Unexpectedly strong diamagnetism and superparamagnetism of aromatic peptides due to self-assembling and cations

TL;DR

This study reveals that aromatic peptides can exhibit unexpectedly strong diamagnetism and superparamagnetism due to self-assembly and cation interactions, bridging the gap between experimental observations and theoretical predictions in biomagnetism.

Contribution

It demonstrates that aromatic peptide self-assembly and cation mixing significantly enhance biomagnetic properties, a novel insight into organic biomagnetism.

Findings

Self-assembly increases peptide diamagnetism by about 11 times.

High concentration ZnCl2 induces superparamagnetism in peptide assemblies.

Aromatic rings and cations are key to the observed magnetic enhancements.

Abstract

There is a considerable amount of work that shows the biomagnetism of organic components without ferromagnetic components at the molecular level, but it is of great challenge to cover the giant gap of biomagnetism between their experimental and theoretical results. Here, we show that the diamagnetism of an aromatic peptide, the AYFFF, is greatly enhanced for about 11 times by self-assembling, reaching two orders of magnitude higher than the mass susceptibility of pure water. Moreover, the AYFFF self-assemblies further mixed with ZnCl2 solution of sufficiently high concentrations display superparamagnetism, with the mass susceptibility reaching more than two orders of magnitude higher than the absolute value of pure water, which may approach the mass susceptibility of ferromagnetism. The aromatic rings in the peptide molecules and the cations are the keys to such a strong diamagnetism and superparamagnetism of aromatic peptides.