l-Histidine enhances stability of hemoglobin concentrates by coordinating with free iron

The objective of this investigation was to evaluate the effects of l-histidine on the stability of porcine hemoglobin concentrates during storage. The results indicated that the addition of l-histidine increased the oxyhemoglobin content and a* values but decreased the methemoglobin content and free iron content (P < 0.05) during storage. The addition of iron cation decreased both the oxyhemoglobin content and a* values but increased both the methemoglobin content and free iron concentration (P < 0.05). CD spectra revealed that the free iron content induced the transformation of the hemoglobin secondary structure from an α-helix (close structure) to a β-pleated, β-turn, and random coil arrangement (loose structure), while l-histidine weakened this behavior of the free iron. Infrared spectra demonstrated that the l-histidine coordinated with the free iron (Fe2 + or Fe3 +) to give the corresponding complex at 25 °C and pH 7.3. Therefore, l-histidine enhanced the stability of hemoglobin concentrates by coordinating with free iron.