What is Bioluminescence?

Eric Prange

MLFSC 680

Bioluminescence

• Bioluminescence is the production of light without heat through chemical reactions by living organisms. Bioluminescence is often referred to as “cold light.”

• To better understand the process, we first have to understand what light is and how any kind of light is produced.

http://www8.nos.noaa.gov/coris_glossary/index.aspx?letter=p

http://www.cartage.org.lb/en/themes/Sciences/Earthscience/Oceanography/OceanWater/Optics/Optics.htm

The Electromagnetic Spectrum• Visible light is just one region of the electromagnetic spectrum,

which ranges from gamma rays to radio waves. • Light has wave-like and particle like properties. • All electromagnetic light always travels at 3.0 x 108 m/s or “c” the

speed of light and is directly related to the wavelength (“λ”) and frequency (“ν”) of that light.

• All EM radiation is also made up of individual pieces called “photons” which have an energy directly related to the frequency of the light and planks constant (“h”)

C = λ ν E =h ν h = 6.63 x 10-34 J.s

Electrons and Light

• While EM radiation can behave as a particle including being affected by gravity and imparting momentum on other objects, it does not have any mass.

• Electrons, like light have quantized (discrete) energy values that they can exist at.

http://outreach.atnf.csiro.au/education/senior/astrophysics/images/spectra/bohrhydrogen.gif

Electrons and Light (Cont.)• One way that electrons can gain and lose

energy is to absorb and emit photons of light. • Another way is that electrons can gain and

lose energy is by exchanging energy with the kinetic energy of the molecule (or heat).

• Think of it this way; a black shirt feels hotter than a white shirt because its electrons absorbs more light, which is then converted into heat.

• You also know that the metal in the picture to the right is extremely hot because it is glowing. In this case the electrons are absorbing some of the energy and going into an “excited state.” When they return to the “ground state” they give off light.

http://zipser.nl/uploaded_images/DSCF1446-745840.JPG

Energy and Chemical Reactions

• All chemical reactions involve a change in energy from the reactants to the products.

• In most chemical reactions, the products are lower in total energy than the reactants and thus energy must somehow be released to the surroundings.

• In virtually all chemical reactions of this type, this energy is released in the form of heat. These are called exothermic reactions.

An example of an “exothermic reaction”

http://static.howstuffworks.com/gif/fire-breathing-7.jpg

Light and Chemical Reactions

• Some reactions that go from high to low energy are able to instead release the extra energy in the form of photons (or light).

• This unusual class of reactions is largely due to the molecular structure of the intermediates that the reaction goes through and must at some point create a molecule in an excited energy state.

• Two of the most commonly seen examples of chemiluminescence are light sticks and luminol.

http://www.blackhawk.com/images/catalog/NOP_LIGHTSTICKS.jpg

Luminol

• Luminol is mixed with a base (OH-) and hydrogen peroxide (which releases O2) to create a chemiluminescent reaction which emits blue light.

• Because iron acts as a catalyst for this reaction, crime scene investigators can use it to search for the presence of blood since hemoglobin contains iron ions.

• Unfortunately, bleach and copper ions also act as catalysts which can lead to false positives for this test.

The luminol reaction

http://en.wikipedia.org/wiki/Luminol#Chemiluminescence

The Luminol Reaction

The product in this reaction is in an excited state and eventually returns to the ground state by giving off a photon of blue light.

http://en.wikipedia.org/wiki/Luminol#Chemiluminescence

The Light Stick Reaction

1) The chemical reaction above produces excess energy 2) The energy is then transferred to a fluorescent dye, which goes into an excited state. 3) The dye returns to the ground state by releasing a photon of light. 4) The color released depends on the chemical structure of the dye molecule.

http://en.wikipedia.org/wiki/Lightstick

Fluorescence

• Fluorescence is the process in which a molecule absorbs a photon of light and then re-emits a photon of light of lower energy.

• The reason the photon released is lower energy is because a small portion of the energy was converted into the kinetic energy of the molecule (heat).

• With black lights, high energy UV light is absorbed by fluorescent materials and is re-emitted as lower energy visible light.

Bio Fluorescence• A large number of organisms

fluoresce.• One famous example is the Crystal

Jellyfish which can emit blue light through bioluminescence. The blue light is then absorbed by “green fluorescent protein” (GFP) and re-emitted as green light.

• Biologists have discovered how to transfer the GFP gene to other organisms so that they glow green when exposed to UV light.

• The GFP molecule can also be attached to macro bio-molecules in order to trace them as they move throughout cells.

Works Cited• http://en.wikipedia.org/wiki/Electromagnetic_radiation

• http://www8.nos.noaa.gov/coris_glossary/index.aspx?letter=p

• http://www.cartage.org.lb/en/themes/Sciences/Earthscience/Oceanography/OceanWater/Optics/Optics.htm

• http://outreach.atnf.csiro.au/education/senior/astrophysics/images/spectra/bohrhydrogen.gif

• http://zipser.nl/uploaded_images/DSCF1446-745840.JPG

• http://www.blackhawk.com/images/catalog/NOP_LIGHTSTICKS.jpg

• http://en.wikipedia.org/wiki/Luminol#Chemiluminescence

• http://en.wikipedia.org/wiki/Lightstick

• http://jellieszone.com/aequorea.htm

• http://hvd.ens-lyon.fr/human_virology_dpt/teams/gs_verel/pr_verel/vectors_verel