Centrifugation vertical rotors

The tubes of the swinging bucket rotor type are accommodated in a pivoted bucket moving from vertical to horizontal position during acceleration under the influence of the centrifugal field. The sedimentation path length is lowest in vertical rotors and highest in swinging-bucket rotors. 

Operation of a vertical rotor A Loading of sample B Beginning of centrifugation C, D During centrifugation E Deceleration of sample F Rotor at rest... 

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.

In vertical rotors (Fig. 13.2) the tubes are fixed in a vertical position during centrifugation, and when the centrifugal force increases the solution reorients to the g force. The reorientation process is explained later in this chapter. For now, this means that in this rotor the tube covers are important, and must be able to withstand... 

This is not the case with fixed-angle and vertical rotors, where the centrifuge tube angle is fixed and determined by the rotor design. Therefore, the gradient and sample redistribute in the tubes, as shown in Figure 13.4. This redistribution process takes place at low velocity (0-1000 rpm), to preserve the gradient, and... 

Figure 13.4. Redistribution of the sample layer and density gradients during centrifugations using fixed-angle and vertical rotors. In (a), the sample (with lower density than the gradient top) is layered, the rotor is at rest. In (b), the rotor begins to accelerate, and the sample begins reorientation. In (c), the sample separation proceeds. In (d) the rotor is at rest, and the particle bands are oriented by the Earth s gravitational force.

This mixture, adjusted to contain 20% of iodixanol, was transferred to 11-mL tubes and centrifuged in a vertical rotor at 364,000 g (4 °C, 3.5 h). Under these conditions, a gradient with a density from 1.02 to 1.25 was formed. Following centrifugation, the gradient was collected through a puncture in the tube bottom, in 0.5-mL fractions. Each fraction was assayed by PCR to determine retrovirus concentration. 

The main circulation pump (pump) is intended for providing the sodium circulation in primary circuit. The pump is centrifugal, vertical arrangement, single-stage, console, sealed, electrically driven type. Motor — asynchronous, double-speed, vertical arrangement with squirrel-cage rotor. 

Rotors for a high-speed centrifuge. A Fixed angle B swinging bucket C vertical. Courtesy of Beckman Instruments, Inc. 

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