Pasteur pipette

The microphone-pipettes or pipettes Pasteur are fine tubes of glass whose end was frayed to obtain an open point of a diameter ad hoc .

Use

In electrophysiology, the microphone-pipettes are filled with saline solution in which a chlorinated money electrode connected to an amplifier is inserted. The point of the microélectrode thus prepared is applied against the cellular membrane to measure the electric activity of it. After establishment of a joint between the membrane and the microphone-pipette, a strong suction (sometimes accompanied by a light electric shock) makes it possible to break the membrane under the microphone-pipette and to return in conformation " cell entière" (see Patch-clamp).
One uses also microphone-pipettes within the framework of the cellular Biologie for example transfecter a cell with a foreign DNA by electrophoresis.

Obtaining

The microphone-pipettes are obtained starting from a capillary of glass (approximately 0,5 mms diameter) whose center is heated by a drawing at the same time as the two ends are drawn. Glass frays until rupture and one obtains two microphone-pipettes whose approximately conical end has the desired diameter. One can obtain the diameter which one wishes by varying the programme of heating-stretching of the printer.

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