Physicochemical Characterization of Heat-induced Soluble Aggregates of Bovine Globin

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Abstract
Physicochemical properties of heat-induced soluble aggregates of bovine globin were studied with several physicochemical measurements and electron microscopy. A great change in ellipticity and formation of soluble aggregates of globin occurred between 45 and 50°C. Soluble aggregates of globin formed below 60°C were globular particles with a diameter of 15 to 20 nm and a sedimentation coefficient and molecular weight of approx. 20 S and 8 × 105 , respectively. Their solutions were not so highly viscous. On the other hand, soluble aggregates of globin formed above 80°C were fibrous macro-aggregates with a thickness of 8 to 10 nm of which the sedimentation coefficient and molecular weight were above 50S and 106 to 108 , respectively. Their solutions were highly viscous. It is suggested that a great increase in globin viscosity on heating takes place through the following process; globular aggregates are formed spontaneously with the unfolding of globin molecules, and subsequently fibrous macro-aggregates are formed via extension and association of globular aggregates. It is also considered that fibrous macro-aggregates might form a gel at a higher concentration.