Membrane Isolation Methods - An Introduction to Biological Membranes - page 285

WATER BATH

GASEOUS PHASE

TEFLON PLUG

GASKET

ETHER/LIPID
SOLUTION

MECHANICAL DRIVE

FIGURE 13.17 Ether vaporization method for production of LUVs [49] .

Concentration Methods
The dilution methods for making LUVs have one major disadvantage the LUVs are

formed in very dilute solution and must be concentrated. This is routinely done using two
types of filters, the best known being Amicon concentrators ( Figure 13.18 ). For both systems
pressure must be applied to the diluted LUV sample to force the buffer through small holes
crossing the filter. LUVs are too large to traverse the pores and so remain behind at ever
increasing concentration. In one type of concentrator high pressure is applied by nitrogen
gas from the top ( Figure 13.18 , Left) while the second type of concentrator relies on centrifu-
gation to drive the buffer through the filter pores ( Figure 13.18 , Right).
Using dilution methodologies, liposome size, and hence sequestered volume, can be
altered by changing the injection rates. This becomes very important if the LUVs are to be

e