PHOTON-CORRELATION SPECTROSCOPY APPLIED TO CHARACTERIZATION OF DENATURATION AND THERMAL-STABILITY OF HUMAN ALBUMIN

Photon correlation spectroscopy and light absorption measurements have been applied for characterisation of denaturation kinetics and therma l stability of human albumin in solution. The hydrodynamic size of the molecules has been studied as a function of pH, and the denaturation rate of ten different lots of 5% (w/v) human albumin solution has been measured at various temperatures. in the native (pH 7) state, the hyd rodynamic molecular diameter was found to 6.3 nm. The molecular size w as relatively stable between pH 10 and 5, but increased with decreasin g pH to approximately 20 nm at pH 3. The denaturation rate, measured a s change in hydrodynamic diameter per min, was strongly dependent on t emperature and increased 3-fold per degree in the 73-75 degrees C rang e. The investigated lots of albumin solution showed large variations i n stability at 74 degrees C, with denaturation rates ranging from 10 t o 100 nm min(-1). The observed thermal stability for the lots investig ated was ranked identically with both the employed techniques. In an e ffort to explain the observed lot to lot variations in denaturation ra te, a broad chemical characterisation including determination of free SH content, fatty acid content and composition and metal content, was performed. However, lot to lot variations in these parameters was not found to fully elucidate the observed variations in thermal stability. (C) 1997 Elsevier Science B.V.