Living Spaceships From Synthetic Chemical Signals?

By Eric Bland for Discovery News

A rush of adrenaline or the pain of a burn seem simple enough, but both are the result of complex chemical interactions known as signaling cascades, vital to all life on Earth.

European scientists are taking the first steps toward creating synthetic signaling cascades. The research has powerful implications for how life on Earth could have developed and what life on other planets could look like.

It could also lead to stronger materials that can respond to their environment intelligently.

"The machines that we use to travel in space and go to the bottom of the ocean -- to go places where biological organisms can't go -- are complex but also rather simple in that they are dumb pieces of metal stuck together with rivets and glue," said Jonathan Nitschke, a scientist at the University of Cambridge and the co-author of a recent paper in the journal Nature Chemistry.

"If we had materials that stuck together like biological organisms, that grew and responded to stimuli, that healed themselves after being punctured, (then) that could allow you to make a living spaceship that could safely travel through space," he added. "This research allows us to start dreaming in that direction -- at least a little bit."

The first step to realizing these science fiction fantasies is to create materials that can react to changes in their environment. Biological organisms do this through signaling cascades.

Signaling cascades are everywhere in nature. The rush of adrenaline spurring humans to fight or flee, the release of ions that allows your fingers to move and the conversion of light from the sun into energy by plants are only a few examples of signaling cascades.

Without these complex chemical chains, life on Earth -- or anywhere else, for that matter -- likely wouldn't be possible.

The scientists wanted to go back to the very beginnings of life, using signaling cascades to learn how it might have begun or evolved. So they created a simple mimic of these complex systems, but using materials that could build a spaceship, like metals.

They created molecules with ladder shapes, like DNA, shapes that could reveal more about how that particular form of molecule might have interacted with its environment before life began.

At the core was copper, instead of the four nucleotides that real DNA contains. The rest of the molecule surrounding the copper was made from normal organic materials such as carbon, resulting in a signaling cascade that wasn't biological, because of the metal, but was still carbon-based, like all life as we know it.

The new molecules were suspended in a solution. When zinc was added to the mixture, it chased away copper ions from the core and took their places, forming a new molecule. The ejected copper didn't just sit there, though, the metal scavenged materials from the surrounding solution and created another shell around itself: another new molecule.

Another chemical was added to the mixture. But now there was a problem: there were no more free-floating materials to scavenge. To build itself, the third molecule had to destroy the first two molecules and use their broken bodies.

Understanding how these new molecules form themselves could lead to the creation of new, intelligent materials, which could become stronger or weaker depending on their surroundings, with no input from a human controller.

If the material detects even subtle changes in, for example, the surrounding pressure or chemistry, it could trigger a signaling cascade that could automatically strengthen a material, make it more flexible, or repair damage.

Living spaceships are one possible outcome of this, said Nitschke, but that's far off.

Other signaling cascades have been created before, noted Nitschke and Darren Johnson, a scientist at the University of Oregon. However, this new signaling cascade is more versatile.

"I think this is a real breakthrough in self-assembling systems," said Johnson. "It mimics the very complex signaling system in biology, and could open the door for a number of interesting applications."

Living spaceships and artificial life are certainly possible eventually, said Johnson. But before those science fiction dreams become reality, more mundane applications, like drug delivery or drug release and quicker, cheaper assembly of molecular machines, will likely happen.