Oligo- and Polynucleotides

The predominant feature of nucleic acids in aqueous solution is the ionic nature of their phosphate groups which makes these molecules ideal candidates for separation by ion-exchange chromatography. Reversed phase separations may also be carried out by utilising the weak hydrophobic nature of the nucleic acid bases. Natural nucleic acids occur in many different size classes and group separations (e.g. between ribosomal RNA and transfer RNA) by size exclusion can also be effective. The relative merits of these methods are described in the following sections. 

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Size discriminating CE (Capillary gel Oligo- and polynucleotides, oligo- and Slab-gel... 

Because of the complex behaviour to be expected for natural nucleic acids, it is only natural that considerable effort has been devoted to studies of the electrochemical properties of their monomeric units, and defined analogues of these, as well as of synthetic oligo- and polynucleotides. A variety of techniques has been applied for this purpose, and some of the details and findings are covered in several reviews 19 24). Most investigations have dealt with electroreduction processes 15 20,24,25). Only relatively recently has attention been directed to possible electrooxidation of nucleic acids and their constituents with the aid of the graphite electrode which, in comparison with the mercury electrode, possesses a much greater accessible range of positive potentials 26 29). 

The ability of adenine and cytosine to undergo reduction in aqueous medium is at least partially retained at the level of oligo- and polynucleotides. In both acid and neutral media, such residues in single-stranded RNA, DNA and synthetic polynucleotides, when subjected to d.c. polarography, undergo irreversible reduction in a protonated, adsorbed, state with the transfer of four electrons to adenine... 

While the importance of IR and Raman spectroscopy for the structural elucidation of purine bases has diminished over the last few decades, its advantages for the study of oligo- and polynucleotides in particular with respect to base pairing is apparent. The IR absorption spectrum of a single-stranded polynucleotide is very similar to that of its component nucleotides, but drastic changes occur on formation of hydrogen-bonded helical structures. 

The distinguishing feature of the photochemistry of purines and their derivatives is their relatively higher resistance to UV irradiation compared with pyrimidine derivatives. With an increase of the dose of UV irradiation, a decrease of absorption of the purines at or ven its complete disappearance, is observed. Purine oligo- and polynucleotides exhibit greater photochemical stability than mononucleotides. 

Nucleotides and Nucleic Acids Oligo- and Polynucleotides 4 Nucleic Acid Structures... 

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