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Scientists have unveiled the mechanisms by which the initial cells might have originated on our planet.

Approximately 4 billion years in the past, Earth underwent changes that made it conducive for life to thrive. Researchers studying the origins of life ponder whether the chemical composition of early Earth resembled that necessary for life as we know it today. They are aware that protocells, which are spherical structures made of fats, played a crucial role as the precursors to cells during the initial stages of life on Earth. However, the question remains: how did these simple protocells come into existence and evolve to pave the way for life on our planet? Recently, scientists from Scripps Research have identified a potential pathway that explains how protocells could have initially formed and developed chemically to enable a wide range of functions.

The results, which were made available online on February 29, 2024, in the Chem journal, indicate that phosphorylation, a chemical process involving the addition of phosphate groups to molecules, may have occurred sooner than initially anticipated. This discovery suggests the formation of more complex protocells with double chains, capable of carrying out chemical reactions and dividing with a wide range of functions. By shedding light on the formation of protocells, scientists can gain insight into the potential mechanisms of early evolution.

According to Ramanarayanan Krishnamurthy, Ph.D., co-corresponding senior author and professor in the Department of Chemistry at Scripps Research, “There comes a time when we all ponder our origins. We have now identified a plausible scenario in which phosphates could have been integrated into cell-like structures earlier than previously believed, laying the groundwork for life.”

“This discovery enhances our understanding of the chemical conditions on early Earth, allowing us to delve into the origins of life and the processes through which life could have developed on ancient Earth.”

Krishnamurthy and his team are researching the chemical processes that led to the creation of simple chemicals and formations present before life emerged on prebiotic Earth. Additionally, Krishnamurthy is a co-leader of a NASA project investigating the emergence of life from these early environments.

In this investigation, Krishnamurthy and his team collaborated with Ashok Deniz, Ph.D., a soft matter biophysicist and professor at Scripps Research. They aimed to explore the potential involvement of phosphates in the formation of protocells. Phosphates play a crucial role in various chemical reactions within the body, leading Krishnamurthy to suspect their presence earlier than previously assumed.

While scientists initially believed protocells originated from fatty acids, the transition from a single chain to a double chain of phosphates, which enhances stability and enables chemical reactions, remained unclear.

To simulate plausible prebiotic conditions, the team identified three chemical mixtures capable of forming vesicles, lipid-based structures resembling protocells. These mixtures included fatty acids, glycerol, and other chemicals that could have been present on early Earth. The researchers observed the reactions, introduced additional chemicals, and subjected the solutions to cycles of cooling, heating, and shaking overnight to facilitate chemical reactions.

During the experiments, the mixtures were examined using fluorescent dyes to determine if vesicle formation had occurred. To gain a better understanding of the factors influencing vesicle formation, the researchers also varied the pH and component ratios. Additionally, they investigated the impact of metal ions and temperature on the stability of the vesicles.

According to Sunil Pulletikurti, the first author and a postdoctoral researcher in Krishnamurthy’s lab, the vesicles were observed transitioning from a fatty acid environment to a phospholipid environment. This suggests that a similar chemical environment could have existed billions of years ago.

Further analysis revealed that phosphorylation of fatty acids and glycerol may have contributed to the formation of a more stable, double chain structure. Specifically, vesicles derived from glycerol-based fatty acid esters exhibited different tolerances to metal ions, temperatures, and pH, which played a crucial role in the diversification of evolution.

Deniz, another researcher involved in the study, stated that they have identified a plausible pathway for the emergence of phospholipids during the chemical evolutionary process. This discovery sheds light on how early chemistries may have transitioned, ultimately leading to the development of life on Earth. Furthermore, it suggests the involvement of intriguing physics that played important functional roles in the evolution of modern cells.

Moving forward, the scientists plan to investigate the reasons behind vesicle fusion and division, aiming to gain a deeper understanding of the dynamic processes of protocells.

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