Unexpectedly Strong Diamagnetism of Self-Assembled Aromatic Peptides

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 aromatic peptides is greatly enhanced for about 11 times by self-assembling, reaching two orders of magnitude higher than the mass susceptibility of pure water. The self-assembly of aromatic rings in the peptide molecules plays the key role in such a strong diamagnetism.

A biomolecular magnetic switch by diamagnetic cations

“…In contrast, the AYFFF assemblies in water have a negative average susceptibility of -4.7×10 -5 emu/(g•Oe) (Fig. 1c), consistent with the strong diamagnetism of the peptide assemblies observed in our previous work 25 . Moreover, non-aromatic peptide IIIGK (i.e., Isoleucine-Isoleucine-Isoleucine-Glycine-Lysine) assemblies do not show the diamagnetism-toparamagnetism switching phenomenon (Fig.…”

“…The relatively large fluctuation of χ is likely due to the morphological variations of the AYFFF assemblies. Since paramagnetic and diamagnetic objects are subjected to magnetic forces of opposite directions in a given gradient magnetic field, we also measured χ by weighing the magnetic forces of peptides at different states under a fixed magnetic field using a high-precision electronic balance 25 and got similar results to the SQUID measurements (Supplementary Fig. 2).…”