You have purified 50 ul of recombinant plasmid DNA from a sm

You have purified 50 ul of recombinant plasmid DNA from a small culture of bacterial cells. You measure the absorbance of the sample using a spectrophotometer set at 260nm and 280 nm and obtain the following readings: A260=0.466 and A280=0.389

a. What is the DNA concentration of the plasmid DNA in your purified sample. Show your work throughout (including units). Hint. The conversation factor for double-stranded DNA is 1.0 OD260= 50 ug dsDNA/ ml

b. How much total DNA was purified by this procedure? Show your work.

c. What is the A260/A280 ratio of the DNA sample and what does this tell you about your preparation?

Solution

A) if the 50 ug dsDNA gives a O.D of 1

Then the DNA of absorbance 0.466 will give the concentration equal to

0.466*50=23.3 ug dsDNA /ml..

C) this ratio gives or tells us the purity of DNA and RNA sample which is obtained.. The impurities which can be present is Proteins..

If the value of the ratio comes approximately equal to 1.8 then we can say it is a pure DNA sample.. For RNA the value is approximately equal to 2 for it to be a pure RNA sample..

So in this experiment the ratio comes to equal to 1.197. This state that the DNA which is obtained contains impurities as protein in them..!!