The goal of this study was to relate conformational changes in the N-terminal domain of chicken troponin I (TnI) to Ca 2+ activation of the actin–myosin two cysteine residues in this region (Cys48 and Cys64) were labeled with two sulfhydryl-reactive pyrene-containing fluorophores [N-(1-pyrene)maleimide, and N-(1-pyrene)-iodoacetamide].The labeled TnI showed a typical fluores-cence spectrum: two sharp peaks of monomer fluorescence and a broad peak of excimer fluorescence arising from the formation of an excited dimer (excimer)
