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visible light damage to DNA



Following is a response from one of our researchers who investigates
mutation mechanisms.  Neat stuff!

Andy

-----Original Message-----

Peak and Peak (I forgot their first names) showed that near UV caused some 
damage (300-~400 nm).  Since DNA absorption tails off around 300 nm this 
came as a surprise.  At longer wavelengths, the visible light, I don't 
think any photochemistry occurs via direct interaction with DNA unless you 
go to high intensity sources (lasers) where multiphoton processes kick 
in.  Visible light can damage DNA indirectly via a chromophore that absorbs 
visible light and subsequently passing on the excitation to O2 (singlet 
oxygen) which then can react with DNA (albeit very slowly).  The latter is 
the basis for photodynamic therapy.


Andrew Karam, CHP              (716) 275-1473 (voice)
Radiation Safety Officer          (716) 275-3781 (office)
University of Rochester           (716) 256-0365 (fax)
601 Elmwood Ave. Box HPH   Rochester, NY  14642

Andrew_Karam@URMC.Rochester.edu
http://Intranet.urmc.rochester.edu/RadiationSafety
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