Scripps research team creates simple chemical system that mimics DNA.

A team of Scripps Research scientists has created a new analog to DNA that assembles and disassembles itself without the need for enzymes. Because the new system comprises components that might reasonably be expected in a primordial world, the new chemical system could answer questions about how life could emerge (see also Scripps Research Institute).

The work, reported in the June 11, 2009 issue of Science Express, an advance, online publication of the journal Science, might also be a starting point on the way to exotic new materials that repair themselves or transform in response to their environment.

Scientists are both bemused and fascinated by the question of how life could have arisen on Earth. One of the most prominent theories is that, before the emergence of DNA, the earliest forms of life used RNA to transmit their genetic codes. The late Leslie Orgel, a co-author of the new paper, first suggested this idea, known as the "RNA World."

One of the theory's challenges is that RNA is still so complex that many researchers believer something still simpler must have preceded it. "I have been working for years to learn what replicators and genetic systems might have come before the advent of the RNA World," says team leader of the new research Professor Reza Ghadiri, a Scripps Research chemist.

One key focus for Ghadiri's team has been amino acids' potential primordial role. In 1996, the group showed for the first time that amino acid strands, or peptides, can self-replicate under enzyme-free conditions. In the current work, the Ghadiri lab extends this focus by creating another type of information system that might be capable of something akin to Darwinian evolution. "This work is a beginning step toward that goal," says Ghadiri.

Simpler Building Blocks

While much of the past work with DNA analogs such as PNA has focused on nucleobases already anchored to their backbone units, Ghadiri had the idea of working with simpler building blocks. If these blocks had easily reversed bonds, unlike DNA and PNA, it could avoid the need for enzymes while preserving key characteristics for encoding information. Looking back on the success of the experiments that have followed, Ghardiri says, "This is one of those things where you say to yourself, 'Why didn't I think of this before?'"