news
ANALYTICAL CURRENTS (a)
Living cell microarray First came microarrays of DNAs, then proteins, and now living cells. This newest strategy, developed by David Sabatini and Junaid Ziauddin of the Whitehead Institute for Biomedical Research, allows the functional analysis of many gene products in parallel and can be used to identify drug targets or to discover gene products that alter cellular physiology. To begin, plasmid DNA that has been encapsulated in gelatin is robotically plated in a grid pattern on a slide. The slide is exposed to a lipid transfection reagent, placed in a culture dish, and covered with a medium containing cells. When cells grow over a spot, they take up the plasmids and express the new DNA. For example, the researchers plated mammalian cells on a slide containing a construct for green fluorescent protein (GFP). Cells next to the array spots were transfected and expressed GFP, which was easily verified using fluorescent light. The array spots were ~150-
DNA/gelatin
(b)
Slide µm diam, so the GFP-expressing Lipid Cells clusters contained 30–80 cells. Other experiments transfected cells with DNA for specific Assay receptors; these cells were then identified with ap- (a) The microarray protocol and (b) the laser scan of a microarray in which cells have taken up plasmid DNA and now express the green propriate ligands fluorescent protein. (Adapted with permission. Copyright 2001 Nature for the receptors. Publishing Group.) In a more sophisticated experiment, microarrays containing 192 different complementaThis new strategy works with various ry DNAs cloned in expression vectors complementary DNAs and detection were used to transfect mammalian cells. schemes and identifies cells that have Screening these transfected cells identiexpression levels only slightly above fied proteins involved in activities such background or that undergo transient as tyrosine kinase signaling and cell death changes. The most difficult step, say the and adhesion. Another analysis investiauthors, is making the DNA expression gated subcellular distributions, such as a constructs for the microarrays. (Nature protein that concentrated in the nucleus. 2001, 411, 107–110)
Catalysis by FRET High-throughput screening has been so
this example, high-throughput methods
ing materials was tagged with a fluorophore
well received in the pharmaceutical com-
identify the optimal catalysts and catalytic
and the other with a quencher. When the
munity that this powerful technique is mi-
conditions for the formation of a-aryl
cyanoacetate formed, the fluorescence
grating into other areas of chemistry. In
cyanoacetates. What makes this report in-
dropped. Thus, the FRET emission was in-
teresting is that O
O O2S N
O
O2S N
CN
O
Strong fluorescence Boc + N
NMe2
N
Br
John Hartwig and
The formation of a-aryl cyanoacetates
colleagues at Yale
was aided by the presence of a palladium
University followed
catalyst. Using a 96-well format and the
the reactions by
FRET data, the researchers investigated
fluorescence reso-
the effects of various forms of the catalyst,
nance energy
changing bases, and different solvents on
transfer (FRET).
the reaction yield. (J. Am. Chem. Soc. 2000,
BocN CN
Catalyst
versely related to the reaction yield.
NMe2 N
N
Weak fluorescence
N
Reaction to form an a-aryl cyanoacetate, which was used to evaluate catalysts.
One of the start-
123, 4641–4642) J U LY 1 , 2 0 0 1 / A N A LY T I C A L C H E M I S T R Y
349 A
news
ANALYTICAL CURRENTS Evidence for electroosmotic perfusion
Nominal particle Subparticle
Gigapore
Macropore Dead-end pores – + – +
– +
+
– +
+ –
– +
Pore flow –
+ –
– – +
+
– + +– +
–
Flow-through pores
–
–
+ + – –
+ –
E
– +
+ +
Researchers know that capillary electrochromatography (CEC) often performs better than capillary HPLC. The reason why has been less certain. But Ulrich Tallarek, Ernst Bayer, and colleagues at Wageningen University (The Netherlands) and Universität Tübingen (Germany) offer evidence that electroosmosis through, rather than around, the porous media in the capillary is largely responsible for the improvement. The researchers compared pressuredriven and electroosmotic flows through a fixed bed of electrically charged, porous
ueo + –
–
+
θ
uax uax ∝ E·cos2θ
Schematic showing the pore network in a hierarchically structured particle and the electroosmotic flow through a gigapore. (Adapted with permission. Copyright 2001 Wiley-VCH Verlag GmbH.)
