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Why does denatured DNA absorb more ultraviolet light than double-stranded DNA?

The phenomenon of UV absorbance increasing as DNA is denatured is known as the hyperchromic shift. The purine and pyrimidine bases in DNA strongly absorb ultraviolet light. Double-stranded DNA absorbs less strongly than denatured DNA due to the stacking interactions between the bases. Single deoxynucleotides absorb more strongly than denatured DNA(1).

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Article References

  1. Alexander, R.R. and Griffiths, J.M. (1993) Basic Biochemical Methods, 2nd Edition. J.M. Wiley and Sons, New York.

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