Integrated Calendar

Thermal motions of atoms is an ever-present phenomenon in all of solid state physics. Phonons, quanta of heat, is the quasiparticule used to describe thermal motion in solids. Under normal conditions phonons are the dominant mechanism that govern transport and the largest contribution to entropy. I want to understand how phonons evolve in time, temperature, and how they behave when they interact strongly with each other or other quasiparticles.
The inherent disorder in thermal motions makes theoretical predictions challenging. I will present methodological developments in finite temperature first principles simulations, specifically targeting strongly anharmonic systems. The method employs model Hamiltonians that explicitly depend on temperature. I will present applications pertaining to thermal conductivity, inelastic neutron spectra and phase stabilities, reproducing non-trivial temperature dependencies.

The conserved signal recognition particle (SRP) system is essential for the biogenesis of integral membrane proteins (IMPs). The E. coli membrane associated SRP-receptor FtsY is a key player in the SRP system, although very little is known about its targeting and association with the membrane. Previous work done in our lab showed that FtsY targeting to the membrane is of a co-translational nature; during its translation, a specific domain emerges out of the ribosome and serves as the signal for membrane localization. This domain was characterized both functionally and structurally, but the manner by which this entire ribosome-nascent chain complex targets the membrane remains mostly unclear. In order to shed light on this mechanism, we have developed a co-translational and in-vivo site-specific crosslinking system. Using ribosome stalling-sequence and amber suppression, we are trying to identify direct co-translational protein-protein interactions involved in the membrane docking event of FtsY.

DOC2B is a high-affinity Ca2+ sensor, which translocates from the cytosol to the plasma membrane (PM) upon Ca2+ elevation and regulates exocytosis by promoting priming and fusion. Its interaction with the PM depends both on calcium and on its C2 domains binding to phosphoinositides (PI(4,5)P2) at the PM. In the lecture, I will move from the level of protein structure and its targeting to PI(4,5)P2 via its effect on vesicle fusion in chromaffin cells up to its involvement in asynchronous release in neurons and its effects on neuronal network activity.