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ducted by Schoenfisch, who is now at
taminants. He and graduate student
the University of North Carolina–Chapel
Huiping Zhang are working on new sili-
Hill, the sensors monitored the levels of
cone rubber materials in which the NO-
hoff suggests that the NO-release chem-
oxygen in the blood of lab animals for at
releasing agents are covalently linked to
istry may have even more widespread
patible with them. Looking ahead a little further, Meyer-
least 20 h, and the data
applications. One pos-
agreed with the expected
sibility is extracorpore-
results. “We didn’t experi-
al technology, which is
ence the large deviations
used when the blood is
from the real values in
taken outside the body,
oxygen that can occur
as in open-heart sur-
with platelet-covered sen-
gery or kidney dialysis.
sors,” Meyerhoff says. In
“There is the potential
fact, the NO-releasing
for clots, because
sensors had much less
platelets stick to the
platelet buildup than the control devices. “The goal
Schematic of (a) typical problems associated with current intravascular blood gas sensors, and (b) an implantable sensor that releases NO.
of these studies was to
walls of the tubing that carries the blood,” he explains. But even
determine if the NO-release chemistry
the polymer, so no leaching can occur.
when there is no clotting, the process
made a detectable difference in vivo,”
These materials release NO for 10 days,
consumes valuable platelets. Here
he says, “and now we have evidence
which should permit the devices to be
again, adhesion is the problem, and
that it does.”
used for longer durations. In addition,
mimicking the body’s own processes
the researchers are looking at optical
may be the solution. As Meyerhoff says,
been optimized yet, Meyerhoff notes.
sensors, as opposed to the electrochem-
“We don’t have all the evidence yet, but
One issue that needs to be addressed is
ical ones currently used, to see whether
we think we’re on the right track.”
that the NO-doped coating leached con-
the NO-release chemistry is also com-
Elizabeth Zubritsky
Nevertheless, the sensors have not
Down under in wine country Wine makers can get into a real funk each year trying to assess the quality of grapes headed for harvest. Traditionalists still walk the vineyards, picking a few berries and tasting the juices to evaluate sugar content and flavor potential. But all that’s changing in Australia, where researchers are coming up with more reliable methods to determine grape quality before harvest. At the Australian Wine Research Institute (AWRI), located on the Waite Campus of the University of Adelaide in southern Australia, new techniques are being perfected that would give wine producers “the ability to pay growers for potential quality based on a quantitative measurement rather than some historical assessment,” says Peter Hoj, the institute’s director. In addition, “Particularly good lots of grapes [could] be identified and allocated to a premium product, enhancing control over the wine-making process,” he says. One of the institute’s recent innovations is a procedure that measures the concentration of glycosides in grapes
before harvest to determine the impact they’ll have on a wine. “Our work suggests that glycosides are responsible for a significant proportion of flavor in white and red wines,” explains research scientist Leigh Francis. “So it was a likely bet that if we could quantify the total concentration of glycosides in grapes or in a young wine, it would indicate the potential quality level of the wine.” More than 3500 wine samples from vineyards throughout Australia—including chardonnay, semillion, shiraz, and cabernet sauvignon—were involved in the glycoside experiments. Buoyed by the results, Francis and his colleagues nailed down an accurate glycosyl–glucose (G–G) measurement from grapes by developing the G–G assay. During the assay, homogenized fruit extracts, juice, or wine samples pass through a C18 reverse-phase solid-phase extraction cartridge. Glycosides and other juice components, including sugars and acids, go through the cartridge and form a glycoside isolate, which is washed from the car-
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Leigh Francis of the Australian Wine Research Institute assesses wine quality the old-fashioned way.
tridge into a test tube. Sulfuric acid is added, and the test tube is heated to break down the glycosides. The researchers quantify the resulting sugar level by using conventional enzymatic spectrophotometric analysis with a commercially available kit and automated analyzer. The procedure is a little too complicated for wine makers to do themselves, and the hard-pressed institute staff has only been able to complete about 10 G–G assays a day. But help is on the way from Advanced Rapid Robotic Manufacturing, a firm near Adelaide, which is perfecting an automated system that could potentially turn out 100 assays a day. According to Francis, the fully automated system will homogenize grape samples and perform an
extraction and a centrifuging step, solid-phase extraction, and hydrolysis on 96 samples simultaneously. “We’re still building the system, and it may be another six months before it is finished,” comments Francis. As an alternative to the assay, the scientists are testing near-IR spectroscopy for determining G–G levels in grapes. If the technology can be incorporated into a relatively inexpensive, hand-held instrument, wine makers and grape growers could assess the flavor potential of fruit on the vine or at the weigh-bridge instead of waiting for costly and time-consuming reports. Aware that the glycosides have a major impact on wine flavor, researchers are now trying to zero in on the specific compounds that please the palate. For instance, betaionone, which gives some pinot noirs a powerful punch, also appears in raspberries. Is reisling a reminder of the days of wine and roses? It wouldn’t be surprising. The compounds linalool and geraniol, which are found in the reisling grape, also appear in roses. In the end, the researchers have every reason to smell the roses, Francis says. They are working on a GC/MS method, which uses deuterium-labeled analogues of the aroma compounds as internal standards, to quantify the flavor compounds on a routine, relatively rapid basis. He adds that several standards have been synthesized and that the researchers are at the point of developing standard curves and validating the analyses. “In a reasonably short time, possibly two years,” he predicts, “we will have an analytical method for the determination of key compounds derived from grapes.” Don Frederick
2-D PAGE gets competition Anyone who has separated proteins using 2-D polyacrylamide gel electrophoresis (PAGE) knows how labor-intensive and cumbersome it is. But despite rapid growth in the field of proteomics, there aren’t many other options for analyzing whole-cell protein expression. That, however, could be about to change. In the March 15 issue of Analytical Chemistry (pp 1099–1111), David Lubman and coworkers at the University of Michigan describe a new twodimensional (2-D) liquid-phase separation method capable of resolving large numbers of cellular proteins and generating quantitative maps of protein expression. In the first dimension, proteins are separated according to pI using a commercially available liquid-phase isoelectric focusing (IEF) separation device. The separation takes about 3–5 h, depending on how good you want the focusing to be, says Lubman. In the end, you are left with 20 different tubes, each containing liquid-phase protein fractions of varying pI ranges. Once the batch IEF separation is complete, a fraction of the contents from each tube is
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injected into an HPLC system for the second-dimension separation, explains Lubman. In the second dimension, proteins are separated on the basis of their hydrophobicity and molecular weight by reversed-phase HPLC. “But it’s not an ordinary reversedphase HPLC [system],” emphasizes Lubman. “It uses nonporous columns, which make all the difference,” he says. The columns are optimized for separating proteins in the 5to 70-kDa range, which is comparable with most gels and includes many of the proteins currently being analyzed as possible cancer biomarkers. The researchers have even been able to separate proteins as large as 100 kDa, says Lubman. As the proteins come off the column, they are detected by UV and collected for MS identification. To create a protein map analogous to a 2-D PAGE image, the researchers developed original software, which creates a protein pattern from the 2-D separation data. For each fraction, pI is plotted against HPLC retention time. In the image, reversed-phase HPLC peaks are repre-
