Silica nanoparticles for the layer-by-layer assembly of fully electro-active cytochrome c multilayers

<p>Abstract</p> <p>Background</p> <p>For bioanalytical systems sensitivity and biomolecule activity are critical issues. The immobilization of proteins into multilayer systems by the layer-by-layer deposition has become one of the favorite methods with this respect. Moreover, the combination of nanoparticles with biomolecules on electrodes is a matter of particular interest since several examples with high activities and direct electron transfer have been found. Our study describes the investigation on silica nanoparticles and the redox protein cytochrome <it>c </it>for the construction of electro-active multilayer architectures, and the electron transfer within such systems. The novelty of this work is the construction of such artificial architectures with a non-conducting building block. Furthermore a detailed study of the size influence of silica nanoparticles is performed with regard to formation and electrochemical behavior of these systems.</p> <p>Results</p> <p>We report on interprotein electron transfer (IET) reaction cascades of cytochrome <it>c </it>(cyt <it>c</it>) immobilized by the use of modified silica nanoparticles (SiNPs) to act as an artificial matrix. The layer-by-layer deposition technique has been used for the formation of silica particles/cytochrome <it>c </it>multilayer assemblies on electrodes. The silica particles are characterized by dynamic light scattering (DLS), Fourier transformed infrared spectroscopy (FT-IR), Zeta-potential and transmission electron microscopy (TEM). The modified particles have been studied with respect to act as an artificial network for cytochrome <it>c </it>and to allow efficient interprotein electron transfer reactions. We demonstrate that it is possible to form electro-active assemblies with these non-conducting particles. The electrochemical response is increasing linearly with the number of layers deposited, reaching a cyt <it>c </it>surface concentration of about 80 pmol/cm²with a 5 layer architecture. The interprotein electron transfer through the layer system and the influence of particle size are discussed.</p> <p>Conclusions</p> <p>This study demonstrates the ability to construct fully electro-active cyt <it>c </it>multilayer assemblies by using carboxy-modified silica nanoparticles. Thus it can be shown that functional, artificial systems can be build up following natural examples of protein arrangements. The absence of any conductive properties in the second building block clearly demonstrates that mechanisms for electron transfer through such protein multilayer assemblies is based on interprotein electron exchange, rather than on wiring of the protein to the electrode.</p> <p>The construction strategy of this multilayer system provides a new controllable route to immobilize proteins in multiple layers featuring direct electrochemistry without mediating shuttle molecules and controlling the electro-active amount by the number of deposition steps.</p

In vitro chemoenzymatic and in vivo biocatalytic syntheses of new beauvericin analogues

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.New beauvericins have been synthesized using the nonribosomal peptide synthetase BbBEAS from the entomopathogenic fungus Beauveria bassiana. Chemical diversity was generated by in vitro chemoenzymatic and in vivo whole cell biocatalytic syntheses using either a B. bassiana mutant or an E. coli strain expressing the bbBeas gene.DFG, EXC 314, Unifying Concepts in Catalysi

Catalytically Active Silica Nanoparticle-Based Supramolecular Architectures of Two Proteins - Cellobiose Dehydrogenase and Cytochrome c on Electrodes

Artificial nanobiomolecular architectures that follow natural examples in protein assembly become more and more important from basic and applied points of view. Our study describes the investigation on cellobiose dehydrogenase (CDH), cytochrome c (cyt c), and silica nanoparticles (SiNP's) for the construction of fully catalytically active supramolecular architectures on electrodes. We report on intraprotein, interprotein, and direct electron-transfer reaction cascades of cellobiose dehydrogenase and cytochrome c immobilized in multiple supramolecular layers. Carboxy-modified SiNP's are used to provide an artificial matrix, which enables protein arrangement in an electroactive form. Direct and interprotein electron transfer has been established for a two-protein system with CDH and cyt c in a layered architecture for the first time. We also highlight that the glycosylation of CDH and the silica nanoparticle size play key roles in the mode of operation in such a complex system. The response of the specific substrate, here lactose, can be tuned by the number of immobilized nanobiomolecular layers

Advanced unidirectional photocurrent generation via cytochrome c as reaction partner for directed assembly of photosystem I

Conversion of light into an electrical current based on biohybrid systems mimicking natural photosynthesis is becoming increasingly popular. Photosystem I (PSI) is particularly useful in such photo-bioelectrochemical devices. Herein, we report on a novel biomimetic approach for an effective assembly of photosystem I with the electron transfer carrier cytochrome c (cyt c), deposited on a thiol-modified gold-surface. Atomic force microscopy and surface plasmon resonance measurements have been used for characterization of the assembly process. Photoelectrochemical experiments demonstrate a cyt c mediated generation of an enhanced unidirectional cathodic photocurrent. Here, cyt c can act as a template for the assembly of an oriented and dense layer of PSI and as wiring agent to direct the electrons from the electrode towards the photosynthetic reaction center of PSI. Furthermore, three-dimensional protein architectures have been formed via the layer-by-layer deposition technique resulting in a successive increase in photocurrent densities. An intermittent cyt c layer is essential for an efficient connection of PSI layers with the electrode and for an improvement of photocurrent densities

