An emerging new direction of research focuses on developing "self-synthesizing materials", those supramolecular structures that can promote their own formation by accelerating the synthesis of building blocks and/or an entire assembly. It was postulated recently that practical design of such systems can benefit from the ability to control the assembly of amphiphilic molecules into nanostructures. We describe here the self-assembly pathway of short amphiphilic peptides into various forms of soluble β-sheet structures--β-plates, fibrils, and hollow nanotubes--and their consequent activity as autocatalysts for the synthesis of monomeric peptides from simpler building blocks. A detailed kinetic analysis of both the self-assembly and self-replication processes allows us to suggest a full model and simulate the replication process, revealing that only specific structures, primarily fibrils that are stable within the solution for a time shorter than a few hours, can be active as catalysts. Interestingly, we have found that such a process also induces fibril reproduction, in a mechanism very similar to the propagation of prion proteins by transmission of misfolded states.
The self-assembly of two similar amphiphilic peptides into fibril structures is described. Molecular dynamic simulations show that both can organize similarly in a monolayer, but in the fibril bilayer, one prefers a single organization while the other forms two conformational variants. This assembly difference correlates well with our experimental results.
Patterning of nanoparticles on solid substrates is one of the main challenges of current nanotechnology applications. The use of organic molecules as templates for the deposition of the nanoparticles makes it possible to utilize simple soft lithography techniques for patterning. Peptides appear to be powerful candidates for this job due to their versatility and design flexibility. In this work, we demonstrate the use of dual-affinity peptides, which bind both to the substrate and to the deposited nanoparticles, as single-layer linkers for the creation of multi-component nanoparticle patterns via microcontact printing processes. Controlled deposition and patterning of gold colloids or carbon nanotubes (CNTs) on silicon oxide surfaces and that of silicon oxide nanoparticles on gold surfaces have been achieved by the use of the corresponding dual-affinity peptides. Furthermore, patterning of both gold colloids and CNTs on a single substrate on predefined locations has been achieved. The suggested generic approach offers great flexibility by allowing binding of any material to a substrate of choice, provided that a peptide binding segment has been engineered for each of the inorganic components. Furthermore, the diversity of possible peptide sequences allows the formation of multi-component patterns, paving the way to fabricating complex functional structures based on peptide templates.
Photosynthesis is Nature's major process for converting solar into chemical energy. One of the key players in this process is the multiprotein complex photosystem I (PSI) that through absorption of incident photons enables electron transfer, which makes this protein attractive for applications in bioinspired photoactive hybrid materials. However, the efficiency of PSI is still limited by its poor absorption in the green part of the solar spectrum. Inspired by the existence of natural phycobilisome light-harvesting antennae, we have widened the absorption spectrum of PSI by covalent attachment of synthetic dyes to the protein backbone. Steady-state and time-resolved photoluminescence reveal that energy transfer occurs from these dyes to PSI. It is shown by oxygen-consumption measurements that subsequent charge generation is substantially enhanced under broad and narrow band excitation. Ultimately, surface photovoltage (SPV) experiments prove the enhanced activity of dye-modified PSI even in the solid state.
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