TY  - JOUR
A1  - Heddergott, Niko
A1  - Krüger, Timothy
A1  - Babu, Sujin B.
A1  - Wei, Ai
A1  - Stellamanns, Erik
A1  - Uppaluri, Sravanti
A1  - Pfohl, Thomas
A1  - Stark, Holger
A1  - Engstler, Markus
T1  - Trypanosome Motion Represents an Adaptation to the Crowded Environment of the Vertebrate Bloodstream
JF  - PLoS Pathogens
N2  - Blood is a remarkable habitat: it is highly viscous, contains a dense packaging of cells and perpetually flows at velocities varying over three orders of magnitude. Only few pathogens endure the harsh physical conditions within the vertebrate bloodstream and prosper despite being constantly attacked by host antibodies. African trypanosomes are strictly extracellular blood parasites, which evade the immune response through a system of antigenic variation and incessant motility. How the flagellates actually swim in blood remains to be elucidated. Here, we show that the mode and dynamics of trypanosome locomotion are a trait of life within a crowded environment. Using high-speed fluorescence microscopy and ordered micro-pillar arrays we show that the parasites mode of motility is adapted to the density of cells in blood. Trypanosomes are pulled forward by the planar beat of the single flagellum. Hydrodynamic flow across the asymmetrically shaped cell body translates into its rotational movement. Importantly, the presence of particles with the shape, size and spacing of blood cells is required and sufficient for trypanosomes to reach maximum forward velocity. If the density of obstacles, however, is further increased to resemble collagen networks or tissue spaces, the parasites reverse their flagellar beat and consequently swim backwards, in this way avoiding getting trapped. In the absence of obstacles, this flagellar beat reversal occurs randomly resulting in irregular waveforms and apparent cell tumbling. Thus, the swimming behavior of trypanosomes is a surprising example of micro-adaptation to life at low Reynolds numbers. For a precise physical interpretation, we compare our high-resolution microscopic data to results from a simulation technique that combines the method of multi-particle collision dynamics with a triangulated surface model. The simulation produces a rotating cell body and a helical swimming path, providing a functioning simulation method for a microorganism with a complex swimming strategy.
KW  - simulation
KW  - multiparticle collision dynamics
KW  - propulsion
KW  - viscosity
KW  - flagellar
KW  - motility
KW  - solvent
KW  - model
KW  - hydrodynamics
KW  - spiroplasma
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-134595
VL  - 8
IS  - 11
ER  - 
TY  - JOUR
A1  - Zaho, Huaying
A1  - Ghirlando, Rodolfo
A1  - Alfonso, Carlos
A1  - Arisaka, Fumio
A1  - Attali, Ilan
A1  - Bain, David L.
A1  - Bakhtina, Marina M.
A1  - Becker, Donald F.
A1  - Bedwell, Gregory J.
A1  - Bekdemir, Ahmet
A1  - Besong, Tabot M. D.
A1  - Birck, Catherine
A1  - Brautigam, Chad A.
A1  - Brennerman, William
A1  - Byron, Olwyn
A1  - Bzowska, Agnieszka
A1  - Chaires, Jonathan B.
A1  - Chaton, Catherine T.
A1  - Coelfen, Helmbut
A1  - Connaghan, Keith D.
A1  - Crowley, Kimberly A.
A1  - Curth, Ute
A1  - Daviter, Tina
A1  - Dean, William L.
A1  - Diez, Ana I.
A1  - Ebel, Christine
A1  - Eckert, Debra M.
A1  - Eisele, Leslie E.
A1  - Eisenstein, Edward
A1  - England, Patrick
A1  - Escalante, Carlos
A1  - Fagan, Jeffrey A.
A1  - Fairman, Robert
A1  - Finn, Ron M.
A1  - Fischle, Wolfgang
A1  - Garcia de la Torre, Jose
A1  - Gor, Jayesh
A1  - Gustafsson, Henning
A1  - Hall, Damien
A1  - Harding, Stephen E.
A1  - Hernandez Cifre, Jose G.
A1  - Herr, Andrew B.
A1  - Howell, Elizabeth E.
A1  - Isaac, Richard S.
A1  - Jao, Shu-Chuan
A1  - Jose, Davis
A1  - Kim, Soon-Jong
A1  - Kokona, Bashkim
A1  - Kornblatt, Jack A.
A1  - Kosek, Dalibor
A1  - Krayukhina, Elena
A1  - Krzizike, Daniel
A1  - Kusznir, Eric A.
A1  - Kwon, Hyewon
A1  - Larson, Adam
A1  - Laue, Thomas M.
A1  - Le Roy, Aline
A1  - Leech, Andrew P.
A1  - Lilie, Hauke
A1  - Luger, Karolin
A1  - Luque-Ortega, Juan R.
A1  - Ma, Jia
A1  - May, Carrie A.
A1  - Maynard, Ernest L.
