engleski

Nonlinear dynamics in DNA sequences

A large amount of available DNA sequences enables better analyses of the problem of existence of significant sequential correlations. The question, which is not yet settled with certainty, whether the correlations are short or long ranged can now be studied. Long-range correlations are usually characteristic of critical phenomena and of low dimensional chaotic dynamics. We study the presence of low dimensional chaos in the protein secondary structures by using the following encoding for the four nucleotides of DNA : T?(00), A? (10), G?(11) and C?(01) based purine (A, G)/pyrimidine (C, T/U) and strong (G, C)/weak (A, T/U) H-bond. The 20 amino acids are then encoded by 6 binary digits. The R/S analyses leading to the Hurst exponent which is related to the fractal dimension is performed for 10 alpha-helices and 10 beta-sheets. We find similar fractal dimension about 1.5. However, the Fourier analyses of the autocorrelation functions of alpha and beta secondary structure show significant differences.

alpha-helices; amino acids; beta-sheets; DNA; Fourier analysis; fractal dimension; long-range correlations; low dimensional chaos; nucleotides

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