Could Quantum Biology Have Evolved Out of One Protective Mechanism?

[NinaMS]

G S Orf et al 2016 recently found evidence for a cysteine-mediated mechanism of excitation energy regulation in a photosynthetic antenna complex (of the green sulphur bacteria).

 

Further findings on the specific cysteines identified in the G S Orf study highlight a possible role for cysteine residues in the redox activity of the pigment-protein complex. R Saer 2016. By specific and reversible oxidation of redox-sensitive cysteines, many biological processes sense and respond to signals from the intracellular redox environment. M Putker 2016.

 

Other studies such as Marais 2015 have explored protective effects in other bacteria which have yet to be properly explained. These relate to a reduction in triplet product yield in reaction centres due to weak magnetic fields.

 

Such solid state photo CIDNP effects have previously been found in the green sulphur bacteria. Roy et al 2007.

 

They have also been found in Rhodobacter Sphaeroides (K Schulten 1977, K Schulten et al 2002, Daviso 2008, Prakash et al 2005, Y Liu et al 2005, Zysmilich and McDermott 1994 and 1996, Matysik et al 2000, Prakash et al 2005 and 2006, Daviso et al 2008) and Spinach (Alia et al 2004, Diller at al 2007, Matysik et al 2000, Diller et al 2005 and 2007). Full references for these studies are given by J Matysik 2009.

 

Indications of long-lived quantum coherence have been found in the green sulphur bacteria, rhodobacter sphaeroides, and spinach. And it is interesting that there has been the suggestion that there could be a link between the conditions of occurrence of photo-CIDNP in Reaction Centres and the conditions of the unsurpassed efficient light-induced electron transfer in reaction centres. This has been explored in various papers by J Matysik e.g Jeschke and Matysik 2003, J Matysik 2009), I F Cespedes-Camacho and J Matysik 2014.

 

There is evidence for the strong correlation between the degree of electronic coherence and efficient and ultrafast charge separation. E Romero 2014. And if a solid state photo CIDNP effect is a quantum mechanism supporting ultrafast charge separation in photosynthesis, there may be wider implications, as there are similar ultra-fast dynamics in bond isomerization in sensory photoreceptors and repairing DNA damage. C Tan 2015.

 

It has also been speculated that solid-state photo CIDNP effect at earth field also plays a role in the magnetoreception of biological systems....Studies have found that the 'solid-state photo-CIDNP' effect allows for signal enhancement of factors of several 10000 s. Such strong signal enhancement allows for example selectively observing photosynthetic cofactors forming radical-pairs at nanomolar concentrations in membranes, cells, and even in entire plants. W Xian Jie 2016 and G Jeskchke 2011.

Both the effect in photosynthesis and in magnetoreception may be drawing on radical pairs, and

 

- A magnetic-field effect has been demonstrated on the photochemical yield of a flavin-tryptophan radical pair in Escherichia coli photolyase. K B Henbest 2008.

 

- An effect has been observed a mutant of the bluelight photoreceptor phototropin (LOV1-C57S from Chlamydomonas reinhardtii). S S Themarath 2010.

 

It may be of interest that in flavo-proteins (mutated in order to remove a cysteine residue next to the chromophore), it is possible to form a spin-correlated radical pair. Denis V. Sosnovsky. 2016.

 

It has been thought that solid-state photo-CIDNP effect has required high magnetic fields and cyclic electron transfer, but does the paper by G S Orf offer a new perspective? Could a mechanism initially developed as a protection against damage from reactive oxygen species, become utilised (through evolution) for other purposes (e.g perhaps supporting ultra-fast electron transfer).

 

This type of approach could also be matched with the concept of environmentally assisted quantum transport - as a redox mediated system (using flavoproteins, etc) could potentially be coupled to a circadian system. Redox-circadian coupling is being found throughout biology e.g M Putker 2016, K Nishio 2015, N B Milev 2015, A Stangherlin 2013. N P Hoyle 2015. Circadian rhythms feature in almost every aspect of photosynthesis, and cryptochrome (in Arabidopsis, Drosophila, and mouse) provide the most direct path by which redox status can interact with the core components of the transcription–translation feedback loop (TTFL). Lisa Wulund 2015.

Sorry I should have also included the following in the above post.

 

The observation of the solid-state photo-CIDNP effect in phototropin has been shown that this effect is not limited to natural photosynthetic systems. In the same way that photo-CIDNP MAS NMR has provided detailed insights into photosynthetic electron transport in RCs, it is anticipated in a variety of applications in mechanistic studies of other photoactive proteins. It may be possible to characterize the photoinduced electron transfer process in cryptochrome in detail. W Xiao-Jie12016.

[Ophiolite]

You have provided a considerable amount of detail. Unfortunately, the number and density of the trees prevent me from figuring out whether I am in a forest, a lumberyard, or a furniture store. This is largely due, I am sure, to my own limited experience in the fields you have touched on. A concise summary of your central point would be useful, not only to me, but perhaps to others also.

[NinaMS]

My argument back is that nature will take the same basic mechanisms and generate complexity from this through evolutionary strategies. You asked for a simplified explanation, so I have set this out below.

