Self-association and solubility of peptides. An infrared absorption method for quantitative titration of the extent of self-association in poly(ethylene glycol)-bound peptides

The disruption of the sparingly soluble, self-associated species ( beta -structure) of the polymer-bound, N-protected peptides Boc-L-Ala-Gly-L-Ile-(L-Ala) sub(2)-NHPEG and Boc-(L-Ala) sub(2)-Gly-L-Ile-(L-Ala) sub(2)-NHPEG (PEG = poly(ethylene glycol)) in methylene chloride by increasing amounts of N,N-dimethylformamide or dimethyl sulphoxide has been monitored by following the disappearance of the intense amide 1 or A i.r. bands of the strongly intermolecularly hydrogen-bonded molecules; this suggests the use of this method for the quantitiative titration of the extent of self-association in PEG-bound peptides.