Researchers from Cornell University were able to produce an image of P2X7 for the first time. P2X7 is a receptor associated with chronic pain.

The visualization of the receptor's shape has led the team to another breakthrough. They found that five of the painkiller molecules they tested did not bind the receptor at the place where it was expected to bind with. This may explain why these painkillers lack efficacy in human patients.

Their study was published in the journal "eLife." It laid the foundations to create targeted and effective molecules to manage chronic pain.

In its official website, Cornell reported that chronic pain affects 10 percent of the adult population. It is said to come with other conditions such as rheumatoid arthritis and migraine, where pain management is important in patient care.

One major problem, though, is that chronic pain does not always respond to current analgesic drugs. Scientists have limited knowledge about pain, thus resulting to the lack of effective medicines.

Researchers at Cornell University have examined a receptor named P2X7, which binds a molecule called ATP. Many drugs that target this particular receptor work by competing for space with the ATP molecule.

They do this by occupying the groove at the surface of P2X7, where ATP would naturally bind. Scientists believed that preventing ATP from binding to the receptor should be enough to block the pain signal.

Research done on animal models demonstrated positive results but clinical trials in humans were not as effective. The team, led by assistant professor in the College of Veterinary Medicine's Department of Molecular Medicine Toshimitsu Kawate, investigated this by visualizing the shape of the receptor.

Kawate said that they were shocked to discover that the drugs did not bind in the right places. They used X-ray crystallography at the Cornell High Energy Synchrotron Source (CHESS) to create an image of the receptor at a resolution of 3.5 angstroms.

They found that the receptor functions as a normal pore but sometimes converts into a big pore. This allows molecules of up to 900 dalton, a unit used to quantify mass at atomic levels, to pass through the membrane.