Lipoprotein fractionation.

Most of the methods used in the separation and fractionation of serum proteins have also been applied to the lipoproteins. Salt precipitationwas used as early as the last century to fractionate serum proteins, and with this technique a lipoprotein was isolated in fairly pure form for the first time by Macheboeuf (1929). The precipitation tcchniques most commonly used today are based on the precipitation of very-low-density and low-density lipoproteins by sulphated polysaccharides (Burstein and Samaille, 1955) (see below). Much of our preser't knowledge of the serum lipoproteins is based on the studies of Gofman and coworkers, who used a combination of analytical and preparative ultracentrifugation (DeLalla and Gofman, 1954). The analytical ultracentrifuge is not widely available but preparative ultracentrifugation which, in combination with lipid analysis of the separated fractions, remains one of the best tools for the study of serum lipoproteins, is quite widely used (Havel, Eder, and Bragdon, 1955; Furman, Howard, and Norcia, 1959; Hatch, 1968). Electrophoresis is one of the most important modern techniques for studying lipoproteins; an important milestone in its development, which led to the classification of hyperlipoproteinaemias of Fredrickson, Levy, and Lees (1967), was the inclusion of albumin in the buffer foi paper electrophoresis (Lees and Hatch, 1963). More recent techniques with agarose or cellulose acetate gel as supporting medium give better resolution of the lipoprotein pattern. Of other techniques, both ultrafiltration in combination with nephelometry and adsorption chromatography on glass powder or calcium phosphates have been used to a limited extent. Gel filtration techniques are fairly new and have mainly been used in the study of the apoproteins of the lipoproteins (Brown, Levy, and Fredrickson, 1970). Immunological methods such as immunoelectrophoresis and immunodiffusion have been invaluable in the study of the protein moiety of the lipoproteins. Such studies have been mainly qualitative (Hatch, 1968; Brown et al, 1970), but there are some quantitative studies (Lees, 1970). An excellent review of this field has been published by Hatch (1968). Practical Methods for Lipoprotein Fractionation