5′ -- AGA GAT TGC CTG ACG TCA GAG AGC TAG -- 3′
3′ -- TCT CTA ACG GAC TGC AGT CTC TCG ATC -- 5′
Underlined nucleotides are the binding site. IRDye 700 oligonucleotides are supplied as 25 µL of 50 nM (or 50 fmol/µL) double-stranded DNA.
CREB proteins are cellular transcription factors activated by phosphorylation of various kinases that bind to certain DNA sequences. For this reason, it is a common oligonucleotide used in EMSA to assess protein binding.
You should establish conditions of the binding reaction for each protein-DNA pair. For IRDye 700 CREB oligonucleotide, the following binding reaction is a good starting point:
| Reaction | µL |
|---|---|
| 10X Binding Buffer (100 mM Tris, 500 mM KCI, 10 mM DTT; pH 7.5) | 2 |
| Poly (dl•dC) 1 µg/µL in 10 mM Tris, 1 mM EDTA; pH 7.5 | 1 |
| 25 mM DTT/2.5% Tween® 20 | 2 |
| 1% NP-40 | 1 |
| Water | 12 |
| IRDye 700 CREB | 1 |
| PC12 nuclear extract (positive control) (5 µg/µL) in Dilution Buffer (20 mM Hepes (pH 7.9), 100 mM KCI, 1 mM MgCl2, 20% glycerol, 0.5 mM PMSF and 0.5 mM DTT) | 1 |
| Total | 20 |
After the addition of the DNA to the protein-buffer mix, reactions are incubated to allow protein binding to DNA. A typical incubation condition is 20-30 minutes at room temperature.
Since IRDye infrared dyes are somewhat sensitive to light, it is best to keep binding reactions in the dark during incubation periods (e.g., put the tubes into a drawer or simply cover the rack containing tubes with aluminum foil). After the incubation period, 10X Orange Loading Dye (P/N 927-10100) is added to the binding reaction for electrophoresis.
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