There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
Quartz has a dissipation factor of approximately 10(-4), which is an order of magnitude
less than that of the best glasses previously used to fabricate patch pipettes; it's
dielectric constant of 3.8 is also lower than that of other glasses. On the basis
of these electrical characteristics it is expected that patch pipettes pulled from
quartz tubing will produce significantly less noise than pipettes made from other
glasses. Our work confirms these expectations and we describe theoretical and practical
aspects of the use of quartz pipettes for single channel patch voltage clamp measurements.
Methods for pulling quartz pipettes with a laser-based puller and coating them with
low-loss elastomers are discussed, as are precautions that are necessary to achieve
low noise recordings. We have shown that quartz pipettes can be pulled from tubing
with outer diameter to inner diameter ratios as large as 3 and a method of applying
heavy elastomer coatings all the way to the tip of pipettes is presented. Noise sources
arising from the pipette and its holder are described theoretically, and it is shown
that measured noise is in good agreement with such predictions. With low noise capacitive
feedback electronics, small geometry holders, and thick-walled quartz pipettes coated
with low-loss elastomers we have been routinely able to achieve noise of 100 fA rms
or less in a 5-kHz bandwidth with real cell patches and a pipette immersion depth
of approximately 2 mm. On occasion we have achieved noise as low as 60 fA rms in this
bandwidth.