Interaction of human hemoglobin and its variants with Agar

In citrate agar electrophoresis hemoglobin appears to bind reversibly to the sulfated polysaccharide agaropectin, a natural component of Difco Bacto-Agar. This complex migrates anodally, since the hemoglobin is only weakly positively charged at pH 6.2 whereas the carbohydrate carries a net negative charge. Electroendosmosis, on the other hand, proceeds in the cathodal direction. These opposing fluxes separate the hemoglobins in the order of their affinity for agaropectin. An agaropectin binding site was identified on hemoglobin by computer-assisted modeling, and the relation of the site to hemoglobin variants that exhibit abnormal citrate agar mobility was established. The citrate anion is postulated to function as a "counter ion." Preliminary evidence indicates that agaropectin has antigelling properties with respect to hemoglobin S.