Nuclear Magnetic Resonance Study of th Interaction between Copper Chlorophyll and Electron Acceptors

Abstract

The interactions of copper chlorophyll and copper chlorophyllin with various kinds of elect-ron acceptors have been investigated by means of measurements of longitudinal relaxation time (T₁) in ₁H-NMR spectra. The additions of copper chlorophyll to the solutions containing one of the electron acceptors shorten the T₁ values of the protons in the electron acceptors except β-carotene. These phenomena are considered to be due to the dipole-dipole interactions of the electron spins on Cu₂₊ and N atoms of four pyrrole units with the protons of the electron acceptors. The distances from the copper ion and the N atoms of pyrroles of copper chloro-phyll to the protons of each electron acceptor have been estimated by using the Solomon's equation. The structures of the complexes of copper chlorophyllin with the electron acceptors are proposed by means of computer simulation.