Life on earth ultimately depends on light. First, light is at the beginning of any food chain, supplying the energy in photosynthesis. Second, vision depends on light sources in the spectral range described by the names of colours (in human terms). The second point is not essential for life, but it makes orientation much more convenient for animals. Due to physical constraints the sun won't shine everywhere, so for special purposes nature invented light sources sustained by biochemical processes. Exergonic chemical reactions dissipate energy - that's why the sun is needed to replenish our ecosystem. Energy dissipation may occur in the form of light, as you know from a bright fire. Living organisms like it somewhat more cool, but still there are oxidative processes controlled by enzymes, in which some energy quantum is emanated in the form of photons. A few proteins causing bioluminescence are known to their atomic structure. Examples of these will be demonstrated here. One example of a light emitting reaction is the oxidation of aldehydes by the enzyme luciferase. A long chain aldehyde reacts with oxygen in the presence of the coenzyme FMN with the generation of one photon per oxidized molecule. Shown here is the structure of luciferase from the marine bacterium Vibrio harveyi. Another example of a light generating enzyme is from a jellyfish, aequorin from Aequorea aequorea. The oxidized substrate is not derived from the general metabolism as in luciferase, but the unique compound coelenterazine, a substituted imidazopyrazinone. It is oxidized by oxygen to the hydroperoxide. Now there is a catch in the enzyme: a hydroperoxide is intrinsically unstable, but by binding it into a pocket of the enzyme the substance is stabilized by means of numerous interactions with functional groups of the protein. Decomposition of the hydroperoxide (along with light emission) is triggered by a conformational change of the protein's structure, releasing some of the interactions. The change in conformation is brought about by the binding of calcium ions. The substrate decomposes to coelenteramide and carbon dioxide, with some reaction energy dissipated as light. Here you find a model of the structure of aequorin with the coelenterazine hydroperoxide bound prior to the binding of calcium ions. Photons emitted in a chemical reaction result from discrete energy states of electrons, as they pass from one excited level to another. Therefore each photon got a fixed amount of energy on its way - that means a fixed wavelength of the light, too. In bioluminescent reactions this is a pale greenish blue, which doesn't penetrate the environment too well. To alert some spectator to the light, a longer wavelength may be more appropiate. In physical terms this means to abstract a fraction of each photon's energy. This may be accomplished by absorbing the light by some chromophore and splitting the energy into a less energetic photon and thermal energy dissipated as heat. Organisms employing aequorin as primary light source face the problem of redshifting the generated light by a substance called green fluorescent protein (GFP). The protein is just the scaffold for the chromophore involved, with the task to protect the dye from environmental influences. Indeeed the fluorescing dye is rather sensitive to the properties of it's surroundings, i.e. to the conformation and composition of the protein shell. This made GFP a toy (or better a tool) for molecular biologists: engineering the protein shell gives the light more or less redshift, thus creating a colorful bunch of transmitters with different efficiencies (quantum yields). Engineering the protein to pH sensitivity turns the system into an intracellular pH-meter. Nature is engaged in this game too, among the variants there are also corals glowing red. Here the structure of GFP of Aequorea victoria is shown. The biochemical effort of red light production is demonstrated with red fluorescing protein. Literature: A Chiesa et al, Recombinant aequorin and green fluorescent protein as valuable tools in the study of cell signalling, Biochem. J. 355 (2001) 1-12 YA Labas et al, Diversity and evolution of the green fluorescent protein family, Proc. Natl. Acad. Sci. USA 99 (2002) 4256-4261 B Stanwood, The Glow, Fawcett Crest (1980) (completely unrelated to blue light emission) Dr. Fun's view of a marine lightshow 3-03 © Rolf Bergmann http://www.papanatur.de/light/introlight.htm
Life on earth ultimately depends on light. First, light is at the beginning of any food chain, supplying the energy in photosynthesis. Second, vision depends on light sources in the spectral range described by the names of colours (in human terms). The second point is not essential for life, but it makes orientation much more convenient for animals. Due to physical constraints the sun won't shine everywhere, so for special purposes nature invented light sources sustained by biochemical processes.
Exergonic chemical reactions dissipate energy - that's why the sun is needed to replenish our ecosystem. Energy dissipation may occur in the form of light, as you know from a bright fire. Living organisms like it somewhat more cool, but still there are oxidative processes controlled by enzymes, in which some energy quantum is emanated in the form of photons. A few proteins causing bioluminescence are known to their atomic structure. Examples of these will be demonstrated here.
One example of a light emitting reaction is the oxidation of aldehydes by the enzyme luciferase. A long chain aldehyde reacts with oxygen in the presence of the coenzyme FMN with the generation of one photon per oxidized molecule. Shown here is the structure of luciferase from the marine bacterium Vibrio harveyi.
