image: This image shows dose-response curves. A typical dose-response curve is shown in blue. The IC50 is the dose that leads to 50% of the maximal response; for both curves, the IC50 is 1. Each curve has a different slope m, which is also known as the Hill coefficient. For the blue curve, m = 1, whereas the red curve has a steeper slope of m = 4. In other words, the higher the Hill coefficient, the steeper the curve, and the more potent the drug at small increases in concentration above the IC50. Curves with m > 1 usually arise from cooperative interactions. This image is Figure 1 from the related Perspective by Perelson et al. This image relates to a paper that appeared in the July 13, 2011, issue of Science Translational Medicine, published by AAAS. The paper, by Dr. L. Shen of Johns Hopkins University School of Medicine in Baltimore, Md., and colleagues, was titled, "Critical Subset Model Provides a Conceptual Basis for the High Antiviral Activity of Major HIV Drugs." view more
Credit: C. Bickel/Science © 2011 AAAS