rhodopsin - University of Michiganchem260/fall01/lecture15.pdf · Jablonski diagram If colliding...
Transcript of rhodopsin - University of Michiganchem260/fall01/lecture15.pdf · Jablonski diagram If colliding...
Nils Walter: Chem 260
Vision
2
22
8mLhnEn =
ππππ-to-ππππ*
rhodopsin
Nils Walter: Chem 260
FluorescenceJablonski diagram
If collidingmolecules cannotaccept this larger
energy
nsecfsec
Excitedelectronic state
Groundelectronic state
Vibrational states
Vibrational states
Dissipation inenvironment asheat = internal
conversion
Nils Walter: Chem 260
fsec
internalconversion
Fluorescence quenchingM + hνννν1 →→→→ M*
→→→→ M + hνννν2(fluorescence, kf)→→→→ M + heat (internal conversion, ki)
+ Q →→→→ M + Q*→→→→ M + Q + heat (quenching, kQ)
Molecular species(e.g., H2O, I-) with
suitable energygaps can take up
this energy���� quenching
of fluorescence
][1 Qkkk Qif ++=τkf + ki
Nils Walter: Chem 260
Green: Donor fluorophoreRed: Acceptor fluorophore
����
The molecular dynamics of asingle biomolecule can be
observed by modernfluorescence techniques
Fluorescence quenching:An example from actual research
601��
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�=rRk
DT τRate of energy transfer
60
6
60
RrREET +
=
Efficiency
Nils Walter: Chem 260
Phosphorescence
min, hoursfsec
Triplet→→→→Singlet state transitionis NOT allowed ���� takes long
radiationless
Nils Walter: Chem 260
Lasers: Light Amplification byStimulated Emission of Radiation
Populationinversion
equilibrium population
laser effect
inverted population pumping