Biophotons (from the Greek βίος meaning "life" and φῶς meaning "light") are photons of light in the ultraviolet and low visible light range that are produced by a biological system. They are non-thermal in origin, and the emission of biophotons is technically a type of bioluminescence, though bioluminescence is generally reserved for higher luminance luciferin/luciferase systems. The term biophoton used in this narrow sense should not be confused with the broader field of biophotonics, which studies the general interaction of light with biological systems.
Biological tissues typically produce an observed radiant emittance in the visible and ultraviolet frequencies ranging from 10−17 to 10−23 W/cm2 (approx 1-1000 photons/cm2/second). This low level of light has a much weaker intensity than the visible light produced by bioluminescence, but biophotons are detectable above the background of thermal radiation that is emitted by tissues at their normal temperature.
While detection of biophotons has been reported by several groups, hypotheses that such biophotons indicate the state of biological tissues and facilitate a form of cellular communication are still under investigation, and claims that biophotons are responsible for physical healing are unsupported. Alexander Gurwitsch, who discovered the existence of biophotons, was awarded the Stalin Prize in 1941 for his mitogenic radiation work.
Detection and measurement
Biophotons may be detected with photomultipliers or by means of an ultra low noise CCD camera to produce an image, using an exposure time of typically 15 minutes for plant materials. Photomultiplier tubes have also been used to measure biophoton emissions from fish eggs, and some applications have measured biophotons from animals and humans. 
The typical observed radiant emittance of biological tissues in the visible and ultraviolet frequencies ranges from 10−17 to 10−23 W/cm2 with a photon count from a few to nearly 1000 photons per cm2 in the range of 200 nm to 800 nm.
Proposed physical mechanisms
Chemi-excitation via oxidative stress by reactive oxygen species and/or catalysis by enzymes (i.e., peroxidase, lipoxygenase) is a common event in the biomolecular milieu. Such reactions can lead to the formation of triplet excited species, which release photons upon returning to a lower energy level in a process analogous to phosphorescence. That this process is a contributing factor to spontaneous biophoton emission has been indicated by studies demonstrating that biophoton emission can be increased by depleting assayed tissue of antioxidants or by addition of carbonyl derivatizing agents. Further support is provided by studies indicating that emission can be increased by addition of reactive oxygen species.
Imaging of biophotons from leaves has been used as a method for Assaying R Gene Responses. These genes and their associated proteins are responsible for pathogen recognition and activation of defense signaling networks leading to the hypersensitive response, which is one of the mechanisms of the resistance of plants to pathogen infection. It involves the generation of reactive oxygen species (ROS), which have crucial roles in signal transduction or as toxic agents leading to cell death.
Biophoton have been observed in stressed plant's roots, too. In healthy cells, the concentration of ROS is minimized by a system of biological antioxidants. However, heat shock and other stresses changes the equilibrium between oxidative stress and antioxidant activity, for example, the rapid rise in temperature induces biophoton emission by ROS.
Hypothesized involvement in cellular communication
In the 1920s, the Russian embryologist Alexander Gurwitsch reported "ultraweak" photon emissions from living tissues in the UV-range of the spectrum. He named them "mitogenetic rays" because his experiments convinced him that they had a stimulating effect on cell division.
Biophotons were claimed to have been employed by the Stalin regime to diagnose cancer. The method has not been tested in the West. However, failure to replicate his findings and the fact that, though cell growth can be stimulated and directed by radiation this is possible only at much higher amplitudes, evoked a general skepticism about Gurwitsch's work. In 1953 Irving Langmuir dubbed Gurwitsch's Mitogenetic Rays pathological science. Commercial products, therapeutic claims and services supposedly based on his work appear at present to be best regarded as such.
But in the later 20th century Gurwitsch's daughter Anna, Colli, Quickenden and Inaba separately returned to the subject, referring to the phenomenon more neutrally as "dark luminescence", "low level luminescence", "ultraweak bioluminescence", or "ultraweak chemiluminescence". Their common basic hypothesis was that the phenomenon was induced from rare oxidation processes and radical reactions.
In the 1970s Fritz-Albert Popp and his research group at the University of Marburg (Germany) showed that the spectral distribution of the emission fell over a wide range of wavelengths, from 200 to 750 nm. Popp proposed that the radiation might be both semi-periodic and coherent.
One biophoton mechanism focuses on injured cells that are under higher levels of oxidative stress, which is one source of light, and can be deemed to constitute a "distress signal" or background chemical process is yet to be demonstrated. The difficulty of teasing out the effects of any supposed biophotons amid the other numerous chemical interactions between cells makes it difficult to devise a testable hypothesis. A 2010 review article discusses various published theories on this kind of signaling.
Many claims with no scientific proof have been made for cures and diagnosis using biophotons. An appraisal of "biophoton therapy" by the IOCOB notes that biophoton therapy claims to treat a wide variety of diseases, such as malaria, Lyme disease, multiple sclerosis, schizophrenia, and depression, but that all these claims remain unproven. F. Popp, a researcher who investigates biophoton emission, concludes that the complexity of cellular chemical reactions in living systems is such that it excludes the possibility to create a machine to selectively heal systems using biophotons, but there are always people who believe in these "miracles."
"The quantum level possesses the highest level of coherence within the human organism. Sick individuals with weak immune systems or cancer have poor and chaotic coherence with disturbed biophoton cellular communication. Therefore, disease can be seen as the result of disturbances on the cellular level that act to distort the cell's quantum perspective. This causes electrons to become misplaced in protein molecules and metabolic processes become derailed as a result. Once cellular metabolism is compromised the cell becomes isolated from the regulated process of natural growth control."
A review of the American Academy of Quantum Medicine concludes that many quantum medicine practitioners are not licensed as health care professionals, that quantum medicine uses scientific terminology but is nonsense, and that the practitioners have created "a nonexistent 'energy system' to help peddle products and procedures to their clients."
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