Table 1.

Curve fitting of data points displayed on Figure 3

Model	dfa	SSEb	Parameter estimates
A. Two-state dimer model	18	0.1287	KD1=10−7.6; KD2=10−4.9
B. Empirically used two-state dimer and two independent sites models	18	0.1287	c1=10−4.9; c2=10−12.4
C. Two independent sites model with f fixed to ½	18	0.1287	KD1=10−7.6; KD2=10−4.9
D. Two independent sites model*	17	0.0544	KD1=10−8.1; KD2=10−5.1; f=0.33
E. Two independent sites model with the empirical inclusion of Hill coefficients* #	15	0.0186	KD1=10−8.0; KD2=10−5.1; f=0.38; nH1=1.16; nH2=2.25

Parameter estimates of a set of models, and statistical comparisons of resulting fittings.

Comparisons between models by the extra-sum of squares F-test (Motulsky and Christopoulos, 2004): ^*P<0.05 with either of Models A, B or C; ^#P<0.05 with Model D.

^aDegrees of freedom.

^bSum of squares of the error.