The Green Fluorescent Protein (GFP) is a 27-kilodalton protein isolated from the jellyfish Aequorea victoria that fluoresces in the green upon illumination with UV light. The cDNA has been cloned and placed into high-level expression vectors optimized for use in organisms ranging from plants to mammalian cells. With the availability of this cDNA, GFP can be introduced easily into virtually any cell type using standard transfection and selection methods, producing a stable cell lineage with maintained GFP expression.
The fusion of GFP with other proteins generates labeled proteins that can be constitutively expressed in situ for long-term studies. These chimeric proteins often maintain normal function when GFP is added to the NH2 or COOH terminus of the fusion partner. Hence, GFP is an ideal tool for labeling cellular proteins to follow their spatial and temporal localization in live-cell preparations.
The primary consideration when selecting a camera to image GFP chimeras in living cells is sensitivity. It is important to choose a low-noise camera that maximizes signal-to-noise ratio. Additionally, to perform precise localization of the labeled structures within the cell, a medium- to high-resolution detector is preferred.