We report a systematic study of the effects of types and positions of amino acid residues of tripeptides on the formation constants log beta, acid dissociation constants pK(a), N and the copper coordination modes of the copper(II) complexes with 27 tripeptides formed from the amino acids glutamic acid, glycine, and histidine. log beta values were calculated from pH titrations with 1 mmol L-1:I mmol L-1 solutions of the metal and ligand and previously reported ligand pK(a) values. Generalized multiplicative analysis of variance (GEMANOVA) was used to model the log beta values of the saturated, most protonated, monoprotonated, log beta(CuL) -log beta(HL), and pK(a) of the amide group. The resulting model of the saturated copper species has a two-term model describing an interaction between the central and the C-terminal residues plus a smaller, main effect of the N-terminal residue. The model supports the conclusion that two copper coordination modes exist depending on the absence or presence of His at the central position, giving species in which copper is coordinated via two or three fused chelate rings, respectively. The GEMANOVA model for pK(amide) which is the same as that for the saturated complex, showed that Gly-Gly-His has the lowest pK(amide) values among the 27 tripeptides. Visible spectroscopy indicated the formation of metal ligand dimers for tripeptides His-His-Gly and His-His-Glu, but not for His-His-His, and the formation of multiple ligand bis compexes CuL2 and Cu(HL)(2) for tripeptides (Glu/Gly)-His-(Glu/Gly) and His-(Glu/Gly)-(Glu/Gly), respectively.