Nonlinear elution chromatography of proteins interactions enable IMAC systems to selectively interact employing the traditional mobile phase modulators in with classes of complementary biopolymers. Although IMAC has been studied using the metal affinity interaction all three amino acids have interactions with the stationmodel (MAIC) in conjunction with the chromatographic ary phase, chromatographic studies on proteins at neumass transport equations. Results indicate that when the tral and alkaline pH have demonstrated that IMAC with feed is loaded under conditions that foster constant pattern formation, isocratic elution leads to Langmuirian pro-immobilized copper distinguishes proteins primarily files at low mobile phase modulator (MPM) concentrabased on their surface histidine content (Sulkowski, tions and a double-plateau profile at high concentrations.
1985). Selectivity in these systems is, therefore, derived A non-self-sharpening protein front during loading, on from the multiplicity, surface accessibility, and variathe other hand, can lead to three plateau profiles or peak tions in the local environment of the histidine sites (pK a splitting and ghost peak formation. Experimental and simulation results on protein separations employing of His groups) (Hemdan et al., 1989). Furthermore, high-affinity modulators suggest that elution with loading differences in molecular size and net charge affect retenin the absence of modulators leads to considerably higher tion in these systems (Rassi and Horvath, 1990).
throughputs and protein concentrations due to the dis-Elution of the adsorbed solutes and hence the separaplacement effects of the modulator as it migrates through tion of protein mixtures can be accomplished by differthe protein zones. Also, for certain separation problems, the operating conditions can be chosen such that the entially modifying the affinities of proteins for the stacomplex modulator system peaks manifest themselves tionary phase. In IMAC, this is typically performed by as spacer displacer; affecting a sharper rear of the earlier either changing the pH of the eluant, i.e., protonation eluting protein and an efficient separation.