The attachment of reporter groups, drug derivatives, or chemically reactive species to DNA in a sequence-specific manner has the potential to provide new materials for detailed spectroscopic and structural analyses as well as new classes of DNA therapeutics and diagnostics. Sequence specific labeling of a nucleic acid sequence can be achieved by a number of procedures that employ either the nucleobase, the carbohydrate or the phosphate residue as a site for attachment (for a recent reviewseeref. 1 ). Specific functional groups (such as terminal phosphomonoesters,seeChapter 3 ) or the enhanced reactivity of selected sites on the purine or pyrimidine building blocks (such as the C5-position of pyrimidines,seeChapter 2 ) are often used in order to covalently attach an appropriate linker or the desired reporter group. The manner in which the nucleic acid is labeled may be dictated by the specific study involved, but in general the principles of simplicity and versatility are best employed to guide the choice of labeling procedure.
