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In order to construct a complex plasmid library, synthesis of cDNA and
ligation to the vector must be as efficient as possible. Ultimately, the
final quality of a plasmid cDNA library is determined by transformation
of the ligation products into the E. coli host. The optimal E.
coli host for generating large, complex cDNA libraries was determined
by comparing the primary size of cDNA libraries constructed in the pCMV-Script
and pAD-GAL4 XR predigested vectors and transformed into XL2-Blue,5
XL10-Gold or DH10B*** cells (figure
2). The average number of primary clones obtained from transformation
into XL10-Gold ultracompetent cells was 4.6-fold greater than the number
of primary clones obtained from XL2-Blue cells and 22-fold greater than
obtained from DH10B cells. For the tranformation control, supercoiled
pUC18 was used. The transformation efficiency for XL2-Blue and XL10-Gold
cells was 5 x 109 colony-forming unit (cfu)/g of pUC18 DNA,
and transformation efficiency for DH10B cells was 1 x 109 cfu/g
of pUC18 DNA. When comparing XL2-Blue and DH10B cells, the relative library
size obtained when the pCMV-Script and pAD-GAL4 XR predigested vectors
were used correlates well with the relative efficiencies observed for
supercoiled pUC18 DNA. However, the relative library size obtained from
transformation into XL10-Gold cells was 4.8-fold higher than predicted
by the transformation effic
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