NEWS OF THE WEEK SPECTROSCOPY
MULTIDIMENSIONAL NMR PICKS UP SPEED New technique is orders of magnitude faster than conventional methods
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INCE THE DEVELOPMENT
of multidimensional nuclear magnetic resonance (NMR) spectroscopy some three decades ago, spectroscopists have hoped to obtain multidimensional spectra more rapidly Now, chemistry professor Lucio Frydman and coworkers at Weizmann Institute of Science, Rehovot, Israel, have devised ultrafast multidimensional NMR, a technique that can shorten by orders of magnitude the time required for multidimensional experiments [Proc. Natl. Acad. Sci. USA, 99, 15858(2002)}. The method obtains a complete multidimensional N M R spectrum in a single scan instead of the large numbers currently required, and it can be carried out with conventional N M R hardware and techniques. Ultrafast multidimensional N M R could aid studies of chemical structure and dynamics and could be useful in combinatorial chemistry, where large numbers of compounds need to be analyzed rapidly It might also make CHAPTER
it possible, Frydman says, "to record N M R movies of dynamic systems—such as proteins folding and in vivo metabolism." Multidimensional N M R measures the chemical environments of atomic nuclei—as does onedimensional NMR—but it also establishes spatial and/or bond correlations among nuclei. And it generally provides higher resolution than 1-D NMR. "These gains, however, are achieved at the expense of collecting hundreds or thousands of individual scans, where the timing parameters that define the N M R pulse sequence are systematically incremented," Frydman notes. Therefore, 2-D N M R experiments take minutes or hours, and 3-D procedures take hours or days, whereas a 1-D scan takes just a fraction of a second. Frydman's group has now reduced multidimensional experiments to 1-D duration by acquiring each multidimensional spectrum in a single scan. Magnetic field gradients partition a sample into slices and ascribe to
each slice the role inH shlft dividual scans play in - PPm \ a conventional multi• i't dimensional experi2 ment. This yields im.'• ,/ provements of one to i t three orders of magU' / . " nitude in overall acquisition time. 6 "It's an ingenious i and conceptually nov8 Conventional el idea," says N I H biophysical chemist Ad 6 * 2 8 1 Bax. "But I suspect H shift, ppm that its practical im1 H shift ppm pact may be somewhat limited by its to inherently low sensitivity—which appears 2rather fundamental, as Frydman and co»f U workers point out in their paper—and by 6 technical limitations \' on what resolution 8 ~\ Single scan one can obtain in practice—which is not a 8 6 4 2 fundamental prob1 H shift, ppm lem, but a limitation of today's hardware. ULTRAFAST Acquisition There are lots of cases time for ultrafast 2-D NMR where one has 'sensispectrum (bottom) is about tivity to burn,' and 0.15 second, whereas that for that's where I expect conventional 2-D spectrum is the technique is going about 90 minutes. to be particularly useful, but it probably will not help out in cases where signal-to-noise is a limiting factor—as is commonly the case in protein NMR."-STU BORMAN
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Dow Corning Closer To Emerging From Bankruptcy federal district court judge has affirmed her two-yearold ruling that women with silicone gel breast implants cannot recover damages from Dow Chemical and Corning, parents of implant maker Dow Corning. The ruling means Dow Corning could emerge from bankruptcy in 2003. The three companies consider the release key to a 1998 plan worked out between implant recipients and the silicones maker. In 1999, a bankruptcy court judge approved the plan but excluded the no-sue provision. Subsequent appeals have kept Dow Corning under supervision, thus delaying payments of $3.2 billion to claimants and $1.3 billion to creditors. The 6th U.S. Circuit Court of Appeals in Cincinnati still has to
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approve the district court judge's ruling. And the appeals court is likely to consider objections from plaintiffs who insist they should be allowed to recover damages from Dow Coming's parents. According to documents filed with the Securities & Exchange Commission, many plaintiffs would like to recover damages from Dow Coming's owners. Corning faces about 70 implantrelated lawsuits while Dow Chemical is named in 10,000 suits. A Dow Corning spokesman acknowledges the likelihood that the plaintiffs' attorneys will ask for a hearing by the appeals court. Depending on which way that court goes, Dow Corning or plaintiff attorneys are then likely to take the ruling to the U.S. Supreme Court.-MARC REI5CH
C&EN
/ DECEMBER
23, 2002
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