More antibody isn't always better! See how the amount of antibody used can affect the your Chromatin Immunoprecipitation (ChIP) results in this Tech Tip hosted by Fang.
The optimal amount of antibody to use in a ChIP assay varies, depending on the antibody's affinity, sensitivity and specificity. More antibody is not always better - both too much and too little antibody decreases ChIP signal. For most ChIP-validated antibodies, 0.5–2 µg of antibody generates an optimal signal-to-noise ratio in the ChIP assay. It's also important to maintain the ratio of antibody volume to the amount of the chromatin, rather than the ratio of antibody volume to the IP volume. For a control antibody such as IgG, you should use an equivalent amount as your test antibody for a fair comparison.