Sandbox 206: Difference between revisions
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The residues surrounding the Venus chromophore are similar to those surrounding the chromophore of EYFP. Electron density studies of Venus show an 11° angle between the planes of the chromophore and Tyr203, while the same angle measured in EYFP is 11.5–12.3°, making the plane of the Venus chromophore slightly more parallel than that of EYFP. | The residues surrounding the Venus chromophore are similar to those surrounding the chromophore of EYFP. Electron density studies of Venus show an 11° angle between the planes of the chromophore and Tyr203, while the same angle measured in EYFP is 11.5–12.3°, making the plane of the Venus chromophore slightly more parallel than that of EYFP. | ||
[[Image:Chromophore1MYW.gif | | [[Image:Chromophore1MYW.gif |340px|left|thumb|Chromophore of Venus]] | ||
This small difference may account for a minor change in the absorption spectrum of Venus rela- tive to EYFP, as seen at a pH range of 4.6–8.6 and a 50 mM NaCl concentration. Although the position of the main absorp- tion maximum remains unchanged (516 nm) in both Venus and EYFP, a smaller peak resulting from the neutral (protonated) chromophore is shifted in Venus by 20 nm producing a peak at 413 nm versus 393 nm in EYFP. The slightly more parallel orientation of the aromatic rings of Tyr66 and Tyr203 might also help improve the π-π interaction, thus reducing the excited state energy of the neutral chromophore. If this is the case, we can hypothesize that at lower pH, which is favorable to chro- mophore protonation, the angle between the rings would be smaller than 11°. | This small difference may account for a minor change in the absorption spectrum of Venus rela- tive to EYFP, as seen at a pH range of 4.6–8.6 and a 50 mM NaCl concentration. Although the position of the main absorp- tion maximum remains unchanged (516 nm) in both Venus and EYFP, a smaller peak resulting from the neutral (protonated) chromophore is shifted in Venus by 20 nm producing a peak at 413 nm versus 393 nm in EYFP. The slightly more parallel orientation of the aromatic rings of Tyr66 and Tyr203 might also help improve the π-π interaction, thus reducing the excited state energy of the neutral chromophore. If this is the case, we can hypothesize that at lower pH, which is favorable to chro- mophore protonation, the angle between the rings would be smaller than 11°. | ||