A1  - Modrak-Wojcik, Anna
A1  - Mok, Yee-Foong
A1  - Mücke, Norbert
A1  - Nagel-Steger, Luitgard
A1  - Narlikar, Geeta J.
A1  - Noda, Masanori
A1  - Nourse, Amanda
A1  - Obsil, Thomas
A1  - Park, Chad K
A1  - Park, Jin-Ku
A1  - Pawelek, Peter D.
A1  - Perdue, Erby E.
A1  - Perkins, Stephen J.
A1  - Perugini, Matthew A.
A1  - Peterson, Craig L.
A1  - Peverelli, Martin G.
A1  - Piszczek, Grzegorz
A1  - Prag, Gali
A1  - Prevelige, Peter E.
A1  - Raynal, Bertrand D. E.
A1  - Rezabkova, Lenka
A1  - Richter, Klaus
A1  - Ringel, Alison E.
A1  - Rosenberg, Rose
A1  - Rowe, Arthur J.
A1  - Rufer, Arne C.
A1  - Scott, David J.
A1  - Seravalli, Javier G.
A1  - Solovyova, Alexandra S.
A1  - Song, Renjie
A1  - Staunton, David
A1  - Stoddard, Caitlin
A1  - Stott, Katherine
A1  - Strauss, Holder M.
A1  - Streicher, Werner W.
A1  - Sumida, John P.
A1  - Swygert, Sarah G.
A1  - Szczepanowski, Roman H.
A1  - Tessmer, Ingrid
A1  - Toth, Ronald T.
A1  - Tripathy, Ashutosh
A1  - Uchiyama, Susumu
A1  - Uebel, Stephan F. W.
A1  - Unzai, Satoru
A1  - Gruber, Anna Vitlin
A1  - von Hippel, Peter H.
A1  - Wandrey, Christine
A1  - Wang, Szu-Huan
A1  - Weitzel, Steven E
A1  - Wielgus-Kutrowska, Beata
A1  - Wolberger, Cynthia
A1  - Wolff, Martin
A1  - Wright, Edward
A1  - Wu, Yu-Sung
A1  - Wubben, Jacinta M.
A1  - Schuck, Peter
T1  - A Multilaboratory Comparison of Calibration Accuracy and the Performance of External References in Analytical Ultracentrifugation
JF  - PLoS ONE
N2  - Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets. These allowed for an assessment of many parameters of instrument performance, including accuracy of the reported scan time after the start of centrifugation, the accuracy of the temperature calibration, and the accuracy of the radial magnification. The range of sedimentation coefficients obtained for BSA monomer in different instruments and using different optical systems was from 3.655 S to 4.949 S, with a mean and standard deviation of (4.304\(\pm\)0.188) S (4.4%). After the combined application of correction factors derived from the external calibration references for elapsed time, scan velocity, temperature, and radial magnification, the range of s-values was reduced 7-fold with a mean of 4.325 S and a 6-fold reduced standard deviation of \(\pm\)0.030 S (0.7%). In addition, the large data set provided an opportunity to determine the instrument-to-instrument variation of the absolute radial positions reported in the scan files, the precision of photometric or refractometric signal magnitudes, and the precision of the calculated apparent molar mass of BSA monomer and the fraction of BSA dimers. These results highlight the necessity and effectiveness of independent calibration of basic AUC data dimensions for reliable quantitative studies.
KW  - fluorescence-detected sedimentation
KW  - size exclusion chromatography
KW  - field flow fractionation
KW  - spinco ultracentrifuge
KW  - aggregation
KW  - bead models
KW  - velocity
KW  - hydrodynamics
KW  - biopharmaceuticals
KW  - proteins
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-151903
VL  - 10
IS  - 5
ER  - 
TY  - JOUR
A1  - Bárcena-Uribarri, Iván
A1  - Thein, Marcus
A1  - Maier, Elke
A1  - Bonde, Mari
A1  - Bergström, Sven
A1  - Benz, Roland
T1  - Use of Nonelectrolytes Reveals the Channel Size and Oligomeric Constitution of the Borrelia burgdorferi P66 Porin
JF  - PLoS ONE
N2  - In the Lyme disease spirochete Borrelia burgdorferi, the outer membrane protein P66 is capable of pore formation with an atypical high single-channel conductance of 11 nS in 1 M KCl, which suggested that it could have a larger diameter than ‘normal’ Gram-negative bacterial porins. We studied the diameter of the P66 channel by analyzing its single-channel conductance in black lipid bilayers in the presence of different nonelectrolytes with known hydrodynamic radii. We calculated the filling of the channel with these nonelectrolytes and the results suggested that nonelectrolytes (NEs) with hydrodynamic radii of 0.34 nm or smaller pass through the pore, whereas neutral molecules with greater radii only partially filled the channel or were not able to enter it at all. The diameter of the entrance of the P66 channel was determined to be \(\leq\)1.9 nm and the channel has a central constriction of about 0.8 nm. The size of the channel appeared to be symmetrical as judged from one-sidedness of addition of NEs. Furthermore, the P66-induced membrane conductance could be blocked by 80–90% by the addition of the nonelectrolytes PEG 400, PEG 600 and maltohexaose to the aqueous phase in the low millimolar range. The analysis of the power density spectra of ion current through P66 after blockage with these NEs revealed no chemical reaction responsible for channel block. Interestingly, the blockage of the single-channel conductance of P66 by these NEs occurred in about eight subconductance states, indicating that the P66 channel could be an oligomer of about eight individual channels. The organization of P66 as a possible octamer was confirmed by Blue Native PAGE and immunoblot analysis, which both demonstrated that P66 forms a complex with a mass of approximately 460 kDa. Two dimension SDS PAGE revealed that P66 is the only polypeptide in the complex.
