Table 2

Thermodynamic parameters of metal binding to EhCaBP1in 20 mM MOPS buffer pH 7.4 at 25°C obtained and calculated from ITC results
Metal Site* Ka(M-1) ΔH(kcal.mol-1) ΔS(Cal.mol-1.K-1) ΔG(kcal.mol-1) Dominating forces (inferred)
Ca2+ 1 2.56E5 ± 9.1E4 −3.33 ± 0.30 13.6 −7.38 H-bonding/hydrophobic interactions
2 1.60E3 ± 9.0E2 −2.42 ± 0.28 6.54 −4.37 H-bonding/hydrophobic interactions
3 2.42E5 ± 8.3E4 8.80 ± 0.36 53.2 −7.34 Hydrophobic interactions
4 1.97E5 ± 8.6E4 −4.85 ± 0.94 7.94 −7.22 H-bonding/hydrophobic interactions
Sr2+ 1 5.57E4 ± 9.6E3 −6.74 ± 0.51 −0.90 −6.47 H-bonding /conformational change
2 6.44E4 ± 7.0E3 −10.35 ± 1.98 −12.7 −6.56 H-bonding /conformational change
3 1.06E5 ± 1.5E4 19.42 ± 2.71 88.1 −6.83 Hydrophobic interactions
4 1.49E5 ± 2.1E4 −7.44 ± 1.31 −1.28 −7.06 H-bonding /conformational change
Ba2+ 1 1.02E5 ± 1.5E4 −3.84 ± 0.17 10.0 −6.82 H-bonding/hydrophobic interactions
2 1.88E5 ± 2.0E4 −2.15 ± 0.39 16.9 −7.18 H-bonding/hydrophobic interactions
3 7.15E4 ± 6.1E3 3.23 ± 1.02 33.1 −6.62 Hydrophobic interactions
4 6.25E4 ± 9.3E3 −1.09 ± 2.14 18.3 −6.55 H-bonding/hydrophobic interactions
5 3.16E4 ± 1.9E3 −0.69 ± 0.23 18.3 −6.14 H-bonding/hydrophobic interactions

*Sites 1, 2, 3, 4 and 5 only correspond to the order of occupied sites during the non-linear fitting of ITC data by sequential mode. These are not exchange digits for the loop of EF-I, EF-II etc.

Kumar et al.

Kumar et al. BMC Biophysics 2012 5:15   doi:10.1186/2046-1682-5-15

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