Nematic and columnar ordering of a PEG-peptide conjugate in aqueous solution.
The self-assembly in aqueous solution of a PEG-peptide conjugate is studied by spectroscopy, electron microscopy, rheology and small-angle X-ray and neutron scattering (SAXS and SANS). The peptide fragment, FFKLVFF is based on fragment KLVFF of the amyloid beta-peptide, Abeta(16-20), extended by two hydrophobic phenylalanine units. This is conjugated to PEG which confers water solubility and leads to distinct self-assembled structures. Small-angle scattering reveals the formation of cylindrical fibrils comprising a peptide core and PEG corona. This constrained structure leads to a model parallel beta-sheet self-assembled structure with a radial arrangement of beta sheets. On increasing concentration, successively nematic and hexagonal columnar phases are formed. The flow-induced alignment of both structures was studied in situ by SANS using a Couette cell. Shear-induced alignment is responsible for the shear thinning behaviour observed by dynamic shear rheometry. Incomplete recovery of moduli after cessation of shear is consistent with the observation from SANS of retained orientation in the sample.
Hamley
Ian W
IW
Department of Chemistry, University of Reading, Whiteknights, Reading, UK. I.W.Hamley@reading.ac.uk
Krysmann
Marta J
MJ
Kelarakis
Antonios
A
Castelletto
Valeria
V
Noirez
Laurence
L
Hule
Rohan A
RA
Pochan
Darrin J
DJ
D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000138:chemical synthesis / Q000737:chemistry*; D053838:Scattering, Small Angle; D017550:Spectroscopy, Fourier Transform Infrared
D010455:Peptides; D011092:Polyethylene Glycols