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Research project (§ 26 & § 27)
Duration : 2019-01-01 - 2021-12-31

Carbon nano tubes (CNTs) are cylindrical nano structures made of carbon atoms. Due to their outstanding mechanical and electrical properties, and thermal conductivity, they are already used as additives in various novel materials. Recently, CNTs have also been considered for several medical applications due to their small diameters and ability to penetrate cells and tissues. However, since CNTs are chemically inert and insoluble in water, they have to be chemically functionalized or coated with biomolecules to carry payloads or interact with the environment. Proteins bound to the surface of CNTs are preferred because they provide a better biocompatibility and offer functional groups for binding additional molecules. Nevertheless, their arrangement and density on the CNT surface and, consequently the availability of functional groups, varies considerably. An alternative approach to functionalize CNTs with an - additionally closed and precisely ordered - protein layer is offered by bacterial surface layer (S-layers) proteins which have already attracted much attention in the functionalization of surfaces as well as supporting structures for biomembranes. In a broad range of bacteria and archaea S-layer proteins cover the cells completely and may be considered as one of the most abundant biopolymers on earth. S-layer protein lattices show parameters in the nanometer range and offer surface chemical groups and genetically introduced biologically functional domains in precisely defined locations and orientation on their surfaces. Moreover, and highly relevant for this project too, is the natural capability of isolated S-layer proteins to self-assemble into monolayers in solution and at interfaces (e.g. on solid supports). The overall project aim is to conduct fundamental studies on the reassembly of S-layer proteins on CNTs and learn from nature how these new hybrid architectures may be used to make novel materials e.g. for biosensing. Key are the reassembly and binding properties of S-layer proteins which allow a highly specific and sensitive functionalization of the CNT surface. Moreover, novel hybrid organic-inorganic nano structures (e.g. nano containers for drug delivery) will become possible by using the S-layer coating as template in the biomineralization of silica, metals or other technologically important materials. Further on, it may also be assumed that the pores in the S-layer lattice will induce an ordered arrangement of metallic nanoparticles directly on the CNT surface and thus might lead to new electronic effects along the “one-dimensional” CNTs. Based on these few examples of an S-layer protein and CNTs construction kit, we would like to stress that our research, although longer term in nature, might lead to a new technology for the functionalization of carbon nanotube surfaces.
Research project (§ 26 & § 27)
Duration : 2017-08-01 - 2020-07-31

Due to global warming an increase of average temperatures is expected, which will affect tree populations in Austrian forests. More drought resistant species such as oak and pine will adapt, which are known to accumulate higher contents of extractives in their inner “heartwood”. Some of these extractive components are known to enhance the trees natural durability by protecting against microbial attacks. Apart of the fact that heartwood is essential for a long-living tree, these more durable heartwoods are desired for construction applications and might give access to valuable add-on products in a biorefinery process. On the other hand in the paper and timber industry the presence of extractives is not always welcome as technical processes may be hindered and have to be adapted. Heartwood formation has been studied since a long time. High variabilities among species, within single trees and under different environmental conditions have shown the complexity of this natural drying and impregnation process. Up to know, the chemical characterization has been mainly achieved by using different wet-chemical and chromatographic analysis. The context and relation to the wood microstructure is lost and often not all components are solved as changes in composition might need other treatment conditions and interactions with other cell wall polymers might occur. Still a knowledge gap exists on the distribution of these extractives on the micro- and nano scale and their interaction with other wood components. Are they mainly accumulated in the place of biosynthesis in the ray parenchyma cells or also transported to and impregnated in the fiber, tracheid and vessel cell walls? Is it a fast process or an ongoing slow polymerization process with changes in time and age? With this project these knowledge gaps will be filled by investigating native never dried heartwood samples by state of the art microspectroscopic in-situ approaches. Fluorescence microscopy will give an overview of the distribution of the phenolic compounds and Raman microscopy deliver a more detailed picture on the chemical composition in context with the microstructure as well as TOF-SIMS microscopy. Co-located ESEM will elucidate the ultrastructure of the changing cell walls during heartwood formation. With these approaches the we will 1) monitor heartwood formation of pine, douglas fir and oak trees by following the extractives from biosynthesis to the cell wall impregnation, 2) Assess the interactions of the extractives with other cell wall components and 3) determine the role of drying during the formation of heartwood and for a kind of “self-sealing” effect observed in some preliminary experiments. The results will reveal new insights into the biology of heartwood due to the detailed in-situ studies on the extractive distribution in context with the micro-and nanostructure as well as changes, solubilities and interactions. Furthermore in comparison to the natural dry falling of the tracheids the effects induced by artificial drying and thus important characteristics of wood as an industrial raw material will be derived. This will break new scientific grounds in the field of plant physiology (tree ageing), biomimetic plant protection mechanisms (decay resistance, “self-sealing”), but also regarding optimization of industrial applications and processes and the valorisation of add-on products in new biorefinery concepts.
Research project (§ 26 & § 27)
Duration : 2017-01-01 - 2021-12-31

Bacterial surface layer proteins (S-layers) have the ability to build protein crystal layers with nanometer regularity on solution and many different substrates. They are currently being tested as nano-templates for different biotechnological applications. However, the (path)way in which such proteins self-assemble forming organized nanostructures is not fully understood. In this context, we propose to investigate the recrystallization of three S-layer proteins, wild type SbpA and the recombinant proteins rSbpA31–1068 and rSbpA31-918, on (molecularly controlled) hydrophobic and hydrophilic disulfides. First, we will study the adsorption kinetics and recrystallization of the three bacterial proteins. Second, we would like to find the relation between the kinetics and the physical properties of the formed protein crystal (e.g. crystal domain size, lattice parameters). Third, we would like to clarify the question of the recrystallization pathway as a function of the properties of the substrate for these bacterial proteins (which also imply to get insight about protein/substrate interactions, especially about the recognition by the protein of hydrophobic and/or hydrophilic moieties).

Supervised Theses and Dissertations