hsqcedetgp.m

Echo/antiecho gradient-selected multiplicity-edited HSQC pulse sequence, based on the Bruker hsqcedetgp pulse program and the standard HSQC sequence from https://doi.org/10.1016/0009-2614(80)80041-8, https://doi.org/10.1002/cmr.a.10095, and https://doi.org/10.1002/mrc.1260310315. 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. The INEPT block is a 90-degree F2 pulse, an evolution over delta/2, simultaneous 180-degree pulses on both channels, and a second evolution over delta/2. A trim pulse of parameters.trim_angle is then applied on the F2 channel, followed by a 90-degree F2 pulse about Ly and the transfer pulse on the F1 channel, which is taken as the difference between the +90-degree and the -90-degree rotations; this retains twice the part of the density matrix that changes sign with the phase of the F1 pulse and cancels the rest.

The first half of the F1 evolution is run as a trajectory with npoints(1)-1 steps, midpoint 180-degree pulses are applied on every channel listed in parameters.decouple_f1, and the second half is run in refocusing mode. The echo and the antiecho branches are separated by retaining zero coherence order on the F2 nucleus together with, respectively, the +1 and the -1 coherence order on the F1 nucleus. Multiplicity editing follows: an evolution over parameters.edit_time, simultaneous 180-degree pulses on both channels, and a second evolution over parameters.edit_time. Back transfer is a simultaneous 90-degree pulse on both channels, an evolution over delta/2, simultaneous 180-degree pulses, and a further evolution over delta/2. The second analytical selection, onto zero coherence order on the F1 nucleus and +1 on the F2 nucleus, is followed by decoupling of the channels listed in parameters.decouple_f2 by decouple.m function and by separate detection of the two branches with npoints(2)-1 steps. The function requires the sphten-liouv formalism.

Syntax

    fid=hsqcedetgp(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','13C'}

    parameters.J                  working scalar coupling, Hz

    parameters.trim_angle         proton trim pulse angle, rad

    parameters.edit_time          multiplicity editing delay, s

    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 multiplicity editing block is a pair of parameters.edit_time delays around simultaneous 180-degree pulses on both channels, and so the total editing period is twice parameters.edit_time.

See also

hsqc.m, ct_hsqc.m, clip_hsqc.m, hmqcetgp.m, hmqcetgpsi.m, dilute.m, Built-in experiments

Version 2.13, authors: Ilya Kuprov