Table 2.

SANS data for CPR at different salt concentrations; Derived hydrodynamic parameters and analysis in terms of two-state models.

Added NaCl, M	Hydrodynamic parameters		Two-state Modelsa
	Rg, Å	Dmax b, Å	Crystal structure + Huang et al. model			Crystal structure + ΔTGEE mutant model
			f compact c	f extended d	χ2	f compact c	f extended d	χ2
0	24.7 ± 0.1	71	0.90	0.10	1.64	0.90	0.10	1.75
0.1	25.8 ± 0.1	80	0.86	0.14	2.27	0.84	0.16	2.37
0.2	25.9 ± 0.2	81	0.85	0.15	2.24	0.85	0.15	2.38
0.5	26.6 ± 0.1	91	0.72	0.28	2.12	0.72	0.28	2.52
0.6	27.4 ± 0.2	96
1.0	30.3 ± 0.3	119
1.5	31.6 ± 0.4	121

^aThe models used to analyse the scattering data in terms of a two-state equilibrium are described in the text. In both cases the compact state is described by the crystal structure of oxidised CPR; the extended structure is described either by the model of Huang et al.³⁷ or by the structure of the ΔTGEE mutant⁴². The goodness-of-fit to the scattering curve is given by the χ² statistic. The two-state models were not used to analyse the data for >0.5 M added salt; see text.

^bAll D_max values, determined from P(r) fits using GNOM in Primus, as part of the ATSAS suite, were rated as “good” (0.8) fits or better. All errors < 2 Å.

^bFraction of the compact conformation.

^cFraction of the extended conformation.