Köster, Sarah

[["dc.bibliographiccitation.firstpage","439"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","The European Physical Journal E - Soft Matter"],["dc.bibliographiccitation.lastpage","449"],["dc.bibliographiccitation.volume","25"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Kierfeld, Jan"],["dc.contributor.author","Pfohl, Thomas"],["dc.date.accessioned","2017-09-07T11:48:46Z"],["dc.date.available","2017-09-07T11:48:46Z"],["dc.date.issued","2008"],["dc.description.abstract","Confinement effects on single semiflexible macromolecules are of central importance for a fundamental understanding of cellular processes involving biomacromolecules. To analyze the influence of confinement on the fluctuations of semiflexible macromolecules we study individual actin filaments in straight and curved microchannels. We experimentally characterize the segment distributions for fluctuating semiflexible filaments in microchannels as a function of the channel width. Moreover, the effect of channel curvature on the filament fluctuations is investigated. We find quantitative agreement between experimental results, Monte Carlo simulations, and the analytical description. This allows for determination of the persistence length of actin filaments, the deflection length, which characterizes the confinement effects, and the scaling exponents for the segment distribution of semiflexible macromolecules."],["dc.identifier.doi","10.1140/epje/i2007-10312-3"],["dc.identifier.gro","3143323"],["dc.identifier.isi","000255867900010"],["dc.identifier.pmid","18425410"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/825"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","1292-8941"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","cytoskeleton"],["dc.subject.gro","cellular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","Characterization of single semiflexible filaments under geometric constraints"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","771"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Cell Motility and the Cytoskeleton"],["dc.bibliographiccitation.lastpage","776"],["dc.bibliographiccitation.volume","66"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Pfohl, Thomas"],["dc.date.accessioned","2017-09-07T11:46:50Z"],["dc.date.available","2017-09-07T11:46:50Z"],["dc.date.issued","2009"],["dc.description.abstract","The motility, shape, and functionality of the cell depend sensitively on cytoskeletal mechanics which in turn is governed by the properties of filamentous proteins mainly actin, microtubules, and intermediate filaments. These biopolymers are confined in the dense cytoplasm and therefore experience strong geometric constraints on their equilibrium thermal fluctuations. To obtain a better understanding of the influence of confinement on cytoskeletal filaments we study the thermal fluctuations of individual actin filaments in a microfluidic in vitro system by fluorescence microscopy and determine the persistence length of the filaments by analyzing the radial distribution function. A unique feature of this method is that we obtain the persistence length without detailed knowledge of the complete contour of the filament which makes the technique applicable to a broad range of biological polymers, including those with a persistence length smaller than the optical resolution."],["dc.identifier.doi","10.1002/cm.20336"],["dc.identifier.gro","3143045"],["dc.identifier.isi","000270500800002"],["dc.identifier.pmid","19137583"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/516"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0886-1544"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","cytoskeleton"],["dc.subject.gro","cellular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","An In Vitro Model System for Cytoskeletal Confinement"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2167"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","Biomacromolecules"],["dc.bibliographiccitation.lastpage","2172"],["dc.bibliographiccitation.volume","8"],["dc.contributor.author","Pfohl, Thomas"],["dc.contributor.author","Otten, Alexander"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Dootz, Rolf"],["dc.contributor.author","Struth, Bernd"],["dc.contributor.author","Evans, Heather M."],["dc.date.accessioned","2017-09-07T11:49:28Z"],["dc.date.available","2017-09-07T11:49:28Z"],["dc.date.issued","2007"],["dc.description.abstract","DNA condensation in vivo usually requires proteins and/or multivalent salts. Here, we explore the in vitro compaction of DNA by cationic dendrimers having an intermediate size and charge. The dynamic assembly of DNA-dendrimer mesophases is discernible due to the laminar flow in a specially designed X-ray compatible microfluidic device. The setup ensures a nonequilibrium ascent of reactant concentration, and the resulting progression of DNA compaction was detected online using microfocused small-angle X-ray diffraction. The evolution of a DNA-dendrimer columnar square mesophase as a function of increasing dendrimer