Speaker
Felix Roosen-Runge
(Division of Physical Chemistry, Lund University)
Description
Information on protein dynamics is of central importance for the understanding how biological
function is effectuated by individual proteins as well as by well-adjusted interaction cascades within
the crowded cytoplasm. Protein dynamics comprises a hierarchy of processes ranging from
fluctuations of side chains and the backbone over interdomain motions to self-diffusion of the entire
macromolecule and collective and cage diffusion characterizing the structural relaxation in crowded
protein solutions. The broad distribution of time scales from pico- to microseconds, and the variety
of dynamical processes including simple as well as confined, anomalous diffusion renders
investigating protein dynamics a challenging research field.
In this context, quasi-elastic neutron scattering (QENS) provides unique information on both the
nature of the underlying dynamical process and the related geometry of dynamical confinement.
Neutron backscattering (NBS) and neutron spin echo (NSE) spectroscopy have proven particularly
relevant for proteins in solutions, as their instrumental time scales around nanoseconds allow to
access simultaneously global and internal dynamics. After a brief overview on the key
characteristics of QENS techniques, the scientific potential of QENS for protein dynamics will be
examplified with two recent case studies.
First, the changes of hierarchical protein dynamics upon thermal denaturation have been studied by
both real-time monitoring and an additional detailed characterization of selected states [1,2].
Interestingly, while global dynamics are irreversibly arrested after denaturation, local internal
dynamics change reversibly, suggesting that localized internal dynamics are mainly affected by
basic physicochemical properties.
Second, scenarios of dynamical arrest have been examined in solutions of α, β and γ crystallins as
model systems for the eye lens with potential implications for the understanding of cataract and
presbyopia. While α crystallin solutions behave similar to hard-sphere systems with a repulsive
glass transition at high volume fraction, γB crystallin experiences a dramatic slowing down of cage
diffusion already at comparably low volume fractions, suggesting an dynamical arrest driven by
weak anisotropic attractions [3,4].
[1] M Grimaldo, F Roosen-Runge, et al. Phys. Chem. Chem. Phys. (2015) 17, 4645-4655
[2] M Hennig, F Roosen-Runge, et al. Soft Matter (2012) 8, 1628-1633
[3] S. Bucciarelli, J.S. Myung, et al. Sci. Adv. (2016) 2, e1601432
[4] S. Bucciarelli, L. Casal-Dujat, et al. J. Phys. Chem. Lett. (2015) 6, 4470–4474
Primary author
Felix Roosen-Runge
(Division of Physical Chemistry, Lund University)
