Quantum Biology: Latest News!

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Photosynthesis

November 2015

Theoretical work by a collaborative group comprising scientists from the Universities of Miami, Los Andes and Ulm suggests that photosynthesis systems exploit spatial coherence in nearby photons to capture the maximum amount of light energy. The structure of photosystems seems to be optimal to take advantage of spatially-correlated photons – yet more evidence that the molecular mechanisms of life have evolved the in the quantum world.

Authors: Pedro Manrique, Adriana De Mendoza, Felipe Caycedo-Soler, Ferney Rodrıguez, Luis Quiroga, Neil Johnson

 Title: Spatial coherence of thermal photons favors photosynthetic

Abstract:Harvesting of sunlight underpins Life on Earth as well as driving novel energy device design. Though several experiments suggest that excitation energy transport and charge separation within a

photosynthetic membrane may benefit from the quantum nature of their dynamics, the effects of
spatial coherences in the incident light have been largely ignored. Here we show that spatial correlations in
the incident light likely play an important role in trapping light and adding robustness, as well as providing
a driving mechanism for an organism’s adaptation toward more ordered structures. Our theory is grounded
by empirical inputs, while its output is validated against testable predictions. Our results suggest that
spatiotemporal correlations between photons, a fundamental property of the quantum world, should play a
key role in our understanding of early Life and in improving the design of artificial photosynthetic systems.
Reference: http://arxiv.org/pdf/1511.07309.pdf

 

December 2014

Martin Plenio’s, group published an interesting paper on the principle, outlined in LOTE, that photosynthesis may harness coherent vibrations to act as a quantum heat engine capable of obtaining a higher efficiency than classical heat engines.

Authors: N. Killoran, S. F. Huelga, and M. B. Plenio.

Title: Enhancing light-harvesting power with coherent vibrational interactions: a quantum heat engine picture.

Abstract: Recent evidence suggests that quantum e ects may have functional importance in biological light-
harvesting systems. Along with delocalized electronic excitations, it is now suspected that quantum
coherent interactions with certain near-resonant vibrations contribute to light-harvesting perfor-
mance. However, the actual quantum advantage o ffered by such coherent vibrational interactions
has not yet been established. We investigate a quantum design principle, whereby coherent ex-
change of single energy quanta between electronic and vibrational degrees of freedom can enhance a
light-harvesting system’s power above what is possible by thermal mechanisms alone. We present a
prototype quantum heat engine which cleanly illustrates this quantum design principle, and quantify
its quantum advantage using thermodynamic measures of performance. We also demonstrate the
principle’s applicability for realistic biological structures.

Reference: arXiv:1412.4136v1

Genes

November, 2015

Long-range energy transport via quantum coherence is a key feature of photosynthesis but now long range energy transport, ‘quantum unfurling’, has now also been discovered to occur along the DNA double-helix .

Authors: Ariel D. Levine,   Michael Iv and   Uri Peskin
Title: Length-independent transport rates in biomolecules by quantum mechanical unfurling
Abstract:
Experiments on hole transfer in DNA between donor and acceptor moieties revealed transfer rates which are independent of the molecular bridge length (within experimental error). However, the physical origin of this intriguing observation is still unclear. The hopping model implies that the hole propagates in multiple steps along the bridge from one localized state to another, and therefore the longer the bridge, the slower the transfer. This can explain weak length-dependence but not a length-independent transfer rate. We show that the rigid molecular structure of a poly-A bridge supports single step transitions from a localized hole state to delocalized states, spread over the entire bridge. Since propagation to the bridge end is a single step process (termed quantum unfurling) the transfer rate becomes independent of the bridge length. This explanation is consistent with experimental results, and emphasizes the importance of structural order in charge transfer through bio-molecular systems.
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Reference: Chem. Sci., 2016, Advance Article

 

 

Enzyme Catalysis

enzyme

A whole slew of papers was published in the December 2014 issue of ‘Accounts of Chemical Research’ focussing on examing the role of protein motion in catalysis. As we describe in LOTE, protein tunnelling in enzymes is thought to be enhanced by vibrational protein motions that bring substrates and enzymes close enough to allow tunnelling of protons across trelatively large gaps to thereby enhance the rate of catalysis. One of the papers is from one of the founders of this field, Judith Klinman from the University of Berkeley.

