Fluorescence

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Transcript Fluorescence

Fluorescence
Monica
Definitions

Incandescence: light produced when electrons
flow through a filament and bump into its atoms,
releasing mostly heat and some light (1, p 83)
 Luminescence: “emission of light” from a
“substance below the temperature of
incandescence,” or “cold light” (2)
 Fluorescence: “ the conversion of one color of
light to another” (1, p 72)
A “Light” Review

UV light of higher
energy than visible
light
 “Black light” not
actually black; coating
on bulb filters visible
light, so UV light let
through it
Shedding Light on Light

When light energy hits a substance, several
outcomes are possible (1, p 86)
– Substance absorbs light
– Usually, light converted into “molecular
agitation” (heat)
– Light reflected (ex. mirror)
– Light passes through (ex. glass) but is refracted
(bent)
What Causes Fluorescence?

When photon of UV light hits molecule of
fluorescent substance, it absorbs the light and
electrons of the substance are excited and jump to
higher energy level (1, p 87)
 Electrons remain there for a few billionths of a
second before falling back to their lower-energy
orbit
 At its return, each electron reemits a portion of the
light it absorbed, but in visible spectrum
More on Fluorescence

Fluorescence is visible as soon as substance is
exposed to UV light and stops as soon as
stimulating light is removed (2)
 “Emitted fluorescent light has less energy (is redshifted) than the exciting light” (1, p 82)
 This phenomenon is called Stokes’s Shift, named
for George G. Stokes, who discovered
fluorescence (1, p 77, 82)
Fluorescent Minerals
Applications in Geology

Helps in the identification of minerals
 Aids in finding the location of large
deposits of certain minerals
 Useful in distinguishing between natural
and synthetic gems
Forensics




When skin contacts most
surfaces, leaves amino
acids (1, p 87)
Ninhydrin applied and
reacts with amino acids
Fluoresces under UV light
“more sensitive and useful
than the traditional blackpowder method of
detecting fingerprints”
Medical Uses
Fluorescent dyes used to “tag” proteins and
antibodies (1, p 92)
 Allowed further study on rheumatic fever
and other diseases, as well as of proteins
 However, limiting—could only be used on
dead tissue, as dyes and images could not
penetrate deeply without being invasive

The Green Fluorescent
Protein (GFP)

Found in Aequorea
jellyfish (1, p 106)
 Uses traditional
luciferin/luciferase
method of
bioluminescent light
production (69)
 That produces blue
light (72)
GFP

Before blue light visibly emitted, absorbed
by the GFP and reemitted as green light
(105)
 Revolutionary discovery
 Could transfer this gene to other species,
and it would be expressed (121)
 Penetrated much deeper than dyes and
allowed study of living tissue (156-157)
More on the GFP

Can attach GFP to specific types of cells or
parts of cells, so only those sections are
fluorescent (160)
 Altered the GFP to create other colors and
brighter glows (141-143)
 Has been used in plants, worms, frogs, fish,
mice, goats, rabbits, monkeys, flies, beetles,
lampreys, and yeast (127)
Fluorescent Mouse
Uses of GFP
Became a “tool widely used in biomedical
research” (1, p 73)
 Monitor calcium levels in living organisms
(1, p 156-157)
 Examine the progression of Alzheimer’s
plaques in a living mouse brain (1, p 91)
 Watch development of tumors (1, p 54)

Further Uses

Examine sections of brain more closely (1, p 202)
 Develop better understanding of olfactory system
(1, p 208)
 Beginning to develop technology that can be
controlled purely by thought (1, p 224)
 Aim to “develop brain-machine interfacing to a
point where people who no longer have the ability
to move by their own volition can control
prosthetic devices” (1, p 225)
Fluorescence
Recreation

Alba—genetically
engineered rabbit
designed as art and
displayed in 2000 (1, p
157)
 GloFish—genetically
engineered zebrafish
sold commercially in
2002 (1, p 159)
Sources
1. Pieribone, V., Gruber, D. F. Aglow in the Dark: The Revolutionary
Science of Biofluorescence; The Belknap Press of Harvard
University Press: Cambridge, Massachusetts, and London, England,
2005.
2.
Photos:
-title page:
http://www.beseenonabike.co.uk/acatalog/Fluorescence_in_various_
sized_CdSe_quantum_dots.png
More Sources
-electromagnetic spectrum:
http://zebu.uoregon.edu/~imamura/122/images/electromagneticspectrum.jpg
-fluorescent minerals:
http://www.acceleratingfuture.com/michael/blog/images/fluorescent_m
inerals.jpg
-Aequorea jellyfish:
http://elnoticierocientifico.blogia.com/upload/20081204182613-gfp5cgfp-aequorea-victoria-1.jpg
-Fluorescent mouse:
http://foreignerinformosa.typepad.com/the_foreigner_in_formosa/2006
/01/taiwanese_scien.html
Additional Sources
-Mouse with brain tumor:
http://foreignerinformosa.typepad.com/photos/uncategorized/fluoresce
nt_mouse_with_brain_tumor.jpg
-Neurons:
http://forum.richarddawkins.net/viewtopic.php?f=5&t=27935
-Alba the rabbit:
http://www.ekac.org/swissprot/sptlt011_2.jpg
-GloFish:
http://www.bio.davidson.edu/people/kabernd/seminar/2004/GMevents/
WW/glosfishpic2.jpg