Hi, Equation 20 in that paper (http://dx.doi.org/10.1021/cr0404287) is actually the sum of the spin-spin relaxation and Rex! This is exactly what Troels has been working with recently. See http://wiki.nmr-relax.com/Matplotlib_DPL94_R1rho_R2eff. In the relaxation dispersion analysis in relax we should really have two parameters automatically generated for the user, R2 and Rex (defined as R2 = R1rho' + Rex). These could then be used to generate dispersion plots of R2 or Rex verses Omega_eff. This might take a while though, in the mean time have a look at Troels' script on that wiki page.
Regards, Edward On 26 March 2014 14:22, Justin Lecher <j.lec...@fz-juelich.de> wrote: > On 26/03/14 13:39, Edward d'Auvergne wrote: >> Hi, >> >> The key here is what is meant by R2. There are many different >> definitions. In relax, the parameter name R2 is defined as: >> >> - In the standard relaxation equations, spin-spin relaxation >> component. I.e. the part influenced by the spectral density function >> J(w). >> >> - Again in the standard relaxation equations, R2 is used for R2*, >> where R2* = R2 + Rex. R2* is also defined differently if you look at >> the exponential decay curves or if you looking at peak widths (for the >> later there are additional factors broadening the peaks which add to >> the R2* equation). >> >> - For relaxation dispersion, R2 is currently defined as R1rho', i.e. >> just the parts influenced by the spectral density function. Here >> R1rho' is the on-resonance part of R1rho, excluding exchange. >> >> R2 = R1rho' + Rex could also be defined, which is probably what you >> are after. The value of R1rho' + Rex has been named many different >> things by the field and there seems to be no consensus. I have >> discussed this with Troels at >> http://thread.gmane.org/gmane.science.nmr.relax.devel/5119/focus=5207. >> This is a long thread with many discussions about implementing this >> as an automatically calculated parameter - which in the end would be a >> great feature. >> >> So which R2 value are you after? >> >> Regards, >> >> Edward > > Hi Edward, > > Principally I am looking for pure R2 without Rex contribution. > > Currently we are using some home made scripts which basically are using > equation 20 in Palmer, Massi, 2006 (PMID 16683750). > > > So for the technical side, how do I proceed in relax? Do I need to fix > the decay for R1 and R1rho and then calculate R2 or just fit R1 and use > my raw intensities from the R1rho measurements for the R2 calculation? > > Thanks, > Justin > > > -- > Justin Lecher > Institute of Complex Systems > ICS-6 Structural Biochemistry > Research Centre Juelich > 52425 Juelich, Germany > phone: +49 2461 61 2117 > > _______________________________________________ relax (http://www.nmr-relax.com) This is the relax-users mailing list relax-users@gna.org To unsubscribe from this list, get a password reminder, or change your subscription options, visit the list information page at https://mail.gna.org/listinfo/relax-users
