Cu(II) and Ni(II) Interactions with the Terminally Blocked Hexapeptide Ac-Leu-Ala-His-Tyr-Asn-Lys-amide Model of Histone H2B (80–85)

Table 3

Stability constants of Cu(II) and Ni(II) complexes of -LAHYNK- at 25^°C.

Stability constants of Cu(II) complexes (log𝛽)^(a)
p𝐾(𝑛/𝑛−1)^(b)	CuH2L	CuL	CuH-1L	CuH−2L	CuH−3L	CuH−4L
	23.55 (2)	12.06 (2)	3.02 (3)	−6.89 (2)	−17.42 (3)	−29.07 (4)
	2/0	0/−1	−1/−2	−2/−3	−3/−4
	5.75^(c)	9.04	9.91	10.53	11.65
Stability constants of Ni(II) complexes (log𝛽)^(a)
p𝐾(𝑛/𝑛−1)^(b)	NiH2L	NiHL	NiH−1L	NiH−2L	NiH-3L
	23.26 (2)	14.65 (4)	−2.60 (2)	−12.35 (2)	−23.09 (3)
	2/1	1/−1	−1/−2	−2/−3
	8.61	8.63^(c)	9.75	10.74

^(a)𝛽 = [M_iH_jL_k]/([M]ⁱ[H]^j[L]^k) where M = Cu(II) or Ni(II), standard deviations of the last digit are given in parenthesis. ^(b)For the ionization reaction MH_𝑛L↔MH_𝑛−1L+H⁺, ^(c)meanp𝐾 value for two protons release.