Fluorescent protein marker · BEGINNER LESSON
GFP
Green fluorescent protein (GFP) is a fluorescent protein used as a marker in living cells and organisms. It is measured by the light it absorbs and the green light it emits, which allows researchers to see where a tagged molecule is located.
What GFP is and what is measured
Green fluorescent protein, or GFP, is a protein that naturally fluoresces. Fluorescence means a material absorbs light at one wavelength and emits light at a longer wavelength. In practice, GFP is measured by its absorption peaks and its emitted green light. The supplied sources describe absorption near 395 nm and 480 nm, with emission near 508 nm. GFP does not need an added substrate or cofactor to glow, which is one reason it became useful in biology. Source evidence also notes that the protein is about 27 kilodaltons, a unit of molecular mass, and that it was first isolated from the jellyfish Aequorea victoria. [1]
[2] Marine-derived Pseudomonas gessardii E2 strain: a novel source of ...
How GFP is used
Researchers fuse the GFP sequence to another protein, making a GFP fusion protein. When the fusion protein is made inside a living cell, the GFP part fluoresces, so the location of the tagged protein can be tracked without killing the cell. This made GFP a major tool for studying gene expression, protein localization, and cell processes in living organisms. The sources also say GFP can be used in microscopy, biosensors, and biomarker work. [0,1]
[1] The fluorescence‐activating and absorption‐shifting tag ... [2] Marine-derived Pseudomonas gessardii E2 strain: a novel source of ...
Mechanism and structure
The fluorescence comes from a chromophore, the light-absorbing and light-emitting part of the protein. The sources describe this chromophore as formed from specific amino acids and protected inside a beta-barrel protein structure, which helps keep it from being quenched by water. One source also notes that GFP fluorescence depends on molecular oxygen, meaning oxygen is needed for the fluorescent state to develop. [1,0]
[2] Marine-derived Pseudomonas gessardii E2 strain: a novel source of ... [1] The fluorescence‐activating and absorption‐shifting tag ...
Limitations
GFP is powerful, but it is not perfect. The supplied sources report that its fluorescence can be reduced by low oxygen, photobleaching from prolonged excitation light, pH sensitivity in many variants, maturation delay after protein synthesis, and loss of signal after fixation. Because GFP is a relatively large tag, attaching it to another protein can also change that protein’s behavior or location. [0,1]
[1] The fluorescence‐activating and absorption‐shifting tag ... [2] Marine-derived Pseudomonas gessardii E2 strain: a novel source of ...
SEE THE IDEA
How GFP helps researchers see proteins
A target protein is linked to GFP so the target can be followed.
The living cell produces the GFP fusion protein.
Light is used to excite GFP so it can fluoresce.
Emitted light shows where the tagged protein is in the cell.
A fusion tag turns protein location into visible green fluorescence under the right illumination.
GFP itself is not the target; it is the fluorescent reporter attached to a target protein.
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Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.