DPL94

The Davis et al., 1994 2-site off-resonance fast exchange relaxation dispersion model for R1rho-type data. It extends the M61 model to off-resonance data, hence it collapses to this model for on-resonance data. The model is labelled as DPL94 in relax.

Equation

[math] \mathrm{R}_{1\rho}= \mathrm{R}_1\cos^2\theta + \left( \mathrm{R}_{1\rho}{´} + \frac{\Phi_\textrm{ex} \textrm{k}_\textrm{ex}}{\textrm{k}_\textrm{ex}^2 + \omega_\textrm{e}^2} \right) \sin^2\theta [/math]

Parameters

The DPL94 model has the parameters {$R_{1\rho}'$, $...$, $\Phi_{ex}$, $k_{ex}$}.

Parameter name space in relax

At time of writing (March 2014) the parameters in relax was stored as:

# Load the outcome from an free-spin analysis
state.load(state="results.bz2", dir="results/final")

# import spin functions
from pipe_control.mol_res_spin import return_spin, spin_loop

# Alias one spin
s13 = return_spin(":13@N")

# See attributes
dir(s13)

# See parameters
print(s13.params)
['r2', 'phi_ex', 'kex']

print(s13.r2)
print(s13.phi_ex)
print(s13.kex)

# See Ri data (ri_type:  The relaxation data type, i.e. 'R1', 'R2', 'NOE', or 'R2eff'. )
print(s13.ri_data)
{'R1': 1.3239399999999999}

# Or print for them all
for curspin, mol_name, res_num, res_name, spin_id in spin_loop(full_info=True, return_id=True, skip_desel=False):
    print(mol_name, res_num, res_name, spin_id, curspin.params, curspin.ri_data)

Reference

The reference for the DPL94 model is:

• Davis, D., Perlman, M., and London, R. (1994). Direct measurements of the dissociation-rate constant for inhibitor-enzyme complexes via the T1rho and T2 (CPMG) methods. J. Magn. Reson., 104(3), 266–275. (10.1006/jmrb.1994.1084)

Related models

The DPL94 model is simply the extension of the M61 model for off-resonance data.

Links

The implementation of the DPL94 model in relax can be seen in the:

• relax manual,
• API documentation,
• relaxation dispersion page of the relax website.