生命的起源--"RNA世界论"假说

自具有催化功能的 RNA分子被发现以来 ,主张生命起源于可以携带遗传信息的 RNA的“RNA世界论”受到广泛承认。该假说的关键之处在于要用实验证明“翻译系统”(能生产比 RNA功能更多的蛋白质 )能够在“RNA世界”中产生 ,证明这个“翻译系统”可由特定的 RNA分子组合来构成。为此 ,最近几年来 ,采用试管人工进化法 ( systematic evolution of ligands byexponential enrichment SEL EX法 ) ,在试管内挑选具有上述功能的 RNA分子的研究非常盛行。与此同时 ,解释“翻译系统”的主要结构——核糖体功能构造的研究也不断的有新结果问世…     

生命起源的RNA学说

生命的起源是一个千古之谜,多少年来,各种观点和学说此起彼伏,争论至今仍未停止;ＲＮＡ催化的证据,强有力地支持了生命起源的ＲＮＡ学说．然而,ＲＮＡ学说并未告诉我们ＲＮＡ从何而来,结合早期地球的有关事实、因相反应特点以及ＲＮＡ在水中的不稳定性,我们猜测ＲＮＡ可能是在固相反应条件下所得到的。     

生物大分子起源问题的讨论

关于生命在地球上的起源与进化问题,历来是一个颇多争论的学术领域。显然,人们无法目睹三十几亿年前地球上曾经发出的事情,也难以用实验的方法来重温这一漫长的历史过程,而只能凭借地球留给我们的某些蛛丝马迹去推想,去研究,去探索。伴随着科学技术的发展,有关生命起源的     

生命起源问题的新争论

生命起源是人们关心的问题,近年围绕着原始大气成分,生命起源于何处,以及是否存在过“ＲＮＡ世界”等问题,又有了新的看法和争论。本文对此作些简要的介绍。     

生物再生与生命起源演化中的几个问题

生物再生与生命起源演化中的几个问题赵双民（陕西省旬邑中学,７１１３００）生命起源问题从人类文明的萌芽到现在,人们不断努力地探索,产生过种种的假设和推测,随着时代的进步和科学技术的发展。生命起源和演化的研究取得了一系列重大成就。对生命起源和演化的研究,...     

生命和手性分子的起源

生命和手性分子的起源王文清,盛湘蓉（北京大学技术物理系１００８７１）生命和手性分子的起源是理论生物物理学的重大难题,它意味着物理学规律的突破和与生物学规律的统一。手性分子的起源来自生命起源中的对称性破缺。对称性可以表述为我们所研究的对象对某种变换的不...     

生命起源RNA世界的提出者——奥吉尔

奥吉尔是一位伟大的科学家,在化学领域提出了配位场理论,在生命起源领域提出了RNA世界假说,尤其在生命起源领域的研究为推动人们对早期生命诞生有了新的理解,撰写此文能够使大家对该科学家有一个较为全面的了解。     

原始生物大分子动态的数学模型及其进化意义

本文应用生态学上关于种群增长及种间竞争的逻辑斯缔方程,提出原始生物大分子动态的数学模型,对从该模型推导得的几种可能结果进行了分析,得出在生命起源初期的原始生物圈的生物多样性是很低的结论,即原始生物圈中较大量存在的只是一些种类单一的,可复制的原始生物大分子,因此,可以认为生物进化就是建立在这样的一个基础上,并沿着生物多样性不断提高的途径演化,该模型还有助于对广泛存在于现代生物基因组中的重复序列的起源的认识。     

生命起源研究回顾与现状

生命起源研究回顾与现状潘宪明,王文清（北京大学技术物理系北京１００８７１）１９９４年８月２９日至９月２日在意大利Ｔｒｉｅｓｔｅ国际理论物理中心（ＩＣＴＰ）召开了第三次国际生命起源研讨会,世界各国的五十多名科学家在会上宣读了论文,北京大学技术物理系潘宪...     

关于生命起源研究的新问题

关于生命起源研究的新问题周俊“地球上的生命是如何起源的？”,这是一个十分古老、也是现代的科学问题,有人将其列为本世纪和下个世纪有限的几个尚待解决的重大课题之一。目前国际上流行的学说（假说）或观点甚多,如果归结起来,基本可以分为两大类：一类是地表起源说...     

