Integrated Calendar

Molecular communication in biology is mediated by protein interactions. According to the current paradigm, the specificity and affinity required for these interactions are encoded in the precise complementarity of binding interfaces. Even proteins that are disordered under physiological conditions or that contain large unstructured regions commonly interact with well-structured binding sites on other biomolecules. We recently discovered the existence of an unexpected interaction mechanism: The two intrinsically disordered human proteins histone H1 and its nuclear chaperone prothymosin α associate in a one-to-one complex with picomolar affinity, but they fully retain their structural disorder, long-range flexibility, and highly dynamic character. Based on the close integration of single-molecule experiments, NMR, and molecular simulations, we obtain a detailed picture of this complex and show that the interaction can be explained by the large opposite net charge of the two proteins without requiring defined binding sites or interactions between specific individual residues

Chemokines and their receptors play critical roles in the progression of autoimmunity and inflammation and cancer. Typically, multiple chemokines are involved in the development of these pathologies. Indeed, targeting single chemokines or chemokine receptors has failed to achieve significant clinical benefits in treating autoimmunity and inflammation. In our work, promiscuous chemokine binding peptides that could bind and inhibit multiple inflammatory chemokines, such as CCL20, CCL2, CCL5, and CXCL9/10/11, were selected from phage display libraries. These peptides were cloned into human mutated immunoglobulin Fc-protein fusions (peptibodies). These peptibodies showed a significant inhibition of disease progression in a variety of animal models for autoimmunity, inflammation and cancer. Based on our peptibodies we develop HTP screening system which allow us the identification of novel anti chemokines small molecules.

The modern theories directed toward unifying gravitation with the three other fundamental interactions suggest variation of the fundamental constants. While the energy scale of such physics beyond the Standard Model is much higher than that currently attainable by particle accelerators the variation of the fundamental constants may nevertheless be detectable via precision measurements at low energies. I will give an overview of various searches for new physics with atomic clocks and focus on proposals for future experiments with highly charged ions. Proposal for tests of Lorentz symmetry with Yb+ and highly charged ions are also presented.

The perovskite crystal structure hosts a wealth of intriguing properties, and the renaissance of interest in halide (and hybrid organic-inorganic) perovskites (HOIPs) has further broadened the palette of exciting physical phenomena. Breakthroughs in HOIP synthesis, characterization, and solar cell design have led to remarkable increases in reported photovoltaic efficiency.

However, the observed long carrier lifetime and PV performance have eluded comprehensive physical justification. The hybrid perovskites serve as an enigmatic crossroads of physics. Concepts from crystalline band theory, molecular physics, liquids, and phase transitions have been applied with some success, but the observations of HOIPs make it clear that none of these conceptual frameworks completely fits. In this talk, recent theoretical progress in understanding HOIPs will be reviewed and integrated with experimental findings. The large amplitude motions of HOIPs will be highlighted, including ionic diffusion, anharmonic phonons, and dynamic incipient order on various length and time scales. The intricate relationships between correlated structural fluctuations, polar order, and excited charge carrier dynamics will also be discussed.

Intrinsically disordered proteins (IDPs) are ubiquitously found in eukaryotic systems. Their lack of a well-defined structure suggests that their broad conformational ensemble is functionally advantageous. Here, we use single-molecule fluorescence resonance energy transfer (smFRET) to investigate the link between the polymer properties of one important IDP network system and the process of coupled binding and folding that leads to functional complexes. Our results suggest that the properties of the disordered IDP ensemble and the stability of the functional complexes are strongly correlated.

Thermodynamic considerations suggest correlation between efficient photo conversion and bright luminescence, in practice we do not usually see that. However, lead-halide perovskites do show excellent efficiencies in both photovoltaic and light-emitting applications. We study perovskite nanocrystals as a model system to further understand the origin of their enigmatic properties.
Low-dimensional colloidal nano-crystals of cesium lead halide demonstrate exceptionally bright emission without shelling and unusual room temperature transformation not common to other semiconductors nanocrystals. These properties suggest a near equilibrium nanocrystal system. In a series of studies we follow the formation and transformations of these nanocrystals. We can now grow quantum confined cesium lead halide nanocrystals with cube, plate and wire shapes and with atomic precision. We demonstrate how quantum confinement and dimensionality dictate the exciton behavior and photophysical properties of these crystals. In the case of two dimensional nanoplates we observe strong quantum confinement of the excitons.(1) In the case of nanowires we show that broken symmetry manifests in significant polarized emission. These nanowires can be further utilized through 3D printing and alignment process to fabricate highly polarized functional metamaterials. In addition to the synthetic shape control, further control of the optical properties is achieved by changing the anion composition. The “softness” of the perovskite crystal allows post synthetic room temperature transformations that tune the material band-gap values throughout the visible spectrum.(2-3) The resulting high quantum yield, combined with the synthetic versatility and facile transformations, position colloidal perovskites as a unique model system for the study of charge dynamics and thermodynamic transformations at the nanoscale, contributing to the understanding of next generation materials for energy. Future developments in perovskites, leading to more stable and lead free materials will also be discussed

To thermodynamically address quantum nanoscopic scenarios that involve very small heat sources and strong system-bath correlation, we suggest a new framework that is based on the principle of passivity. Passivity allows to get many thermodynamic inequalities that constrain observables that were so far outside the scope of thermodynamics. As an example we derive lower and upper bounds on the system-bath energy covariance in the Jaynes-Cummings model (spin-oscillator interaction). Using a stronger version of the passivity principle, we extend the second law to handle initial system-bath correlation (which is common in microscopic strong system-bath coupling scenarios). In addition, it is shown that passivity-based inequalities can detect "sub-Maxwellian” demons that apply a feedback that is too subtle to be detected using the standard second law. Finally an intrinsically quantum feature of strong passivity is exploited to assign a thermodynamic cost for quantum coherence generation.