relax: dynamics analysis, model-free analysis, relaxation data, R1 and R2 exponential curve-fitting, steady-state NOE calculation, reduced spectral density mapping, relaxation dispersion, N-state model, frame order dynamics theories, stereochemistry, conformational analysis, organic molecules, proteins, RNA, DNA, sugars, and other biomolecules.

relax - Molecular dynamics by NMR data analysis

Analysis software for: Model-free, NMR relaxation (R1, R2, NOE), reduced spectral density mapping, relaxation dispersion, N-state models, frame order theory.

Frequently Asked Questions (FAQ)

How do I obtain the newest relax source code?

To obtain the most up to date copy of the relax source code without waiting for a new release, the new code can be checked out from the repository by typing:

$ svn co svn:// relax-trunk

or if this doesn't work:

$ svn co relax-trunk

If you already have a checked out copy, try typing:

$ svn up

This requires installation of the subversion program. If the fitting of the R1 and R2 NMR relaxation rates is required, the relaxation curve-fitting C modules will need to be compiled using SCons. For more information, see the compilation subsection of the relax downloads page.

How do I check out a relax source code branch?

Sometimes code for a new analysis type or a new feature is developed within a dedicated branch within the relax repository. To obtain for example the incomplete relaxation dispersion relax branch, type:

$ svn co svn://


$ svn co

This will create the directory relax_disp containing the source code of the branch.

The equations (or units) used by relax are incorrect!

This is more a commonly stated point rather than a question. But if you believe that NMR relaxation data should be measured in Hertz, that the molecular correlation times or internal correlation times do not contain radian units, that the units for spherical harmonics is not radians, or that the rotation power spectral density functions do not contain radian units, the following links are for you.

Radians are a dimensionless and hidden unit ubiquitous to NMR. A detailed description of this hidden radian unit as used in NMR has been written as reference for understanding the unit in the context of the SI system. Copies of this description can also be found here, here or here.

A detailed derivation in the context of Abragam's relaxation equations may also help. Copies of this derivation can be found here or here as well.

The menu icons are missing in Linux.

On some Linux systems, the icons for the menu items are not shown. This was a decision taken by the Gnome developers at some point to keep the GUI minimal, though in recent versions this behaviour has been reverted. If you suffer from this problem, to reactive the icons simply type in the shell:

$ gconftool-2 --type boolean --set /desktop/gnome/interface/menus_have_icons true