Table 1.

Parameters used in simultaneous sum-of-squares best fit of isotherms for a series of separately prepared 5,5′ dimethylBAPTA and EDTA solutions in TRIS buffer with residual calcium present

Sample	Residuala Ca2+ (μM)	Purityb (%)	K′Ca2+ (nM)	ΔH (cal/mol)
5,5′ dimethylBAPTA
0c	0	59.10 (59.05–59.20)d	105e	2155.7 (2148.0–2163.5)
1	563	68.75 (68.67–68.84)
3	663
6	847
EDTA
8	42	97.39 (97.35–97.42)	62.3 (59.0–65.1)	−12,814.3 (−12,785–12,843)
9	975
12	1105

^aAdded Ca²⁺ derived from analytical preparation, with small adjustments made for goodness-of-fit.

^bAn additional 3.5% (95% CI, 3.23–3.79) of the 5,5′ dimethylBAPTA macromolecule described in the simulation is dedicated to a second single-binding site chelator with weak Ca²⁺ affinity (13.1 μM, (95% CI, 9.95–17.85)) and enthalpy of 479 cal/mol to represent an apparent impurity (see the Supporting Material).

^cSample prepared independently without analytical glassware.

^dCa²⁺ apparent dissociation constant derived from potentiometric data analysis.

^eParentheses indicate 95% confidence intervals for floating parameters, computed from sum-of-squares best fit values; they do not reflect propagated experimental errors.