We describe the design and properties of cyanine dye-peptide conjugates synthesized on solid supports for screening assays. With this approach, we demonstrate the feasibility of including a diagnostic molecule into a spot synthesis of membrane-bound peptide libraries in order to permit screening of complete dye-peptide conjugates for their potential as fluorescent contrast agents in biomedical optical imaging. A cellulose support, which is modified with a linker permitting cleavage of the dye-peptide conjugates from the support, was prepared. The attachment of dyes to the peptides is exemplified with carboxy-substituted indotricarbocyanines, which can be covalently linked to the N-terminal amino group or a lysin in the course of the synthesis. Several dye-peptide conjugates were obtained by automated peptide synthesis on resins. Furthermore, model sequences consisting of up to 11 amino acids were synthesized on cellulose in sufficient amounts and purity, thus permitting direct testing of these compounds in cell- based assays and fluorescence microscopy. The dyes show only negligible alterations in their absorption and fluorescence properties when attached to low molecular weight peptides. In conclusion, membrane-bound peptide libraries provide a powerful tool to generate large diversities of dye-labeled peptides and to make these compounds available for biological screening assays.
|