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  • kgoglin
    Member
    • Dec 2014
    • 17

    Bioanalyzer and qPCR concentrations differ with large libraries

    We have a theory that large libraries, specifically those with fragments trailing off to >2kb, do not quantitate accurately from Bioanalzyer. We think this because qPCR concentrations do not correlate. Has anyone else had this problem? It seems if we are able to remove the "tail", then qPCR matches a bit better with Bioanalzyer.
  • jwfoley
    Senior Member
    • Jun 2009
    • 183

    #2
    Libraries over 2 kb don't tend to work on Illumina sequencers, so do you really care what the concentration of those molecules is?

    Also, are you doing a TaqMan qPCR or SYBR? If it's SYBR, you have to factor in the average molecule size, so you're still dependent on the Bioanalyzer anyway.

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    • nucacidhunter
      Jafar Jabbari
      • Jan 2013
      • 1250

      #3
      Originally posted by kgoglin View Post
      We have a theory that large libraries, specifically those with fragments trailing off to >2kb, do not quantitate accurately from Bioanalzyer. We think this because qPCR concentrations do not correlate. Has anyone else had this problem? It seems if we are able to remove the "tail", then qPCR matches a bit better with Bioanalzyer.
      This depend on qPCR cycle settings. Using standard protocols gives enough time for extension of around up to 900 bp fragments so larger fragments are not amplified by qPCR. Since fragments above this size do not cluster efficiently they can be ignored. For accurate quantification average fragment length from the shortest fragment to 900-950 bp on the bioanalyser can be used to calculate concentration.

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