Fluorescence-excitation and emission spectroscopy on single FMO complexes

In green-sulfur bacteria sunlight is absorbed by antenna structures termed chlorosomes, and transferred to the RC via the Fenna-Matthews-Olson (FMO) complex. FMO consists of three monomers arranged in C3 symmetry where each monomer accommodates eight Bacteriochlorophyll a (BChl a) molecules. It was the first pigment-protein complex for which the structure has been determined with high resolution and since then this complex has been the subject of numerous studies both experimentally and theoretically. Here we report about fluorescence-excitation spectroscopy as well as emission spectroscopy from individual FMO complexes at low temperatures. The individual FMO complexes are subjected to very fast spectral fluctuations smearing out any possible different information from the ensemble data that were recorded under the same experimental conditions. In other words, on the time scales that are experimentally accessible by single-molecule techniques, the FMO complex exhibits ergodic behaviour

A stable FSI algorithm for light rigid bodies in compressible flow

In this article we describe a stable partitioned algorithm that overcomes the added mass instability arising in fluid-structure interactions of light rigid bodies and inviscid compressible flow. The new algorithm is stable even for bodies with zero mass and zero moments of inertia. The approach is based on a local characteristic projection of the force on the rigid body and is a natural extension of the recently developed algorithm for coupling compressible flow and deformable bodies. Normal mode analysis is used to prove the stability of the approximation for a one-dimensional model problem and numerical computations confirm these results. In multiple space dimensions the approach naturally reveals the form of the added mass tensors in the equations governing the motion of the rigid body. These tensors, which depend on certain surface integrals of the fluid impedance, couple the translational and angular velocities of the body. Numerical results in two space dimensions, based on the use of moving overlapping grids and adaptive mesh refinement, demonstrate the behavior and efficacy of the new scheme. These results include the simulation of the difficult problem of a shock impacting an ellipse of zero mass.Comment: 32 pages, 20 figure

Die Bewertungsnotwendigkeiten wissensintensiver Unternehmen : intellektuelles Kapital erkennen und Ansätze zu seiner Evaluierung

Der Produktionsfaktor Wissen gewinnt im Zuge der Entwicklung hin zu einer Hochtechnologie- und Wissensgesellschaft mehr und mehr an Bedeutung. Die Aufmerksamkeit gilt immer mehr dem Intellektuellen Kapital, welches in seinem Anteil am Unternehmensgesamtwert kontinuierlich steigt und mittlerweile sogar bis zu 90 Prozent des "wahren" Wertes eines Unternehmens abbilden kann. Es stellt einen zentralen Faktor der Wirtschaft dar und genieÃt mittlerweile sogar einen hÃheren Stellenwert als materielle und finanzielle Mittel. Umso erstaunlicher ist es, dass bisher noch keine allgemein anerkannten Methoden zur Messung von Intellektuellen Kapital existieren. Aktuelle Studien zeigen, dass in den meisten Organisationen ein GroÃteil des Intellektuellen Kapitals im Moment weder systematisch erfasst, geschweige denn systematisch gesteuert und entwickelt wird. Auch das traditionelle Rechnungswesen bildet immaterielles VermÃgen und somit die wirtschaftliche Lage des Unternehmens nur sehr mangelhaft ab. Die monetÃ$re Bewertung des Unternehmens und des Intellektuellen Kapitals erfordert im Wesentlichen eine Zukunftsorientierung. Die Bewertung erfolgt auf der Prognose von ZukunftsertrÃ$gen, welche aber in vielen FÃ$llen nur schwer vorhergesagt werden kÃnnen und dadurch Bewertungsunsicherheiten erzeugen. Die klassische Unternehmensbewertung muss deshalb zur umfassenden Unternehmensanalyse ausgebaut werden. Es mÃssen neue Instrumente neben traditionelle Systeme treten, um Managern und Investoren fÃr ihre Entscheidungen die relevanten zusÃ$tzlichen Informationen Ãber die immateriellen Faktoren zu liefern. Nur die ganzheitliche Betrachtungsweise unter entsprechender Beachtung von sowohl quantitativen als auch qualitativen Faktoren kann fÃr eine adÃ$quate Bewertung des Unternehmens und seines Intellektuellen Kapitals zielfÃhrend sein. Diese Arbeit analysiert zu Beginn das nationale und internationale Bilanzierungssystem, untersucht in weitere Folge verschiedene Bewertungsmethoden auf deren AbbildungsadÃ$quanz von Intellektuellem Kapital und vervollstÃ$ndigt durch die qualitative Komponente schlieÃlich die ganzheitliche Bewertungsperspektive.No abstract availableAlexander Paul LöhnerAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersKlagenfurt, Alpen-Adria-Univ., Diss., 2006KB2006 07OeBB(VLID)241220

Contribution of low-temperature single-molecule techniques to structural issues of pigment-protein complexes from photosynthetic purple bacteria

As the electronic energies of the chromophores in a pigment-protein complex are imposed by the geometrical structure of the protein, this allows the spectral information obtained to be compared with predictions derived from structural models. Thereby, the single-molecule approach is particularly suited for the elucidation of specific, distinctive spectral features that are key for a particular model structure, and that would not be observable in ensemble-averaged spectra due to the heterogeneity of the biological objects. In this concise review, we illustrate with the example of the light-harvesting complexes from photosynthetic purple bacteria how results from low-temperature single-molecule spectroscopy can be used to discriminate between different structural models. Thereby the low-temperature approach provides two advantages: (i) owing to the negligible photobleaching, very long observation times become possible, and more importantly, (ii) at cryogenic temperatures, vibrational degrees of freedom are frozen out, leading to sharper spectral features and in turn to better resolved spectra

The origin of the split B800 absorption peak in the LH2 complexes from Allochromatium vinosum

The absorption spectrum of the high-light peripheral light-harvesting (LH) complex from the photosynthetic purple bacterium Allochromatium vinosum features two strong absorptions around 800 and 850 nm. For the LH2 complexes from the species Rhodopseudomonas acidophila and Rhodospirillum molischianum, where high-resolution X-ray structures are available, similar bands have been observed and were assigned to two pigment pools of BChl a molecules that are arranged in two concentric rings (B800 and B850) with nine (acidophila) or eight (molischianum) repeat units, respectively. However, for the high-light peripheral LH complex from Alc. vinosum, the intruiging feature is that the B800 band is split into two components. We have studied this pigment–protein complex by ensemble CD spectroscopy and polarisation-resolved single-molecule spectroscopy. Assuming that the high-light peripheral LH complex in Alc. vinosum is constructed on the same modular principle as described for LH2 from Rps. acidophila and Rsp. molischianum, we used those repeat units as a starting point for simulating the spectra. We find the best agreement between simulation and experiment for a ring-like oligomer of 12 repeat units, where the mutual arrangement of the B800 and B850 rings resembles those from Rsp. molischianum. The splitting of the B800 band can be reproduced if both an excitonic coupling between dimers of B800 molecules and their interaction with the B850 manifold are taken into account. Such dimers predict an interesting apoprotein organisation as discussed below