Fig. 1. Barotropic behavior of lipid nanodiscs.

Illustration of the reproducibility of DLS, SEC, and NMR data (a: DPPC; b: POPC/POPG; c: DMPC) of empty, i.e., without MP, nanodiscs collected at atmospheric pressure before and after a pressure jump to 2500 bar during 25 min (DLS and SEC experiments) or ramp (NMR experiments) (see Methods). For DLS and SEC experiments, the graphs represent the volume-weighted distribution function of the diameter of nanodiscs in nm and the absorbance at 280 nm in the function of the volume of elution (the y axis has been removed for clarity), respectively. One-dimensional (1D) ¹H NMR spectra represent a close-up in the region of amide, amine, and aromatic protons of the lipoprotein MSP1D1 and 2D ¹H,¹³C spectra are plotted in the CH₂ and CH₃ resonance region of the lipid acyl chains. The numbers on the 2D NMR spectra indicate the CH_n (n = 2 or 3) moieties composing the lipid acyl chains indicated on the chemical structures on the right (NMR assignments are based on abundant literature, e.g., ref. ⁶⁶) and the letter C in green indicates some signals of the cholesterol in the case of POPC/POPG and DPPC nanodiscs. The asterisk symbols in 1D and 2D experiments indicate residual traces of imidazole and weak signals that could correspond to CH₂ moieties spatially close to the lipoprotein, respectively.