Figure 4.

Magnetic alignment and flipping of macro–nanodiscs by ¹⁴N NMR. Nitrogen-14 NMR spectra of DMPC:SMA-QA with (c,d) and without (a,b) YbCl₃ acquired at 295 K (a,c) and 310 K (b,d). The isotropic ¹⁴N NMR spectra (a,c) indicate that the macro–nanodiscs are isotropic in the gel phase, that is, below the gel-to-liquid crystalline phase transition temperature of DMPC lipids. The magnetic alignment (b) and its flipping because of the presence of 1 mM YbCl₃ (d) are revealed by the observed ¹⁴N quadrupole splitting of 9.4 (b) and 18.8 kHz (d) for the bilayer normal oriented perpendicular (b) and parallel (d) to the applied magnetic field direction, respectively. All of these NMR spectra were acquired using a Bruker 400 MHz NMR spectrometer.