particles packed in a capillary under various conditions. By using NMR to trace the fluid molecules, they separated the intra- and interparticle kinetics. Focusing on the intraparticle mass transfer kinetics, they determined that applying an electric field significantly enhances the exchange of fluid molecules, whereas applying pressure to the porous particles has little effect. This, along with other observations, argues that an electroosomotic perfusion mechanism exists. The researchers note that the interconnectivity of the particles’ pores is more important than their average diameter for electroosmotic perfusion. They suggest that attention to both the electroosmotic and separation characteristics of CEC particles may enhance analyses. (Angew. Chem., Int. Ed. 2001, 40, 1684–1687)
LC/TOFMS toxicology screens Forensic toxicologists routinely test biolog-
plied Biosystems created an LC/TOFMS
program that calculated monoisotopic
ical materials for a wide array of pesti-
method to qualitatively screen for toxico-
masses created the target library, which
cides, therapeutic and illicit drugs, and
logically relevant drugs and their main
contains 433 drugs and metabolites rang-
other xenobiotic substances. In previous
metabolites in urine samples without ref-
ing from 105 to 734 Da. Final identification
broad-scale screening techniques, access
erence compounds. The researchers also
was based on exact mass. Collection of
to reference substances has limited the
established an automated calibration ca-
full spectra was a benefit because sam-
availability and content of chromatograph-
pability and a post-run computer search
ples could be searched again for a par-
ic or spectroscopic libraries, whether they
based on elemental formulas to help
ticular compound without re-running.
were generated in-house or purchased.
process the data.
However, in drug discovery applica-
After solid-phase extraction and LC
The LC/TOFMS method was tested with autopsy urine, and the 5- to 10-ppm
tions, time-of-flight MS (TOFMS) has
separation of the sample, a full TOFMS
mass accuracy obtained for most com-
shown promise in determining the elemen-
spectrum was recorded, automatically cal-
pounds compared well with GC and thin-
tal composition of metabolites. Building on
ibrated, and compared with the target li-
layer chromatography analyses. (Rapid
this use, Merja Gergov and colleagues at
brary for positive identification. Entering
Commun. Mass Spectrom. 2001, 15,
the University of Helsinki (Finland) and Ap-
each substance’s elemental formula into a
521–526.)
350 A
A N A LY T I C A L C H E M I S T R Y / J U LY 1 , 2 0 0 1
news
A lineup in the microchannel On a macroscale, it’s possible to create patterns in solutions containing paramagnetic particles by applying external magnetic forces, which induce the formation of particle aggregates. Mark Hayes and colleagues at Arizona State University and ThermoBiostar have been extending these observations to fluid-based micro-
and Brownian motion and electrostatic repulsion quickly restore the original disarray of the colloidal suspension once the magnetic field has been removed. The formation of supraparticle structures depends on the particle diameters, the volume fraction of the solution, the magnetic susceptibility, the intensity of
the magnetic field, the channel geometry, the system’s temperature, and the surface properties of the microchannels. These factors will influence possible on-chip applications such as the fabrication of optics or structural elements for separations, filtration, or biological interactions. (Langmuir 2001, 17, 2866–2871)
B
Cells in a pattern A
Imagine placing a single cell exactly B
which promotes adhesion of cells.
where you need it. For applications rang-
The coated microwell plate was then
ing from building biosensor circuits, to
exposed to a suspension of bovine capil-
screening combinatorial libraries, to engi-
lary endothelial cells. In a typical experi-
neering new tissues, such control would
ment with 50-µm-diam, 1.3-µm-deep mi-
be beneficial. George Whitesides and his
crowells, the bovine cells adhered to
colleagues at Harvard University and Chil-
~70% of the wells. Narrower and deeper
C D E F
Behavior of paramagnetic particles in 20-µmdiam microchannels. (A) No applied external magnetic field, B. (B–E) Alignments of paramagnetic particles with different orientations of B. (F) Upon removal of B, paramagnetic particles resume colloidal state.
dren’s Hospital and Harvard Medical School describe a method for depositing proteins or cells selectively into microwells and demonstrate their approach by placing mammalian cells into wells with
devices as an alternative to traditional microfabrication techniques. The researchers demonstrate that paramagnetic particles in microchannels produce unique, dynamic, and controllable structures when interactions are induced and manipulated via an external magnetic field. Direct physical interface with a magnet is not required to see the effect. These induced structures, referred to as supraparticle structures, are not attached to any channel wall and are not distorted when rotated or when transported by pressure or electrokinetic flow. Optical microscopy shows that the structures respond to changes in external magnetic field strength and orientation,
≤100-µm diams and ≤50-µm depths. The microwells were fabricated in the inert, transparent elastomer poly(dimethylsiloxane). To keep the cells off of surfaces other than the microwells, the space between the
Bovine capillary endothelial cells adhere selectively to wells coated with fibronectin. A layer of bovine serum albumin prevents adhesion between the wells. (Inset) Two cells have spread to entirely cover their wells.
