K-factor (centrifugation)
Encyclopedia
In centrifugation
, the K-factor represents the clearing factor
of a centrifuge rotor at maximum rotation speed. This factor can be used to determine the time required for pelleting a fraction with a known sedimentation coefficient
. The lower the K-factor, the more efficient the pelleting will be.
The K-factor can be calculated by the formula:
Where
is the maximum radius from the axis of rotation, and 
is the minimum radius from the axis of rotation. These parameters are usually available from the centrifuge rotor manufacturer. 
is the speed in revolutions per minute.
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
Centrifugation
Centrifugation is a process that involves the use of the centrifugal force for the sedimentation of mixtures with a centrifuge, used in industry and in laboratory settings. More-dense components of the mixture migrate away from the axis of the centrifuge, while less-dense components of the mixture...
, the K-factor represents the clearing factor
Clearing factor
In centrifugation the clearing factor or k factor represents the relative pelleting efficiency of a given centrifuge rotor at maximum rotation speed...
of a centrifuge rotor at maximum rotation speed. This factor can be used to determine the time required for pelleting a fraction with a known sedimentation coefficient
Sedimentation coefficient
The sedimentation coefficient s of a particle is used to characterize its behaviour in sedimentation processes, notably centrifugation. It is defined as the ratio of a particle's sedimentation velocity to the acceleration that is applied to it .The sedimentation speed v_t is also known as the...
. The lower the K-factor, the more efficient the pelleting will be.
The K-factor can be calculated by the formula:
Where
is the maximum radius from the axis of rotation, and is the minimum radius from the axis of rotation. These parameters are usually available from the centrifuge rotor manufacturer. is the speed in revolutions per minute.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