Computational studies of biomembrane systems: Theoretical considerations, simulation models, and applications

This chapter summarizes several approaches combining theory, simulation and experiment that aim for a better understanding of phenomena in lipid bilayers and membrane protein systems, covering topics such as lipid rafts, membrane mediated interactions, attraction between transmembrane proteins, and aggregation in biomembranes leading to large superstructures such as the light harvesting complex of green plants. After a general overview of theoretical considerations and continuum theory of lipid membranes we introduce different options for simulations of biomembrane systems, addressing questions such as: What can be learned from generic models? When is it expedient to go beyond them? And what are the merits and challenges for systematic coarse graining and quasi-atomistic coarse grained models that ensure a certain chemical specificity

Anbau von Raps mit Kleeuntersaat im ökologischen Landbau

Im ökologischen Landbau ist der Anbau von Raps aufgrund des Schädlingsbefalls mit einem hohen Risiko behaftet (Petterson et. al. 2002; Haas u. Kramer, 1995). Weiterhin stellt Raps als stark stickstoff- (N) -zehrende Kultur hohe Ansprüche an die Vorfrucht und an die organische Düngung (Gruber, 2001; Mayer et. al., 2001; Loges u. Böhm, 2001). Er konkurriert aus diesem Grund im ökologischen Landbau mit Weizen um den Platz in der Fruchtfolge. Für die N-Versorgung der Nachfrucht erscheint es daher günstig, im Raps eine Kleeuntersaat zu etablieren. Es wurden verschiedene Verfahren des Rapsanbaus erprobt. Eine Weisskleeuntersaat zwischen den Reihen trug im ersten Versuchsjahr weder meßbar zu einer Verbesserung der N-Versorgung von Winterraps bei, noch konnte nachgewiesen werden, dass sie durch die Kleeuntersaat verschlechtert wurde. Der Versuch zeigte, dass Kleeuntersaat in Winterraps während der Vegetationsperiode N im Bodenprofil halten kann. Lagernder Raps war bei einer Weisskleeuntersaat nur mit großen Ernteverlusten zu beernten. Jedoch blieb eine bereits gut etablierte Leguminosenvorfrucht für den Anbau von Winterweizen zurück. Der Versuch wird als Exaktversuch mit verschiedenen Reihenabständen fortgesetzt

Multiband Superconductivity in KFe2As2: Evidence for one Isotropic and several Liliputian Energy Gaps

We report a detailed low-temperature thermodynamic investigation (heat capacity and magnetization) of the superconducting state of KFe2As2 for H || c axis. Our measurements reveal that the properties of KFe2As2 are dominated by a relatively large nodeless energy gap (Delta?0 = 1.9 kBTc) which excludes dx2-y2 symmetry. We prove the existence of several additional extremely small gaps (?Delta0 < 1.0 kBTc) that have a profound impact on the low-temperature and low-field behavior, similar to MgB2, CeCoIn5 and PrOs4Sb12. The zero-field heat capacity is analyzed in a realistic self-consistent 4-band BCS model which qualitatively reproduces the recent laser ARPES results of Okazaki et al. (Science 337 (2012) 1314). Our results show that extremely low-temperature measurements, i.e. T < 0.1 K, will be required in order to resolve the question of the existence of line nodes in this compound.Comment: 7 pages, 6 figure

David Chyträus als Historiker : Ein Beitrag zur Kenntnis der deutschen Historigraphie in Reformationsjahrhundert : [Diss.]

http://www.ester.ee/record=b4008284*es

Derivation of coarse-grained simulation models of chlorophyll molecules in lipid bilayers for applications in light harvesting systems

The correct interplay of interactions between protein, pigment and lipid molecules is highly relevant for our understanding of the association behavior of the light harvesting complex (LHCII) of green plants. To cover the relevant time and length scales in this multicomponent system, a multi-scale simulation ansatz is employed that subsequently uses a classical all atomistic (AA) model to derive a suitable coarse grained (CG) model which can be backmapped into the AA resolution, aiming for a seamless conversion between two scales. Such an approach requires a faithful description of not only the protein and lipid components, but also the interaction functions for the indispensable pigment molecules, chlorophyll b and chlorophyll a (referred to as chl b/chl a). In this paper we develop a CG model for chl b and chl a in a dipalmitoylphosphatidyl choline (DPPC) bilayer system. The structural properties and the distribution behavior of chl within the lipid bilayer in the CG simulations are consistent with those of AA reference simulations. The non-bonded potentials are parameterized such that they fit to the thermodynamics based MARTINI force-field for the lipid bilayer and the protein. The CG simulation shows chl aggregation in the lipid bilayer which is supported by fluorescence quenching experiments. It is shown that the derived chl model is well suited for CG simulations of stable, structurally consistent, trimeric LHCII and can in the future be used to study their large scale aggregation behavior.publishe

Characterisation of Listeria monocytogenes Isolates from Hunted Game and Game Meat from Finland

Listeria monocytogenes is an important foodborne zoonotic bacterium. It is a heterogeneous species that can be classified into lineages, serogroups, clonal complexes, and sequence types. Only scarce information exists on the properties of L. monocytogenes from game and game meat. We characterised 75 L. monocytogenes isolates from various game sources found in Finland between 2012 and 2020. The genetic diversity, presence of virulence and antimicrobial genes were studied with whole genome sequencing. Most (89%) of the isolates belonged to phylogenetic lineage (Lin) II and serogroup (SG) IIa. SGs IVb (8%) and IIb (3%) of Lin I were sporadically identified. In total, 18 clonal complexes and 21 sequence types (STs) were obtained. The most frequent STs were ST451 (21%), ST585 (12%) and ST37 (11%) found in different sample types between 2012 and 2020. We observed 10 clusters, formed by closely related isolates with 0–10 allelic differences. Most (79%) of the virulence genes were found in all of the L. monocytogenes isolates. Only fosX and lin were found out of 46 antimicrobial resistance genes. Our results demonstrate that potentially virulent and antimicrobial-sensitive L. monocytogenes isolates associated with human listeriosis are commonly found in hunted game and game meat in Finland