Synthesis and fluorescent labeling of beta-amyloid peptides

Fluorescent cell analytical techniques require the incorporation of a fluor ophore into the target molecule without causing a significant change in the native conformation. Many short peptides have a limited number of reactive groups that can be labeled without affecting the biological activity. In t his work we present several methods for labeling beta -amyloid peptides (be taA[25-35], betaA[1-40]) and their derivatives (LPFFD. RIIGL and RVVIA) wit h different chromophores exclusively at the N-terminus. In the case of liqu id-phase labeling, fluorescein isothiocyanate was used. The side-chain amin o function of Lys, if present in the sequence, was protected with an Fmoc g roup, whereby the hydrophobic character of the peptide was further increase d. The labeling reaction was carried out in an appropriate deaggregating so lvent, DMSO. For solid-phase labeling, 5(6)-carboxyfluorescein and 7-amino- 4-methyl-3-coumarinylacetic acid were applied. Several cleavage cocktails w ere tested for removal of the labeled amyloid peptides from the resin in or der to completely suppress the oxidation of Met. Copyright (C) 2001 Europea n Peptide Society and John Wiley & Sons, Ltd.