Testing life’s metal

I’ve always been a huge fan of alternative biochemistries. Because as marvellous as we terrestrial lifeforms are with our amino acids and our sugar phosphate self-replicating polymers, there’s got to be more than one way to skin this particular catfish. Enter Lee Cronin, a scientist based at the University of Glasgow who’s attempting to create just such a thing.

It’s a curious idea really. Almost frankensteinian, in a sense. Cronin’s aim is to create cell-like bubbles made from polyoxometalates, which he hopes will one day be able to reproduce and even evolve. Synthetic, inorganic life forms. Cronin is even quoted as saying, “I am 100 per cent positive that we can get evolution to work outside organic biology.” I share his enthusiasm on the fact that it can work, but the fact that he’s actually attempting to make it work is really quite staggering!

The polyoxometallates he’s using are based on oxygen and phosphorus, with various different types of metal (Tungsten being amongst them, apparently) being used to combine with them. The molecules themselves then self-assemble into cell-like structures in solution. He accomplishes this by creating salt solutions, once containing large metal oxide anions, and the other containing large organic cations. When mixed together the large ions, metal oxide and organic, combine together and precipitate out of solution, forming shell-like structures. The image above is a microscope image of one of these cell-like bubbles, this one containing a smaller bubble within it, mimicking the internal compartments of living cells. Artificial organelles, if you will.

The interesting thing here is that if these things really do self assemble this way, then that bolsters the idea of something like this occurring naturally elsewhere. When life formed on Earth, it obviously didn’t have any scientists tinkering with it and making sure everything went according to plan. It was just a messy soup of chemicals. Anything which couldn’t form by itself would not have formed at all. Self-organisation (presumably) allowed lipids to form into bilayers and cell membranes for Earth life. Apparently self-organisation also allows polyoxometalates to do something similar in Cronin’s lab.

These metal-oxide based bubbles have been dubbed iCHELLs (short for inorganic chemical cells), and with some fine tuning of the precise chemical precursors used, they can actually be made to act like real cell membranes. It’s fairly intuitive really, seeing as whatever properties a small molecule has are passed onto any larger structure they become a part of. Use a small molecule with a hole in it, and get a porous cell wall. Further fine tuning, and you become able to carefully control how the cell behaves. Chemically speaking, that is.

The research group is even working on ways to use photosensitive dyes to split water into ions and electrons, and set up a proton gradient across one of the iCHELL membranes, to mimic photosynthesis. Could they really create an artificial cell powered by photosynthesis? Think what a leap that would be for nanotechnology!

On a final note, Cronin is attempting to introduce his iCHELLs into different chemical environments, in order to see which survive and which don’t. If an iCHELL is broken down by a different pH, it’s considered to have died, leaving behind the more adaptable and more healthy iCHELLs to continue the miniature Darwinian experiment. Apparently, though he hasn’t released any specifics, Cronin is quoted as saying that “I think we have just shown the first droplets that can evolve.” Curiouser and curiouser. I’d be interested to see what might be published from this study…

Personally, my immediate thought (aside from the general elation that someone is actually working on alternative biochemistries in the lab!) is into what the chemical composition of those iCHELL membranes actually is. And I mean in detail. I’ll admit that I haven’t read the papers yet (I don’t have access to them at home), but certain metals would be particularly favourable from an astrobiological viewpoint. For instance, ageing carbon stars tend to be rich in certain metals like Vanadium and Zirconium. Metals created in a type of stellar fusion called the s-process. Stars with spectra showing Titanium oxide are not uncommon. If any of these s-process metals prove to be particularly successful in Cronin’s iCHELLs, then I’d be very interested indeed.

Ageing bloated red giants constantly puff material off into space. Hot stardust cooling slowly in the night. Perhaps the ash from one of these elder stars may be the cause of life taking hold somewhere. What a happy thought!

