Complementation of physiological and behavioral defects by a slowpoke Ca(2+) -activated K(+) channel transgene.

The Drosophila slowpoke gene encodes a large conductance calcium-activated potassium channel used in neurons, muscle, and some epithelial cells. Tissue-specific transcriptional promoters and alternative mRNA splicing generate a large array of transcripts. These distinct transcripts are thought to tailor the properties of the channel to the requirements of the cell. Presumably, a single splice variant cannot satisfy the specific needs of all cell types. To test this, we examined whether a single slowpoke splice variant was capable of complementing all slowpoke behavioral phenotypes. Null mutations in slowpoke cause animals to be semiflightless and to manifest an inducible "sticky-feet" phenotype. The well-characterized slowpoke transcriptional control region was used to direct the expression of a single slowpoke splice variant (cDNA H13) in transgenic flies. The endogenous gene in these flies had been inactivated by the slo(4) mutation. Action-potential recordings and voltage-clamp recordings demonstrated the production of functional channels from the transgene. The transgene completely complemented the flight defect, but not the sticky-feet phenotype. We conclude that distinct slowpoke channel isoforms, produced by alternative splicing, are not interchangeable and are required for proper function of different cell types.

Behavioral and electrophysiological analysis of Ca-activated K-channel transgenes in Drosophila.

The slowpoke gene of Drosophila melanogaster encodes a Ca-activated K channel. This gene is expressed in neurons, muscles, tracheal cells, and the copper and iron cells of the midgut. The gene produces a large number of alternative products using tissue-specific transcriptional promoters and alternative mRNA splicing. We have described in great depth how transcription is regulated and are now cataloging the tissue-specificity of different splice variants. It is believed that the diversity of products serves to tailor channel attributes to the needs of specific tissues. Electrophysiological and behavioral assays indicate that at least some of these products produce channels with distinct properties.

Microlithography by using neutral metastable atoms and self-assembled monolayers.

Lithography can be performed with beams of neutral atoms in metastable excited states to pattern self-assembled monolayers (SAMs) of alkanethiolates on gold. An estimated exposure of a SAM of dodecanethiolate (DDT) to 15 to 20 metastable argon atoms per DDT molecule damaged the SAM sufficiently to allow penetration of an aqueous solution of ferricyanide to the surface of the gold. This solution etched the gold and transformed the patterns in the SAMs into structures of gold; these structures had edge resolution of less than 100 nanometers. Regions of SAMs as large as 2 square centimeters were patterned by exposure to a beam of metastable argon atoms. These observations suggest that this system may be useful in new forms of micro- and nanolithography.

Fabrication of submicrometer features on curved substrates by microcontact printing.

Microcontact printing (mu CP) has been used to produce patterned self-assembled monolayers (SAMs) with submicrometer features on curved substrates with radii of curvature as small as 25 micrometers. Wet-chemical etching that uses the patterned SAMs as resists transfers the patterns formed by mu CP into gold. At present, there is no comparable method for microfabrication on curved surfaces.