Report centrifugal force in g units NOT rpm! (Rant)

Warren Gallin wgallin at gpu.srv.ualberta.ca
Fri Feb 16 11:56:27 EST 1996


I don't see it as quite that simple.  Sure you are reporting the g force at
the bottom of the tube, but the geometry of the rotor will determine what
the g force is at various parts of the tube.  Different rotors will give
different results.  Take the extreme example of a vertical rotor vs. a
swinging bucket rotor.  My preference is that one report both the type of
rotor, speed and length of centrigugation (for real reproducibility) and
also some general description of the geometry of the setup and the g-max,
for those who can not come up with the identical equipment.



In Article <4fvmra$df6 at sol.caps.maine.edu>, rr at bmmb01.umesci.maine.edu
(Robert Roxby) wrote:
>So many centrifugation protocols give only rpm and rotor type, even in 
>technical compendia devoted entirely to methods, such as Current 
>Protocols in Molecular Biology.  Rotor and rpm is ambiguous unless you 
>have the same centrifuge equipment as used in the original protocol, or 
>have data for that equipment.  I suggest exercising some rigor in 
>reporting centrifugation conditions in units of g.  It can be 
>easily calculated as follows:
>
>force (g) = w^2 *r/980 where w=2*pi*(rpm/60) and r is the distance to 
>from the center of rotation to the bottom of the tube.  
>
Warren Gallin,
Department of Biological Sciences, University of Alberta
wgallin at gpu.srv.ualberta.ca



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