For centuries, the best chemists in the world struggled every day to create the molecules that your own cells manufacture every second. Then they discovered how one group of atoms let them make stuff that only living cells could make, until then. Here’s why we no longer need life to create the products of life.
The Transition Metals
On the main periodic table, the transition metals form the slender bridge between the two chunks on the left and the right. They’re metals. You can beat any one of them into a thin wire, and then use that wire to conduct heat and electricity. But the transition metals also have other qualities. Most of these qualities are linked to the placement of the metals’ electrons: We know that atoms link up by sharing electrons, and these tend to be the electrons on the atoms’ outer “shells.”
Transition metals have electrons that link up on both their outer, and one of their inner, shells. This quality gives transition metals a more complex and varied life than other metals.
Mix sodium chloride (sodium being a non-transition metal) with water, and you get salty water. Evaporate the water again and you get sodium chloride again. Such a thing is not guaranteed with transition metals, which, when put in a solution, can drop one element and pick up a better one. More importantly, they can pick up an element, then drop it, then pick up another.
As we’ve seen, when platinum is exposed to nitrogen-oxide, it grabs the nitrogen away from the oxygen, releases the nitrogen, then grabs the nitrogen off of the next nitrogen-oxide pair. Simply by being there, this transition metal instigates a process that would otherwise take time, extreme conditions, or intention to happen.
How Palladium Can Imitate Life
Ripping apart nitrogen and oxygen is a relatively simple process. There are much more difficult atoms to work with. One of the most notoriously difficult atoms is carbon. How can this be? Carbon is both stable and common. It is the basis for all known life, is famous for existing in a wide variety of forms, and is often manipulated into different structures. It seems like it should be easy to work with.
Carbon’s stability has actually proved to be a curse. Carbon atoms need to be very close to each other, to react with each other. Biological systems had very complicated ways of making that happen, but clumsy humans with their clumsy instruments couldn’t get the same results. The only way to get carbon to team up with more carbon was to render both carbon atoms more reactive, and once they were more reactive, they reacted with too many things.
Chemists were stymied, until they looked at an unassuming little transition metal called palladium. Remember the odd placement of the transition metals’ electron orbitals? There were three transition metals that had electron placement that would basically “dock” two carbon atoms within easy reach of each other. Platinum and nickel proved too slow. An atom of palladium however, picked up two carbon atoms, brought them in close, let them react, and then dropped them again to pick up the next set of carbon atoms. This remarkable property was discovered, independently by three different scientists. Richard Heck used palladium to make durable and strong synthetic fibers. Ei-ichi Negishi described how to make seemingly impossible connections using many different metals, palladium being one of them. Akira Suzuki found a method of linking compounds with palladium which is now used to make antiviral drugs. These three scientists shared the Nobel Prize for Chemistry in 2010.
These discoveries — however interesting to chemists and useful to the world — don’t at first seem like the stuff to fill one’s mind with inspiration. But these processes, and these elements, are more intimately connected with life than they appear to be. Every day, your cells build elaborate proteins which facilitate reactions . . . which build the cells. This stumped scientists for a good long while. How could cells exist, if only the cells themselves could make the structures which could build cells? The answer came when it was discovered that transition metals that could act at catalysts. Iron and copper inadvertently built the stuff that built the cells that resulted in life on Earth.
And now, life on Earth is repeating the process deliberately. Palladium allows chemists to build molecules that, up until now, could only be created by living cells.
If you want a concrete example, take a look at photosynthesis. Plants turn energy from the sun into chemical energy, and they do it by building a complex molecule with lots of carbon atoms bonded together. Once upon a time, that was impossible to make without another complicated molecule, an enzyme called rubisco which was also built by the plants. Now scientists can make the same energy-storing molecule without the enzyme, and they can do it using palladium to hook up the carbon. And they can do it with fewer steps than the plant takes to make the same molecule. Suddenly, and because of these discoveries, we can create the energy of the plant, without the plant. Amazing.