Constant-time period  with J evolution

When X and Y are homonuclear spins and there is no coupling evolution during t₁ (T=2*d5=n/2J_XY). This is equivalent to a CT period in a IX spin system.

 

Evolution of X chemical shift: (t₁/2)+d5-(d5-t₁/2)=t₁
Evolution of J_IX coupling constant: (t₁/2)-d5+(d5-t₁/2)=0
Evolution of J_XX' coupling constant: (t₁/2)+d5+(d5-t₁/2)=2*d5
Evolution of J_XY coupling constant: (t₁/2)+d5+(d5-t₁/2)=2*d5

Example 1:  2D CT-HSQC experiment where I is ¹H, X is the ¹³C attached to I, and Y is a ¹³C attached to X.

Example 2: Another possibility is the evolution of J_XY when X and Y are homonuclear spins (2*d5=(2n+1)/4J_XY) as, for instance, in a  3D CBCA(CO)NH experiment in which I is CO, X is CB and Y is CA.

The same approach can be extended when X and Y are heteronuclear spins:

Example 3: Constant-time ¹⁵N period with evolution of J_NH and J_NCO but not J_NCA in a out-and-back 3D HNCA experiment.

 

 Example 4: Constant-time  ¹³CA period with evolution of J_CH and J_NCA but not J_CACO evolution in a 3D (HA)CANNH experiment.

     

 

Easy implementation on AVANCE spectrometers.