Portabilitaet und Adaption von Software der linearen Algebra fuer Distributed Memory Systeme

Available from TIB Hannover: RR 5549(238)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Does the Reconstitution of RC-LH1 Complexes from <i>Rhodopseudomonas acidophila</i> Strain 10050 into a Phospholipid Bilayer Yield the Optimum Environment for Optical Spectroscopy?

We have investigated reaction-center light-harvesting 1 (RC-LH1) complexes from <i>Rhodopseudomonas (Rps.) acidophila</i> in detergent buffer solution and reconstituted into a phospholipid bilayer and compared the results with the outcome of an earlier study conducted on RC-LH1 immobilized in polyvinyl alcohol (PVA). The aim of this study was to test whether the immobilization of the complexes in a PVA matrix might lead to a deterioration of the proteins and thereby limit the accessible information that can be obtained from optical spectroscopy. It has been found that the complexes dissolved in a detergent buffer solution are subject to fast spectral dynamics preventing any meaningful application of single-molecule spectroscopy. In contrast, for the bilayer samples it is revealed that the reconstitution process results in a significantly larger fraction of broken complexes with respect to the preparation of the complexes in a PVA film. Moreover, we find that for the intact complexes the statistics of the key spectral features, such as the spectral separations of the bands and the mutual orientation of their transition-dipole moments, show no variation dependent on using either a bilayer or PVA as a matrix. Given the additional effort involved in the reconstitution process, the lower amount of intact RC-LH1 complexes and, concerning the decisive spectral details, the identical results with respect to embedding the complexes in a PVA matrix, we come to the conclusion that the immobilization of these proteins in a PVA matrix is a good choice for conducting low-temperature experiments on individual light-harvesting complexes

The Open, the Closed, and the Empty: Time-Resolved Fluorescence Spectroscopy and Computational Analysis of RC-LH1 Complexes from <i>Rhodopseudomonas palustris</i>

We studied the time-resolved fluorescence of isolated RC-LH1 complexes from <i>Rhodopseudomonas palustris</i> as a function of the photon fluence and the repetition rate of the excitation laser. Both parameters were varied systematically over 3 orders of magnitude. On the basis of a microstate description we developed a quantitative model for RC-LH1 and obtained very good agreement between experiments and elaborate simulations based on a global master equation approach. The model allows us to predict the relative population of RC-LH1 complexes with the special pair in the neutral state or in the oxidized state P⁺ and those complexes that lack a reaction center