TY  - JOUR
A1  - Atilaw, Yoseph
A1  - Heydenreich, Matthias
A1  - Ndakala, Albert
A1  - Akala, Hoseah M.
A1  - Kamau, Edwin
A1  - Yenesew, Abiy
T1  - 3-Oxo-14 alpha, 15 alpha-epoxyschizozygine: A new schizozygane indoline alkaloid from Schizozygia coffaeoides
JF  - Phytochemistry letters
N2  - The stem bark extract of Schizozygia coffaeoides (Apocynaceae) showed moderate antiplasmodial activity (IC50 = 8-12 mu g/mL) against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the isolation of a new schizozygane indoline alkaloid, named 3-oxo-14 alpha, 15 alpha-epoxyschizozygine. In addition, two dimeric anthraquinones, cassiamin A and cassiamin B, were identified for the first time in the family Apocynaceae. The structures of the isolated compounds were deduced on the basis of spectroscopic evidence. The schizozygane indole alkaloids showed good to moderate antiplasmodial activities (IC50 = 13-52 mu m). (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.
KW  - Schizozygia coffaeoides
KW  - Schizozygane indoline alkaloid
KW  - 3-Oxo-14 alpha, 15 alpha-epoxyschizozygine
KW  - Dimeric anthraquinone
KW  - Cassiamin A
KW  - Cassiamin B
Y1  - 2014
U6  - https://doi.org/10.1016/j.phytol.2014.07.003
SN  - 1874-3900
SN  - 1876-7486
VL  - 10
SP  - 28
EP  - 31
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Sarauli, David
A1  - Peters, Kristina
A1  - Xu, Chenggang
A1  - Schulz, Burkhard
A1  - Fattakhova-Rohlfing, Dina
A1  - Lisdat, Fred
T1  - 3D-Electrode architectures for enhanced direct bioelectrocatalysis of pyrroloquinoline quinone-dependent glucose dehydrogenase
JF  - ACS applied materials & interfaces
N2  - We report on the fabrication of a complex electrode architecture for efficient direct bioelectrocatalysis. In the developed procedure, the redox enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase entrapped in a sulfonated polyaniline [poly(2-methoxyaniline-5-sulfonic acid)-co-aniline] was immobilized on macroporous indium tin oxide (macroITO) electrodes. The use of the 3D-conducting scaffold with a large surface area in combination with the conductive polymer enables immobilization of large amounts of enzyme and its efficient communication with the electrode, leading to enhanced direct bioelectrocatalysis. In the presence of glucose, the fabricated bioelectrodes show an exceptionally high direct bioelectrocatalytical response without any additional mediator. The catalytic current is increased more than 200-fold compared to planar ITO electrodes. Together with a high long-term stability (the current response is maintained for >90% of the initial value even after 2 weeks of storage), the transparent 3D macroITO structure with a conductive polymer represents a valuable basis for the construction of highly efficient bioelectronic units, which are useful as indicators for processes liberating glucose and allowing optical and electrochemical transduction.
KW  - 3D electrode structures
KW  - macroITO
KW  - conductive polymer
KW  - PQQ-GDH
KW  - direct bioelectrocatalysis
KW  - bioelectrochemistry
Y1  - 2014
U6  - https://doi.org/10.1021/am5046026
SN  - 1944-8244
VL  - 6
IS  - 20
SP  - 17887
EP  - 17893
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Derese, Solomon
A1  - Barasa, Leonard
A1  - Akala, Hoseah M.
A1  - Yusuf, Amir O.
A1  - Kamau, Edwin
A1  - Heydenreich, Matthias
A1  - Yenesew, Abiy
T1  - 4 '-Prenyloxyderrone from the stem bark of Millettia oblata ssp  teitensis and the antiplasmodial activities of isoflavones from some Millettia species
JF  - Phytochemistry letters
N2  - The CH2Cl2/MeOH (1: 1) extract of the stem bark of Millettia oblata ssp. teitensis showed antiplasmodial activity (IC50 = 10-12 mu g/mL) against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the isolation of a new isoflavone, 4'-prenyloxyderrone (1), together with known isoflavones (8-O-methylretusin, durmillone, maximaisoflavone B, maximaisoflavone H and maximaisoflavone J), a rotenoid (tephrosin) and a triterpene (lupeol). Similar investigation of Millettia leucantha resulted in the identification of the isoflavones afrormosin and wistin, and the flavone chrysin. The identification of these compounds was based on their spectroscopic data. Five of the isoflavones isolated from these plants as well as 11 previously reported compounds from Millettia dura were tested and showed good to moderate antiplasmodial activities (IC50 = 13-53 mu M), with the new compound, 4'-prenyloxyderrone, being the most active (IC50 = 13-15 mu M).