wells was coated with bovine serum albumin (BSA). Air bubbles trapped in the
wells had lower occupancies, and wider
microwells kept any BSA from entering
and deeper depressions had enough
these depressions. The microwells were
space for multiple cells in one well.
then coated with the protein fibronectin,
(Langmuir 2001, 17, 2828–2834)
J U LY 1 , 2 0 0 1 / A N A LY T I C A L C H E M I S T R Y
351 A
news
ANALYTICAL CURRENTS Theory for a SNEM Porous pads for PCR To improve the efficiency of DNA microarray analysis, researchers have been working on ways to integrate onchip PCR. Sergei Tillib, Andrei Mirzabekov, and Boris Strizhkov at Argonne National Laboratory and the Russian Academy of Sciences describe an approach in which on-chip
The scanning near-field microscope (SNOM) moved optical microscopy past the Rayleigh diffraction limit, which held resolution to one-half of the optical wavelength. Instead, the SNOM’s resolution increases as its tip diameter decreases. Unfortunately, the intensity of the light also decreases. A way around this limitation could be the scanning near-field exciton microscope (SNEM), which creates images using excitons—electronic excitations in a dielectric media—rather than an opti-
cal light field. Elisabeth Paule and Peter Reineker of the Universität Ulm (Germany) investigate the imaging properties of a SNEM and provide a theoretical framework for the optimization of its resolution and contrast. They also model the detection of single molecules on a surface, studying the intensity as a function of the wavelength of the incident electric field and the distance between the tip and sample. (J. Phys. Chem. B 2001, 105, 4293–4304)
gel pads serve as reaction chambers
are many copies of the two primers needed for PCR. The sample DNA is allowed to hybridize with the primers, and the unhybridized sequences are removed by washing. Then the chip is soaked in a solution containing PCR reagents and ribonuclease A, which releases one type of PCR primer from its tethers—a step that improves the amplification efficiency. A third primer can be used to test for particular single-nucleotide mutations. After amplification, the product is denatured and allowed to interact with fluorescent probes attached elsewhere on the chip’s surface. The researchers tested the method by analyzing mutations in three antibiotic resistance genes in
Mycobacterium tuberculosis. (Anal. Biochem. 2001, 292, 155–160)
352 A
Researchers have previously harnessed single-stranded DNA “hairpins” to serve as fluorescent probes, popularly known as “molecular beacons”. Now, Jocelyn Grunwell and colleagues at the University of California–Berkeley and Lawrence Berkeley National Laboratory use hairpins as a model system for studying the kinetics of single molecules bound to surfaces. The researchers attached hairpins to glass surfaces using one of two biotin– streptavidin interactions or using a covalent immobilization strategy. They monitored the opening and closing of the
hairpins using fluorescence imaging and applied a two-state model when analyzing the data. On the basis of a previous study, the researchers predicted that the average open-state lifetime for their hairpins would be ~3 ms. Instead, the calculated lifetimes were 133 ± 5.5 ms for a hairpin with a 7base-pair (bp) stem and 142 ± 22 ms for a 9-bp stem. The difference between predicted and actual was apparently due to variations in the loops’ sequences. On the other hand, closed-state lifetimes were 45 ± 2.4 ms for a 7-bp stem and 103 ± 6.0 ms for a 9-bp stem, and as expected, they were independent of the loop characteristics. The relatively long open-state lifetimes suggest that being tethered to a surface stabilizes the kopen Cy5 open state of the hairpin and affects the overall kikclosed netics of the system. Thus, TMR the researchers conclude Biotin or thiol for that models derived from surface attachment Closed Open polymer simulations and thermodynamic calculations may not be generally applicable to hairpins and that sequence information 0 1 0 1 should be considered. (J. Energy transfer Energy transfer Am. Chem. Soc. 2001, Schematic of the closed-to-open transition of a DNA hairpin. 123, 4295–4303)
A N A LY T I C A L C H E M I S T R Y / J U LY 1 , 2 0 0 1
Events
Immobilized within each gel pad
Individual hairpin dynamics
Events
for PCR amplification.
