Fig 1.
Room temperature, solution EPR spectra of αS56 and αS69 (a) in buffer, (b) with IMM, (c) with NPM.
Black line: experiment, red line: simulation. Arrows show the low field feature indicating reduced mobility (see text).
Table 1.
Parameters (τr) describing the mobility of the spin label of αS bound to natural membranes from simulations of cw-EPR spectra.
τr: rotation-correlation time.
Fig 2.
DEER time traces and distance distributions for αS27/56 bound to IMM, NPM and POPG SUVs.
(a) Time trace before background correction (black line), red line: background. (b) Time trace after background correction (black line), red line: fit of the time trace with the distance distributions shown in c. (c) Distance distribution obtained after Tikhonov regularization of αS27/56 bound to IMM (black line) and NPM (red line). (d) Distance distribution obtained after Tikhonov regularization of αS27/56 bound to POPG SUVs. For comparison, the same regularization parameter was used for c and d, it seems to be on the small side for d. Small peaks shown with asterisks in Fig 2C have negligible contribution to the distance distribution according to the suppression tool in DEER analysis, the feature at 5.5. nm in all distributions is related to a background artefact and not relevant. Considering the two contributions in the distance distributions, the larger intensity contribution is centered at a longer distance and the smaller intensity contribution is centered at a shorter distance. The distance distributions were fitted with two Gaussians, the parameters of which are given in Table 2.
Table 2.
Parameters of distance distributions for αS27/56 bound to SUVs of IMM and NPM and model membranes for comparison.