NS CPMG 2-site expanded

The relaxation dispersion model for the numeric solution (NS) to the Bloch-McConnell equations for SQ CPMG-type data. This uses the Maple expanded and fast equations from Nikolai Skrynnikov. The model is labelled as NS CPMG 2-site expanded in relax.

This type of model can be called silico derived, as it is a computer-assisted derivation for the equivalent computations, of the much more expensive numerical matrix-form.

This function is exact, just as the explicit Bloch-McConnell numerical treatments. It comes from a Maple derivation based on the Bloch-McConnell equations. It is much faster than the numerical Bloch-McConnell solution. It was derived by Nikolai Skrynnikov and is provided with his permission.

Parameters

The NS CPMG 2-site expanded model has the parameters {R₂⁰, ..., p_A, Δω, k_ex}.

Code

The library code: https://sourceforge.net/p/nmr-relax/code/ci/master/tree/lib/dispersion/ns_cpmg_2site_expanded.py

Reference

The reference for the NS CPMG 2-site expanded model is:

• Tollinger, M., Skrynnikov, N. R., Mulder, F. A. A., Forman-Kay, J. D., and Kay, L. E. (2001). Slow dynamics in folded and unfolded states of an sh3 domain. J. Am. Chem. Soc., 123(46), 11341-11352. (DOI: 10.1021/ja011300z)

Code origin

The code originates as optimization function number 5 from the fitting_main_kex.py script from Mathilde Lescanne, Paul Schanda, and Dominique Marion (see the mailing list discussion, the relax task with attached code and the file).

Links to the copyright licensing agreements from all authors are:

• Nikolai Skrynnikov,
• Martin Tollinger,
• Paul Schanda,
• Mathilde Lescanne,
• Dominique Marion.

Links

The implementation of the NS CPMG 2-site expanded model in relax can be seen in the:

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