Oligomerization of di-D-amino acid substituted peptides
Photo-induced cross-linking of unmodified proteins (PICUP) was used to stabilize oligomer states, allowing quantitative determination of the oligomer size frequency distribution using SDS-PAGE, silver staining, and densitometry (for a review see 32). produced an oligomer distribution comprising predominately dimers and trimers, with progressively fewer tetramers and pentamers (Fig. 2; Aβ40, lane ”Aβ”). Several D-substituted peptides displayed altered oligomer distributions. For example, D-[H14,Q15]11For ease of reference, we refer to particular peptides by specifying only the position(s) of D-amino acids. Thus D-[H14,Q15] refers to a full-length Aβ peptide containing D-His14 and D-Q15. displayed a prominent band with a mobility greater than that of monomer, as well as a more diffuse and fainter tetramer band (Fig. 2, red arrow). oligomer distribution of D-[K16,L17] was shifted to higher oligomer orders, as evidenced by a more prominent pentamer band, a diffuse hexamer band, and poorly resolved higher order bands. D-[A30,I31], like D-[K16,L17], had an oligomer distribution shifted to higher orders, but in this case, bands were distinct, not smeared. D-[A30,I31] showed substantial smearing between trimer and tetramer.