Eucl3

In a first step, the S-layer protein SbpA was recrystallized on the previously cleaned gold sensor surface by pumping the SbpA solution in the flow cell.^{[38 (link)]} Then, the sensor was rinsed with MilliQ water and the car-boxyl groups on the SbpA lattice were activated with the EDC/S-NHS solution (MilliQ water). After 10 min, a suspension containing the vesicles composed of DMPE (presenting terminal amino groups), βDK and BdEO and/or POPC was passed onto the S-layer lattice. In order to produce a gravimetric gradient, the cell was when rinsed with 200 mM glucose. For the fusion/ rupture of the vesicles, 1 mM EuCl₃ (Sigma-Aldrich) in MilliQ water or in 200 mM glucose solution (MilliQ water) was passed over the vesicular layer. The complex formation of one Eu³⁺-ion with two βDK groups located at adjacent vesicles comprising low polymer content caused in many cases the rupture and fusion of the bound vesicles.^{[38 (link)]} Vesicles comprising a high polymer content did nor open and fuse with each other and hence, the vesicular layer was incubated with 200 mM CaCl₂ solution (MilliQ water), citrate buffer (pH 4.0), and/or with a 0.2% solution of the detergent 3-[(3-cholamidopropyl) dimethyl-ammonio] -1-propane-sulfonate (CHAPS). If not other indicated, the presented data are the mean values of two independent measurements.

GdCl₃, TiCl₄, TeCl₄, EuCl₃, ErCl₃, YCl₃, YbCl₃, CeCl₄, MoCl₆, and TaCl₅ were obtained from Sigma-Aldrich. NaOH was obtained from Sinopharm Chemical Reagent Co. Deionized water used in all experiments was obtained from a Milli-Q water system.