Comparison of supersaturation profiles employed on lysozyme crystallization from a hanging drop

Fiber optic Raman spectroscopy combined with a partial least-squares regression model was used as a monitor of lysozyme concentration during crystallization in a hanging-drop experiment in real time. Raman spectral features of the buffer and protein were employed to build the regression model. The use of fiber optic technology coupled with Raman spectroscopy, which is ideal for use with aqueous solutions, results in a powerful, noninvasive probe of the changing environment within the solution. Monitoring the concentration changes of the lysozyme within the hanging drop permits a measurement of the level of supersaturation of the system and provides for the potential of dynamic control of the crystallization process. Previously, hanging-drop experiments have been monitored in real time. These experiments have given insight into the changing environment of the hanging drop as the lysozyme within the hanging drop concentrates and nucleates and as crystal growth continues. Upon alteration of the ionic strength of the reservoir, the number, size, and quality of the resultant crystals has been affected. This investigation compares the resultant supersaturation of the lysozyme crystallization within the hanging drop by employing various reservoir conditions. These conditions include a constant ionic strength reservoir, a step change in reservoir ionic strength, and a differential change in reservoir ionic strength.