If it is true then please explain why there is a difference in the absorption peaks of DNA (@260nm) & RNA? Considering the fact that DNA & RNA differ only in terms of an extra oxygen atom (present in sugar of RNA) and an extra methyl present on a nitrogen base of DNA (T v/s U);
And both these atoms (oxygen) and groups (methyl) do not have any aromatic rings and hence they cannot be considered involved in absorbing UV radiation which rules out any possibility of difference in absorption peaks of DNA & RNA.
Kindly share your views on this. Thank you !!! :)
For RNA in aqueous solution or most buffered aqueous solutions the absorbance spectrum is very similar to DNA with a major peak at 260nm and no major peak at 230nm. 260/280 ratio is very slightly higher if anything in RNA - typically not below 2.0 for pure preparations. Also typically RNA preparations are only partially double stranded and for this reason extinction coefficient at 260nm is higher than for double stranded DNA preparations, approaching that of single stranded DNA. For RNA a rough conversion is that 40ug/ml has an OD of 1 at 260nm.
For RNA in aqueous solution or most buffered aqueous solutions the absorbance spectrum is very similar to DNA with a major peak at 260nm and no major peak at 230nm. 260/280 ratio is very slightly higher if anything in RNA - typically not below 2.0 for pure preparations. Also typically RNA preparations are only partially double stranded and for this reason extinction coefficient at 260nm is higher than for double stranded DNA preparations, approaching that of single stranded DNA. For RNA a rough conversion is that 40ug/ml has an OD of 1 at 260nm.
RNA does not absorb at 230nm. Absorption at 230nm can be caused by contamination with some organic compounds. For a pure RNA sample, the A230:260:280 should be around 1:2:1.
I hope it helps!
- Badges
- Science method
- Similar topics
- Methodology
- Absorption Spectroscopy