Self-assembly of short peptides composed of only aliphatic amino acids and a combination of aromatic and aliphatic amino acids.
ABSTRACT The morphology of structures formed by the self-assembly of short N-terminal t-butyloxycarbonyl (Boc) and C-terminal methyl ester (OMe) protected and Boc-deprotected hydrophobic peptide esters was investigated. We have observed that Boc-protected peptide esters composed of either only aliphatic hydrophobic amino acids or aliphatic hydrophobic amino acids in combination with aromatic amino acids, formed highly organized structures, when dried from methanol solutions. Transmission and scanning electron microscopic images of the peptides Boc-Ile-Ile-OMe, Boc-Phe-Phe-Phe-Ile-Ile-OMe and Boc-Trp-Ile-Ile-OMe showed nanotubular structures. Removal of the Boc group resulted in disruption of the ability to form tubular structures though spherical aggregates were formed. Both Boc-Leu-Ile-Ile-OMe and H-Leu-Ile-Ile-OMe formed only spherical nanostructures. Dynamic light scattering studies showed that aggregates of varying dimensions were present in solution suggesting that self-assembly into ordered structures is facilitated by aggregation in solution. Fourier transform infrared spectroscopy and circular dichroism spectroscopy data show that although all four of the protected peptides adopt well-defined tertiary structures, upon removal of the Boc group, only H-Phe-Phe-Phe-Ile-Ile-OMe had the ability to adopt β-structure. Our results indicate that hydrophobic interaction is a very important determinant for self-assembly and presence of charged and aromatic amino acids in a peptide is not necessary for self-assembly.
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ABSTRACT: Hydrogels can be prepared using the commercially available Fmoc-phenylalanine or Fmoc-tyrosine as the gelator. Gelation is triggered by careful adjustment of the pH of the solution using glucono-delta-lactone (GdL). Model dyes have been entrapped in the hydrogels, and the release of the dyes from the hydrogels has been monitored. The release ratios indicate that the systems are under Fickian diffusion control. A range of dyes with different radii of gyration diffuse from the Fmoc-phenylalanine hydrogels with similar diffusion coefficients, implying that the network is not specifically retaining even relatively large (5 nm) dyes. On the other hand, the larger dyes are restricted in their diffusion from Fmoc-tyrosine hydrogels. These results correlate with the rheological measurements for the hydrogels, where those formed from Fmoc-tyrosine were shown to have significantly higher storage moduli than those formed from Fmoc-phenylalanine. In addition, the frequency-dependent behavior of the hydrogels demonstrates that Fmoc-tyrosine shows the classic response of a strong gel with a storage modulus that is nearly independent of frequency. However, for Fmoc-phenylalanine, the frequency dependence of moduli is very strong and very similar to that displayed by a transient network, where the interconnections between junction zones in the network are highly flexible and able to withstand large deformations.Langmuir 07/2009; 25(17):10285-91. · 4.19 Impact Factor
Article: Peptide fibrillization.[show abstract] [hide abstract]
ABSTRACT: The fibrillization of peptides is relevant to many diseases based on the deposition of amyloids. The formation of fibrils is being intensively studied, especially in terms of nanotechnology applications, where fibrillar peptide hydrogels are used for cell scaffolds, as supports for functional and responsive biomaterials, biosensors, and nanowires. This Review is concerned with fundamental aspects of the self-assembly of peptides into fibrils, and discusses both natural amyloid-forming peptides and synthetic materials, including peptide fragments, copolymers, and amphiphiles.Angewandte Chemie International Edition 02/2007; 46(43):8128-47. · 13.73 Impact Factor
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ABSTRACT: Titration of a salt-free solution of native staphylococcal nuclease by HCl leads to an unfolding transition in the vicinity of pH 4, as determined by near- and far-UV circular dichroism. At pH 2-3, the protein is substantially unfolded. The addition of further HCl results in a second transition, this one to a more structured species (the A state) with the properties of an expanded molten globule, namely substantial secondary structure, little or no tertiary structure, relatively compact size as determined by hydrodynamic radius, and the ability to bind the hydrophobic dye 1-anilino-8-naphthalene sulfonic acid. The addition of anions, in the form of neutral salts, to the acid-unfolded state at pH 2 also causes a transition leading to the A state. Fourier transform infrared analysis of the amide I band was used to compare the amount and type of secondary structure in the native and A states. A significant decrease in alpha-helix structure, with a corresponding increase in beta or extended structure, was observed in the A state, compared to the native state. A model to account for such compact denatured states is proposed.Protein Science 08/1993; 2(7):1155-60. · 2.74 Impact Factor