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

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?

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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