Self-assembly of membrane-like materials from highly stable protein-mimetics
Protein self-assembly is a commonplace phenomenon in living systems and is frequently responsible for building molecular machines that carry out the vast array of functions, such as molecular separation and selective ion transport. Inspired by in nature, various proteins and peptides have been designed and exploited for self-assembly of functional materials in vitro. However, the application of these protein- and peptide-based materials is limited because of their poor stabilities against thermal and chemical degradation. Therefore, there is a great need to develop protein-like synthetic polymers that can function like proteins and peptides for molecular recognition and self-assembly, but exhibit high stabilities. There are several known chemical systems that can create non-natural, sequence-specific polymers, such as ?-peptides and peptoids (poly-N-substituted glycines). Peptoids have received particular attention because they can be cheaply and efficiently synthesized, and several hundred commercially available amines can be used to build their large side-chain diversity. We recently demonstrated that peptoids were able to mimic peptides commonly present in natural biominerals for unprecedented control over both calcite morphology and growth kinetics. In this presentation, we report our progress in exploiting peptoids to mimic proteins and peptides for self-assembly. Specifically, we demonstrate that 12-mer peptoids are able to self-assemble into highly-ordered membrane-like materials both in solution and on substrate surfaces. In aqueous solution, these peptoids self-assemble into highly-crystalline and free-floating nanosheets through a solvent-driven crystallization process. These nanosheets have single-bilayer thickness (3.2 nm) and large area (up to mm2). X-ray diffraction data indicate that these peptoids are highly packed through p-p stacking and peptoid side-chain hydrogen bonding. These results represent the smallest peptoid oligomers that self-assemble into free-floating nanosheets and do not require the compression of monolayers formed at the water-air interface. The formation of single-bilayer-thick nanosheets also occurs on various substrate surfaces. For example, on freshly-cleaved mica surface, we observed that nanosheets were formed through a heterogeneous nucleation process. Similar nanosheets were assembled even when 12-mer peptoids were specifically conjugated with functional groups, indicating that self-assembly of 12-mer peptoids into nanosheets is robust, and these nanosheets can serve as a well-defined 2D platform for post-functionalization. Peptoid self-assembly is highly sequence-specific, and pH sensitive. When the diblock-like 12-mer peptoids are switched to an alternative motif, the resulting 12-mers only self-assemble into fiber-like materials. Multi-scale simulations are also used to provide insights into peptoid-assembly mechanisms
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1797564
- Report Number(s):
- PNNL-SA-108839
- Resource Relation:
- Conference: 2015 MRS Spring Meeting & Exhibit April 6-10, 2015 San Francisco, California
- Country of Publication:
- United States
- Language:
- English
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