Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.|Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.|Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.|Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.|Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.|Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.