Plasmids for protein expression in mammalian cells - (Oct/01/2009 )

Hi all
I have constructs for fragments and whole protein.
I use TNT lysate (Promega) to express proteins to test protein interactions.
I've tried different plasimds but the results were not good.
Can someone give me advice or some information about what plasmids are best for protein expression in lysate ( mammalian cells)?
Also what are the features that should be in plasmids to use them for protein expressin?

Thank you in advance

you are doing in vitro transcription/translation right?

Have you thought of using other lysates instead of the promega one that you are using currently?

Yes, I use in vitro transcription/translation system.
In fact we just used Promega products. Sorry, why you suggest using another lysate?