Author: Judith P. Klinman

Title: Dynamically Achieved Active Site Precision in Enzyme Catalysis

Abstract: The grand challenge in enzymology is to define and understand all of the parameters that contribute to enzymes’ enormous rate
accelerations. The property of hydrogen tunneling in enzyme reactions has moved the focus of research away from an exclusive focus on transition state stabilization toward the importance of the motions of the heavy atoms of the protein, a role for reduced barrier width in catalysis, and the sampling of a protein conformational landscape to achieve a family of protein substates that optimize enzyme−substrate interactions and beyond.
This Account focuses on a thermophilic alcohol dehydrogenase for which the chemical step of hydride transfer is rate determining across a wide range of experimental conditions. The properties of the chemical coordinate have been probed using kinetic isotope effects, indicating a transition in behavior below 30 °C that distinguishes nonoptimal from optimal C−H activation. Further, the introduction of single site mutants has the impact of either enhancing or eliminating the temperature dependent transition in catalysis. Biophysical probes, which include time dependent hydrogen/deuterium exchange and fluorescent lifetimes and Stokes shifts, have also been pursued. These studies allow the correlation of spatially resolved transitions in protein motions with catalysis. It is now possible to define a long-range network of protein motions in ht-ADH that extends from a dimer interface to the substrate binding domain across to the cofactor binding domain, over a distance of ca. 30 Å. The ongoing challenge to obtaining spatial and temporal resolution of catalysis-linked protein motions is discussed.

Reference: Acc. Chem. Res., Article ASAP. DOI: 10.1021/ar5003347

 

Bird Navigation

robin

 

November, 2015

The identity of the avian magnetic compass has remained a mystery for over a century. Earlier work favoured the idea that bird’s may possess some kind of conventional compass, perhaps crystals of magnetite that align with the earth’s magnetic field. However, the heroes of our avian compass story, the husband and wife team of Roswitha and Wolfgang Wiltschko demonstrated that European robins possess an inclination compass that cannot be accounted for by a conventional compass needle. In LOTE we describe the quantum entangled free radical model of the avian compass, a story put together from classic ornithology studies, genetic studies on fruit flies and butterflies, inovative chemistry of Klaus Schulton and theoretical and experimental studies from Thursten Ritz and colleagues, which demonstrated that the European robin’s compass was disrupted by high frequency radio waves, as predicted by the quantum entanglment theory. Since then, the avian compass has been the poster child of quantum biology. However, the precise molecular identity of the magnetic receptor in the bird’s eye has remained mysterious, although the  cryptochrome protein, shown to be present in the bird’s eye, has been implicated as a likely candidate.

A recent paper by Chinese scientists claims to have found the found the magnetic compass needle. a rod-shaped complex of proteins including both an iron-binding protein, MagR and cyyptochome that, they domonstrate, can align with Earth’s weak magnetic field.

nature-nmat4484-graphicfrom: http://www.nature.com/news/discovery-of-long-sought-biological-compass-claimed-1.18803

Title: A magnetic protein biocompass

Authors: Siying Qin et al.

Abstract:

The notion that animals can detect the Earths magnetic field was once ridiculed, but is now well established. Yet the biological nature of such magnetosensing phenomenon remains unknown. Here, we report a putative magnetic receptor (Drosophila CG8198, here named MagR) and a multimeric magnetosensing rod-like protein complex, identified by theoretical postulation and genome-wide screening, and validated with cellular, biochemical, structural and biophysical methods. The magnetosensing complex consists of the identified putative magnetoreceptor and known magnetoreception-related photoreceptor cryptochromes (Cry), has the attributes of both Cry- and iron-based systems, and exhibits spontaneous alignment in magnetic fields, including that of the Earth. Such a protein complex may form the basis of magnetoreception in animals, and may lead to applications across multiple fields.

