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SUMMARY:When Diffusion Slows Down: How Crowding\, Hydrodynamics\, and Soft
 ness Shape Protein Motion
DTSTART:20260507T131500Z
DTEND:20260507T141500Z
DTSTAMP:20260515T225700Z
UID:indico-event-9540@indico.fysik.su.se
DESCRIPTION:Speakers: Christian Gutt (University of Siegen)\n\nBiological 
 environments are highly crowded\, with macromolecular volume fractions oft
 en exceeding 30–40%. In such conditions\, protein motion deviates strong
 ly from simple Brownian diffusion\, yet the physical mechanisms governing 
 this behavior remain poorly understood due to a long-standing experimental
  gap at nanometer length scales and microsecond times. In this talk\, I wi
 ll present recent advances using megahertz X-ray photon correlation spectr
 oscopy (MHz-XPCS) at X-ray free-electron lasers to directly probe protein 
 dynamics in this previously inaccessible regime. These measurements reveal
  that protein motion in crowded environments is governed by a complex inte
 rplay of transient caging\, hydrodynamic interactions\, and particle softn
 ess\, leading to anomalous\, non-exponential relaxation dynamics. Across m
 odel systems ranging from globular proteins in polymeric crowders to nativ
 e lipoproteins in dense biological fluids\, we observe a strong coupling b
 etween structure and dynamics\, including collective slowing-down at chara
 cteristic length scales and pronounced deviations from classical diffusion
 –viscosity relations. Together\, these results establish a physical pict
 ure in which protein transport is controlled not only by excluded volume\,
  but by interaction-specific effects and many-body hydrodynamics. This fra
 mework provides new insight into molecular motion in biological media and 
 has implications for processes ranging from intracellular transport to dru
 g delivery in complex fluids.\nDas Anthuparambil\, N. et al.Lipoprotein di
 ffusion in dense yolk plasma is governed by softness\, hydrodynamics\, and
  caging: Insights from MHz-XPCS. PNAS 123\, e2519681123 (2026)\nDargasz\, 
 M. et al.Depletion-induced interactions modulate nanoscale protein diffusi
 on in polymeric crowder solutions.PNAS (2026\, in review / draft)\nGirelli
 \, A. et al.Coherent X-rays reveal anomalous molecular diffusion and cage 
 effects in crowded protein solutions.Nature Communications 16\, 10814 (202
 5)\nReiser\, M. et al.Resolving molecular diffusion and aggregation of ant
 ibody proteins with megahertz X-ray free-electron laser pulses.Nature Comm
 unications 13\, 5528 (2022)\n\nhttps://indico.fysik.su.se/event/9540/
URL:https://indico.fysik.su.se/event/9540/
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