Structure and growth of ultrasmall protein microcrystals by synchrotron radiation: I. microGISAXS and microdiffraction of P450scc.

Ultrasmall P450scc cytochrome microcrystals are grown by classical hanging vapor diffusion and by its modification using homologous protein thin-film template displaying a long-range order. The nucleation and growth mechanisms of P450scc microcrystals are studied at the thin cytochrome film surface by a new microbeam grazing incidence small angle X-ray scattering (microGISAXS) technique developed at the microfocus beamline of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. P450scc cytochrome crystals of about 5 microm are also investigated by synchrotron radiation diffraction in order to attempt a preliminary analysis of the atomic structure of this unique protein system yet unsolved.