Research group "Hybrid Materials"

Group leader:


Martin Humenik, PhD. 0921-55 7347
  martin.humenik(.at.)bm.uni-bayreuth.de
   

Research overview

Self-assembly is based on autonomous mechanisms of non-covalent interactions between distinct building blocks. Related processes do not require an external energy source and have no limitation in dimensional scaling. This “bottom up” approach results in formation of nanostructured materials organized at different hierarchical levels, as represented by highly stable bones, shells or spider silks in nature. Application of the principles of self-assembly in controlled nano- and micro scaled structuring and ordering of materials is in the focus of our group.

Self-assembly properties of spider silk combined with functionalities of biomacromolecules will allow construction of nanostructured hybrid materials for on-demand functionality localized in 1D along the fibril and/or in 2D on surfaces.

DNA-protein hybrids

The proteins in focus self-assemble into nanofibrils, i.e. supramolecular structures of densely packed cross-beta sheets. Such fibrils, typically < 10 nm in diameter and hundreds nanometers long, possess a high aspect ratio, high environmental and chemical stability as well as mechanical rigidity. These systems are highly attractive for the creation of ordered nanomaterials especially in combination with metallic nanoparticles, enzymes and dyes for novel electronic, optic and catalytic applications.

Nucleic acids can self-assemble into many different nano-structures with precision and predictability, which is unrivalled among natural and synthetic materials. One of the best example for such high fidelity is programming and folding of DNA origami. In order to take advantage of both protein and DNA materials, we chemically combine structural proteins such as spider silk and nucleic acids in hybrid entities. The fundamental properties of the protein hybrid systems are investigated to realize their utilization in materials research. Moreover, we study new chemical modifications and conjugations of the building blocks, arrangements and assembly of modified protein moieties, morphology and structure of conjugate fibrils, as well as their self-organization into hierarchical nanostructures upon DNA interactions in solutions and on surfaces.

 

Self-organization of DNA-protein hybrid materials in “bottom up” approach in solution: Spider silk moieties prepared upon a chemical conjugation with DNA were spatially arranged into branched structures using designed DNA hybridization and self-assembled into ribbons, which further self-organized into micro-rafts due to DNA interaction at specific temperature gradients.
 

 

Patterning of the hybrid materials using DNA-directed hybridization technology: Surfaces modified by capture DNA were specifically linked to complementary DNA-spider silk conjugates on defined positions using micro-contact printing technology. Immobilized conjugates served as nucleation sites for silk fibril growth on the surface.
 
Protein fusion constructs

Recombinant spider silk proteins were genetically combined with globular domains to introduce new functions to the silk structuring domain. As an example, GFP was successfully fused to the C-terminus of the recombinant spider silk. Both, silk and the GFP moieties, retained native structures in the fusion construct as well as respective properties, the self-assembly of the silk into fibrils and hydrogels, as well as fluorescent activity of the GFP.

 

Functional protein hybrids prepared by fusion of globular and structuring moieties. Schematic representation of GFP (1EMA) fused to the spider silk eADF4(C16). The protein self-assembled into fluorescently active nanoscopic fibrils, which were processed into hydrogels.
 
Selected publications:

• Hybrid materials:

Humenik, M.*, Mohrand, M., & Scheibel, T. (2018) Self-assembly of spider silk-fusion proteins comprising enzymatic and fluorescence activity. Bioconjugate Chemistry doi: 10.1021/acs.bioconjchem.1027b00759.

Humenik, M.* & Scheibel, T. (2014). Self-assembly of nucleic acids, silk and hybrid materials thereof. Journal of Physics: Condensed Matter 26, 503102.

Humenik, M.*, Drechsler, M. & Scheibel, T. (2014). Controlled Hierarchical Assembly of Spider Silk-DNA Chimeras into Ribbons and Raft-Like Morphologies. Nano Letters 14, 3999-4004.

Humenik, M.* & Scheibel, T. (2014). Nanomaterial Building Blocks Based on Spider Silk–Oligonucleotide Conjugates. ACS Nano 8, 1342-1349

• Protein self-assembly:

Humenik, M., Smith, A. M., Arndt, S. & Scheibel, T. (2015). Ion and seed dependent fibril assembly of a spidroin core domain. Journal of Structural Biology 191, 130-138.

Humenik, M., Magdeburg, M. & Scheibel, T. (2014). Influence of repeat numbers on self-assembly rates of repetitive recombinant spider silk proteins. Journal of Structural Biology 186, 431-437.

Humenik, M., Scheibel, T. & Smith, A. (2011). Spider Silk: Understanding the Structure–Function Relationship of a Natural Fiber. In Progress in Molecular Biology and Translational Science (Howorka, S., ed.), Vol. 103, pp. 131-185. Academic Press.

Humenik, M., Smith, A. M. & Scheibel, T. (2011). Recombinant Spider Silks—Biopolymers with Potential for Future Applications. Polymers 3, 640-661.

• DNA-Protein conjugates:

Humenik, M., Poehlmann, C., Wang, Y. & Sprinzl, M. (2008). Enhancement of Electrochemical Signal on Gold Electrodes by Polyvalent Esterase-Dendrimer Clusters. Bioconjugate Chemistry 19, 2456-2461.

Humenik, M., Huang, Y., Wang, Y. & Sprinzl, M. (2007). C-terminal incorporation of bio-orthogonal azide groups into a protein and preparation of protein-oligodeoxynucleotide conjugates by Cu(I)-catalyzed cycloaddition. ChemBioChem 8, 1103-1106.

Wang, Y., Stanzel, M., Gumbrecht, W., Humenik, M. & Sprinzl, M. (2007). Esterase 2-oligodeoxynucleotide conjugates as sensitive reporter for electrochemical detection of nucleic acid hybridization. Biosensors & Bioelectronics 22, 1798-1806.