Hill equation


Hill e·qua·tion

(hil), the equation y(1 - y) = [S]n/Kd, where y is the fractional degree of saturation, [S] is the binding ligand concentration, n is the Hill coefficient, and Kd is the dissociation constant for the ligand. The Hill coefficient is a measure of the cooperativity of the protein: the larger the value, the higher the degree of cooperativity. This coefficient cannot be higher than the number of binding sites. For the oxygen binding curve of hemoglobin, an association constant, Ka, is used and the equation becomes y/(1 - y) = Ka[S]n. For human hemoglobin A, n = 2.5. Compare: Hill plot. [Archibald V. Hill]

Hill e·qua·tion

(hil ĕ-kwā'zhŭn) The equation y(1 - y) = [S]n/Kd, where y is the fractional degree of saturation, [S] is the binding ligand concentration, n is the Hill coefficient, and Kd is the dissociation constant for the ligand. The Hill coefficient is a measure of the cooperativity of the protein; the larger the value, the higher the cooperativity. This coefficient cannot be higher than the number of binding sites. For the oxygen binding curve of hemoglobin, an association constant, Ka, is used and the equation becomes y/(1 - y) = Ka[S]n. For human hemoglobin, n = 2.5. [Archibald V. Hill]

Hill,

Archibald V., English biophysicist and Nobel laureate, 1886-1977. Hill equation - used to express the fractional saturation of a molecule with a ligand as a function of ligand concentration.Hill plot - a graphical representation of enzyme kinetic data or of binding phenomena to assess the degree of cooperativity of a system.