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Historically a cesium chloride (CsCl) solution was often used, but more commonly used density gradients are sucrose or Percoll.This application requires a solution with high density and yet relatively low viscosity, and CsCl suits it because of its high solubility in water, high density owing to the large mass of Cs, as well as low viscosity and high stability of CsCl solutions.
Differential centrifugation, on the other hand, does not utilize a density gradient, and the centrifugation is taken in increasing speeds. The different centrifugation speeds often create separation into not more than two fractions, so the supernatant can be separated further in additional centrifugation steps.
During a relatively short or slow centrifugation, the particles are separated by size, with larger particles sedimenting farther than smaller ones. Over a long or fast centrifugation, particles travel to locations in the gradient where the density of the medium is the same as that of the particle density; (ρp – ρm) → 0.
Sedimentation equilibrium experiments reports the molar mass of analytes and their chemical equilibrium constants. [3] The rotor speed is adjusted such that a steady-state concentration profile c(r) of the sample in the cell is formed, where sedimentation and diffusion cancel out each other.
Such an "equilibrium" centrifugation can allow extensive purification of a given particle. Sucrose gradient centrifugation —a linear concentration gradient of sugar (typically sucrose, glycerol, or a silica-based density gradient media, like Percoll )—is generated in a tube such that the highest concentration is on the bottom and lowest on top.
Sedimentation equilibrium in a suspension of different particles, such as molecules, exists when the rate of transport of each material in any one direction due to sedimentation equals the rate of transport in the opposite direction due to diffusion. Sedimentation is due to an external force, such as gravity or centrifugal force in a centrifuge.
Equilibrium gradient centrifugation; I. Isopycnic centrifugation; U. Ultracentrifugation This page was last edited on 21 June 2022, at 04:11 (UTC). Text is ...
Isopycnic centrifugation, often used to isolate nucleic acids such as DNA; Sucrose gradient centrifugation, often used to purify enveloped viruses and ribosomes, and also to separate cell organelles from crude cellular extracts; There are different types of laboratory centrifuges: Microcentrifuges