Half sphere exposure Half sphere exposure Half Sphere Exposure (HSE) is a protein solvent exposure measure that was first introduced by . Like all solvent exposure measures it measures how buried amino acid residues are in a protein. It is found by counting the number of amino acid neighbors within two half spheres of chosen radius around the amino acid. The calculation of HSE is found by dividing a contact number (CN) sphere in two halves by the plane perpendicular to the Cβ-Cα vector. This simple division of the CN sphere results in two strikingly different measures, HSE-up and HSE-down. HSE-up is defined
Sphere and is called the equation of an imaginary sphere. If formula_5 the only solution of formula_6 is the point formula_7 and the equation is said to be the equation of a point sphere. Finally, in the case formula_8, formula_6 is an equation of a sphere whose center is formula_10 and whose radius is formula_11. If in the above equation is zero then is the equation of a plane. Thus, a plane may be thought of as a sphere of infinite radius whose center is a point at infinity. The points on the sphere with radius formula_12 and center formula_13 can