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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...

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...

What is the optimal size of DNA that you recommend for Nucleofection®?

We routinely use plasmids of 4-7 kb in our laboratories and plasmids up to approximately 20kb should not be a problem. Using plasmids larger than this will most likely result in lower transfection efficiency. Some preliminary results we have also...

How should I purify my DNA for Nucleofection® of neurons?

The quality and the concentration of DNA used for Nucleofection® in general plays a central role for the efficiency of gene transfer. We strongly recommend using endotoxin free prepared DNA. Endotoxin free Kits are available from several...

Is there a difference between, for example, the programs C-20 and C-020?

No, the programs C-20 and C-020 are identical regarding their electrical parameters. The letter minus a two-digit number is the nomenclature of the Nucleofector™ I. Since we have launched the Nucleofector™ II we changed it to a letter minus a three...

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.

I've noticed that duration of the Nucleofection® Program seems to change even when I haven't changed the program I am using. Why?

The duration time of a program is dependent on the number of the program. The duration is also dependent on how long the Nucleofector® System has been turned on as well as the number of Nucleofections you have done in the last couple of...

Why do you recommend 7AAD instead of PI staining for cell determination in mouse macrophages?

The results obtained using 7AAD staining are much clearer than those obtained using propidium iodide (PI).  Using flow cytrometry stained and unstained, transfected and non-transfected populations can be separated much more easily.

What is the lowest amount of DNA which can be used for transfection? Do I need a DNA carrier for low DNA amounts?

The recommended amount of DNA per 100 µl reaction is 0.5µg-5 µg. No carrier is needed.

How long have you been able to observe GFP expression in primary Human Keratinocytes?

GFP expression has been observed for up to one week as measured by light and fluorescence microscopy.
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