If the same experiment is performed in the presence of p53, the unzipping time becomes longer as the binding of p53 to the DNA stabilizes the hairpin, increasing its unfolding activation energy by ≈2 × 10−20 J. No unzipping delay is instead observed in the presence of the p53 mutant (Cys135Ser), revealing the inability of this protein to suppress the denaturation of a DNA hairpin and providing a possible molecular-level explanation for the ineffectiveness of p53 in suppressing tumor growth. The gene discussed is TP53; the disease is neoplasm.