NUCLEIC-ACID DENDRIMERS - NOVEL BIOPOLYMER STRUCTURES

A general convergent-growth procedure for the synthesis of nucleic acid dendrimers has been developed. The synthetic strategy involves (i) the synthesis of oligonucleotides on the surface of controlled-pore glass with an automated DNA synthesizer, (ii) the introduction of the branch-point nucleoside by the coupling of two adjacent polymer-bound nucleotide chains with a tetrazole-activated adenosine 2',3'-bis(phosphoramidite) derivative, and (iii) repetitive chain elongation and branching steps to form successive generations (G = 1-3), each with twice as many chain ends as the previous generation. Various dendrimers were constructed based on thymidine and adenosine building blocks, including an 87-unit-long dendrimer having a molecular weight of ca. 25 000 with six branch points and twelve terminal ends at the periphery of the macromolecule. Full enzymatic characterization of the dendrimers is also described.