Quantum Phenomena of Photosynthesis

Nano-Passion

Can someone confirm this as true or as crank-science. I tried looking for any publication of this but haven't found anything.

"They were trying to establish exactly how organic photosynthesis approaches 95% efficiency, whereas the most sophisticated human solar cells operate at only half that. What they discovered is nothing short of remarkable. Using femtosecond lasers to follow the movement of light energy through a photosynthetic bacterial cell, Engel et al. observed the energy traveling along every possible direction at the same time."

Mike H

They are likely referring to work published a few years ago that was published here:

"Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems."

The issue - IMO - is not the science which is rather interesting and reasonable, but rather some people's usage of said science to support rather idiosyncratic notions (and that's being charitable).

Evo

Thank you Mike!

Nano-Passion

Yes, that is definitely the article.

Really? Can you explain? It sounds like your dismissing quantum biology as a flawed interpretation.

Mike H

I Googled a long enough fraction of that quote in your first post to sate my own curiosity out of interest. When I saw the phrase "quantum consciousness" on my screen, I immediately closed that tab in my browser. It may have been an excessive response, but I've been around the block often enough to be wary. ;)

The idea of "quantum biology" has been one that has cropped up on here before. Outside of cases like photosynthesis, certain enzymatic reactions which seem to utilize proton tunneling, and possibly a few other interesting scenarios, I don't see the urgency to directly appeal to quantum mechanics to explain things in biology - often, one can just draw upon chemistry and classical physics for answers. I suppose that one could split hairs and note that quantum chemical methods are necessary for computational studies of enzyme mechanisms, but that's the case for pure chemistry as well.

Ygggdrasil

Nature ran a recent news piece discussing a few examples of systems where quantum mechanical phenomena play important roles in biology (http://www.nature.com/news/2011/1106...l/474272a.html, subscription required). As Mike H said, these cases are limited to a few special cases of enzymes that utilize proton tunneling, Graham Flemming's work on quantum coherence in photosynthesis, and the mechanisms by which birds sense magnetic fields (see for example, http://link.aps.org/doi/10.1103/PhysRevLett.106.040503).

I also agree with Mike that attempts to invoke quantum effects to explain consciousness or other phenomena in neuroscience seem to be just a bunch of ********. Or at least no one has yet been able to show me any evidence to convince me otherwise.

Pythagorean

I've always felt like QC was an attempt to slay Laplace's demon.

It's unfortunate that it drives us to have to divide studies between classical and quantum physics. The border is a lot more fuzzy in biological systems than it is in cannonballs.

Nano-Passion

Well yeah, I was watching a documentary and his name came up so I decided to read a bit about it. I'm a skeptic myself but it might be a bit too early to completely dismiss it, until more conclusive evidence is found. As the article shared by Ygggdrasil suggested, it might be that a certain structure can enhance quantum effects under noise rather than degrade it. That much may be true for the brain, but everything else seems to have a weaker argument [for now].

Ryan_m_b

There have been some excellent responses in this thread that I entirely agree with. There is a pervasive cult of pseudo-science around quantum effects in biology. Whilst we can't totally dismiss the role of quantum effects in the brain and neither can we dismiss their role in consciousness the fact remains that there is no good evidence to accept the hypothesis and some research to show that previous claims are flawed.

Mike H

I agree that it is unfortunate, but I am rather curious about what other biological problems you have in mind that epitomize that fuzzy border. My knowledge is pretty much limited to what has been mentioned in this thread (photosynthesis/other photoactive compounds, certain enzymes, and the magnetic field sensing possibility).

Related to the paper I cited earlier - the protein they were examining (the Fenna-Matthews-Olsen protein from a green sulfur bacterium) is literally jam-packed with bacteriochlorophyll molecules (I think it's on the order of 20 such molecules per protein). It serves as a bridge for electron transfer from the light harvesting arrays to the photosynthetic reaction center. It's a very photochemically active and interesting system. If one were to find organized arrays of such molecules in other biological systems, I would imagine the argument for quantum effects in that system might be a bit easier.

Pythagorean

The chemical reactions themselves are not defined in classical mechanics. So if you want to model the system most generally, you have to mix chemistry and classical physics. I find chemistry to be too abstracted for quantitative modeling, personally. The stoichiometry and the geometry are presented as two independent concepts in a toolbag for patchwork investigation.

If you want a pure particle approach, you must define some kind of hybrid model that handle both electrodynamic particle configurations AND their reactions (meaning some allowance of QED). Not that have any idea of what that would like, but I guess I just feel there's a huge disconnect there.

I guess the overall interest is really unification of chemistry and physics, rather than patchwork modelling.

Nano-Passion

I think its unfortunate when people dismiss quantum phenomena in biology because of crack-pots when there are some people [non-crackpots] that have worked very toward understanding this phenomena, and worked faithfully. That is like the equivalent of dismissing quantum mechanics because of crackpots who attempt to extrapolate on it.

You sound like you have a very big-picture view of things; that is very important in academia. Best of luck in your endeavor!!

Ryan_m_b

Whose dismissing it only the spurious claims of quantum consciousness are dismissed.

Nano-Passion

Well.. agreed. I was just speaking in general, some do dismiss it or are reluctant to agree.

Mike H

No argument from me regarding chemical reactions not being explicable classically. Most of the computationally oriented theoretical chemists I know basically model everything either quantum mechanically or semiclassically (e.g., parametrized force fields for molecular mechanics). I suppose when I was thinking of classical physics being used to understand biological systems, I had notions along the lines of David Dusenbery's work or something along the lines of the early work in chemotaxis that Berg & Purcell did in the 1970s.

It sounds as if you want to do something like Car and Parrinello did (their merger of DFT with MD), but more general. Which would certainly be something worth doing - although I also don't have any clue how that would actually manifest itself.

Can't argue with that goal, though.

underlondon07

It doesn't seem reasonable to dismiss quantum explanations for nature's efficiency.

Drakkith

See post # 13.