ABSTRACT
Nucleic acid hybridization describes a range of techniques in which single-stranded nucleic acids are incubated under conditions of temperature and ionic strength that favor pairing of complementary bases and duplex formation. This chapter considers the structure and properties of nucleic acids with special emphasis on properties that affect hybridization. All nucleic acids are composed of nitrogenous bases, pentose sugars and phosphate. In DNA, the bases are the purines adenine and guanine and the pyrimidines cytosine and thymine. Covalent bonds between adjacent nucleotides determine the primary structure of DNA and weak forces determine the three-dimensional shape. These forces are individually weak, but they act co-operatively and are collectively strong enough to maintain a stable structure while being weak enough to allow conformational flexibility. The strictness of base-pairing rules produces a regular helix because each base pair is about the same size. Certain mismatches can be tolerated within a double-stranded structure, causing minimal local structural perturbations.
