What was the concentration of pUC19 DNA calculated from the

What was the concentration of pUC19 DNA calculated from the OD260 reading and how much total plasmid DNA did you purify from the culture? Give the reading, show your calculations and what was the OD260/280 ratio? OD260=0.017 OD260/A280 = 1.39 Diluted 5 uL of plasmid DNA to total volume of 100 uL. I am unsure of the volume I resuspended the DNA into (if that makes a difference - would i need to know this?). Thank you! (can you please show work and units?)

Solution

Since we diluted 5 ul of plasmid to 100 ul , the dilution factor becomes 100 / 5 = 20

the total plasmid that we purified would be given by the formula :

100 ug/ml x OD260 X dilution factor.

100 ug/ml x 0.017 x 20 = 34 mg /ml

the OD260/280 ratio shows the purity of the purified DNA. pure DNA has the ratio of approximately 1.8 and pure RNA has a ratio of approximately 2.0 . low ratios could be due to mixing of protein and phenol.

since the OD260/280 ratio was 1.39, it could indicate protein or phenol contamination,

therefore the total plasmid that was purified was 34 mg/ml.