Informational polymers in the primitive Earth: Lempel-Ziv complexity and Entropy of tRNAs in anaerobic Archea compared to computer-generated random data

摘要

In a possible scenario for the origin of life there was a time in which informational genetic polymers played primary roles. Transfer-RNA molecules may be considered possible "fossils" of that primitive era (billions years ago). In order to test the hypothesis that the nucleotide sequences of the primitive informational polymers might not be chosen randomly, we propose a comparison of computer-generated random sequences with tRNAs nucleotide sequences present in anaerobic Archaea. Random sequence data were obtained from the algorithm by Press and Teukolsky. Relative Lempel-Ziv complexity and Entropy of nucleotide sequences and of computer-generated random data represented as random walks were evaluated. Manhattan and Euclidean "fractal" dimensions (DM, DE) were also evaluated. Nonlinear parameters obtained from the Archaea are lower than the values of randomly generated sequences (p<0.01, p<0.01). DM and DE confirm the results (p<0.01, p<0.01). The observed deviation from pure randomness should bearisen from some constraints like the secondary structure of this biologic macromolecule and/or from a "frozen" stochastic transition when informational polymers originated. The nonlinear evaluation of nucletoide sequences expressed as random walk, herepresented, provides an efficient assessment of the primary structure of nucleic acid sequences.