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Dortmund, Germany

Wieland D.C.F.,Helmholtz Center Geesthacht | Degen P.,Fakultat Chemie | Paulus M.,Fakultat Physik DELTA | Schroer M.A.,Fakultat Physik DELTA | And 3 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

Structural and mechanical properties of molecularly thick polysiloxane membranes were studied on different liquid subphases to investigate the impact of the subphase's pH value on the cross-linking process. The lateral structure of these films was studied in-situ by grazing incidence diffraction while torsions pendulum experiments reveal the response of the system to mechanical stress. The results show a hindered cross-linking on acidic subphases. At alkaline and neutral pH conditions the cross-linking process was not effected. The data revealed that the degree of polymerization can be tuned by regulating the subphase's pH value, which opens the opportunity to build complex polysiloxane membranes in a controlled manner. © 2014 Elsevier B.V. Source


Wieland D.C.F.,Helmholtz Center Geesthacht | Degen P.,Fakultat Chemie | Paulus M.,Fakultat Physik DELTA | Schroer M.A.,Fakultat Physik DELTA | And 10 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2013

The early stages of the formation of inorganic aggregates, composed of iron compounds at the solution-air interface, were investigated in situ. The properties of the solution-air interface were changed by using different Langmuir layers. In order to get insight into the evolution of the sample system in situ, the processes were studied by X-ray scattering and spectroscopy techniques. The formation of aggregates was detected under cationic as well as under anionic Langmuir layers. The observed compounds lack long range order which indicates the formation of amorphous structures. This is supported by extended X-ray absorption fine structure measurements showing only minor order in the formed aggregates. © 2013 Elsevier B.V. Source


Schroer M.A.,Fakultat Physik DELTA | Paulus M.,Fakultat Physik DELTA | Jeworrek C.,TU Dortmund | Krywka C.,University of Kiel | And 9 more authors.
Biophysical Journal | Year: 2010

A structural interpretation of the thermodynamic stability of proteins requires an understanding of the structural properties of the unfolded state. High-pressure small-angle x-ray scattering was used to measure the effects of temperature, pressure, denaturants, and stabilizing osmolytes on the radii of gyration of folded and unfolded state ensembles of staphylococcal nuclease. A set of variants with the internal Val-66 replaced with Ala, Tyr, or Arg was used to examine how changes in the volume and polarity of an internal microcavity affect the dimensions of the native state and the pressure sensitivity of the ensemble. The unfolded state ensembles achieved for these proteins with high pressure were more compact than those achieved at high temperature, and were all very sensitive to the presence of urea and glycerol. Substitutions at the hydrophobic core detectably altered the conformation of the protein, even in the folded state. The introduction of a charged residue, such as Arg, inside the hydrophobic interior of a protein could dramatically alter the structural properties, even those of the unfolded state. The data suggest that a charge at an internal position can interfere with the formation of transient hydrophobic clusters in the unfolded state, and ensure that the pressure-unfolded form of a protein occupies the maximum volume possible. Only at high temperatures does the radius of gyration of the unfolded state ensemble approach the value for a statistical random coil. © 2010 by the Biophysical Society. Source

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