TY - JOUR A1 - Keller, Julia A1 - Haase, H. A1 - Koch, Matthias T1 - Hydroxylation and dimerization of zearalenone: comparison of chemical, enzymatic and electrochemical oxidation methods JF - World Mycotoxin Journal N2 - Investigations of the metabolic pathway of mycotoxins by microsomal techniques are often laborious, causing an increasing demand for easy and rapid simulation methods. Thus, the non-microsomal oxidation technique of electrochemistry coupled online to mass spectrometry (EC/MS) was applied to simulate phase I biotransformation of the Fusarium mycotoxin zearalenone (ZEA). The obtained transformation products were identified by high resolution mass spectrometry (FT-ICR) and HPLC-MS/MS. Transformation products (TPs) from EC/MS were compared to those of other oxidative methods such as Fenton-like and Ce(IV) reactions and metabolites derived from in vitro assays (human and rat liver microsomes). Electrochemical oxidization of ZEA was achieved by applying a potential between 0 and 2,500 mV vs. Pd/H2 using a flow-through cell with a boron-doped diamond working electrode. Several mono-hydroxylated TPs were generated by EC/MS and Fenton-like reaction, which could also be found in microsomal in vitro assays. EC and Ce(IV) led to the formation of structurally different ZEA dimers and dimeric quinones probably connected over covalent biaryl C-C and C-O-C bonds. Although the dimerization of phenolic compounds is often observed in natural processes, ZEA dimers have not yet been reported. This is the first report on the formation of stable ZEA dimers and their related quinones. The tested non-microsomal methods, in particular EC/MS, could be useful in order to predict the biotransformation products of mycotoxins, even in cases where one to one simulation is not always feasible. KW - Electrochemistry KW - Zearalenone KW - Dimer PY - 2017 DO - https://doi.org/10.3920/WMJ2017.2213 SN - 1875-0710 SN - 1875-0796 VL - 10 IS - 4 SP - 297 EP - 307 PB - Wageningen Academic Publishers AN - OPUS4-43393 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liu, F. A1 - Lakey, P. S. J. A1 - Berkemeier, T. A1 - Tong, H. A1 - Kunert, A. T. A1 - Meusel, H. A1 - Cheng, Y. A1 - Su, H. A1 - Fröhlich-Nowoisky, J. A1 - Lai, S. A1 - Weller, Michael G. A1 - Shiraiwa, M. A1 - Pöschl, U. A1 - Kampf, C. J. T1 - Atmospheric protein chemistry influenced by anthropogenic air pollutants: nitration and oligomerization upon exposure to ozone and nitrogen dioxide JF - Faraday Discussions N2 - The allergenic potential of airborne proteins may be enhanced via post-translational modification induced by air pollutants like ozone (O3) and nitrogen dioxide (NO2). The molecular mechanisms and kinetics of the chemical modifications that enhance the allergenicity of proteins, however, are still not fully understood. Here, protein tyrosine nitration and oligomerization upon simultaneous exposure of O3 and NO2 were studied in coated-wall flow-tube and bulk solution experiments under varying atmospherically relevant conditions (5–200 ppb O3, 5–200 ppb NO2, 45–96% RH), using bovine serum albumin as a model protein. Generally, more tyrosine residues were found to react via the nitration pathway than via the oligomerization pathway. Depending on reaction conditions, oligomer mass fractions and nitration degrees were in the ranges of 2.5–25% and 0.5–7%, respectively. The experimental results were well reproduced by the kinetic multilayer model of aerosol surface and bulk chemistry (KM-SUB). The extent of nitration and oligomerization strongly depends on relative humidity (RH) due to moisture-induced phase transition of proteins, highlighting the importance of cloud processing conditions for accelerated protein chemistry. Dimeric and nitrated species were major products in the liquid phase, while protein oligomerization was observed to a greater extent for the solid and semi-solid phase states of proteins. Our results show that the rate of both processes was sensitive towards ambient ozone concentration but rather insensitive towards different NO2 levels. An increase of tropospheric ozone concentrations in the Anthropocene may thus promote pro-allergic protein modifications and contribute to the observed increase of allergies over the past decades. KW - Oxidation KW - Nitration KW - Cross-linking KW - Ozone KW - Nitrogen dioxide KW - Dimer KW - Air pollution KW - Diesel KW - Aeroallergens KW - Pollen KW - Tyrosine KW - Nitrotyrosine KW - BSA KW - Albumin PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-418482 DO - https://doi.org/10.1039/c7fd00005g SN - 1359-6640 VL - 200 SP - 413 EP - 427 PB - Royal Society of Chemistry CY - London AN - OPUS4-41848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liu, F. A1 - Reinmuth-Selzle, K. A1 - Lai, S. A1 - Weller, Michael G. A1 - Pöschl, U. A1 - Kampf, C. J. T1 - Simultaneous determination of nitrated and oligomerized proteins by size exclusion high-performance liquid chromatography coupled to photodiode array detection JF - Journal of Chromatography A N2 - Chemical modifications such as nitration and cross-linking may enhance the allergenic potential of proteins. The kinetics and mechanisms of the underlying chemical processes, however, are not yet well understood. Here, we present a size-exclusion chromatography/spectrophotometry method (SEC-HPLC-DAD) that allows a simultaneous detection of mono-, di-, tri-, and higher protein oligomers, as well as their individual nitration degrees (NDs). The ND results of proteins from this new method agree well with the results from an alternative well-established method, for the analysis of tetranitromethane (TNM)- and nitrogen dioxide and ozone (NO2/O3)-nitrated protein samples. Importantly, the NDs for individual oligomer fractions can be obtained from the new method, and also, we provide a proof of principle for the calculation of the concentrations for individual protein oligomer fractions by their determined NDs, which will facilitate the investigation of the kinetics and mechanism for protein tyrosine nitration and cross-linking. KW - Size exclusion chromatography KW - HPLC-DAD KW - Protein nitration degree KW - Protein oligomer analysis KW - Nitrotyrosine KW - Dimer KW - Trimer KW - Oligomer KW - Protein KW - Tetranitromethane KW - BSA KW - Albumin KW - Air pollution KW - Nitrogen oxides PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0021967317303795 DO - https://doi.org/10.1016/j.chroma.2017.03.015 SN - 0021-9673 VL - 1495 SP - 76 EP - 82 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-40304 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Felbeck, Tom A1 - Behnke, Thomas A1 - Hoffmann, Katrin A1 - Grabolle, Markus A1 - Lezhnina, M.M. A1 - Kynast, U.H. A1 - Resch-Genger, Ute T1 - Nile-red-nanoclay hybrids: Red emissive optical probes for use in aqueous dispersion JF - Langmuir N2 - Water-dispersible and (bio)functionalizable nanoclays have a considerable potential as inexpensive carriers for organic molecules like drugs and fluorophores. Aiming at simple design strategies for red-emissive optical probes for the life sciences from commercial precursors with minimum synthetic effort, we systematically studied the dye loading behavior and stability of differently functionalized laponites. Here, we present a comprehensive study of the absorption and emission properties of the red emissive hydrophobic and neutral dye Nile Red, a well-known polarity probe, which is almost insoluble and nonemissive in water. Adsorption of this probe onto disk-shaped nanoclays was studied in aqueous dispersion as function of dye concentration, in the absence and presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB) assisting dye loading, and as a function of pH. This laponite loading strategy yields strongly fluorescent nanoclay suspensions with a fluorescence quantum yield of 0.34 at low dye loading concentration. The dye concentration-, CTAB-, and pH-dependent absorption, fluorescence emission, and fluorescence excitation spectra of the Nile-Red6#8211;nanoclay suspensions suggest the formation of several Nile Red species including emissive Nile Red monomers facing a polar environment, nonemissive H-type dimers, and protonated Nile Red molecules that are also nonfluorescent. Formation of all nonemissive Nile Red species could be suppressed by modification of the laponite with CTAB. This underlines the great potential of properly modified and functionalized laponite nanodisks as platform for optical probes with drug delivery capacities, for example, for tumor and therapy imaging. Moreover, comparison of the Nile Red dimer absorption spectra with absorption spectra of previously studied Nile Red aggregates in dendrimer systems and micelles and other literature systems reveals a considerable dependence of the dimer absorption band on microenvironment polarity which has not yet been reported so far for H-type dye aggregates. KW - Nile Red KW - Dye KW - Laponite KW - Nanoclay KW - Photoluminescence KW - Fluorescence KW - Polarity probe KW - Aggregate KW - Dimer PY - 2013 UR - http://pubs.acs.org/doi/pdf/10.1021/la402165q DO - https://doi.org/10.1021/la402165q SN - 0743-7463 SN - 1520-5827 VL - 29 IS - 36 SP - 11489 EP - 11497 PB - American Chemical Society CY - Washington, DC AN - OPUS4-29017 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -