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Percoll is a reagent consisting of colloidal silica particles used in cell biology and other laboratory settings. It was first formulated by Pertoft and colleagues, [2] and commercialized by Pharmacia Fine Chemicals. [3] Percoll is used for the isolation of cells, organelles, or viruses by density centrifugation.
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.
Using the example of a separation of eukaryotic organelles from intact cells, the cell must first be lysed and homogenized (ideally by a gentle technique, such as Dounce homogenization; harsher techniques or over homogenization will lead to a lower proportion of intact organelles). Once the crude organelle extract is obtained, it may be ...
Some density-gradient work for purifying cells and organelles can be carried out in swinging-bucket rotors, or in the case of Percoll gradients in fixed-angle rotors. [9] High-speed or superspeed centrifuges can handle larger sample volumes, from a few tens of millilitres to several litres.
An example of such a product is the "Accuspin System Histopaque-1077" sold by Sigma Aldrich. The cost of this product is significantly higher than basic Ficoll and Ficoll-Paque products. It is also possible to have the Ficoll-Paque separating system included in the Vacutainer used to collect the blood.
Gradient of parabola is used to evaluate diffusion terms. If F w > 0 and F e > 0 and if we use above equations for the convective terms and central differencing for the diffusion terms, the discretized form of the one-dimensional convection–diffusion transport equation will be written as:
A binding gel, diffusive gel (typically a polyacrylamide hydrogel) and filter membrane are stacked onto the base, and the cap is used to seal the gel and filter layers inside [4]: 4.2.3 Dimensions of the gel layers vary depending on features of the environment, such as the flow rate of water being sampled; [4]: 4.2.1 an example is an ...
The transport rate is usually estimated using the equations of Stokes flow, where the fluid velocity is obtained by equating the stress gradient to the viscous dissipation. A surface tension is a force per unit length, so the resulting stress must scale as Δ γ / L {\displaystyle \Delta \gamma /L} , while the viscous stress scales as μ u / L ...