Montmorillonite,Oligonucleotides, RNA and Origin of Life

Na-montmorillonite prepared from Volclay by the titration method facilitates the self-condensation of ImpA, the 5'-phosphorimidazolide derivative of adenosine. As was shown by AE-HPLC analysis and selective enzymatic hydrolysis of products, oligo(A)s formed in this reaction are 10 monomer units long and contain 67% 3',5'-phosphodiester bonds (Ferris and Ertem, 1992a). Under the same reaction conditions, 5'-phosphorimidazolide derivatives of cytidine, uridine and guanosine also undergo self-condensation producing oligomers containing up to 12-14 monomer units for oligo(C)s to 6 monomer units for oligo(G)s. In oligo(C)s and oligo(U)s, 75-80% of the monomers are linked by 2',5'-phosphodiester bonds. Hexamer and higher oligomers isolated from synthetic oligo(C)s formed by montmorillonite catalysis, which contain both 3',5'- and 2',5'-linkages, serve as catalysts for the non-enzymatic template directed synthesis of oligo(G)s from activated monomer 2-MeImpG, guanosine 5'-phospho-2-methylimidazolide (Ertem and Ferris, 1996). Pentamer and higher oligomers containing exclusively 2',5'-linkages, which were isolated from the synthetic oligo(C)s, also serve as templates and produce oligo(G)s with both 2',5'- and 3',5'-phosphodiester bonds. Kinetic studies on montmorillonite catalyzed elongation rates of oligomers using the computer program SIMFIT demonstrated that the rate constants for the formation of oligo(A)s increased in the order of 2-mer < 3-mer < 4-mer ... < 7-mer (Kawamura and Ferris, 1994). A decameric primer, dA(pdA)8pA bound to montmorillonite was elongated to contain up to 50 monomer units by daily addition of activated monomer ImpA to the reaction mixture (Ferris, Hill and Orgel, 1996). Analysis of dimer fractions formed in the montmorillonite catalyzed reaction of binary and quaternary mixtures of ImpA, ImpC, 2-MeImpG and ImpU suggested that only a limited number of oligomers could have formed on the primitive Earth rather than equal amounts of all possible isomers (Ertem and Ferris, 2000). Formation of phosphodiester bonds between mononucleotides by montmorillonite catalysis is a fascinating discovery, and a significant step forward in efforts to find out how the first RNA-like oligomers might have formed in the course of chemical evolution. However, as has been pointed out in several publications, these systems should be regarded as models rather than a literal representation of prebiotic chemistry (Orgel, 1998; Joyce and Orgel, 1999; Schwartz, 1999).     

The Origin of Genetic Code and Translation in the Framework of Current Concepts on the Origin of Life

Biochemistry (Moscow) - The origin of genetic code and translation system is probably the central and most difficult problem in the investigations on the origin of life and one of the most complex...     

RNA Folding Argues Against a Hot-Start Origin of Life

Opinion is strongly divided on whether life arose on earth under hot or cold conditions, the hot-start and cold-start scenarios, respectively. The origin of life close to deep thermal vents appears as the majority opinion among biologists, but there is considerable biochemical evidence that high temperatures are incompatible with an RNA world. To be functional, RNA has to fold into a three-dimensional structure. We report both theoretical and experimental results on RNA folding and show that (as expected) hot conditions strongly reduce RNA folding. The theoretical results come from energy-minimization calculations of the average extent of folding of RNA, mainly from 0–90°C, for both random sequences and tRNA sequences. The experimental results are from circular-dichroism measurements of tRNA over a similar range of temperatures. The quantitative agreement between calculations and experiment is remarkable, even to the shape of the curves indicating the cooperative nature of RNA folding and unfolding. These results provide additional evidence for a lower temperature stage being necessary in the origin of life. Received: 1 March 2000 / Accepted: 14 June 2000     

The Origin of Cellular Life and Biosemiotics

Recent successes of systems biology clarified that biological functionality is multilevel. We point out that this fact makes it necessary to revise popular views about macromolecular functions and distinguish between local, physico-chemical and global, biological functions. Our analysis shows that physico-chemical functions are merely tools of biological functionality. This result sheds new light on the origin of cellular life, indicating that in evolutionary history, assignment of biological functions to cellular ingredients plays a crucial role. In this wider picture, even if aggregation of chance mutations of replicator molecules and spontaneously self-assembled proteins led to the formation of a system identical with a living cell in all physical respects but devoid of biological functions, it would remain an inanimate physical system, a pseudo-cell or a zombie-cell but not a viable cell. In the origin of life scenarios, a fundamental circularity arises, since if cells are the minimal units of life, it is apparent that assignments of cellular functions require the presence of cells and vice versa. Resolution of this dilemma requires distinguishing between physico-chemical and biological symbols as well as between physico-chemical and biological information. Our analysis of the concepts of symbol, rule and code suggests that they all rely implicitly on biological laws or principles. We show that the problem is how to establish physico-chemically arbitrary rules assigning biological functions without the presence of living organisms. We propose a solution to that problem with the help of a generalized action principle and biological harnessing of quantum uncertainties. By our proposal, biology is an autonomous science having its own fundamental principle. The biological principle ought not to be regarded as an emergent phenomenon. It can guide chemical evolution towards the biological one, progressively assigning greater complexity and functionality to macromolecules and systems of macromolecules at all levels of organization. This solution explains some perplexing facts and posits a new context for thinking about the problems of the origin of life and mind.     

Origin of Life and Definition of Life,from Buffon to Oparin

Many theories on origin of life at the end of the XIXth century and the beginning of the XXth, generally use conceptions of life instead of explicit definitions of life. This paper presents ideas on the origin of life as studied by Buffon (1707–1788), Lamarck (1744–1829), Darwin (1809–1882), Huxley (1825–1895), Oparin (1894–1980) and Haldane (1892–1964). We show that their conceptions on the evolution of matter and life reveal their conceptions of life rather than their definitions of life.     

Ice And The Origin Of Life

Sea ice occurs abundantly at the polar caps of the Earth and, probably, of many other planets. Its static and dynamic properties that may be important for prebiotic and early biotic reactions are described. It concentrates substrates and has many features that are important for catalytical actions. We propose that it provided optimal conditions for the early replication of nucleic acids and the RNA world. We repeated a famous prebiotic experiment, the poly-uridylic acid-instructed synthesis of polyadenylic acid from adenylic acid imidazolides in artificial sea ice, simulating the dynamic variability of real sea ice by cyclic temperature variation. Poly(A) was obtained in high yield and reached nucleotide chain lengths up to 400 containing predominantly 3′→ 5′ linkages.