Probing DNA-amyloid interaction and gel formation by active magnetic wire microrheology

TL;DR

This study uses magnetic microrheology to investigate how bacterial proteins form amyloid fibers that interact with DNA, leading to gel-like structures, and demonstrates the technique's effectiveness in analyzing complex biological fluids.

Contribution

It introduces magnetic rotational spectroscopy as a simple, effective method to probe DNA-amyloid interactions and gel formation, supported by theoretical modeling and application to biological samples.

Findings

DNA and Hfq-CTR form gel-like networks with amyloid fibers

Pristine DNA and Hfq-CTR behave as viscous liquids

Magnetic microrheology effectively characterizes complex biological fluids

Abstract

Recent studies have shown that bacterial nucleoid-associated proteins (NAPs) can bind to DNA and result in altered structural organization and bridging interactions. Under spontaneous self-assembly, NAPs may form anisotropic amyloid fibers, whose effects are still more significant on DNA dynamics. To test this hypothesis, microrheology experiments on dispersions of DNA associated with the amyloid terminal domain (CTR) of the bacterial protein Hfq were performed using the technique of magnetic rotational spectroscopy (MRS). In this chapter, we survey this microrheology technique which is based on the remote actuation of magnetic wires embedded in a sample. MRS is interesting as it is easy to implement, and does not require complex procedures regarding data treatment. Pertaining to the interaction between DNA and amyloid fibers, it is found that DNA and Hfq-CTR protein dispersion behave like a gel, an outcome that suggests the formation of a network of amyloid fibers cross-linked with the DNA strands. In contrast, the pristine DNA and Hfq-CTR dispersions behave as purely viscous liquids. To broaden the scope of the MRS technique, we include theoretical predictions for the rotation of magnetic wires regarding the generic behaviors of basic rheological models from continuum mechanics, and we list the complex fluids studied by this technique over the past 10 years.