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+and - in plasmid names - (Oct/09/2007 )

Hi, I am working with a plasmid whose name is pET-29b+. I wonder what the + stands for? can anyone enlighten me?


Generally + and - are used to indicate the orientation of the plasmids' MCS. Say if in +, MCS is EcoRI-BamHI-PstI then in - it would be reversed (PstI-BamHI-EcoRI). But still confirm if the same holds true for your plasmid.


From the pET system manual (see here, for example):

"Note that the (+) following the name indicates that the vector contains an f1 origin of replication that allows the production of single stranded plasmid DNA for mutagenesis and sequencing applications."