Fragmented Chromatin Concentration Below Required Threshold (ChIP (CST Guide))

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Accepted Answer

DNA concentration of chromatin preparation is insufficient for ChIP, falling below the recommended 50 µg/ml or unable to provide 5-10 µg per IP reaction. Common causes: 1) Insufficient starting material: fewer cells or tissue than required for chromatin preparation 2) Incomplete cell or tissue lysis during chromatin extraction 3) Inaccurate cell counting prior to cross-linking leading to systematic underestimation 4) Enzymatic protocol: incomplete nuclear membrane disruption after micrococcal nuclease digestion Solutions: 1) If concentration is close to 50 µg/ml, add additional chromatin volume to each IP to achieve minimum 5 µg/IP 2) Count cells from a separate plate before cross-linking to determine accurate cell number 3) Enzymatic protocol: visualize cell nuclei under microscope before and after sonication to confirm complete nuclear lysis 4) Increase starting material according to tissue-specific yield tables (e.g., brain requires more than 25 mg per IP)