Rockefeller University Press

Table I

Parameters used for the calculations

1	2	3	4	5	6
Calcium	D_buf	k_1,buf	k_−1,buf	K_d,buf	[buf]_R
buffer
	10⁻⁶cm²s⁻¹	10⁸M⁻¹s⁻¹	s⁻¹	μM	mM
EGTA	1.7^§	0.025^§	1.485^§	0.594	18.24
ATP	1.4^‖	0.136^‖	30,000^‖	2,200	5.5
troponin	0	0.575^*	115^*	2	0.42^§
fura-2	0.54^‡	0.7^‡	30^§	0.43	0.05-6

1	2	3	4	5	6
Calcium	D_buf	k_1,buf	k_−1,buf	K_d,buf	[buf]_R
buffer
	10⁻⁶cm²s⁻¹	10⁸M⁻¹s⁻¹	s⁻¹	μM	mM
EGTA	1.7^§	0.025^§	1.485^§	0.594	18.24
ATP	1.4^‖	0.136^‖	30,000^‖	2,200	5.5
troponin	0	0.575^*	115^*	2	0.42^§
fura-2	0.54^‡	0.7^‡	30^§	0.43	0.05-6

Column 1 gives the name of the Ca buffer. Column 2 gives the value of the diffusion coefficient in myoplasm. Columns 3 and 4 give the values of the apparent forward and backward rate constants for Ca complexation. Column 5 gives the values of the apparent dissociation constant, equal to the ratio of the values in columns 4 and 3. Column 6 gives the resting concentrations that were used for the calculations. The values in columns 4 and 5 for EGTA are estimated for pH = 6.9. The value in column 6 for troponin gives the concentration of Ca-regulatory sites on troponin (expressed in terms of myoplasmic concentration in the I-band) for a sarcomere length of 3.6 μm, with the assumption that all the troponin lies on the thin filaments, which have a length of 2.05 μm (Page and Huxley, 1963); the value of 0.42 mM for the concentration in the I-band corresponds to a spatially averaged myoplasmic concentration of (2.05/3.6)0.42 = 0.24 mM, as estimated by Baylor et al. (1983). Values of other parameters are D_Ca = 3 × 10⁻⁶ cm² s⁻¹ (Pape et al., 1995), and, unless noted otherwise, ø_point = 0.5 × 10⁶ ions s⁻¹ (which corresponds to 0.16 pA). In the equations in Appendix C, α_ATP = K_d,ATP⁻¹).

Baylor et al. (1983),

‡

Pape et al. (1993),

Pape et al. (1995),

‖

Baylor and Hollingworth (1998).

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