glutathione thyrodi cancer Frontiers glutathione colorimetric assay Glutathione peroxidase

Even trace levels of oxygen in cuvettes sealed with parafilm (for measurements performed outside the anaerobic hood) led to the oxidation of Cys-FeS clusters, with the 420 nm signal disappearing over 3 hindicating that the Cys-FeS clusters had broken down

VITAMIN B12 INJECTION Vitamin B12 is an essential water-soluble vitamin that plays a role in many bodily functions

doi: 10.1177/1559325818807382

So the similarity in the constraints of 1-Cys and 2-Cys reduction facilitates this second Cys acquisition step, but an additional constraint is that the second Cys must be the resolving Cys and thus have a higher pKa than the existing Cys