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A biophoton (from the Greek βιο meaning "life" and φωτο meaning "light") is a photon of light emitted in some fashion from a biological system. Biophotons and their study should not be confused with bioluminescence, as the term "bioluminescence" is generally reserved for higher intensity luciferin/luciferase systems, while "biophoton emission" refers to the more general phenomena of very low-intensity photon emission from living systems. Biophoton emission is synonymous with ultraweak photon emission, low-level biological chemiluminescence, ultraweak bioluminescence, and other similar terms which are together more common in the scientific literature than biophoton.
Common usage of the term
In general usage, the term "biophotonics" refers to the study, research and applications of photons in their interactions within and on biological systems. Topics of research pertain more generally to basic questions of biophysics and related subjects (for example, the regulation of biological functions, cell growth and differentiation, connections to so-called delayed luminescence, and spectral emissions in supermolecular processes in living tissues, etc.).
The term biophoton is used more specifically to denote those photons that are detected by biological probes as part of the general weak electromagnetic radiation of living biological cells. Further terms used for this phenomenon are ultra-weak bioluminescence, dark luminescence, and ultraweak chemiluminescence.
The typical detected magnitude of "biophotons" in the visible and ultraviolet spectrum ranges from a few up to several hundred photons per second per square centimeter of surface area. This is much weaker than in the openly visible and well-researched phenomenon of normal bioluminescence, but stronger than in the thermal, or black body radiation that so-called perfect black bodies demonstrate.
The detection of these photons has been made possible (and easier) by the development of more sensitive photomultiplier tubes and associated electronic equipment.
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 he assumed that they had a stimulating effect on cell division rates of nearby tissue. However, common biochemical techniques as well as the fact that cell growth can generally be stimulated and directed by radiation, though at much higher amplitudes, evoked a general skepticism about Gurwitsch's assumption. Consequently, the mitogenetic radiation hypothesis was largely ignored.
However, after the end of World War II some Western scientists such as Colli (Italy), Quickenden (Australia), Inaba (Japan) returned to the subject of "mitogenetic radiation", but referred to the phenomenon 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. While they added some general chemistry to the hypothesis of photon emission, they did not address the more mysterious assertion of Gurwitsch that the photons themselves, forming the so-called mitogenic rays, stimulated cellular responses.
In the 1970s the then assistant professor Fritz-Albert Popp, and his research group, at the University of Marburg (Germany) offered a slightly more detailed analysis of the topic. They showed that the spectral distribution of the emission fell over a wide range of wavelengths, from 200 to 800 nm. Popp further proposed the hypothesis that the radiation might be both semi-periodic and coherent. This hypothesis has not won general acceptance among scientists who have studied the evidence. Popp's group constructed, tested, patented, and sought to market a device for measuring biophoton emissions as a means of assessing the ripeness and general food value of fruits and vegetables.
Mechanism of biophoton generation
Chemiexcitation via oxidative stress by reactive oxygen species(ROS) and/or catalysis by enzymes (ie peroxidase, lipoxygenase) is a common event in the biomolecular milieu (Cilento, Adam 1995). 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 attenuated by depleting assayed tissue of antioxidants (Ursini et al. 1989) or by addition of carbonyl derivitizing agents (Katoaka et al. 2001). Further support is provided by studies indicating that emission can be increased by addition of reactive oxygen species (ROS) (Boveris et al. 1980).
A model for random photon emissions
In statistical mechanics and modern biology, the favored model of many systems has to do with ensemble phenomena due to a large number of interacting molecules, etc. In chaos theory, for example, it is often suggested that the appearance of randomness in systems is due to a lack of understanding of the larger scheme under which the system responds. Regardless, this has led many who deal with large systems to employ statistics to explain seemingly random events as outlying effects in probability distributions. In this way, since there is normal and openly visible bioluminescence in both many bacteria and other cells (see bioluminescence article) which emit light by particular chemical reactions due to proteins, then it can be inferred that due to the extremely small number of photons in ultra-weak bioluminescence (the numbers given above correspond to roughly a single photon per cell per month, assuming a typical cell diameter of 10 micrometers) that these emissions are simply a random by-product of cellular metabolism.
Since cellular metabolism is thought to occur in a chain of steps in which each step involves small energy exchanges (See ATP), that due to a certain degree of randomness according to the laws of thermodynamics (or statistical mechanics), it must then be expected that, very rarely, some irregular steps can occur. These are referred to as "outlying states." Thus due to occasional physiochemical energy imbalance, a photon is occasionally emitted.
Hypothesized involvement in cellular communication
Russian, German, and other biophotonics experts, adopting the term "biophotons" from Popp, have theorized that they may be involved in various cell functions, such as mitosis, or even that they may be produced and detected by the DNA in the cell nucleus. Proponents of the theory of biophotons claim that experiments have been done which support this hypothesis--e.g., an experiment of Gurwitsch in which growth in one plant seemed to stimulate growth in another across a quartz barrier that blocked chemical messengers, indirectly suggesting that biophotons in the ultraviolet range provided the stimulus. However, debate surrounds such evidence and conclusions, and 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.
Some groups have further speculated that these emissions may be part of a system of cell-to-cell communication, which may be of greater complexity than the modes of cell communication already known. These ideas would then suggest that biophotons may be important for the development of larger structures, such as organs and organisms.
Proponents additionally claim that studies have shown that injured cells will emit a higher biophoton rate than normal cells, and organisms with illnesses will likewise emit a brighter light, which has been interpreted as implying a sort of distress signal being given off. However, injured cells are under higher amounts of oxidative stress, which ultimately is the source of the light, and whether this constitutes a "distress signal" or simply a background chemical process is yet to be demonstrated. One hypothesis is this postulated minor form of communication first became common as single-cell organisms began to cooperate to form complex organisms, using biophotons as a less effective neural system. According to another hypothesis, this form of biophotonic signaling, primarily in the blood, continues to play a role in the reception, transmission, and processing of electromagnetic data.
Skepticism regarding biophotons
Objections to the conjectured signaling role of biophotons include the observation that most organisms are bathed in what would be considered a relatively high intensity light field (daylight or even starlight is orders of magnitude more intense) when compared to any ultraweak biophoton emission, thus swamping any signalling effect such emissions could have.
Usage of term "Biophoton" in non-scientific media
The field of biophoton related study also appears to have recently become rife with new age, alternative medicine, and quantum mysticism claims from those wishing to exploit such claims for financial benefit. Numerous claims are even made that by "harnessing the energy of biophotons" that supposed natural cures for cancer are guaranteed. Mainstream medicine and science strongly reject these claims as outright fraud and a dangerous diversion from actual medical treatment for someone who is suffering from such disease.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Biophoton". A list of authors is available in Wikipedia.|