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. Author manuscript; available in PMC: 2010 Jul 25.
Published in final edited form as: Methods Enzymol. 2000;326:245–254. doi: 10.1016/s0076-6879(00)26058-8

Fig. 1.

Fig. 1

Models of the interactions between the polyhistidine affinity tag and two immobilized metal affinity chromatography matrices, (a) The nickel–nitrilotriacetic acid matrix (Ni+2–NTA) [from J. Crowe, H. Döbeli, R. Gentz, E. Hochuli, D. Stüber, and K. Henco, Methods Mol. Biol. 31, 371 (1994)]. (b) The cobalt–carboxylmethylaspartate matrix (Co2+–CMA) (from G. Tchaga, Clontech, personal communication). In both cases, the metal ion exhibits octahedral coordination by four matrix ligands and two histidine side chains, the latter provided by the polyhistidine affinity tag.