3D NOESY-TOCSY NMR Experiment
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Experiment offers significant clarification of spectral regions that are crowded in the [[2D NOESY]] and [[2D TOCSY]] spectra. For example 3D NOESY-TOCSY experiment allowed nearly complete assignment of proton chemical shifts in 31-mer DNA triplex <cite>patel92</cite> (including H3',H4' and H5' and H5<nowiki>''</nowiki> protons which are difficult to assign using 2D spectra). Authors used ω<sub>3</sub> = const 2D planes for analysis because ω<sub>3</sub> dimension offers the best chemical shift resolution and therefore those planes are the least crowded. Recording time was ~150 hours on a Bruker [[AMX 500]] instrument ( 256x66x128 complex points in t3,t2,t1 with 16 scans) using 4 mM sample. | Experiment offers significant clarification of spectral regions that are crowded in the [[2D NOESY]] and [[2D TOCSY]] spectra. For example 3D NOESY-TOCSY experiment allowed nearly complete assignment of proton chemical shifts in 31-mer DNA triplex <cite>patel92</cite> (including H3',H4' and H5' and H5<nowiki>''</nowiki> protons which are difficult to assign using 2D spectra). Authors used ω<sub>3</sub> = const 2D planes for analysis because ω<sub>3</sub> dimension offers the best chemical shift resolution and therefore those planes are the least crowded. Recording time was ~150 hours on a Bruker [[AMX 500]] instrument ( 256x66x128 complex points in t3,t2,t1 with 16 scans) using 4 mM sample. | ||
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disp: 4@a 5@b 7@c 5@d 11@e 8@g | disp: 4@a 5@b 7@c 5@d 11@e 8@g | ||
Current revision
Homonuclear 3D NOESY-TOCSY experiment was introduced by Vuister et. al [1] in 1988.
Magnetization from protons excited by the first 90o pulse evolves during incremented delay τ1 then, during τm is transferred to the nearby protons by cross-relaxation. Magnetization that arose due to the cross-relaxation then evolves during incremented τ2 delay, then undergoes homonuclear Hartmann-Hahn mixing and then is recorded during the acquisition delay τ3.
A peak observed at (ω1,ω2,ω3) = (ωa,ωb,ωc) with all three values being different will correspond to a proton A close in space to proton B which in turn belongs to the same spin system as proton C. The magnetization follows the path ωa -- NOE --> ωb -- TOCSY --> ωc.
ωa = ωb diagonal plane will contain TOCSY spectrum, ωb = ωc - NOESY spectrum, and ωa = ωc plane will contain so-called back-transfer spectrum where magnetization is first transferred from proton A to proton B by NOE and then back to the origin proton A by Hartmann-Hahn mechanism.
Experiment offers significant clarification of spectral regions that are crowded in the 2D NOESY and 2D TOCSY spectra. For example 3D NOESY-TOCSY experiment allowed nearly complete assignment of proton chemical shifts in 31-mer DNA triplex [2] (including H3',H4' and H5' and H5'' protons which are difficult to assign using 2D spectra). Authors used ω3 = const 2D planes for analysis because ω3 dimension offers the best chemical shift resolution and therefore those planes are the least crowded. Recording time was ~150 hours on a Bruker AMX 500 instrument ( 256x66x128 complex points in t3,t2,t1 with 16 scans) using 4 mM sample.
References
- Vuister, GW and Boelens, R and Kaptein, R. Nonselective three-dimensional NMR spectroscopy. The 3D NOE-HOHAHA experiment. J Magn Reson 80:176--185, 1988. BibTeX
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Radhakrishnan, I and Patel, DJ and Gao, X. Three-dimensional homonuclear NOESY-TOCSY of an intramolecular pyrimidine. purine. pyrimidine DNA triplex containing a central G. TA triple: nonexchangeable proton assignments and structural implications.. Biochemistry 31(9):2514--23, 1992. BibTeX
Implementations
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