KW  - Millettia oblata ssp teitensis
KW  - Millettia leucantha
KW  - Millettia dura;
Y1  - 2014
U6  - https://doi.org/10.1016/j.phytol.2014.02.001
SN  - 1874-3900
SN  - 1876-7486
VL  - 8
SP  - 69
EP  - 72
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Muiva-Mutisya, Lois
A1  - Macharia, Bernard
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Akala, Hoseah M.
A1  - Derese, Solomon
A1  - Omosa, Leonidah K.
A1  - Yusuf, Amir O.
A1  - Kamau, Edwin
A1  - Yenesew, Abiy
T1  - 6 alpha-Hydroxy-alpha-toxicarol and (+)-tephrodin with antiplasmodial activities from Tephrosia species
JF  - Phytochemistry letters
N2  - The CH2Cl2/MeOH (1: 1) extract of the roots of Tephrosia villosa showed good antiplasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC50 values of 3.1 +/- 0.4 and 1.3 +/- 0.3 mu g/mL, respectively. Chromatographic separation of the extract yielded a new rotenoid, 6 alpha-hydroxy-alpha-toxicarol, along with five known rotenoids, (rotenone, deguelin, sumatrol, 12 alpha-hydroxy-alpha-toxicarol and villosinol). Similar treatment of the extract of the stem of Tephrosia purpurea (IC50 = 4.1 +/- 0.4 and 1.9 +/- 0.2 mu g/mL against D6 and W2 strains of P. falciparum, respectively) yielded a new flavone having a unique substituent at C-7/C-8 [trivial name (+)-tephrodin], along with the known flavonoids tachrosin, obovatin methyl ether and derrone. The relative configuration and the most stable conformation in (+)-tephrodin was determined by NMR and theoretical energy calculations. The rotenoids and flavones tested showed good to moderate antiplasmodial activities (IC50 = 9 +/- 23 mu M). Whereas the cytotoxicity of rotenoids is known, the flavones (+)-tephrodin and tachrosin did not show significant cytotoxicity (IC50 > 100 mu M;) against mammalian African monkey kidney (vero) and human larynx carcinoma (HEp2) cell lines. (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.
KW  - Tephrosia villosa
KW  - Tephrosia purpurea
KW  - 6 alpha-Hydroxy-alpha-toxicarol
KW  - (+)-Tephrodin
KW  - Plasmodium falciparum
Y1  - 2014
U6  - https://doi.org/10.1016/j.phytol.2014.09.002
SN  - 1874-3900
SN  - 1876-7486
VL  - 10
SP  - 179
EP  - 183
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Salffner, Katharina
A1  - Boehm, Michael
A1  - Reich, Oliver
A1  - Löhmannsröben, Hans-Gerd
T1  - A broadband cavity ring-down spectrometer based on an incoherent near infrared light source
JF  - Applied physics : B, Lasers and optics
Y1  - 2014
U6  - https://doi.org/10.1007/s00340-014-5762-9
SN  - 0946-2171
SN  - 1432-0649
VL  - 116
IS  - 4
SP  - 785
EP  - 792
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Meyners, Christian
A1  - Wawrzinek, Robert
A1  - Kraemer, Andreas
A1  - Hinz, Steffen
A1  - Wessig, Pablo
A1  - Meyer-Almes, Franz-Josef
T1  - A fluorescence lifetime-based binding assay for acetylpolyamine amidohydrolases from Pseudomonas aeruginosa using a [1,3]dioxolo[4,5-f][1,3]benzodioxole (DBD) ligand probe
JF  - Analytical & bioanalytical chemistry
N2  - High-throughput assays for drug screening applications have to fulfill particular specifications. Besides the capability to identify even compounds with low potency, one of the major issues is to minimize the number of false-positive hits in a screening campaign in order to reduce the logistic effort for the subsequent cherry picking and confirmation procedure. In this respect, fluorescence lifetime (FLT) appears as an ideal readout parameter that is supposed to be robust against autofluorescent and light-absorbing compounds, the most common source of systematic false positives. The extraordinary fluorescence features of the recently discovered [1,3]dioxolo[4,5-f][1,3]benzodioxole dyes were exploited to develop an FLT-based binding assay with exceptionally robust readout. The assay setup was comprehensively validated and shown to comply not only with all requirements for a powerful high-throughput screening assay but also to be suitable to determine accurate binding constants for inhibitors against enzymes of the histone deacetylase family. Using the described binding assay, the first inhibitors against three members of this enzyme family from Pseudomonas aeruginosa were identified. The compounds were characterized in terms of potency and selectivity profile. The novel ligand probe should also be applicable to other homologues of the histone deacetylase family that are inhibited by N-hydroxy-N'-phenyloctandiamide.
