HEAVY-ION-INDUCED SINGLE-STRAND AND DOUBLE-STRAND BREAKS IN PHIX-174 REPLICATIVE FORM DNA
HEAVY-ION-INDUCED SINGLE-STRAND AND DOUBLE-STRAND BREAKS IN PHIX-174 REPLICATIVE FORM DNA
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DOI：
10.1080/09553007214551351
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发表时间：
1972-01-01
期刊：
影响因子：
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通讯作者：
TOBIAS, CA
中科院分区：
文献类型：
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作者：
CHRISTENSEN, RC;TOBIAS, CA
测量了ΦX-174 Replicative Form I(RFI)DNA线性能量转移(LET)对加速原子核的损伤。辐射是在室温下进行的，在一种高度防辐射的肉汤中进行，以最大限度地减少自由基的影响。大多数离子束在连续混合的样品中终止。用~3H-TdR标记的RF DNA中性蔗糖梯度沉淀法测定辐照样品中RF I(超级线圈)、RF II(开式线圈)和RF III(线性)DNA构型的相对比例。用球体测定法测定DNA样品的活力。在所研究的LET范围内，单链断裂事件的生产效率(每rad)下降了三倍，而双链断裂事件的生产效率增加了五倍。单链断裂事件与双链断裂事件的比例变化从约26：1(60Co伽马射线)到约2：1(氧离子辐照)。在低LET时，双链断裂在观察到的活力丧失中所占比例不到10%，在高LET时上升到约50%。低LET下总DNA断裂事件的碱性蔗糖梯度测定结果始终高于类似的中性蔗糖测定结果，这表明辐照DNA中存在诱导的碱性不稳定键。
Damage caused by accelerated atomic nuclei was measured in ΦX-174 Replicative Form I (RF I) DNA as a function of linear-energy transfer (LET). Irradiations were performed at room temperature in a highly radioprotective broth to minimise the effects of free radicals. Most ion beams terminated in the continuously-mixed samples. By using neutral sucrose gradient sedimentation of3H-TdR-labelled RF DNA, irradiated samples were assayed for relative proportions of RF I (supercoil), RF II (open coil), and RF III (linear) DNA configurations. A spheroplast assay was used to determine the viability of DNA samples. The efficiency of production (per rad) of single-strand break events decreased three-fold over the LET range investigated, whereas double-strand break production increased five-fold. The ratio of single-strand break events to double-strand breaks varied from about 26 : 1 for60Co gamma-irradiation, to about 2 : 1 for oxygen-ion irradiation. Double-strand breaks accounted for less than 10 per cent of the observed loss of viability at low LET, rising to about 50 per cent at high LET. Alkaline sucrose gradient determinations of total DNA break events at low LET yielded consistently greater values than did analogous neutral sucrose determinations, suggesting the presence of induced alkali-labile bonds in irradiated DNA.