Latest documents http://publikationen.stub.uni-frankfurt.de/index/index/ Mon, 13 May 2013 10:46:32 +0200 Mon, 13 May 2013 10:46:32 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29871 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29871 Mon, 13 May 2013 10:46:32 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29732 The universal biological energy currency adenosine triphosphate (ATP) is synthesized by the F1Fo-ATP synthase in most living organisms. The overall structure and function of F-type ATPases is conserved in the different organisms. The F1Fo-ATP synthase consist of two domains; the soluble F1 complex has the subunit stoichiometry α3β3γδε and the membrane embedded Fo complex consists of subunits ab2c10-15 in its simplest form found in bacteria. F1 and Fo both function as reversible rotary motors that are connected by a central stalk (γε) and a peripheral stalk (b2δ). For ATP synthesis, the electrochemical energy formed by a proton or sodium ion gradient is required. The ion translocation across the Fo subcomplex induces torque in the motor part of the enzyme (cnγε), which causes conformational changes in the α3β3 domain leading to ATP synthesis from ADP and inorganic phosphate (Pi) catalyzed in the β-subunits. ATP hydrolysis causes a reverse torque in the Fo subcomplex triggering uphill ion translocation from cytoplasm to periplasm, and the enzyme functions as an ion pump. The ATP synthesis mechanism is well understood, since several high-resolution structures of F1 are available. In contrast, the ion translocation mechanism across the membrane, mediated by the Fo subcomplex, is not understood in its structural detail. Subunit a and the c-ring form an ion pathway, but subunit b is needed to form an active ion translocation pathway in both H+- and Na+-dependent systems. Several high-resolution structures of c-rings have provided insights in the ion translocation mechanism. The different ion translocation models based on biochemical, biophysical and structural analysis are in agreement in the fact that ions are translocated through a periplasmic ion access pathway in subunit a to the middle of the membrane and there to the binding site of a c-subunit. After almost a whole rotation of the c-ring the ion returns into the a-c interface, where it can be released to the cytoplasm. In the different models the cytoplasmic access pathway has been proposed to be located in subunit a, at the a-c interface or within the c-ring. The driving force of torque generation has been proposed to be the pH gradient or membrane potential. Several biochemical studies show that a conserved arginine in helix four of subunit a (R226 in Ilyobacter tartaricus or R210 in Escherichia coli)plays a critical role in the ion translocation. The arginine has been proposed to function as an electrostatic separator between the cytoplasmic and periplasmic pathways and as a mediator of the ion exchange into the c-ring ion-binding site. Structural data of a related enzyme (V1Vo-ATPase from Thermus thermophilus) has provided insight into the helical arrangement of the ion translocating subunits I and Lring (related to subunit a and the c-ring). These structures indicated a small interface between subunit I and the L-ring, and two four-helix bundles in the N-terminal domain of subunit I were proposed to build the periplasmic and cytoplasmic ion pathways. To comprehend the ion-translocation and torque generation mechanism in F1Fo-ATP synthase, structural data of an intact a-c complex is needed. The goal of this work was to obtain structural data of subunit a, most preferably in a complex with the c-ring or additionally with subunit b. Therefore, a new purification procedure for the I. tartaricus Fo-subcomplex, heterologously expressed in E. coli cells, was established. The purified Fo was characterized biochemically and by Laserinduced liquid bead ion desorption mass spectrometry (LILBID-MS). These analyses showed that pure and completely assembled Fo containing all its subunits in the correct stoichiometry (ab2c11) was obtained. The purified Fo complex was stable at 4°C for several months and at room temperature in the presence of lipids for several weeks. A lipid analysis was performed by thin-layer chromatography (TLC) to investigate the qualitative lipid composition of I. tartaricus whole lipid extract and various I. tartaricus F1Fo isolates. The whole lipid extract contained PC, PG and PE lipids and probably cardiolipin. PC, PG and PE lipids were bound to wild type I. tartaricus F1Fo, whereas recombinant I. tartaricus F1Fo did not have any bound lipids, but was able to bind the synthetic lipids POPC and POPG if they were provided during the purification. For subsequent structural studies the purified Fo was subjected to two-dimensional (2D) crystallization trials. Vesicles and sheets tightly packed with protein and crystals with a rare plane group for I. tartaricus c11 (p121) were obtained. The c-ring was visible in the CCD images, and immunogold-labeling revealed the presence of the His-tagged a-subunit in the reconstituted vesicles. Furthermore, atomic force microscopy (AFM) imaging showed protein densities next to the c-rings, which protruded less from the membrane (0.4±0.1 nm) than the c-ring (0.7±0.1 nm). These protein densities presumably belonged to subunit a. Cryo-electronmicroscopy (cryo-EM) was used to collect data of the p121 crystals and a merged projection density map was calculated to 7.0 Å resolution. The unit cell of the crystals (81 × 252 Å) contained two asymmetric units with three c-rings in each and next to the c11-rings new