APOE and Alzheimer disease: For instance, the peaks corresponding to the monomers (denoted by *) and the homomeric oligomers of Aβ peptides (denoted as the a and b peaks) are evident in the CSF and in the AD and control brain homogenates SDG spectra for all three APOE4 genotype groups (compare the light green shaded areas in Figure 4A with Figure 4B, and/or Figures 1A–D).