Marcel Petri

Publications (3)11.52 Total impact

• Article: Structural characterization of nanoscale meshworks within a nucleoporin FG hydrogel.

  Marcel Petri, Steffen Frey, Andreas Menzel, Dirk Görlich, Simone Techert
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  ABSTRACT: The permeability barrier of nuclear pore complexes (NPCs) controls all exchange of macromolecules between the cytoplasm and the cell nucleus. It consists of phenylalanine-glycine (FG) repeat domains apparently organized as an FG hydrogel. It has previously been demonstrated that an FG hydrogel derived from the yeast nucleoporin Nsp1p reproduces the selectivity of authentic NPCs. Here we combined time-resolved optical spectroscopy and X-ray scattering techniques to characterize such a gel. The data suggest a hierarchy of structures that form during gelation at the expense of unstructured elements. On the largest scale, protein-rich domains with a correlation length of ~16.5 nm are evident. On a smaller length scale, aqueous channels with an average diameter of ~3 nm have been found, which possibly represent the physical structures accounting for the passive sieving effect of nuclear pores. The protein-rich domains contain characteristic β-structures with typical inter-β-strand and inter-β-sheet distances of 1.3 and 0.47 nm, respectively. During gelation, the formation of oligomeric associates is accompanied by the transfer of phenylalanines into a hydrophobic microenvironment, supporting the view that this process is driven by a hydrophobic collapse.
  Biomacromolecules 05/2012; 13(6):1882-9. · 5.48 Impact Factor
• Article: Concentration effects on the dynamics of liquid crystalline self-assembly: time-resolved X-ray scattering studies.

  Marcel Petri, Andreas Menzel, Oliver Bunk, Gerhard Busse, Simone Techert
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  ABSTRACT: A manifold of ordering transitions relevant to chemical and biological systems occur at interfaces from liquids to self-assembled soft solids like membranes or liquid crystals. In the present case, we were interested in understanding the phase transition from the microemulsion phase to the liquid crystal phase in terms of their driving forces, i.e., activation energy and entropy. The purpose of this work was to clarify the influence of concentration effects of the amphiphilic molecules on the nature of these self-assembly processes. By photosensitization of the model system (polyalkylglycolether (C(10)E(4)), water, decane, and cyclohexane) with laser dyes, we could effectively induce and control the phase transition through the absorption of optical photons. The photo transformation conditions were chosen in such a way that the system was in thermal equilibrium. By application of time-resolved photo small-angle X-ray scattering we could monitor the conversion process and demonstrate that the surfactant concentration has a direct impact on the activation energy, which is observable through the length of the induction time.
  The Journal of Physical Chemistry A 02/2011; 115(11):2176-83. · 2.95 Impact Factor
• Source

  Available from: Wilson Quevedo

  Article: On the mechanism of photoinduced phase transitions in ternary liquid crystal systems near thermal equilibrium.

  Wilson Quevedo, Marcel Petri, Gerhard Busse, Simone Techert
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  ABSTRACT: According to their phase diagram, polyalkyl glycol ether dissolved in ternary solutions (water, alcane, and cyclohexane) lead to the formation of either liquid crystal phases or microemulsion phases. By photosensitization of the ternary system with laser dyes and choosing the adequate concentration and temperature conditions of these lyotropic systems, it is possible to photoinduce the phase transitions from the microemulsion phase to the liquid crystal phase (and vice versa). The phototransformation conditions were chosen in such a way that the system is in thermal equilibrium during the entire phase transition. The method of photo small angle x-ray scattering has been applied to investigate the mechanism of photoinduced phase transition. Spectroscopically, the mechanism of photoinduced phase transition has been characterized by optical absorption and emission techniques.
  The Journal of chemical physics 08/2008; 129(2):024502. · 3.09 Impact Factor