Analysis of the frequencies of occurrence of mono- and dinucleotides in sequenced E. coli DNA fragments was performed. The DNA sequences of total length 135 000 nucleotides were considered. It was demonstrated that the fragments of DNA which have different functional properties also have different parameters of neighbour nucleotides correlation. Moreover, periodical positional dependence of correlation parameters in coding regions was found. The evolution significance of stated observation is discussed, so as the opportunity of using them in the special model of nucleotide's sequences, which is needed for development of the computer recognition algorithms for genomic functional units.