Sigma receptors are proteins found on mainly the surface of endoplasmic reticulum (ER) in certain cells. Sigma-1 and sigma-2 are the two main classes of these receptors. The sigma-1 receptor is involved neurological disorders and certain types of cancer. To understand better how the receptor is involved in disease and whether drugs developed to target it are working, it is important to be able to accurately trace the sigma-1 receptor. Researchers have now ..