Double-strand breaks (DSBs) of giant DNA molecules after exposure to 1.0 MHz pulsed-wave ultrasound were quantitatively evaluated by single-molecule observation of giant DNA (T4 GT7 DNA; 166 kbp) through fluorescence microscopy. Aqueous solutions of DNA were exposed to ultrasonic waves with different sound pressures, repetition periods (1, 2, 5 ms), and pulse durations (5, 10, 50 μs). Below a threshold value of sound pressure, almost no double-strand breaks were generated, and above the threshold, the degree of damage increased in an accelerated manner as the pressure increased. DNA damage was much more severe for exposure to ultrasound with a shorter pulse duration. In addition, a longer pulse repetition period caused worse damage in DNA molecules. The effect of microbubbles on the damage induced by exposure to ultrasound had also been studied. While a result showed that a very small amount of microbubbles increased DSBs of DNA, this effect of microbubbles only weakly depended on their concentrations.

中文翻译：

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由兆赫兹超声引起的基因组大小的 DNA 双链断裂

 通过荧光显微镜对巨型 DNA (T4 GT7 DNA; 166 kbp) 进行单分子观察，对暴露于 1.0 MHz 脉冲波超声后的巨型 DNA 分子的双链断裂 (DSB)进行定量评估。DNA 水溶液暴露于具有不同声压、重复周期（1、2、5 ms）和脉冲持续时间（  5、10、50 μs)。在声压阈值以下，几乎不产生双链断裂，在阈值以上，损伤程度随着压力的增加而加速增加。暴露于脉冲持续时间较短的超声波时，DNA 损伤要严重得多。此外，较长的脉冲重复周期对 DNA 分子造成更严重的损伤。还研究了微泡对超声暴露引起的损伤的影响。虽然结果表明极少量的微泡会增加 DNA 的 DSB，但微泡的这种影响仅微弱地取决于它们的浓度。