Vesicles protect activated acetic acid

Prebiotic Peptide Synthesis: How Did Longest Peptide Appear?

The origin of proteins is a fundamental question in the study of the origin of life. Peptides, as the building blocks of proteins, necessarily preceded the first proteins in prebiotic chemical evolution. Prebiotic peptides may have also played crucial roles in early life's evolution, contributing to self-catalysis, interacting with nucleic acids, and stabilizing primitive cell compartments. Longer and more complicated prebiotic peptides often have greater structural flexibility and functional potential to support the emergence and evolution of early life. Since the Miller-Urey experiment demonstrated that amino acids can be synthesized in a prebiotic manner, the prebiotic synthesis route of peptides has garnered increasing attention from researchers. However, it is difficult for amino acids to condense into peptides in aqueous solutions spontaneously. Over the past few decades, researchers have explored various routes of prebiotic peptide synthesis in the plausible prebiotic Earth environment, such as thermal polymerization, clay mineral catalysis, wet-dry cycles, condensing agents, and lipid-mediated. This paper reviews advancements in prebiotic peptide synthesis research and discusses the conditions that may have facilitated the emergence of longer peptides.

Origin of Life on Mars: Suitability and Opportunities

Although the habitability of early Mars is now well established, its suitability for conditions favorable to an independent origin of life (OoL) has been less certain. With continued exploration, evidence has mounted for a widespread diversity of physical and chemical conditions on Mars that mimic those variously hypothesized as settings in which life first arose on Earth. Mars has also provided water, energy sources, CHNOPS elements, critical catalytic transition metal elements, as well as B, Mg, Ca, Na and K, all of which are elements associated with life as we know it. With its highly favorable sulfur abundance and land/ocean ratio, early wet Mars remains a prime candidate for its own OoL, in many respects superior to Earth. The relatively well-preserved ancient surface of planet Mars helps inform the range of possible analogous conditions during the now-obliterated history of early Earth. Continued exploration of Mars also contributes to the understanding of the opportunities for settings enabling an OoL on exoplanets. Favoring geochemical sediment samples for eventual return to Earth will enhance assessments of the likelihood of a Martian OoL.

Ingredients for microbial life preserved in 3.5 billion-year-old fluid inclusions

It is widely hypothesised that primeval life utilised small organic molecules as sources of carbon and energy. However, the presence of such primordial ingredients in early Earth habitats has not yet been demonstrated. Here we report the existence of indigenous organic molecules and gases in primary fluid inclusions in c. 3.5-billion-year-old barites (Dresser Formation, Pilbara Craton, Western Australia). The compounds identified (e.g., H₂S, COS, CS₂, CH₄, acetic acid, organic (poly-)sulfanes, thiols) may have formed important substrates for purported ancestral sulfur and methanogenic metabolisms. They also include stable building blocks of methyl thioacetate (methanethiol, acetic acid) – a putative key agent in primordial energy metabolism and thus the emergence of life. Delivered by hydrothermal fluids, some of these compounds may have fuelled microbial communities associated with the barite deposits. Our findings demonstrate that early Archaean hydrothermal fluids contained essential primordial ingredients that provided fertile substrates for earliest life on our planet.

It is widely hypothesised that primeval life utilized small organic molecules as sources of carbon and energy, however, the presence of such primordial ingredients in early Earth habitats has not yet been demonstrated. Here the authors report the existence of indigenous organic molecules and gases in primary fluid inclusions in c. 3.5- billion-year-old rocks from Western Australia.

Fatty acids' double role in the prebiotic formation of a hydrophobic dipeptide

In search of a connection between prebiotic peptide chemistry and lipid compartments, the reaction of a 5(4H)-oxazolone with leucinamide was extensively explored under buffered aqueous conditions, where diverse amphiphiles and surfactants could form supramolecular assemblies. Significant increases in yield and changes in stereoselectivity were observed when fatty acids exceeded their critical aggregation concentration, self-assembling into vesicles in particular. This effect does not take place below the fatty acid solubility limit, or when other anionic amphiphiles/surfactants are used. Data from fluorimetric and Langmuir trough assays, complementary to the main HPLC results reported here, demonstrate that the dipeptide product co-localizes with fatty acid bilayers and monolayers. Additional experiments in organic solvents suggest that acid-base catalysis operates at the water-aggregate interface, linked to the continuous proton exchange dynamics that fatty acids undergo at pH values around their effective pK_a. These simple amphiphiles could therefore play a dual role as enhancers of peptide chemistry under prebiotic conditions, providing soft and hydrophobic organic domains through self-assembly and actively inducing catalysis at their interface with the aqueous environment. Our results support a systems chemistry approach to life's origin.

Current Ideas about Prebiological Compartmentalization

Contemporary biological cells are highly sophisticated dynamic compartment systems which separate an internal volume from the external medium through a boundary, which controls, in complex ways, the exchange of matter and energy between the cell's interior and the environment. Since such compartmentalization is a fundamental principle of all forms of life, scenarios have been elaborated about the emergence of prebiological compartments on early Earth, in particular about their likely structural characteristics and dynamic features. Chemical systems that consist of potentially prebiological compartments and chemical reaction networks have been designed to model pre-cellular systems. These systems are often referred to as "protocells". Past and current protocell model systems are presented and compared. Since the prebiotic formation of cell-like compartments is directly linked to the prebiotic availability of compartment building blocks, a few aspects on the likely chemical inventory on the early Earth are also summarized.