- Synopsis
- Defaults
- Keyword arguments
- Description
- The no chemical exchange models
- The SQ CPMG-type experiments
- The MMQ CPMG-type experiments
- The R1rho-type experiments
- Prompt examples

relax_disp.select_model

Select the relaxation dispersion model.

relax_disp.select_model(model=`R2eff')

model: The type of relaxation dispersion model to fit.

A number of different dispersion models are supported. This includes both analytic models and numerical models. Models which are independent of the experimental data type are:

**`R2eff' -**- This is the model used to determine the R2eff/R1
*r*ho values and errors required as the base data for all other models,

**`No***R*_{ex}' -- This is the model for no chemical exchange being present.

The currently supported analytic models are:

**`LM63' -**- The original Luz and Meiboom (1963) 2-site fast exchange equation with parameters {R20, ...,
*φ*_ex, kex}, **`LM63 3-site' -**- The original Luz and Meiboom (1963) 3-site fast exchange equation with parameters {R20, ...,
*φ*_ex, kex,*φ*_ex2, kex2}, **`CR72' -**- The reduced Carver and Richards (1972) 2-site equation for most time scales whereby the simplification R20A = R20B is assumed. The parameters are {R20, ..., pA, dw, kex},
**`CR72 full' -**- The full Carver and Richards (1972) 2-site equation for most time scales with parameters {R20A, R20B, ..., pA, dw, kex},
**`IT99' -**- The Ishima and Torchia (1999) 2-site model for all time scales with pA > > pB and with parameters {R20, ..., pA, dw, kex},
**`TSMFK01' -**- The Tollinger, Kay et al. (2001) 2-site very-slow exchange model, range of microsecond to second time scale. Applicable in the limit of slow exchange, when |R20A-R20B| < <
*k*_AB,kB < < 1/tau_CP. R20A is the transverse relaxation rate of site A in the absence of exchange. 2*tau_CP is is the time between successive 180 deg. pulses. The parameters are {R20A, ..., dw,*k*_AB}. **`B14' -**- The Baldwin (2014) 2-site exact solution model for all time scales, whereby the simplification R20A = R20B is assumed. The parameters are {R20, ..., pA, dw, kex},
**`B14 full' -**- The Baldwin (2014) 2-site exact solution model for all time scales with parameters {R20A, R20B, ..., pA, dw, kex},

The currently supported numeric models are:

**`NS CPMG 2-site 3D' -**- The reduced numerical solution for the 2-site Bloch-McConnell equations using 3D magnetisation vectors whereby the simplification R20A = R20B is assumed. Its parameters are {R20, ..., pA, dw, kex},
**`NS CPMG 2-site 3D full' -**- The full numerical solution for the 2-site Bloch-McConnell equations using 3D magnetisation vectors. Its parameters are {R20A, R20B, ..., pA, dw, kex},
**`NS CPMG 2-site star' -**- The reduced numerical solution for the 2-site Bloch-McConnell equations using complex conjugate matrices whereby the simplification R20A = R20B is assumed. It has the parameters {R20, ..., pA, dw, kex},
**`NS CPMG 2-site star full' -**- The full numerical solution for the 2-site Bloch-McConnell equations using complex conjugate matrices with parameters {R20A, R20B, ..., pA, dw, kex},
**`NS CPMG 2-site expanded' -**- The numerical solution for the 2-site Bloch-McConnell equations expanded using Maple by Nikolai Skrynnikov. It has the parameters {R20, ..., pA, dw, kex}.

The currently supported models are:

**`MMQ CR72' -**- The the Carver and Richards (1972) 2-site model for most time scales expanded for MMQ CPMG data by Korzhnev et al., 2004, whereby the simplification R20A = R20B is assumed. Its parameters are {R20, ..., pA, dw, dwH, kex}.
**`NS MMQ 2-site' -**- The numerical solution for the 2-site Bloch-McConnell equations for combined proton-heteronuclear SQ, ZQ, DQ, and MQ CPMG data whereby the simplification R20A = R20B is assumed. Its parameters are {R20, ..., pA, dw, dwH, kex}.
**`NS MMQ 3-site linear' -**- The numerical solution for the 3-site Bloch-McConnell equations linearised with kAC = kCA = 0 for combined proton-heteronuclear SQ, ZQ, DQ, and MQ CPMG data whereby the simplification R20A = R20B = R20C is assumed. Its parameters are {R20, ..., pA, dw(AB), dwH(AB), kex(AB), pB, dw(BC), dwH(BC), kex(BC)}.
**`NS MMQ 3-site' -**- The numerical solution for the 3-site Bloch-McConnell equations for combined proton-heteronuclear SQ, ZQ, DQ, and MQ CPMG data whereby the simplification R20A = R20B = R20C is assumed. Its parameters are {R20, ..., pA, dw(AB), dwH(AB), kex(AB), pB, dw(BC), dwH(BC), kex(BC), kex(AC)}.

The currently supported analytic models are:

On-resonance models are:

**`M61' -**- The Meiboom (1961) 2-site fast exchange equation with parameters {R1
*r*ho', ...,*φ*_ex, kex}, **`M61 skew' -**- The Meiboom (1961) 2-site equation for all time scales with pA > > pB and with parameters {R1
*r*ho', ..., pA, dw, kex},

Off-resonance models are:

**`DPL94' -**- The Davis, Perlman and London (1994) 2-site fast exchange equation with parameters {R1
*r*ho', ...,*φ*_ex, kex}, **`TP02' -**- The Trott and Palmer (2002) 2-site equation for all time scales with parameters {R1
*r*ho', ..., pA, dw, kex}. **`TAP03' -**- The Trott, Abergel and Palmer (2003) off-resonance 2-site equation for all time scales with parameters {R1
*r*ho', ..., pA, dw, kex}. **`MP05' -**- The Miloushev and Palmer (2005) 2-site off-resonance equation for all time scales with parameters {R1
*r*ho', ..., pA, dw, kex}.

The currently supported numeric models are:

**`NS R1***r*ho 2-site' -- The numerical solution for the 2-site Bloch-McConnell equations using 3D magnetisation vectors whereby the simplification R20A = R20B. Its parameters are {R1
*r*ho', ..., pA, dw, kex}. **`NS R1***r*ho 3-site linear' -- The numerical solution for the 3-site Bloch-McConnell equations using 3D magnetisation vectors whereby the simplification R20A = R20B = R20C is assumed and linearised with kAC = kCA = 0. Its parameters are {R1
*r*ho', ..., pA, dw(AB), kex(AB), pB, dw(BC), kex(BC)}. **`NS R1***r*ho 3-site' -- The numerical solution for the 3-site Bloch-McConnell equations using 3D magnetisation vectors. Its parameters are {R1
*r*ho', ..., pA, dw(AB), kex(AB), pB, dw(BC), kex(BC), kex(AC)}.

To pick the 2-site fast exchange model for all selected spins, type one of:

[numbers=none] relax> relax_disp.select_model('LM63')

[numbers=none] relax> relax_disp.select_model(model='LM63')