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All around the net you will find this list giving 260/280 ratios of individual nucleotides:

Guanine: 1.15 Adenine: 4.50 Cytosine: 1.51 Uracil: 4.00 Thymine: 1.47

Yet I cannot find a reliable source for these values. One source cites a 70s version of Leninger's Biochemistry but even though I got hold of a more recent edition, I cannot find that information in there.

Does anyone happen to know a quotable source for this?

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I too was unable to find the data in the 3rd Edition of Lehninger's Biochemistry.

A good source of such information usually is

Data for Biochemical Research, by Rex M. C Dawson, Daphne C. Elliott, William H. Elliott and Kenneth M. Jones (3rd Edition, 1986, Clarendon Press Oxford).

The first thing to note is that the ratios may be significantly pH-dependent, and the source quoted by the OP does not specify what pH the data refer to.

The data in Column 2 below been taken from the above source, from which the data in Column 3 were calculated.

(pH 7)-------------A280/A260--A260 /A280

Adenine             0.13        ~ 7.7                              
Cytosine            0.58        ~ 1.7
Guanine             1.04        ~ 0.96
Uracil              0.17        ~ 5.9
Thymine             0.53        ~ 1.9   

These data seem to have been substantially taken from an article by K. Burton in the second edition of DFBR.

K. Burton (1969) Spectral Data and pK values for purines, pyrimidines, nucleosides, and nucleotides in Data for Biochemical Research by Rex M. C Dawson, Daphne C. Elliott, William H. Elliott and Kenneth M. Jones (2rd Edition, Clarendon Press Oxford).

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If it's so important to you that you need a quotable source for this, I'd measure it myself with the equipment I use for the real experiment.

Otherwise I'd suggest you look at a chemical database such as NIST: http://webbook.nist.gov/cgi/cbook.cgi?ID=C58617&Mask=400 and use the spectra that can be found there.

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  • $\begingroup$ +1, but I disagree with your first statement. To reliably determine such ratios will require very pure reagents or, at the very least, experimental evidence that the 'pure' nucleotides and the solvent contain no materials that absorb at either 260nm or 280nm. $\endgroup$ – user1136 Oct 27 '16 at 16:41
  • $\begingroup$ @tomd: Yes, to get the "true" values that would be required, and apparently also in the literature they didn't get the same values twice. I'd say if you need them for your own experiments, it might be better to actually measure the purities you have. $\endgroup$ – VonBeche Oct 27 '16 at 19:57

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