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Flagship Instrument Joins Chemistry Department

by Gail Taylor

Photo: Manish Mehta stands by the new NMR spectrometerDECEMBER 5, 2001--A new 600-megahertz nuclear magnetic resonance (NMR) spectrometer will put Oberlin's chemistry research facilities at the head of the pack among similarly-ranked colleges and allow students to use an existing 200 MHz spectrometer as part of their earliest experiences in college chemistry, says Manish Mehta, assistant professor of chemistry.

Mehta, and his colleagues Martin Ackermann, Albert Matlin, and Michael Nee, recently secured a $252,000 grant from the National Science Foundation for the purchase of the new equipment. The college and the chemistry department provided matching funds to make the purchase of the new instrument possible. The installation of the instrument is expected to be complete by the end of this year.

The NMR spectrometer, Mehta says, is the workhorse of any chemistry department, allowing researchers to study the composition and structure of organic compounds without destroying the sample, as older methods of chemical analysis require. Space for the new spectrometer--with its requirement of 12 feet of ceiling clearance and a large magnetic field that must be isolated from such disturbances as floor vibrations--was included in Payette Associates' design for the college's new science center, where the new spectrometer is housed.

The phenomenon of NMR spectroscopy, says Mehta, is dependent on the magnetic property of certain atomic nuclei. These nuclei behave like tiny magnets, responding like a compass needle to external magnetic force. Importantly, the kinds of atoms that have this property--certain isotopes of hydrogen, carbon, and nitrogen among them--are essential components of biological molecules.

In NMR spectroscopy, a compound is placed inside a tubular opening, or bore, within a powerful magnet. The force of the magnet causes the nuclei under study to line up in a particular way. When a nucleus is so aligned, an electromagnetic pulse (similar to a radio wave) of a specific frequency will cause it to jump out of position and then realign. The frequency at which a nucleus responds reflects both its identity and its chemical environment (the compound of which it is part.) Each kind of molecule will produce a different pattern of frequency responses (its "fingerprint" as Mehta puts it), so an analysis of these responses provides a map of a compound's atomic makeup.

The more complex the compound under study, Mehta says, the more precise an instrument is needed to study its components, since the molecules respond with numerous and sometimes hard-to-distinguish frequencies. Oberlin's new 600-MHz instrument, superceding a 200 MHz instrument bought in 1986, will provide such power. The new instrument also will be an asset for recruiting new faculty members in the future.

With the arrival of the new spectrometer, Mehta says, the existing 200 MHz machine will be available for greater use by general and organic chemistry students, while advanced students and faculty researchers put the bigger instrument to work. NMR is essential to modern chemistry, Mehta says, so students learn about it right away. Currently, however, Chemistry 101 students see only printouts of the machinery's readings. (Chemists' shorthand term for such a reading is "a spectrum.") Now students will be able to use the machine to produce spectra of their own.

Mehta's own research funding includes a grant to study the protein molecules within cell membranes that cause cells to stick to their surroundings. Using the new spectrometer, such proteins can be studied in vitro, transplanted into an artificial cell membrane in which they act much as they do in their natural state.

"The advantage is clear," Mehta says. "You don't have to tear a thing apart to see inside it. "

High-ranked liberal arts colleges nationwide are now updating their NMR equipment, Mehta says, but most are acquiring 400-MHz instruments. Oberlin's new 600-MHz machine, he says, "will be the flagship instrument in our department. It will keep us ahead of the pack for many years to come."

Photo: Manish Mehta stands by the spectrometer's electrical "brains"

Mehta (right) with Earl Emery (left), an applications scientist at TecMag Inc. Pictured is the 600 MHz electronic console, manufactured by TecMag.





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