Real lab failures, root causes, and fixes — curated and bilingually annotated by our team.
Multiple bands appear at molecular weights lower than the expected target protein, often accompanied by smearing or streaking below the primary band. This pattern suggests progressive breakdown of the intact protein.
Multiple bands or a smear/streak appear at molecular weights higher than the predicted size of the target protein. This pattern is characteristic of post-translational modifications adding mass to the protein.
Distinct bands appear at molecular weights corresponding to known cleavage products or activated forms of the protein, rather than the full-length form. The fragment pattern may be specific and reproducible, distinct from degradation smearing.
Multiple bands appear at unexpected molecular weights that do not correspond to known forms of the target protein. These bands may vary in intensity between experiments and do not correlate with expected protein expression patterns.
Band patterns differ from expected or previously observed results when using cell lines that have been maintained in culture for extended periods. Multiple unexpected bands or altered expression levels appear compared to earlier passages.
Additional bands appear at molecular weights that are integer multiples (2×, 3×, or higher) of the expected target protein size, indicating oligomeric forms. These higher molecular weight bands suggest incomplete protein denaturation.
Strong signal appears at the top of the gel (in or near the loading well) or at the bottom (dye front), unrelated to the expected molecular weight of the target protein. This is especially common for very high molecular weight proteins (>250 kDa).
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