After the discovery of soft ionization techniques including MALDI and electrospray, proteomics became a very popular analytical tool for identification and quantification of proteins. MALDI ionization is a very popular technique due to its speed, simplicity of sample preparation and higher tolerance to salts and other impurities. Many different proteases, more or less specific, are used to digest protein or complex proteins mixtures. The most widely used protease is trypsin, mainly for its high specificity, low cost and relative robustness. Other proteases such as chymotrypsin, pepsin, endoproteinase GluC, etc. are also very often used in cases, where trypsin does not allow forming of appropriate peptides.
Functionalized MALDI targets modified with different types of proteases offer an alternative approach to conventional methods. Protein digestion occurs directly on the target and is mainly used for fast pre-screening of protein of interest. AffiPro offers now modified MALDI targets with trypsin or pepsin proteases. Preparation of customized MALDI targets with other proteases is also possible.