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Published 1991 | public
Journal Article

Chiral copper—chelate complexes alter selectivities in metal affinity protein partitioning


Proteins can be distinguished by exploiting complementarity between a histidine's microenvironment and a metal—chelate ligand in metal-affinity separations. The partitioning behavior of three myoglobins was investigated in aqueous two-phase polyethylene glycol—dextran systems containing polyethylene glycol derivatized with Cu(II) complexes of the l- and d-isomers of methionine and aspartate. TSK chromatographic supports derivatized with the methionine complexes were used to study retention of these proteins in metal-affinity chromatography. In partitioning studies, the amino acid metal chelates exhibit selectivities for the myoglobins that are different from that of Cu(II)-iminodiacetate. Significant differences in selectivity based on the chiral nature of the amino acid complexes were also obsrved. The chromatographic selectivities of the chelating ligands exhibit little variation, however, suggesting that interactions occuring in solution but not on a surface play an important role in protein binding to the Cu(II)-aminoa acid-PEG complexes. In solution, the Cu(II)-amino acid complexes are sensitive probes of the microenvironments of surface histidines. The choice of the metal chelate affinity ligand offers a powerful means by which the selecitivity of metal-affinity separations can be altered.

Additional Information

© 1991 Published by Elsevier B.V. Received 13 December 1990. This research is supported by the National Science Foundation, Grant No. EET-8807351, and a NSF Presidential Young Investigator Award. F.H.A. is the recipient of a David and Lucile Packard Foundation Fellowship. E.W. is the recipient of a Caltech Summer Undergraduate Research Fellowship. R.T. acknowledges the support of a predoctoral training fellowship in biotechnology from the National Institute of General Medical Sciences, NRSA 1 T32 GM 08346-01, Pharmacology Sciences Program.

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