KW  - radii
KW  - hydrodynamics
KW  - SDS polyacrylamide gel electrophoresis
KW  - molecular mass
KW  - outer membrane proteins
KW  - single channel recording
KW  - blue native polyacrylamide gel electrophoresis
KW  - borrelia burgdorferi
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-129965
VL  - 8
IS  - 11
ER  - 
TY  - THES
A1  - Hupp, Markus
T1  - Simulating Star Formation and Turbulence in Models of Isolated Disk Galaxies
T1  - Simulation von Sternentstehung und Turbulenz in Modellen von isolierten Scheibengalaxien
N2  - We model Milky Way like isolated disk galaxies in high resolution three-dimensional hydrodynamical simulations with the adaptive mesh refinement code Enzo. The model galaxies include a dark matter halo and a disk of gas and stars. We use a simple implementation of sink particles to measure and follow collapsing gas, and simulate star formation as well as stellar feedback in some cases. We investigate two largely different realizations of star formation. Firstly, we follow the classical approach to transform cold, dense gas into stars with an fixed efficiency. These kind of simulations are known to suffer from an overestimation of star formation and we observe this behavior as well. Secondly, we use our newly developed FEARLESS approach to combine hydrodynamical simulations with a semi-analytic modeling of unresolved turbulence and use this technique to dynamically determine the star formation rate. The subgrid-scale turbulence regulated star formation simulations point towards largely smaller star formation efficiencies and henceforth more realistic overall star formation rates. More work is necessary to extend this method to account for the observed highly supersonic turbulence in molecular clouds and ultimately use the turbulence regulated algorithm to simulate observed star formation relations.
N2  - In dieser Arbeit beschäftigen wir uns mit der Modellierung und Durchführung von hoch aufgelösten dreidimensionalen Simulationen von isolierten Scheibengalaxien, vergleichbar unserer Milchstraße. Wir verwenden dazu den Simulations-Code Enzo, der die Methode der adaptiven Gitterverfeinerung benutzt um die örtliche und zeitliche Auflösung der Simulationen anzupassen. Unsere Galaxienmodelle beinhalten einen Dunkle Materie Halo sowie eine galaktische Scheibe aus Gas und Sternen. Regionen besonders hoher Gasdichte werden durch Teilchen ersetzt, die fortan die Eigenschaften des Gases beziehungsweise der darin entstehenden Sterne beschreiben. Wir untersuchen zwei grundlegend verschiedene Darstellungen von Sternentstehung. Die erste Methode beschreibt die Umwandlung dichten Gases einer Molekülwolke in Sterne mit konstanter Effektivität und führt wie in früheren Simulationen zu einer Überschätzung der Sternentstehungsrate. Die zweite Methode nutzt das von unserer Gruppe neu entwickelte FEARLESS Konzept, um hydrodynamische Simulationen mit analytischen-empirischen Modellen zu verbinden und bessere Aussagen über die in einer Simulation nicht explizit aufgelösten Bereiche treffen zu können. Besonderes Augenmerk gilt in dieser Arbeit dabei der in Molekülwolken beobachteten Turbulenz. Durch die Einbeziehung dieser nicht aufgelösten Effekte sind wir in der Lage eine realistischere Aussage über die Sternentstehungsrate zu treffen. Eine zukünftige Weiterentwicklung dieser von uns entwickelten und umgesetzten Technik kann in Zukunft dafür verwendet werden, die Qualität des durch Turbulenz regulierten Sternentstehungsmodells noch weiter zu steigern.
KW  - Astrophysik
KW  - Hydrodynamik
KW  - Turbulenz
KW  - Sternentstehung
KW  - Computersimulation
KW  - Interstellare Materie
KW  - Subgrid-Skalen Modell
KW  - Galaxienentstehung
KW  - Galaxienentwicklung
KW  - astrophysics
KW  - hydrodynamics
KW  - turbulence
KW  - star formation
KW  - subgrid-scale model
Y1  - 2008
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-34510
ER  -