Technical information

Centrifuge Standard Operating Procedure 3
Table 1-1: Media suitability for density gradient separations applications
(Basics of Centrifugation, Cole Parmer Technical Library)
Gradient
Media
C
ells
Viruses
Organelles
Nucleo
-
proteins
Macro
-
molecules
Sugars Limited use Good Good Limited Use
Not
suitable
Poly
-
saccharides
(e.g. Ficoll)
Good for
some
applications
Good for
some
applications
Good for
some
applications
Not suitable
Not
suitable
Coll
oidal
Silica (e.g.
Percoll)
Good Limited use Good Not suitable
Not
suitable
Iodinated
media (e.g.
Nycodenz)
Excellent
Good for
some
applications
Excellent Good Limited use
Alkali metal
salts (e.g.
CsCl)
Not suitable
Good for
some
applications
Not suitable
Good for
some
applications
Excellent
1.2.2 Rotor Selection
There are three main rotor types for any centrifuge: swinging bucket, fixed
angle, and vertical or near-vertical. Table 1-2 lists the suitability of each rotor
for various applications.
Swinging bucket rotors contain hinged buckets which swing out to a horizontal
position when the rotor is in motion. This type of rotor provides a longer path
length for settling than fixed angle or vertical tube rotors, and it is particularly
useful for density gradients. Swinging bucket rotors are generally inefficient for
pelleting.
Fixed angle rotors hold sample tubes at a specific angle and are all purpose
rotors. They are ideal for pelleting bacteria, yeast, and mammalian cells and
can be used for isopycnic density separations.
Vertical rotors hold sample tubes completely vertical or nearly vertical
throughout a run. These rotors are ideal for isopycnic separations of DNA, RNA,
and lipoproteins, but are not useful for pelleting.