Blue light excites natural GFP to emit green fluorescence. The correct answer is (A) Blue. This property makes GFP a vital tool in molecular biology for visualizing proteins in living cells.

Option Analysis

Natural Green Fluorescent Protein (GFP), derived from the jellyfish Aequorea victoria, contains a chromophore formed by amino acids Ser65-Tyr66-Gly67 that undergoes cyclization and oxidation. This chromophore absorbs light at two main peaks: ~395 nm (UV-violet) and ~475 nm (blue), with optimal excitation around 488 nm blue light, leading to green emission at ~509 nm.​

• (A) Blue: Correct. Blue light (~475-488 nm) matches the major excitation peak of wild-type GFP, promoting the neutral chromophore to an excited state that relaxes to emit green fluorescence.​

• (B) Green: Incorrect. Green light (~509 nm) aligns with GFP’s emission wavelength, not excitation; it cannot energize the chromophore effectively.​

• (C) Infrared: Incorrect. Infrared wavelengths (>700 nm) are too low-energy to excite the GFP chromophore, which requires visible or near-UV light.​

• (D) Red: Incorrect. Red light (~600 nm) falls outside GFP’s absorption spectrum; some GFP variants photoactivate to red states with blue light, but natural GFP emits green when excited by blue.​

Natural GFP, a revolutionary biomarker from jellyfish, relies on specific light wavelengths for fluorescence. Which color of light excites natural GFP to emit green fluorescence? Blue light provides the energy needed for its chromophore to glow green, powering applications in gene expression tracking and live-cell imaging.​

GFP Excitation Mechanism

The GFP chromophore absorbs blue light at 475-488 nm, exciting electrons to a higher state before they release energy as 509 nm green photons. UV-violet light (395 nm) also works but less efficiently in standard setups. This Stokes shift—longer emission wavelength than excitation—prevents overlap and enables clear detection.​

Why Not Other Colors?

Green light matches emission, causing no excitation. Infrared lacks sufficient energy, while red suits far-red proteins, not natural GFP. Engineered variants like EGFP optimize blue excitation for brighter signals.​

Applications in Life Sciences

GFP’s blue-to-green fluorescence tags proteins for microscopy, aiding CSIR NET topics like molecular biology and biotechnology. It revolutionized studies in genetics, cell signaling, and plant engineering without cell harm.​