Frankfurt Institute for Advanced Studies

About: Frankfurt Institute for Advanced Studies is a facility organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Baryon & Quark–gluon plasma. The organization has 798 authors who have published 2733 publications receiving 82799 citations. The organization is also known as: FIAS.

Particle number fluctuations in the microcanonical ensemble

Abstract: Particle number fluctuations are studied in the microcanonical ensemble. For the Boltzmann statistics we deduce exact analytical formulas for the microcanonical partition functions in the case of noninteracting massless neutral particles and charged particles with zero net charge. The particle number fluctuations are calculated and we find that in the microcanonical ensemble they are suppressed in comparison to the fluctuations in the canonical and grand canonical ensembles. This remains valid in the thermodynamic limit too, so that the well-known equivalence of all statistical ensembles refers to average quantities, but does not apply to fluctuations. In the thermodynamic limit we are able to calculate the particle number fluctuations in the system of massive bosons and fermions when the exact conservation laws of both the energy and charge are taken into account.

Amplitude and phase effects on the synchronization of delay-coupled oscillators

Abstract: We consider the behavior of Stuart-Landau oscillators as generic limit-cycle oscillators when they are interacting with delay. We investigate the role of amplitude and phase instabilities in producing symmetry-breaking/restoring transitions. Using analytical and numerical methods we compare the dynamics of one oscillator with delayed feedback, two oscillators mutually coupled with delay, and two delay-coupled elements with self-feedback. Taking only the phase dynamics into account, no chaotic dynamics is observed, and the stability of the identical synchronization solution is the same in each of the three studied networks of delay-coupled elements. When allowing for a variable oscillation amplitude, the delay can induce amplitude instabilities. We provide analytical proof that, in case of two mutually coupled elements, the onset of an amplitude instability always results in antiphase oscillations, leading to a leader-laggard behavior in the chaotic regime. Adding self-feedback with the same strength and delay as the coupling stabilizes the system in the transverse direction and, thus, promotes the onset of identically synchronized behavior.

NMR protein structure determination in living E. coli cells using nonlinear sampling

Abstract: The cell is a crowded environment in which proteins interact specifically with other proteins, nucleic acids, cofactors and ligands. Atomic resolution structural explanation of proteins functioning in this environment is a main goal of biochemical research. Recent improvements to nuclear magnetic resonance (NMR) hardware and methodology allow the measurement of high-resolution heteronuclear multidimensional NMR spectra of macromolecules in living cells (in-cell NMR). In this study, we describe a protocol for the stable isotope ((13)C, (15)N and (2)H) labeling and structure determination of proteins overexpressed in Escherichia coli cells exclusively on the basis of information obtained in living cells. The protocol combines the preparation of the protein in E. coli cells, the rapid measurement of the three-dimensional (3D) NMR spectra by nonlinear sampling of the indirectly acquired dimensions, structure calculation and structure refinement. Under favorable circumstances, this in-cell NMR approach can provide high-resolution 3D structures of proteins in living environments. The protocol has been used to solve the first 3D structure of a protein in living cells for the putative heavy metal-binding protein TTHA1718 from Thermus thermophilus HB8 overexpressed in E. coli cells. As no protein purification is necessary, a sample for in-cell NMR measurements can be obtained within 2-3 d. With the nonlinear sampling scheme, the duration of each 3D experiment can be reduced to 2-3 h. Once chemical shift assignments and NOESY peak lists have been prepared, structure calculation with the program CYANA and energy refinement can be completed in less than 1 h on a powerful computer system.