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Thread: Peptides can form naturally without amino acids

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    Peptides can form naturally without amino acids

    An important advancement in the science of abiogenesis demonstrates how Peptides can form naturally without amino acids making peptides from energy-rich aminonitriles. This could potentially solve the amino acid’s being unable to randomly bond well in water issue. As also suggested from the link were struggles with the central focus on only amino acids.

    Source: https://www.sciencedaily.com/releases/2019/07/190710132019.htm?utm_source=dlvr.it&utm_medium=facebook



    Origin of life insight: Peptides can form without amino acids

    Summary:
    Peptides, one of the fundamental building blocks of life, can be formed from the primitive precursors of amino acids under conditions similar to those expected on the primordial Earth, finds a new study.


    Peptides, one of the fundamental building blocks of life, can be formed from the primitive precursors of amino acids under conditions similar to those expected on the primordial Earth, finds a new UCL study.

    The findings, published in Nature, could be a missing piece of the puzzle of how life first formed.

    "Peptides, which are chains of amino acids, are an absolutely essential element of all life on Earth. They form the fabric of proteins, which serve as catalysts for biological processes, but they themselves require enzymes to control their formation from amino acids," explained the study's lead author, Dr Matthew Powner (UCL Chemistry).

    "So we've had a classic chicken-and-egg problem -- how were the first enzymes made?"

    He and his team have demonstrated that the precursors to amino acids, called aminonitriles, can be easily and selectively turned into peptides in water, taking advantage of their own built-in reactivity with the help of other molecules that were present in primordial environments.

    "Many researchers have sought to understand how peptides first formed to help life develop, but almost all of the research has focused on amino acids, so the reactivity of their precursors was overlooked," said Dr Powner.

    The precursors, aminonitriles, require harsh conditions, typically strongly acidic or alkaline, to form amino acids. And then amino acids must be recharged with energy to make peptides. The researchers found a way to bypass both of these steps, making peptides directly from energy-rich aminonitriles.

    They found that aminonitriles have the innate reactivity to achieve peptide bond formation in water with greater ease than amino acids. The team identified a sequence of simple reactions, combining hydrogen sulfide with aminonitriles and another chemical substrate ferricyanide, to yield peptides.

    "Controlled synthesis, in response to environmental or internal stimuli, is an essential element of metabolic regulation, so we think that peptide synthesis could have been part of a natural cycle that took place in the very early evolution of life," said Pierre Canavelli, the first author of the study who completed it while at UCL.

    The molecules that served as substrates to help the formation of the amide bonds in the experiments are outgassed during volcanism and are all likely to have been present on the early Earth.

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    Last edited by shunyadragon; 07-12-2019 at 05:58 AM.
    Glendower: I can call spirits from the vasty deep.
    Hotspur: Why, so can I, or so can any man;
    But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

    go with the flow the river knows . . .

    Frank

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    tWebber shunyadragon's Avatar
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    The more technical reference is here:

    Source: https://www.nature.com/articles/s41586-019-1371-4



    Peptide ligation by chemoselective aminonitrile coupling in water

    Pierre Canavelli, Saidul Islam & Matthew W. Powner
    Nature (2019)

    Abstract

    Amide bond formation is one of the most important reactions in both chemistry and biology1,2,3,4, but there is currently no chemical method of achieving α-peptide ligation in water that tolerates all of the 20 proteinogenic amino acids at the peptide ligation site. The universal genetic code establishes that the biological role of peptides predates life’s last universal common ancestor and that peptides played an essential part in the origins of life5,6,7,8,9. The essential role of sulfur in the citric acid cycle, non-ribosomal peptide synthesis and polyketide biosynthesis point towards thioester-dependent peptide ligations preceding RNA-dependent protein synthesis during the evolution of life5,9,10,11,12,13. However, a robust mechanism for aminoacyl thioester formation has not been demonstrated13. Here we report a chemoselective, high-yielding α-aminonitrile ligation that exploits only prebiotically plausible molecules—hydrogen sulfide, thioacetate12,14 and ferricyanide12,14,15,16,17 or cyanoacetylene8,14—to yield α-peptides in water. The ligation is extremely selective for α-aminonitrile coupling and tolerates all of the 20 proteinogenic amino acid residues. Two essential features enable peptide ligation in water: the reactivity and pKaH of α-aminonitriles makes them compatible with ligation at neutral pH and N-acylation stabilizes the peptide product and activates the peptide precursor to (biomimetic) N-to-C peptide ligation. Our model unites prebiotic aminonitrile synthesis and biological α-peptides, suggesting that short N-acyl peptide nitriles were plausible substrates during early evolution.

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    Glendower: I can call spirits from the vasty deep.
    Hotspur: Why, so can I, or so can any man;
    But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

    go with the flow the river knows . . .

    Frank

    I do not know, therefore everything is in pencil.

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