Biological complexity: magical photosynthesis (Introduction)

by David Turell , Wednesday, November 07, 2018, 19:03 (1997 days ago) @ David Turell

The appearance of the photosynthesis mechanism transformed the Earth by adding oxygen to the atmosphere so life could evolve to the complex forms of today:

https://phys.org/news/2018-11-high-resolution-atomic-movie-photosynthesis-date.html

"When Earth formed about 4.5 billion years ago, the planet's landscape was almost nothing like what it is today. ....But it wasn't until one of those specks of life mutated and developed the ability to harness light from the sun and turn it into energy, releasing oxygen molecules from water in the process, that Earth started to evolve into the planet it is today. This process, oxygenic photosynthesis, is considered one of nature's crown jewels and has remained relatively unchanged in the more than 2 billion years since it emerged.

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"Photosystem II is the workhorse responsible for using sunlight to break water down into its atomic components, unlocking hydrogen and oxygen.

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"Previously, the researchers were able to determine the room temperature structure of two of the states at a resolution of 2.25 angstroms; one angstrom is about the diameter of a hydrogen atom. This allowed them to see the position of the heavy metal atoms, but left some questions about the exact positions of the lighter atoms, like oxygen. In this paper, they were able to improve the resolution even further, to 2 angstroms, which enabled them to start seeing the position of lighter atoms more clearly, as well as draw a more detailed map of the chemical structure of the metal catalytic center in the complex where water is split.
This center, called the oxygen-evolving complex, is a cluster of four manganese atoms and one calcium atom bridged with oxygen atoms. It cycles through the four stable oxidation states, S0-S3, when exposed to sunlight.

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"One of the most significant aspects of this paper, Yano said, is that they were able to image two moments in between S2 and S3. In upcoming experiments, the researchers hope to use the same technique to image more of these in-between states, including the mad dash for home—the transient state, or S4, where two atoms of oxygen bond together—providing information about the chemistry of the reaction that is vital to mimicking this process in artificial systems.

"'The entire cycle takes nearly two milliseconds to complete," Kern said. "Our dream is to capture 50 microsecond steps throughout the full cycle, each of them with the highest resolution possible, to create this atomic movie of the entire process."

"Although they still have a way to go, the researchers said that these results provide a path forward, both in unveiling the mysteries of how photosynthesis works, and in offering a blueprint for artificial sources of renewable energy."

Comment: this is a biological system so complex we still don't fully know how it works, and it requires the invention of very advanced study tools that still do not exist to complete the job. We might ask the obvious question. How dos life invent a process like this by chance? Not likely, is it? The picket fence should be shaking.