Bio-Rad Helios® Gene Gun System - Manual (Page 44)

2. To measured gold, add aqueous solution of mRNA preparation.
The ratios of RNA to gold used are similar to those used for DNA (1–15 µg RNA/mg particles).
3. Add 1/10 volume of 5 M ammonium acetate and 2 volumes of 2-propanol, mix by vor-
texing. Place the microfuge tube at -20 °C for 1 hour.
4. Proceed with Section 5.2, steps 9–12.
10.2 Replacing the O-rings and Barrel Liner on the Helios Gene
Gun
Fig. 22. Location of barrel liner and O-rings in the Gene Gun. The barrel (cover) is removed for visual clar-
ity but is not required for barrel liner removal/insertion.
The Helios Gene Gun has three user-serviceable parts: the barrel liner and two O-rings
(Figure 22). The barrel liner screws into the barrel of the Gene Gun. It is a molded plastic
piece with the correct shape to permit optimum spread and penetration of the microcarriers at
the target site. It may be autoclaved between experiments or replaced.
To remove the barrel liner:
Hold the exposed part of the barrel liner (the spacer) and turn counterclockwise 4–5 turns
(see Figure 5).
To insert the barrel liner:
1. Remove the cartridge holder from the Gene Gun.
2. Place the barrel liner into the Gene Gun and turn clockwise until the threads just bind.
Do not overtighten.
The O-rings function to keep the helium from expanding around the tube in the firing
position in the cartridge holder. One O-ring is inserted at the end of the barrel liner that makes
contact with the cartridge holder; the other O-ring surrounds the exit port of the main valve.
Both O-rings fit in grooves with center supports.
40