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. Author manuscript; available in PMC: 2011 May 25.
Published in final edited form as: Biochemistry. 2010 May 25;49(20):4361–4373. doi: 10.1021/bi100092a

Table 2.

Values of kd as a function of Na+ and anion (Cl−, Glu− or F−) for the dissociation of RPo at the λPR promoter at 25 °C

Na+
(M)		 kd (s−1)
Cl− Glu− F−
0.23 (2.8±0.1) × 10−4
0.25 (5.8±0.4) × 10−4
0.27 (1.2±0.3) × 10−3
0.29 (2.37±0.09) × 10−3
0.34 (8±4) × 10−6
0.37 (1.2±0.3) × 10−5
0.43 (1.7±0.7) × 10−6
0.45 (1.4±0.5) × 10−5
0.46 (1.2±0.5) × 10−5
0.50 (2.1±0.2) × 10−5
0.55 (1.8±0.5) × 10−5
0.57 (1.8±0.4) × 10−5
0.61 (6.5±0.8) × 10−5
Skd 9.2±0.1 3.2±0.8

Values of kd in Cl− buffer determined by direct measure of the irreversible rate of dissociation of RPo initiated by the addition of heparin. Values of kd in Glu− and F− buffer determined using a decay to equilibrim experiment (eqs 5-6, see Methods) at 25 °C. Skd ≡ (∂logkd /∂log[Na+]). Values of kd in Glu− do not differ from those in F− outside of experimental uncertainty and were fit together to determine Skd.