Table 2. Binding constants for interactions between streptavidin and SBP-Tags.

The BIAevaluation software was used to evaluate the fit of the association model (A + B = AB) and dissociation model (AB = A + B) to the experimental data. The goodness of fit to these models was assessed by inspecting the residual plot (which shows the difference between experimental and calculated data), the lag plot and the ² value. The residual (0.6RU randomly scattered around the x axis) and ² values are well within the noise limit. The points in the lag plot are randomly scattered around the origin. These tests indicate that the model provides a good representation of the data.

	k on (M 1s1)	k off (s1)	K d (M)
SBP-Tag	3.17 105 7.98 103	4.85 104 3.61 106	1.53 109 4.52 1010
SBP-Tag2	3.38 105 8.51 103	4.96 104 3.52 106	1.47 109 4.14 1010