RD4 cannot recognize N279D-4R tau, but new anti-4R labels both WT and N279D-4R tau equally. Immunoblot analysis of wild-type (WT) and N279D mutant tau before (WT, N279D) and after (p-WT, p-N279D) phosphorylation with PKA, using T46 (a), RD4 (b), anti-4R (c) and 12E8 (d) antibodies. Immunoblot analysis of six recombinant human tau isoforms with T46, RD3, RD4 and anti-4R antibodies (e). Specificities of RD4 (1:1000 dilutions) and anti-4R (1:3000 dilutions) antibodies for synthetic peptides, L-Asn (wild-type), L-Asp, L-isoAsp and D-Asp peptides (0.625 ~ 10 μg/mL) tested by ELISA assay (f). Quantitation of the ELISA results (the mean of absorbance at 490 nm on 1.25 μg/mL peptide is shown (g). Pathways for deamidation of asparaginyl residues (h). L-Asn residue can be converted spontaneously via a succinimidyl intermediate to form L-Asp, D-Asp. L-isoAsp and D-isoAsp residue (modified from Ref. ).