Skip to main content
. Author manuscript; available in PMC: 2010 Jul 8.
Published in final edited form as: Biochemistry. 1990 Apr 24;29(16):3937–3943. doi: 10.1021/bi00468a021

Table I.

Summary of Metal Dissociation Constants

metal ion effective ionic radius (Å) KD (M)a ±SE (M) calcd ΔGB (kcal/mol)b
group IA
 Li(I) 0.84c ≥0.9 ≥−0.1
 Na(I) 1.12 ≥2.4 ≥0.5
 K(I) 1.46 ≥0.8 ≥−0.1
 Rb(I) 1.56 ≥1.9 ≥0.3
group IIA
 Mg(II) 0.81c 0.20 0.06 −1.0
 Ca(II) 1.06 2.5 × 10−5 1.1 × 10−5 −6.3
 Sr(II) 1.21 5.4 × 10−3 0.2 × 10−3 −3.1
 Ba(II) 1.38 ≥0.6 ≥−0.3
group IIIA
 Sc(III) 0.81c 1.91 × 10−4 0.01 × 10−4 −5.1
 Y(III) 0.96 3.8 × 10−5 0.1 × 10−5 −6.0
 La(III) 1.10 7.29 × 10−4 0.04 × 10−4 −4.3
lanthanides
 Ce(III) 1.07 4.6 × 10−4 0.6 × 10−4 −4.6
 Pr(III) 1.06 3 × 10−4 1 × 10−4 −4.8
 Nd(III) 1.05c 2.3 × 10−4 0.4 × 10−4 −5.0
 Sm(III) 1.02 1.3 × 10−4 0.2 × 10−4 −5.3
 Eu(III) 1.01 9.5 × 10−5 0.5 × 10−5 −5.5
 Gd(III) 1.00 8.2 × 10−5 0.1 × 10−5 −5.6
 Tb(III) 0.98 9 × 10−6d 4 × 10−6 −6.9
 Dy(III) 0.97 2.5 × 10−5 0.8 × 10−5 −6.3
 Ho(III) 0.96c 3.3 × −610−5 0.1 × 10−5 −6.1
 Er(III) 0.945 2.6 × 10−5 0.1 × 10−5 −6.3
 Tm(III) 0.94c 1.3 × 10−5 0.2 × 10−5 −6.6
 Yb(III) 0.925 0.8 × 10−6 0.2 × 10−6 −8.3
 Lu(III) 0.92c 1.1 × 10−6 0.2 × 10−6 −8.1
a

All measurements were at 25 °C and 2.5 μM protein, 100 mM KCl, and 10 mM PIPES, pH 6.0.

b

Binding free energies for 1 M standard state concentration (ΔGB = RT In KD)

c

Effective ionic radius for coordination number = 7 was obtained by averaging EIR for CN = 6 and CN = 8. In other cases EIR are those measured for CN = 7. EIR are from Shannon (1976).

d

Determined by equilibrium dialysis.