Z gradient cryogenic probe

NMR spectra were collected at the National Magnetic Resonance Facility at Madison on a 750 MHz (¹H) Bruker with a z-gradient cryogenic probe. The buffer used for NMR samples (HNT buffer) contained 20 mM HEPES at pH 7.6, 150 mM NaCl, and 2 mM TCEP. All sample temperatures were regulated at 25 °C. NMRPipe software was used to process the raw NMR data and NMRFAM-SPARKY software was utilized to visualize and analyze the processed NMR data.
To study the interactions of FDX1 with elesclomol, 0.2 mM [U-¹⁵N]-FDX1 in HNT buffer were placed in 5 mm Shigemi NMR tubes, and 2D ¹H,¹⁵N TROSY-HSQC spectra were collected before and after titration of 5 equivalent molar ratio of elesclomol dissolved in HNT buffer.
Chemical shift perturbations (Δδ_HN absolute value ppm) were calculated by
$$\text{Eq}.\mathrm{i}:\Delta {\delta }_{\text{HN}}=[(\Delta {\delta }_{\mathrm{H}}{)}^2+(\Delta {\delta }_{\mathrm{N}}∕6{)}^2{]}^{1∕2}$$
where Δδ_H and Δδ_N are the chemical shift changes in the ¹H and ¹⁵N dimensions, respectively.