Self-assembly of short peptides composed of only aliphatic amino acids and a combination of aromatic and aliphatic amino acids
CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India.Journal of Peptide Science (Impact Factor: 1.55). 05/2012; 18(5):283-92. DOI: 10.1002/psc.2395
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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- "From the initial observation that the sequence from A40 i.e., KLXFFAE can form fibrils, nanotubes have been formed from even the sequence FF by introducing conventional peptide chemistry protecting groups  . Nanotubes and nanospheres have also been generated from simple sequences such as II or LII . Similarly, simple di-and tri-peptides have been used for formation of hydrogels [129- 133]. "
ABSTRACT: The process of self-assembly is universal and lies at the heart of biological structures and function. Peptide aggregation, while considered a nuisance in peptide chemistry, soon gained interest with the discovery of pore-forming peptide toxins and had been an area of intense research during last century and even to date. This has also resulted in the increasing use of the more respectable term peptide self-assembly. The discovery of amyloid forming peptides have rekindled the interest in peptide self-assembly since such aggregates are directly implicated in many debilitating diseases in human and animals. Amyloid aggregates have posed many fundamental questions to researchers. In addition, self-assembly of peptides has emerged as a bottoms-up strategy for the fabrication of nanostructures owing to highly ordered nature of the process and considerable degree of flexibility and diversity provided by peptides as starting materials. This review provides a brief account of the progress in the field of peptide self-assembly from pore-forming toxins to amyloid forming peptides and those forming nanostructures.
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ABSTRACT: Self-assembling into aggregates with defined structures is a common phenomenon for many peptides at high concentrations. In this study, we found that when PTP-7b (FLGALFKALSHLL), a concentration-dependent self-assembling peptide, bound to tissue cells and accumulated on cell surfaces, it migrated and self-assembled into exosome-like aggregates at certain locations on the cell membranes. Studies using confocal microscopy and scanning electron microscopy revealed that peptide PTP-7b induced cell tissue damage through a new cell lysis mechanism that involved peptide self-assembly on cell surfaces, extracting lipids from cell membranes, and transporting peptides into the cytoplasm. Peptide self-assembly attributed greatly to peptide-cell interactions and thus the biological activity of a peptide. Because peptide self-assembly was a slow process, PTP-7b-induced cell lysis showed a biphasic behavior: a gradual viability decrease was followed by a rapid decline. These results suggest that peptide self-assembly could be equally as important as charge and secondary structure of a peptide in determining the anticancer and antibacterial activities of therapeutic peptides.
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ABSTRACT: Peptide-based self-assembly offers a unique entry into the construction of soft structures with interesting material properties and functions. Aromatic amino acid-containing peptides are commonly employed as they exhibit high propensity to aggregate due to increased hydrophobic content, promotion of favorable secondary structures, planarity and the possibility of π-π interactions. Incorporation of covalent scaffolds, stimuli-responsive handles and carbohydrate moieties augment beneficial characteristics to the resulting peptide conjugates. These modifications were shown to enforce self-association, elicit stimuli response and achieve improved hydrophilic properties, to name but a few.
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