news
RESEARCH PROFILES Assessing carcinogen exposure with MS dard LC runs at 0.5–1.0 mL/min, but technique does not necessarily have a For researchers, the complexity of canmore recent work has introduced flow high resolving power,” Vouros explains. cer continues to be vexing. So many rates of 10–20 nL/min. For these stud“You may see one spot, but it may actuthings can go wrong in a cell and lead ies, 10- to 20-nL flow rates couldn’t ally have two or three or more [kinds of to its transformation that it is difficult adducts] because the resolution is insufto pinpoint the specific mechanisms that be achieved routinely, so Vouros and his colleagues settled on ~200 nL/min. ficient, particularly for human samples, underlie disease. Add to that the unfor“That provided a very dramatic improve- where a number of lesions may be detunate fact that practically every known tected.” In addition, the 32P post-labelvariety of cancer follows a different patho- ment in sensitivity,” he says. To demonstrate the method, the ing does not provide structural informalogical course, and it is little wonder that team looked at the heterocyclic aromattion to identify the adduct. MS has the “war on cancer” has produced only ic amine 2-amino-3-methylimidazo[4, more resolving and defining capability spotty victories. 5-f ]quinoline (IQ), which is a potent than the radioactive method, he says. Even as the mutations and genetic carcinogen in rodents and nonhuman However, the sensitivity of the capilcascades that lead to tumorigenesis beprimates. IQ is found in cooked meat lary LC/MS technique (2 adducts in come known, the contributions of enviand fish and in cigarette smoke conden108 bases) hasn’t reached that of radioronmental factors such as diet remain activity (1 adduct in 1010 elusive. “There is a school bases). Still, the researchers of thought that some canHV are edging closer. “I think cers are initiated by a . . . Negative pressure – sample introduction we’re becoming competimodification of the DNA + tive,” says Vouros. “The inby some exogenous comteresting thing is that you ponent,” says Paul Vouros S 400 µL/min. 200 nL/min. really cannot get by with of Northeastern Universione method alone, in my ty. But so far, theory has Splitter opinion . . . . [We are going ventured ahead of methodto] use those two techniques ology, and there is little Microbore Finnigan TSQ700 in parallel.” proof to support the hyWaste valve with 0.5 µL internal In time, Vouros hopes the pothesis. Before researchPacked capillary sample loop MS technique’s sensitivity ers can gauge exposure column (75 µm I.D.) eventually will surpass that risk accurately, they need Sheathless/liquid junction of 32P post-labeling. The tools to directly measure µESI tip work to date has been done molecular impact on cells. Schematic of the capillary LC/microelectrospray ionization MS system. on a 10-year-old mass specIn the current issue of Analytical Chemistry (pp trometer, he notes. “My ex2819–2827), Vouros, pectation is that, with better Robert Turesky, and their colleagues at sate, and it forms stable adducts with instruments, people should be able to Northeastern, the U.S. National Center DNA. The researchers dosed rats with improve on what we’re reporting now for Toxicological Research, and Nestec, .05, .5, 1, and 10 mg/kg of IQ by by at least a factor of 10, if not better, Ltd. (Switzerland) report a method that body weight and collected liver DNA in the very near future,” he says. The they hope will give researchers the power samples 24 h later. Even at the lowest real test will be whether the method to test exogenous influences on tumoridosage, the researchers could detect and can detect DNA adducts from the lung genesis. The method combines LC and quantify adducts with a S/N of 16:1, tissue of, say, a chronic smoker. microelectrospray ionization MS/MS and the results were reproducible from Vouros thinks he’s close. “With a litto detect modified bases starting with day to day. tle bit better manipulation and improv~300 µg of DNA. That translates into The LC/MS approach has some ading our know-how—and with a new finding ~200–300 modifications per vantages over the most commonly used generation of instruments—this can cell, says Vouros. Although it’s a formimethod to measure DNA adducts: 32P be translated to humans in the near dable task, it is close to the level that post-labeling, in which adenosine triphos- future,” he says. If he’s right, the old is necessary to investigate the contribuphate—the cell’s fuel—is tagged with question of Nature versus nurture, at tions of diet to cancer risk. the radiolabel, and the modified DNA is least as applied to cancer, might finally The enhanced ability stems primarily detected by thin-layer chromatography be answered. –Jim Kling from an improvement in fluidics. A stan- or HPLC. “[One] problem is that the
J U LY 1 , 2 0 0 1 / A N A LY T I C A L C H E M I S T R Y