 

Photosynthesis and magnetoreception (in species that are able to navigate using the Earth’s magnetic field) are the focuses of study in quantum biology. There is a good introduction to quantum biology at www.nature.com/nphys/journal/v9/n1/full/nphys2474.html

 

Quantum coherence in photosynthesis has been evidenced (actually measured) and is thought to be supporting ultra-fast charge separation. There are plenty of scientific papers exploring this (published on the internet and generally available) but there has been no agreement on what has been behind this effect.

 

Magnetoreception has also been demonstrated in a number of species, and there are many peer reviewed papers out there that have explored the theory that magnetoreception is based on quantum mechanics. However, there been no actual measurement of quantum coherence in magnetoreception as yet. There are two main theories of what might trigger a quantum version of magnetoreception, one which involves a light dependent flavoprotein called cryptochrome and the generation of radical pairs.

 

In the case of the cryptochrome theory, a short-lived radical pair (magnetically sensitive chemical intermediates formed by photoexcitation of cryptochrome proteins) would interconvert coherently between its electronic singlet and triplet states in such a way that the yields of its reaction products would be influenced by weak magnetic fields.

 

What the above posting describes are findings in photosynthesis of a radical pair mechanism resulting in reduced triplet product yield and that this could be connected to the quantum mechanical effects found in photosynthesis. The solid state photo CIDNP effect is thought to be based on a radical pair mechanism - and this effect potentially offers bacteria and plants a form of protection from damaging oxidative stress.

 

The findings that the solid state photo CIDNP effect is also present in Escherichia coli photolyase, and the bluelight photoreceptor phototropin LOV1-C57S, and the possibility it may be present in cryptochrome (both photolyases and cryptochromes are from the same 'family'), may mean that the same quantum effect is supporting both quantum mechanics in photosynthesis and magnetoreception.

 

The finding that cysteine residues may be involved a newly discovered protective/quenching effect in the green sulphur bacteria (which has already demonstrated the solid state photo CIDNP effect) is of interest as it could through more light on the above. The cysteine mediated mechanism could be a completely different protective effect from that of the solid state photo CIDNP effect - but there is also the possibility the two could be related. In mutant plant cryptochrome it has been found that cysteine can act as a gatekeeper for proton transfer and it has been concludes that the formation of the flavin anion radical as the photoproduct is a consequence of a blockage of proton transfer by cysteine. A Hense 2015.

 

These cysteine mediated effect also shows a possible role for cysteine residues in the redox activity of the pigment-protein complex. Generally the coupling between circadian rhythms and the metabolism/redox is recognised within biology, although a relatively new development. Such an effect could support the concept of environmentally assisted quantum transport (ENAQT) which is thought to take place in the FMO complex of the green sulphur bacteria). The idea behind ENAQT is that optimally efficient networks are not purely quantum, but assisted by interaction with a 'noisy' classical environment. A coupled redox - circadian system could potentially offer this combination.

 

I hope that makes more sense to you - if you click into the links in the first posting, you will find the accompanying theory and evidence from these fields.

[Strange]

I'm not sure what your point is. Yes, quantum effects are important in some aspects of biochemistry. But, ultimately, all chemistry is due to quantum effects.

 

So ... what exactly ...

 

Perhaps you could summarise your main point in a sentence or two?

[NinaMS]

Yes you are right, but the field of quantum biology is seeking to demonstrate that that quantum mechanics plays an important role in biological processes and evolution. My posting attempts to support this approach. I cant sum up the implications of quantum biology in a sentence or two, so if you are interested in finding out more I would recommended

 

www.nature.com/nphys/journal/v9/n1/full/nphys2474.html or http://richannel.org/jim-al-khalili--quantum-life-how-physics-can-revolutionise-biology

[Strange]

Yes you are right, but the field of quantum biology is seeking to demonstrate that that quantum mechanics plays an important role in biological processes and evolution.

 

 

 

Yes, that is what quantum biology is. And ...

 

Was there something particular you wanted to discuss about it? (For example, I can't see any connection to the thread title in anything you have posted so far.)

[NinaMS]

Only further evidence will tell whether the links that J Matysik has made between the protective effect described and ultra fast electron transfer in photosynthesis or the suggestions that this effect might support both photosynthesis and magnetoreception by Iannis K Kominis are more than speculation. It is one avenue that is being explored, among the many avenues being explored in quantum biology. Until one is proven correct they are all speculation. That is why I started my first post with 'could'? If you still unable to see how the posting might connect to the title of this thread, then I haven't got anything else to add. Perhaps any posting discussing an area that isn't widely accepted within the scientific community should be moved to the speculation section of this website. If that was the case I would accept that this thread should be within that grouping. However, from what I have seen from the posts on this forum there are plenty of discussions with less substance than this one, and they would all need to be moved across for the sake of consistency. Thank you.

[Strange]

 

 

Perhaps any posting discussing an area that isn't widely accepted within the scientific community should be moved to the speculation section of this website.

 

I think that is only for people proposing their own hypotheses/theories, not for discussion of scientific hypotheses that have not been confirmed.

 

So is the question about whether photosynthesis and magnetoreception could have evolved from the same source? (Thanks for clarifying. I would never have been able to pick that out of the dense list of references to other work that you provided in your first couple of posts.)

 

Perhaps someone with relevant expertise will comment now that is clearer...

[Endy0816]

Cross posted.

Edited October 24, 2016 by Endy0816