[1] UJF, CNRS, UMR 5075,Inst Biol Struct Jean Pierre Ebel, CEA,Lab Resonance Magnet Nucl, F-38027 Grenoble 1, France
[2] CNRS, LISM, UPR 9027, Inst Biol Struct & Microbiol, F-13402 Marseille, France
[3] CNRS, BIP, UPR 9036, Inst Biol Struct & Microbiol, F-13402 Marseille 20, France