Affinity Chromatography of Hemoglobin on Cross-Linked Amylose

New packing materials for protein chromatography

This review describes new packing materials designed for protein chromatography, covering advances in base supports and stationary phases. Base supports are classified according to their chemical composition. Since most separation media are bead shaped, typical procedures used for their preparation are also presented. In order to provide matrices combining improved chemical stability and chromatographic performances, composite materials continue to be developed, including bonded stationary phases, pore composites and mixed carriers. The different approaches to their preparation are described and characteristics that play a major role in the chromatographic process are discussed. Recently introduced materials and some of their applications under non-denaturing conditions in the different chromatographic modes are also presented.

New support for the affinity chromatography of hemoglobin

A new support for affinity chromatography of hemoglobin was synthesised from EAH Sepharose-4B containing a hexamethylamine spacer. Benzenetetracarboxylic (BTC) or benzenehexacarboxylic (BHC) acids were covalently bound to the spacer arm. At pH close to the pI of the protein, the biospecificity of the support due to the interactions of the allosteric site of hemoglobin with immobilised polyanionic ligands was proved. When the allosteric site was blocked by covalently linked pyridoxalphosphate, the protein showed no more affinity for the support. Further investigations were done on the BHC support; the association constants between BHC support and the hemoglobin forms, oxyhemoglobin and deoxyhemoglobin, were determined. The deoxyhemoglobin affinity was ten times higher than that of oxyhemoglobin, both for fixed and for free ligand. The following values of binding constants K(PX) and K(PL) (1 mol(-1)) with fixed or free ligand respectively were found: for oxyhemoglobin, K(PX)=8.0x10(2), K(PL)=1.4x10(4); for deoxyhemoglobin, K(PX)=9.7x10(4), K(PL)=2.3x10(5). The BHC support capacity was about 4.7x10(-5) mol hemoglobin g(-1) of dry gel corresponding to 1.5x10(-6) mol hemoglobin g(-1) of hydrated gel or 0.1 g hemoglobin g(-1) of hydrated gel.

Specific hemoglobin (poly)saccharide recognition

Hemoglobin (Hb) is not a glycoprotein but can easily be glycosylated by a non-enzymatic mechanism. Based on some kinetic particularities, consisting in a faster glycosylation of the amine terminal group of the beta-chain located on the allosteric site, a hypothesis of a recognition center for specific sugars has been advanced. Affinity chromatography materials based on epichlorohydrin crosslinked amylose, agarose and dextran (Sephadex), were used. A specific interaction with the CL-amylose (alpha-1,4-glycosidic links) was found, while for Sephadex (alpha-1,6-glycosidic links), no Hb retention was observed. An affinity retention of hemoglobins (human and bovine) on agarose (a galactose containing carbohydrate) has also been established. Chromatographic studies of Hb competitive elution with several monosaccharides (glucose, fructose, galactose) and disaccharides (saccharose, cellobiose, maltose, lactose) indicated that Hb retained by affinity onto CL-amylose columns, can be eluted only with galactose and lactose; with the other tested saccharides, very poor or no desorption at all, has been observed. These new data suggest: (1) a selective recognition of a limited number of (poly)saccharidic materials; and (2) a different behavior towards various sugars, the best interaction being observed with galactose-containing sugars (lactose). These aspects fit well with the hypothesis of a hemoglobin recognition center for sugars.