Unfolding Pathway of Apomyoglobin: Simultaneous Characterization of Acidic Conformational States by Frequency Domain Fluorometry

摘要: The dynamic properties of the conformational states co-existing during acid-induced unfolding tuna apomyoglobin, a single tryptophan-containing protein, have been investigated simultaneously by frequency domain fluorometry. In transition region, in absence salt, tryptophanyl fluorescence emission arises from bimodal lifetime distribution. pH decrease causes marked broadening short-lived distribution component whereas other component, i.e. long-lived one, remains unchanged and represented very narrow whose width is similar to that native protein. observed on lowering indicated this fully unfolded molecules. This was further corroborated acrylamide quenching studies at acidic pH. collisional rate constant 8·9 × 109 M-1 s-1, found be for exposed residue. characterized lower constant, i.e.2·3 s-1. value if compared determined apoprotein neutral pH, 4·0 108 indicates native-like structure surviving possesses large molecular flexibility.