Apo lipoprotein A-I (apo A-I) obtained from delipidated serum high density lipoprotein (HDL) was isolated and characterized. HDL was obtained by three ultracentrifugations and was purified by gel-filtration. Apo A-I was isolated from apo HDL by two gel-filtrations in 1% SDS and 6M urea.
Apo A-I had a molecular weight of approximate 27,000 by SDS-polyacrylamide gel electrophoresis and had a characteristic amino acid composition showing low amounts of isoleucine and no cystine or cystein. The amino acid composition of apo A-I was compatible with the result report by Baker et al. Antisera against apo A-I were prepared and immunological propertsy of apo A-I were defined.