Ultra-weak photon emission

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The term ultra-weak photon emission of chemiluminescence (UPE, ultra- weak chemiluminescence , English: spontaneous chemiluminescence, ultraweak light emission, ultraweak photoemission, dark photoemission, low-level luminescence ) is an extremely low- intensity spontaneous or externally inducible photon emission ( luminescence ) which accompanies chemical reactions. which is only slightly above the technical verifiability and is investigated in the scientific branch of biophotonics . The characteristic low luminance of the ultra-weak photon emission is below the perception threshold even of the dark-adapted eye .

This light emission can be observed with inanimate matter as well as with biological material , in the latter case one speaks of ultra-weak cell radiation . The ultra-weak photon emission in biological systems is to be regarded as a product of physiological chemical reactions and their change over time as a response to exogenous influences or the presence of noxious substances .

The ultra-weak chemiluminescence differs in its spectrum , its radiation intensity and its chemiluminescence quantum yield both from the thermal radiation (see Stefan-Boltzmann law ), as well as from the much more intense bioluminescence (with more than one million photons / cm² and second, e.g. Luciferin –Luciferase – System) and fluorescence .

This article does not address the special so-called biophoton hypothesis of the German physicist Fritz-Albert Popp .

properties

The radiation observed so far was 1 to 1000 photons / cm 2 (typically: a few to a few hundred photons / cm 2 ) per second in the spectral range from 200 nm to 800 nm. The radiation power is in the range from 10 −21 W to 10 −18 watts . This means about one photon emission per cell (assumed diameter: 10 micrometers) and month. In order to be able to measure in this area, individual photons must be detectable. The intensity is almost static over time, but in biological systems, like other parameters, it can be subject to circadian fluctuations and other biological rhythms and make these detectable non-invasively.

According to Campbell (1988), the prerequisite for chemiluminescence in general is the presence of:

  • exothermic chemical reactions that deliver between 160 and 300 kJ / mol of energy
  • Presence of molecules in a suitable excited state , which allows either direct photon emission or the transfer of energy to suitable fluorophores in the phenomenon of fluorescence
  • The activated species must be able to be deactivated at least partially by the emission of photons.

The efficiency of the underlying chemiluminescence reactions is described by the chemiluminescence quantum yield. This is very low for both the spontaneous and the induced ultra-weak chemiluminescence. This is a distinguishing feature for more efficient and more intensive bioluminescence with a higher chemiluminescence quantum yield (up to 0.5). This value corresponds to the quotient of the number of emitted photons and the number of reacting molecules.

Development of the spontaneous ultra-weak photon emission in the context of chemiluminescence

The spontaneous ultra-weak chemiluminescence is an emission of photons without external excitation. The formation is explained as a side effect of oxidative processes (e.g. in metabolic processes). Alternative explanations can also be found in the above-mentioned biophoton hypothesis. The continuous cell metabolism leads to the ongoing formation of so-called free radicals , which are of crucial importance in this phenomenon. The formation of free radicals (reactive oxygen compounds) promotes the emission of light, whereby the ambient light and the temperature influence the phenomenon. A supply of vitamin E or other so-called radical scavengers reduces the photon emission. Well-known molecules that are involved in the development of the phenomenon are lipid peroxides.

Induced weak photon emission and induced chemiluminescence

This is a much more intense and technically easier to detect photon emission after an external excitation. The suggestion can e.g. B. by UV radiation , the supply of ozone or peroxides . The induced chemiluminescence can also persist for a while after the effect of a noxious substance and is then also referred to as delayed light emission (so-called light storage behavior ), although a phenomenon of photon storage is unknown, since photons by definition move (in a vacuum) at the speed of light . Initial values ​​can be several powers of ten above the spontaneous values ​​with decay times of around 2–5 minutes. For this purpose, UV radiation is often used, which is known to lead to the formation of free radicals. However, the exact mechanisms of UV-induced chemiluminescence are not known to a satisfactory extent. According to current data, the generation of reactive oxygen radicals after UV irradiation and the subsequent oxidative modification of macromolecules are responsible for the emission of photons. In addition to UV radiation, other stressors such as B. ozone, hydrogen peroxide and benzoyl peroxide are known inducers. As early as 1980, Rudolf Teubner was researching with radiation with daylight lamps to measure food for various quality criteria, description 1983.

