Results (
Thai) 2:
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Giant protoplasts of Saccharomyces cerevisiae of 10–35 µm in diameter were generated by multi-cell electrofusion.
Thereby two different preparation strategies were evaluated with a focus on size distribution and “patchability”
of electrofused protoplasts. In general, parental protoplasts were suitable for electrofusion 1–12 h after isolation.
The electrophysiological properties of electrofused giant protoplasts could be analyzed by the whole-cell patch
clamp technique. The area-specific membrane capacitance (0.66±0.07 µF/cm2
) and conductance (23–44 µS/cm2
)
of giant protoplasts were consistent with the corresponding data for parental protoplasts. Measurements with
fluorescein-filled patch pipettes allowed to exclude any internal compartmentalisation of giant protoplasts by
plasma membranes, since uniform (diffusion-controlled) dye uptake was only observed in the whole-cell
configuration, but not in the cell-attached formation. The homogeneous structure of giant protoplasts was further
confirmed by the observation that no plasma membrane associated fluorescence was seen in the interior of giant
cells after electrofusion of protoplasts expressing the light-activated cation channel Channelrhodopsin-2 (ChR2)
linked to yellow fluorescent protein (YFP). Patch clamp analysis of the heterologously expressed ChR2-YFP
showed typical blue light dependent, inwardly-directed currents for both electrofused giant and parental
protoplasts. Most importantly, neither channel characteristics nor channel expression density was altered by
electric field treatment. Summarising, multi-cell electrofusion increases considerably the absolute number of
membrane proteins accessible in patch clamp experiments, thus presumably providing a convenient tool for the
biophysical investigation of low-signal transporters and channels
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