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Molecular self-assembly of surfactant-like peptides to form nanotubes and nanovesicles - PubMed

  • ️Tue Jan 01 2002

Molecular self-assembly of surfactant-like peptides to form nanotubes and nanovesicles

Sylvain Vauthey et al. Proc Natl Acad Sci U S A. 2002.

Abstract

Several surfactant-like peptides undergo self-assembly to form nanotubes and nanovesicles having an average diameter of 30-50 nm with a helical twist. The peptide monomer contains 7-8 residues and has a hydrophilic head composed of aspartic acid and a tail of hydrophobic amino acids such as alanine, valine, or leucine. The length of each peptide is approximately equal to 2 nm, similar to that of biological phospholipids. Dynamic light-scattering studies showed structures with very discrete sizes. The distribution becomes broader over time, indicating a very dynamic process of assembly and disassembly. Visualization with transmission electron microscopy of quick-freeze/deep-etch sample preparation revealed a network of open-ended nanotubes and some vesicles, with the latter being able to "fuse" and "bud" out of the former. The structures showed some tail sequence preference. Many three-way junctions that may act as links between the nanotubes have been observed also. Studies of peptide surfactant molecules have significant implications in the design of nonlipid biological surfactants and the understanding of the complexity and dynamics of the self-assembly processes.

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Figures

Figure 1
Figure 1

Space-filling molecular models of surfactant peptide. (A) A6D. (B) V6D. (C) V6D2. (D) L6D2. D (aspartic acid) bears negative charges, and A (alanine), V (valine), and L (leucine) constitute the hydrophobic tails with increasing hydrophobicity. Green, carbons; red, oxygen; blue, nitrogen; white, hydrogen. Each peptide is ≈2–3 nm in length, similar to biological phospholipids.

Figure 2
Figure 2

DLS measurement of surfactant peptide nanostructures. The peptides V6D, V6D2, and A6D gave similar results. Intensity data were collected five times, each looking nearly identical to the rest. The x axis is the size in nanometers, and the y axis is the fraction distribution. The average diameter (D) is ≈30–50 nm. (A) A6D. (B) V6D. The other dimension along the length of the nanotube is beyond the range of DLS measurement.

Figure 3
Figure 3

Quick-freeze/deep-etch TEM image of the surfactant peptides A6D, V6D, V6D2, and L6D2 in water (4.3 mM). These peptides self-assembled into a dense network extended to several micrometers in length. Because the droplet solution containing the peptide nanotubes is in three dimensions, the network of a two-dimensional image appears denser than the actual structure, similar to looking at a picture of the branches on a tree without leaves. (A) A6D. (B) V6D. (C) V6D2. (D) L6D2.

Figure 4
Figure 4

(A) Quick-freeze/deep-etch TEM image of A6D and V6D dissolved in water (4.3 mM at pH 7) at high-resolution. The images show the dimensions, 30–50 nm in diameter with openings of nanotube ends (red arrows). (Inset) Opening ends in more detail. Note some opening ends of the peptide nanotube may be cut vertically. The strong contrast shadow of the platinum coat also suggests the hollow tubular structure. Similar lipid right-handed helical tubular nano- and microstructures have been reported (26, 27). B and C show a three-way junction and many three-way junctions, respectively. There are openings at the ends (D and E, indicated by red arrows), with the other ends possibly buried inside the replica. There also are some vesicles and nanotubes in the upper right corner (E, arrows point to the hollow opening at the ends). Micelles and vesicles are present also. (E) Example of vesicles that are budding off of a nanotube.

Figure 5
Figure 5

Potential pathway of V6D peptide nanotube formation. Each peptide monomer is 2 nm, and the diameter of the modeled bilayer nanotube is 50 nm. Red, hydrophilic head; blue, hydrophobic tail. Each peptide may interact with one another to form closed rings, which in turn stack on top of one another, ultimately yielding a nanotube. Three nanotubes are connected to each other through a three-way junction. This phenomenon mirrors lipid microtubule structures (26, 27).

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References

    1. Whitesides G M, Mathias J P, Seto C T. Science. 1991;254:1312–1319. - PubMed
    1. Lehn J M. Science. 1993;260:1762–1763. - PubMed
    1. Alivisatos A P, Johnsson K P, Peng X, Wilson T E, Loweth C J, Bruchez M P, Jr, Schultz P G. Nature (London) 1996;382:609–611. - PubMed
    1. Mirkin C A, Letsinger R L, Mucic R C, Storhoff J J. Nature (London) 1996;382:607–609. - PubMed
    1. Langer R S, Vacanti J P. Science. 1993;260:920–926. - PubMed

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