Archive for Saturday, August 17, 1991


August 17, 1991


Daryle Busch, Kansas University chemistry professor, refers to himself as the "father of macrocycles," but one might also think of him as Lord of the Rings.

That's because macrocycles are complex molecules with a large ring structure. And like the Lord of the Rings in J.R.R. Tolkien's trilogy, a person who knows how to use such rings can work wonders.

The applications of macrocyclic chemistry range from creating paper for making carbonless copies to fabricating oxygen carriers such as the ones found in human blood.

Busch said the origin of macrocycles dates back to 1952 when he was a doctoral student at the University of Illinois. One day, someone was discussing a complex compound in which a metal ion was only three-fourths encircled by "ligands," or "things that bind to."

"The fourth side was open, and that was offensive to me," Busch said. "It seemed to me that the structure should be complete. It just needed another chain to bind the ring, and rings are perfect."

BUSCH ASKED his professor if such ring structures had been created, and his professor responded, "No. Why don't you make it?"

Busch accepted the challenge. However, it wasn't until seven years later, when Busch was a professor at Ohio State University, that he accomplished his goal.

"That was the first-delivered synthesis of what we call macrocycles, or macrocyclic ligands," Busch said. "We had to invent some new chemistry in order to do it."

Macrocycles today play an important role in the area of supramolecular chemistry. Coined by 1987 Nobel Prize-winner Jean-Marie Lehn, supramolecular chemistry represents "chemistry beyond the molecule," Busch said.

"It really represents a field where different molecular species interact," Busch said. "You get into questions about how one molecule recognizes another, how they might combine and what determines how strongly they bind."

MOLECULES BIND very strongly when they bind into macrocycles; hence their importance in supramolecular chemistry.

Busch said macrocycles occur naturally in living systems. Chlorophyll is a macrocycle, as is the hemoglobin that carries oxygen in the blood. Using macrocyclic chemistry, the first synthetic oxygen carriers were developed around 1980, Busch said.

Considering the possible applications of macrocyclic chemistry to health sciences, Busch said it is important to have interdisciplinary cooperation among chemists and other researchers. He said he sees such cooperation at KU, where divisions such as pharmaceutical chemistry and biological chemistry can be found under one roof in Malott Hall.

"It's an interface between two fields," Busch said. "Everyone is constrained by their background. None of us knows enough to do everything we want to do. You can work with people across that border and do better things."

Busch came to KU in 1988 after a long tenure at Ohio State University.

"The ambience of this campus, and certainly of Malott, and even more clearly of the chemistry department, is just super for scientists," Busch said. "It doesn't have a lot of the taints and discomforts that are built into some other organizations."

Busch said he had been impressed by the KU chemistry department since 1952, when he met several KU professors during a national chemistry conference in Kansas City. He said that's one reason he came to KU.

WITH HIM came five graduate researchers and six post-doctoral researchers. He also brought funding from the National Institutes of Health and the National Science Foundation. Busch has received continual funding from both of those sources for the last 30 years, and on a competitive basis.

Busch also has received considerable backing from the private sector, and he now is wrapping up a project for 3M. The project involves "carbonless copies," which people commonly see in the form of receipts from service stations.

Busch said 3M officials said they were interested in changing their carbonless copy pigment because "our customers want black, but we've got purple."

They called on Busch because he works in the area of chemistry that figures in the production of carbonless paper. On the back of the top page are microcapsules containing a solution, and covering the bottom page is a layer of nickel salts.

"WHEN YOU press down on the ball point it breaks the capsules, they go onto the other sheet, the reaction occurs and develops the pigment," Busch said.

He and his researchers have managed to create a black pigment for 3M, as well as a blue pigment.

Busch also is working to produce new pharmaceuticals that can combat the inflammation that usually occurs in the area of a wound or injury. And once that project's finished, Busch knows he'll have plenty more to do, and plenty more to discover.

"You can't expect the cutting edge of a field to remain the same," Busch said. "The material I use in my work today, I'd say 5 percent of it was known when I started.

"You don't know what you're going to be working on a few weeks or a few months down the road, and that's exciting."

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