Science Biochemical electrode uses tissue slices Just how "crude" can the biochemical ,part of a biochemical electrode be and still be useful? Generally these electrodes couple a purified enzyme (the biochemical part) with an ion-sensing electrode (the electrochemical part) to make a very sensitive and selective probe for a particular biological molecule. In some cases whole bacteria can be used in place of the purified enzyme (C&EN, Oct. 25, 1976,
mine. Such a system would be even more straightforward than the arginine electrode since it would bypass the urea-toammonia conversion step. Results on this system are still very preliminary, he says, but promising. Rechnitz sees electrodes of this type primarily as teaching tools rather than research tools. "It's a remarkably simple way to make an electrode biologically
Liver tissue converts arginine to urea -Ammonia electrode -Gas-permeable membrane
-Liver tissue slice
-Dialysis membrane -4
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page 23). Last week, Dr. Garry A. Rechnitz of the University of Delaware told the Metrochem '78 meeting in South Fallsburg, N.Y., that tissue slices can also be used in place of purified enzyme. Rechnitz, along with graduate student Mark Meyerhoff, has developed an arginine-sensitive electrode that uses a thin slice of liver tissue to make it sensitive to arginine. They place a thin section of beef liver at the sensing end of a membrane electrode for urea. The liver slice contains arginase, an enzyme that converts arginine to ornithine and urea. The urea, in turn, is converted by the enzyme urease in the urea-sensing electrode to ammonia. The ammonia generated is measured by an ammonia-sensitive ion-sensing electrode. Considering how completely unpurified the arginine-sensing part of this electrode system is, it is a remarkably good electrode for arginine, Rechnitz says. The electrode's response to arginine covers almost a 100-fold range and is sensitive to arginine concentrations as low as 0.1 mM. The response slope for this electrode, which shows the efficiency of the biochemical conversions taking place, is comparable to that of a conventional biochemical electrode for arginine. Measurements take about five minutes. There may be other tissues that can be used in electrodes in the same way, Rechnitz says. He and Meyerhoff are investigating kidney slices used in conjunction with a commercially available ammonia electrode as a sensor for gluta16
C&EN Oct. 9, 1978
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sensitive," he explains. "It's something that makes sense to students." Similar systems that use whole bacteria to provide the biochemical sensitivity are proving in some cases to be more sensitive, longer lasting, or better able to measure a specific substance than purified enzyme electrodes. Finding out whether tissue-slice electrodes will have any of these advantages will require further development. D
BNL synchrotron soliciting experiments With at least part of the National Synchrotron Light Source (NSLS) scheduled for experimental use by mid-1981, Brookhaven National Laboratory is starting to plan ahead for the experiments. It is now seeking expressions of interest from members of the scientific community who wish to take advantage of NSLS's capabilities either as general users or as members of a Participating Research Team. The facility, now under construction at Brookhaven, will have two electron storage rings dedicated exclusively to production of photons for experimental use. A*0.7-GeV ring providing radiation in the wave-length interval between infrared and about 10 A is scheduled to be ready for experimental use by mid-1981. The second, a 2.5-GeV ring, whose spectrum, with beam wiggler magnets, will extend to about 0.1 A, should be available for ex-
perimental use by the end of 1981 or early 1982. There will be room for operating 40 or more experiments on each of the two storage rings. But, BNL says, providing beam line instrumentation for such a large number of experiments on a reasonable time scale will be beyond the capability of the NSLS staff. So BNL has worked up a policy for instrumentation and utilization of the facility. It is designed to enable scientists at Brookhaven, other national laboratories, universities, and industrial laboratories to cooperate in designing and building experimental apparatus and carrying out research with a minimum of formal administrative interaction. The policy sets up two categories of scientific utilization. In addition to beam lines constructed by the NSLS staff for general use, a number of beam lines would be set aside for Participating Research Teams, each of which would be given priority for a fraction of scheduled beam time for the particular beam line it constructs. The Participating Research Team will provide expertise, funds, or specific instrumentation (monochromators, target chambers, mirrors/gratings/crystals, detectors, and the like), for construction of a specific beam line. It will schedule experiments to be done by its own members. General users or user groups would have the unawarded fraction of time on the beam lines assigned to Participating Research Teams and the beam lines built by the NSLS staff and intended for general use. When a general user is using a team's beam line, BNL expects team members to provide technical assistance, and, if mutually desirable, scientific collaboration with the general user. The lab sees this aid as an obligation incurred by the team in return for the photons that it has access to for its designated fraction of the scheduled beam time. The director of BNL will appoint a program advisory committee to provide advice on utilization of the facility, on proposals, and on priorities for use of the various experimental beam lines. BNL will solicit proposals for use of the facility and the committee will review and rank the proposals. It will take into account not only scientific merit but the resources of NSLS and potential resources available to specific proposed research teams. The BNL director, on the advice of the committee, will approve grants of beam time to general users or user groups. For a research team's beam line, this will be done in consultation with the.spokesman of the relevant team. For now, BNL is seeking expressions of interest or intent from those who wish to take advantage of NSLS as general users or as members of a Participating Research Team. BNL notes that a team in some cases could be formed by BNL's bringing together researchers with common interests. BNL wants responses by Dec. 31. They should be sent to Dr. Martin Blume, Department of Physics, Brookhaven National Laboratory, Upton, N.Y. 11973. D
