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Spontaneous Emergence of Membrane-Forming Protoamphiphiles from a Lipid-Amino Acid Mixture Under Wet-Dry Cycles
ChemRxiv Pub Date : 2020-10-19
Manesh Joshi, Anupam Sawant, Sudha Rajamani

The prelude to the origin of cellular life on Earth would have involved a fundamental step, that of protocell formation. This involves the coming together of two crucial processes; abiotic synthesis of informational and catalytic polymers, and the assembly of membrane compartments. Mutual interactions between these processes would have likely affected the emergence and early stages of protocell evolution. Previous investigations have predominantly focused on cooperative interactions, often neglecting any competitive behavior that might ensue as ‘counterproductive cross-talk’. However, in a realistic scenario, both cooperative and competitive reactions would have occurred simultaneously in a complex prebiotic soup, generating a plethora of chemical species with their own prebiotic implications. In this study, we followed a systematic and unbiased approach to explore this interdependence. We used a lipid-amino acid system to demonstrate the above-mentioned phenomenon wherein we investigated the effect of a membrane-forming amphiphile on peptide synthesis, under prebiotically plausible conditions. Interestingly, our study shows the formation of a hitherto unobserved reaction product that could have played a significant role during the emergence of life on the early Earth. We do show that peptide synthesis occurs but with a decrease in the yield. This is due to another concurrent and competing reaction, wherein an amino acid covalently interacts with a phospholipid to generate new amphiphilic species called N-acyl amino acids (NAAs) via an ester-amide exchange process. These NAAs are thermostable and, hence, persistent even at high temperatures. Furthermore, this protoamphiphile is also able to self-assemble into vesicles at acidic pH. Au contraire, fatty acids, a widely accepted constituent of prebiotic compartments, have been shown to generate vesicles only at neutral to alkaline pH. Thus, NAAs could have had a selective advantage over fatty acids to form thermostable protocell compartments under acidic geothermal pool-like conditions, a niche that has gained prominence as one of the important geological settings where life could have originated. Our study underlines the importance of an unbiased exploration of the complex interactions between prebiotic processes, which could potentially open new avenues to solving the origin of life conundrum.

中文翻译:

干湿循环下脂质-氨基酸混合物中形成膜的两亲物的自发出现。

地球细胞生命起源的前奏将涉及一个基本步骤,即原始细胞的形成。这涉及到两个关键过程的融合。信息和催化聚合物的非生物合成,以及膜室的组装。这些过程之间的相互影响可能会影响原始细胞进化的出现和早期阶段。先前的调查主要集中于合作性互动,通常忽略了可能会导致“反生产性串扰”的竞争行为。但是,在现实情况下,复杂的益生元汤中会同时发生合作和竞争反应,从而产生大量具有自身益生元含义的化学物种。在这个研究中,我们遵循一种系统而公正的方法来探索这种相互依存关系。我们使用脂质-氨基酸系统来证明上述现象,其中我们研究了在益生元合理的条件下成膜两亲物对肽合成的影响。有趣的是,我们的研究表明,迄今未观察到的反应产物的形成可能在地球早期生命的出现过程中发挥了重要作用。我们确实显示出发生了肽合成,但是产率降低了。这是由于另一个同时发生的竞争反应,其中氨基酸与磷脂共价相互作用,通过酯-酰胺交换过程生成称为N-酰基氨基酸(NAA)的新两亲性物质。这些NAA是热稳定的,因此即使在高温下也可以持久存在。此外,该原两亲物还能够在酸性pH下自组装成囊泡。相反,脂肪酸已被广泛认可为益生元区室的组成部分,仅在中性至碱性pH值时才产生囊泡。因此,在酸性地热池状条件下,NAA可能比脂肪酸具有选择性优势,可以形成热稳定的原生细胞隔室,而这种利基已经成为生命起源的重要地质环境之一,而这一地位已得到重视。我们的研究强调了对益生元过程之间的复杂相互作用进行无偏探索的重要性,这可能为解决生命难题的根源开辟新途径。益生元区室的一种广泛接受的成分,已显示仅在中性至碱性pH值时才产生囊泡。因此,在酸性地热池状条件下,NAA可能比脂肪酸具有选择性优势,可以形成热稳定的原生细胞隔室,而这种利基已经成为生命起源的重要地质环境之一,而这一地位已得到重视。我们的研究强调了对益生元过程之间的复杂相互作用进行无偏探索的重要性,这可能为解决生命难题的根源开辟新途径。益生元区室的一种广泛接受的成分,已显示仅在中性至碱性pH值时才产生囊泡。因此,在酸性地热池状条件下,NAA可能比脂肪酸具有选择性优势,可以形成热稳定的原生细胞隔室,而这种利基已经成为生命起源的重要地质环境之一,而这一地位已得到重视。我们的研究强调了对益生元过程之间的复杂相互作用进行无偏探索的重要性,这可能为解决生命难题的根源开辟新途径。作为一种可能起源于生命的重要地质环境之一,这一小生境已倍受关注。我们的研究强调了对益生元过程之间的复杂相互作用进行无偏探索的重要性,这可能为解决生命难题的根源开辟新途径。作为一种可能起源于生命的重要地质环境之一,这一小生境已倍受关注。我们的研究强调了对益生元过程之间的复杂相互作用进行无偏探索的重要性,这可能为解决生命难题的根源开辟新途径。
更新日期:2020-10-19
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