content is described. Additionally, in regions of maximum shear, an unexpected high-level perpendicular ordering of this phase is recorded. Furthermore, these assemblies are found to be in coexistence with a densely packed DNA-only mesophase in regions of excess DNA. The latter is reminiscent of dense packing found in bacteriophage and chromosomes, although surprisingly, it is not stabilized by direct dendrimer contact."],["dc.identifier.doi","10.1021/bm070317s"],["dc.identifier.gro","3143474"],["dc.identifier.isi","000247820000019"],["dc.identifier.pmid","17579478"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/992"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","1525-7797"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","x-ray scattering"],["dc.subject.gro","molecular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","Highly packed and oriented DNA mesophases identified using in situ microfluidic X-ray microdiffraction"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","96"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Small"],["dc.bibliographiccitation.lastpage","100"],["dc.bibliographiccitation.volume","3"],["dc.contributor.author","Dootz, Rolf"],["dc.contributor.author","Evans, Heather M."],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Pfohl, Thomas"],["dc.date.accessioned","2017-09-07T11:49:53Z"],["dc.date.available","2017-09-07T11:49:53Z"],["dc.date.issued","2007"],["dc.description.abstract","Microfluidics meets microdiffraction: A straightforward and inexpensive method of fabricating long‐lifetime, X‐ray‐microdiffraction compatible, ultrathin microfluidic devices with an overwhelming versatility with respect to channel design elements is presented (see image). To illustrate the analytic power and geometric flexibility of these microflow foils, X‐ray microdiffraction measurements on shear‐induced alignment effects in the smectic liquid crystal n‐octyl‐4‐cyanobiphenyl are shown."],["dc.identifier.doi","10.1002/smll.200600288"],["dc.identifier.gro","3143568"],["dc.identifier.isi","000243478200014"],["dc.identifier.pmid","17294477"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/1096"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","1613-6810"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","x-ray scattering"],["dc.subject.gro","microfluidics"],["dc.title","Rapid prototyping of X-ray microdiffraction compatible continuous microflow foils"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","745"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Journal of Synchrotron Radiation"],["dc.bibliographiccitation.lastpage","750"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Otten, Alexander"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Struth, Bernd"],["dc.contributor.author","Snigirev, Anatoly"],["dc.contributor.author","Pfohl, Thomas"],["dc.date.accessioned","2017-09-07T11:53:40Z"],["dc.date.available","2017-09-07T11:53:40Z"],["dc.date.issued","2005"],["dc.description.abstract","The combination of X- ray microdiffraction and microfluidics is used to investigate the dynamic behaviour of soft materials. A microfocused X- ray beam enables the observation of the influence of droplet formation on the nanostructure of a smectic liquid crystal in water. Using a hydrodynamic focusing device, the evolution of the intercalation of DNA into multilamellar membranes can be studied. Owing to the elongational flow at the centre of this device, alignment of the material is induced which allows for an improved structural characterization. Furthermore, the influence of strain applied to these materials can be tested."],["dc.identifier.doi","10.1107/S0909049505013580"],["dc.identifier.gro","3143792"],["dc.identifier.isi","000232619300009"],["dc.identifier.pmid","16239743"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/1344"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0909-0495"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","x-ray scattering"],["dc.subject.gro","molecular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","Microfluidics of soft matter investigated by small-angle X-ray scattering"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","541"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","ACS Macro Letters"],["dc.bibliographiccitation.lastpage","545"],["dc.bibliographiccitation.volume","1"],["dc.contributor.author","Steinhauser, Dagmar"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Pfohl, Thomas"],["dc.date.accessioned","2017-09-07T11:48:53Z"],["dc.date.available","2017-09-07T11:48:53Z"],["dc.date.issued","2012"],["dc.description.abstract","Many aspects of modern material science and biology rely on the strategic manipulation and understanding of polymer dynamics in confining micro- and nanoflow. We directly observe and analyze nonequilibrium structural and dynamic properties of individual semiflexible actin filaments in pressure-driven microfluidic channel flow using fluorescence microscopy. Different conformational shapes, such as filaments fluctuating in an elongated