353 A
news
RESEARCH PROFILES Detecting living Cryptosporidium zone, indicating whether living parasites stranded RNA target sequence. LipoThe protozoan parasite Cryptosporidium are present in the test sample. somes bearing biotin and oligonuparvum, usually found in water, can be Once added to the strip, the test takes cleotide reporter probes, which are life-threatening to people with impaired only 8–10 min, says Durst, although excomplementary to the target sequence, immune systems and may cause serious tracting the RNA from the organisms and gastrointestinal illness in healthy people. are then added to the mixture. The performing the NASBA takes an additionprobes will hybridize to any target seThe parasite’s oocysts are not killed by al 2–3 h. “But even going through that, quence that is present. The mixture is standard disinfection methods such as we still have an assay that can be done chlorination and have caused major out- then applied to a nitrocellulose test in less than a day,” he points out. The strip. breaks of illness in the United States, The test strip contains two zones. The method can detect as little as 80 fmol of United Kingdom, and Japan. C. parvum target sequence. The standard proceThe researchers develdure to detect C. parvum oocysts is staining with oped the test-strip format fluorescent antibodies and for easy in situ use at Antibiotin antibody identification under a miwater treatment plants. Biotin croscope. However, this (Unlike PCR, NASBA approach often incorrectly can be done with a simple Reporter probe and antisense reporter estimates the number of heating block rather than probe organisms because it doesspecial thermal cycling n’t distinguish between equipment.) Durst would Target oligonucleotide living and dead parasites. also like to see the test 2 2 In the current issue of used in restaurants. “If 1 1 Liposome Analytical Chemistry (pp you’re washing food with 3162–3167), Richard contaminated water, Side view Side view Durst and colleagues at you’re taking something Schematic of the test strip assay. In a positive test, the liposome Cornell University dethat’s safe and contamibinds to (2) the antibody zone. In a negative test, it binds to (1) the scribe a quick, sensitive, nating it,” he says. An capture zone. test strip-based method at-home test may even to detect small amounts be possible in the future. of living oocysts via the This approach is just first, called the capture zone, contains binding of amplified RNA to oligonuone of many that Durst’s laboratory has oligonucleotides that are complementacleotides immobilized on liposomes. developed using liposomes, and it could ry to the reporter probe (and thus iden- be easily adapted to other organisms by The method takes advantage of the tical to the target sequence), whereas fact that only living organisms produce changing the reporter probe and the the second, called the antibody zone, RNA. “DNA stays around for a long complementary oligonucleotide, he says. contains anti-biotin antibodies. If no time,” Durst explains. “In contrast, For example, the researchers have used target sequence is present, then the remessenger RNA is rapidly degraded. a similar RNA-based approach to detect porter probes on the liposomes will bind Shiga toxin produced in live E. coli So if an organism is dead, [its RNA] to the oligonucleotides in the capture won’t be around for very long.” O157:H7 or Shigella. In addition, antizone, providing an internal control. If, The procedure involves heating the bodies or proteins can be attached to on the other hand, the target sequence organisms to make them produce large the liposomes instead of the oligonuamounts of the RNA for heat shock pro- was present in the sample, then the recleotides. In collaboration with Laurie porter probes on the liposomes will altein 70 (hsp70)—part of this sequence Locascio and Michael Tarlov at the Naready be bound to the target, leaving no tional Institute of Standards and Techappears to be unique to C. parvum— sites available to bind to oligonucleotides nology, the researchers also developed and extracting the RNA (Anal. Chem. in the capture zone. In this case, the li2001, 73, 1176–1180). A segment of a microfluidic C. parvum test, which is posomes will migrate by capillary action the hsp70 RNA is further amplified even more sensitive (pp 2952–2958). to the antibody zone, where their biotin “Sensitivity is one of the key advantages using nucleic acid sequence-based amlabels bind to the anti-biotin antibodies. we have with the liposome,” says Durst. plification (NASBA)—a method similar Because the liposomes encapsulate a red “It’s almost a universal reagent.” to PCR except that it does not require –Alka Agrawal dye, they are easily visualized in either thermal cycling—to produce a single-
354 A
A N A LY T I C A L C H E M I S T R Y / J U LY 1 , 2 0 0 1
news
