Figure 7.

(a) ³¹P NMR spectra of the phosphate signal of a 0.5 mM solution (0.426 mg/mL) of purified 1 in 0.2 M KPi (pH = 7) with added Co(II) at the indicated concentrations. (b) The measured full-width at half-maximum (fwhm) of the phosphate ³¹P NMR signal is linearly dependent on the concentration of added Co(II). The equation of the linear calibration curve is fwhm = {(936 ± 8) × [Co(II)]} + (7.2 ± 0.4). (c–e) ³¹P NMR spectra of the phosphate signal for three separate batches of 0.426 mg/mL of crude 1 in 0.2 M KPi at pH = 7. Using the calibration curve of (b), the amount of line broadening corresponds to a Co(II) concentration of 0.086 ± 0.004 mM, 0.091 ± 0.008 mM, and 0.065 ± 0.006 mM for samples (c), (d) and (e), respectively.