Systems containing lyophilic material

Macromolecular solutions are stabilised by a combination of electric double layer interaction and solvation, and both of these stabilising 

Ammonium sulphate, which has a high solubility, is often used to precipitate proteins from aqueous solution. 

Lyophilic colloids can also be desolvated (and precipitated if the electric double layer interaction is sufficiently small) by the addition of non-electrolytes, such as acetone or alcohol to aqueous gelatin solution and petrol ether to a solution of rubber in benzene. 

The stability of lyophobic sols can often be enhanced by the addition of soluble lyophilic material which adsorbs on to the particle surfaces. Such adsorbed material is sometimes called a protective agent. The stabilisation mechanism is usually complex and a number of factors may be involved. 

Lyophilic stabilisation is particularly important in non-aqueous systems115, e.g. oil-based paints, and in systems of very high particle concentration where electrostatic stabilisation is of limited effectiveness. It is also essential in biological systems, e.g. blood, where the 

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Many facets of the container/closure system should be taken into consideration to expedite the development, scale-up, and production processes for lyophilized materials. It is important to remember that just as every drug product is unique, so is its packaging requirements. A thorough evaluation early in the development process will help to avoid problems later in the cycle. 

The majority of the studies outlined in Section 2 utilized the rapid and inexpensive plate incorporation assay with the Salmonella histidine-reversion system.All strains (missense and frameshift) should be screened with unknown materials. However, in practice, most determinations can be made with strains TAIOO and TA98 (containing the R plasmid pkMlOl). Crude materials or fractions for testing are usually dissolved in DMSO in the range of 5-10 mg of total solids/ml. Stock solutions are stored in the dark at 4°C. Fractions or subfractions are evaporated or lyophilized to dryness or to a concentrated tar before solubilization. In actual practice, many crude fractions are not completely soluble even in DMSO. The treatment can be carried out with the suspended material or the DMSO-soluble materials after suspension and centrifugation. 

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