Glossoscolex paulistus hemoglobin with fluorescein isothiocyanate: Steady-state and time-resolved fluorescence

•Fluorescein isothiocyanate (FITC) binds to Glossocolex paulistus hemoglobin (HbGp) at pH 7.0.•Protein/heme molar ratios of 0.2 and 2.0 lead to 0.12 and 0.79 FITC molecules bound per heme.•Protein tryptophans emission show greater sensitivity to urea as compared to FITC emission.•Time-resolved fluorescence decays were studied for both protein tryptophans and bound FITC.•Fluorescence anisotropy decays show two rotational correlation times for HbGp-bound FITC.