Question

Which one of the following is the peak absorption range of ultraviolet light by heterocyclic bases (nitrogen bases)?
A. $1500$ nm
B. $26$ nm
C. $75$ nm
D. $260$ nm

Answer 1

Most absorption of nucleic acids is due to heterocyclic nitrogen base rings. DNA and RNA, the sample is exposed to ultraviolet light at wavelength, and the photodetector measures the light that passes through the sample.

Complete answer:
-Heterocyclic bases (Nitrogenous bases) of DNA or RNA absorb maximum at $260$nm in the UV spectrum. The most absorption at $260$nm through nucleic acids is because of the heterocyclic rings of nitrogenous bases.
-Spectrophotometric evaluation is primarily based totally on the concept that nucleic acids soak up ultraviolet light in a particular pattern. In the case of DNA and RNA, a sample is exposed to ultraviolet light at a wavelength of $260$ nanometres (nm) and a photodetector measures the light that passes via the sample.
-Some of the ultraviolet light will by skip via and a few, might be absorbed with the aid of using the DNA/RNA. The greater light absorbed through the sample, the better the nucleic acid concentration withinside the sample. The ensuing impact is that much less light will strike the photodetector and this can produce a better optical density (OD).
So, the correct answer is (D) '$260$ nm'.

Note: UV spectra of bases display most from $259$ to $274$ nm. The sugar-phosphate spine is taken into consideration as the maximum vital for conformational modifications in double-stranded DNA (A and B forms). Backbone PO2 stretching bands may be observed only using FT-IR spectroscopy. These are visible from at $836$ - 860$$$$cm^{−1}, respectively. A comparison of the incorporated absorptions of those bands A$836$/(A$836$+A$860$) may be used for quantitative estimations of B-A forms.