Thermal Stability of Human Blood Serum Orosomucoid (Acid α1-Glycoprotein) in Water and Water-Ethanol Systems

Abstract

Thermal stability of human serum orosomucoid (acid α1-glycoprotein) was studied in water and in water - ethanol systems by the differential scanning microcalorimetry and temperature perturbation difference spectrometry. This investigation has led to the following results: (i) the change in heat capacity Cp of isoionic orosomucoid with temperature was irreversible; different values of ∆H were obtained on repeated heating; (ii) in buffered solution at pH 7, hysteresis in temperature perturbation difference spectra was observed within the wavelength range of 250 - 266 nm; (iii) a strong destabilizing effect of ethanol on the orosomucoid molecule was observed in the alkaline region at an alcohol volume fraction of 20%. This effect corresponds to the anomalous behaviour of the water ethanol systems.