By using magnetic tweezers,atomic force microscope and mass spectrometry,we study the effects of pH on oxaliplatin-induced DNA condensation,the DNA persistence length,the amounts of micro-loops and of oxaliplatin bound to DNA.It is found that the DNA condensation degree,the amounts of micro-loops and of oxaliplatin bound to DNA increase with the decrease in the pH value while the DNA persistence length has an opposite behavior.The observed effects may be related to the drug resistance of cancer cells.