3740 Bull. Korean Chem. Soc. 2010, Vol. 31, No. 12 Liang Wang and Xiao-jun Zhao
DOI 10.5012/bkcs.2010.31.12.3740
Investigation of Self-assembly Structure and Properties
of a Novel Designed Lego-type Peptide with Double Amphiphilic Surfaces
Liang Wang and Xiao-jun Zhao†,*
West China Hospital Nanomedicine Laboratory, Center for Regenerative Medicine and Institute for Nanobiomedical
Technology and Membrane Biology, West China Hospital, Sichuan University, Chengdu 610065, Sichuan, China
†Center for Biomedical Engineering, NE47-379, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
Received July 22, 2010, Accepted October 19, 2010
A typically designed ‘Peptide Lego’ has two distinct surfaces: a hydrophilic side that contains the complete charge
distribution and a hydrophobic side. In this article, we describe the fabrication of a unique lego-type peptide with the
AEAEYAKAK sequence. The novel peptide with double amphiphilic surfaces is different from typical peptides due
to special arrangement of the residues. The results of CD, FT-IR, AFM and DLS demonstrate that the peptide with
the random coil characteristic was able to form stable nanostructures that were mediated by non-covalent interactions
in an aqueous solution. The data further indicated that despite its different structure, the peptide was able to undergo
self-assembly similar to a typical peptide. In addition, the use of hydrophobic pyrene as a model allowed the peptide
to provide a new type of potential nanomaterial for drug delivery. These efforts collectively open up a new direction
in the fabrication of nanomaterials that are more perfect and versatile.
Key Words: Self-assembly structure and properties, Lego-type peptide, Amphiphilic surfaces, Pyrene, Fluorescence
Introduction
The self-assembly phenomenon, which is ubiquitous in nature,
is the result of biological evolution. A large number of biologically
functional macromolecules and organisms are accomplished
through self-assembly. The development of self-assembling
peptides is quickly becoming the most emerging nanoscale field
and has gained rapid pace in recent years. It has prompted numerous
studies of peptides such as lego-type peptides, peptide
surfactants and peptide ink.1-3 ‘Peptide Lego’ forms well-ordered
nanofiber scaffolds for 3D cell culture and for regenerative
medicine. ‘Peptide surfactants’ are used for drug, protein and
gene delivery as well as for solubilizing and stabilizing membrane
proteins. ‘Peptide ink’ plays an important role in surface
biological engineering.4-9
In this work, we focus on the molecular-designed ‘Peptide
Lego’, discovered from a segment in a left-handed Z-DNA binding
protein in yeast, which can be programmed for self-assembly
in well-formed structures.10 Typical sequences of artificially
fabricated lego-type peptides show regular repeats of alternating
hydrophobic and hydrophilic residues along the complete sequence
of the peptide, and the hydrophilic residues possess alternating
positive and negative amino acids. This special arrangement
of the residues gives the peptides two distinct surfaces: a
hydrophilic side with the complete charge distribution and a
hydrophobic side.11 These peptides exhibit the characteristic
of beta-sheet structures and self-assemble into three-dimensional
nanofiber scaffolds in water.12-15
In this project, we have followed traditional ideas for the
fabrication of designer peptides to fabricate an amphiphilic peptide
with a unique architecture. Our novel lego-type peptide
consisted of 9 amino acids and was designed with two amphiphilic
surfaces. With regard to the sequence of the peptide,
alanine was designed as the hydrophobic backbone whereas
Glu and Lys formed the hydrophilic district that provided ionic
bonds in regular repeats. We designed the peptide with the Tyr
amino acid and without the full-sequence ionic complements
between the repeats of Ala-Glu and Ala-Lys. The introduction
of Tyr mediated the charge residues distributed on both sides
of the backbone to form a molecule with two amphiphilic surfaces,
which is different from a typical molecule. In addition,
the aromatic interactions may play a key role in the formation
of nanostructures because they contribute free energy of formation,
order and directionality to the self-assembly process.16
To detect its ability to spontaneously assemble into well-ordered
nanostructures, we used CD, FT-IR AFM and DLS to investigate
the self-assembly properties and behavior of the novel
nanomaterial. As the results indicate, the novel peptide was able
to undergo self-assembly and form a stable nanostructure in an
aqueous solution. In addition, the investigation of the hydrophobic
district demonstrated that the novel designed peptide
was able to provide a new type of nanomaterial for delivering
hydrophobic drugs. These efforts collectively open up a new
direction in the fabrication of novel amphiphilic self-assembly
peptides..........
