One of the greatest mysteries scientists have been trying to reveal is how inanimate chemicals joined to produce life. It’s definitely one of the biggest questions scientists are trying to answer, and the challenges are numerous since it’s very difficult to appreciate what the exact conditions necessary for this to happen were billions of years ago. We might never find out what the exact molecules that sprouted life were, but by studying the biomolecules available today, valuable clues emerge. In time, it may be possible to simulate and re-create these conditions.
Pasquale Stano at the University of Roma Tre sought to investigate how biomolecules might have provided one way to trigger life trough a characteristic process known to scientists since the 1980s: self-organization. Previously, a model for the origin life was devised into a two-stage process of natural chemical evolution:
1) formation of organic molecules, which combine to make larger biomolecules;
2) self-organization of these molecules into a living organism.
The simplest “living system” we can imagine, involving hundreds of components interacting in an organized way to achieve energy production and self-replication, would be extremely difficult to assemble by undirected natural process. And all of this self-organization would have to occur before natural selection (which depends on self-replication) was available, according to Craig Rusbult. Basically, the complexity required for life (the two stage process) is a lot greater than the complexity available by natural process, considering lifeless matter is the starting point. With this in mind, scientists have been trying to devise new models with less requirements while still being viable – no such model has been found thus far, and some believe life as we know it originated as a fluke of nature.
We’re missing something
Stano’s research suggests that we simply don’t know all the variables yet and our model assumptions might be wrong from the get-go. University of Roma scientists chose an assembly comprised of 83 different molecules including DNA, which was programmed to produce a special green fluorescent protein (GFP) that could be observed under a confocal microscope. This assembly can produce proteins, necessary for the formation of life.
To produce proteins, all of these molecules need to be really close together for chemical reactions to occur, which is why cell components are so densely packed together. The researchers diluted the assembly with water, spacing the molecules apart and making protein generation impossible. However, they then added a chemical called POPC; a fatty molecule which isn’t soluble in water and when in contact with water forms liposomes. These have a very similar structure to the membranes of living cells and are widely used to study the evolution of cell. This was made in hope that some of these liposomes would trap the myrriad of molecules required for assembly. Here’s where it gets interesting.
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A computer simulation showed that the chance of even one liposome producing the green fluorescent protein the assembly was programmed for is zero. In their experiment, however, the scientists found that five in every 1,000 such liposomes had all 83 of the molecules needed to produce the protein and glowed in the dark. Stano and colleagues do not yet understand why this happened, but what’s certain is that their model assumptions were wrong and that something unique may be at play.
It may be that these particular molecules are suited to this kind of self-organisation because they are already highly evolved, which is why research into origin of life is so difficult. Research which less complex molecules will follow next to see if the results can be replicated. Nevertheless, their findings described in the journal Angewandte Chemie provide one more clue and a solid stepping stone for researchers to follow in their quest to answer how life on Earth came to be.