Table 3. Stability Constants (log β) and pK_a Values of the Zn(II)/Peptide Systems^a.

peptide	species	log βb	pKac	deprotonating residue
P1	[ZnH2L]−	26.97(2)
	[ZnHL]2–	21.06(2)	5.91	His
	[ZnL]3–	13.79(4)	7.27	Cys
	[ZnLH–1]4–	3.58(4)	10.21	Owater
P2	[ZnH2L]3+	26.65(4)
	[ZnHL]2+	20.91(2)	5.74	His
	[ZnL]+	13.16(6)	7.75	Cys
	[ZnLH–1]	3.51(6)	9.65	Owater
	[ZnLH–2]−	–7.16(6)	10.57	Owater/Lys

^aT = 298 K; I = 0.1 M NaClO₄; standard deviations are given in parentheses.

^bOverall stability constants (β) expressed by the equation β([ZnH_nL](ⁿ⁺²)⁺) = [[ZnH_nL]⁽ⁿ⁺²⁾⁺]/[Zn(II)][[L]ⁿ⁺][H⁺]ⁿ.

^cAcid dissociation constants (pK_a) expressed as pK_a = log β([ZnH_nL]⁽ⁿ⁺²⁾⁺) – log β([ZnH_n–1L]⁽ⁿ⁺¹⁾⁺).