manner, parabolically bent, as well as tumbling, are identified. With increasing flow velocity, a strong center-of-mass migration toward the channel walls is observed. This significant migration effect can be explained by a shear rate dependent spatial diffusivity due to a gradient in chain mobility of the semiflexible polymers."],["dc.identifier.doi","10.1021/mz3000539"],["dc.identifier.gro","3142539"],["dc.identifier.isi","000303964900004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/8901"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","2161-1653"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","cytoskeleton"],["dc.subject.gro","cellular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","Mobility Gradient Induces Cross-Streamline Migration of Semiflexible Polymers"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1504"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Biomacromolecules"],["dc.bibliographiccitation.lastpage","1511"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Kinahan, Michelle E."],["dc.contributor.author","Filippidi, Emmanouela"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Hu, Xiao"],["dc.contributor.author","Evans, Heather M."],["dc.contributor.author","Pfohl, Thomas"],["dc.contributor.author","Kaplan, David L."],["dc.contributor.author","Wong, Joyce Y."],["dc.date.accessioned","2017-09-07T11:44:15Z"],["dc.date.available","2017-09-07T11:44:15Z"],["dc.date.issued","2011"],["dc.description.abstract","Despite widespread use of silk, it remains a significant challenge to fabricate fibers with properties similar to native silk. It has recently been recognized that the key to tuning silk fiber properties lies in controlling internal structure of assembled beta-sheets. We report an advance in the precise control of silk fiber formation with control of properties via microfluidic solution spinning. We use an experimental approach combined with modeling to accurately predict and independently tune fiber properties including Young's modulus and diameter to customize fibers. This is the first reported microfluidic approach capable of fabricating functional fibers with predictable properties and provides new insight into the structural transformations responsible for the unique properties of silk. Unlike bulk processes, our method facilitates the rapid and inexpensive fabrication of fibers from small volumes (50 mu L) that can be characterized to investigate sequence structure property relationships to optimize recombinant silk technology to match and exceed natural silk properties."],["dc.identifier.doi","10.1021/bm1014624"],["dc.identifier.gro","3142732"],["dc.identifier.isi","000290246400013"],["dc.identifier.pmid","21438624"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/168"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","1525-7797"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","molecular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","Tunable Silk. Using microfluidics to fabricate silk fibers with controllable properties"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1"],["dc.bibliographiccitation.lastpage","6"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Leach, Jennie B."],["dc.contributor.author","Pfohl, Thomas"],["dc.contributor.author","Wong, Joyce Y."],["dc.date.accessioned","2017-09-07T11:53:15Z"],["dc.date.available","2017-09-07T11:53:15Z"],["dc.date.issued","2011"],["dc.description.abstract","The hierarchical structure of type I collagen fibrils is a key contributor to the mechanical properties of the extracellular matrix (ECM). It is known that the process of in vitro fibrillogenesis strongly depends on the pH of the collagen solution. To date, there are few methods available for precisely controlling and investigating the dependence of collagen fibril assembly on the local pH. The objective of this work was to create highly defined pH gradients to systematically determine the effects of local pH on microscale collagen fibrillogenesis and alignment. We use a microfluidic mixing device to create a diffusion controlled pH gradient, which in turn initiates the self-assembly and concurrent flow-alignment of soluble collagen. Finite element method simulations of the hydrodynamic and diffusive phenomena are used to calculate the local concentrations of the components involved in the reaction. We develop a model to analytically calculate the local pH in the microfluidic device from these concentrations. A comparison with the experimental results from polarized light microscopy are in good agreement with the simulations."],["dc.identifier.doi","10.1557/proc-0898-l05-21"],["dc.identifier.gro","3145051"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/2744"],["dc.language.iso","en"],["dc.notes.intern","Crossref Import"],["dc.notes.status","final"],["dc.publisher","Materials Research Society"],["dc.publisher.place","Warrendale, Pa."],["dc.relation.eventend","2005-12-02"],["dc.relation.eventlocation","Boston, Massachusetts"],["dc.relation.eventstart","2005-11-28"],["dc.relation.isbn","1-55899-853-5"],["dc.relation.ispartof","Mechanical