Reference: Nature Materialsdoi:10.1038/nmat4484

 

December 2014

Roswitha and Wolfgang Wiltschko published a new experimental paper that sought to explore the molecular mechanism behind their previous demonstration, with Thorsten Ritz, that the avian magnetic compass was disrupted by high frequency magnetic fields.  As we descriibe in LOTE, Ritz proposed that this was due to disruption of quantum entanglement in cryptochrome molecules in the bird’s eyes that, the team proposed, are involved in detecting the earth’s very weak magnetic field. However, there may be other possible explanations for this sensitivity, for example, the fields could disrupt the photoreduction of cryptochrome. In this paper the team demonstrated that high frequency fields did not affect photoreduction of cryptochome, making an entanglement mechanism a bit more more likely.

Title: Magnetoreception in birds: the effect of radio-frequency fields’s

Authors: Wiltschko R, Thalau P, Gehring D, Nießner C, Ritz T, Wiltschko W.

Title: Magnetoreception in birds: the effect of radio-frequency fields.

Abstract: The avian magnetic compass, probably based on radical pair processes, works only in a narrow functional window around the local field strength, with cryptochrome 1a as most likely receptor molecule. Radio-frequency fields in the MHz range have been shown to disrupt the birds’ orientation, yet the nature of this interference is still unclear. In an immuno-histological study, we tested whether the radio-frequency fields interfere with the photoreduction of cryptochrome, but this does not seem to be the case. In behavioural studies, birds were not able to adjust to radio-frequency fields like they are able to adjust to static fields outside the normal functional range: neither a 2-h preexposure in a 7.0 MHz field, 480 nT, nor a 7-h pre-exposure in a 1.315MHz field, 15 nT, allowed the birds to regain their orientation ability. This inability to adjust to radio-frequency fields suggests that these fields interfere directly with the primary processes of magnetoreception and therefore disable the avian compass as long as they are present. They do not have lasting adverse after-effects, however, as birds immediately after exposure to a radio-frequency field were able to orient in the local geomagnetic field.

Reference: J. R. Soc. Interface 12: 2014 1103. http://dx.doi.org/10.1098/rsif.2014.1103

 

brain

Consciousness

In LOTE we discuss how quantum coherent ion channels may be linked via the brain’s electromagnetic (EM) field. I, and others. have proposed that consciousness may be seated in the EM fields generated by brain firing, the kind of fields that are picked up by brain-scanning techniques, such as EEG and measurement of ‘local field potentials’ (see consciousness page) but they are also the principle means by which revolutionary forms of brain augmentation hardware aims to interact with the brain. However, perhaps surprisingly given their importance, the origin of these EM fields is still not clear.  One of the  scientists to propose an EM field theory of consciousness is Sue Pockett from the University of Aukland. She has just published a useful review paper on the origin of local field potentials.

Authors: Colin G. Hales and Susan Pockett

Title: The relationship between local field potentials (LFPs) and the electromagnetic fields that give rise to them.

Reference: Front. Syst. Neurosci., 12 December 2014 | doi: 10.3389/fnsys.2014.00233

Sue has also recently published an interesting opinion paper arguing that theories, such as my own cemi field theory, that equate consciousness with information are flawed.

Author: Susan Pockett

Title: Problems with theories that equate consciousness with information or information processing.

Abstract: Attempts to augment the function of the human brain inevitably involve in some way what Block (1995) calls phenomenal consciousness—bodily sensations and perceptual experiences—the redness of a strawberry, the smell of newly-baked bread. At present there is no consensus among scientists about what such sensory experiences are. This Opinion piece points out some problems with one of the major
theatrical viewpoints on that question.

[end of abstract]

Needless to say, I do not agree with Sue. Her central argument is that information is abstract rather than ‘concreta’ and this creates a fundamental problem then linking it to physical processes. I agree. But I take the opposing view, now widely accepted in physics, that, as computing pioneer Rolf Landauer declared in 1991 ‘information is physical’. Information is always physical and instantiated in particles, fields etc. It is therefore not a problem to assign real properties, such as awareness/consciousness, to integrated electromagnetic information as in my cemi field theory, so long as the information is indeed physical, which it is.