Superparamagnetism of tryptophan and walk memory of proteins

TL;DR

This paper reports superparamagnetism in tryptophan and proposes a model where proteins behave as a multidimensional Ising lattice, exhibiting ferromagnetic memory and long-range spatial coherence under physiological conditions.

Contribution

It introduces the concept of protein assembly as a physical lattice gas with Ising-like behavior, revealing magnetic properties and memory effects in proteins.

Findings

Fibrinogen shows attenuated magnetic response due to its one-dimensional structure.

Proteins can exhibit ferromagnetic memory through spatial coherence of spin states.

Superparamagnetism in tryptophan suggests a microscopic origin for magnetic phenomena in proteins.

Abstract

Superparamagnetism of tryptophan implying the presence of magnetic domain is reported. The observation helps us to conceive assembly of proteins as a physical lattice gas with multidimensional Ising character, each lattice points assuming discrete spin states. When magnetic field is applied the equilibrium is lost and the population density of one spin state increases (unidirectional alignment), resulting in net magnetization. Spatial coherence between the identical spin states further imparts a ferromagnetic memory. This effect is observed using direct nanoscale video imaging. Out of the three proteins ferritin serum albumin and fibrinogen, fibrinogen showed an attenuated response, the protein being essentially one dimensional. Eventually, Ising lattice is capable of showing ferromagnetic memory only when it has a higher dimensional character. The study highlights possible presence of long range spatial coherence at physiological condition and a plausible microscopic origin of the same.