This project is the study of S-nitrosylated proteins in SSM and cytosolic subfractions from heart of sedentary and exercise trained rats. Iodoacetyl Tandem Mass Tag (TMT) and TMT-peptide enrichment coupled with liquid chromatography-tandem mass spectrometry analysis have been used to analyze the modified cysteine residues. Comparisons were performed to reveal the impact of exercise training on protein S-nitrosylation.