KW  - Histone deacetylases
KW  - Acetylpolyamine amidohydrolases
KW  - Fluorescence life time
KW  - Binding assay
KW  - Pseudomonas aeruginosa
Y1  - 2014
U6  - https://doi.org/10.1007/s00216-014-7886-5
SN  - 1618-2642
SN  - 1618-2650
VL  - 406
IS  - 20
SP  - 4889
EP  - 4897
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - GEN
A1  - Sarauli, David
A1  - Xu, Chenggang
A1  - Dietzel, Birgit
A1  - Schulz, Burkhard
A1  - Lisdat, Fred
T1  - A multilayered sulfonated polyaniline network with entrapped pyrroloquinoline quinone-dependent glucose dehydrogenase
BT  - tunable direct bioelectrocatalysis
N2  - A feasible approach to construct multilayer films of sulfonated polyanilines – PMSA1 and PABMSA1 – containing different ratios of aniline, 2-methoxyaniline-5-sulfonic acid (MAS) and 3-aminobenzoic acid (AB), with the entrapped redox enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) on Au and ITO electrode surfaces, is described. The formation of layers has been followed and confirmed by electrochemical impedance spectroscopy (EIS), which demonstrates that the multilayer assembly can be achieved in a progressive and uniform manner. The gold and ITO electrodes subsequently modified with PMSA1:PQQ-GDH and PABMSA1 films are studied by cyclic voltammetry (CV) and UV-Vis spectroscopy which show a significant direct bioelectrocatalytical response to the oxidation of the substrate glucose without any additional mediator. This response correlates linearly with the number of deposited layers. Furthermore, the constructed polymer/enzyme multilayer system exhibits a rather good long-term stability, since the catalytic current response is maintained for more than 60% of the initial value even after two weeks of storage. This verifies that a productive interaction of the enzyme embedded in the film of substituted polyaniline can be used as a basis for the construction of bioelectronic units, which are useful as indicators for processes liberating glucose and allowing optical and electrochemical transduction.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 275 
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98744
ER  - 
TY  - JOUR
A1  - Sarauli, David
A1  - Xu, Chenggang
A1  - Dietzel, Birgit
A1  - Schulz, Burkhard
A1  - Lisdat, Fred
T1  - A multilayered sulfonated polyaniline network with entrapped pyrroloquinoline quinone-dependent glucose dehydrogenase: tunable direct bioelectrocatalysis
JF  - Journal of materials chemistry : B, Materials for biology and medicine
N2  - A feasible approach to construct multilayer films of sulfonated polyanilines - PMSA1 and PABMSA1 containing different ratios of aniline, 2-methoxyaniline-5-sulfonic acid (MAS) and 3-aminobenzoic acid (AB), with the entrapped redox enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) on Au and ITO electrode surfaces, is described. The formation of layers has been followed and confirmed by electrochemical impedance spectroscopy (EIS), which demonstrates that the multilayer assembly can be achieved in a progressive and uniform manner. The gold and ITO electrodes subsequently modified with PMSA1:PQQ-GDH and PABMSA1 films are studied by cyclic voltammetry (CV) and UV-Vis spectroscopy which show a significant direct bioelectrocatalytical response to the oxidation of the substrate glucose without any additional mediator. This response correlates linearly with the number of deposited layers. Furthermore, the constructed polymer/enzyme multilayer system exhibits a rather good long-term stability, since the catalytic current response is maintained for more than 60% of the initial value even after two weeks of storage. This verifies that a productive interaction of the enzyme embedded in the film of substituted polyaniline can be used as a basis for the construction of bioelectronic units, which are useful as indicators for processes liberating glucose and allowing optical and electrochemical transduction.
