Polynucleotide-chitosan complex, an insoluble but reactive form of polynucleotide

DNA formed an insoluble complex on mixing with chitosan (poly-D-glucosamine) in solution. The DNA content of the complex was about 50% and the DNA remained insoluble in aqueous media of pH 2-7%; e.g., on treatment of the DNA-chitosan complex with phosphate-buffered saline at pH 7 and 37 degrees C for 26 h, the DNA released into the aqueous phase was less than 0.05%. Obviously, DNA and chitosan formed a tight complex due to ionic interactions. The DNA can be solubilized by treatment with 0.1 N NaOH. RNA and other polynucleotides formed similar insoluble complexes with chitosan. The DNA attached to chitosan can be digested with a mixture of DNase I and phosphodiesterase. Cytosine residues in the DNA (denatured DNA) can be deaminated by treatment with sodium bisulfite, forming uracil DNA-chitosan. The uracil DNA-chitosan served as a substrate for uracil DNA glycosylase. Using polynucleotide-chitosan as an adsorbent, the affinities of reagents for polynucleotides can be determined directly. With this technique it was found that carcinogenic heterocyclic amines have an affinity for RNA as well as DNA. The results with homopolyribonucleotide-chitosans as adsorbents for 4 heterocyclic amines indicated that the binding occurs in a purine nucleotide-specific manner. These results suggest that the polynucleotides in the chitosan complex are accessible to enzymes and reagents. This new derivative may be useful in chemical and biological studies of polynucleotides and substances interacting with polynucleotides.