Peptoid nanosheets exhibit a new secondary-structure motif

Abstract

A promising route to the synthesis of protein-mimetic materials that are capable of complex functions, such as molecular recognition and catalysis, is provided by sequence-defined peptoid polymers--structural relatives of biologically occurring polypeptides. Peptoids, which are relatively non-toxic and resistant to degradation, can fold into defined structures through a combination of sequence-dependent interactions. However, the range of possible structures that are accessible to peptoids and other biological mimetics is unknown, and our ability to design protein-like architectures from these polymer classes is limited. Here we use molecular-dynamics simulations, together with scattering and microscopy data, to determine the atomic-resolution structure of the recently discovered peptoid nanosheet, an ordered supramolecular assembly that extends macroscopically in only two dimensions. Our simulations show that nanosheets are structurally and dynamically heterogeneous, can be formed only from peptoids of certain lengths, and are potentially porous to water and ions. Moreover, their formation is enabled by the peptoids' adoption of a secondary structure that is not seen in the natural world. This structure, a zigzag pattern that we call a Σ('sigma')-strand, results from the ability of adjacent backbone monomers to adopt opposed rotational states, thereby allowing the backbone to remain linear and untwisted. Linear backbones tiled in a brick-like way form an extended two-dimensional nanostructure, the Σ-sheet. The binary rotational-state motif of the Σ-strand is not seen in regular protein structures, which are usually built from one type of rotational state. We also show that the concept of building regular structures from multiple rotational states can be generalized beyond the peptoid nanosheet system.

Radiation Influence on Edible Materials

“…A promising route to the synthesis of protein-mimetic materials that are capable of complex functions, such as molecular recognition and catalysis, is provided by peptoid nanosheets polymers structurally related to biologically occurring polypeptides [75].…”

Polypeptoid polymers: Synthesis, characterization, and properties

“…As a result, the global conformations of polypeptoids are strongly dependent on the N-substituent structures, giving rise to random coils or well-defined secondary structures [eg, polyproline I (PPI) helix [1][2][3][4][5][6] and R-sheets] [7][8][9][10][11][12] that are reminiscent of those of polypeptides. The polypeptoid backbone containing tertiary amide linkages is highly polar and hydrophilic.…”

“…The polypeptoid backbone containing tertiary amide linkages is highly polar and hydrophilic. The physicochemical properties of polypeptoids can be tailored by the N-substituent structures, enabling control over the hydrophilicity and lipophilicity balance (HLB), charge characteristics, [13,14] backbone conformation, [1][2][3][4][5][6][7][8][9][10][11][12] solubility, [15][16][17][18][19][20] thermal and crystallization properties of the polypeptoids. [21][22][23][24] Without extensive hydrogen bonding, polypeptoids are thermally processable similar to conventional thermoplastics, [20][21][22][23][24] whereas polypeptides undergo thermal degradation before they can be melt-processed due to the extensive hydrogen bonding interactions.…”

Improved chemical and mechanical stability of peptoid nanosheets by photo-crosslinking the hydrophobic core

“…1,2 Peptoids are a class of robust, informationrich, chemically-diverse peptidomimetic polymers composed of N-substituted glycine monomers. 3 Like peptides, they have the ability to adopt distinct secondary structures such as ribbons, 4 helices, 5,6 sheets, 7 turns, 8 and cyclic structures; 9,10 however, the lack of a backbone hydrogen bond donor (NH) and chirality forces peptoid oligomers to conform to different folding rules as compared to their peptide counterparts. 11 Peptoids can be engineered to adopt multiple two and three-dimensional supramolecular assemblies including superhelices, 12 multi-helical bundles 13,14 and two-dimensional nanosheets.…”

“…25,26 In our case, we would expect the chlorophenyl groups to be in close proximity to several neighboring and apposing phenyl groups, and upon exposure of an aqueous nanosheet solution to ultraviolet radiation (254 nm), numerous biphenyl crosslinks should form. The chlorinated nanosheet forming peptoid polymer (referred to as B28-pCl 7 , Fig. 1a) was synthesized by the previously reported automated solid phase submonomer method and purified by preparative reversed phase HPLC.…”