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Thursday,
07 May 2026 |
Video-Recording for any system with MP4-support - Video.mp4 (ca. 321 Mb) |
15:15 – 16:05 |
"When Diffusion Slows Down:
How
Crowding, Hydrodynamics and Softness Shape Protein Motion"
Prof. Christian Gutt
(Universität
Siegen)
Abstract:
Biological environments are highly
crowded, with macromolecular volume fractions
often exceeding 30–40%. In such
conditions, protein motion deviates strongly 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 will present recent advances using
megahertz X-ray photon correlation
spectroscopy (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 interplay of transient
caging, hydrodynamic interactions, and particle
softness, leading to anomalous,
non-exponential relaxation dynamics. Across model
systems ranging from globular proteins in
polymeric crowders to native lipoproteins
in dense biological fluids, we observe a
strong coupling between structure and
dynamics, including collective
slowing-down at characteristic length scales and
pronounced deviations from classical
diffusion–viscosity relations.
Together, these results establish a
physical picture in which protein transport is
controlled not only by excluded volume,
but by interaction-specific effects and many-
body hydrodynamics. This framework
provides new insight into molecular motion in
biological media and has implications for
processes ranging from intracellular
transport to drug delivery in complex
fluids.
Das Anthuparambil, N.
et al.
Lipoprotein diffusion in dense yolk plasma
is governed by softness, hydrodynamics,
and caging: Insights from MHz-XPCS. PNAS
123, e2519681123 (2026)
Dargasz, M. et al.
Depletion-induced interactions modulate
nanoscale protein diffusion in polymeric
crowder solutions.
PNAS (2026, in review / draft)
Girelli, A. et al.
Coherent X-rays reveal anomalous molecular
diffusion and cage effects in crowded
protein solutions.
Nature Communications 16, 10814 (2025)
Reiser, M. et al.
Resolving molecular diffusion and
aggregation of antibody proteins with megahertz
X-ray free-electron laser pulses.
Nature Communications 13, 5528 (2022)