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Berlin, Germany

The Humboldt University of Berlin is one of Berlin's oldest universities, founded in 1810 as the University of Berlin by the liberal Prussian educational reformer and linguist Wilhelm von Humboldt, whose university model has strongly influenced other European and Western universities. From 1828 it was known as the Frederick William University , and later also as the Universität unter den Linden after its location. In 1949, it changed its name to Humboldt-Universität in honour of both its founder Wilhelm and his brother, geographer Alexander von Humboldt.In 2012, the Humboldt University of Berlin was one of eleven German universities to win in the German Universities Excellence Initiative, a national competition for universities organized by the German Federal Government. The university has educated 29 nobel prize winners and is considered one of the most prestigious universities in Europe overall as well as one of the most prestigious universities worldwide for arts and humanities. Wikipedia.

Dobbek H.,Humboldt University of Berlin
Coordination Chemistry Reviews | Year: 2011

This review provides an overview of the contributions of protein X-ray crystallography to the field of pyranopterin-containing W/Mo-enzymes. Several crystal structures for all of the four different families of pyranopterin-containing enzymes have been determined in recent years allowing one to compare overall folds and active site architectures. Especially within the dimethylsulfoxide reductase family and the Mo-containing hydroxylases a diversity of Mo/W-ligands has been discovered, challenging the earlier proposed functions of individual active site components. Reinterpretations of structures and the use of enzyme variants and complexes with inhibitors and slow substrate provided further insights, which will be discussed for the individual enzymes. © 2010 Elsevier B.V.

Brettschneider C.,Humboldt University of Berlin
Molecular systems biology | Year: 2010

The circadian rhythm of the cyanobacterium Synechococcus elongatus is controlled by three proteins, KaiA, KaiB, and KaiC. In a test tube, these proteins form complexes of various stoichiometry and the average phosphorylation level of KaiC exhibits robust circadian oscillations in the presence of ATP. Using mathematical modeling, we were able to reproduce quantitatively the experimentally observed phosphorylation dynamics of the KaiABC clockwork in vitro. We thereby identified a highly non-linear feedback loop through KaiA inactivation as the key synchronization mechanism of KaiC phosphorylation. By using the novel method of native mass spectrometry, we confirm the theoretically predicted complex formation dynamics and show that inactivation of KaiA is a consequence of sequestration by KaiC hexamers and KaiBC complexes. To test further the predictive power of the mathematical model, we reproduced the observed phase synchronization dynamics on entrainment by temperature cycles. Our model gives strong evidence that the underlying entrainment mechanism arises from a temperature-dependent change in the abundance of KaiAC and KaiBC complexes.

Blaison C.,Humboldt University of Berlin
Emotion (Washington, D.C.) | Year: 2012

The Affect Misattribution Procedure (AMP; Payne, Cheng, Govorun, & Stewart, 2005) is an important tool in implicit social cognition research, but little is known about its underlying mechanisms. This paper investigates whether, as the name implies, affect-based processes really underlie the AMP. We used a modified AMP that enabled us to separate the influence of affective and nonaffective processes. In three studies, evidence for the implication of nonaffective processes was consistently found. In contrast, there was no evidence for affect-based processes. Thus, the AMP rather seems cold than hot. The generalizability of the results obtained with the modified AMP is discussed. (PsycINFO Database Record (c) 2012 APA, all rights reserved).

Hasenbusch M.,Humboldt University of Berlin
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We study the spin-1/2 Ising model and the Blume-Capel model at various values of the parameter D on the simple cubic lattice. To this end we perform Monte Carlo simulations using a hybrid of the local Metropolis, the single cluster and the wall cluster algorithm. Using finite size scaling we determine the value D =0.656 (20) of the parameter D, where leading corrections to scaling vanish. We find ω=0.832 (6) for the exponent of leading corrections to scaling. In order to compute accurate estimates of critical exponents, we construct improved observables that have a small amplitude of the leading correction for any model. Analyzing data obtained for D=0.641 and 0.655 on lattices of a linear size up to L=360 we obtain ν=0.63002 (10) and η=0.03627 (10). We compare our results with those obtained from previous Monte Carlo simulations and high-temperature series expansions of lattice models, by using field-theoretic methods and experiments. © 2010 The American Physical Society.

Rudiger S.,Humboldt University of Berlin
Physics Reports | Year: 2014

Cellular signaling operates in a noisy environment shaped by low molecular concentrations and cellular heterogeneity. For calcium release through intracellular channels-one of the most important cellular signaling mechanisms-feedback by liberated calcium endows fluctuations with critical functions in signal generation and formation. In this review it is first described, under which general conditions the environment makes stochasticity relevant, and which conditions allow approximating or deterministic equations. This analysis provides a framework, in which one can deduce an efficient hybrid description combining stochastic and deterministic evolution laws. Within the hybrid approach, Markov chains model gating of channels, while the concentrations of calcium and calcium binding molecules (buffers) are described by reaction-diffusion equations. The article further focuses on the spatial representation of subcellular calcium domains related to intracellular calcium channels. It presents analysis for single channels and clusters of channels and reviews the effects of buffers on the calcium release. For clustered channels, we discuss the application and validity of coarse-graining as well as approaches based on continuous gating variables (Fokker-Planck and chemical Langevin equations). Comparison with recent experiments substantiates the stochastic and spatial approach, identifies minimal requirements for a realistic modeling, and facilitates an understanding of collective channel behavior. At the end of the review, implications of stochastic and local modeling for the generation and properties of cell-wide release and the integration of calcium dynamics into cellular signaling models are discussed. © 2013.

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