Raman microspectroscopy was applied to monitor porphyrin perturbation associated with the tense-relaxed (T --> R) state transition of hemoglobin (Hb) within a single red blood cell. The spectra exhibited dramatic changes in the spin state region (1650-1500 cm(-1)) and the methine C-H deformation region (1250-1200 cm(-1)) between the 27- and 54-min interval following reoxygenation. Principal components analysis revealed a sigmoidal curve when the PC1 scores versus time were plotted. The inflection point on the curve corresponded to the T --> R transition point spectrum, indicating the cell is composed of Hb in a mixture of spin states. The results of this work illustrate the dynamics of porphyrin perturbation during erythrocyte respiration and may have applications in the diagnosis and treatment of red blood cell disorders including thalassemia and sickle cell anemia.
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