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DictionarySeeconstantsedimentation constant
sedimentation constant[‚sed·ə·mən′tā·shən ‚kän·stənt] (physical chemistry) A quantity used in studying the behavior of colloidal particles subject to forces, especially centrifugal forces; it is equal to 2 r 2(ρ-ρ′)/9η, where r is the particle's radius, ρ and ρ′ are reciprocals of partial specific volumes of particle and medium respectively, and η is the medium's viscosity. sedimentation constant
sed·i·men·ta·tion con·stantthe constant s in the Svedberg equation for estimating the molecular weight of a protein from the rate of movement in a centrifugal field:where M is the molecular weight, R the gas constant, T the absolute temperature, D the diffusion constant (in square centimeters per second), the partial specific volume of the protein, and ρ the density of the solvent. The constant s, with dimensions of time per unit of field force (s = drb/dt/ω2ro where rb is the position at time t, r0 is the position at time 0, and ω is the angular velocity) is usually between 1 × 10-13 and 200 × 10-13 s. The Svedberg unit (S) is arbitrarily set at 1 × 10-13 s and is very often used to describe the sedimentation rate of macromolecules; for example, 4S RNA. Synonym(s): sedimentation coefficientsed·i·men·ta·tion con·stant (sed'i-mĕn-tā'shŭn kon'stănt) The constants in a Svedberg equation for estimating the molecular weight of a protein from the rate of movement in a centrifugal field. The Svedberg unit (S) is arbitrarily set at 1 × 10-13 sec and is often used to describe the sedimentation rate of macromolecules (e.g., 4 S RNA).
Synonym(s): sedimentation coefficient. |