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The Biogeochemistry of Sulfur in Hydrothermal SystemsThe incorporation of sulfur into many biomolecules likely dates back to the development of the earliest metabolic strategies. Sulfur is common in enzymes and co-enzymes and is an indispensable structural component in many peptides and proteins. Early metabolism may have been heavily influenced by the abundance of sulfide minerals in hydrothermal systems. The incorporation of sulfur into many biomolecules likely dates back to the development of the earliest metabolic strategies. Sulfur is common in enzymes and co-enzymes and is an indispensable structural component in many peptides and proteins. Early metabolism may have been heavily influenced by the abundance of sulfide minerals in hydrothermal systems. Understanding how sulfur became prevalent in biochemical processes and many biomolecules requires knowledge of the reaction properties of sulfur-bearing compounds. We have previously estimated thermodynamic data for thiols, the simplest organic sulfur compounds, at elevated temperatures and pressures. If life began in hydrothermal environments, it is especially important to understand reactions at elevated temperatures among sulfur-bearing compounds and other organic molecules essential for the origin and persistence of life. Here we examine reactions that may have formed amino acids with thiols as reaction intermediates in hypothetical early Earth hydrothermal environments. (There are two amino acids, cysteine and methionine, that contain sulfur.) Our calculations suggest that significant amounts of some amino acids were produced in early Earth hydrothermal fluids, given reasonable concentrations H2, NH3, H2S and CO. For example, preliminary results indicate that glycine activities as high as 1 mmol can be reached in these systems at 100 C. Alanine formation from propanethiol is also a favorable reaction. On the other hand, the calculated equilibrium log activities of cysteine and serine from propanethiol are -21 and -19, respectively, at 100 C. These results indicate that while amino acid formation with thiols as intermediates is favored in some cases, other mechanisms may have been necessary to produce significant amounts of other amino acids. Coupled with our previous results for thiols, these studies imply that sulfur may have been easily incorporated into the organic geochemistry of early Earth hydrothermal systems, leading to its widespread use in biomolecules. Formation of more complex biomolecules in hydrothermal systems may have required sulfur-bearing organic compounds as reaction intermediates.
Document ID
20010091026
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Schulte, Mitchell
(NASA Ames Research Center Moffett Field, CA United States)
Rogers, K. L.
(Washington Univ. Saint Louis, MO United States)
DeVincenzi, Donald L.
Date Acquired
August 20, 2013
Publication Date
April 9, 2001
Subject Category
Life Sciences (General)
Meeting Information
Meeting: Earth Systems Processes
Location: Edinburgh
Country: United Kingdom
Start Date: June 24, 2001
End Date: June 28, 2001
Funding Number(s)
PROJECT: RTOP 344-38-00-02
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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