The CuA center of a soluble domain from Thermus cytochrome ba3. An NMR investigation of the paramagnetic protein

1H NMR measurements were conducted at 600 MHz on a soluble CuA domain from Thermus thermophilus cytochrome ba3. The NMR spectra showed several very noticeable narrow lines due to the very short relaxation time of the CuA site. Twelve sizable hyperfine-shifted signals were seen at pH 8 and 13 and pH 4.6. There were three very broad signals clustered between 250 and 300 ppm and a fourth broad signal at 105 ppm.