Nashville, TN and Jupiter, FL--A backscattering interferometry (BSI) technique being developed by scientists at Vanderbilt University and the Scripps Research Institute can measure interactions between proteins in a cell's membrane and their ligands. The technique will aid the process of drug discovery. (This BSI technique differs from optical coherence tomography, which is a more-complex form of backscattering interferometry.)
The researchers report that BSI can precisely measure the binding force between membrane proteins and both large and small molecules in a natural environment. BSI measures the binding force between two molecules mixed in a microscopic liquid-filled chamber using red laser light. The resulting interference pattern is very sensitive to what the molecules are doing: if the molecules begin sticking together, for example, the pattern begins to shift. The setup, which is simple and low in cost, can measure the protein/ligand interactions at picomolar concentrations.
Testing on synthetic and natural membranes
The researchers created synthetic membranes that contained a small protein, called GM1, which is a primary target that cholera toxins bind with in order to get into a cell. When they mixed these membranes with cholera toxin B, they measured a binding force consistent with that obtained by other methods.
Similar validation tests were performed with naturally derived membranes and three membrane proteins, one associated with breast cancer, another associated with pain and inflammation, and the neurotransmitter GABA, which is known to aid in relaxation and sleep and to regulate anxiety.
Scientists estimate that about 30% of the 7,000 proteins in a human cell reside in the cell's membrane, and that these membrane proteins initiate 60% to 70% of the signals that control the operation of the cell's molecular machinery. As a result, about half of the drugs currently on the market target membrane proteins. Most existing assay methods require that the membrane be removed from its natural environment or modified in a variety of different ways, such as attaching fluorescent labels, to analyze membrane protein activity.
"In addition to being expensive and time-consuming, these modifications can affect the target membrane's function in unpredictable ways," said Darryl Bornhop, a professor at Vanderbilt, who developed the new technique. Vanderbilt has applied for and received three patents on the process and has several other patents pending.
The university has issued an exclusive license to develop the technology to Molecular Sensing (Montara, CA). Bornhop is one of the founders of the start-up and serves as its chief scientist.
REFERENCE:
1. Michael M. Baksh et al., Nature Biotechnology, published online 13 March 2011; doi:10.1038/nbt.1790.
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