Molekulare Organisation und Signaltransduktion an Kontaktstellen zwischen Membranen

Abstract

Oberflächen schaffen eine Umgebung, in der zahlreiche Kräfte zusammenwirken und dabei eine Vielzahl komplexer chemischer Prozesse auslösen. Dies gilt vor allem für Zellmembranen, deren Fluidität und Flexibilität eine Antwort auf chemische Wechselwirkungen an der Oberfläche ermöglichen, wie man sie bei anorganischen Materialien in dieser Form nicht findet. Die Bildung räumlicher Proteinmuster an Membranoberflächen im Bereich von Membrankontaktstellen liefert viele Beispiele für solche Phänomene und spielt darüber hinaus eine wichtige Rolle bei der interzellulären Signaltransduktion. Entsprechend interessieren sich sowohl Physikochemiker als auch Zellbiologen für Wechselwirkungen an Membranoberflächen. Aktuelle, fachübergreifende Untersuchungen zur Bildung von Proteinmustern in immunologischen Synapsen und zur Rekonstitution und Manipulation von Membranen unter Verwendung moderner bildgebender Verfahren werden in diesem Aufsatz vorgestellt.

Modulation of Substrate–Membrane Interactions by Linear Poly(2‐methyl‐2‐oxazoline) Spacers Revealed by X‐ray Reflectivity and Ellipsometry

“…However, the calculation of polymer chain volume failed under dry conditions. For example, the chain volume calculated from the thickness measured by ellipsometry at RH = 11.3 %, V exp/ell = 3652 3 , is much smaller than V Connolly . This discrepancy suggests that the polymer layer thickness is underestimated in our slab model.…”

“…In fact, if one assumes that approximately 80 % of layer c with a thickness of 11 is filled with polymers, the expected volume of 1461 3 agrees very well with the difference V Connolly ÀV exp/ell = 1488 3 . After the deposition of the distal monolayer, the polymer layer now under bulk water becomes thicker by a factor of 6 (d exp/ell = 176 ), which corresponds to V exp/ell = 29 216 3 . Here, the influence of the polymer immersed in layer c on the entire volume of polymer is merely 5 %, and the volume fraction of water, F water/ell = 82 % (5140/29216 % 0.18) is obtained.…”

“…To estimate the volume fraction of hydrating water, these volumes obtained by experiment were compared to the volume predicted by the calculation method proposed by Connolly. [50] Using a probe radius of 1.4 for water, the excluded volume of one dry PMOx60 chain can be calculated to be V Connolly = 5140 3 . Comparison with the experimental chain volume at RH = 85 % suggests that the volume increases by 6 % due to the uptake of water.…”

“…Ellipsometric results were evaluated using a self-written code for IGOR Pro (WaveMetrics, Portland, OR, USA) based on the Abels matrix formalism. [3,28] The fit quality was assessed by evaluating the function of merit [Eq. (1)]:…”

“…[1][2][3] More recently, polymer-supported membranes have drawn increasing attention as a more sophisticated model for membraneextracellular contacts that provide soft interlayers for immobilization of membrane proteins without the risk of denaturation. [4,5] Model systems proposed so far can mainly be classified into two categories: 1) supported membranes deposited on preformed polymer films (polymer-cushioned membranes); [6] and 2) supported membranes separated from solid substrates by linear polymer spacers (polymer-tethered membranes).…”