Nanodrop

     Some experimenters may find a need to know the concentration of a certain substance, usually a plasmid (circular DNA). In order to find out how much DNA you have, you could use a spectrophotometer. However, normal spectrophotometers usually use about 1mL of a sample. In most cases, you do not have this much plasmid. In order to measure the concentration using a small amount of plasmid, you can use a nano spectrophotometer, referred to as Nanodrop.
     If you have access to a nanodrop, install the software on your computer, and click on ND1000 to open the software. Select the nucleic acid setting if you are measuring DNA . Make sure DNA-50 is selected in the top right. Wipe both the upper and lower terminals with nanopure to clean the terminals. Then, initialize the instrument with water by placing 2uL of nanopure water on the sample pedestal, lowering the arm, and clicking okay. Then clean the pedestal to remove the water. Next, blank the insturment by placing 2uL of your elution buffer (ex. TE, Tris HCL, etc.) on the pedestal and clicking blank. It is important to blank the instrument using the buffer your DNA is in to account for any background absorbance from the buffer. Then, clean off the pedestal again. Finally, measure your sample by placing 2uL of it on the pedestal and clicking measure. The output is in ng/uL. Record the 260/280 value and the 260/230 value. These ratios will give you the purity of the DNA if you need it. Print out your graph.

     To be more accurate, take a second measurement and average the readings. The concentration of plasmids are usually abbreviated using the symbol λ, which means ug/uL. If your value is 1.5λ, then that is equal to 1.5ug/uL, which is equal to 1500ng/uL.