Expression of mature APP correlates with the release of N-terminally truncated Aβ peptides. For the correlation analysis 12 cultures (1× CON, 4× PB, 2× acLDL, 3× LPS, 2× PB+LPS) were analysed simultaneously for intracellular APP and released Aβ-peptides by APP-SDS-PAGE and 2D-Aβ-WIB, respectively. Pearson's correlation coefficient (r) and the respective p-value were calculated for the association of the relative amounts of APP band 1 (APP1), band 2 (APP2), band 3 (APP3), and band 4 (APP4) with the relative amounts of N-terminally truncated Aβ peptides migrating at the isoelectric point pI 6.37 (N-truncated Aβ). The relative amount of single APP-bands was determined by dividing the signal intensity of the respective band by the sum of the signal intensities of all four visible APP bands. For the relative amount of N-truncated Aβ the sum of all visible Aβ isoforms migrating at pI 6.37 (Aβ2-40, Aβ2-42, Aβ2-40a and the Aβ peptide at spot 6.37-G) were divided by the sum of all quantified Aβ-peptide spots. The proportion of N-terminally truncated Aβ peptides correlates positively with mature APP (APP1) and negatively with APP2.