Specific forms of Aβ in Tg2576 and AD brains.A–D, Immunoblot analysis of SDS (A,C) and formic acid (B, D) extracts of 21M Tg2576 mouse brains and AD brains labeled with BAN-50 (A, B) or 4G8 (C,D). Two microliters of the SDS or FA extract (dried and resuspended) were directly added to each lane; proteins were separated on 10–20% Tricine gels. E,F, Immunoblot analysis of SDS (E) and formic acid (F) extracts of AD and 23M Tg2576 brains labeled with the following: 4G8, which detects both N-terminally modified and unmodified Aβ; anti-AβN1(D), which detects the unmodified N terminus; anti-N1(iD), which recognizes isomerized forms (l-iso-Asp) of AβN1; anti-N1(rD), which detects stereoisomerized forms (rectus Asp) of AβN1; anti-AβN3(pE), which detects forms beginning with pyroglutamate at position 3; or anti-AβN11(pE), which recognizes forms beginning with pyroglutamate at position 11. The Aβ in 10 μl of SDS or FA extracts was examined on each lane. In the SDS extracts, Aβ was immunoprecipitated with the indicated antibody as described in Materials and Methods before separation and immunoblotting with the same antibody. In the FA extracts, Aβ was dried and resuspended as described in Materials and Methods before separation and immunoblotting. Proteins were separated on 16% Tricine gels.G–L, Time course of accumulation of formic acid-soluble Aβ in Tg2576 brains (8M–23M) and AD brains labeled with 4G8 (G), anti-N1(D) (H), anti-N1(rD) (I), anti-N3(pE) (J), BA-27 (K), or BC-05 (L). The Aβ in 10 μl of formic acid extract was examined on each lane, and proteins were separated on 16% Tricine gels.