. Author manuscript; available in PMC: 2012 Apr 16.

Published in final edited form as: J Am Chem Soc. 2007 Nov 7;129(47):14597–14604. doi: 10.1021/ja0731569

Table 1.

The binding affinities of ligands toward apo FDAS by isothermal titration calorimetry

ligands	Stoichiometr y (N)	K_a (app) (×10⁵ M⁻¹)	ΔH (kcal/mol)	S (cal/mol)
SAM	0.56 ± 0.01	8.0 ± 0.5	−25 ± 0.4	−58
SAH	0.72 ± 0.01	302 ± 74	−40 ± 0.5	−98
FDA	1.16 ± 0.01	45.5 ± 6.5	−14 ± 0.1	−17
Ade	0.67 ± 0.01	12.2 ± 1.2	−20 ± 0.4	−40
3′-deoxy-Ade	0.37 ± 0.02	4.5 ± 0.6	−16 ± 0.9	−27
L-Met^FDA^*	0.58 ± 0.07	0.59 ± 0.05	−17 ± 2	−36
L-Met^Ade^*	0.48 ± 0.11	0.57 ± 0.07	−13 ± 3	−22

The binding affinity of L-Met^FDA was obtained by titrating 1mM L-methionine into 0.08 mM FDA and 0.02 mM apo FDAS mixture, while the affinity of L-Met^Ade was obtained by titrating 1mM L-methionine into 0.024 mM Adenosine and 0.02 mM apo FDAS mixture