In centrifugation the clearing factor or k factor represents the relative pelleting efficiency of a given centrifuge rotor at maximum rotation speed. It can be used to estimate the time (in hours) required for sedimentation of a fraction with a known sedimentation coefficient (in svedbergs):
The value of the clearing factor depends on the maximum angular velocity of a centrifuge (in rad/s) and the minimum and maximum radius of the rotor:
As the rotational speed of a centrifuge is usually specified in RPM, the following formula is often used for convenience:
Centrifuge manufacturers usually specify the minimum, maximum and average radius of a rotor, as well as the factor of a centrifuge-rotor combination.
For runs with a rotational speed lower than the maximum rotor-speed, the factor has to be adjusted:
- 2
The K-factor is related to the sedimentation coefficient by the formula:
Where is the time to pellet a certain particle in hours. Since is a constant for a certain particle, this relationship can be used to interconvert between different rotors.
Where is the time to pellet in one rotor, and is the K-factor of that rotor. is the K-factor of the other rotor, and, the time to pellet in the other rotor, can be calculated. In this manner, one does not need access to the exact rotor cited in a protocol, as long as the K-factor can be calculated. Many online calculators are available to perform the calculations for common rotors.
Famous quotes containing the words clearing and/or factor:
“[Panurge] spent everything in a thousand little banquets and joyous feasts open to all comers, particularly jolly companions, young lasses, and delightful wenches, and in clearing his lands, burning the big logs to sell the ashes, taking money in advance, buying dear, selling cheap, and eating his wheat in the blade.”
—François Rabelais (1494–1553)
“It is change, continuing change, inevitable change, that is the dominant factor in society today. No sensible decision can be made any longer without taking into account not only the world as it is, but the world as it will be.... This, in turn, means that our statesmen, our businessmen, our everyman must take on a science fictional way of thinking.”
—Isaac Asimov (1920–1992)