![]() Nucleic acids (DNA and RNA) absorb maximally at 260 nm. ![]() These absorbance measures give you an idea of the concentration of your DNA prep and whether there are any other contaminants. Then you measure the absorbance of the DNA sample. This is a “blank” and measures the background absorbance. First you measure the absorbance of the buffer that the DNA is in. The spectrophotometer measures these absorbances using UV-transparent cuvettes. Molecules absorb different wavelengths of light to different degrees and many molecules have a specific wavelength that they maximally absorb. This method involves measuring the absorbance/transmission of light through a liquid to determine the concentration of substances in the liquid. Using UV absorbance is one of the most common ways to quantify DNA. There are many ways to do this and the method you choose could be based on your downstream application, time, and instrument availability. How do you know if you actually have DNA in your tube without seeing it? But in many cases, you won’t see any signs of DNA in your final tube after purification. You’ve prepped your DNA and you’re ready to get started on the next step of your experiment.
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