1. What is Fluorescence?

2. http://elchem.kaist.ac.kr/vt/chem-ed/spec/molec/mol-fluo.htm A type of electronic spectroscopy, that is, it involves excitation of electrons—energy absorption to an excited state— followed by emission of a smaller energy as radiation. Fluorescence and Phosphorescence are two types of Luminescence.

3. What is Fluorescence? Link to Simulation spectrometer: http://terpconnect.umd.edu/~toh/models/Fluorescence.html S refers to ‘singlet’ and T to ‘triplet’ states. The S 0 state is the ground state and the subscript numbers, S 1 and S 2, identify individual excited states.

4. What is Fluorescence? Xe lamp Sample cell photodetector Emission monochromator excitation monochromator

5. Why is Fluorescence useful in DNA (and other biochemical) Studies? -Fluorescence generally is much more sensitive to the environment of the chromophore than is light absorption. - Fluorescence is a useful technique for following the binding of ligands or conformational changes. - The sensitivity of fluorescence is a consequence of the relatively long time a molecule stays in an excited singlet state before de-excitation. -Absorption is a process that is over in 10 -15 sec, a time scale where the molecule and its environment are effectively static. -In Fluorescence, during the 10 -9 to 10 -8 sec that a singlet remains excited, all kinds of processes can occur, including protonation or deprotonation reactions, solvent-cage relaxation, local conformational changes, and any processes coupled to translational or rotational motion.

6. What is the connection between Fluorescence and DNA Photocleavage? Ru(bpy) 2 (L) 2+ Ground state {Ru(bpy) 2 (L) 2+ }* Excited state Ru(bpy) 2 (L) 2+ Ground state {Ru(bpy) 2 (L) 2+ }* Excited state + h

7. What is the connection between Fluorescence and DNA Photocleavage? Ru(bpy) 2 (L) 2+ Ground state {Ru(bpy) 2 (L) 2+ }* Excited state MLCT, d e-   * orbital 1 O 2 singlet state, S 3 O 2 triplet state, T “Ru(bpy) 2 (L) 2+ “ Relaxed state O=O “triplet energy transfer"

8. What is the connection between Fluorescence and DNA Photocleavage? Ru(bpy) 2 (L) 2+ Ground state {Ru(bpy) 2 (L) 2+ }* 3O23O2 “Ru(bpy) 2 (L) 2+ “ Relaxed state 1O21O2 + h AT TA CG GC AT CG AT TA CoxG GC AT CG

9. What is the connection between Fluorescence and DNA Photocleavage? Oxidized Guanine bases 3O23O2 1O21O2 AT TA CG GC AT CG AT TA CoxG GC AT CG