Staining of nucleus in human cell line U-2 OS (HPA043786)
Scale bar represents 10µm
The nucleus is the largest organelle in the human cell and contains almost all the DNA in eukaryotic cells (the rest being found in the mitochondria). It is surrounded by the nuclear membrane, which isolates it from the rest of the cell. This ensures a highly controlled DNA replication and transcription without interference of the translation that takes place in the cytoplasm.
In the Human Protein Atlas the chemical 4',6-diamidino-2-phenylindole (DAPI) is used to counterstain the nucleoplasm, as it will bind strongly to DNA, and hence not stain the nucleoli. The immunofluorescent staining of proteins localized to the nucleus varies between different antibodies, in some cases staining the whole nucleus and in others the nucleoplasm. The staining characteristics can vary from a smooth to a punctate staining.