Lipid methodology.

Advances in our knowledge of the circulating lipids and lipoproteins have been dependent on developments in analytical methods. In the past decade or so important advances have been made in this field, and some of the techniques now available to the lipid biochemist include analytical ultracentrifugal flotation (Pedersen, 1945; Gofman, Lindgren, Jones, Lyon, and Strisower, 1951); preparative ultracentrifugation with subsequent chemical analysis of fractions (Lindgren, Elliott, and Gofman, 1951; Hillyard, Entenman, Feinberg, and Chaikoff, 1955; Havel, Eder, and Bragdon, 1955; Bragdon, Havel, and Boyle, 1956); complexing and precipitation with polyanions (Burstein and Samaille, 1960; Bernfeld, Donahue, and Berkowitz, 1957); electrophoresis using various media, including paper (Lees and Hatch, 1963), cellulose acetate (Margolis and Langdon, 1966), starch gel (Kunkel and Slater, 1952), polyacrylamide gel (Narayan, Narayan, and Kummerow, 1965), and agar and agarose gel (Scanu, Lewis, and Page, 1958; Uriel, 1964; Noble 1968); immunological techniques including immunoelectrophoresis (Grabar and Burtin, 1964) aind immunodiffusion (Mancini, Carbonara, and Heremans, 1965); membrane filtration (Stone and Thorp, 1966). Other physico-chemical methods such as gas-liquid chromatography (Woodford, 1964), nuclear magnetic resonance (Chapman and Morrison, 1966), refractometry (Lindgren and Nichols, 1960), electron microscopy, x-ray techniques (Palmer, Schmitt, and Chargaff, 1941), and infrared and circular dichroic spectroscopy (Scanu and Hirz, 1968) have their place in the research laboratory. However the two techniques most widely used have been ultracentrifugation with chemical analysis of the density-gradient fractions, and the various types of electrophoresis. Indeed it is on the basis of the latter techniques, with ultracentrifugation as the reference method, that the lipoprotein families have been characterized, thus enabling biochemists and clinicians to gain an understanding of their physiological and pathological significance. In most clinical laboratories, instead of quantita-