[Models of chromatin fibril organization]

Idealized models of chromatin fibers are presented. They are based on the data of nucleosome structure and on the postulate about lengths congruence and rectilinearity of internucleosomal DNA fragments. It has been shown that the majority of models are in the form of spirals with the diameter 30--40 nm consisting of chains of successively located nucleosomes. With some lengths of internucleosomal stretches the spirals are transformed to linear columns with two, three of four rows of nucleosomes. The DNA packing coefficient strongly depends on the shape of the model. The structure of real chromatin fibers is believed to be close to that of compact models. Corrections of the models due to supercoiling of internucleosomal DNA stretches are considered qualitatively.