Table 1.

Intramolecular distances for 17 membrane-bound doubly-labeled derivatives from four-pulse DEER experiments

Derivative	Distance, Å
	DEER	Ideal helix	SDS (NMR)
11R1/26R1	25	22.5	22.5
11R1/41R1	48	45	43.3
22R1/52R1	49	45	23.3
26R1/41R1	23	22.5	25.4
26R1/56R1	44	45	24.4
37R1/67R1	42	45	39.2
41R1/56R1	23	22.5	24.0
41R1/67R1	37	39	38.8
41R1/70R1	41	43.5	42.0
44R1/67R1	36	34.5	34.2
48R1/67R1	29	28.5	27.8
56R1/70R1	22	21	20.1
56R1/85R1	42	43.5	42.0
63R1/81R1	26	27	25.7
11R1/70R1	>60	88.5	22.7
11R1/81R1	>60	105	22.8
41R1/85R1	>60	66	62.6

The experimental distances are taken from the peaks of the Tikhonov regularization-based fits (for data, see Fig. S3), but identical maximal distances (within 1 Å or less) were obtained from Gaussian fits. The data are compared to the rise of an ideal helical structure, which is taken to be 1.5 Å per residue. The final column shows the respective α -carbon distances from the high-resolution NMR structure of SDS-bound α -synuclein.