From Purple Membranes to Pigmented Proteins: How Rhodopsins Sense and Harvest Light.

From Purple Membranes to Pigmented Proteins: How Rhodopsins Sense and Harvest Light.

An estimated 13% of bacteria in the nutrient poor, high radiation sunlit surface of oceans were found to contain variants of the protein proteorhodopsin, which could allow them to harvest electromagnetic energy from light.

The most intensely studied light harvesting protein is bacteriorhodopsin. It uses light energy to pump protons out of the bacterial cell. Just as a waterfall can drive a turbine to generate electricity, the protons can run back into the cell and turn the rotary motor of the ATP-synthase, to make the main currency of energy used by the cell (ATP).

How do rhodopsin-like proteins sense light and extract energy from it? Can we use them to fire action potentials in neurons by the flick of a light switch, or to restore vision to the blind? A recent paper reported using a rhodopsin variant as a voltage sensor, to detect action potentials in neurons…how does that work? What do carrots have to do with all this?

Answers are in the images..if you have questions, ask. I teach this stuff and love it!

For all serious science geeks, including Koen De Paus , and Rich Pollett , who rashly agreed to read this.

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25 Responses to From Purple Membranes to Pigmented Proteins: How Rhodopsins Sense and Harvest Light.


  1. Very exciting methinks!

  2. Rich Pollett says:


    Thanks Rajini Rao, fascinating and much appreciated – rash or not. Yep I love all this too. 🙂


  3. Could one use a mechanism like this to sense a specific action potential in specific neuron and cause a specific response on a chip, like say record/amplify/modulate/resist/etc the action potential? If so do you know anyone who is working on those kinds of electronic interfaces? Rajini Rao

  4. Rajini Rao says:


    My cool choice was the very recent discovery that skin cells have rhodopsin which is what signals our skins to tan..makes perfect sense, wonder why it was not discovered before. It didn’t get as much press either. The voltage sensor (#6) is cool too, but needs much genetic tweaking to become cooler!


  5. This is a discussion I will surely follow, although it’s really hard for me to understand all the image’s content…


    I think that it is quite inspiring to find such “hard” science posts in Google+, and if you add to it the chance to ask questions to an expert, it is surely a winning combination!


    Too bad I’m so far afield from this area to start asking questions myself…

  6. Rajini Rao says:


    William Tatum , I know of one method that uses lipid membranes adsorbed to thin gold solid supports, it could be modified for neurons or there may be better ways. The lipids have ion channels or proteins that move charges across the membrane. The charge is detected by the gold layer as “coupled capacitance” changes and shows up as a spike of current. Klaus Fendler in Germany has perfected this, and there was a spin off company for this technology.


    http://www.ncbi.nlm.nih.gov/pubmed/19580777


    Neurons can be grown on a chip, specific neurons can be activated if they have been engineered to make these channel rhodopsins. I’ll look around to see if anyone has done something along the lines you mention.


  7. Rajini Rao Thank you so very much. I had not heard about that company or what they were doing. Will be looking into them.


    So i was reading about how a mouse had cells that were “trained” with human stem cells and then then implanted into the mouse and it conferred the “training” to neurons in the rats brain.(http://io9.com/5862310/breakthrough-human-stem-cells-successfully-transplanted-into-mouse-brains) Could one grow neurons on a chip engineered to do “something”(doesn’t really matter what just something to prove the concept), “train” other neurons, in culture, to interact with said neurons on a chip and then implant the whole thing with a bunch of cell growth “fertilizers” into a brain?


    I am a total layman but very interested in the topic.

  8. DaFreak says:


    I am going to put this link here because this “COLBERT” project made use of channel rhodopsins to activate neurons as well… not on a chip though… :p


    http://colbert.physics.harvard.edu/

  9. Rajini Rao says:


    I downloaded the original article, William Tatum , let me read through and get back to you. It is impressive, they grow the mouse neurons together with human stem cells and the latter are trained to fire action potentials that look like the adult mouse neurons 🙂

  10. Rajini Rao says:


    Thanks for the link, Koen De Paus ..very apropos, and I love it when scientists show their funny, mischievous side!

  11. DaFreak says:


    Same here, if you name your project X3Lv7ab#119, it’s very hard to get the public to read further than that while project Colbert is much more inviting. ^^

  12. Rajini Rao says:


    Haha, yes..my lame joke to my class (repeated every year, of course) is that I get my exercise from “pumping ion”..get it? 😉

  13. DaFreak says:


    sooo… have you ever scored a laugh with that one yet? 😉


    I actually dig “nerd” humor quite a bit. :p


    If you are looking for more inspiration; just search for science cats ^^


    http://images.icanhascheezburger.com/completestore/2008/12/23/128745494486077048.jpg


    http://i2.photobucket.com/albums/y45/Christopher4myspace/Science%20Cat/Inertia.jpg


    http://icanhascheezburger.com/2011/07/26/funny-pictures-chemistry-cat-science-puns/


    Sorry, couldn’t stop myself, this one goes below the belt ^^ (not that it applies to biochemistry but w/e)


    http://particlezoo.net/physicsLOLcats/physics_cat.jpg


  14. Brought back some nice memories since bR was the first protein I ever worked with for a research project (Master’s thesis). That was around when Landau’s group came out with the crystal structure of the protein (one of the earliest membrane proteins to have such a high-resolution structure!).


    Back in the 90s, I believe a group was also trying to use oriented purple membranes for designing hybrid electronic circuits with the aim of building biological computers. Was a neat idea, but not sure how it has turned out.


    Optogenetics (Nature Method’s Method of the Year for 2010) – like the CoLBeRT project – is a really cool application of the rhodopsin family.

  15. Rajini Rao says:


    Ahh, Prithwish Pal , so you are the real expert on this forum! As you know, I’m more of an ATPase person..my first love was the ATP synthase from my Rochester days with Alan Senior. bR is the best studied ion pump, and so elegant too..it actually changes to a rainbow of colors with each spectrometric intermediate. And our fellow countryman and Noble Laureate, Har Gobind Khorana, synthesized it from scratch. A cool protein all around, cheers!

  16. Rajini Rao says:


    LOL, Koen De Paus , I chuckled at the physics cat, of course. Don’t worry, we have a pecking order in Biology too..the biophysicists claim superiority in rigor over the biochemists, who in turn scoff at the cell biologists..and so on..


    Besides the best science cat jokes comes from chemistry: e.g., what do you call a mix of iron, lithium and neon? FeLiNe! 🙂


  17. sorry about that. some drunken lout just snatched my tablet away from me. Excuse me while I give him a thrashing

  18. Rajini Rao says:


    Marc Ponomareff , this IS WIN Central, stick around 😉

  19. Rajini Rao says:


    Marc Ponomareff , LOL, bring back that drunken lout, I quite like him 🙂


  20. OK. So, let’s have some WINS then!! blerg


  21. Wondering if it would be possible to use it to activate all parts of the brains – maybe not all, but at least increase neural activity. Comma patients should make perfect test candidates. I’ll definitely read more on this. It’s fascinating.

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