Figure 1: Half sphere exposure. The half sphere exposure (HSE) is a measure of the degree of surface exposure of an amino acid on a protein. It counts the number of C∝ neighbours within a half sphere of a given radius. The fewer the number of C∝ neighbours the more exposed an amino acid is. The dotted line represents the position of the plane that divides the sphere with a central C∝ atom and radius ‘R’. The thick black lines represent part of the C∝ backbone of the protein. Adapted from Hamelryck [35].