The aqueous environment and ionic surrounding are the most important factors determining the conformation of DNA and its functioning in the cell. The specificity of the interaction between DNA and cations is especially pronounced with a decrease in water activity. In this work, we studied the B-A transition in high molecular weight DNA with a decrease of humidity in the film with different contents of Na+ ions using FTIR spectroscopy. The IR spectrum of DNA is not only very sensitive to the state of its secondary structure, but also allows us to estimate the amount of water bound to DNA. Upon dehydration of the DNA film, changes characteristic of the B-A transition were observed in the IR absorption spectrum. Using thermogravimetric analysis, it was shown that the degree of DNA hydration reaches the saturation level at a relative humidity of 60% and decreases slightly upon further drying. It has been established that with increasing Na+ concentration, the amount of water strongly bound to DNA decreases. Along with it, sodium ions destroy the hydration shell of DNA and are able to interact directly with phosphate groups.
The action of hypochlorite on various biological molecules in a living cell has been actively studied for years. However, the influence of the structural organization of nucleic acids on their interaction with hypochlorite remains underinvestigated. In this work, using ultraviolet and infrared spectroscopy, we analyzed the effect of the structure of nucleic acids on the reaction with hypochlorite using the example of the three most common and biologically significant types of nucleic acids (NA): double-stranded DNA in the B-form, single-stranded RNA, and nucleotide phosphates. It was found that the rate of the initial stage of the reaction of hypochlorite with endocyclic nitrogen atoms depends on the presence/absence of base pairing in the NA structure. At the same time, the polymeric structure of NC significantly accelerates and increases the efficiency of the subsequent stages of the reaction associated with the chlorination of exocyclic nitrogen atoms and the destruction of the ring structure of nitrogenous bases.
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