Replication protein A (RPA), the eukaryotic ssDNA binding protein, is a heterotrimeric protein required for almost all aspects of cellular DNA metabolism. RPA binds single-stranded DNA with high affinity. We want to elucidate the roles of RPA in DNA replication, using integrated structural and biophysical methods, using the Archaeon Pyrococcus abyssi as a model organism. RPA is an ideal target for small angle scattering studies as there is partial structural information available on the individual protein subunits, an incomplete structure available of the trimerization core, and of partial structures of portions of RPA bound to DNA. In our initial experiments we have obtained data on the unliganded protein and its components. We now wish to expand this to investigate the structure of the proteins bound to DNA constructs representing normal and damaged intermediates in DNA replication.