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A new study used atomic-scale simulations to reveal not one escape route but a web of pathways, all activating within the first quadrillionths of a second after UV light strikes.<\/p>\n
A molecule under fire<\/p>\n
Sunlight carries a band of energy that our eyes never see. This is UV radiation<\/a>, the invisible stuff that reddens skin and, over years, drives most skin cancers. <\/p>\n When UV radiation lands on DNA, the molecule soaks it up \u2013 which makes it dangerous.<\/p>\n Left unchecked, it can rearrange the bonds holding the code together, scrambling instructions and seeding mutations. Yet DNA rarely lets that happen. <\/p>\n Chemists call the trait photostability<\/a> \u2013 taking in light and shedding it without harm.<\/p>\n A team at the University of Surrey<\/a>, working with collaborators in France, set out to catch the process in the act. <\/p>\n The study was led by Juliana Gon\u00e7alves de Abrantes, a postgraduate researcher at Surrey.<\/p>\n Energy that must vanish<\/p>\n The reason DNA rarely breaks from sunlight comes down to speed. <\/p>\n A single base \u2013 one chemical letter of the genetic alphabet \u2013 can absorb a packet of UV energy and dump it almost at once.<\/p>\n Lab experiments<\/a> have clocked lone bases shedding that energy in well under a trillionth of a second. The molecule slips back to its calm resting state before anything can go wrong.<\/p>\n That clock runs in femtoseconds. One femtosecond is a quadrillionth of a second, a span so short the energy drains away before the molecule\u2019s bonds can rearrange and snap.<\/p>\n Two bases, many exits<\/p>\n DNA spells out its instructions with four bases that pair off in a fixed way. <\/p>\n The team zoomed in on two of them, guanine and cytosine, which clasp together through a few chemical bonds.<\/p>\n For years, the picture held that an excited pair had one main door back to safety. The new work tells a busier story. <\/p>\n In the simulations, absorbing UV light causes an electron to shift from guanine toward cytosine.<\/p>\n That lopsided, charged state is itself unstable, and rather than returning by a single route, the energy fans out through a network of competing reactions. The diversity is the heart of the finding.<\/p>\n Watching the atoms move<\/p>\n Seeing this in a living cell<\/a> is impossible. It\u2019s too fast and too small for any camera. The team rebuilt the base pairs inside a computer instead.<\/p>\n There, computer equations tracked the motion atom by atom, following where every electron and proton went after the flash. <\/p>\n The approach trades the mess of a real cell for a clean, controlled view.<\/p>\n To test whether layout mattered, they built two short stacks of these pairs in slightly different orders. <\/p>\n Both produced the same dominant escape route, a hint the behavior is built into the chemistry itself \u2013 not a quirk of one arrangement.<\/p>\n The proton\u2019s quick jump<\/p>\n The leading escape came down to a single proton \u2013 a hydrogen nucleus \u2013 hopping from guanine to cytosine across the central bond. <\/p>\n An earlier paper<\/a> had flagged this kind of move as part of DNA\u2019s defence. In the simulations, that one jump did most of the work. <\/p>\n Across one version of the stack it handled more than four out of five escapes; in the other, roughly seven in ten. The same move, dominant either way.<\/p>\n A less common pathway moved the proton from a different region of guanine to an oxygen atom on cytosine. <\/p>\n This route accounted for roughly a quarter of escapes in one stack and about one-sixth in the other. Transfers in the opposite direction were rare.<\/p>\n Coupled but not locked<\/p>\n Watching it unfold, the team noticed something about how the electron and proton traveled. <\/p>\n In the simulations, the two moved together, each nudging the other, but not bolted into a single rigid step.<\/p>\n That loose link surprised the researchers most. Were the two locked together, DNA would have one escape mechanism and little else. <\/p>\n Because they move in concert without being chained, the pair finds many slightly different paths home.<\/p>\n The guanine-cytosine pairing has drawn attention for decades. Until this study, no one had mapped the full crowd of routes running at once.<\/p>\n Beyond a single cell<\/p>\n DNA protecting itself was already known. The new finding is more precise.<\/p>\n The protection runs through a web of competing, ultrafast reactions rather than one tidy mechanism, with electron and proton motions linked yet free to vary.<\/p>\n Dr. Marco Sacchi is an associate professor of physical and computational chemistry at Surrey and the study\u2019s senior author.<\/p>\n \u201cWe can now see the incredibly fast molecular processes that safely drain away the energy before damage has a chance to spread,\u201d said Dr. Sacchi.<\/p>\n Knowing the exact molecular steps gives scientists a clearer picture of how mutations arise, how cells age, and how radiation affects living tissue.<\/p>\n DNA guards itself not with one trick but with many, firing in the first quadrillionths of a second after light strikes.<\/p>\n The study is published in The Journal of Physical Chemistry Letters<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Chemists had a tidy explanation for why DNA survives daily exposure to sunlight. One fast molecular step sheds…\n","protected":false},"author":2,"featured_media":706510,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[49,48,66],"class_list":["post-706509","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ca","tag-canada","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/706509","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=706509"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/706509\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/706510"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=706509"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=706509"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=706509"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}