prominent densities were visible. In each extra density up to 7 transmembrane helices were visible, belonging to the stator subunit a and/or subunit b. To elucidate whether there are conserved elements in the three extra densities non-crystallographic averaging was applied using a single-particle approach. Six possible arrangements for the c-rings and the extra densities were identified and used for the averaging. The extra densities were enhanced only in one of the possible arrangements. The average showed a four-helix bundle and a fifth helix in close proximity to the c-ring. Two more helices were present in each position but their position was ambivalent. The data obtained in this work provides the first insight in the helical arrangement in the a-c interface of F1Fo-ATP synthase. Jonna Hakulinen doctoralthesis http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29732 Wed, 10 Apr 2013 08:33:40 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29147 In the context of nationwide protests 2009 also students of the faculty of medicine/dentistry at Goethe-University in Frankfurt demanded more transparency and communication. To satisfy these demands, a web 2.0-tool offered an innovative solution: A blog-based online-magazine for students and other faculty-members. The online-magazine „PULS.“ is realized with the share-ware blog-software (wordpress version 3.1.3) and is conceived and written by an online-journalist. „PULS.“ is available from https://newsmagazin.puls.med.uni-frankfurt.de/wp/. The articles are generated from own investigations and from ideas of different groups of the faculty– deanship, students and lecturers. A user-analysis is conducted with the open-source software Piwik and considers the data security. Additionally, every year an anonymous online-user-survey (Survey Monkey) is conducted. “PULS.” is continuously online since 14.02.2010 and has published 806 articles (state: 27.11.2012) and has about 2400 readers monthly. The content focuses on the needs of Frankfurt medical students. The close cooperation with different groups of the faculty - deanship, students and lecturers - furthermore guarantees themes relevant to the academic faculty. “PULS.” flanks complex projects and decisions with background-information and communicates them understandable. The user-evaluation shows a growing number of readers and a high acceptance for the online-magazine, its themes and its style. The web 2.0-tool “Blog” and the web-specific language comply with media habits of the main target group, the students of the faculty medicine/dentistry. Thus, “PULS.” has proven as a suitable and strategic instrument. It pushes towards a higher transparency, more communication and a stronger identification of the students with their faculty. Bettina Wurche; Gertrud Klauer; Frank Nürnberger article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29147 Wed, 13 Mar 2013 10:48:36 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27860 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27860 Fri, 01 Feb 2013 15:00:09 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27519 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27519 Fri, 30 Nov 2012 16:14:03 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27524 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27524 Fri, 30 Nov 2012 10:14:03 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27531 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27531 Mon, 26 Nov 2012 16:26:29 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26993 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26993 Mon, 26 Nov 2012 15:28:54 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27458 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27458 Wed, 21 Nov 2012 15:49:45 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26998 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26998 Tue, 06 Nov 2012 15:45:11 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26989 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26989 Fri, 02 Nov 2012 11:36:20 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26830 Measurements of transverse momentum fluctuations can be used to determine the shear viscosity [1]. We use current data to estimate the viscosity-to-entropy ratio in the range from 0.08 to 0.3, and discuss how future measurements can reduce this uncertainty. Sean Gavin; Mohamed Abdel-Aziz article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26830 Fri, 02 Nov 2012 09:39:36 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26816 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26816 Tue, 30 Oct 2012 10:38:59 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27018 The simultaneous recording of the activity of many neurons poses challenges for multivariate data analysis. Here, we propose a general scheme of reconstruction of the functional network from spike train recordings. Effective, causal interactions are estimated by fitting generalized linear models on the neural responses, incorporating effects of the neurons’ self-history, of input from other neurons in the recorded network and of modulation by an external stimulus. The coupling terms arising from synaptic input can be transformed by thresholding into a binary connectivity matrix which is directed. Each link between two neurons represents a causal influence from one neuron to the other, given the observation of all other neurons from the population. The resulting graph is analyzed with respect to small-world and scale-free properties using quantitative measures for directed networks. Such graph-theoretic