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The Lp(a) lipoprotein, a distinct class of serum lipoproteins, was detected in 1962. It consists of an LDL particle to which a long polypeptide chain is attached by a disulfide bridge. The level of Lp(a) lipoprotein is genetically determined. Single locus control was suggested already in the very first report, and this has been conclusively confirmed by the demonstration of absolute genetic linkage to the plasminogen gene, from which the LPA gene is likely to have evolved. The detection in 1974 of an association between Lp(a) lipoprotein and coronary heart disease has been confirmed in numerous studies. The Lp(a) lipoprotein may have atherogenic as well as thrombogenic properties and thus form the bridge between atherogenesis and thrombogenesis. Genes determining a moderate level of Lp(a) lipoprotein may be longevity genes, and it seems possible that Lp(a) lipoprotein, because of its affinity to vessel walls, may also influence placental function. Lp(a) lipoprotein measurements should be included in the diagnostic work-up of people with premature coronary heart disease or with such disease in close relatives.

The apoprotein of human erythrocyte membranes was covalently spin-labelled with nitroxide-maleimide and mixed anhydride labels, before and after removal of sialic acids. The e.s.r. spectra and pH-induced spectral changes were compared with the reported spectra of native membranes. Interactions between the apoprotein and other lipids were examined using lipids containing spin probes. Lysolecithin was shown to bind more strongly than other lipids to membrane apoprotein. This binding was compared with the binding of lysolecithin to bovine serum albumin and acid casein. The formation of a lipoprotein complex between positively charged sialic acid free apoprotein and negatively charged sonicated dispersions of membrane lipid in an aqueous medium was examined using spin labels and spin probes. The data demonstrate that both polar and apolar interactions between the lipid and protein are involved in stabilisation of the complex.