Source: New Scientist
Image Credits: Microscope images – Cronin Group, Uni. Glasgow
“Mercury” – Mercury metal droplets and puddle – Cyberchemist @ Flickr
Publications: Cooper et al 2011, Miras et al 2010

I know the actual proverb is that there’s more than one way to skin a cat, but I’m rather fond of cats, so that’s an image I’d rather do without. Besides, apparently the expression was originally about catfish who, as it happens, are notoriously difficult to prepare for cooking. Ok, I should stop offending the vegetarian contingent of my readership now. Oh, and while we’re on the subject of proverbs, I hasten to add that I do know the true phrase is “testing one’s mettle”, but the pun doesn’t work with that spelling!
Which would presumably be a process of supramolecular self-assembly…?
Or perhaps it did, who am I to know? Somehow though, I have a feeling we aren’t living in a four billion year old petri dish.

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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4 Responses to Testing life’s metal

  1. Hi there are using WordPress for your site platform?
    I’m new to the blog world but I’m trying to get started and create my own.
    Do you require any html coding knowledge to make your own blog?
    Any help would be greatly appreciated!

    • invaderxan says:

      Yes, I’m hosted on wordpress.com, and I find it one of the most easy blog platforms to use! I use a couple of others which are also powered by WordPress You don’t really need any html coding knowledge, no. A little can be useful in customising your blog, and formatting your posts, but this isn’t necessary.

      Good luck with your blog!

  2. invaderxan says:

    I know what you mean. On hearing an audacious claim like that, skepticism is the only logical response. Mind you, for anything to be truly considered “alive” in our familiar biological sense, it would need some kind of genetics. Some means by which it organises itself. In other words, some polyoxometalate equivalent of DNA.
    And evolution doesn’t always happen too slowly to see, particularly in the microscopic world. Take MRSA, for instance. Essentially it evolved to survive against conventional medical antibiotics.
    Your comment was thought provoking. Thank you. And personally, I agree. Extraterrestrial life is almost certain to exist in places which we haven’t been looking. Places which our anthropocentric way of thinking has dismissed when we should have been looking closer.
    And Venus? Believe me, there’s a lot about Venus which we could know more about… :)

  3. It has been predicted that artificial cellular life could be created within ten years. I was very skeptical of that projection but the successes in this research give rise to the possibility. If iCHELLS could be made to run on artificial photosynthesis, and they could be made to self – replicate, then they would be close to alive. The final step would be to give it the ability to respond to environmental changes and self – regulate. I am curious how the different biochemistry would affect the rate of evolution. Evolution typically occurs at a rate too slow to observe. There might be a way to accelerate replication, diversification, and selection to enable observable (and “steerable”) evolution. An obvious way to artificially select the iCHELLS is stated – testing the viability of different designs under specific conditions – but I wonder if there is a way to get the cells to evolve on their own, but fast enough to observe.
    If artificial life is successful, it represents two technologies; if the cells can be controlled and specialized, they constitute nanorobots. Even if they cannot be controlled/specialized, they could still be used to grow components of nanorobots and the construction of the cells is an application of nanotech. The other technology is artificial life itself. You could call this the hybridization of nanotechnology and biotechnology, but in a way it is neither. It could be the best of both worlds. Living machines are created to “evolve” for a specific purpose. They could then increase in their efficiency and ability by evolving into their application the same way life evolves into ecological niches. This would simply require that performing their job is conducive to survival and reproduction.
    The successful creation of living iCHELLS would establish a “formula of life”, that could be used as a set of rules for creating artificial life with any biochemistry that would work in an organism. It would also offer incredible insight as to where to look for life in the universe. The worlds that produced the conditions best for the generation of life under any biochemistry would be easier to identify. I believe that the conditions of extraterrestrial worlds as related to existing life have been overemphasized. Life adapts to any conditions it exists in. What is important is whether it has the opportunity to form at all. Understanding what creates life is the part that matters. Life “takes it from there”, evolving to adapt to – and ultimately changing – the environment. Long story short, we may find out that we have been looking in the wrong places. If metal – based biochemistry proves to be successful, it opens the possibility of life on much hotter worlds than Earth. Life with silicon and metal based biochemistry could hypothetically inhabit worlds as hot as Venus.

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