主题：【原创】这是真的吗？Maxipreps concentration＝4163.1ng/ul？！ -- 大鹏翔宇

If this is your first time do this, better do it in a quantitative way. For example, you can measure OD600 to quantify the amount of E coli before extract the plasmid.

This is not quite safe since you may have other plasmid that using the same antibiotic selection. Better do a double digestion to confirm it.

Do not trust the instrument blindly. As a matter of fact, the smaller the sample size, the larger the experimental error it tend to be. Since you are not limited by the sample amount, I would suggest to measure the UV absorption on a regular UV-Vis spectrometer with proper dilution - get absorption at 260-280 nm in between 0.1-0.8 absorbance on most instruments. Don't forget the blank, it is also very important. I would use the same buffer you used to disolve plasmid in the same cuvette to measure blank. Subtract this blank from the spectrum you measured for your plasmid solution.

I did not do molecular cloning for a long time. But 260/280=1.91 is off a little bit for double strand DNA in my memory (It shows the purity of your DNA sample).

Plasmid can adopt perfect super-coil structure, it can be also nicked so that it will adopt open circle or even linear conformation. Different conformation of plasmid has different mobility rate. This is why you need to digest it in order to compare the size.