Fig. 1

Schematic of the preparation of synthesis surfaces for the laser printer-based peptide microarray synthesis and schematic of a synthesis cycle in the combinatorial synthesis. i) Cleaned and activated glass substrates are silanized with 2-bromo-N-(3-triethoxysilyl)propyl isobutyramide to provide an initiator for the atom transfer radical polymerization (ATRP). ii) The ATRP with PEGMA and MMA yields a graft polymer coating which is covalently linked to the glass substrate (silane and MMA backbone are depicted as a sidled line). iii) The hydroxyl groups in the PEG side chains are esterified with Fmoc-β-alanine to provide amino groups for the peptide synthesis. Synthesis cycle: a) Microparticles containing the N-terminally Fmoc protected and C-terminally Opfp activated amino acids are deposited on the synthesis support. b) Heating of the slide leads to melting of the polymeric particle matrix and, thus, gives viscous reaction spheres in which the amino acids can couple to the amino groups on the slide. c) Routine washing removes microparticle residues such as matrix material and unreacted amino acids. Capping of unreacted amino groups on the surface helps to avoid formation of incorrect peptide sequences. d) Removal of the N-terminal Fmoc protecting groups renders new amino groups for the next synthesis cycle