A Thiolomic Approach to Map Free Thiol Distribution in Food Proteins

Thiolomics aims to map the distribution of total free cysteine thiol groups among proteins in any biological system, including proteins in process-reticulated food networks. Proteins—either native or unfolded—are labeled with a fluorescent probe specific for free thiols (i.e., 5-(iodoacetamido)fluorescein) and then separated by electrophoresis (SDS-PAGE or 2D-PAGE). The fluorescent pattern is directly acquired at the end of the electrophoretic separation, and the gel may be subsequently stained for the total protein pattern. The patterns acquired on the same gel (i.e., fluorescence and total proteins) are then compared to individuate labeled proteins. This contribution discusses an example of the application of a thiolomic approach to the characterization of wheat protein fractions (albumins/globulins; gliadins; and glutenins). In this example, after thiol labeling, individual proteins are separated by and profiled by mono- and bi-dimensional electrophoresis.