Hey, if Im going to insult myself, I may as well pick on you too

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More photochemistry!!
Hey, if Im going to insult myself, I may as
well pick on you too!
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Fates of Electronically Excited States

• Excited states can undergo many processes
• 1) Dissociation / Predissociation
• 2) Fluorescence / Phosphorescence / Internal
  Conversion
• In the gas phase, these are usually the only
  important processes
• However, in the solution phase
• Collisional Quenching (vibrational relaxation)
• Collisional Deactivation (excitation
  transferred to collision partner)

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Jablonski Diagram
http//www.shsu.edu/chemistry/chemiluminescence/J
ABLONSKI.html
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Collisional Quenching
Figure 1. Pictorial representation of the
ANTS/DPX vesicle-fusion assay.
Originally developed by Smolarsky and co-workers
to follow complement-mediated immune lysis,   the
ANTS/DPX fluorescence quenching assay has since
been widely used to detect membrane fusion.  This
assay is based on the collisional quenching of
the polyanionic fluorophore ANTS by the cationic
quencher DPX (Figure 1). Separate vesicle
populations are loaded with 25 mM ANTS (A350) in
40 mM NaCl and 90 mM DPX (X1525).
Vesicle
http//probes.invitrogen.com/handbook/boxes/0437.h
tml
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http//www.eurogentec.com/EGT/Images/beacons.gif
Molecular Beacons are probes which contain a
stem-loop structure, a fluorophore and a quencher
at their 5 and 3 ends, respectively.  The
stem sequence keeps the fluorophore and the
quencher together, but only in the absence of a
sequence complementary to the loop sequence. As
long as the fluorophore and the quencher are in
close vicinity, any photons emitted by the
fluorophore are absorbed by the quencher. This
phenomenon is called collisional (or proximal)
quenching. In the presence of a complementary
sequence, the probe unfolds and hybridizes to the
target, the fluorophore is displaced from the
quencher, which can no longer absorb the photons
emitted by the fluorophore, and the probe starts
to fluoresce.
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http//www.htrf.com/technology/htrftheory/
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http//www.icms.qmul.ac.uk/flowcytometry/uses/FRET
/
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http//www.kcci.virginia.edu/FRET-FLIM/index.php
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Figure 1. FRET efficiency and time-resolved
changes in the FRET signal of PTHR-cam.(a)
Overall transmembrane topology of the GPCR-cam
constructs. (b) Fluorescence emission spectra of
selected PTHR constructs. Shown are the emission
spectra of PTHR-CFP3-loop (blue), PTHR-YFPC-term
(yellow), simultaneous PTHR-CFP3-loop
PTHR-YFPC-term (black), and PTHR-cam (red) upon
excitation at 433 nm.
(d) Time-resolved changes in the ratio F 535/F
480 in single HEK293 cells stably expressing
PTHR-cam. Emission intensities of YFP (535 nm,
yellow), CFP (480 nm, blue) and the ratio F
535/F 480 (red) were recorded simultaneously
from single cells.
Nature Biotechnology  21, 807 - 812 (2003)
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Cos-7 cells were transfected with expression
vectors for PPARalpha-ECFP and RXRalpha-EYFP.
(Upper panel) Images of two cells expressing both
PPAR-ECFP and RXR-EYFP in the CFP and YFP
settings. A Gaussian blur of 1 was applied to the
original image. (Lower panel) NFRET and expNFRET
images generated by the PixFRET plug-in. The
cells are pseudo-colorized with a different look
up table to better visualize intensity
differences.
http//www.unil.ch/cig/page16989.html
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Black Light
Ultraviolet light is invisible, but black lights
or UV-lamps also emit some visible violet
light. Many fluorescent and phosphorescent
materials absorb and re-emit the energy from an
ultraviolet lamp, sometimes called a 'black
light' because the ultraviolet light is not
visible.
http//chemistry.about.com/od/imagesclipartstructu
res/ig/Fluorescence---Phosphorescence/Black-Light.
htm
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Fluorescence
An example of fluorescence. Tonic water is clear
under normal light, but vividly fluorescent under
ultraviolet light, due to the presence of the
quinine used as a flavoring.
http//chemistry.about.com/od/imagesclipartstructu
res/ig/Fluorescence---Phosphorescence/Tonic-Water-
Fluorescence.htm
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Fluorescence
Glowing Fluorescent Dye This is an example of a
fluorescent dye, shown under ultraviolet light.
http//chemistry.about.com/od/imagesclipartstructu
res/ig/Fluorescence---Phosphorescence/Glowing-Fluo
rescent-Dye.-07P.htm
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Phosphorescence
Terlingua-type calcite. This blue fluorescence is
actually phosphorescence. The energy of the 254
nm (short wave) UV is believed to be absorbed by
cerium and then photochemically transferred to
europium, which fluoresces blue. Since there is a
visible delay at the start of the fluorescence
(first pink, then blue) and a long lived
phosphorescence, we should call this
phosphorescence instead of fluorescence.
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Phosphorescence
Under a somewhat shorter wavelength of UV (350 nm
peak) the pinkish fluorescence turns to an almost
straw-yellow colour. This is probably caused by
the blue fluorescence/phosphorescence that is
starting to show. Removing the UV-source reveals
a short-lived blue phosphorescence.
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Phosphorescence
This is the typical fluorescence under 366 nm UV.