LABORATORY PROFILE Extreme electrochemistry the creatures that live there and survive in total darkness in a completely chemosynthetic food chain has fascinated scientists since their discovery. In situ electrochemistry, pH, and temperature data were combined with analyses performed aboard the surface support ship to help understand the biology within the steep temperature and concentration gradients found at the vents. The results were published this year (Nature 2001, 410, 813–816). There are several compelling reasons to use voltammetry in this setting. Samples collected at the bottom and transported to the surface for analysis undergo a 200-fold change in pressure. Sulfide equilibria, notoriously temperature- and pressure-sensitive, are difficult to duplicate and study at the surface. Measurements performed in situ should give much more reliable results, Nuzzio reasoned. He chose electrochemistry because it can sample small volumes quickly and reliably under extreme conditions. In addition, voltammograms give information about the identity and amount of the electroactive species present. “[Yet] the real power of electrochemical measurement in situ is . . . that it can reveal information about species complexation—information not available with most metalsensitive spectroscopies,” says Nuzzio. “The Alvin crew generally has a skeptical view of new equipment,” says Nuzzio. But the system worked so well that the same instrument—with a smaller housing and remote operating capabilities—was deployed from a platform off the Knorr, another WHOI research vessel, in late May to map out the water column in the Black Sea. And Nuzzio was along to make sure everything went smoothly. –Zelda Ziegler COURTESY OF DON NUZZIO.
“Electrochemistry works!” was the radio sonnel sphere via laptop computer. “The Alvin instrument is capable of performreport from 2.5 km below the ocean’s ing most standard electrochemical techsurface, 5 hours into the dive to study niques—dc, linear sweep, and cyclic the thermal vents off the west coast of voltammetry; differential pulse, square Mexico. With this comment the starwave, and stripping analysis—all selecboard observer, Don Nuzzio, analytical table through the laptop,” says Nuzzio. chemist and president of Analytical InThe electronic portion of the instrustrument Systems, Inc. (AIS) of Flemment weighs about one pound, but the ington, NJ, marked the end of 2 years aluminum casing to protect it from of hard work to get aboard the deep submergence vehicle (DSV) Alvin and signaled the surface support group to start celebrating. That was one year ago. Nuzzio founded AIS in 1989 with the goal of making low-cost, portable, rugged, and reliable analytical instruments for use in the laboratory or the field. AIS received two Small Business Innovation Research grants to develop equipment to correlate the chemistry at deep-sea thermal vents with the distribution of life forms typically present there. In one grant, Nuzzio runs electrochemical analyses aboard the Alvin. the National Science Foundation funded the development of a probe to measure the crushing pressures at the sea floor temperature, pH, and electrochemistry brings the unit’s total weight to about in water columns and in the sediment 100 pounds. This hardware was designed beds below them. In the other grant, the National Aeronautics and Space Ad- to operate with a special probe, made by George Luther of the University of ministration funded the adaptation of this instrument to the micromanipulators Delaware, which includes voltammetric on DSV Alvin, the small, maneuverable, electrodes, a temperature probe, and a underwater vehicle developed by Wood’s syringe sampler to collect water samples for further analysis on the surface. The Hole Oceanographic Institute (WHOI) probe was inserted into the flowing wain 1964. In a typical untethered dive, ters of the hydrothermal vents and enAlvin can transport a pilot and two obdured extreme temperature shifts—from servers in relative comfort and safety to a depth of 4.5 km, where they can navi- 400 °C at the vents to 2 °C in the ocean only a short distance away. gate the bottom, collect samples, take Entire ecosystems exist at black smokphotographs, and resurface the same day. ers—the thermal vents on the sea botAIS built a submersible potentiostat to control several electrodes and perform tom that spew a hot solution of dissolved electrochemical analyses. The electronics iron, hydrogen sulfide, and other complex ions into the cold dense brine at the include a microprocessor that can be sea floor. The origin and distribution of controlled by someone inside the per-
J U LY 1 , 2 0 0 1 / A N A LY T I C A L C H E M I S T R Y
355 A
news
GOVERNMENT AND SOCIETY ACS to vote on new division At the August 2001 ACS National Meeting in Chicago, IL, board members are expected to vote in favor of creating a new ACS division focused on laboratory automation. The new division will stem from a partnership with the Lab Robotics Interest Group (LRIG; http://lab-
