PN B32164AC
18
JA-14.50 Fixed-Angle Rotor
Preparation and Use
Figure 10
Examples of Tubes with Minimum and Moderate Crazing
Run Times
The
k
factor of the rotor is a measure of the rotor’s pelleting efficiency. Beckman Coulter has
calculated the
k
factors for all of its rotors, at maximum speed with full tubes, using the following
formula:
EQ 1
where
ω
is the angular velocity of the rotor in radians per second (
= 0.105
RPM),
r
max
is the
maximum radius, and
r
min
is the minimum radius.
After substitution:
EQ 2
In the JA-14.50 rotor, the
k
factor is 787 for full 50-mL tubes at maximum speed.
*
For containers that
nominally hold less than 50 mL, the
k
factors will be different. Calculate the
k
factors for
these containers using
.
Use the
k
factor in the following equation to estimate the run time
t
(in hours) required to pellet
particles of known sedimentation coefficient
s
(in Svedberg units,
S
).
EQ 3
For example, at 14,000 RPM
E. coli
(
s
= 3600
S
) will pellet in
EQ 4
* Based on sedimentation in water at 20°C.
k
r
max
r
min
⁄
(
)
ln
ω
2
-----------------------------------
10
13
3600
------------
×
=
k
2.533
10
11
×
(
)
r
max
r
⁄
min
(
)
ln
RPM
(
)
2
------------------------------------------------------------------------
=
t
k
s
---
=
t
787
3600
------------
13 min
≈
=
Содержание JA-14.50
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