The TROSY (Transverse Relaxation-Optimized Spectroscopy) experiment increases the sensitivity and the resolution of heteronuclear ¹H-X correlation inverse experiments by selecting the multiplet component which relaxes most slowly due to cross-correlation between dipole-dipole (DD) and chemical shift anisotropy (CSA) relaxation. Thus, at very high fields strengths, nearly complete cancellation of both mechanism can be achieved and, consequently, spin-spin relaxation rates can be reduced significantly. This effect is particularly attractive in ¹H-¹⁵N amide groups in the backbone of proteins and in the aromatic side chains where the ¹³C nuclei exhibit large CSA. However, cross-correlation between DD(¹H-¹³C) and CSA (¹³C) is less complete than for ¹H-¹⁵N bevasue the ¹³C CSA tensors deviate more pronouncely from axial symmetry than the ¹⁵N CSA tensors in amied groups and because aromatic ¹H spins have much smaller CSA than amide protons.

This approach offers the posibility to extent the aplication of triple-resonance NMR experiments to biomolecules larger than 25-30 kDa.

The TROSY approach has been successfully implemented in many double- and triple-resonance experiments (See TROSY Applications)

Easy implementation on AVANCE spectrometers equipped with pulsed field gradients (PFGs) and inverse probehead.

The original TROSY version is a modification of the regular HSQC pulse train in which the retro-INEPT building block is conveniently modified in order to select the slowest relaxing component ( 97PNAS12366 and B03ZER227).

Improved versions affecting both sensitivity and resolution requirements has been reported that incorporate the PEP methodology ( 98JMR364-133 ), the use of PFGs ( 98JACS10778 , 98JB345 , 98JACS11845 , 98ANG2859 , 99JMR92-136 , 99JB77 , 03MRCS80 and 05JB161-31 )

and the incorporation of the CRINEPT scheme.

Since relaxation rate of antiphase components is faster than that of the in-phase ones, spurious relaxation-induced artifacts can be present in TROSY spectra. Several approaches have been proposed to remove them ( 00JMR417-143 and 00JMR123-144 ).

A variant to detect and suppress conformational exchange induced transverse relaxation in nucleic acids has been reported ( 01JB275 ) and applied to measure through-hydrogen bond coupling constants.

SEA-TROSY element: 1H-15N TROSY experiment to detect solvent exposed amide protons ( 01JACS4633 ). The idea is to use a double 15N filter to eliminate all magnetization generated from amide protons. The water magnetization is then returned to the z axis to exchange with amide protons during a mixing time. Resultant mangnetization is then observed using a TROSY block. This block can be inserted in any TROSY-base and also HSQC (Clean SEA-HSQC - 02JB317 ) experiments.

qTROSY: Recovery of the anti-TROSY magnetisation ( 05JB113-32 )

This experiment can be recorded using the basic parameter set available for a 2D inverse-detected experiment as, for instance, the HSQC experiment.

Tutorials: 2D inverse experiments

Tutorials: 2D gradient-based inverse experiments

The S³E element
The S³CT element

Related experiments:

2D Inverse experiments

2D Inverse gradient-enhanced experiments