Other
Scientific paper
Feb 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007oleb...37...27d&link_type=abstract
Origins of Life and Evolution of Biospheres, Volume 37, Issue 1, pp.27-45
Other
Iron Sulfide Minerals, Primitive Seawater-Sulfides Interfaces, Acidic &Rarr, Alkaline Transitions, Phosphate Capture And Release Mechanisms, Modulation Of Phosphate Availability In Primitive Scenarios, Phosphorylation Reactions
Scientific paper
Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affected by hydrothermal emissions, reveal that acidic conditions favour P i sorption whereas mild alkaline media as well as those simulating sulfur oxidation to SO2- 4 revert this capture process. Several mechanisms relevant to P i availability in prebiotic eras are implicated in the modulation of these processes. Those favouring sorption are: (a) hydrophobic coating of molecules, such as acetate that could be formed in the vicinity of hydrothermal vents; (b) water and Mg2+ bridging in the interface mineral-aqueous media; (c) surface charge neutralization by monovalent cations (Na+ and K+). The increase of both the medium pH and the SO2- 4 trapping by the mineral interface would provoke the release of sorbed P i due to charge polarization. Moreover it is shown that P i self-modulates its sorption, a mechanism that depends on the abundance of SO2- 4 in the interface. The relevance of the proposed mechanisms of P i capture, release and trapping arises from the need of abundant presence of this molecule for primitive phosphorylations, since similarly to contemporary aqueous media inorganic phosphate concentrations in primitive seas should have been low. It is proposed that the presence of sulphide minerals with high affinity to P i could have trapped this molecule in an efficient manner, allowing its concentration in specific niches. In these niches, the conditions studied in the present work would have been relevant for its availability in soluble form, specially in primitive insulated systems with pH gradients across the wall.
Bonapace José A. P.
Braz-Levigard Raphael
Ching-San Yonder
de Souza-Barros Fernando
Monte Marisa B. M.
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