Quantum phenomena in the retina, cochlea, macrophages and other biological tissues in vivo ......
Electron tunneling associated with ferritin (electron tunneling) was proposed as early as 1988 and has been viewed with skepticism despite the overwhelming evidence for it.
In a recent paper published in IEEE Molecular, Biological and Multiscale Communications, the co-authors review the evidence for electron tunneling in ferritin and the evidence that this electron tunneling may be used by biological systems including the retina, cochlea, macrophages, glial cells, mitochondria, and magnetic induction systems.
Although these different systems belong to different areas of research, the research team said, "We hope this article will improve understanding of the mechanisms of electron tunneling associated with ferritin and encourage further investigation of this phenomenon in biological systems that incorporate ferritin - particularly in those systems where there is no apparent need for ferritin's iron storage function."
Ferritin is an iron storage protein that self-assembles into a spherical shell 12 nanometers in diameter (2 nanometers thick), which also stores up to about 4,500 iron atoms in a core 8 nanometers in diameter.
Illustration of the protein subunit and core material structure of ferritin.
The evolutionary history of ferritin appears to go back 1.2 billion years (single-celled organisms are thought to have first evolved about 3.5 billion years ago). Thus, ferritin may have evolved more than 2 billion years ago: members of the ferritin family may have been present when the first multicellular organisms evolved about 600 million years ago, and they can be found today in almost all plants and animals.
As early as 1988, it was proposed that ferritin might have some quantum mechanical properties - 88 years after the discovery of quantum mechanics and 8 years after the discovery of quantum dots (quantum dots are semiconductor nanoparticles that behave like artificial atoms and are similar in size to ferritin).
The quantum mechanical properties of ferritin include magnetic behavior due to the way iron forms a crystalline structure in the core of the ferritin shell, and electron tunneling effects.
The formation of Coulomb blocking in the ferritin structure.
However, these properties in this billion-year-old biological structure seem to be mostly considered a curiosity or artifact rather than a quantum biological property. Quantum biology as a study has been viewed skeptically by biologists and many other scientists (although many of the scientists who discovered quantum mechanics more than 100 years ago thought it could be applied to biology), but it is a growing field that is being studied by many top universities: for example, Caltech, Yale, the University of Chicago, and UCLA, among others.
The principle of the tunneling effect.
Quantum mechanics proposes that the physical properties of electrons, protons, neutrons, and other so-called subatomic "particles" are defined in terms of probability waves. Experimental evidence for the wave-like behavior of these particles has been obtained and is generally accepted; these waves are described experimentally as the probability of detecting the physical properties of a particle at some location in time and space, which is sometimes referred to as the "collapse" of the wave function.
However, when a particle collapses, nothing changes except the dynamics of the wave function. A wave function can be called "coherent" when it behaves in accordance with Schrödinger's wave function, and "incoherent" when it interacts with other particles and no longer behaves in accordance with that wave function.
The spatial wave-like properties of electrons in vacuum can have a wavelength of about 5 nm at room temperature, which is important for the interaction of molecules. Electrons can move between molecules, and when they "touch" each other (the wave function of the atoms and subatomic particles in a molecule is the actual interaction), adiabatic or classical behavior may occur; but under the right conditions, an electron can "tunnel" between molecules ": this means that it can move from one molecule to another in a way that adiabatic or classical behavior does not allow.
There is nothing mysterious about this, it is just a physical property of the electron, but since the wave function is a probability wave, this may make it seem mysterious.
Now, this review article shows that electrons appear to pass through ferritin at distances as high as 12 nm in successive tunneling events, and that the unusual magnetic properties of the ferritin core material may be related to this unusually long electron tunneling distance.
This work is based on "solid-state" experiments and does not involve living biological systems. Because electron tunneling cannot be observed directly, it must be inferred from other evidence: measured currents and voltages, for example. In biological systems, it may be more difficult, but not impossible, to obtain evidence of such electron tunneling.
There are several cellular reactions associated with electron tunneling in ferritin.
The first one is electron storage (electron storage). In extracellular laboratory tests ("in vitro"), ferritin's ability to store electrons in aqueous solution has been shown to last for several hours.
-- This is unusual because it is expected that iron stored within ferritin would be released once electrons are received, but this does not occur rapidly. This observation suggests that electrons do not readily move through the insulating protein shell by classical conduction, but rather move electrochemically or tunneling.
The evidence also suggests that in solid-state tests, electrons can travel up to 8 nm through ferritin in a single tunneling event, so it is possible that electrons stored inside the ferritin core can "tunnel" into molecules (such as radicals) outside the 2 nm thick protein shell at energy levels that allow them to accept electrons. These free radicals can acquire electrons from other molecules and cause cellular damage, and neutralizing free radicals by donating electrons is one of the functions of antioxidants.
Ferritin interacts with antioxidants such as ascorbic acid (more commonly known as vitamin C) in the cellular environment in a way that stabilizes stored iron, which is also overexpressed in response to free radicals. If ferritin can store electrons from antioxidants so that they are available to free radicals by way of electron tunneling effects, then it can increase the efficiency of that neutralization reaction by allowing electrons to reach free radicals that are far away and storing them until they are needed.
If the only function of ferritin is to store iron, then this would not make sense in situations where the source of free radicals, inflammation and ROS is not excess iron, which is often the case. The complexity of how cells use iron (i.e., iron homeostasis) makes electron tunneling associated with ferritin difficult to identify.
Another proposed quantum biological function of electron tunneling in ferritin is electron transport across cellular distances. In a type of cell known as an M2 macrophage, ferritin can form a number of regularly ordered structures that macrophages appear to use to deliver ferritin to the cells that the macrophages help. For example, macrophages are associated with increased levels of ferritin associated with some cancers and appear to help cancer cells neutralize inflammation.
Comparison of ferritin structures in a) placental macrophages and b) glial cells.
Antioxidants may also help some cancer cells survive by providing electrons to neutralize free radicals and ROS, but in the absence of antioxidants in these cells, is it possible for electrons to tunnel through the ferritin structure of M2 macrophages into the ferritin of other cells? Evidence for this function also exists.
In a small-angle neutron scattering (SANS) test performed by Dr. Olga Mykhaylyk on placental tissue including macrophages, increased neutron scattering was measured, but not in the large amounts of ferritin extracted from the tissue. Neutron scattering can occur in solids containing nanoparticles with aligned magnetic moments, and these tests indicate that ferritin in placental tissue containing macrophages has aligned magnetic moments.
Routing electrons to ferritin, where they are needed to eliminate free radicals, inflammation and ROS in cells, is another proposed quantum biological function. However, since electron tunneling cannot be directly observed, further studies are needed to investigate this hypothesis.
Evidence of electron tunneling in ferritin-containing neural tissue.
[1]https://ieeexplore.ieee.org/document/10123991
[2]https://phys.org/news/2023-06-electron-tunneling-ferritin-vivo-retina-1.html
