Unexpectedly super strong paramagnetism of aromatic peptides due to cations of divalent metals

The magnetism of most biomolecules has not been characterized, which impedes our understanding of some magnetic field-related phenomena, including magnetoreception and magnetic effects on biological systems. Here we measured the magnetic susceptibility of an aromatic peptide in the presence or absence of divalent metal cations in liquid phase at room temperature, which is very close to the physiological conditions in many living organisms. Unexpectedly, the AYFFF self-assemblies in the chloride solution of various divalent cations (Mg2+, Zn2+, and Cu2+) display super strong paramagnetism, indicating the possible existence of ferromagnetism in living organism. We attribute the observation to the rich aromatic rings in the AYFFF assemblies, on which the cations adsorb via cation-{\pi} interactions, display non-divalent behavior and thus possess magnetic moments. The findings not only provide fundamental information for understanding the magnetism of biomolecules, provoke insights for investigating the origin of magnetoreception and bio-effects of magnetic field, but also help developing future magnetic control techniques on aromatic ring-enriched biomolecules and drugs, including their aggregation, dynamics and reactions, in living organisms.