Aggregation of adult and fetal hemoglobin by ingested nitrate anions

Abstract

The ingested nitrates sourced from tap water, food, chemicals and pharmaceuticals are<br />converted to nitrites in the body surfaces by bacteria and then, the nitrite ions can lead the<br />structural changing in hemoglobin. In the present work, aggregation of the purified hemoglobin<br />in adult (HbA) and in fetus or newborn (HbF) in the presence of nitrite ions were studied.<br />Hemoglobin aggregation was performed chemically in the presence of 10 mg/l nitrite ions and<br />examined by UV-Vis spectrophotometer at 360 nm wavelength. The extrinsic fluorimetric<br />measurements indicated that repulsive electrostatic interaction between nitrite anions and<br />negative charged groups of both types of HbA and HbF molecules leads to expose the<br />hydrophobic patch of the protein molecules. Moreover, the α-helix to β-strand transition in both<br />types of hemoglobins shown by circular dichroism support aggregation process among this<br />protein. However, at natural pH, the protonated amino group of Gly in HbF tends to bind to<br />nitrite anions more than the unprotonated forms of Val residue in HbA. The drastic slop of<br />aggregation plot and shorter lag time of HbF relative to HbA demonstrated more aggregation of<br />former protein.