Forgotten Molecules: The Fruits of an Emeritus Professor's 40-year Career are Contributing to the Modern Search for New Medications
On a rainy day last fall, chemist Scott Wildman left his office on the UW–Madison campus and drove to a retirement community on the city’s west side to bring 40 years of scientific work out of the dark.
His trip brought him to the home of Laurens “Andy” Anderson, emeritus professor of biochemistry. There, packed away in a closet, Wildman found a cache of dark green boxes holding nearly 800 meticulously organized vials of purified chemicals, each one stoppered with real cork and labeled with intricate handwriting. Many of the vials boasted a tiny drawing of a structural chemical formula for identifying the white or sometimes colored powders inside. Wildman wrapped the glass treasures in protective plastic and chaperoned them to their new home — and new purpose — at the UW Carbone Cancer Center’s Drug Development Core (DCC).
The so-called “green box collection” contains the physical legacy of Anderson’s career with the Department of Biochemistry. While cleaning his house one day, it occurred to him that the molecules could be useful for carbohydrate chemistry researchers, so he approached the department about donating the collection. In the end, it was decided they would have the biggest impact at the DDC, where they can serve as a resource for the next generation of scientists looking to discover new drugs for treating diseases.
In the complicated process of drug discovery, scientists screen large collections of molecules — called libraries — in search of a range of properties that indicate they could be used as antibiotic, antifungal, or anticancer agents, or even neurological drugs. A molecule with one or more of these properties is called a “hit” and can be further investigated as a possible drug. A hit gives researchers an important starting point for deeper research in drug design. But when compared to the types of molecules synthesized for drug discovery today, the old-school way in which Anderson’s molecules were made gives them some unique properties, so they are taking on new significance in their present home.
“Learning about him and what he did while he was here 20 years before I was born has been very interesting, especially because I am now one of the keepers of the fruits of that labor,” says Wildman, who is an associate scientist at the DDC. “As scientists, we have a finite period of time in which to make an impact. But in this case, we just gave his impact a whole new lease on life. In a way, he can start over, even without being in the lab.”
The Making of the 800
Anderson, now 98, was born in South Dakota, and he earned his undergraduate degree from the University of Wyoming in 1942. After college, he joined the Air Force and served as a bomber pilot in missions over southern Europe. In 1946, he began his graduate studies in biochemistry at UW–Madison, where he worked with esteemed biochemist Henry Lardy, an expert in metabolism and sugars. After earning his Ph.D., and following a yearlong postdoctoral position in Switzerland, Anderson returned to UW–Madison to join the biochemistry faculty.
One of Anderson’s first major scientific contributions was determining the molecular structure of several cyclitols, which are a group of compounds closely related to sugars. Around the time Anderson joined the UW faculty, antibiotics were just starting to see widespread clinical use. The second one to be introduced, streptomycin, included a cyclitol in its chemical structure.
“And so I began thinking about how to synthesize analogues of streptomycin,” Anderson says. “I thought, ‘Well, if I could change the cyclitol part and put more sugars on it, maybe I’d have an antibiotic.’”
Although Anderson’s work did not lead to a new antibiotic (at least, not yet), it did start him down the path of completing complicated organic syntheses of sugars. He began reading about the importance of sugar molecules on the surface of cells and how they contribute to crucial functions such as cell-to-cell communication and immunity. These cell-surface sugar molecules are oligosaccharides, or combinations of a few individual sugars into a larger, multi-unit sugar. Anderson expected he could use his organic chemistry expertise to synthesize a variety of oligosaccharides with potential biological applications.
The problem is that the chemistry of making substitutions in sugars is extraordinarily complex. Unlike the other “big player” molecules in biochemistry (DNA, RNA, and proteins), sugars have multiple chemically reactive parts to them, any of which is difficult to differentiate. With specific end products in mind, Anderson realized he needed to selectively block certain reactive parts in order to synthesize the intended product.
“The result, then, is that I’ve spent a great deal of effort on thinking how to attach protecting groups to the reactive groups of the sugar molecules,” says Anderson, who retired from the biochemistry department in 1986. “This turned out not to be the best strategy for making oligosaccharides.”
