An Introduction to Fluorescent Proteins
EoSFP: Green to Red In A Flash
Fluorescent proteins are members of a structurally homologous class of proteins that are able to fluoresce when exposed to particular wavelengths of light. These proteins accomplish this through the formation of a chromophore with three amino acids within the structure of the protein.
What is a Fluorescent Protein?
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Photoactivatable / Photoconvertible: Proteins is this category of classification are able to change their emission fluorescence or begin fluorescing when excited by a particular wavelength of light.
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Fluorescent Timers (FT): Proteins in this category are able to change their fluorescence after being activated over a period of time.
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Large Stokes Shift (LSS): Proteins in this category have large shifts from excitation to emission (greater than or equal to 100 nm). Most fluorescent proteins have a shift much less than this of about 50nm
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Fluorescent Sensors: These proteins change their fluorescence in response to changes in environmental conditions.
Fig. 1 - Color Emission Categorization
The first fluorescent protein was isolated from Aequorea victoria jellyfish by Osamu Shimomura and Frank Johnson in 1961. They named this protein aequorin. While isolating aequorin, which emits a blue fluorescence, another protein was discovered that instead emitted a green fluorescence. It was this protein that was given the name green fluorescent protein (GFP). These calcium induced fluorescent proteins have since been used in research, along with other fluorescent proteins that have since been discovered, to track expression levels in systems and visualize localizations of different fusion proteins. In addition, fluorescent proteins have been used for biosensors, study interactions of proteins within cells, study promoter activity, etc.
Fluorescent proteins are categorized by emission color (Fig. 1) and other properties as summarized below:
Below is a summary of some fluorescent proteins and their properties. A broader list of fluorescent proteins and their properties can be found at the link provided http://nic.ucsf.edu/FPvisualization/ and at AddGene.com.
What is a Fluorescent Protein?
Categorization by Properties:
