托福阅读背景知识之早晨的阳光更安全

　　The early bird gets the worm—and may avoid skin cancer. Because a new mousestudy suggests that, for humans, tanning in the mornings may be less likely topermanently damage DNA and cause skin cancer.

　　早起的鸟儿有虫吃，当然也能避免皮肤癌。因为，一项旨在人类健康的动物试验研究显示，晒早上的阳光也许不太容易损害你的DNA从而引发可怕的皮肤癌。

　　A mouse’s levels of the DNA-repairing protein XPA are different fromours—they peak in the morning and bottom out in the evening. Researchers exposedmice to UV radiation when their XPA was at its minimum level, around 4 a.m., andothers to the same rays around 4 p.m., when XPA levels peaked.

　　人类的DNA修复蛋白XPA含量变化与老鼠的不同，一般在早晨达到峰顶，而晚上则降低到谷底。研究人员进行了相关实验如下：实验组1—在早上4点左右小鼠的XPA含量最低时进行UV辐照;而实验组2---在晚上4点也就是小鼠的XPA含量最高时进行，然后对比两组的结果。

　　Mice who tanned while low on the repair protein developed skin cancerfaster and five times more frequently than their evening-tanning counterparts.The study is in the Proceedings of the National Academy of Sciences. [ShobhanGaddameedhi et al, Control of skin cancer by the circadian rhythm]

　　结果显示，XPA含量低的实验组动物在照射下，更快的患上皮肤癌，并且比含量高时进行的实验组得病的速度快5倍。研究已经发表在《国家科学研究进展》杂志上。

　　Unlike mice, humans are not nocturnal, so their XPA levels rise and fall atdifferent times. In people, XPA is at prime DNA-repairing levels in the morning,which thus looks the safest time for UV exposure. So if you want to avoid skincancer, probably go to the tanning salon early—or better yet, don’t go atall.

　　不像鼠类那样只在夜间活动，所以人类的XPA含量在不同的时间会有上下起伏的波动。人类的XPA蛋白在早上会达到修复DNA能力的最高含量，因此在此时如果受到紫外线的照射，也许最安全。因此如果你想避免患皮肤癌的话，或许去晒健康肤色也要赶早一些比较好------或者更安全的做法就是，根本不去晒~