Determination of the adiabatic compressibility of bovine serum albumen in concentrated solution by a new ultrasonic method

New data are presented for the adiabatic compressibility of bovine serum al bumen (BSA) over the temperature range 2-85 degrees C and at pH 5, 6, 7 and 8. The relative impact of intrinsic and hydration contributions to the obs erved compressibility for BSA is estimated and shown to agree very well wit h general values for globular protein and with previous results for HSA. Th e compressibility manifests a maximum value in the regions where BSA is mos t stable, exhibiting a parabolic dependence on temperature with lowest valu es where it is least stable. These data are obtained with a novel technique that employs a commercial, low cost and automated pulse echo apparatus for the measurement of the speed of sound to an accuracy of 1 m s(-1) and a pr ecision of 0.1 m s(-1). This requires the use of relatively high protein co ncentrations, typically of the order of 10 mg ml(-1) upwards. The ultrasoun d data is analysed using a relation obtained from scattering theory that ac counts for the multiple scattering of sound in concentrated systems. The te chnique has a data acquisition rate of 20 measurements per second and large quantities of high-quality data can be amassed, permitting the automatic s canning of the compressibility of a protein as a function of temperature fo r example. This makes it particularly appropriate for studying the behaviou r of proteins and other large biomolecules in food. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.