The absorption of UV radiation to emit photons of greater wavelengths is known as photoluminescence .

Importance and uses

The measurement of the ultra-weak photon emission is possible with sensitive photomultipliers and avalanche photodiodes (in the so-called Geiger mode ) and is particularly suitable for the non-invasive detection of oxidative processes in biological material. Today secondary electron multipliers (SEV / photomultiplier) are used for measurements . You can show a highly sensitive cathode material in which even single photons can knock out electrons via the external photoelectric effect . A downstream dynode assembly can then implement amplification factors of several million in order to obtain usable measurement signals. The spectral investigation of the measured ultra-weak photon radiation represents a particular problem area. Conventional filter and interference methods can not be used due to the low photon currents.

The determination of the intensity of the ultra-weak photon emission has been used in recent years primarily for the investigation of UVA- induced damage and the quantification of the antioxidative potential of topically applied active ingredients in medicine.

literature

  • RC Allen: Chemiluminescence and the study of phagocyte redox metabolism. In: Adv Exp Med Biol. 141, 1982, pp. 411-421.
  • R. Teubner: To determine the quality of useful plants, especially medicinal plants, with the help of ultra-weak photon emission. Dissertation . Göttingen 1983.
  • D. Slawinska, J. Slawinski: Low-level luminescence from biological objects. In: JG Burr (Ed.): Clinical and biological analysis chemi- and bioluminescence. Marcel dekker, New York / Basel 1985.
  • Campbell AK: Chemiluminescence, Principles and applications in biology and medicine. Ellis Horowood, Chichester, England 1988.

Individual evidence

  1. ↑ KD Gundermann, F. Mc. Capra: Chemiluminescence in Organic Chemistry. Springer, Berlin / Heidelberg 1987.
  2. ↑ GM Barenboim, AN Domanskii, KK Turoverov: Luminescence of Biopolymers and Cells. Plenum Press, New York / London 1969.
  3. ↑ Èva Hideg: On the spontaneous light emission Ultraweak of plants. In: Journal of Photochemistry and Photobiology. B: Biology. Volume 18, Issues 2-3, May 1993, pp. 239-244.
  4. ^ G. Cilento, W. Adam: From Free Radicals to Electronically Excited Species. In: Free Radical Biology and Medicine . 19 (1), 1995, pp. 103-114.
  5. ↑ É. Hideg, Olof Björn: Ultraweak light emission, free radicals, chilling and light sensitivity. In: Physiologia Plantarum. Vol 98, Number 2, October 1996, pp. 223-228.
  6. ↑ F. Ursini, R. Barsacchi, G. Pelosi, A. Benassi: Oxidative stress in the Rat Heart, Studies on Low-Level Chemiluminescence. In: Journal of Bioluminescence and Chemiluminescence. 4 (1), 1989, pp. 241-244.
  7. ↑ R. Barsacchi, M. Coassin, M. Maiorino, G. Pelosi, C. Simonelli, F. Ursini: Increased ultra weak chemiluminescence emission from rat heart at postischemic reoxygenation: protective role of vitamin E. In: Free Radic Biol Med. 6 (6), 1989, pp. 573-579.
  8. ↑ Karin Bieske: Measurements of ultra-weak photon flows. 1999. (PDF; 455 kB)
  9. ↑ Faryar Khabiri: Investigation of oxidative processes using induced ultra- weak photon emission (UPE). Dissertation. 2005. (PDF; 3.4 MB)
  10. ↑ P. Evelson, CP Ordonez, S. Llesuy, A. Boveris: Oxidative stress and in vivo chemiluminescence in mouse skin exposed to UVA radiation. In: J Photochem Photobiol. B 38, 1997, pp. 215-219.