Hyperchromic effect
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The hyperchromic effect is the striking increase in absorbance of DNA caused by the denaturation of the double-stranded DNA molecule. The two strands of DNA are bound together by the hydrogen bonds between the complementary bases. The hydrogen bond limits the resonance of the aromatic ring so the absorbance of the sample is limited as well. When the DNA double helix is treated with denatured agents, the interaction force holding the double helical structure is disrupted. The double helix then separates into two single strands which are in the random coiled conformation. At this time, the base-base interaction will be reduced, increasing the UV absorbance of DNA solution because many bases are in free form and do not form hydrogen bonds with complementary bases. As a result, the absorbance for single-stranded DNA will be 40% higher than that for double stranded DNA at the same concentration.
