Bio-Synthesis offers several types of azide, alkyne, or copper free dibenzo-cycloocytne (DBCO) modifiers to be introduced at the 5’, 3’, or internal positions during chemical synthesis. The reaction between an azide and an alkyne has been referred to as the Huisgen cycloaddition reaction since 1964. More recently the Sharpless group invented the term “click chemistry” to describe the reactions because of the nature of the electrophiles that participate in it.
Azides are useful electrophilic contributors in click chemistry reactions due to their ease of formation and stability. For this reason, alkyl azides undergo nearly no side reactions and are extremely stable in aqueous solution regardless of the presence of biological material. In addition, alkyne groups are also remarkably stable in biological mixtures, as long as they don’t have an activating group nearby, such as a carbonyl, which would make them susceptible to Michael-type addition reactions, especially with thiols.
Azides are useful electrophilic contributors in click chemistry reactions due to their ease of formation and stability. For this reason, alkyl azides undergo nearly no side reactions and are extremely stable in aqueous solution regardless of the presence of biological material. In addition, alkyne groups are also remarkably stable in biological mixtures, as long as they don’t have an activating group nearby, such as a carbonyl, which would make them susceptible to Michael-type addition reactions, especially with thiols.
Both functional groups used in click chemistry conjugations are completely unreactive towards biological molecules and free from side reactions which would cause instability in aqueous environments. As a result, oligonucleotides modified to contain an azide or alkyne group would react specifically to one another even in the presence of other molecules. In addition, without the presence of Cu(I), the azido-molecule and the alkyne-molecule would not by catalyzed to react to an considerable extent.
There is one drawback to the classic click chemistry approach. The copper ions used in the reaction can harm cells, reduce fluorescence of fluorophores and even impair protein functions. An alternative for preventing these harmful reactions is to modify an oligo with DCBO alkyne reagents. DCBO modified oligonucleotides are compatible with copper free click chemistry reactions.