Bio-Rad PDS-1000 / He™ and Hepta™ Systems - Manual (Page 35)

Suggested starting helium pressure conditions for optimizing various biological systems are:
Cell type Rupture disk pressure
Bacteria 1,100 psi
Fungi 1,300 psi
Yeast 1,300 psi
Plant cells/tissue 1,100 psi
Mammalian cells 1,100 psi
5.4 Solenoid Valve Adjustment
A factory pre-set metering valve (black knob) on the 3-way helium metering (solenoid)
valve assembly controls the fill rate of the gas acceleration tube. The proper fill rate is set at
the factory for a 1,550 psi rupture disk to burst within 12–15 seconds. A more rapid fill rate
may result in what appears to be a lower burst pressure, due to a lag of needle movement in
the oil-filled gauge. The metering valve (black knob) may be adjusted if desired. Adjust knob
in small increments: a clockwise rotation of the black knob will lengthen the fill rate.
5.5 Vacuum Flow Rate Control Valves
Both valves are set at the factory to be fully open (counter clock-wise), for maximum
flow rates. To decrease the rates, turn the valves (knob) clockwise until the desired evacua-
tion and/or vent rate is achieved (see Figure 2.9).
5.6 Distance Between Rupture Disk and Macrocarrier
The effect of the gas shock wave on microcarrier velocities is determined in part by the
gap between the rupture disk and the macrocarrier. The smaller the distance, the more pow-
erful the effect of the gas shock wave on macrocarrier acceleration.
Three hexagonal gap adjustment tools of 1/8", 1/4", and 3/8" have been provided to repro-
ducibly set the gap distance (Figure 2.4). A 1/4" distance between the rupture disk retaining cap
and the macrocarrier cover lid is recommended when initially optimizing bombardment parameters.
5.7 Distance Between Macrocarrier and Stopping Screen
Macrocarrier flight instability increases with greater travel distance, therefore, the shortest trav-
el distance is recommended. This is achieved by having the stopping screen support placed above
both spacer rings inside the fixed nest when initially optimizing bombardment conditions. The
macrocarrier flight distance can be adjusted by varying the position of the stopping screen support,
as positioned by the spacer rings inside the fixed nest of the microcarrier launch assembly. The trav-
el can be increased to a maximum of 16 mm in steps of 5 mm by varying spacer ring placement.
5.8 Distance Between Stopping Screen and Target Shelf (micro-
carrier flight distance)
One of the most important parameters to optimize is target shelf placement within the
bombardment chamber. This placement directly affects the distance that the microcarriers
travel to the target cells for microcarrier penetration and transformation.
Four target shelf levels are available in the bombardment chamber: level 1= 3 cm,
level 2 = 6 cm, level 3 = 9 cm, and level 4 =12 cm below the stopping screen (Figure 5.1).
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