The activator probably is manganese with some
co-activator, most likely one or more of the rare
earth elements. Photo was taken under a
well-filtered blacklight (true blacklight with
wood-glass mantle).
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Phosphorescence
These photos illustrate phosphorescence. This is
europium doped strontium silicate-aluminate oxide
powder (cyan pigmented), under visible light,
long-wave UV light, and in darkness. In
phosphorescence, energy is absorbed and then
slowly released in the form of light. The slower
time scale of the re-emission (as compared with
fluorescence) is associated with "forbidden"
energy state transitions. The light from
phosphorescence may be released up to several
hours after the exposure to the initial
radiation.
http//chemistry.about.com/od/imagesclipartstructu
res/ig/Fluorescence---Phosphorescence/Phosphoresce
nce-Example.htm
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Be careful!
Hannes Grobe This is a collection of fluorescent
minerals, shown under ultraviolet light.
http//chemistry.about.com/od/imagesclipartstructu
res/ig/Fluorescence---Phosphorescence/Fluorescent-
Minerals.htm
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Hannes Grobe This key identifies the fluorescent
minerals. 1. Cerussit (yellow), Baryt xx -
Mibladen, Marokko2. Skapolith (yellow) -
Greenvile, Ontario, Canada3. Hardystonit (blue),
Calcit (rot), Willemit (grün) - Franklin, New
Jersey, USA4. Dolomite - Långban, Filipstad,
Sweden5. Adamin - Ojuela Mine, Mapimi, Mexico6.
Scheelit (blue) - provenance unknown7. Achat
Druse - Utah, USA8. Tremolit - Balmat, New York,
USA9. Esperit (yellow), Willemit (grün) -
Franklin, New Jersey, USA10. Dolomite - Långban,
Filipstad, Schweden11. Fluorite, Calcite -
Urberg, St. Blasien, Schwarzwald
12. Calcite - Capnic, Rumänien13. Ryolith -
provenance unknown14. Dolomite -
Långban/Jakobsberg, Filipstad, Schweden15.
Willemit (green), Calcit (red), Franklinit,
Rhodonit - Franklin, New Jersey, 16. Eukryptit -
Bikita, Zimbabwe17. Calcite - Schwäbische
Alb18. Calcite in Toneisenstein (Septarie) -
Zion National Park, Utah, USA19. Fluorite -
Upper Weirdale, Durham Co., England20. Calcite
green - Jakobsberg, Nordmark, Filipstad,
Sweden21. Calcite, Dolomite - Iglesiente,
Sardinien22. Dripstones - Lykia, Turkey23.
Scheelit (104), roemer24. Aragonite - Agrigenti,
Sizilien25. Benitoit - San Benito, Kalifornien,
USA26. Quartz aus Schneekopfkugel - Thüringer
Wald27. Dolomite with iron ore - Långban,
Filipstad, Schweden28. unknown (yellow, 10)29.
synthetic corundum30. Powellit xx - Indien31.
Hyalit (Glasopal) - Ungarn32. Vlasovit (yellow)
in Eudyalit - Kipawa, Villedieu, Quebec33.
Doppelspat - Creel, Mexico
34. Manganocalcite? - Långban, Filipstad,
Sweden35. Clinohydrit, Hardystonit, Willemit,
Calcit - Franklin, New Jersey, 36. Calcite -
Urberg, St. Blasien, Schwarzwald37. Apatite,
Diopside - USA39. Dolomitgestein - Långban,
Filipstad, Sweden40. Fluorite - Upper Weirdale,
Durham Co., England41. Manganocalcite - Peru42.
Galmei auf Zinkblende in Ganggestein -
Schulenberg, Harz43. blue/yellow - Långban,
Filipstad, Sweden44. Glasopal - provenance
unknown45. Gips x - Klein-Steinbke,
Königslutter, Elm46. Dolomitgangart - Långban,
Filipstad, Sweden47. Chalcedony - provenance
unknown48. Willemite, Calcite - Franklin, New
Yersey, USA
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Internal conversion
Hair removal!
Pulsed light penetrates deep into the hair
follicle where it triggers a photothermal
reaction that heats up the follicle. 
At the same time, heat travels down through the
skin to help raise the temperature inside the
hair follicle, results in its destruction.
http//www.csomethingnice.com/light_heat.html
The result is long-term removal of hair.
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Internal conversion
Photo-thermal switching of chemical properties.
On-off switching of intramolecular hydrogen bond
by photo-thermal isomerization cycle provides a
new approach for the active controlling of
chemical properties of functional molecules.
http//www.rsc.org/ejga/OB/2006/OB004007.jpg
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Internal Conversion
Photothermal therapy for cancer treatment
an in vitro demonstration of gold nanorods as
novel contrast agents for both molecular imaging
and photothermal cancer therapy.
As a result of the strongly scattered red light
from gold nanorods in dark field, observed using
a laboratory microscope, the malignant cells are
clearly visualized and diagnosed from the
nonmalignant cells. It is found that, after
exposure to continuous red laser at 800 nm,
malignant cells require about half the laser
energy to be photothermally destroyed than the
nonmalignant cells. Thus, both efficient cancer
cell diagnostics and selective photothermal
therapy are realized at the same time.
http//pubs.acs.org/cgi-bin/abstract.cgi/jacsat/20
06/128/i06/abs/ja057254a.html
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PDT application of ISC
The photosensitizer (PS) absorbs light and an
electron moves to the first short-lived excited
singlet state. This is followed by intersystem
crossing, in which the excited electron changes
its spin and produces a longer-lived triplet
state. The PS triplet transfers energy to
ground-state triplet oxygen, which produces
reactive singlet oxygen (1O2). 1O2 can directly
kill tumour cells by the induction of necrosis
and/or apoptosis, can cause destruction of tumour
vasculature and produces an acute inflammatory
response that attracts leukocytes such as
dendritic cells and neutrophils.
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http//www.uni-duesseldorf.de/home/Jahrbuch/2003/M
arian
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Tune in next time for more photochemistry!!!