NAI
2010 Annual Science Report
University of Hawaii, Manoa
Reporting | SEP 2009 – AUG 2010
Amino Acid Alphabet Evolution
Project Summary
A standard “alphabet” of just 20 amino acids builds the proteins that interact to form metabolism of all life on Earth (rather like the English of 26 letters can be linked into words that interact in sentences and paragraphs to produce meaningful writing). However, considerable research from many scientific disciplines points to the idea that many other amino acids are made by non-biological processes throughout the universe. A natural question is why did life on our planet “choose” the members of its standard alphabet?
Our project seeks to gather and organize the diverse information that describes these non-biological amino acids, to understand their properties and potential for making proteins and thus to understand better whether the biology that we know is a clever, predictable solution to making biology – or just one of countless possible solutions that may exist elsewhere.
Project Progress
We have performed a series of computational analyses that reveal highly unusual properties of life’s chosen amino acid alphabet relative to randomly selected alternative alphabets.
Put simply these analyses show a very low probability that a random selection of amino acids could exceed the range and evenness with which life’s “choice” represents the physicochemical properties of size, charge and hydrophobicity.
We have shown this result holds true for the start point of genetic coding (a smaller alphabet of <20 amino acids), how it grew, and how it ended up (as a collection of 20 amino acids) based on the picture of prebiotic availability provided by the Murchison meteorite.
We have written up this work and submitted for publication within Astrobiology journal. We have also initiated research that expands these analyses to a broader picture of prebiotic availability – based on spark discharge experiments and meta-analyses of prebiotic simulations.
Publications
- Freeland, S. & Philip, G.K. (2010). What Can the Origin of Life on Earth Tell Us About the Cosmos? Journal of Cosmology, 10: 3408-3417.
- Freeland, S. (2009). Terrestrial amino acids and their evolution. In: Hughes, A.B. (Eds.). Amino Acids, Peptides and Proteins in Organic Chemistry. Vol. 1. Wiley, Weinheim.
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PROJECT INVESTIGATORS:
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PROJECT MEMBERS:
Stephen Freeland
Project Investigator
Gayle Philip
Collaborator
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RELATED OBJECTIVES:
Objective 1.1
Formation and evolution of habitable planets.
Objective 3.1
Sources of prebiotic materials and catalysts
Objective 3.2
Origins and evolution of functional biomolecules
Objective 3.4
Origins of cellularity and protobiological systems
Objective 4.1
Earth's early biosphere.
Objective 4.3
Effects of extraterrestrial events upon the biosphere
Objective 6.2
Adaptation and evolution of life beyond Earth
Objective 7.1
Biosignatures to be sought in Solar System materials
Objective 7.2
Biosignatures to be sought in nearby planetary systems