hmqcetgpsi.m

Sensitivity-improved echo/antiecho gradient-selected HMQC pulse sequence, based on the Bruker hmqcetgpsi pulse program and the standard HMQC sequence from https://doi.org/10.1016/0022-2364(83)90241-X and https://doi.org/10.1016/0022-2364(91)90036-S. The gradient selection is represented analytically by coherence order selection statements.

The Liouvillian is assembled as L=H+i*R+i*K, the two evolution time steps are the reciprocals of the sweep widths, and the J-coupling evolution time is delta=1/(2*|J|). The initial condition is Lz on the F2 nucleus and the detection state is L+ on the same nucleus. A 90-degree pulse on the F2 channel is followed by an evolution over delta, an inversion pulse and a 90-degree excitation pulse on the F1 channel, and the first half of the F1 evolution, run as a trajectory with npoints(1)-1 steps. Midpoint 180-degree pulses are then applied on every channel listed in parameters.decouple_f1, and the second half of the F1 evolution is run in refocusing mode.

The echo and the antiecho branches are separated at this point by retaining, respectively, the +1 and the -1 coherence order on the F1 nucleus. Each branch receives an inversion pulse and a 90-degree back-transfer pulse on the F1 channel, and then the sensitivity improvement block: an evolution over delta, a 90-degree F2 pulse together with an F1 inversion pulse, a second evolution over delta, an F2 inversion pulse together with a 90-degree F1 pulse about Ly, a third evolution over delta, and a final 90-degree F2 pulse about Ly. A 180-degree F2 pulse before acquisition is followed by the second analytical selection, onto zero coherence order on the F1 nucleus and +1 on the F2 nucleus. Decoupling of the channels listed in parameters.decouple_f2 is then applied by decouple.m function, and the two branches are detected separately with npoints(2)-1 steps. The function requires the sphten-liouv formalism.

Syntax

    fid=hmqcetgpsi(spin_system,parameters,H,R,K)

Parameters

    parameters.sweep              [F1 F2] sweep widths, Hz

    parameters.npoints            [F1 F2] numbers of points

    parameters.spins              {F1 F2} nuclei (e.g. '13C','1H')

    parameters.decouple_f2        nuclei to decouple in F2, e.g.
                                  {'15N','13C'}

    parameters.decouple_f1        nuclei that receive midpoint
                                  180-degree refocusing pulses in
                                  F1, e.g. {'1H'}

    parameters.J                  working scalar coupling, Hz

    H  - Hamiltonian matrix, received from context function

    R  - relaxation superoperator, received from context function

    K  - kinetics superoperator, received from context function

Outputs

    fid.pos,fid.neg -  echo and antiecho components of the
                       signal.

Notes

Note: natural abundance simulations should make use of the isotope dilution functionality. See dilute.m function.

The difference from hmqcetgp.m is the sensitivity improvement block between the back-transfer pulse and the acquisition; the parameter set and the coherence selection statements are the same.

See also

hmqcetgp.m, hmqc.m, hsqcedetgp.m, hsqc.m, dilute.m, Built-in experiments

Version 2.13, authors: Ilya Kuprov