α-cyano-4-hydroxycinnamic acid affinity sample preparation.: A protocol for MALDI-MS peptide analysis in proteomics

We present a new MALDI sample preparation technique for peptide analysis using the matrix alpha -cyano-4-hydroxycinnamic acid (CHCA) and prestructured sample supports. The preparation integrates sample purification, based on the affinity of microcrystalline CHCA for peptides, thereby simplifying the analysis of crude peptide mixtures. Enzymatic digests can thus be prepared directly, without preceding purification. Prepared samples are homogeneous, facilitating automatic spectra acquisition, This method allows preparation of large numbers of samples with little effort and without the need for automation. These features make the described preparation suitable for cost-efficient high-throughput protein identification. Performance of the sample preparation is demonstrated with in situ proteolytic digests of human brain proteins separated by two-dimensional gel electrophoresis.