It did, however, turn out to be a strategy that yielded more than 800 cyclitol and sugar derivatives, most of which are the intermediates to becoming the desired end product. Along the way, Anderson and his research group purified each of the derivatives and meticulously documented and saved them, which led to the green box collection.
Each purified chemical in the “green box collection” is contained in a vial, which in turn is housed in a larger glass tube and sealed with a cork stopper. The number and letter combination on the outside denotes the location of the tube in the collection. Photo by Robin Davies.
A Legacy of Scientific Rigor
The diligent labeling and organizing of his sugar collection reflects Anderson’s approach to all of science, explains biochemistry professor John Ralph. Ralph, also a researcher with the Great Lakes Bioenergy Research Center based at the Wisconsin Energy Institute, collaborated with Anderson in the 1990s and 2000s.
Ralph describes Anderson as extremely rigorous in his scientific work, particularly when it comes to naming carbohydrates. A system for naming scientific compounds is extremely important; proper nomenclature allows scientists from around the world to understand one another’s work. Ideally, carbohydrates are named based on their structure so that a scientist can tell the exact structure from the name. There was no good system for naming new carbohydrates until Anderson changed the field. His naming rules are still in use today.
Anderson working in his lab during his tenure in the department. Photo from
Department of Biochemistry archives.
“He is really a world authority on carbohydrate nomenclature and helped devise many of the rules during his career,” Ralph says. “His interest and expertise in the fine details advanced the field immensely. He was also an editor at the Journal of Carbohydrate Research for a long period and ensured everything that went in that journal was absolutely correct. He never minded being contacted, and we’d run new compounds by him to make sure they were accurately named. He was always happy to lend his expertise without a hint of arrogance or condescension.”
Anderson and Ralph worked on two papers together when Anderson was still mentoring some young scientists in his retirement. One paper dealt with the cross-linking of plant cell walls and required Anderson’s selective protection strategies; and the other, which was a particularly successful paper, was about a popular dietary supplement called psyllium. Anderson was working with collaborators in the Department of Food Science to investigate a specific polysaccharide in psyllium thought to be responsible for lowering cholesterol. Ralph was invited onboard to use a technique called nuclear magnetic resonance (NMR) spectroscopy to determine the structure of the complex polysaccharide.
“We made a big advance in that paper, and it actually got a top citation award in 2007,” Ralph says. “It’s also an example of how Andy always wanted to stay relevant. He had an interest in being meticulous in his synthesis and nomenclature but also saw the big picture and the impact his work could have in an area like health and cholesterol lowering.”
Ralph’s current research focuses on lignin, a chemical polymer that binds plant fibers together and makes stems hard, durable, and difficult to break down. His lab is investigating how lignin can be engineered so it’s easier to break down plant biomass for purposes such as biofuel. Although his current work focuses outside the field of carbohydrate chemistry, Ralph says Anderson’s rigorous scientific approach still inspires him today.
“In the lignin literature, there can be a lot of discrepancies in the structures presented, but we try to ensure we are always correct,” Ralph says. “It’s important for us because, when you don’t make those silly mistakes, we become known as experts, and now people know they can come to us for advice. That is something I attribute in large measure to Andy.”
Ralph adds that Anderson’s collection of molecules will have great value for a long time because not many people are still doing the same kind of difficult synthesis. “Andy is one of those wonderful human beings and an unbelievably good mentor to many people,” he says. “A collection like this one he’s donated is just invaluable.”
A New Purpose: Drug Screens
Jennifer Golden, associate director of the DDC’s Medicinal Chemistry Center, knows that there are many unique chemical collections from UW’s scientific past. Which is why her center reaches out to local investigators who have synthesized novel molecules and helps funnel their compounds into diverse biological screens.
“Academic careers have been built on training students to construct structurally unique molecules,” says Golden, who is also an assistant professor in the School of Pharmacy. “Once synthesized, these agents can often end up in a freezer vial, never to see the light of day. There is a second life for some of these compounds, which may harbor untapped biological relevance. We want to harvest these potential gems from the freezer — or the closet, in the case of Andy’s collection.”
Wildman, the DDC chemist who procured the green box collection, is now working with his team to confirm the chemical structure of each molecule and enter it into the database. When the process is complete, Anderson’s sugar molecules will be ready to screen, along with the hundreds of thousands of other molecules available at the DDC.
To reap the benefits of these molecules, scientists can incorporate them into their current experiments. The DDC works with researchers to screen the molecules and narrow the search for compounds that can be developed into new drugs. James Keck, professor of biomolecular chemistry in the UW School of Medicine and Public Health (SMPH), is using this screening process to look for possible new antibiotics.
“Essentially, these experiments are like huge sieves,” explains Keck, who is also the SMPH’s associate dean for basic sciences. “You start out with this giant library of roughly half a million compounds they have at the screening facility, where Andy’s will soon be included, and you devise a way of rapidly going through and checking each compound individually to see if any appear to do what you want.”
Using different methods, the screens continue to narrow the pool of molecules finer and finer. From half a million, to fifty thousand, to maybe 500, and then finally a number that individuals in a lab can actually work with. Keck’s search for possible antibiotics just finished its first screen.
Keck’s lab studies protein complexes that are uniquely found in bacteria, not humans, and that are essential for the bacteria to survive. If they can find a chemical that binds to one of those protein complexes and then stops an essential process, they’ve got a potential drug to investigate.
“You’re sorting the wheat from the chaff, and each step in the process is a screen that gets rid of more of the chaff,” he says. “Then, the small number of molecules we end up with almost certainly aren’t the drugs one could use. They must undergo further research after that.”
Old Molecules Meet New
This efficient screening of candidate drugs is not a new innovation. It was picked up in earnest by pharmaceutical companies in the 1990s. And the number of molecules in the green box collection, synthesized by fairly conventional methods, pales in comparison to the hundreds of thousands of molecules now available through commercial libraries. The significance of Anderson’s molecules lies in their uniqueness, complexity, and close relationship to molecules that occur naturally.
Back when Wildman worked for a pharmaceutical company as a drug library designer, he says he made them as simple as possible. The reasoning was twofold. One, each step requires purification that can be laborious, so the fewer the steps, the less purification. Two, researchers thought drugs should not be so chemically complex that they react with everything — they should only react with the intended target.
After his retirement in 1986, Anderson couldn’t stay away from
science. He became a visiting scientist in the UW Department of
Chemistry, where he was involved in science outreach and work with
undergraduates. Photo from Department of Biochemistry archives.
“From a development standpoint, structural simplicity offers many advantages,” Golden says. “However, it is more widely appreciated now that surveying compounds that are architecturally differentiated from those in commercial libraries is likely to offer new opportunities in drug discovery. We need structural diversity, and an academic environment is uniquely suited to deliver on that front.”
Golden is principal investigator on a recently awarded UW2020 grant that seeks to make spatially complex molecules like Anderson’s, but to do so with biological significance and drug-likeness in mind. Once completed, the UW2020 library, like Anderson’s, will be a resource for the entire UW community.
With the donation of Anderson’s collection, the science is coming full circle. Anderson’s storied career, which includes earning the American Chemical Society’s prestigious Hudson Award for Carbohydrate Chemistry in 1984, can now carry on even though he’s no longer in the lab.
Today’s researchers are happy to include his molecules in their libraries and develop new methods to make libraries with the same chemical diversity, albeit much faster thanks to modern technology. Among the hundreds of thousands of molecules in these screens, the researchers say these 800 will always stick out for their uniqueness and fascinating connection to UW–Madison.
“An enormous amount of man and woman hours went into these things, and I had a policy from the beginning that if we made some kind of intermediate we would save a little bit and put it in a vial and label it,” Anderson says. “That’s how we ended up with those green boxes. I’m glad they are back at UW–Madison.”
Story by Kaine Korzekwa and Sarah Perdue for the College of Agricultural and Life Sciences' Grow Magazine. See the original here.