· Backbone chemical shift assignments were carried out on a mM [13 C/ 15 N/ 2 H]HR1 sample in a buffer containing 20 mM sodium phosphate (pH 6), 30 mM sodium chloride, 150 mM DMPC/DHPC, and 3% D 2 O. 1 H N, 15 N, 13 C α, and 13 C′ chemical shifts were obtained from TROSYbased HNCO and HNCA spectra recorded at 35°C on a 700MHz .