Aggregation of adult and fetal hemoglobin by ingested nitrate anions

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