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Name: sheelta
Status: student
Grade: other
Location: Outside U.S.
Country: Fiji
Date: Spring 2013


Question:
DNA usually has a uv absorption at 260/280nm. Explain this property of UV absorption based on DNA structure. Why does DNA absorb UV light?



Replies:
Hi Sheelta,

Thanks for the question. DNA contains adenine, thymine, guanine, and cytosine, or the A, T, G, and C base pairs. These base pairs contain double bonds as part of what we call an aromatic system. The double bonds absorb UV light which causes the electrons to go from a low energy molecular orbital to a higher energy molecular orbital.

I hope this helps. Please let me know if you have more questions. Thanks Jeff



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