Powder Diffraction Analysis for Initiation Factor Subunits and P450scc Cytochrome


Shailesh Kumar Tripathi, Eugenia Pechkova, and Claudio Nicolini

Nanoworld Institute, University of Genoa, Corso Europa 30, 16132 Genoa, Italy

e-mail: shaileshh5@gmail.com

URL: http://www.fondazione-elba.org

 

Single crystal X-ray diffraction of initiation factor IF2 Alpha subunit and P450scc cytochrome were acquired at the ID13 of Synchrotron Radiation at ESRF (Grenoble). In the attempt to solve their structure we use here Crystal Powder diffraction technique. The routines such as EXPGUI used for this purpose are devoted to inorganic crystal refinement. So data editing was done (using FIT2D) to finally get the data in the form suitable to the routines. Finally rietveld refinement was done on the files to refine structure and obtain unit cell parameters. Different proteins having homology with our structure were used as template for doing parameter refinement. The plot of intensity versus 2*theta plot of IF2 alpha microcrystal and P450scc ultra microcrystal ( 5 microns in size) were quite similar to previously published data of hen egg white lysozyme , suggesting that they appears to be just amorphous non crystalline material. On IF2 Alpha only broad diffuse rings are instead seen without any low angle rings/spots, suggesting that we are dealing with large grain polycrystalline stuff rather than a fine powder, thereby possibly being dominated by just some crystallized salt despite the Mass Spectrometry data pointing to a real IF2 alpha subunit. In conclusion IF alpha appears to be low crystalline powder material and P450scc cytochrome ultra microcrystal appears largely amorphous non crystalline material, pointing to a hint of crystalline powder - rings at low angles- which could form nice powder with slightly different solvent conditions (work in progress). This preliminary conclusion is compatible with what being inferred by the close analogy to the powder diffraction pattern of hen egg lysozyme large crystal previously independently reported.[2]