Abstract
Polyaminostyrene, and diazopolystyrene quenched with β-naphthol bound insulin in a manner of physical adsorption (polyaminostyrene-insulin, PAS-I and β-naphthyl-azo-polystyrene-insulin, β-NAS-I, respectively). The properties of these physically modified insulin preparations were compared with that of polystyrene-azo-insulin (PAI), in which insulin was coupled chemically by azo linkages, and following results were obtained:
1). The insulin content of these preparations was found to be 50 to 70 mg/g of PAS-I, 80 to 100 mg/g of β-NAS-I and 130 to 170 mg/g of PAI. The biological activities of PAS-I, β-NAS-I and PAI were about 70, 40 and 40% of the original value, respectively.
2). By a successive washing with mild acid, insulin was unbound from its physical binding to polyaminostyrene (PAS-I). The biological activity of β-NAS-I was reduced to 10 to 20% of the original value after liberating about one forth of insulin by mild acid treatment.
3). By acrylamide-gel electrophoresis, free insulin was detected in the PAI preparation. PAI without any demonstrable free insulin by a successive washing procedure lost its biological activity as well as immunoreactivity, even though a considerable amount of insulin was still found in PAI preparation.
4). PAS-I was destroyed, to some extent, by digestive enzymes.β-NAS-I and PAI, on the other hand, were quite resistent to peptic and α-chymotryptic digestions in vitro.
From these results, the properties of insulin fixed physically on β-naphthyl-azo-polystyrene were found to be almost similar to those of chemically coupled by azo linkages. These findings also suggest that insulin fixed tightly (either chemically or physically) plays no significant role in its pharmacodynamic action. Insulin fixed loosely appears to be of importance for its activity.
