Self-assembly of short peptides composed of only aliphatic amino acids and a combination of aromatic and aliphatic amino acids.

Chilukuri Subbalakshmi, Sunkara V Manorama, Ramakrishnan Nagaraj

CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India.

Journal of peptide science : an official publication of the European Peptide Society 2012 May

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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. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.

Citation

Chilukuri Subbalakshmi, Sunkara V Manorama, Ramakrishnan Nagaraj. Self-assembly of short peptides composed of only aliphatic amino acids and a combination of aromatic and aliphatic amino acids. Journal of peptide science : an official publication of the European Peptide Society. 2012 May;18(5):283-92