Biology Reference
In-Depth Information
bath and sample chamber wall before reaching the cell, this method is far gentler and
less destructive than the direct tip method. Sonication is provided by a standard tip son-
icater that is orientated upside down with the cup horn attached to the vertical sonicater
shaft.
Another gentle, indirect sonication method involves use of a sonicating water bath, some-
times called a 'jeweler's bath' ( Figure 12.4 ). No titanium tip is involved. Instead the walls of
the bath supply the sonic energy and a vessel containing the cell sample is suspended in the
bath. This is the least destructive of the three methods and has the advantage of providing
accurate temperature control during sonication. However, its low energy limits its
membrane applications. Sonic baths are often used to suspend lipids into water in the prep-
aration of liposomes.
6. Bead Beaters
Another commonly employed homogenization procedure involves 'bead beaters' [20] ,an
example of which is shown in Figure 12.5 . These devices disrupt cells by violently shaking
them in the presence of small (usually) glass beads. Sometimes ceramic, zirconium, or steel
beads are used. Bead beating is done in sealed vials typically containing 100
lto1ml
samples and bead sizes are typically between 0.5 and 1.0 mm in diameter. Samples are
agitated at 2,000 to 5,000 oscillations per minute in a specially designed clamp driven by
a high energy electric motor.
m
7. Gas Ebullition (High Pressure 'Bomb')
Very rapid cell homogenization can be achieved by use of what is known as a 'high pres-
sure bomb' [21] . The most commonly used pressure bomb for cell homogenization, a Parr
Pressure Bomb, is shown in Figure 12.6 . The basis of this method is similar to what divers
experience as the bends (decompression sickness). The high pressures experienced by divers
in deep water force gas to dissolve into their body fluids. If the diver returns to the surface too
rapidly, the gasses (primarily nitrogen) leave the body fluids and return to the gaseous state
FIGURE 12.5 Bead Beater type of cell homogenizer. Courtesy of Glen Mills
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