Complex sentence: The intact GFP protein (and its variants CFP, YFP, BFP, and RFP) is fluorescent, however, when the fluorescent protein is split into N and C-terminal halves, the molecule does not produce fluorescence.
Split into simpler sentences: The intact GFP protein (and its variants CFP, YFP, BFP, and RFP) is fluorescent. However, when the fluorescent protein is split into N and C-terminal halves, the molecule does not produce fluorescence.