behavior of biological and biomimetic materials"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","molecular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","Microaligned collagen matrices by hydrodynamic focusing"],["dc.title.subtitle","Controlling the pH-induced self-assembly"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","199"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Biomacromolecules"],["dc.bibliographiccitation.lastpage","207"],["dc.bibliographiccitation.volume","9"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Evans, Heather M."],["dc.contributor.author","Wong, Joyce Y."],["dc.contributor.author","Pfohl, Thomas"],["dc.date.accessioned","2017-09-07T11:48:48Z"],["dc.date.available","2017-09-07T11:48:48Z"],["dc.date.issued","2008"],["dc.description.abstract","We present in situ studies on the self-assembly and,dynamic evolution of collagen gels from semidilute solutions in a microfluidic device. Collagen fibrils not only reinforce the mechanical properties of bone and tissues, but they also influence cellular motility and morphology. We access the initial steps of the hierarchical self-assembly of collagen fibrils and networks by using hydrodynamic focusing to form oriented fibers. The accurate description of the conditions within the microchannel requires a numerical expression for the pH in the device as well as a modified mathematical description of the viscosity, which increases nearly 300-fold as collagen fibrils form around neutral pH. Finite element modeling profiles overlay impressively with cross-polarized microscopy images of the birefringent fibrils in the channel. Real-time X-ray microdiffraction measurements in flow indicate an enhanced supramolecular packing having a unit spacing commensurate with that of a pentameric collagen subunit. These results have significant implications for the field of biomedicine, wherein new aligned, cellularly active, and mechanically strengthened materials continue to be in demand. However, this work is also-remarkable from a more fundamental, biophysical point of view because the underlying concepts may be generalized to a large pool of systems."],["dc.identifier.doi","10.1021/bm700973t"],["dc.identifier.gro","3143368"],["dc.identifier.isi","000252415600028"],["dc.identifier.pmid","18078321"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/874"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10 / Funder: NHLBI NIH HHS [R01 HL072900, R01 HL072900-03]"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","1525-7797"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","molecular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","An in situ study of collagen self-assembly processes"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","217"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Bulletin of the Polish Academy of Sciences. Technical sciences"],["dc.bibliographiccitation.lastpage","227"],["dc.bibliographiccitation.volume","55"],["dc.contributor.author","Evans, H. M."],["dc.contributor.author","Dootz, Rolf"],["dc.contributor.author","Köster, Sarah"],["dc.contributor.author","Struth, Bernd"],["dc.contributor.author","Pfohl, Thomas"],["dc.date.accessioned","2017-09-07T11:49:28Z"],["dc.date.available","2017-09-07T11:49:28Z"],["dc.date.issued","2007"],["dc.description.abstract","The study of liquid crystalline assemblies, with an emphasis on biological phenomena, is now accessible using newly developed microdevices integrated with X-ray analysis capability. Many biological systems can be described in terms of gradients, mixing, and confinement, all of which can be mimicked with the use of appropriate microfluidic designs. The use of hydrodynamic focusing creates well-defined mixing conditions that vary depending on parameters such as device geometry, and can be quantified with finite element modelling. We describe experiments in which geometry and strain rate induce finite changes in liquid crystalline orientation. We also demonstrate the online supramolecular assembly of lipoplexes. The measurement of lipoplex orientation as a function of flow velocity allows us to record a relaxation process of the lipoplexes, as evidenced by a remarkable 4-fold azimuthal symmetry. All of these processes are accessible due to the intentional integration of design elements in the microdevices."],["dc.identifier.gro","3143487"],["dc.identifier.isi","000255242300011"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/1006"],["dc.language.iso","en"],["dc.notes.intern","WoS Import 2017-03-10"],["dc.notes.status","final"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","0239-7528"],["dc.relation.orgunit","Institut für Röntgenphysik"],["dc.relation.workinggroup","RG Köster (Cellular Biophysics)"],["dc.subject.gro","x-ray scattering"],["dc.subject.gro","molecular biophysics"],["dc.subject.gro","microfluidics"],["dc.title","X-ray microdiffraction on flow-controlled biomolecular assemblies"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]