Geard C R, Colvett R D, Rohrig N
Mutat Res. 1980 Jan;69(1):81-99. doi: 10.1016/0027-5107(80)90178-5.
A unique radiation configuration, triads of protons, where mean separation between protons was controlled to be about 0.2 microns, has been used to irradiate Chinese hamster V79 cells. These triads of accelerated particles were more effective at producing chromosomal aberrations than randomly incident particles. Cells were irradiated with either single or three associated protons, with each proton depositing energy intracellularly at an LET of about 30 keV per micron. The associated protons were produced from accelerated molecular ions (H3+) that dissociated into atomic ions in a 6 mu Mylar foil on which the cells were growing, becoming triads of particles separated by a mean of about 0.2 microns in the cell nuclei. Chromosomal aberrations were scored from cells accumulated with colcemid over hourly intervals after irradiation. Those cells closest to mitosis (late G2) were the most sensitive to radiation, while overall "triple" protons were 52% more effective than single protons in producing aberrations. Only 10% of particles incident in nuclei resulted in an effect for the most sensitive period (late G2) dropping to 2% for the least sensitive period (early S--late G1). The frequencies of chromatid deletions declined dramatically with time post-irradiation, with isochromatid deletions less so and the frequencies of chromatid interchanges comparatively unchanged. Chromatid deletions and isochromatid deletions were often subtantially increased after "triple" proton irradiation, with the frequencies of chromatid interchanges less effected. This implies that both chromatid and isochromatid deletions can readily result from interactions between pairs of induced lesions about 0.2 microns apart. Achromatic lesions (gaps) were numerically equivalent after both irradiations implying a single lesion production mode. Results are compatible with there being a substantial short range component of interaction (less than 0.1 microns) between damaged sites, with a long range component of interaction extending to a few tenths of a micrometer.
一种独特的辐射构型，即质子三联体，其中质子间的平均间距被控制在约0.2微米，已被用于照射中国仓鼠V79细胞。这些加速粒子三联体在产生染色体畸变方面比随机入射粒子更有效。细胞用单个或三个相关质子进行照射，每个质子在细胞内以约30keV/微米的线性能量传递沉积能量。相关质子由加速的分子离子（H3+）产生，这些分子离子在细胞生长所在的6微米聚酯薄膜中解离成原子离子，在细胞核中形成平均间距约为0.2微米的粒子三联体。照射后每隔一小时对用秋水仙酰胺积累的细胞进行染色体畸变评分。那些最接近有丝分裂的细胞（G2晚期）对辐射最敏感，而总体而言，“三联体”质子在产生畸变方面比单个质子有效52%。在最敏感时期（G2晚期），只有10%入射到细胞核中的粒子产生效应，在最不敏感时期（S早期 - G1晚期）降至2%。染色单体缺失的频率在照射后随时间急剧下降，等臂染色单体缺失下降程度较小，染色单体互换频率相对不变。“三联体”质子照射后，染色单体缺失和等臂染色单体缺失通常大幅增加，染色单体互换频率受影响较小。这意味着染色单体和等臂染色单体缺失都很容易由相距约0.2微米的成对诱导损伤之间的相互作用产生。两种照射后无色病变（间隙）在数量上相当，这意味着单一的病变产生模式。结果与受损位点之间存在大量短程相互作用成分（小于0.1微米）以及延伸至几十分之一微米的长程相互作用成分相符。
