Wednesday, October 1, 2014

Using magnets to find new drugs: Inside UAB's high-field nuclear magnetic resonance facility

Most high-end lab equipment is inaccessible to the public eye, but one of UAB's most powerful drug-discovery tools is clearly visible from the Campus Green. The Central Alabama High Field Nuclear Magnetic Resonance Facility occupies a gleaming ground-floor space in the Chemistry Building. Its massive magnets give researchers invaluable insight into disease-causing proteins — and the data they need to find new ways to stop them.

UAB Magazine Fall 2014 cover
The cover story of the latest issue of UAB Magazine features the Alabama Drug Discovery Alliance, a partnership between UAB and Southern Research Institute that aims to accelerate high-potential discoveries from the lab to patient-ready treatments. One key tool in that process is the Central Alabama High Field Nuclear Magnetic Resonance Facility, which opened in 2013. The Mix takes a closer look in this new feature.

Spin This Way

Each of the facility's NMR machines specializes in a different type of job, but the basic functioning is the same, explains NMR director N. Rama Krishna, Ph.D., UAB professor in the Department of Biochemistry and Molecular Genetics. The machines generate strong magnetic fields that polarize the tiny magnets in the nuclei of hydrogen atoms. “Then, using radiofrequency pulses, you can count all of the individual hydrogen atoms in a sample, which tells you what amino acids are present and how they are arranged in space,” Krishna says. And that’s precisely the information you need to create a detailed picture of a protein’s structure.

Mapping a protein's structure is crucial to understanding its function — and to finding ways to alter that function to treat disease. For instance, locating suitable "binding pockets" on a protein linked to brain cancer tells medicinal chemists how to design a drug to block (or enhance) that protein. "That's why NMR is one of the most versatile tools for drug-discovery research," Krishna says.

The bigger your magnet, the better images you can get. The centerpiece of the NMR facility is an 850 MHz Bruker BioSpin model, one of the largest in the South, which allows scientists to analyze structural data on even the largest proteins.

(Story continues after graphic)

Building a Better Drug

The 850 MHz machine can also accelerate the drug-discovery process "by allowing researchers to rapidly test new compounds they've developed in the lab," Krishna adds. Using a technique called saturation transfer difference NMR (STD-NMR), Krishna and his team can register the minute changes in signals from hydrogen atoms that occur when a compound binds to a protein. It would be nearly impossible to capture this interaction directly, he points out, because "it may last only a few microseconds." With STD-NMR, researchers can screen a number of potential drugs at once, then focus on the ones that show signs of binding to the target protein.
UAB's Rama Krishna and scientists from Southern Research
Institute have collaborated in developing a novel high-field
NMR-based protocol for determining the binding of
allosteric ligands to target proteins. They used the kinesin-5
protein Eg5 (a cancer target) and its inhibitor monastrol
 as an example (see above) for this protocol.

Using other techniques, researchers can analyze the disease-causing interaction between two proteins, and then find the right location to dock an inhibitor that would prevent the proteins from coming together. Or they could do the opposite, in an approach dubbed “fragment-based discovery” — using NMR data to identify two compounds that bind close together on a protein and “cross link” them to significantly improve their binding.

Krishna uses these techniques in his own National Cancer Institute-funded research to find new treatments for pancreatic cancer. Other UAB investigators are using the NMR facility to further their drug-discovery efforts in Parkinson's disease, brain tumors, breast cancer, heart disease, HIV and more. And as word of these capabilities has spread, researchers at institutions across the South have begun sending in samples to the NMR facility for evaluation.

Early Warning Signs

NMR is useful for many applications beyond drug discovery, Krishna adds. The facility's 600 MHz machine specializes in a hot area of medicine known as metabolomics, which studies the way the body processes everything from food to medicines.

"If you are taking a drug that is toxic to the liver, the body will generate some small molecules — known as metabolites — associated with liver damage,” Krishna explains. "We can detect these molecules in the NMR spectra of biofluids such as urine and blood plasma and say, 'Aha, after this patient started taking the drug, we can see an increase in these signals, so something is going wrong." That can warn researchers of side effects from new drug treatments "long before there is any major problem," Krishna says.

"The range of applications in this facility is amazing," adds Krishna. "It is a unique platform for everything from basic science to translational research.”

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