Chemical modification has become an important way to improve the performance of oligonucleotides, which have high sensitivity and specificity, enhanced affinity to complementary nucleic acids sequences, and the capacity to recognize and permeate target cell membranes. One form of chemical modification is the attachment of ligands that can be covalently attached to oligonucleotide chains through the 5′ or 3′ end, the nucleobases, the sugars, or the internucleotide bridges.
Phosphotriester and phosphite methods are the two main techniques used for the synthesis of oligonucleotides. Both involve very active intermediates that require appropriate protection for the functional groups not engaged in the coupling reactions, and deprotection conditions that do not affect the integrity of the oligonucleotide chain. Because of these constraints, these two methods are essentially used to introduce simple and chemically stable functional groups or ligands to the 5′ end of oligonucleotides. In the case of ligands with poor chemical stability or complex structures, the best conjugation method involves coupling to unblocked oligomers. The preparation of oligonucleotide ligands from unblocked oligomers requires a reactive electrophilic or nucleophilic group at its 5 'end, which reacts specifically with ligands bearing appropriate functional groups either directly or after activation. Functional groups that meet these requirements include phosphorous, thiophosphate, thiol, amino, carboxyl, and cis-dihydroxyl groups.
Amerigo Scientific offers a variety of chromophores and ligands for the development of modified synthetic oligonucleotides conjugated with reporter molecules that can be used in hybridization-based assays. These oligonucleotides have high specificity to the target nucleic acid sequence and are widely used in basic molecular biology research and clinical diagnosis.