Determination of the oxido-redox status of plasma albumin in hemodialysis patients

The oxido-redox status of plasma albumin in patients treated with hemodialysis was characterized with LC–ESI-MS/MS and was compared with models of oxidative stress. Oxidised albumin was characterized by sulfonation (SO3−) of the SH at Cys 34, unfolding and acidification of the molecule. Albumin in hemodialysis patients presented, instead, only intermediate oxidation products such as sulfenic (SO2), sulfonic (SO) and methionine sulfoxide (C5H9NO2S) involving Cys 165–269 and Met 329–548 but did not present SO3− at Cys 34. Absence of charge and structural alterations compared to the oxidised templates was also confirmed with electrophoretic titration and calorimetry. In conclusion, the oxido-redox status of plasma albumin in hemodialysis patients lacks the hallmarks of the advanced oxidation products. LC–ESI-MS/MS was crucial to characterize albumin in conditions of oxidation stress; surrogate techniques can mirror conformational changes induced by oxidation.