Apolipoprotein E (apoE) plays a critical role in lipoprotein particle clearance from blood plasma through its interaction with the low density lipoprotein (LDL) receptor and other related receptors. Here, we studied a 58-residue peptide encompassing the receptor binding region of apoE. ApoE3-(126 -183) was generated by cyanogen bromide cleavage of recombinant apoE3-(1-183), purified by reversed-phase high pressure liquid chromatography, and characterized by mass spectrometry.