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BIOTECHNOLOGY Patch-clamp method gets a makeover The first successful demonstration of patch-clamp recordings using a planar glass chip has recently been performed by an interdisciplinary group of German scientists at the University of Munich and the Munich-based startup company Nanion Technologies GmbH (both in Germany). The new method is a significant step toward the automatic highthroughput monitoring of electrical currents through the ion channels of cell membranes. Ion channels are crucial for physiological cell processes and important targets for drugs against diseases, such as epilepsy, cardiac disrhythmia, high blood pressure, or diabetes. The traditional patch-clamp technique was introduced in the early 1970s by Erwin Neher and Bert Sakmann, winning them the Nobel Prize for medicine and physiology in 1991. Their technique soon became the “gold standard” in studying the function of ion channels in cell membranes. In the most popular variation—the whole-cell technique—a cell is partly sucked into a glass micropipette filled with ionic solution to form a tight electrical seal. The vacuum ruptures the cell
membrane, and intracellular access is provided through the small, open “patch” that results. The ion current flow between the inner cell—accessed through the pipette—and the outer cell can thus be measured over the entire cell membrane. The electrical charge is “clamped” at a constant level to measure the ion current through the membranes. Patch clamping is still a laborious manual task under the microscope and needs the steady hands and patience of a very skilled experimenter. It is difficult, if not impossible, to combine traditional patch clamping with optical, fluorescent, or scanning probe methods; there simply is no place to install extra equipment among the objective, sample, micropipette, and wires of the inverted light microscope that is normally used. On the other hand, the new chip—developed by Niels Fertig, Robert Blick, and Jan Behrends—can easily be scaled up into a parallel array of electrodes, allowing a huge number of cells to be measured in parallel (Biophys. J. 2002, 82, 3056–3062). “The chips are made from planar fusedquartz wafers,” explains Fertig. A single
high-energy gold ion is shot through the chip, leaving behind a track of molecular damage. “Then we etch the ion track open with hydrofluoric acid.” Stopping the etching process at the correct moment leaves behind a 0.5- to 2-µm-diam hole, which is on the same scale as the previously used pipette tips. A cell suspension is loaded onto the patch-clamp chip, and when gentle suction is applied, a single cell automatically positions itself tightly on the aperture. The low pressure on the underside opens the patch in the cell membrane. To ensure electrical conductivity, the chip is covered with electrolytes on both sides, which are isolated from each other by the wafer. Electrodes in the electrolyte are connected to a commercial amplifier and the data acquisition software. “An important feature is the possibility [of combining] the new technique with . . . additional measuring equipment,” says Behrends. “Because the chip is [planar] and transparent, highresolution fluorescent microscopy, for example, can enable new insights into the function of ion channels.” a —Hanns-J. Neubert
PEOPLE Division of Analytical Chemistry graduate fellowship awards Eleven analytical chemistry graduate students have been selected by the ACS Division of Analytical Chemistry to receive fellowships for the 2002– 2003 academic year ($18,000) or for the summer ($6,000). The program encourages basic research in analytical chemistry and recognizes future leaders in the field.
Full-year fellowships Carrie Donley of the University of Arizona (Neal Armstrong). Donley’s work focuses on understanding and control-
ling the compositions of surfaces and interfaces relevant to organic electronic devices. Her fellowship is sponsored by Procter & Gamble. Joel Kimmel of Stanford University (Richard Zare). Kimmel is working to further develop Hadamard transform TOF-MS and to
apply this high-duty cycle technique to capillary format separations. His fellowship is sponsored by Merck and Co. Shane Peper of Auburn University (Eric Bakker). Peper designs novel polymeric materials for improving the lifetime of potentiometric and optical ionselective chemical sensors, and he applies this technology to the development of microsphere-based sensing strategies
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for the analysis of clinical electrolytes. His fellowship is sponsored by Eli Lilly and Co. Kimberly Roy of the University of Alberta (Charles Lucy). Roy is using a theoretical dielectric friction model to understand the selectivity changes that are observed in aqueous organic and nonaqueous CE. Her fellowship is sponsored by DuPont.
Summer fellowships Zoraida Aguilar of the University of Arkansas (Ingrid Fritsch). Aguilar is fabricating microelectrochemical enzyme-linked DNAhybridization sensors for the detection of Cryptosporidium parvum hsp70 mRNA in drinking water. Her fellowship is sponsored by Johnson & Johnson Pharmaceutical Research and Development. Frederick Cox of the University of Delaware (Murray Johnston). Cox is developing MALDI and other MS methods for the characterization of olefinic polymers and copolymers. His fellowship is sponsored by the Society for Analytical Chemists of Pittsburgh. Amanda Haes of Northwestern University (Richard Van Duyne). Haes’s work focuses on designing metal nanoparticle systems and utilizing their unique optical 460 A
properties to create highly sensitive biological and chemical nanosensors. Her fellowship is sponsored by Eastman Chemical Co. Fanyu Meng of the University of Illinois (Neil Kelleher). Meng uses customized FT-MS and a “top-down” analysis strategy to establish an efficient platform for simultaneous identification of intact proteins and characterization of their posttranslational modifications in eukaryotic systems. His fellowship is sponsored by the Dow Chemical Co. Foundation. Allison Null of Virginia Commonwealth University (David Muddiman). Null is developing electrospray ionization FT ion cyclotron resonance MS methods to characterize genetic variation in the human genome. Her fellow-
ship is also sponsored by the Society for Analytical Chemists of Pittsburgh. Michael Roper of the University of Florida (Robert Kennedy). Roper is developing microfabricated systems for the simultaneous measurement of cellular secretion (competitive CE immunoassay) and intracellular secondary messengers (electrochemical sensors or fluorescent reporter dyes). His fellowship is also sponsored by the Society for Analytical Chemists of Pittsburgh. Rachel Smith of Pennsylvania State University (Paul Weiss). Smith is investigating the near-field optical and electronic coupling of heterogeneous nanoparticle structures using photon-emission scanning tunneling microscopy. Her fellowship is also sponsored by the Society for Analytical Chemists of Pittsburgh.
DAC fellowship nominations Applications are now being accepted for the 2003–2004 Division of Analytical Chemistry Graduate Fellowships. These fellowships are available to full-time graduate students working toward a Ph.D. in analytical chemistry. Applicants must be nominated by their graduate thesis advisers and must have completed their second year of graduate studies by the time their fellowships begin. The applicant’s thesis adviser must be a member of the Division, and only one nomination per adviser will be accepted. Applicants must demonstrate outstanding research ability and accomplish-
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ment, as evidenced by peer-reviewed publications in analytical chemistry. In addition to the application forms, nominees must submit three letters of recommendation and copies of their undergraduate and graduate transcripts. Applications and information are available at www.wabash.edu/ acsgraduatefellowship/home.htm. For further information, contact Richard F. Dallinger (preferably by e-mail) at Wabash College (765-3616242; fax 765-361-6340; dallingr@ wabash.edu). Completed application packages must be submitted by December 6, 2002.
