Dear Oleg,

Please give us infos about :

-protocols about the isolation of your DNA and purification

-the kind of DNA (source),

-about the spectrometer used for UV-Vis(Supplier/single beam , double beam , arrays..) and your buffer or solvent used and your cuvettes (e.g. quartz, PST ..).

-The cutoff of solvent and cuvettes is important and needed for a correct answer.

Please note that the E-Value must be between 0-1.0 and give infos about the concentration.

JRG

Dear Jean,

I can't give you the full protocol of the isolation. But one method was based on phenol-chloroform extraction while the second was realized without phenol.

The source of DNA was yeasts.

The spectrometer is Ultrospec 7000 (GE).

The solvent was the solution of 0,1M NaCl 0,01MTris 0,001M EDTA pH8,0.

Cuvvettes were quartz, 10mm.

upd Thank You, Jean for the reminding about valid range of absorption (0-1,0). I've forgotten about it.

Dear Oleg,

I thank you for the fast answer to my questions. According to your answer, it seems that you use the old Marmur protokol with "phenol" (see papers for the mixture) . I send you the cover and Marmur-references of an old book about DNA isolation and purification.

When you don´t send any infos about the second extraction, I cannot help you with a answer.

I send you a copy of the instructions (free of charge via Thermo Scientific) for the Yeast DNA extraction Kit.

Please , if avaible for you , isolate the Yeast DNA by using the Thermo scientific protocol and test it via UV-Vis and compare the spectrum with the 2 samples .

Concerning your sentence : What do you think about that?

It seems that you isolated impure e.g. contaminated samples (Ratio over 1,8 black spectrum).

I send you a paper about the interpretation of nucleic acid 260/280 ratios (from Thermo Scientific).

Good luck

JRG