Figure 2.

Ways of two hydrated Cu²⁺ ions binding with two phospholipids. The cyan, brown, red, white and yellow balls represent carbon, phosphorus, oxygen, hydrogen and copper, respectively. (a) A phosphate group in a phospholipid (PL). (b–d) Hydrated Cu²⁺ ions binding to phospholipids based on a simplified model, H₃C-[PO₄]⁻-CH₃. (b) Initial state. Four molecular groups (H₃C-[PO₄]⁻-CH₃ and [Cu(H₂O)₅]²⁺) are separated by a large distance. (c) State I. Two Cu²⁺ ions bind to two phospholipids, respectively, resulting in two [PL-Cu(aq)]⁺ structures. (d) State I′. One Cu²⁺ ion binds to two phospholipids, forming a structure [PL-Cu(aq)-PL]. (e) State II. Two Cu²⁺ ions bind simultaneously with two phospholipids, forming a [PL-diCu(aq)-PL]²⁺ structure.