In-depth magnetometry and EPR analysis of the spin structure of human-liver ferritin: from DC to 9 GHz.

Ferritin, the major iron storage protein in organisms, stores iron in the form of iron oxyhydroxide most likely involving phosphorous as a constituent, the mineral form of which is not well understood. Therefore, the question of how the 2000 iron atoms in the ferritin core are magnetically coupled is still largely open. The ferritin core, with a diameter of 5-8 nm, is encapsulated in a protein shell that also catalyzes the uptake of iron and protects the core from outside interactions.

Tracking amyloid oligomerization with monomer resolution using a 13-amino acid peptide with a backbone-fixed spin label.

Amyloid oligomers are suspected as toxic agents in neurodegenerative disease, and are transient and often heterogeneous, making them difficult to detect. Here we show an approach to track the development of amyloid oligomers in situ by room temperature, continuous wave (cw) 9 and 95 GHz EPR. Three amyloid peptides with the 2,2,6,6-tetramethyl-N-oxyl-4-amino-4-carboxylic acid (TOAC) spin label were synthesized by solid phase peptide synthesis: T0EZ (TKVKVLGDVIEVGG) with TOAC (T) at the N-terminus, T5EZ with TOAC in the middle (KVKVTGDVIEVG) and T12EZ with TOAC at the C-terminus (KVKVLGDVIEVTG).

A tailored multi-frequency EPR approach to accurately determine the magnetic resonance parameters of dynamic nuclear polarization agents: application to AMUPol.

To understand the dynamic nuclear polarization (DNP) enhancements of biradical polarizing agents, the magnetic resonance parameters need to be known. We describe a tailored EPR approach to accurately determine electron spin-spin coupling parameters using a combination of standard (9 GHz), high (95 GHz) and ultra-high (275 GHz) frequency EPR. Comparing liquid- and frozen-solution continuous-wave EPR spectra provides accurate anisotropic dipolar interaction D and isotropic exchange interaction J parameters of the DNP biradical AMUPol.

Interaction of the amyloid β peptide with sodium dodecyl sulfate as a membrane-mimicking detergent.

The amyloid β (A β) peptide is important in the context of Alzheimer's disease, since it is one of the major components of the fibrils that constitute amyloid plaques. Agents that can influence fibril formation are important, and of those, membrane mimics are particularly relevant, because the hydrophobic part of A β suggests a possible membrane activity of the peptide. We employed spin-label EPR to investigate the aggregation process of A β1-40 in the presence of the sodium dodecyl sulfate (SDS) detergent as a membrane-mimicking agent.