Cayman’s S-Nitrosylated Protein Detection Kit (Biotin Switch) employs a modification of the Jaffrey et al. 'Biotin-switch' method to allow for the direct visualization of S-nitrosylated proteins in whole cells or tissues, as well as by WB analysis. Using this method, free SH groups are first blocked (an addition of 125.1 amu per residue) and any S-NO bonds present in the sample are then cleaved. Biotinylation of the newly formed SH groups (an addition of 523.6 amu per residue) provides the basis for visualization using streptavidin-based colorimetric or fluorescence detection.