Mosqueira F G, Albarran G, Negron-Mendoza A
Centro Universitario de Communicacion de la Ciencia, UNAM, Ciudad Universitaria, Mexico, D.F.
Orig Life Evol Biosph. 1996 Feb;26(1):75-94. doi: 10.1007/BF01808161.
This paper describes the possible effects of ionizing radiation arising from long-lived soluble radionuclides within clays, in particular 40K, at the epoch of the emergence of life on Earth. The free dispersion of soluble radionuclides constitutes an effective in situ irradiation mechanism that might have acted upon adsorbed nucleic bases and their derivatives on clays, inducing chemical changes on these organic molecules. Several types of well documented reactions for radiolysis of nucleic acid bases and their derivatives are known, even at low doses (i.e., 0.1 Gy). For example, estimates with a dose rate calculated from 40K from deep sea clays at 3.8 Ga ago, indicates that over a period of 1000 years the amount of organic material transformated is 1.8 X 10(-7) moles/kg-clay. Although ionizing radiation may also induce synthetic reactions with prebiological interest, all in all these considerations indicate that nucleic acid bases and their derivatives adsorbed on clays were exposed for long periods to degradation conditions. Such situation promotes decomposition of organic molecules rather than protection of them and enhancement of farther polymerization, as it has been usually taken for granted.
本文描述了地球生命出现时期，黏土中长寿命可溶性放射性核素，特别是40K产生的电离辐射可能带来的影响。可溶性放射性核素的自由扩散构成了一种有效的原位辐照机制，该机制可能作用于黏土上吸附的核酸碱基及其衍生物，从而引起这些有机分子的化学变化。即使在低剂量（即0.1戈瑞）下，核酸碱基及其衍生物辐射分解的几种反应类型也已得到充分记录。例如，根据38亿年前深海黏土中40K计算出的剂量率估算，表明在1000年的时间里，转化的有机物质数量为1.8×10^(-7)摩尔/千克黏土。尽管电离辐射也可能引发具有前生物意义的合成反应，但总体而言，所有这些因素表明，吸附在黏土上的核酸碱基及其衍生物长期处于降解条件下。这种情况促进了有机分子的分解，而不是像通常认为的那样对它们起到保护作用并促进进一步聚合。