analyses have been performed on many complex dynamic networks, including the connectivity structure between different brain areas. Only few studies have attempted to look at the structure of cortical neural networks on the level of individual neurons. Here, using multi-electrode recordings from the visual system of the awake monkey, we find that cortical networks lack scale-free behavior, but show a small, but significant small-world structure. Assuming a simple distance-dependent probabilistic wiring between neurons, we find that this connectivity structure can account for all of the networks’ observed small-world-ness. Moreover, for multi-electrode recordings the sampling of neurons is not uniform across the population. We show that the small-world-ness obtained by such a localized sub-sampling overestimates the strength of the true small-world structure of the network. This bias is likely to be present in all previous experiments based on multi-electrode recordings. Felipe Gerhard; Gordon Pipa; Bruss Lima; Sergio Neuenschwander; Wulfram Gerstner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27018 Tue, 30 Oct 2012 08:39:56 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26971 GoeTheo ist ein Projekt, welches der Transparenz des Fachbereichs und der Informationsweitergabe an Studierende, Förderer und Interessierte dient. Die Fachbereichszeitschrift ist eine gemeinsame Publikation des Vereins der Freunde und Förderer der Evangelischen Theologie in Frankfurt/Main und des Fachbereichs Evangelische Theologie der Goethe-Universität. Seit Wintersemester 2009/10 erscheint GoeTheo immer zum Semesteranfang und informiert über die Lehrveranstaltungen des kommenden Semesters, sowie über aktuelle Entwicklungen des Fachbereichs in Forschung und Lehre. periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26971 Mon, 29 Oct 2012 12:22:53 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26657 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26657 Tue, 09 Oct 2012 15:27:29 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26604 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26604 Mon, 08 Oct 2012 15:49:51 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26419 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/26419 Fri, 05 Oct 2012 12:51:06 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/25223 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/25223 Tue, 04 Sep 2012 11:15:54 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/25788 Zweimonatlich erscheinender kostenloser elektronischer Newsletter des Instituts für sozial-ökologische Forschung (ISOE). periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/25788 Tue, 21 Aug 2012 16:54:08 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/24181 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/24181 Tue, 03 Apr 2012 10:24:18 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/23609 Der "flur_funk" ist die Zeitung der Fachschaften 03 und 04 und erscheint idealerweise 3 mal im Semester. Hier findet ihr Berichte aus dem Fachbereich, Neues zu aktuellen Entwicklungen der Lehre und auch Dinge darüber hinaus. Einzelhefte s.u. URL. periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/23609 Wed, 21 Dec 2011 00:00:00 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/23627 periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/23627 Wed, 14 Dec 2011 00:00:00 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/19255 This paper discusses the effect of capital regulation on the risk taking behavior of commercial banks. We first theoretically show that capital regulation works differently in different market structures of banking sectors. In lowly concentrated markets, capital regulation is effective in mitigating risk taking behavior because banks' franchise values are low and banks have incentives to pursue risky strategies in order to increase their franchise values. If franchise values are high, on the other hand, the effect of capital regulation on bank risk taking is ambiguous as banks lack those incentives. We then test the model predictions on a cross-country sample including 421 commercial banks from 61 countries. We find that capital regulation is effective in mitigating risk taking only in markets with a low degree of concentration. The results remain robust after accounting for financial sector development, legal system effciency, and for other country and bank-specific characteristics. Keywords: Banks, market structure, risk shifting, franchise value, capital regulation JEL Classifications: G21, G28 Patrick Behr; Reinhard H. Schmidt; Ru Xie workingpaper http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/19255 Mon, 23 May 2011 16:34:56 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/20977 ProtoSociology is an interdisciplinary journal which crosses the borders of philosophy, social sciences, and their corresponding disciplines. Each issue concentrates on a specific topic taken from the current discussion to which scientists from different fields contribute the results of their research. ProtoSociology is further a project that examines the nature of mind, language and social systems. In this context theoretical work has been done by investigating such theoretical concepts like interpretation and (social) action, globalization, the global world-system, social evolution, and the sociology of membership. Our purpose is to initiate and enforce basic research on relevant topics from different perspectives and traditions. periodical http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/20977 Tue, 22 Feb 2011 13:26:31 +0100