RESUMO
In order to remove immunoglobulins from adult bovine serum (ABS), adsorptions were carried out in suspension with thiophilic adsorbents without (T-gel) and with (ST-gels) short amine spacer. The developed ST-gels could be cleaned in sodium hydroxide and specifically adsorbed immunoglobulins from ABS at a lower ionic strength of the adsorption buffer than a T-gel. The ST-gels are suited for the performance of adsorptions in a suspension with a high concentration of the adsorbent. For an almost complete removal of immunoglobulins from ABS in 0.5 M potassium sulfate and 0.1 M potassium phosphate (pH 7), up to 75 g ST-gel per 1 suspension may process up to 100 ml ABS. The synthesized ST-gels contained an equal amount of amine spacers and sulfone groups. The ratio between coupled 2-mercaptoethanol molecules and sulfone groups was about 0.4. In comparison with the T-gel, the chemical stability of the ST-gels in solutions of 0.1 to 1 M sodium hydroxide was higher. The capacity for adsorbing pure immunoglobulins of the T-gel was 0.329 g g-1 (10.9 g l-1) and of the ST2-gel, 0.677 g g1 (52.3 g l-1). The capacity for adsorbing IgG from ABS of the T-gel was 0.177 g g1 (5.88 g l-1) and of the ST2-gel, 0.152 g g-1 (11.7 g l-1). This reduced capacity was attributed to a low affinity binding to the adsorbents of other proteins from ABS. When an incubation of the adsorbent with ABS was performed in 0.5 M potassium sulfate and 0.1 M potassium phosphate (pH 7), the affinity constant (Ka) for IgG of the T-gel was 2.5 x 10(6) M-1 and of the ST-gel, 3.1 x 10(7) M-1. In this adsorption buffer at a protein concentration above 5 g l-1, salt-promoted precipitation of IgG took place. When an adsorption was performed at the minimal ionic strength of the adsorption buffer, the Ka of the T-gel for IgG was about 9 x 10(3) M-1 and of the ST-gel, about 2.3 x 10(5) M-1. In this case, the removal of Igs from ABS was achieved by means of a partition equilibrium, rather than by high affinity adsorption.
