The application of a
15N filtering block in the
1H,
13C-HSQC pulse sequence (
A) allows the observation of
1H,
13C groups directly coupled to
15N nuclei. In the sequence in panel
B-1 no filtering will be observed and the resulting spectrum (
C-1) will contain all
1H,
13C groups adjacent to either
14N or
15N nuclei. The use of a
15N filter (
B-2) will result in only those
1H,
13C groups adjacent to a
15N nuclei being observed in the resulting
1H,
13C HSQC spectrum (
C2).
1H,
13C J-coupling is suppressed during acquisition using adiabatic bilevel decoupling (ad-bilev)
21. The pulse phases are: ϕ
1 = y; ϕ
2 = x, -x; ϕ
3 = x for the no filter sequence (panel
B-1) and y for the
15N filtered sequence (panel
B-2); ϕ
4 = y, –y for the no filter sequence and y, y for the
15N filtered sequence; ϕ
5 = y, -y for the no filter sequence x, -x for the
15N filtered sequence; ϕ
6 = x, x, -x, -x; ϕ
7 = x, x, x, x, -x, -x, -x, -x; ϕ
8 = x, x, x, x, y, y, y, y; ϕ
rec = x, -x, -x, x, y, -y, -y, y.