GEL TECHNIQUES AND SMALL-ANGLE X-RAY-SCATTERING TO FOLLOW PROTEIN CRYSTAL-GROWTH

Agarose gels have been used in combination with small angle X-ray scat tering (SAXS) at the synchrotron radiation facility LURE (Orsay) to fo llow hen egg white (HEW) lysozyme nucleation and growth. The advantage of using gels rather than solutions is that the nucleation centers, b eing trapped in the gel network, remain in the X-ray beam during the e xposure. The advantage of agarose is that the scattering of the gel al one is limited to the low angle part. Nucleation of lysozyme was induc ed by decreasing temperature leading to supersaturation in the gel. Th e effect of varying different parameters was investigated: the percent age of gel and the concentration of salt, the effect of irradiation on crystal growth and the protective effect of an anti-oxidative agent. The crystals formed within one day were good enough to give Bragg refl ections at small angles, easily observable with the camera at LURE.