Y1  - 2014
U6  - https://doi.org/10.1039/c4tb00336e
SN  - 2050-750X
SN  - 2050-7518
VL  - 2
IS  - 21
SP  - 3196
EP  - 3203
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - THES
A1  - Giordano, Cristina
T1  - A neglected world: transition metal nitride and metal carbide based nanostructures
T1  - Eine vernachlässigte Welt: Übergangsmetallnitrid- und Metallcarbid-basierte Nanostrukturen
BT  - novel synthesis and future perspectives
BT  - neuartige Synthese und Zukunftsperspektiven
N2  - Potentiality of nanosized materials has been largely proved but a closer look shows that a significant percentage of this research is related to oxides and metals, while the number drastically drops for metallic ceramics, namely transition metal nitrides and metal carbides. The lack of related publications do not reflect their potential but rather the difficulties related to their synthesis as dense and defect-free structures, fundamental prerequisites for advanced mechanical applications. 
The present habilitation work aims to close the gap between preparation and processing, indicating novel synthetic pathways for a simpler and sustainable synthesis of transition metal nitride (MN) and carbide (MC) based nanostructures and easier processing thereafter. In spite of simplicity and reliability, the designed synthetic processes allow the production of functional materials, with the demanded size and morphology. 
The goal was achieved exploiting classical and less-classical precursors, ranging from common metal salts and molecules (e.g. urea, gelatin, agar, etc), to more exotic materials, such as leafs, filter paper and even wood. It was found that the choice of precursors and reaction conditions makes it possible to control chemical composition (going for instance from metal oxides to metal oxy-nitrides to metal nitrides, or from metal nitrides to metal carbides, up to quaternary systems), size (from 5 to 50 nm) and morphology (going from mere spherical nanoparticles to rod-like shapes, fibers, layers, meso-porous and hierarchical structures, etc). The nature of the mixed precursors also allows the preparation of metal nitrides/carbides based nanocomposites, thus leading to multifunctional materials (e.g. MN/MC@C, MN/MC@PILs, etc) but also allowing dispersion in liquid media. Control over composition, size and morphology is obtained with simple adjustment of the main route, but also coupling it with processes such as electrospin, aerosol spray, bio-templating, etc. Last but not least, the nature of the precursor materials also allows easy processing, including printing, coating, casting, film and thin layers preparation, etc). 
The designed routes are, concept-wise, similar and they all start by building up a secondary metal ion-N/C precursor network, which converts, upon heat treatment, into an intermediate “glass”. This glass stabilizes the nascent nanoparticles during their nucleation and impairs their uncontrolled growth during the heat treatment (scheme 1). This way, one of the main problems related to the synthesis of MN/MC, i.e. the need of very high temperature, could also be overcome (from up to 2000°C, for classical synthesis, down to 700°C in the present cases). The designed synthetic pathways are also conceived to allow usage of non-toxic compounds and to minimize (or even avoid) post-synthesis purification, still bringing to phase pure and well-defined (crystalline) nanoparticles.
This research aids to simplify the preparation of MN/MC, making these systems now readily available in suitable amounts both for fundamental and applied science. The prepared systems have been tested (in some cases for the first time) in many different fields, e.g. battery (MnN0.43@C shown a capacity stabilized at a value of 230 mAh/g, with coulombic efficiencies close to 100%), as alternative magnetic materials (Fe3C nanoparticles were prepared with different size and therefore different magnetic behavior, superparamagnetic or ferromagnetic, showing a saturation magnetization value up to 130 emu/g, i.e. similar to the value expected for the bulk material), as filters and for the degradation of organic dyes (outmatching the performance of carbon), as catalysts (both as active phase but also as active support, leading to high turnover rate and, more interesting, to tunable selectivity). Furthermore, with this route, it was possible to prepare for the first time, to the best of our knowledge, well-defined and crystalline MnN0.43, Fe3C and Zn1.7GeN1.8O nanoparticles via bottom-up approaches. 
Once the synthesis of these materials can be made straightforward, any further modification, combination, manipulation, is in principle possible and new systems can be purposely conceived (e.g. hybrids, nanocomposites, ferrofluids, etc).
