A firmly hybridizable, DNA-like architecture with DAD/ADA- and ADD/DAA-type nonnatural base pairs as an extracellular genetic candidate.

We describe artificial DNA molecules exclusively consisting of four types of alkynyl C-nucleotides with nonnatural bases. The artificial DNA exhibited almost the same characteristics as natural DNA, such as in regard to the stepwise duplex and triplex formation and the right-handed higher-order structure with an antiparallel alignment fashion.