Self-assembly of the ionic peptide EAK16: the effect of charge distributions on self-assembly.
Amphiphilic peptides suspended in aqueous solution display a rich set of aggregation behavior. Molecular-level studies of relatively simple amphiphilic molecules under controlled conditions are an essential step toward a better understanding of self-assembly phenomena of naturally occurring peptides/proteins. Here, we study the influence of molecular architecture and interactions on the self-assembly of model peptides (EAK16s), using both experimental and theoretical approaches. Three different types of EAK16 were studied: EAK16-I, -II, and -IV, which have the same amino acid composition but different amino acid sequences. Atomic force microscopy confirms that EAK16-I and -II form fibrillar assemblies, whereas EAK16-IV forms globular structures. The Fourier transform infrared spectrum of EAK16-IV indicates the possible formation of a beta-turn structure, which is not found in EAK16-I and -II. Our theoretical and numerical studies suggest the underlying mechanism behind these observations. We show that the hairpin structure is energetically stable for EAK16-IV, whereas the chain entropy of EAK16-I and -II favors relatively stretched conformations. Our combined experimental and theoretical approaches provide a clear picture of the interplay between single-chain properties, as determined by peptide sequences (or charge distributions), and the emerging structure at the nano (or more coarse-grained) level.
Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
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Hong
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Imamura
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Ha
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Bechhoefer
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Chen
D003198:Computer Simulation; D019281:Dimerization; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000648:ultrastructure*; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D055672:Static Electricity
C098329:EAK16 peptide; D046912:Multiprotein Complexes; D009842:Oligopeptides