N2  - Materialien sind wichtige Hilfsmittel, die wir täglich benutzen, um unser Leben einfacher zu machen. Materialien werden durch ihre Eigenschaften charakterisiert. Manche sind stark, manche sind elektrisch, manche magnetisch, usw. Wenn ein Stoff auf die Dimension eines Virus verkleinert wird, zeigen sich besondere Veränderungen. War das Material groß z.B. elektrisch, hat es klein diese Eigenschaft nicht mehr. Groß war es glanzlos, aber klein ist es transparent... Das heißt, dass jedes bekannte Material prinzipiell ein neues Material werden kann, nur durch die Veränderung seiner Größe. Wegen dieser besonderen Entdeckung, ist seit vielen Jahren ein Großteil der Forschung Nanopartikeln gewidmet. Dennoch werden in diesem Gebiet meistens besondere Materialien untersucht, weil ihre Anwendungsfelder weithin bekannt und wichtig sind. Meine Forschung basiert auf der Untersuchung neuer oder weniger bekannter Materialien, nämlich Übergangsmetallnitride und Übergangsmetallcarbide als Nanostrukturen. Sie sind nicht so bekannt, weil sie nicht so einfach herzustellen waren (die klassische Synthese braucht eine hohe Temperatur bis 2000°C, und oft toxische Reaktionsmittel). Trotzdem sind sie sehr interessante Materialien, weil sie auf der Grenze zwischen reinen Metallen und reinen keramischen Materialien hinsichtlich der Eigenschaften liegen. Das heißt, sie sind z.B. sehr fest, aber auch leitend, sie haben einen hohen Schmelzpunkt und sind magnetisch, etc. Durch die hier vorgestellte Forschung wird die Synthese dieser Materialien einfacher gemacht, bei niedrigen Temperaturen, mit natürlichen Produkten (z.B. Harnstoff, Gelatine, Agar, Zellulose, etc). Die Eigenschaften und Anwendungsmöglichkeiten dieser Systeme wurden auch studiert, ebenso wie die Kontrolle der Größe und Form. So konnten wir sphärische, rohrförmige, und fiber-basierte Nanostrukturen synthetisieren, aber sogar Blätter und Holz konnten als Reaktionsmittel benutzt werden und in Nitrid und Carbid umgewandelt werden, ohne die Form zu ändern. Weil die Synthese dieser Materialien direkt gemacht werden konnte, ist prinzipiell jede weitere Modifikation, Kombination und Manipulation möglich. So können jetzt neue Systeme entworfen werden.
KW  - metal carbides
KW  - metal nitrides
KW  - nanostructures
KW  - sol-gel
KW  - Metallnitride
KW  - Metallcarbide
KW  - Nanostrukturen
KW  - Sol-Gel
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-75375
ER  - 
TY  - JOUR
A1  - Füchsel, Gernot
A1  - Tremblay, Jean Christophe
A1  - Saalfrank, Peter
T1  - A six-dimensional potential energy surface for Ru(0001)(2x2):CO
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - We present a new global ground state potential energy surface (PES) for carbon monoxide at a coverage of 1/4, on a rigid Ru(0001) surface [Ru(0001)(2x2):CO]. All six adsorbate degrees of freedom are considered. For constructing the PES, we make use of more than 90 000 points calculated with periodic density functional theory using the RPBE exchange-correlation functional and an empirical van der Waals correction. These points are used for interpolation, utilizing a symmetry-adapted corrugation reducing procedure (CRP). Three different interpolation schemes with increasing accuracy have been realized, giving rise to three flavours of the CRP PES. The CRP PES yields in agreement with the DFT reference and experiments, the atop position of CO to be the most stable adsorption geometry, for the most accurate interpolation with an adsorption energy of 1.69 eV. The CRP PES shows that diffusion parallel to the surface is hindered by a barrier of 430 meV, and that dissociation is facilitated but still activated. As a first "real" application and further test of the new potential, the six-dimensional vibrational Schrodinger equation is solved variationally to arrive at fully coupled, anharmonic frequencies and vibrational wavefunctions for the vibrating, adsorbed CO molecule. Good agreement with experiment is found also here. Being analytical, the new PES opens an efficient way towards multidimensional dynamics. (C) 2014 AIP Publishing LLC.
Y1  - 2014
U6  - https://doi.org/10.1063/1.4894083
SN  - 0021-9606
SN  - 1089-7690
VL  - 141
IS  - 9
PB  - American Institute of Physics
CY  - Melville
ER  -