科學家對地球上生命起源的新看法

SCIENTISTS PROPOSE NEW THEORY FOR HOW LIFE ON EARTH BEGAN-

《科學家對地球上生命起源的新看法》

         

            生命起源和生物体的演化

BY HANNAH OSBORNE ON 5/19/17 AT 6:17 AM

編按：

本文作者下列所提，並非『鷄蛋和小雞，那一項先後發生』的無稽之談，而是和生化(BIO-CHEMISTRY) 和遺傳工程(GENETIC ENGINEERING) 相關的科學，來探討生命之起源。文章內容頗有深度，若你對生命科學感興，不妨細心一讀。

How life on Earth first started is a mystery mankind has grappled with for thousands of years. Scientists generally agree that all life must have evolved from single-celled organisms that first emerged around 3.8 billion years ago. But how this first form of life emerged is subject of much debate.

             DNA和RNA之分別

地球上的生命如何首次開始，是人類千百年來努力設法解開的神秘。科學家們普遍同意，所有的生命必定是，從約 38 億年前的單細胞生物進化而來。但生命首次方式如何演化，則是大家爭論的話題。

In a study published in Nature Communications Friday, scientists from the U.S. and the U.K. have proposed a new theory about how a group of molecules essential to all life on Earth could have formed on our primordial planet.

本週五，發表在「自然通訊」雜誌上的一項研究中，來自美國和英國的科學家們提出了新的看法-有關在我們原始的星球上，對地球上所有生命至關重要的一組分子，如何能夠形成.

The researchers focus on a group of molecules called nucleotides. These form the building blocks of DNA and RNA (a nucleic acid that carries instructions from DNA), which are essential to all life on Earth.

研究人員將焦點集中於稱為核苷酸的微分子上。這些構成了DNA 和 RNA （RNA乃指攜帶 DNA 指示的核酸），它們對地球上所有生命都是至關重要的組成骨幹。

Earth from space.NASA 從太空看地球(太空中心提供)

In the paper, the scientists look at purines and pyrimidines—the two nitrogenous bases of nucleotides. Previously, it was thought that  purines and pyrimidines must have emerged as a result of separate processes. This is because they can only form in completely incompatible conditions—recent research “uniformly fails to account for simultaneous access to both pyrimidine and purine,” the scientists write. “Remarkably, all proposed prebiotic syntheses of pyrimidine and purine nucleotides have yielded either pyrimidines or purines separately, but never (yet) both by the same strategy.”

   

在本文中，科學家們注視purines and pyrimidines— 兩個核苷酸的氮基的(註)。以前，人們認為這兩種生物合成物(biosynthesis) ，必定經由單獨的進程結果而產生出來。這是因為，他們只能在完全不相容的條件下形成 —最近的研究「一致地未能」解釋出來，無法同時接近purines and pyrimidines，科學家們如此寫道。他們又說『引人注目的是，所有擬議的purines and pyrimidines事先生物合成法，已分別產生核苷酸，但從來無法用以相同的策略，同時產生兩種。

註：purine，中譯普林，如amino~氨基普林。pyrimidines三氮三烯陸圜。

DNA和RNA中，這兩個基地用它們完全的普林，形成了氫氣鏈(hydrogen bonds) 。普林是經由生物合成為核甘酸，特別成為核酸醣類

However, the researchers have now shown how these two nucleotides could have formed by the same process. "We provide a new perspective on how the original RNA molecules were made and suggest a simple chemical solution for delivering both purine and pyrimidine nucleotides at the origins of life," study author Matthew Powner said in a statement.

儘管如此，研究人員現在已顯示出來，如何經由相同的過程，來形成這兩個核苷酸。研究作者說『對原始的 RNA 分子如何製造出來，我們提供了看法的新視角，並建議用簡單的化學解決方法，在生命開始時，同時送出普林和嘧啶核苷酸』。

The scientists show how purines and pyrimidines can form from a common precursor molecule that could have existed before life on Earth began. They find 8-oxo-purine shares underlying similarities with pyrimidine nucleotides. These two nucleoids can form under the same chemical conditions on a sugar scaffold, then bind together through molecular interactions—eventually resulting in the molecules that go on to become RNA.

科學家們展示給我們看，地球上的生命開始之前，普林和嘧啶如何從可能早已存在的共同前體分子而形成。他們發現8-氧代-普林，與嘧啶核苷酸，具有共同相似性。這兩個生殖細胞在可以形成糖架的相同的化學條件下，可以形成；然後通過分子間的相互作用而綁在一起，— 最終導致成為 RNA分子。(Ribonucleric acid-核糖核酸)

The process identified “may have played a key role in primordial nucleic acids prior to the emergence of canonical nucleotides of biology [the base of DNA],” they conclude.  

他們的結論是， 在初始核酸中，這個標識的進程 『在生物學上公認的的核苷酸的[即DNA 的基礎] 誕生之前，可能已經發揮了關鍵作用』。註：DNA= Deoxyribonucleric Acid-去氧核糖核酸

                       

       生命的化學要素-氨基酸,血脂肪, 碳水化合物,核酸,小粒子

Powner said: "RNA is the cornerstone of all life on Earth and probably carried the first information at the outset of life, but making RNA requires both purine and pyrimidine nucleotides to be simultaneously available. A solution to this problem has remained elusive for more than 50 years.”

作者Powner說: 『RNA(核糖核酸) 是地球上所有生命的基石，和可能在生命開始時，就帶有這個第一個訊息，但卻使 RNA 需要普林和嘧啶核苷酸，可以同時獲得。這個問題的答案，超過50 年以上，一直難以捉摸。』

                     

Shaun Stairs, first author of the study, adds: "The mechanism we've reported gives both classes of molecule the same stereochemistry that is universally found in the sugar scaffold of biological nucleic acids, suggesting that 8-oxo-purine ribonucleotides may have played a key role in primordial nucleic acids.”

Shaun Stairs，此項研究工作的第一作者補充說: 『我們曾經報導過的機制，給這兩類分子相同的立體化學，它通常普遍見於，生物核酸的糖支架上，它也暗示，8-氧代-普林核苷酸，可能早在原始的核酸中發揮了關鍵作用。』

Justin Lai 譯自Newsweek 

美國南加州

05/21/2017