Electrocatalytically active multi-protein assemblies using nanoscaled building blocks

Biosensors based on nanomaterials constitute an emerging area of interdisciplinary research. In particular in electrochemical sensors, electron transfer cascades can be used for defined signal generation. Our study describes the investigation of silica nanoparticles (SiNPs), DNA, cytochrome c (cyt c) and cellobiose dehydrogenase (CDH) for the development of catalytically active multi-protein assemblies. We report on direct and interprotein electron transfer reaction cascades of CDH and cyt c in an immobilized form by means of nanoscaled building blocks: Carboxy-modified SiNPs, and DNA. The building blocks provide an artificial matrix, which permit protein arrangement in an electro- and catalytically-active form. Multilayered protein architectures on electrodes featuring direct and interprotein electron transfer by the use of entirely different nanoscaled building blocks has been established for the first time. In addition we highlight, that the secondary building blocks (DNA or SiNPs) used for the construction as well as the glycosylation of the enzyme (CDH) play a key role for the mode of operation in such complex entities

Unidirectional photocurrent of photosystem I on π-system-modified graphene electrodes: nanobionic approaches for the construction of photobiohybrid systems

One major vital element of the oxygenic photosynthesis is photosystem I (PSI). We report on the construction of graphene-based nanohybrid light-harvesting architectures consisting of PSI supercomplexes adsorbed onto π-system-modified graphene interfaces. The light-driven nanophotobioelectrochemical architectures have been designed on a modified carbon surface, on the basis of π–π-stacking interactions between polycyclic aromatic compounds and graphene. As a result of the remarkable features of graphene and the feasibility of purposeful surface property adjustment, well-defined photoelectrochemical responses have been displayed by the nanophotohybrid electrodes. In particular, the PSI–graphene electrodes utilizing naphthalene derivatives provided a suitable surface for the adsorption of PSI and display already at the open circuit potential (OCP) a high cathodic photocurrent output of 4.5 ± 0.1 μA/cm2. By applying an overpotential and addition of a soluble electron acceptor (methyl viologen), the photocurrent density can be further magnified to 20 ± 0.5 μA/cm2. On the contrary, the investigated anthracene-based PSI–graphene electrodes exhibit considerably smaller and not very directed photoelectrochemical responses. This study grants insights into the influences of different polycyclic aromatic compounds acting as an interface between the very large protein supercomplex PSI and graphene while supporting the electrochemical communication of the biomolecule with the electrode. It needs to be emphasized that solely the naphthalene-based photoelectrodes reveal unidirectional cathodic photocurrents, establishing the feasibility of utilizing this advanced approach for the construction of next-generation photovoltaic devices

Catalytically Active Silica Nanoparticle-Based Supramolecular Architectures of Two Proteins – Cellobiose Dehydrogenase and Cytochrome <i>c</i> on Electrodes

Artificial nanobiomolecular architectures that follow natural examples in protein assembly become more and more important from basic and applied points of view. Our study describes the investigation on cellobiose dehydrogenase (CDH), cytochrome <i>c</i> (cyt <i>c</i>), and silica nanoparticles (SiNP's) for the construction of fully catalytically active supramolecular architectures on electrodes. We report on intraprotein, interprotein, and direct electron-transfer reaction cascades of cellobiose dehydrogenase and cytochrome <i>c</i> immobilized in multiple supramolecular layers. Carboxy-modified SiNP's are used to provide an artificial matrix, which enables protein arrangement in an electroactive form. Direct and interprotein electron transfer has been established for a two-protein system with CDH and cyt <i>c</i> in a layered architecture for the first time. We also highlight that the glycosylation of CDH and the silica nanoparticle size play key roles in the mode of operation in such a complex system. The response of the specific substrate, here lactose, can be tuned by the number of immobilized nanobiomolecular layers

Engineering of supramolecular photoactive protein architectures: the defined co-assembly of photosystem I and cytochrome c using a nanoscaled DNA-matrix

The engineering of renewable and sustainable protein-based light-to-energy converting systems is an emerging field of research. Here, we report on the development of supramolecular light-harvesting electrodes, consisting of the redox protein cytochrome c working as a molecular scaffold as well as a conductive wiring network and photosystem I as a photo-functional matrix element. Both proteins form complexes in solution, which in turn can be adsorbed on thiol-modified gold electrodes through a self-assembly mechanism. To overcome the limited stability of self-grown assemblies, DNA, a natural polyelectrolyte, is used as a further building block for the construction of a photo-active 3D architecture. DNA acts as a structural matrix element holding larger protein amounts and thus remarkably improving the maximum photocurrent and electrode stability. On investigating the photophysical properties, this system demonstrates that effective electron pathways have been created