I have a protocol that requires me to use a centrifugation speed of 44,000 x g for 70 mins to generate cytoplasts from a human cell. However, I only have access to a ultracentrifuge rotor that goes up 42,200 x g.
Would it be possible for me to just run this ultracentrifuge at 42,200 x g for 70 mins or slightly longer to generate my cytoplasts?
You need the k-factors of the rotors and then use the relationship k1/t1 = k2/t2. The k-factor is found in the rotor specifications.
I'm always reluctant to run a rotor at its maximal rated speed, especially if I don't know how well it has been treated in the past or how old it is. Chances are the stated time and g-force in the protocol are more than sufficient, so spinning at 40,000 g for 80 minutes will probably achieve the desired result.
Of course, if different rotor and tube geometries are used, results will vary because of differences in k-factor, as Engelbert Buxbaum mentioned. People usually don't specify all the details of the centrifugation, such as the rotor used or the type of tube, so it may not be possible to compare k-factors.
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