The excitation-contraction coupling of cardiac muscle is a critical to life in most animals, and errors in E-C coupling contribute to important human diseases (arrhythmia, heart failure, cardiac hypertrophy). Highly specific monoclonal and polyclonal antibodies to proteins critical to cardiac muscle excitation-contraction coupling have been assembled. All of these antibodies have been carefully validated for use in western blotting, in addition, some have also been validated for use in immunofluorescence microscopy and in vitro functional assays. Many of these antibodies recognise the site-specific phosphorylation of target proteins and most have been used in numerous publications in the scientific literature.