(C) Mass spectra of recombinant HTTex1 23Q after 16 hour of co-incubation with by TBK1 showing complete phosphorylation of S13 and S16. The lower panel is a representative western blot of the same phosphorylation reaction (upper panel) using anti-pT3 (CHDI-90001528-1), pS13 HTT (CHDI-90001039-1) and pS16 (ZCH11020 -generated in house), antibodies (ab) after the indicated phosphorylation reaction times. 