  We have found that the effective survival time of amino acids in organisms
follows a power law with respect to frequency of their occurrence in genes. We
have used mutation data matrix PAM1 PET91 to calculate selection pressure on
each kind of amino acid. The results have been compared to MPM1 matrix
(Mutation Probability Matrix) representing the pure mutational pressure in the
Borrelia burgdorferi genome.The results are universal in the sense that the
survival time of amino acids calculated from the higher order PAMk matrices
(k>1) follows the same power law as in the case of PAM1 matrices.
