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- ItemPH-Responsive Biohybrid Carrier Material for Phenol Decontamination in Wastewater(Columbus, Ohio : American Chemical Soc., 2018) Pretscher, Martin; Pineda-Contreras, Beatriz A.; Kaiser, Patrick; Reich, Steffen; Schöbel, Judith; Kuttner, Christian; Freitag, Ruth; Fery, Andreas; Schmalz, Holger; Agarwal, SeemaSmart polymers are a valuable platform to protect and control the activity of biological agents over a wide range of conditions, such as low pH, by proper encapsulation. Such conditions are present in olive oil mill wastewater with phenol as one of the most problematic constituents. We show that elastic and pH-responsive diblock copolymer fibers are a suitable carrier for Corynebacterium glutamicum, i.e., bacteria which are known for their ability to degrade phenol. Free C. glutamicum does not survive low pH conditions and fails to degrade phenol at low pH conditions. Our tea-bag like biohybrid system, where the pH-responsive diblock copolymer acts as a protecting outer shell for the embedded bacteria, allows phenol degradation even at low pH. Utilizing a two-step encapsulation process, planktonic cells were first encapsulated in poly(vinyl alcohol) to protect the bacteria against the organic solvents used in the second step employing coaxial electrospinning.
- ItemCharge isomers of myelin basic protein: Structure and interactions with membranes, nucleotide analogues, and calmodulin(San Francisco, CA : Public Library of Science, 2011) Wang, C.; Neugebauer, U.; Bürck, J.; Myllykoski, M.; Baumgärtel, P.; Popp, J.; Kursula, P.As an essential structural protein required for tight compaction of the central nervous system myelin sheath, myelin basic protein (MBP) is one of the candidate autoantigens of the human inflammatory demyelinating disease multiple sclerosis, which is characterized by the active degradation of the myelin sheath. In this work, recombinant murine analogues of the natural C1 and C8 charge components (rmC1 and rmC8), two isoforms of the classic 18.5-kDa MBP, were used as model proteins to get insights into the structure and function of the charge isomers. Various biochemical and biophysical methods such as size exclusion chromatography, calorimetry, surface plasmon resonance, small angle X-ray and neutron scattering, Raman and fluorescence spectroscopy, and conventional as well as synchrotron radiation circular dichroism were used to investigate differences between these two isoforms, both from the structural point of view, and regarding interactions with ligands, including calmodulin (CaM), various detergents, nucleotide analogues, and lipids. Overall, our results provide further proof that rmC8 is deficient both in structure and especially in function, when compared to rmC1. While the CaM binding properties of the two forms are very similar, their interactions with membrane mimics are different. CaM can be used to remove MBP from immobilized lipid monolayers made of synthetic lipids - a phenomenon, which may be of relevance for MBP function and its regulation. Furthermore, using fluorescently labelled nucleotides, we observed binding of ATP and GTP, but not AMP, by MBP; the binding of nucleoside triphosphates was inhibited by the presence of CaM. Together, our results provide important further data on the interactions between MBP and its ligands, and on the differences in the structure and function between MBP charge isomers.
- ItemConsensus model of a cyanobacterial light-dependent protochlorophyllide oxidoreductase in its pigment-free apo-form and photoactive ternary complex(London : Springer Nature, 2019) Schneidewind, Judith; Krause, Frank; Bocola, Marco; Stadler, Andreas Maximilian; Davari, Mehdi D.; Schwaneberg, Ulrich; Jaeger, Karl-Erich; Krauss, UlrichPhotosynthetic organisms employ two different enzymes for the reduction of the C17 = C18 double bond of protochlorophyllide (Pchlide), yielding the chlorophyll precursor chlorophyllide. First, a nitrogenase-like, light-independent (dark-operative) Pchlide oxidoreductase and secondly, a light-dependent Pchlide oxidoreductase (LPOR). For the latter enzyme, despite decades of research, no structural information is available. Here, we use protein structure modelling, molecular dynamics (MD) simulations combined with multi-wavelength analytical ultracentrifugation (MWA-AUC) and small angle X-ray scattering (SAXS) experiments to derive a consensus model of the LPOR apoprotein and the substrate/cofactor/LPOR ternary complex. MWA-AUC and SAXS experiments independently demonstrate that the apoprotein is monomeric, while ternary complex formation induces dimerization. SAXS-guided modelling studies provide a full-length model of the apoprotein and suggest a tentative mode of dimerization for the LPOR ternary complex, supported by published cross-link constraints. Our study provides a first impression of the LPOR structural organization.
- ItemAnalyses and localization of pectin-like carbohydrates in cell wall and mucilage of the green alga Netrium digitus(Wien [u.a.] : Springer, 2010) Eder, M.; Lütz-Meindl, U.The unicellular, simply shaped desmid Netrium digitus inhabiting acid bog ponds grows in two phases. Prior to division, the cell elongates at its central zone, whereas in a second phase, polar tip growth occurs. Electron microscopy demonstrates that Netrium is surrounded by a morphologically homogeneous cell wall, which lacks pores. Immunocytochemical and biochemical analyses give insight into physical wall properties and, thus, into adaptation to the extreme environment. The monoclonal antibodies JIM5 and JIM7 directed against pectic epitopes with different degrees of esterification label preferentially growing wall zones in Netrium. In contrast, 2F4 marks the cell wall only after experimental de-esterification. Electron energy loss spectroscopy reveals Ca-binding capacities of pectins and gives indirect evidence for the degree of their esterification. An antibody raised against Netrium mucilage is not only specific to mucilage but also recognizes wall components in transmission electron microscopy and dot blots. These results indicate a smooth transition between mucilage and the cell wall in Netrium. © 2009 The Author(s).
- ItemCytoskeletal transition in patterned cells correlates with interfacial energy model(London [u.a.] : Royal Society of Chemistry, 2014) Müller, A.; Meyer, J.; Paumer, T.; Pompe, T.A cell's morphology is intricately regulated by microenvironmental cues and intracellular feedback signals. Besides biochemical factors, cell fate can be influenced by the mechanics and geometry of the surrounding matrix. The latter point was addressed herein, by studying cell adhesion on two-dimensional micropatterns. Endothelial cells were grown on maleic acid copolymer surfaces structured with stripes of fibronectin by microcontact printing. Experiments showed a biphasic behaviour of actin stress fibre spacing in dependence on the stripe width with a critical size of approx. 15 μm. In a concurrent modelling effort, cells on stripes were simulated as droplet-like structures, including variations of interfacial energy, total volume and dimensions of the nucleus. A biphasic behaviour with regard to cell morphology and area was found, triggered by the minimum of interfacial energy, with the phase transition occurring at a critical stripe width close to the critical stripe width found in the cell experiment. The correlation of experiment and simulation suggests a possible mechanism of the cytoskeletal rearrangements based on interfacial energy arguments.