Alzheimer’s disease is the sixth leading cause of death in the United States. It causes patients to slowly lose memories and intellectual function. Scientists believe this loss is due to the aggregation of a substance called amyloid beta in the brain, which interferes with neurons’ ability to receive and generate energy, get rid of waste and communicate with each other.
Phillip Turner, a doctoral student in the department of chemical engineering working with assistant professor Shannon Servoss, is familiar with the devastation caused by Alzheimers. “My family has had cases of Alzheimer’s on both sides,” he explained.
Phillip is conducting research on peptoids, molecules that mimic proteins and are synthesized in a lab. These chains, which Phillip designs to stand up to the harsh environment of the brain, could inhibit the formation of amyloid beta plaques or break up the plaques once they are formed.
Stringing together atoms and molecules to create peptoids is a complicated process, involving patience, diligence, and several pieces of specialized equipment.
Step 1: Put together the building blocks.
Phillip’s peptoids are composed of a backbone composed of oxygen and nitrogen atoms and side chains, which he attaches using resin. Using a machine called an ABI 4300 automated peptide synthesizer, Phillips creates peptoids that he and other researchers design, typically putting 8-12 side chains onto a backbone.
The synthesizer Phillip uses to create peptoids.
Step 2: Separate the peptoid from the resin
The synthesizer produces a sandy substance—a mixture of peptoids and the resin that glues them together.
In order to put the building blocks of the peptoids together, the synthesizer uses tiny pieces of resin. Phillip must use an acidic solution to remove the resin from the peptoid sample, but this is a tricky process—if he leaves the sample in the acid for longer than a couple of minutes, the side chains will break off. A machine called a rotary evaporator removes the chemicals from the sample so that it can be purified.
This machine removes acidic chemicals from the peptoid sample
Step 3: Purify the peptoid sample
This machine purifies the peptoid sample and uses chromatography to verify that the sample is pure.
To purify the sample, Phillip uses a reversed-phase high pressure liquid chromatography machine. This machine separates the pure peptoid chains from impurities, and uses a detector to verify that the sample is pure. The reverse phase HPLC produces a mixture of peptoids and a solvent, so Phillips uses a machine called a lyophilizer, which freeze-dries the peptoid sample, producing a fine powder.
Pure peptoids make a dry, powdered sugar-like substance that can be stored for up to year.
Step 4: Confirm the purity of the peptoid
An ananlytical reversed-phase uses chromatography to verify the purity of the peptoid samples.
Although the first reverse-phase HPLC can tell Phillips that his sample is pure, he double checks these results using more chromatography. By performing chromotogarphy on a smaller scale using an analytical reversed-phase HPLC, Phillip can if the
peptoids have the correct molecular structure. In addition, he uses mass spectroscopy to make sure they have the correct mass.
Phillip checks the results. The peaks on the graph tell him whether his peptoids have the expected molecular mass.
Step 5: Put the peptoid and the amyloid beta together and see what happens
A tiny test tube containing amyloid beta, the substance thought to cause Alzheimer’s disease.
Synthesizing and testing peptoids is just the first step in a long process of creating and testing an effective treatment for Alzheimer’s. “Even though it may not cure Alzheimer’s next week,” said Phillip, “our research can give insight toward the future.” And so far, the future looks good. Preliminary results indicate that the peptoid designed by Phillips and the other researchers does indeed block the formation of amyloid beta aggregates.
- Phillip Turner and Shannon Servoss are collaborating with Melissa Moss at the University of South Carolina on this project.
- Acknowledgements for work around the University of Arkansas include Dr. TKS Kumar’s lab, Statewide Mass Spectroscopy Facility, and Dr. Bob Beitle’s lab.
- Funding come from University of Arkansas Start-up Funds, National Center for Research Resources (NIH) Grant # 1P30RR031154-02, and Arkansas Bioscience Institute.