11i_9c - Lab 11i: Determining the Purity and Concentration...

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Lab 11i: Determining the Purity and Concentration of DNA Samples A UV spectrophotometer can be used to study the concentration and purity of samples of DNA, RNA, and protein. Hence, the purpose of this lab was to approximate the concentration and relative purity of DNA in spinach samples from two different DNA extraction kits Puregene and Qiagen to compare their efficiency. We determine this efficiency by measuring both concentration and purity by collecting readings of each sample at 260 nanometers and 280 nanometers. A good sample would have a purity quantified between 1.5 and 1.8. A number above 1.8 indicates RNA contamination, whereas a number below 1.5 indicates protein contamination. A good sample should also be as concentrated as possible. The absorbance reading at 260 nm of the Qiagen sample was 0.29125 au while the absorbance reading at 280 nm was 0.2125. The concentration of this sample was 14.56 μg/mL. By dividing the absorbance at 280 nm into the absorbance at 260 nm the purity is determined to be 1.37, indicating protein contamination. The absorbance reading of the Puregene sample at 260 nm was 0.293 au and 0.232 au at 280 nm. The concentration was 146.5 μg/mL, however the purity was only 1.26. Despite that the concentrations of each sample is suitable, the purity is lower than optimum for DNA samples (1.5-1.8) suggesting that the samples are highly concentrated with impurities, not DNA. Hence, one can conclude that both samples are contaminated with protein, and that neither
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This note was uploaded on 12/06/2011 for the course ENG 100 taught by Professor Posh during the Summer '11 term at San Mateo Colleges.

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11i_9c - Lab 11i: Determining the Purity and Concentration...

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