HPLC traces for the separation of nucleoside mixtures arising from the enzymatic digestion of nucleic acids that were isolated from the in-vivo chemically cross-linked DNA-protein complexes by the standard phenol extraction method (A) and the DNAzol method (B). The identities of nucleosides were confirmed by HPLC analysis of authentic compounds. “A”, “C”, “G”, “U” designate the four natural ribonucleosides, and “dA”, “dC”, “dG”, and “dT” represent the four natural 2′-deoxyribonucleosides.