Articles by Martha E. Brennich in JoVE
גודל הדרה מקוונת ו כרומטוגרפיה יון-חליפין על beamline SAXS Martha E. Brennich1, Adam R. Round2,3, Stephanie Hutin4 1Structural Biology Group, European Synchrotron Radiation Facility, 2European Molecular Biology Laboratory, 3School of Chemical and Physical Sciences, Keele University, 4Groupe de Microscopie Electronique et Méthodes, Institut de Biologie Structurale קביעת מבנה פתרון של חלבון על ידי פיזור קטן זווית קרני רנטגן (SAXS) דורש דגימות monodisperse. כאן, אנו מציגים שתי אפשרויות על מנת להבטיח עיכובים מינימאליים בין הכנת מדגם ורכישת נתונים: כרומטוגרפיה בגודל הדרה מקוון (SEC) כרומטוגרפיה היון-Exchange Online (IEC).
Other articles by Martha E. Brennich on PubMed
Impact of Ion Valency on the Assembly of Vimentin Studied by Quantitative Small Angle X-ray Scattering Soft Matter. Mar, 2014 | Pubmed ID: 24800271 The assembly kinetics of intermediate filament (IF) proteins from tetrameric complexes to single filaments and networks depends on the protein concentration, temperature and the ionic composition of their environment. We systematically investigate how changes in the concentration of monovalent potassium and divalent magnesium ions affect the internal organization of the resulting filaments. Small angle X-ray scattering (SAXS) is very sensitive to changes in the filament cross-section such as diameter or compactness. Our measurements reveal that filaments formed in the presence of magnesium chloride differ distinctly from filaments formed in the presence of potassium chloride. The principle multi-step assembly mechanism from tetramers via unit-length filaments (ULF) to elongated filaments is not changed by the valency of ions. However, the observed differences indicate that the magnesium ions free the head domains of tetramers from unproductive interactions to allow assembly but at the same time mediate strong inter-tetrameric interactions that impede longitudinal annealing of unit-length filaments considerably, thus slowing down filament growth.
ISPyB for BioSAXS, the Gateway to User Autonomy in Solution Scattering Experiments Acta Crystallographica. Section D, Biological Crystallography. Jan, 2015 | Pubmed ID: 25615862 Logging experiments with the laboratory-information management system ISPyB (Information System for Protein crystallography Beamlines) enhances the automation of small-angle X-ray scattering of biological macromolecules in solution (BioSAXS) experiments. The ISPyB interface provides immediate user-oriented online feedback and enables data cross-checking and downstream analysis. To optimize data quality and completeness, ISPyBB (ISPyB for BioSAXS) makes it simple for users to compare the results from new measurements with previous acquisitions from the same day or earlier experiments in order to maximize the ability to collect all data required in a single synchrotron visit. The graphical user interface (GUI) of ISPyBB has been designed to guide users in the preparation of an experiment. The input of sample information and the ability to outline the experimental aims in advance provides feedback on the number of measurements required, calculation of expected sample volumes and time needed to collect the data: all of this information aids the users to better prepare for their trip to the synchrotron. A prototype version of the ISPyBB database is now available at the European Synchrotron Radiation Facility (ESRF) beamline BM29 and is already greatly appreciated by academic users and industrial clients. It will soon be available at the PETRA III beamline P12 and the Diamond Light Source beamlines I22 and B21.
The Filament Forming Reactions of Vimentin Tetramers Studied in a Serial-inlet Microflow Device by Small Angle X-ray Scattering Biomicrofluidics. Mar, 2016 | Pubmed ID: 27042250 The structural organization of metazoan cells and their shape are established through the coordinated interaction of a composite network consisting of three individual filament systems, collectively termed the cytoskeleton. Specifically, microtubules and actin filaments, which assemble from monomeric globular proteins, provide polar structures that serve motor proteins as tracks. In contrast, intermediate filaments (IFs) assemble from highly charged, extended coiled coils in a hierarchical assembly mechanism of lateral and longitudinal interaction steps into non-polar structures. IF proteins are expressed in a distinctly tissue-specific way and thereby serve to generate the precise plasticity of the respective cells and tissues. Accordingly, in the cell, numerous parameters such as pH and salt concentration are adjusted such that the generation of functional networks is ensured. Here, we transfer the problem for the mesenchymal IF protein vimentin to an in vitro setting and combine small angle x-ray scattering with microfluidics and finite element method simulations. Our approach is adapted to resolve the early assembly steps, which take place in the sub-second to second range. In particular, we reveal the influence of ion species and concentrations on the assembly. By tuning the flow rates and thus concentration profiles, we find a minimal critical salt concentration for the initiation of the assembly. Furthermore, our analysis of the surface sensitive Porod regime in the x-ray data reveals that the formation of first assembly intermediates, so-called unit length filaments, is not a one-step reaction but consists of distinct consecutive lateral association steps followed by radial compaction as well as smoothening of the surface of the full-width filament.