Self-assembling amphiphilic peptides

Abstract

The self-assembly of several classes of amphiphilic peptides is reviewed, and selected applications are discussed. We discuss recent work on the self-assembly of lipopeptides, surfactant-like peptides and amyloid peptides derived from the amyloid-β peptide. The influence of environmental variables such as pH and temperature on aggregate nanostructure is discussed. Enzyme-induced remodelling due to peptide cleavage and nanostructure control through photocleavage or photo-cross-linking are also considered. Lastly, selected applications of amphiphilic peptides in biomedicine and materials science are outlined.

Keywords: amphiphilic peptides; amyloid peptides; self-assembly; surfactant-like peptides.

Figure 1

The four domains in a PA molecule that are required for self-assembly in a functional system .

Figure 2

Cylindrical nanofibre formed as a result of the aggregation of individual PA molecules (with an IKVAV pentapeptide head group) above a critical aggregation concentration .

Figure 3

Schematic representation of the self-assembly of a PA forming a nanobelt exhibiting grooves on its surface .

Figure 4

Model of stacked disc-like micelles for a PA comprising two C₁₄ alkyl chains and a collagen-based peptide, consistent with fitting of small-angle neutron scattering data .

Figure 5

Negative stain TEM image showing tape nanostructures for a 2 : 1(wt% : wt%) C₁₆-KTTKS : C₁₆-ETTES mixture . The scale bar represents 1 µm.

Figure 6

Introduction of an N-terminal alkyl chain enables the self-assembly of a PEG/peptide containing an N-terminal KTVIIE sequence along with a photocleavable linker (top); exposure to UV light then causes disassembly (bottom) when the alkyl chain is cleaved . Courtesy of D. Löwik.

Figure 7

Thermoreversible transition between nanotubes/helical ribbons and twisted tapes for the PA shown .

Figure 8

Dependence of morphology of C₁₆-KTTKS on pH . (A) Atomic force microscopy (AFM) image of 1 wt% C₁₆-KTTKS at pH 2. (B) The height distribution for spherical micelles extracted on the AFM images of 1 wt% C₁₆-KTTKS at pH 2. AFM images of 1 wt% C₁₆-KTTKS at (C) native pH 3, (D) pH 4 and (E) pH 7. (F) The longitudinal height profiles of the structures observed for 1 wt% C₁₆-KTTKS at native pH 3 (blue curve), at pH 4 (black curve) and at pH 7 (red curve). Z scale for the AFM images is 6 nm for (A) and 60 nm for (C–E).

Figure 9

Cryo-TEM images for solutions containing 1 wt% of (A) C₁₆-KKFFVLK, (B) C₁₆-KKFF, (C) C₁₆-KKF, (D) FVLK and (E) VLK .

Figure 10

Model for the structure of A₆K nanotubes based on information from small-angle scattering, isotope-edited FTIR and solid-state NMR experiments .

Figure 11

The KLVFF sequence in the Aβ40/Aβ42 primary sequence.

Figure 12

Model for the assembly of β-sheets of KLVFFAE into nanotubes . (A) A flat rectangular bilayer, (B) coiled tubular fibril with helical patch of 214 nm, (C) top view of nanotube and (D,E) details of molecular packing in nanotube wall. Figure courtesy of D. Lynn, based on Ref. .

Figure 13

Schematic of the bilayer structure produced in C₁₆-KTTKS self-assembly .