Photon correlation spectroscopy applied to characterisation of denaturation and thermal stability of human albumin.

Photon correlation spectroscopy and light absorption measurements have been applied for characterisation of denaturation kinetics and thermal 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 hydrodynamic molecular diameter was found to 6.3 nm. The molecular size was relatively stable between pH 10 and 5, but increased with decreasing pH to approximately 20 nm at pH 3. The denaturation rate, measured as change in hydrodynamic diameter per min, was strongly dependent on temperature and increased 3-fold per degree in the 73-75 degrees C range. The investigated lots of albumin solution showed large variations in stability at 74 degrees C, with denaturation rates ranging from 10 to 100 nm min-1. The observed thermal stability for the lots investigated was ranked identically with both the employed techniques. In an effort to explain the observed lot to lot variations in denaturation rate, 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.