Small Angle X ray Scattering applied to protein characterization studies

Author(s)

Mario de Oliveira Neto

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 2008-09-26

Examining board members

Igor Polikarpov; José Ramon Beltran Abrego; Guinther Kellermann; Luis Mauricio Trambaioli da Rocha e Lima; Ricardo De Marco

• Advisor: Igor Polikarpov

Abstract

Small angle X-ray scattering has been proven to be a powerful tool in the structural analysis of proteins in solution. This technique permits the three-dimensional visualization of native proteins envelop at the level of nanometers. In this study we discuss the small angle X-ray scattering theory and we proposed a new methodology to determine the molecular weight of proteins in solution, using only SAXS curve in arbitrary units. Prior the development of this method, the proteins molecular weighs were calculated by comparison with another of known size, usually bovine serum albumin. We also assembled SAXS equipment at the Physics Institute of São Carlos, which will permits in house measurements; as well as the cloning, expression and purification of DBD hTR, followed by the characterization of this protein by fluorescence anisotropy, crosslink and SAXS. The DNA-protein complex, F2-DBD hTR, was subjected to crystallization assays. Although, the crystals obtained for the complex showed no pattern of diffraction we were able to generate low-resolution models for the F2-DBD hTR using SAXS analysis. Moreover, the studies of the protein LepFNR and the complex IL-22/IL-22R1 by small angle X-ray scattering were performed in the line of SAXS of the LNLS, and their threedimensional models were resolved (AU)