Self-Assembly of β-Sheets into Nanostructures by Poly(alanine) Segments Incorporated in Multiblock Copolymers Inspired by Spider Silk

Abstract

Selective replacement of the amorphous peptide domain of a spider silk with poly(ethylene glycol) gave N. clavipes silk-inspired polymers having similar solid-state structures and very good mechanical properties. The tendency of poly(alanine) having appropriate chain length to form beta-sheets and the facility with which the beta-sheets self-assemble have been retained in the polymers. Solid-state (13)C NMR, solid-state FTIR, X-ray diffraction, and AFM studies showed that the polymers formed predominantly antiparallel beta-sheets that self-assembled into discrete nanostructures. The longer the peptide segment was, the greater was the tendency to self-assemble into antiparallel beta-sheet aggregates. AFM revealed that the morphology of the polymers was a microphase-separated architecture that contained irregularly shaped 100-200 nm poly(alanine) nanodomains interspersed within the PEG phase. The results suggest that the poly(alanine) domain influences the solid-state properties of spider silk through beta-sheet self-assembly into temporary cross-links. The results further demonstrate that by selectively replacing certain segments of a naturally occurring biopolymer with a judiciously selected nonnative segment while, at the same time, retaining other segments known to be critical for the essential properties of the native biopolymer, a synthetic polymer with similar properties and function can be obtained.

A toolbox of oligopeptide-modified polymers for tailored elastomers

“…This peak can be assigned to the intermolecular spacing between oligopeptides within a b-sheet tape. Notably, however, it is significantly smaller than the typical value of B4.8 Å observed in proteins, due to strong hydrogen bonding in the hydrophobic matrix 20,30,45,46 . Moreover, M2-M5 exhibited an additional reflection at a spacing of 5.3-5.4 Å, corresponding to the intersheet distance between stacked b-sheets observed in poly(L-alanine) 45 , spider silk (5.30 Å) 47 or related materials 20,30,46 (Fig.…”

“…Inspired by this example of nature's design principles, the selective formation of onedimensional nanostructures from b-sheet-forming oligopeptides and oligopeptide-modified polymers has been extensively investigated [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] . However, the thermomechanical properties of the corresponding bulk materials have rarely been studied in much detail [29][30][31] . Supramolecular materials from polymers with other types of hydrogen-bonded end groups have frequently been used to obtain thermoplastic elastomers with superior processing behaviour at elevated temperatures [32][33][34][35][36][37][38][39] .…”

Controlling supramolecular polymerization through multicomponent self‐assembly

“…384 This observation was attributed to the slow crystallization of the PFS-core in protic polar solvents. 385 Due to the kinetic stability of the cylindrical micelles the Winnik and Manners groups have been able to build increasingly sophisticated superstructures with multiple levels of structural hierarchy, for example the gradient CDSA into cylindrical comicelles with segmented coronas, 386 the self-assembly of the multiblock comicelles into nanofibrillar hydrogels, 387 [394][395][396][397][398][399][400][401] In most of the reported examples these triblocks consist of a central silk inspired [402][403][404][405][406][407][408][409] repeat of (GAGAGAGX) n (where X 5 E, K, or H; n 5 48), which are flanked by two hydrophilic and inert collagen-based blocks that are dimers of the triplet repeat (GXY) n (where X and Y are rich in Q, N, and S; n 5 99) (Fig. 31).…”

Z. Guan, Control of polymer topology through late‐transition‐metal catalysis, J Polym Sci Part A: Polym Chem (2003), 41(22), 3680–3692

“…CONTROL OF POLYMER TOPOLOGY nation of early-or late-transition-metal complexes (16)(17)(18)(19) with an excess of an aluminum compound (AlR x Cl 3Ϫx ; Scheme 8). These catalyst systems were shown to oligomerize ethylene to form branched oligomers with a number-average molecular weight (M n ) of less than 2000.…”