A new approach to the measurement of protein solubility by Michaelson interferometry

Protein concentration influences nucleation and crystal growth rates, there fore an appropriate degree of supersaturation is essential for the preparat ion of large and good quality crystals. Knowledge of a protein's solubility dependence on solution variables such as temperature, pH, or ionic strengt h can be very useful for defining optimum conditions for protein crystal gr owth work. We have refined a Michaelson interferometry technique reported b y Sazaki et al. (J. Crystal Growth 169 (1996) 355.) for determination of pr otein solubility using the proteins lysozyme and equine serum albumin by ex amining the behavior of both surface and concentration gradient fringes. Th is has provided a sensitive and accurate estimate of protein solubility usi ng small crystals (0.2 mm x 0.1 mm). (C) 2001 Elsevier Science B.V. All rig hts reserved.