Speakers
Description
Conformational dynamics of proteins studied by time resolved small angle X-ray scattering combined with THz irradiation
Proteins rely on conformational changes to perform complex biochemical tasks.
This dynamic plasticity can be modeled by large scale vibrational modes that
have theoretical resonance frequencies in the range of $0.3$ to $6$ THz and can
therefore be triggered by THz radiation. Since these modes are associated with
conformational changes of several Angstrom to nm, they can be probed by small
angle X-ray scattering (SAXS). We aim to observe synchronized collective
vibrational modes in time resolved SAXS experiments with external THz
excitation. Apart from standard protein samples, we aim to investigate porcine
microtubules and human dipeptidyl peptidase 3 (DPP3). These systems exhibit
large scale conformational plasticity and characeristic SAXS profiles.
The major challenge for this type of experiment is the sample environment. The
harsh conditions under X-ray irradiation require constant material flow during
the SAXS experiment. Simultaneous irradiation with THz radiations requires a
thin liquid film ($<200 \mu \rm{m}$) to compensate for the high absorption
coefficient of aqueous solutions in the THz regime. Furthermore, window
materials for X-ray and THz transmission have to be chosen with great care to
avoid excess absorption or scattering artefacts. We design flow cells that
fullfill these requirements to enable combined SAXS-THz experiments.
