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Why do plasmids which contain IRES sequences often have lower transfection efficiency?

In general, there is not a problem using IRES plasmids with Nucleofection®, with one important caveat. The levels of expressed protein for the first and second genes will not be identical, and this can create problems with analysis and interpretation...

Do I need a special incubator for cultivation of insect cells ?

Insect cells are cultivated at lower temperatures than E.coli or mammalian cells (S2 cells at 24°C, Sf9 cells at 28°C).Therefore they need a dedicated incubator with appropriate temperature.

When nucleofecting cancer cell lines, do I need to be concerned about passage number?

For the most efficient gene transfer, we recommend using cells that are in logarithmic growth phase and at a passage number of 10-15 (from the time of thaw). This is because some cell lines differentiate and change their features after many...

Which promoter can be recommended for transient gene expression in mammalian cells ?

Vectors with a CMV promoter typically work fine for transient protein expression in mammalian cells, like HEK293, CHO or NSO. For insect cells, like Sf9 or Sf21, vectors with insect promoters are required. In HEK293E (EBNA) cells, the use of...

Why do plasmids that contain LTR sequences often have lower transfection efficiency?

In general, successful Nucleofection® is vector independent, with one important caveat. Some expression plasmids utilize promoters and enhancers obtained from the Long Terminal Repeats (LTR's) of retroviruses, and when these expression plasmids are...

Following Nucleofection®, I cannot obtain stable clones from single cells. What could be the reason?

Some cell lines need certain cell densities to proliferate. For those cells you can try using conditioned medium for setting up limiting dilution or culturing single cells together with feeder cells.

What is the best incubation time for transient gene expression in Nucleofection® Experiments?

The optimal incubation time ranges from 2 to 6 days depending on various factors like the stability of the protein in the medium, potential toxicity of the protein, cell density and stability of the plasmid in the nucleus. To check the timepoint for...

What antibiotic concentration should I use for selecting stable transfectants?

We highly recommend to perform a titration for G418 in a range of 0,1 mg/ml to 1,5 mg/ml; in serum-free culture expand range down to 20 µg/ml).Choose the concentration which is 0,1 or 0,2 mg/ml above the one which shows complete cell death as...

Is it more difficult to detect DsRed by FACS than GFP?

Yes, DsRed is much less bright than GFP and is more difficult to detect by FACS and microscopy because it bleaches quickly.

Why is the Nucleofector® Technology ideal for transient protein production ?

For many cell lines in suspension, especially sCHO, conventional transfection methods are very limited in efficiency. For protein production, suspension cells are favored over adherent cells because they are much easier to cultivate. Unlike...
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