Interaction of DNA and deoxyribonucleoprotein with methylene blue. Influence of acid fixation and pretreatment used in chromosome G-banding techniques.

Influence of fixation and so-called pretreatment procedures used in visualization of chromosome G-bands on staining capacity of isolated biopolymers in solution and on chromatin of cell nuclei was investigated. Whereas acid fixation as well as pretreatment procedures generally decreased the maximum binding capacity of isolated DNA and DNP for methylene blue, the dye content in acid-fixed nuclei was increased as compared with chromatin of neutral-fixed and non-fixed nuclei. The role of dehistonization and aggregation in an acid medium on the dye-binding properties of these two types of DNP was examined and the relation of higher-order structure of chromatin to its staining properties as reflected in G-banding pattern was discussed.