Nanoscale Ordering of Magnetosomes Under the Influence of a Magnetic Field Investigated by Small‐Angle X‐Ray Scattering

Recently, the synthetic Rhodospirillum rubrum ‘magneticum’ has been shown to enable the light‐driven production of magnetosomes (MAGs) in high yields. These membrane‐enveloped magnetic nanoparticles represent promising alternatives to their chemically synthesized analogs for many applications in the biotechnological and biomedical field. However, in contrast to native MAGs naturally produced by magnetotactic bacteria, little is known about the recombinant particles from R. rubrum ‘magneticum’ with regard to their magnetic field‐dependent structure. Small‐angle X‐ray scattering patterns reveal a pronounced anisotropy, attributed to chain formation and alignment of MAGs in the presence of a magnetic field. Directional ordering effects were observed and modeled using a Monte‐Carlo approach, which enables the sampling of the corresponding particle size‐ and orientation distributions. The magnetic field‐induced ordering was found to follow a modified Langevin function in accordance with the alignment process under thermal fluctuations. As the strength of the magnetic field increases, MAGs form chains that organize into a three‐dimensional arrangement. These findings provide critical insights into the assembly behavior of MAGs, which is vital for potential applications that are based on magnetic fields.