weird thing in Maxiprep - (Jan/04/2006 )
After maxiprep, DNA concentration is 200ng/ul in 2500ul water, 206/280 ratio is 1.9.
Then I use Sodium actetate/ethonal to preciptate the DNA and washed once with 70% ethonal, then diluted in 250ul water, found the 260/280 ratio is only 1.4 although DNA concentration is higher (1.1ug/ul) What's wrong with the preciptation? why 260/280 ratio becamce so low?
i'm not 100%sure but when concentration is increased,the ratio tendstodecrease little. When i have conc like yours, i use to heat DNA at 50° for few min (5 to 10) and measure the OD. Ratio is more accurate.
I heated the DNA for half an hour. The OD is still very low.