This chapter discusses structure, metabolism, and epidemiology of lipoprotein(a) [Lp(a)]. Lp(a) has been purified by gel filtration chromatography on Bio-Gel A-15m and has an apparent diameter of 262 Å as determined by quasielastic light scattering. Upon extended storage under low-salt conditions, the lipoprotein undergoes self-association to a particle with an apparent diameter of about 420 Å. The molecular weight of unfractionated Lp(a) has been measured by several different techniques including gel filtration chromatography, sedimentation equilibrium, and quasielastic light scattering. Lp(a) exhibits slow pre-β mobility when electrophoresed in agarose. One of the distinguishing physical properties of Lp(a) is its high tendency toward aggregation, especially at high concentrations (> 5–10 mg/ml). Several different assays have been developed for quantitating Lp(a) in fresh and frozen sera. Each of these assays is based upon an immunochemical reaction between the apo(a) antigen and an antibody directed against one or more of its determinants.
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