A T₂ filter can be incorporated as a building block to monitor the T₂ relaxation times of the different signals or molecules of the analyzed sample. The only requirement is that the input magnetization msut be in the transverse plane.

Some applications:

• Measurement of T₂ ¹ relaxation times using the CPMG experiment
• Measurement of T₂ ¹³C and ¹⁵N relaxation times of labeled biomolecules using modified HSQC experiments.
• Detection of small molecules in the presence of large biomolecules or study of ligand-protein complexes

Easy implementation on AVANCE spectrometers.

The user only needs to define the overall duration of the filter. For T₂ measurements a list of filter delays must be defined as a function of the resonances to be observed. In experiments involving differentiation, the filter delay is set as a function of the molecular sizes of the involved species.

The most simple way to implement the T₂ filter in a pulse program is as follows:

... 3 d20 p2 ph2 d20 lo to 3 times c ...

where d20 is a fixed echo time to allow elimination of diffusion and J-modulated effects, p2 is the 180 degree pulse, and the loop is repeated c times in order to the overall filter to be extended by a time of (d20*2+p2)*c times.

More complicated pulse sequences involving equivalent filters are also available: