261: MHz-XPCS reveals anomalous ferritin diffusion and nanoscale cage trapping

Girelli et al., Nature Communications - MHz-XPCS of ferritin solutions at EuXFEL shows anomalous, cage-trapped protein diffusion with reduced long-time transport and ~1.2 nm rattling at high concentration. Key terms: ferritin, MHz-XPCS, anomalous diffusion, cage effects, hydrodynamic function. Study Highlights:The study probes crowded ferritin solutions using megahertz X-ray Photon Correlation Spectroscopy (MHz-XPCS) at EuXFEL combined with SAXS and δγ-theory modeling. Intensity autocorrelation functions g2(q,t) become non-exponential at high concentrations, and double-exponential analysis yields short- and long-time diffusion components with Dlong/Dshort ≈ 0.12 ± 0.04 at 730 mg/ml and an interaction time estimated near 4.25 µs. δγ-theory of hydrodynamically interacting spheres reproduces the q-dependent hydrodynamic function only when a scaling factor tied to direct protein interactions is included, indicating hydrodynamics set the q-dependence while direct forces reduce overall self-diffusion. Cage analysis finds an average rattling displacement δ ≈ 1.0 ± 0.3 nm for ≈89% of proteins, implying cage-trapping substantially slows molecular transport with consequences for ferritin-based drug delivery. Conclusion:MHz-XPCS measurements and δγ-theory modeling demonstrate that crowded ferritin solutions exhibit anomalous, cage-trapped diffusion with separate short- and long-time components and markedly reduced self-diffusion, indicating slower molecular transport under crowding. Music:Enjoy the music based on this article at the end of the episode. Article title:Coherent X-rays reveal anomalous molecular diffusion and cage effects in crowded protein solutions First author:Girelli Journal:Nature Communications DOI:10.1038/s41467-025-66972-6 Reference:Girelli, A., Bin, M., Filianina, M. et al. Coherent X-rays reveal anomalous molecular diffusion and cage effects in crowded protein solutions. Nat Commun (2025). https://doi.org/10.1038/s41467-025-66972-6 License:This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) - https://creativecommons.org/licenses/by/4.0/ Support:Base by Base – Stripe donations: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00 Official website https://basebybase.com On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics. Episode link: https://basebybase.com/episodes/ferritin-anomalous-diffusion-xpcs QC:This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-01-16. QC Scope:- article metadata and core scientific claims from the narration- excludes analogies, intro/outro, and music- transcript coverage: Audited the spoken content for the central findings and methods: crowded diffusion in ferritin solutions, MHz-XPCS techniques at EuXFEL, evidence for cage trapping, two diffusion regimes (Dshort and Dlong), interaction time, cage displacement, δγ-theory modeling with a scaling factor, and implications for diffusion in- transcript topics: Crowding and diffusion in cellular-like environments; MHz-XPCS methodology at EuXFEL; Ferritin as a model system; Anomalous diffusion and cage effects; Short-time vs long-time diffusion; Two-component diffusion: Dshort and Dlong QC Summary:- factual score: 10/10- metadata score: 10/10- supported core claims: 6- claims flagged for review: 0- metadata checks passed: 4- metadata issues found: 0 Metadata Audited:- article_doi- article_title- article_journal- license Factual Items Audited:- Anomalous diffusion observed in crowded ferritin solutions- Cage trapping as a mechani...