Centrifugation fixed angle rotors

Free subcellular particles or virus from Percoll by centrifuging the respective fraction of cell fractionation in a fixed-angle rotor at 100 000 X g for 90 min. Percoll forms a solid pellet whidi contains practically no material of interest. 

Operation of a fixed angle rotor A Loading of sample B Sample at start of centrifugation C Bands form as molecules sediment D Rotor at rest showing separation of two components... 

Figure 10.5 Pore water extraction by (A) drainage centrifugation using a swing-out rotor and (B) immiscible liquid displacement using a fixed-angle rotor (after Kinniburgh and Miles, 1983).

Thermostatized centrifuge with fixes angle rotor (angle of inclination 33°) (e.g. Hettich Rotixa RP 001260 Tuttlingen Germany)... 

Figure 4-36. Fixed angle rotor. On the left is illustrated a conventional centrifuge tube, in which liquid is pressed against the lid during centrifugation. The right depicts a tube with an offset neck to avoid this problem.

Figure 13.2. Centrifugal forces in different rotor types. The angle is measured with respect the rotation axis, these means than a fixed-angle rotor with an angle of 14° is related to a vertical rotor, and therefore its sedimentation pathlength is shorter than in a 40° rotor.

Ultrafiltration. The second method is an ultrafiltration procedure for FT4 determination in serum that is significantly less time-consmning than dialysis. " In this method, the serum specimen is adjusted to pH 7.4, incubated for 20 minutes at 37 °C (to achieve equilibrium of the binding at this temperature), and then appfied to an ultrafiltration device for centrifugation for 30 minutes at 37 °C and 2000 Xg (using a fixed-angle rotor). Subsequently the ultrafiltrate is analyzed for T4. Variable protein leakage in ultrafiltration devices continues to hamper commercialization of this method. 

Centrifugation With the concentration devices from the Amicon company, the solution to be concentrated is centrifuged in a fixed-angle rotor over a filter (max. 5,000 g). The concentrate collects above the filter and can be transferred into an Eppendorf tube in a second centrifugation step. The different systems (Microcon, Centricon, Centriprep) concentrate 0.5 to 15 ml of source solution into 5 to 500 pi. Depending on the filter, the process takes between 10 minutes and 3 h. The company offers filters with MG limits from 3 to 100 kd. 

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