Patent ID: 8633300

Claim:
A method for selective reduction of an engineered protein in its active conformation comprising at least one non-native cysteine, said protein comprising one or more cysteine moieties conjugated through a disulfide bridge to a low-molecular weight thiol (RS-Cys), said moiety/moieties not being involved in intramolecular S—S bridges (Cys-S—S-Cys) when the protein is in its active form, the method comprising the step of allowing the low-molecular weight thiol-conjugated protein to react with a mixture comprising a redox buffer under non-denaturing conditions, wherein the redox buffer is a redox pair of reduced and oxidized glutathione, the concentration of the reduced glutathione is in the range of 0.01-50 mM, and the concentration of the oxidized glutathione is in the range of 0.001-2 mM, and wherein the engineered protein is a Factor VII polypeptide.