. 2023 Nov 1;62(45):18607–18624. doi: 10.1021/acs.inorgchem.3c02910

Table 1. Protonation Constants (log β) and pK_a Values of Peptides P1 and P2^a.

peptide	species	log β^b	pK_a^c	deprotonating residue
P1	[H₆L]⁺	41.40(4)	3.37	C_terminal
	[H₅L]	38.03(4)	4.19	Asp
	[H₄L]⁻	33.84(3)	6.96	His
	[H₃L]^2–	26.88(3)	8.15	Cys
	[H₂L]^3–	18.73(2)	8.92	Cys
	[HL]^4–	9.81(2)	9.81	Cys
P2	[H₈L]⁷⁺	47.41(2)	2.15	C_terminal
	[H₇L]⁶⁺	45.26(2)	3.12	Asp
	[H₆L]⁵⁺	42.14(2)	3.74	Asp
	[H₅L]⁴⁺	38.40(2)	4.38	Glu
	[H₄L]³⁺	34.02(2)	6.73	His
	[H₃L]²⁺	27.29(1)	8.15	Cys
	[H₂L]⁺	19.14(1)	9.03	Cys
	[HL]	10.11(1)	10.11	Cys

T = 298 K; I = 0.1 M NaClO₄; standard deviations on the last digit given in parentheses.

Overall stability constants (β) expressed by the equation β(H_nL) = [H_nL]/[L][H⁺]ⁿ.

Acid dissociation constants (pK_a) expressed as pK_a = log β(H_nL) – log β(H_n–1L).

Table 1. Protonation Constants (log β) and pKa Values of Peptides P1 and P2a.