A comparative study of in-gel digestions using microwave and pressure-accelerated technologies

One of the most popular methods to prepare tryptic peptides for bottom-up proteomic analysis is in-gel digestion. To date, there have been few studies comparing various digestion methods. In this study, we compare the efficiency of several popular in-gel digestion methods, along with new technologies that may improve digestion efficiency, using a human epidermoid carcinoma cell lysate protein standard. The efficiency of each protocol was based on the average number of proteins identified and their respective sequence coverage and relative quantitation using spectral counting. The importance of this study lies in its comparison of pre-existing in-gel digestion methods with those that use newly developed technologies that may introduce the potential for a more cost-effective digestion, higher protein yield, and an overall reduction in processing time. The following four protocols were compared: an overnight in-gel digestion protocol; an overnight in-gel digestion protocol, in which we remove the vacuum centrifugation steps; in-gel digestion in a barometric pressure cycler; and in-gel digestion in a scientific microwave. Several variables were tested for increased digestion efficiency and decreased keratin contamination. Statistical analysis was performed on replicate samples to determine significant differences between protocols.