% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Hemonnot:315821,
      author       = {Hemonnot, Clement},
      othercontributors = {Koester, Sarah},
      title        = {{I}nvestigating {C}ellular {N}anoscale with {X}-{R}ays :
                      {F}rom {P}roteins to {N}etworks},
      school       = {University of Göttingen},
      type         = {Dr.},
      reportid     = {PUBDB-2016-06090},
      pages        = {184},
      year         = {2016},
      note         = {University of Göttingen, Diss., 2016},
      abstract     = {The advances and technical improvements of X-ray imaging
                      techniques, taking advantage of X-ray focussing optics and
                      high intensity synchrotron sources, nowadays allow for the
                      use of X-rays to probe the cellular nanoscale. Importantly,
                      X-rays permit thick samples to be imaged without sectioning
                      or slicing. In this work, two macromolecules, namely keratin
                      intermediate filament (IF) proteins and DNA, both essential
                      components of cells, were studied by X-ray techniques.
                      Keratin IF proteins make up an integral part of the
                      cytoskeleton of epithelial cells and form a dense
                      intracellular network of bundles. This network is built from
                      monomers in a hierarchical fashion. Thus, the keratin
                      structure formation spans a large range of length scales
                      from a few nanometres (monomers) to micrometres (networks).
                      Here, keratin was studied at three different scales: i)
                      filaments, ii) bundles and iii) networks. Solution
                      small-angle X-ray scattering revealed distinct structural
                      and organisational characteristics of these highly charged
                      polyelectrolyte filaments, such as increasing radius with
                      increasing salt concentration and spatial accumulation of
                      ions depending on the salt concentration. The results are
                      quantified by employing advanced modelling of keratin IFs by
                      a core cylinder flanked with Gaussian chains. Scanning
                      micro-diffraction was used to study keratin at the bundle
                      scale. Very different morphologies of keratin bundles were
                      observed at different salt conditions. At the network scale,
                      new imaging approaches and analyses were applied to the
                      study of whole cells. Ptychography and scanning X-ray
                      nano-diffraction imaging were performed on the same cells,
                      allowing for high resolution in real and reciprocal space,
                      thereby revealing the internal structure of these networks.
                      By using a fitting routine based on simulations of IFs
                      packed on a hexagonal lattice, the radius of each filament
                      and distance between filaments were retrieved.In mammalian
                      cells, each nucleus contains 2 nm-thick DNA double helices
                      with a total length of about 2 m. The DNA strands are packed
                      in a highly hierarchical manner into individual chromosomes.
                      DNA was studied in intact cells by visible light microscopy
                      and scanning X-ray nano-diffraction, unveiling the
                      compaction und decompaction of DNA during the cell cycle.
                      Thus, we obtained information on the aggregation state of
                      the nuclear DNA at a real space resolution on the order of
                      few hundreds nm. To exploit to the reciprocal space
                      information, individual diffraction patterns were analysed
                      according to a generalised Porod’s law at a resolution
                      down to 10 nm. We were able to distinguish nucleoli,
                      heterochromatin and euchromatin in the nuclei and follow the
                      compaction and decompaction during the cell division cycle.},
      cin          = {DOOR},
      cid          = {I:(DE-H253)HAS-User-20120731},
      pnm          = {6G3 - PETRA III (POF3-622) / VH-VI-403 - In-Situ
                      Nano-Imaging of Biological and Chemical Processes
                      $(2015_IFV-VH-VI-403)$ / FS-Proposal: I-20130035
                      (I-20130035) / FS-Proposal: I-20140150 (I-20140150)},
      pid          = {G:(DE-HGF)POF3-6G3 / $G:(DE-HGF)2015_IFV-VH-VI-403$ /
                      G:(DE-H253)I-20130035 / G:(DE-H253)I-20140150},
      experiment   = {EXP:(DE-H253)P-P10-20150101},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2016-06090},
      url          = {https://bib-pubdb1.desy.de/record/315821},
}