, require a sophisticated system, which analyses the samples for their individual compounds. Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18749 SN - 0255-5476 SN - 1662-9752 VL - 941 SP - 2518 EP - 2521 PB - Trans Tech Publications ER - TY - JOUR A1 - Tsonev, Tsvetomir A1 - Herzog, Michael A1 - Nenkova, Sanchi T1 - Shape memory polyurethanes based on recycled polyvinyl butyral. I. Synthesis and morphology JF - Central European Journal of Chemistry N2 - Shape memory polyurethanes (SMPUs) were synthesized by 4,4′-diphenylmethane diisocyanate (MDI), hexane-1,6-diol (HD), polypropylene glycol (PPG), and recycled polyvinyl butyral (PVB). Dynamic mechanical analysis, differential scanning calorimetry and Fourier transformation infrared attenuated total reflection spectroscopy was used to characterize the poly (vinylbutyral-urethanes). Micro-phase domain separation of hard and soft segments and phase inversion were investigated. Increasing the hard segment content, i.e., average hard segment molecular weight, leads to an increase in the degree of micro-phase separation, hard domain order and crystallinity. The crystalline hard segment structures combined with the elastic nature of soft segment matrix provide enough physical and chemical crosslinks to have shape memory effect. Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9664 SN - 2391-5420 VL - 11 IS - 12 SP - 2058 EP - 2065 ER - TY - CHAP A1 - Tolkiehn, Günter-Ulrich A1 - Rabe, P. A1 - Werner, A. ED - Garner, C.D. ED - Hasnain, S.S. T1 - Structure investigation on the hexacyanoferrate-(II) and -(III) complexes T2 - EXAFS for inorganic systems : Proceedings of the Daresbury Study Weekend March 1981 N2 - The contribution reports a structure investigation on the hexacyanoferrate-(II) and (III) complexes in solid state and in aqueous solution using EXAFS. Results are discussed and compared with other published data. KW - EXAFS KW - structure KW - bond-length KW - hexacyanoferrate Y1 - 1981 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-7218 SP - 130 EP - 132 PB - Science and Engineering Research Council CY - Daresbury, England ER - TY - JOUR A1 - Wegerich, F. A1 - Turano, Paola A1 - Allegrozzi, Marco A1 - Möhwald, H. A1 - Lisdat, Fred T1 - Superoxide Biosensing with Engineered Cytochrome c JF - Procedia Chemistry N2 - Several mutation positions have been chosen for introducing positively charged lysines in human cytochrome c (cyt c) with the aim of increasing the reaction rate with superoxide radicals (SO) and thus, the sensitivity of an electrochemical cyt c based SO biosensor. The impact of the mutations on structural and redox properties as well as on the reaction rate with SO are verified. Four mutants show a higher reaction rate with the radical compared to the wild type. These mutants are used for the construction of SO sensors based on thiol-modified gold electrodes and covalently fixed proteins. The E66K mutant electrode has a clearly higher sensitivity in comparison to the wildtype based sensor. KW - biosensor KW - cytochrome c KW - superoxide KW - protein engineering Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-6523 SN - 1876-6196 VL - 1 IS - 1 SP - 1287 EP - 1290 ER - TY - GEN A1 - Alow, Jewgeni M. A1 - Gerassimowa, Nina P. A1 - Korikow, Pjotr W. A1 - Moskwitschjow, Juri A. A1 - Noshnin, Nikolai A. A1 - Paschinin, Alexej N. T1 - Synthese neuer organischer Schwefelverbindungen aus aromatischen Thiolverbindungen und Sulphinsäuren T2 - Wissenschaftliche Beiträge 2001 N2 - Die rasche Entwicklung der Chemie organischer Schwefelverbindungen in der zweiten Hälfte des 20. Jahrhunderts wurde durch drei wichtige Prozesse ausgelöst: - die Einbeziehung von schwefelhaltigen und stark schwefelhaltigen Erdölen sowie die Verwendung von schwefelhaltigen Abfällen zur Steigerung der Produktion, die durch die Entwicklung anderer Industriebranchen notwendig wurde; - die Erweiterung der Anwendungsbereiche von organischen Schwefelverbindungen bei der Produktion von Arzneimitteln, Pestiziden, Flotationsmitteln, Zusatzstoffen für Öle und Heizstoffe, Inhibitoren gegen Metallkorrosion, Polymerisationsreglern, Farbstoffen u. a.; - durch das große Interesse an organischen Schwefelverbindungen als Modelle für die Erforschung vieler wichtiger Grundlagenkonzeptionen in der organischen Chemie. Aus diesem Grunde ist die Synthese neuer organischer Schwefelverbindungen mit potenziell nützlichen Eigenschaften sowie die Untersuchung der Gesetzmäßigkeiten des Reaktionsverlaufs mit dem Ziel, diese Prozesse bewusst zu steuern, von besonderer Aktualität. In der vorliegenden Arbeit wurden Reaktionen der nukleophilen Addition von aromatischen Thiolverbindungen und Sulfinsäuren an aktivierte Doppelbindungen (Vinylketone und Akrylnitrile) und die weitere Umwandlung der entstandenen Addukte zu heterozyklischen Verbindungen untersucht. Y1 - 2001 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-8318 SN - 0949-8214 VL - 6 SP - 11 EP - 15 ER -