Another example of a light generating enzyme is from a jellyfish, aequorin from Aequorea aequorea. The oxidized substrate is not derived from the general metabolism as in luciferase, but the unique compound coelenterazine, a substituted imidazopyrazinone. It is oxidized by oxygen to the hydroperoxide. Now there is a catch in the enzyme: a hydroperoxide is intrinsically unstable, but by binding it into a pocket of the enzyme the substance is stabilized by means of numerous interactions with functional groups of the protein. Decomposition of the hydroperoxide (along with light emission) is triggered by a conformational change of the protein's structure, releasing some of the interactions. The change in conformation is brought about by the binding of calcium ions. The substrate decomposes to coelenteramide and carbon dioxide, with some reaction energy dissipated as light. Here you find a model of the structure of aequorin with the coelenterazine hydroperoxide bound prior to the binding of calcium ions. Photons emitted in a chemical reaction result from discrete energy states of electrons, as they pass from one excited level to another. Therefore each photon got a fixed amount of energy on its way - that means a fixed wavelength of the light, too. In bioluminescent reactions this is a pale greenish blue, which doesn't penetrate the environment too well. To alert some spectator to the light, a longer wavelength may be more appropiate. In physical terms this means to abstract a fraction of each photon's energy. This may be accomplished by absorbing the light by some chromophore and splitting the energy into a less energetic photon and thermal energy dissipated as heat. Organisms employing aequorin as primary light source face the problem of redshifting the generated light by a substance called green fluorescent protein (GFP). The protein is just the scaffold for the chromophore involved, with the task to protect the dye from environmental influences. Indeeed the fluorescing dye is rather sensitive to the properties of it's surroundings, i.e. to the conformation and composition of the protein shell. This made GFP a toy (or better a tool) for molecular biologists: engineering the protein shell gives the light more or less redshift, thus creating a colorful bunch of transmitters with different efficiencies (quantum yields). Engineering the protein to pH sensitivity turns the system into an intracellular pH-meter. Nature is engaged in this game too, among the variants there are also corals glowing red. Here the structure of GFP of Aequorea victoria is shown. The biochemical effort of red light production is demonstrated with red fluorescing protein. Literature: A Chiesa et al, Recombinant aequorin and green fluorescent protein as valuable tools in the study of cell signalling, Biochem. J. 355 (2001) 1-12 YA Labas et al, Diversity and evolution of the green fluorescent protein family, Proc. Natl. Acad. Sci. USA 99 (2002) 4256-4261 B Stanwood, The Glow, Fawcett Crest (1980) (completely unrelated to blue light emission) Dr. Fun's view of a marine lightshow 3-03 © Rolf Bergmann http://www.papanatur.de/light/introlight.htm
Another example of a light generating enzyme is from a jellyfish, aequorin from Aequorea aequorea. The oxidized substrate is not derived from the general metabolism as in luciferase, but the unique compound coelenterazine, a substituted imidazopyrazinone. It is oxidized by oxygen to the hydroperoxide. Now there is a catch in the enzyme: a hydroperoxide is intrinsically unstable, but by binding it into a pocket of the enzyme the substance is stabilized by means of numerous interactions with functional groups of the protein. Decomposition of the hydroperoxide (along with light emission) is triggered by a conformational change of the protein's structure, releasing some of the interactions. The change in conformation is brought about by the binding of calcium ions. The substrate decomposes to coelenteramide and carbon dioxide, with some reaction energy dissipated as light. Here you find a model of the structure of aequorin with the coelenterazine hydroperoxide bound prior to the binding of calcium ions.
Photons emitted in a chemical reaction result from discrete energy states of electrons, as they pass from one excited level to another. Therefore each photon got a fixed amount of energy on its way - that means a fixed wavelength of the light, too. In bioluminescent reactions this is a pale greenish blue, which doesn't penetrate the environment too well. To alert some spectator to the light, a longer wavelength may be more appropiate. In physical terms this means to abstract a fraction of each photon's energy. This may be accomplished by absorbing the light by some chromophore and splitting the energy into a less energetic photon and thermal energy dissipated as heat. Organisms employing aequorin as primary light source face the problem of redshifting the generated light by a substance called green fluorescent protein (GFP). The protein is just the scaffold for the chromophore involved, with the task to protect the dye from environmental influences. Indeeed the fluorescing dye is rather sensitive to the properties of it's surroundings, i.e. to the conformation and composition of the protein shell. This made GFP a toy (or better a tool) for molecular biologists: engineering the protein shell gives the light more or less redshift, thus creating a colorful bunch of transmitters with different efficiencies (quantum yields). Engineering the protein to pH sensitivity turns the system into an intracellular pH-meter. Nature is engaged in this game too, among the variants there are also corals glowing red. Here the structure of GFP of Aequorea victoria is shown. The biochemical effort of red light production is demonstrated with red fluorescing protein. Literature: A Chiesa et al, Recombinant aequorin and green fluorescent protein as valuable tools in the study of cell signalling, Biochem. J. 355 (2001) 1-12 YA Labas et al, Diversity and evolution of the green fluorescent protein family, Proc. Natl. Acad. Sci. USA 99 (2002) 4256-4261 B Stanwood, The Glow, Fawcett Crest (1980) (completely unrelated to blue light emission) Dr. Fun's view of a marine lightshow 3-03 © Rolf Bergmann http://www.papanatur.de/light/introlight.htm
Photons emitted in a chemical reaction result from discrete energy states of electrons, as they pass from one excited level to another. Therefore each photon got a fixed amount of energy on its way - that means a fixed wavelength of the light, too. In bioluminescent reactions this is a pale greenish blue, which doesn't penetrate the environment too well. To alert some spectator to the light, a longer wavelength may be more appropiate. In physical terms this means to abstract a fraction of each photon's energy. This may be accomplished by absorbing the light by some chromophore and splitting the energy into a less energetic photon and thermal energy dissipated as heat. Organisms employing aequorin as primary light source face the problem of redshifting the generated light by a substance called green fluorescent protein (GFP). The protein is just the scaffold for the chromophore involved, with the task to protect the dye from environmental influences. Indeeed the fluorescing dye is rather sensitive to the properties of it's surroundings, i.e. to the conformation and composition of the protein shell. This made GFP a toy (or better a tool) for molecular biologists: engineering the protein shell gives the light more or less redshift, thus creating a colorful bunch of transmitters with different efficiencies (quantum yields). Engineering the protein to pH sensitivity turns the system into an intracellular pH-meter. Nature is engaged in this game too, among the variants there are also corals glowing red. Here the structure of GFP of Aequorea victoria is shown. The biochemical effort of red light production is demonstrated with red fluorescing protein.
