The self-assembly of prebiotically plausible amphiphiles
(fatty
acids) to form a bilayer membrane for compartmentalization is an important
factor during protocellular evolution. Such fatty acid-based membranes
assemble at relatively high concentrations, and they lack robust stability.
We have demonstrated that a mixture of lipidated lysine (cationic)
and prebiotic fatty acids (decanoic acid, anionic) can form protocellular
membranes (amino acid-based membranes) at low concentrations via electrostatic,
hydrogen bonding, and hydrophobic interactions. The formation of vesicular
membranes was characterized by dynamic light scattering (DLS), pyrene
and Nile Red partitioning, cryo-transmission electron microscopy (TEM)
images, and glucose encapsulation studies. The lipidated nonproteinogenic
analogues of lysine (Lys), such as ornithine (Orn) and 2,4-diaminobutyric
acid (Dab), also form membranes with decanoate (DA). Time-dependent
turbidimetric and 1H NMR studies suggested that the Lys-based
membrane is more stable than the membranes prepared from nonproteinogenic
lower analogues. The Lys-based membrane embeds a model acylating agent
(aminoacyl-tRNA mimic) and facilitates the colocalization of substrates
to support regioselective peptide formation via the α-amine
of Lys. These membranes thereby assist peptide formation and control
the positioning of the reactants (model acylating agent and −NH2 of amino acids) to initiate biologically relevant reactions
during early evolution.
A positively charged micelle, loaded with substrates was transported selectively to the reaction site (cathode) to promote the proximity and localization of the reactants (ester and hydroxide). The guided vehicular...
Templated assembly of small molecules into nano-structural architectures has been used extensively by nature throughout its evolution. These systems were also studied in artificial systems to design phosphate templated assembly....
Protocellular surface formation via the self-assembly of amphiphiles, and catalysis by simple peptides/proto-RNA are two important pillars of the evolution of protocells. To hunt for prebiotic self-assembly-supported catalytic reactions, we...
Prebiotic membranes are one of the essential elements
of the origin
of life because they build compartments to keep genetic materials
and metabolic machinery safe. Since modern cell membranes are made
up of ethanolamine-based phospholipids, prebiotic membrane formation
with ethanolamine-based amphiphiles and phosphates might act as a
bridge between the prebiotic and contemporary eras. Here, we report
the prebiotic synthesis of O-lauroyl ethanolamine
(OLEA), O-lauroyl methyl ethanolamine (OLMEA), and O-lauroyl dimethylethanolamine (OLDMEA) under wet–dry
cycles. Turbidimetric, NMR, DLS, fluorescence, microscopy, and glucose
encapsulation studies highlighted that OLEA-ATP and OLMEA-ATP form
protocellular membranes in a 3:1 ratio, where ATP acts as a template.
OLDMEA with a dimethyl group did not form any membrane in the presence
of ATP. ADP can also template OLEA to form vesicles in a 2:1 ratio,
but the ADP-templated vesicles were smaller. This suggests the critical
role of the phosphate backbone in controlling the curvature of supramolecular
assembly. The mechanisms of hierarchical assembly and transient dissipative
assembly are discussed based on templated-complex formation via electrostatic,
hydrophobic, and H-bonding interactions. Our results suggest that N-methylethanolamine-based amphiphiles could be used to
form prebiotic vesicles, but the superior H-bonding ability of the
ethanolamine moiety likely provides an evolutionary advantage for
stable protocell formation during the fluctuating environments of
early earth.
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