Very recommendable! Amazing stuff!
"... Currently, the leading hypothesis within the scientific community is that life developed from RNA molecules, known for their self-replication ability. Yet for the past two decades, Prof. Doron Lancet, of the Weizmann Institute of Science’s Molecular Genetics Department, has been swimming against the currents of the primordial soup. “It is highly improbable that the origin of life traces back to a single complex molecule such as RNA,” says Lancet, “but more likely to assemblies of simple chemical compounds that can form spontaneously and reproduce as a whole.” ...
RNA molecules that are able to replicate consist of tens, and often hundreds, of discrete molecular units organized linearly. These units, in turn, are assumed to be distilled from a milieu containing millions of other different molecules, a next to impossible feat. ...
RNA molecules that are able to replicate consist of tens, and often hundreds, of discrete molecular units organized linearly. These units, in turn, are assumed to be distilled from a milieu containing millions of other different molecules, a next to impossible feat. ...
The molecular ensembles proposed by Lancet as the earliest reproducible entities are called micelles – nano-scale spheres the size of viruses, composed of lipid molecules. These possess a unique property: They are made up of a water-“loving” head, and a water-“hating” tail. This arrangement enables lipids to perform their task as the principal structural component of the membranes that surround every living cell, as well as to form into significantly smaller micellar structures.
... it has been demonstrated that lipid molecules could have formed on ancient Earth and may even have arrived here carried on meteorites. Previous studies by Lancet have further provided evidence that micellar structures, unlike RNA, could have readily formed spontaneously in the chaotic primordial environment.
For lipid micelles to be considered candidates for the origin of life, they must show catalytic properties, namely, a capacity for speeding up reaction processes. In their first paper, the researchers present comprehensive evidence for just that: diverse instances of lipid catalysis. These findings, derived unexpectedly from the chemical industry, support the notion that micelles can indeed mimic present-day cells. The researchers also surveyed studies that implemented Lancet’s computational model to predict the behavior of lipids under a variety of conditions. These studies demonstrate that micelles can create copies of their molecular composition as they develop – and later on split – which is reminiscent of how cells behave. ...
Given that micellar replication is error prone – similar in a way to how DNA acquires spontaneous, random mutations – it could drive forward evolutionary processes. The researchers address this aspect as well by introducing new routes by which micelles could have evolved to gradually become more complex, toward becoming what are known as protocells – simple precursors of modern cells. In the second paper, the scientists provide further biochemical evidence that chemical groups, attached to the water-“loving” surface of micelles, may form molecular recognition sites, comparable to those found in present-day proteins. ..."
For lipid micelles to be considered candidates for the origin of life, they must show catalytic properties, namely, a capacity for speeding up reaction processes. In their first paper, the researchers present comprehensive evidence for just that: diverse instances of lipid catalysis. These findings, derived unexpectedly from the chemical industry, support the notion that micelles can indeed mimic present-day cells. The researchers also surveyed studies that implemented Lancet’s computational model to predict the behavior of lipids under a variety of conditions. These studies demonstrate that micelles can create copies of their molecular composition as they develop – and later on split – which is reminiscent of how cells behave. ...
Given that micellar replication is error prone – similar in a way to how DNA acquires spontaneous, random mutations – it could drive forward evolutionary processes. The researchers address this aspect as well by introducing new routes by which micelles could have evolved to gradually become more complex, toward becoming what are known as protocells – simple precursors of modern cells. In the second paper, the scientists provide further biochemical evidence that chemical groups, attached to the water-“loving” surface of micelles, may form molecular recognition sites, comparable to those found in present-day proteins. ..."
From the abstract (1):
"... This postulate gains considerable support from experiments describing micellar catalysis and autocatalytic proliferation, and, more recently, from reports on cross-catalysis in mixed micelles that lead to life-like steady-state dynamics. Such results, along with evidence for micellar prebiotic compatibility, synergize with predictions of our chemically stringent computer-simulated model, illustrating how mutually catalytic lipid networks may enable micellar compositional reproduction that could underlie primal selection and evolution. Finally, we highlight studies on how endogenously catalysed lipid modifications could guide further protocellular complexification, including micelle to vesicle transition and monomer to biopolymer progression. These portrayals substantiate the possibility that protocellular evolution could have been seeded by pre-RNA lipid assemblies."
From the abstract (2):
"A widespread dogma asserts that life could not have emerged without biopolymers – RNA and proteins. However, the widely acknowledged implausibility of a spontaneous appearance and proliferation of these complex molecules in primordial messy chemistry casts doubt on this scenario. A proposed alternative is “Lipid-First”, based on the evidence that lipid assemblies may spontaneously emerge in heterogeneous environments, and are shown to undergo growth and fission, and to portray autocatalytic self-copying. What seems undecided is whether lipid assemblies have protein-like capacities for stereospecific interactions, a sine qua non of life processes. This Viewpoint aims to alleviate such doubts, pointing to growing experimental evidence that lipid aggregates possess dynamic surface configurations capable of stereospecific molecular recognition. Such findings help support a possible key role of lipids in seeding life's origin."
1) Self-reproducing catalytic micelles as nanoscopic protocell precursors (no public access)
2) Dynamic lipid aptamers: non-polymeric chemical path to early life (open access)
No comments:
Post a Comment