Geochemical influences on nonenzymatic oligomerization of prebiotically relevant cyclic nucleotides

Abstract

The spontaneous emergence of long RNA molecules on the early Earth, a phenomenon central to the RNA World hypothesis, continues to remain an enigma in the field of origins of life. Few studies have looked at the nonenzymatic oligomerization of cyclic mononucleotides under neutral to alkaline conditions, albeit in fully dehydrated state. In this study, we systematically investigated the oligomerization of cyclic nucleotides under prebiotically relevant conditions, wherein starting reactants were subjected to repeated dehydration-rehydration (DH-RH) regimes. DH-RH conditions, a recurring geological theme that was prevalent on prebiotic Earth, are driven by naturally occurring processes including diurnal cycles and tidal pool activity. These conditions have been shown to facilitate uphill oligomerization reactions. The polymerization of 2 ′ ′ ′ ′ ′ -3 ′ ′ ′ ′ ′ and 3 ′ ′ ′ ′ ′ -5 ′ ′ ′ ′ ′ cyclic nucleotides of a purine (adenosine) and a pyrimidine (cytidine) was investigated. Additionally, the effect of amphiphiles was also evaluated. Furthermore, to discern the effect of "realistic" conditions on this process, the reactions were also performed using a hot spring water sample from a candidate early Earth environment. Our study showed that the oligomerization of cyclic nucleotides under DH-RH conditions resulted in intact informational oligomers. Amphiphiles increased the stability of both the starting monomers and the resultant oligomers in selected reactions. In the hot spring reactions, both the oligomerization of nucleotides and the back hydrolysis of the resultant oligomers were pronounced. Altogether, this study demonstrates how nonenzymatic oligomerization of cyclic nucleotides, under both laboratory-simulated prebiotic conditions and in a candidate early Earth environment, could have resulted in RNA oligomers of a putative RNA World.

Influence of Wet–Dry Cycling on the Self‐Assembly and Physicochemical Properties of Model Protocellular Membrane Systems

“…Therefore, in future studies, it would be important to look at changes in membrane lamellarity as a function of wet‐dry cycles. Previous studies have demonstrated that multiple wet‐dry cycles result in the oligomerization of monomers such as nucleotides and amino acids [10–18] . When vesicles reform, the oligomers can get encapsulated within these vesicles forming protocellular entities.…”

“…Fluctuating environments on the prebiotic Earth, driven by thermal evaporation, geyser activity, rainfall etc., give rise to wet‐dry cycles [8,9] . Such naturally recurring wet‐dry cycles have been demonstrated to promote formation of different building blocks of life, e. g., oligoesters, [10,11] oligopeptides, [12,13] nucleotides [14,15] and oligonucleotides [16–18] etc. High temperature in these niches induces water loss, which tends to concentrate dilute solutions and promote thermodynamically uphill condensation reactions [8,9] .…”

Porphyrin in Prebiotic Catalysis: Ascertaining a Route for the Emergence of Early Metalloporphyrins**

“…Based on the above observations, we set out to investigate the ability of metal ions to coordinate with TPPS and discern if metal‐coordinated TPPS (M‐TPPS) complexes could result under prebiotically plausible terrestrial geothermal conditions. In addition to being widely considered as a niche pertinent to discerning the emergence of life on the early Earth, these prebiotic settings have previously been shown to facilitate the formation of biopolymers relevant to extant biochemistry [50–54] . Towards this, aqueous solution containing 0.3 mM metal ions and 0.03 mM (ten times lower than metal ion) TPPS was incubated at 70° C, simulating putative early Earth conditions [55] (details in Experimental Section).…”

“…In addition to being widely considered as a niche pertinent to discerning the emergence of life on the early Earth, these prebiotic settings have previously been shown to facilitate the formation of biopolymers relevant to extant biochemistry. [50][51][52][53][54] Towards this, aqueous solution containing 0.3 mM metal ions and 0.03 mM (ten times lower than metal ion) TPPS was incubated at 70°C, simulating putative early Earth conditions [55] (details in Experimental Section). Metal coordination with the TPPS scaffold was monitored at specific time points using the temporal change observed in the UV absorption spectrum and steady-state fluorescence spectroscopy (Supporting Information Figures S11-22).…”

RNA polymerisation without catalyst from 2’,3’-cyclic nucleotides by drying at air-water interfaces

“…Our observations of cAMP and cUMP forming up to trimers are consistent with literature. [27,28] The polymerisation is demonstrated in the presence of bulk water at the air-water interface, within a microfluidic thermal chamber. The chamber mimics conditions of a heated, water filled volcanic rock pore that includes a gas bubble.…”