robotics.org), a grassroots organization based out of Martinsville, NJ, which began 14 years ago as a topical group of the North Jersey section of the ACS. Dennis France of Novartis Oncology, executive chair of the LRIG Mid-Atlantic Chapter, says the idea to create a new di-
An “udder” milk safety test In May 2001, milk safety specialists at the biennial National Conference on Interstate Milk Shipments (NCIMS) reviewed and approved a new multichannel immunoassay as a method for screening U.S. milk for the b-lactam family of antibiotics, reports NCIMS Laboratory Committee Chairman Lee Jensen. The b-lactam family—named for the b-lactam ring in the structure— includes several heavily used antibiotics, including penicillin, cephalosporin, and their derivatives. NCIMS acceptance of any new test kit is the ultimate stamp of approval for using the assay in the U.S. National Milk Drug Residue Testing Program. According to a 1992 General Accounting Office report to the U.S. House of Representatives, the National Milk Drug Residue Testing Program was established after surveys conducted several years earlier by the Wall Street Journal and the Center for Science in the Public Interest indicated that 20% and 38%, respectively, of retail milk samples tested may have contained residues from drugs given to animals. Among those drugs were the suspected human carcinogen sulfamethazine and drugs not approved by the U.S. Food and Drug Administration (FDA). According to Rob Byrne of the National Milk Producers Federation, “The levels of antibiotics in milk can be a consumer public health issue of antibiotic resist-
356 A
ance, [and] high levels of antibiotics in milk [also] may reflect disease in the dairy cow.” The maximum residue level allowed in milk for each of the six b-lactams varies between 5 and 50 ppb. The currently approved tests are able to detect the specified levels of four or five of the six b-lactams approved for use in dairy cattle, says a spokesperson from the FDA’s Center for Veterinary Medicine (CVM). To test for all six b-lactams, two or more tests must be used. However, the new test—an immunoassay called the Parallux system from Idexx, Inc.— “provides the means to detect all six of the currently used b-lactams and can also be used to identify the specific drug,” says the CVM’s Norris Alderson. Other changes approved at the NCIMS were aimed at reducing false-positive results, which can waste many gallons of milk and millions of dollars, Byrne says. For example, any new test cannot be >50% more sensitive than the regulated safety level of the targeted drug residue. In addition, milk testing protocols were changed to further reduce false-positives. Finally, he says, if a test kit is resubmitted to the FDA for evaluation because of changes in its ability to detect one drug residue, data will be examined for all drugs that the kit claims to detect. –Laura Ruth
A N A LY T I C A L C H E M I S T R Y / J U LY 1 , 2 0 0 1
vision sprang from the increasing growth of and demand for robotics in areas such as high-throughput screening, drug discovery, and combinatorial chemistry. This partnership between LRIG and the ACS is not the first. “We would have joint meetings with the ACS, and the turnout would be disappointing,” says France. “We had all but given up on the ACS because of those failed meetings.” But a renewed dedication by Les McQuire of Novartis, former chair of the North Jersey section of the ACS, and other key players—namely Mark Hayward, chair-elect of the North Jersey MS group (Novartis); Bill Suits, current chair of the North Jersey section of the ACS division; and Alan Cooper (ScheringPlough)—persuaded France and his colleagues at LRIG to give ACS another try. Hayward, who pitched the renewed partnership to Divisional Activities Committee members at the 221st ACS National Meeting in San Diego, CA, says that the merger will address unmet needs on both sides. “ACS had always had success with their national meetings but needed a way to have the same success on a local or regional level, which the LRIG could provide,” says Hayward. “By the same token, a merger with ACS gives the LRIG the ability to provide organized local service on a national plateau.” The LRIG currently has seven chapters under its umbrella: Mid-Atlantic, New England, Southeast, Bay Area, San Diego, Northwest, and European. The long-term vision for the new ACS Laboratory Automation Division is to run more productive meetings, increase member and vendor participation, and continue to provide researchers in the drug discovery/high-throughput screening market with cutting-edge instruments. “Since all of us are extremely busy scientists, we are trying to keep the infrastructure and processes simple,” says France, “because the day that it becomes cumbersome is the day that it may fall apart like a house of cards.” –Wilder Smith
