Peptide derivatives (50 nmol) were dissolved in 25 μL of printing solution (70% DMSO, 25% 0.2 M sodium acetate pH 4.5, 5 % glycerol; by vol.) and transferred into 384-well microtiterplates. Two droplets of 0.5 nL peptide solution were deposited per spot on aldehyde functionalized glass slides using the non-contact printer Nanoplotter of GESIM (Großerkmannsdorf, Germany) equipped with 8 piezoelectric NanoTips (GESIM, Großerkmannsdorf, Germany). Printed peptide microarrays were kept at room temperature for 5 hours, washed with deionised water, quenched for 1 hour with 50% aqueous hydroxylamine, washed extensively with water followed by ethanol, and dried under a stream of nitrogen. Each block of 300 peptides was printed in triplicate on each slide. The final physical dimensions of the array were 19.5 X 19.5 mm with each peptide spot having a diameter of ~350 μm and peptide spots being 750 μm apart.
