1 Fluorescence, Fluorescent microscopy and probes Nico Stuurman UCSF Microscopy Boot Camp 2009 Fluorescence in live cells What is it? Sir John Frederick William Herschel, 1854: Though perfectly transparent and colorless when held between the eye and the light, or a white object, it yet exhibits in certain aspects, and under certain incidences of the light, an extremely vivid and beautiful celestial blue colour, which, from the circumstances of its occurrence, would seem to originate in those strata which the light first penetrates the liquid….. Fluorescence 0 1 2 S 0 S 1 S 2 hν A hν A Internal conversion hν E Fluorescence Spin conversion Intersystem Crossing T 1 Phosphorescence hν P Jablonski diagram
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Fluorescence, Fluorescentmicroscopy and probes
Nico StuurmanUCSF Microscopy Boot Camp 2009
Fluorescence in live cells
What is it?
Sir John Frederick William Herschel, 1854: Though perfectlytransparent and colorless when held between the eye and the light,or a white object, it yet exhibits in certain aspects, and under certainincidences of the light, an extremely vivid and beautiful celestial bluecolour, which, from the circumstances of its occurrence, would seemto originate in those strata which the light first penetrates theliquid…..
Fluorescence
012S0
S1
S2
hνA hνA
Internalconversion
hνE
Fluorescence
Spin conversionIntersystem Crossing
T1
Phosphorescence
hνP
Jablonski diagram
2
Stokes shift
Stokes shift
A matter of time
012
Internalconversion
10-12s (300µm)S1
S2
S0
hνA hνA
10-15s (300nm)
hνE
10-8s (3m)QE: ratio ofabsorbed and
emitted photons
Brightness: determined byabsorption coefficient and QE
Absorption coefficient:frequency of
absorption of photons
Othermolecules
Non-radiativedecay
Saturation
012
S1
S0
hνA hνE
Multi-photon excitation
012
S1
S0
hνA
Internalconversion
hνEhνA
hνA
Brad Amos, MRC, Cambridge
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Polarization/Anisotropy
Shinya Inoué
Why use Fluorescence probes?
• Sensitivity• Specificity• Analysis of location and quantity of a single
component in a complex mixture• Detection of small quantities of fluorophores
and fluorescent objects below the resolutionlimit
• Environmental sensitivity• Does not rely on physical properties of the
specimen for contrast generation
Light Source
Excitation filter
Dichroic mirror
Emission filter
3
1
2
1
•Mercury arc lamp•Xenon arc lamp
•Metal Halide doped Hg-Xe Arc
•LASERs (most often used for confocal, TIRF)
Commonly Used Light Sources forFluorescence Microscopy
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Light Sources: Mercury & Xenon Arc Lamps Metal Halide doped Hg-Xe Arc•Halogens decrease carbon deposits and slow deterioration of electrodes
•X-cite illuminator uses liquid light guide; minimal heat transfer
UV
Rel
ativ
e O
utpu
t
Wavelength (nm)
Relative Output of X-Cite Metal Halide vs. HBO 100
Laser linesArgon
HeNe Krypton
http://www.repairfaq.org/sam/lasersam.htm
Light Source
Excitation filter
Dichroic mirror
Emission filter
3
1
2
5
Filters
• Need to reject excitation lightcompletely
• Need to be transparent for emitted light• Need to match spectra of dyes• Spectra of dyes: