| Assay Method Information | |
| | In Vitro Fluorescence-Based Recombinant Tau Binding Assay |
| Description: | (A) Expression and Purification of Human Tau: 1 mM IPTG (Sangon Biotech, Cat. No A100487) was used to induce production of tau by bacteria (BL21, Invitrogen, Cat. No C600003) transformed with a full-length 2N4R tau expression plasmid. After 3 hours, cell pellet was resuspended in lysis buffer (100 mM PIPES, 1 mM EGTA, 1 mM MgSO4, pH 6.8) and lysed by sonication followed by centrifugation (15,000 rpm, 15 min, 4° C.). The supernatant was then placed in a boiling water bath for 20 min, followed by centrifugation (15,000 rpm, 15 min, 4° C.). Supernatant was loaded onto a Q-Sepharose Fast Flow column (GE healthcare, Cat. No 17-0510-01), the flow-through fraction was loaded onto an SP-Sepharose Fast Flow column (GE healthcare, Cat. No 17-0729-01), and tau protein was eluted with elution buffer (100 mM PIPES, 1 M NaCl, 1 mM EGTA, 1 mM MgSO4, 0.2 M NaCl, pH 6.8). Collected fractions of tau-containing eluates were pooled, concentrated and dialyzed against HEPES buffer (25 mM HEPES, 0.1 mM EDTA, 0.5 mM DTT, 100 mM NaCl, pH 7.2) and stored at −80° C. in small aliquots until use. Protein concentration was determined by UV absorption.(B) Preparation of Heparin-Induced Aggregated Tau (aTau):>2 μM of tau prepared in 30 mM Tris-HCl, pH 7.5 buffer was incubated in tube with 15 μM heparin (Sigma, Cat. No H3149) at 37° C. for 24 hours. (C) Compound Fluorescent Spectra Scanning Assay: Compounds were dissolved in 100% DMSO, and 40 nM aTau was incubated with 10 μM of each compound in 2% DMSO in 96 well plate (Corning, Cat. No 3573) at 37° C. for 1 hour. Emission and excitation of the compound was scanned by microplate spectrometer (EnSpire 2300, PerkinElmer).(D) In Vitro Fluorometric aTau Binding Assays: 2 μM aTau was diluted to 0.04 μM with 30 mM Tris-HCl (pH 6.8), and then incubated with serially diluted compound (three-fold serial dilutions, from 10 to 0.00017 μM) in a 96-well plate (Corning, Cat. No 3573) at 37° C. for 1 hour. Fluorescence intensity (excitation/emission=370/500 nm) of APN-0729 was read by microplate spectrometer (EnSpire 2300, PerkinElmer). Compound Kd values were calculated using the following equation: Y=B max *X/(Kd+X), where X is the concentration of compound; Y is the fluorescence signal of (compound+aTau)−(compound+DMSO); and B max is the maximum signal. |
| Affinity data for this assay | |
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