Objective: To determine the free thiols in the chimeric protein PfCP-2.9 of Plasmodium falciparum expressed by Pichia pastoris.
Methods: Two experiments of reverse phase HPLC and Ellman's reaction were applied to the PfCP-2.9 for the determination of its free thiols. For RP-HPLC analysis, three kinds of samples were tested: PfCP-2.9, dithiothreitol-reduced PfCP-2.9 and indoacetic acid-alkylated PfCP-2.9.
Results: Both experiments showed that there were no any free thiols present in the PfCP-2.9.
Conclusion: The disulfide bonds between cysteine residues of PfCP-2.9 were formed completely.