Abstract
Interferons of human, mouse, and rabbit origin bind to straight chain hydrocarbons immobilized on agarose. The hydrophobic nature of binding is established by the following observations: (a) a positive correlation between the length of hydrocarbon ligand and the strength of interaction; (b) a stronger interaction with hydrocarbon ligands terminated with apolar rather than polar head groups; (c) a lack of dependence of binding on ionic strength and pH of the solvent; (d) a reversal of binding by ethylene glycol, a hydrophobic solute; (e) an increasing eluting efficacy of tetraalkylammonium ions with the length of their alkyl substituents. The hydrophobic interactions of human interferon underlie the efficiency of two-step chromatographic procedures. For example, human embryo kidney interferon can be purified about 3,600-fold by sequential chromatography on (a) concanavalin A-agarose, (b) octyl-agarose. Another two-step procedure: (a) concanavalin A-agarose, (b) L-tryptophan-agarose, gives about 10,000-fold purification. The overall recovery of interferon in both cases in close to 90%.
Highlights
Interferons of human, mouse, and rabbit origin bind to straight chain hydrocarbons immobilized on agarose
As the immobilization of the ligands, through their primary amino groups, to cyanogen bromide activated agarose results in a positive charge on agarose matrix
When the immobilized ligand carries a polar head group the capacity of the ligand to act as an anion exchanger is clearly increased
Summary
Interferons of human, mouse, and rabbit origin bind to straight chain hydrocarbons immobilized on agarose. Additional characterization of the intrinsic hydrophobicity of the interferon molecule required, ligands less prone to conformational distortions either during immobilization or upon their exposure to extreme solvent conditions. Both of these requirements were met, in principle, by our later finding that human fibroblast interferon would bind to wcarboxypentyl-agarose in a solvent of high ionic strength (1 M NaCl) and could be readily displaced from the sorbent by ethylene glycol [4]. In this report we establish a positive correlation between the strength of binding of interferon and the length of the hydrocarbon ligand, which allows the characterization of the interaction as hydrophobic [5]. Pends on the length of their alkyl arms: tetramethyl- and tetraethylammonium ions are ineffective whereas tetrapropyland tetrabutylammonium ions, at the same molar concentration as the first two, are efficient eluants
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