Does anyone regularly measure the 260/280 for their oligos and what kind of numbers do you get?
RESPONSE:1. We used to measure 260/280 routinely, but rarely bother now for a couple of reasons. First, the A260 value for oligos depends very much on the base composition since the extinction coefficients for G and A are much higher than those for T and C. We found that we got 260/280 ratios ranging from1.4 to 2.2 even on highly purified oligos, so the ratio was not a very good measure of purity without going through the calculations for each oligo. On long DNA strands the purines and pyrimidines tend to average out, so one can expect a more stable average of 1.8. 2. We do not measure such ratios. My feeling is that they are not very useful unless the DNA is REALLY filthy. See the following reference: Glasel, J.A. (1994);Validity of nucleic acid purities monitored by 260nm/280nm absorbance ratios. BioTechniques. 18(1): p. 62-63.
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