Spectrophotometric estimation of RNA

Anton Scott Goustin asg at cmb.biosci.wayne.edu
Mon Mar 11 19:07:12 EST 1996


srinum at iastate.edu (SRINIVAS MUMMIDI) wrote:
>Hello,
>	I am trying to estimate the concentration of double-stranded RNA
>spectrophotometrically.  Is 1 A260 unit of double stranded RNA is equal
>to 50 micrograms per ml as in case of DNA? Any pointers will be very
>helpful. Thank you very much in advance.
>
No, like single-stranded DNA, RNA absorbs more per mole than double-
stranded DNA.  The lack of base-stacking leads to a so-called hyper-
chromic effect, increasing the A260 per mol.  Thus, 1 OD260 of single-
stranded DNA is less moles of DNA than 1 OD260 of dsDNA.  The rule for
ssDNA is the same as RNA:  1 OD260 will result if you dissolve 40 µg
of ssDNA or RNA in 1 mL and measure with a pathlength of 1 cm.
Some authors use 1 OD260 = 37 µg of RNA.  I am not sure which is
correct.





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