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A New Tape Measure for Molecular Size

Dr. David Dearden of the Department of Chemistry and Biochemistry recently discovered a new method for describing the shape of molecules with the help of graduate student Fan Yang and the rest of Dearden’s research team.

Although mass spectrometry typically measures a molecule’s mass, as currently practiced it fails to answer critically important questions about the shapes into which molecules fold. Dearden’s new technique answers those questions by observing how the molecule interacts with a target gas. He calls it “CRAFTI,” short for “cross-sectional areas by Fourier transform ion cyclotron resonance.”

Using the strong magnetic field in a Fourier transform mass spectrometer, CRAFTI observed the collision of molecules while they orbited within the electromagnetic trap.

Since helium, which is used to measure shapes in specialized ion mobility instruments, was too light for the CRAFTI method, the researchers used xenon as the target gas. Large molecules collide more often, causing them to slow down. By analyzing the collision rates, the molecules’ sizes are measured. The CRAFTI method is very innovative in how it uses the combination of a powerful magnet and the chemical xenon instead of helium to discover molecular shape, which also shows the size of the molecule.

“It’s just not very often in science that you find something that’s really new,” Dearden said. “But this is a brand-new kind of technique.”

One of Dearden’s colleagues at UC Santa Barbara is currently using ion mobility methods to study how amyloid beta proteins fold, a process some theorize causes Alzheimer’s disease. The CRAFTI method should be applicable to these same problems without requiring a specialized instrument.

Although such applications are important to Dearden and his group, they are also motivated by basic science concepts. “If you never have the basic foundation to make the science work, then you won’t have any applications,” Dearden said.

Dearden and his team’s research leading to the CRAFTI method spans over ten years. Others in his field told him the idea would never work and encouraged Dearden to give up. Dearden was not swayed and his theory worked. Dearden’s article was published in Analytical Chemistry and his research team is currently working on several other publications regarding the CRAFTI method.

Dr. David Dearden’s publication in Analytical Chemistry is available online at dx.doi.org/10.1021/ac300379a and will shortly appear in the printed journal. Graduate student Fan Yang and Jacob Voelkel, a BYU undergraduate student at the time of writing, are both co-authors.

By Alysa Kleinman Posted on