Scientists create "living" crystals

Discussion in 'Chemistry' started by Magical Realist, Jun 30, 2014.

  1. Magical Realist Valued Senior Member

    "Three billion years after inanimate chemistry first became animate life, a newly synthesized laboratory compound is behaving in uncannily lifelike ways.

    The particles aren’t truly alive — but they’re not far off, either. Exposed to light and fed by chemicals, they form crystals that move, break apart and form again.

    “There is a blurry frontier between active and alive,” said biophysicist Jérémie Palacci of New York University. “That is exactly the kind of question that such works raise.”

    Palacci and fellow NYU physicist Paul Chaikin led a group of researchers in developing the particles, which are described Jan. 31 in Science as forming “living crystals” in the right chemical conditions.

    Their experiments are rooted in the researchers’ interest in self-organizing collective behaviors, which are easier to study in controlled particle form than in schooling fish or flocking birds.

    Each particle is made from a microscopic cube of hematite, a compound consisting of iron and oxygen, sheathed in a spherical polymer coat. One corner is left exposed.

    Under certain wavelengths of blue light, hematite conducts electricity. When the particles are placed in a hydrogen peroxide bath under blue light, chemical reactions catalyze around the exposed tips.

    'There is a blurry frontier between active and alive.'

    As the hydrogen peroxide breaks down, concentration gradients form. The particles travel down these, aggregating into crystals that also follow the gradients.

    Random forces pull the crystals apart, but eventually they merge again. The process repeats again and again, stopping only when the lights go out.

    The ultimate goal of the work is to study how complicated collective behaviors arise from simple individual properties, perhaps informing molecular self-assembly projects, but it’s hard not to think about the origin-of-life implications.

    “Here we show that with a simple, synthetic active system, we can reproduce some features of living systems,” Palacci said. “I do not think this makes our systems alive, but it stresses the fact that the limit between the two is somewhat arbitrary.”

    Chaikin notes that life is difficult to define, but can be said to possess metabolism, mobility, and the ability to self-replicate. His crystals have the first two, but not the last.

    Some scientists think that life’s building blocks once existed in such a form, bouncing back and forth for millions of years until coalescing in configurations that possessed the ability to copy themselves.

    Add slight imperfections in the copies — mutations, in other words — and the necessary conditions for natural selection and evolution would be fulfilled.

    Inasmuch as it’s possible to say what might have happened billions of years ago, the rest was evolutionary history.

    As for what’s happening now in Palacci and Chaikin’s lab, a particle currently under development isn’t mobile, but it has a metabolism and is self-replicating.

    “We’re working on it,” Chaikin said.

    Citation: “Living Crystals of Light-Activated Colloidal Surfers.” By Jeremie Palacci, Stefano Sacanna, Asher Preska Steinberg, David J. Pine, Paul M. Chaikin. Science, Vol. 339 No. 6119, 1 February 2013.
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  3. exchemist Valued Senior Member

    Nice! Thanks for drawing to my attention.
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  5. humbleteleskop Banned Banned

    Transformium. It's the stuff Transformers are made of. Movies are like science, only faster.
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  7. wellwisher Banned Banned

    One could do the same thing in another way. If we mix oil and water and agitate, an emulsion will form, as the two phases break down into smaller and small bubbles of water and oil. If we stop the agitation, the water and oil bubble will each self assemble trying to form only two layers. This is all based on free energy; entropy and enthalpy. Using the criteria of life being connected to self assembly, water and oil (reduced organics) provide the simplest and most abundant natural systems of self assembly.

    Water and lipids self-assemble into a bilayer of lipids surrounded by water inside and out. If we agitate this, we can break it down by adding energy. Once the energy is released the entropy lowers and new lipid bilayers appear due to self assembly directed by the water.

    For the next experiment, we will add a third component like an alcohol to oil and water. With the same agitation, the bubble can get even smaller due to the solvent action of the alcohol. If we turn off the agitation the systems will also self assemble but now the result is somewhat different with more than two phases. As the alcohol evaporates the experiments also changes by lowering the solvent power of the alcohol.

    If we start with oil and water and agitate we again get an emulsion. Next, we will add random protein, with both organic and polar surfaces. As the water and oil separate or self assemble, the protein will also self assemble, some assembling into the oil and some into the water phase; extraction. The protein know where to go via this complex self assembly. Membrane proteins find the membrane, while water based protein find the water where they self assemble with the water and oil molecules and often with each other in pairings.

    The water-oil system could be called living by the new looser definition, with its basic self assembly considerations being modified and modifying others materials, into the self assembly of life.

    Once we get to a cell, the same principles of oil and water apply. You need an energy source to increase the entropy for division. Once this energy source stops, there is a push toward natural self assembly using the fundamental self assembly of water-oil. Aspects like the nuclear membrane which were dispersed via entropy and energy, once again self assemble allowing specific self assembly within a larger self assembly, with oil and water the foundation for self assembly that was/is always there.
  8. humbleteleskop Banned Banned

    Indeed. Still pretty weird it would tend to shape into such extreme complexity. Perhaps contrary to intuition, it turns out more complex is more robust than less complex.
  9. Write4U Valued Senior Member

    Perhaps it turns out that nature reaches "optimum" complexity, or even sheds complexity which is no longer needed.

    Even in mundane terms most living organisms seems to have "defunct" genes, leftovers from prior configurations, but no longer needed or used..
  10. humbleteleskop Banned Banned

    There surely must be optimal points, possibly more than one per any particular ratio between size and mass. I'm not sure about shedding complexity, like blind cave-fish lost their eyes. Perhaps they gained complexity somewhere else in the same time. But really, if shedding complexity is for the best, then that should be the way to go, which means adaptivity has higher priority than evolution.

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