Institution: NIH Library Sign In as Member / Individual

This Article Abstract Full Text Services Alert me to new issues of the journal Request Copyright Permission

Supporting Information

Files in this Data Supplement:

Fig. 7. Fits to kinetic progress curves of T₊, T_–, and R gels. The time course of the transient absorption was analyzed as the sum of three stretched exponentials {exp[–(t/τ)^β]}. Two kinds of fits to the data were carried out, with parameters summarized in Table 1. In the first, each curve was fitted with a sum of three stretched exponentials with no constraints (black curve). In the second, the time constants and exponents for the three phases were constrained to be the same for all three data sets, and a zero amplitude was assumed for the fast bimolecular phase of T₊ and the slow bimolecular phase of R (green dashed curve). The reduced χ² value was 1.9 ´ 10^–4 for the constrained fit (R² = 0.9986) and 1.1 ´10^–4 for the fit, with all parameters free to vary (R² = 0.9992). The requirement for stretched exponentials suggests that there is incomplete averaging of conformational substates (1-3), explaining the lack of a perfect constrained fit (green dashed curve) and exact superposition of the linear combination of R and T₊ with T_– (Fig. 3a), as discussed in the main text. Blue curve, T₊ gel at pH 7.0; orange curve, R gel at pH 7.0; cyan curve, T_– gel at pH 7.6; red curve, T_– gel at pH 7.0; magenta curve, T_– gel at pH 7.0 plus 200 mM potassium chloride.

1. Austin, R. H., Beeson, K. W., Eisenstein, L., Frauenfelder, H. & Gunsalus, I. C. (1975) Biochemistry 14, 5355-5373.

2. Hagen, S. J. & Eaton, W. A. (1996) J. Chem. Phys. 104, 3395-3398.

3. Hagen, S. J., Hofrichter, J. & Eaton, W. A. (1995) Science 269, 959-962.