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Old 03-04-2015, 02:04 PM   #14
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Location: Bioo Scientific, Austin, TX, USA

Join Date: Jun 2012
Posts: 119

I have noticed something similar when quantifying gDNA by Nanodrop. What I saw was values that would vary quite a bit when reading different "drops" from the same tube of gDNA. This was solved by vortexing the DNA for 10 seconds. The idea is that the genomic DNA molecules are so large that one microliter might have varying amount of these large DNA molecules. Following vortexing the gDNA is in much smaller fragments, which allows it to exist more evenly in solution such that every microliter will have a much more similar amount of DNA. Think of it of grabbing handfuls of sand versus handfuls of medium sized rocks and weighing them. The handful of sand will be very close to the same weight each time, but the rocks will vary much more. I haven't tested the theory about large DNA vs sheared DNA, but we have tested vortexing DNA for 10 seconds prior to reading on the Nanodrop and it definitely results in much more consistent readings.
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