CAGEBIRD: improving the GBIRD filter with a CPMG sequence.

An improvement of the GBIRD-filter is presented. The current approach utilizes Carr–Purcell–Meiboom–Gill type pulse train during the BIRD delay. The method enables recording of purely absorptive 1D spectrum using only one isotope editing element. In the current method, the parent signal leakage due to JHH evolution during the BIRD delay is considerably smaller than in the conventional approach. As a consequence, the t1-noise is smaller also in 2D applications, such as GBIRD-filtered HSQC.