@article{FeifelStiegerKappetal.2016, author = {Feifel, Sven Christian and Stieger, Kai Ralf and Kapp, Andreas and Weber, Dennis and Allegrozzi, Marco and Piccioli, Mario and Turano, Paola and Lisdat, Fred}, title = {Insights into Interprotein Electron Transfer of Human Cytochrome c Variants Arranged in Multilayer Architectures by Means of an Artificial Silica Nanoparticle Matrix}, series = {ACS Omega}, volume = {1}, journal = {ACS Omega}, number = {6}, issn = {2470-1343}, doi = {10.1021/acsomega.6b00213}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-6753}, pages = {1058 -- 1066}, year = {2016}, abstract = {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.}, language = {en} } @article{KoelschHejaziStiegeretal.2018, author = {K{\"o}lsch, Adrian and Hejazi, Mahdi and Stieger, Kai Ralf and Feifel, Sven Christian and Kern, Jan F. and M{\"u}h, Frank and Lisdat, Fred and Lokstein, Heiko and Zouni, Athina}, title = {Insights into the binding behavior of native and non-native cytochromes to photosystem I from Thermosynechococcus elongatus}, series = {Journal of Biological Chemistry}, volume = {293}, journal = {Journal of Biological Chemistry}, number = {23}, issn = {1083-351X}, doi = {10.1074/jbc.RA117.000953}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12780}, pages = {9090 -- 9100}, year = {2018}, abstract = {The binding of photosystem I (PS I) from Thermosynechococcus elongatus to the native cytochrome (cyt) c6 and cyt c from horse heart (cyt cHH) was analyzed by oxygen consumption measurements, isothermal titration calorimetry (ITC), and rigid body docking combined with electrostatic computations of binding energies. Although PS I has a higher affinity for cyt cHH than for cyt c6, the influence of ionic strength and pH on binding is different in the two cases. ITC and theoretical computations revealed the existence of unspecific binding sites for cyt cHH besides one specific binding site close to P700. Binding to PS I was found to be the same for reduced and oxidized cyt cHH. Based on this information, suitable conditions for cocrystallization of cyt cHH with PS I were found, resulting in crystals with a PS I:cyt cHH ratio of 1:1. A crystal structure at 3.4-{\AA} resolution was obtained, but cyt cHH cannot be identified in the electron density map because of unspecific binding sites and/or high flexibility at the specific binding site. Modeling the binding of cyt c6 to PS I revealed a specific binding site where the distance and orientation of cyt c6 relative to P700 are comparable with cyt c2 from purple bacteria relative to P870. This work provides new insights into the binding modes of different cytochromes to PS I, thus facilitating steps toward solving the PS I-cyt c costructure and a more detailed understanding of natural electron transport processes.}, language = {en} } @misc{StiegerFeifelLoksteinetal.2018, author = {Stieger, Kai Ralf and Feifel, Sven Christian and Lokstein, Heiko and Hejazi, Mahdi and Zouni, Athina and Lisdat, Fred}, title = {Biohybride Architekturen f{\"u}r eine effiziente Umwandlung von Licht in elektrische Energie durch Integration von Photosystem I in skalierbare mesopor{\"o}se 3D Elektroden}, series = {Wissenschaftliche Beitr{\"a}ge 2018}, volume = {22}, journal = {Wissenschaftliche Beitr{\"a}ge 2018}, issn = {0949-8214}, doi = {10.15771/0949-8214_2018_2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10220}, pages = {17 -- 24}, year = {2018}, abstract = {Die Kombination von fortschrittlichen Materialien und kontrolliertem Oberfl{\"a}chendesign mit komplexen Proteinen aus der nat{\"u}rlichen Photosynthese ist derzeit eines der Hauptthemen bei der Entwicklung von Biohybridsystemen und Biophotovoltaik. In dieser Studie werden transparente makropor{\"o}se Indium-Zinn-Oxid-(μITO-) Elektroden mit dem trimeren Superkomplex Photosystem I (PSI) aus dem Cyanobakterium Thermosynechococcus elongatus sowie dem kleinen Redoxprotein Cytochrom c (Cyt c) kombiniert, um neuartige und effiziente biohybride Photokathoden herzustellen. Mit diesen bis zu 40 μm hohen 3D-Strukturen k{\"o}nnen beide Proteine in einer ann{\"a}hernden Monolage abgeschieden werden und die elektrische Kommunikation mit der Elektrode kann erzielt werden. Der generierte Photostrom folgt dabei linear der kontrollierbaren Schichtdicke der μITO-Elektrode, wobei Stromdichten von bis zu 150 μA cm -2 erhalten werden. Eine effiziente elektrische Kopplung der Proteine kann durch die hohe interne Quanteneffizienz von 30 \% gezeigt werden.}, language = {de} }