Perfluorooctanoic Acid Destabilizes Hemoglobin Structure at Submicromolar Concentrations

Perfluorooctanoic acid's (PFOA) effects on human hemoglobin (Hb) at micromolar and submicromolar PFOA concentrations were investigated using time-correlated single photon counting (TCSPC) fluorescence, native mass spectrometry (NMS), and ion mobility spectrometry (IMS). TCSPC results show that tryptophan fluorescence quenching mechanisms in Hb change from Förster resonance energy transfer (FRET) with the heme to charge transfer to the peptide backbone as the PFOA concentration increases. NMS showed 4 lower and 2 higher affinity sites for PFOA interacting with Hb. At concentrations as low as 10 nM, 2 PFOA molecules bind to Hb, leading to destabilization of the complex, loss of an α subunit, and release of heme. Together, these data show that PFOA alters the biophysical properties of human Hb in ways that suggest allosteric inhibition.