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
On 26 March 2014 12:58, Justin Lecher <j.lecher@xxxxxxxxxxxxx> wrote:
On 26/03/14 12:47, Troels Emtekær Linnet wrote:
Hi Justin.
If one have R1, and R1rho, R2 (R1rho') is fitted in:
http://wiki.nmr-relax.com/DPL94
http://wiki.nmr-relax.com/TAP03
http://wiki.nmr-relax.com/TP02
http://wiki.nmr-relax.com/NS_R1rho_2-site
R1+(R2) can be made by:
http://wiki.nmr-relax.com/Tutorial_for_R1/R2_Relaxation_curve-fitting_analysis_on_varian_recorded_as_fid_interleaved
(A tutorial I made for our students in our lab. We have Varian at our
place).
Best
Troels
Hi Troels,
perfect, thanks! I found the wiki pages, but I wasn't sure which one is
the best to choose. Any general suggestion or does it strictly depend on
the type of model which applies best to my system?
thanks
Justin
--
Justin Lecher
Institute of Complex Systems
ICS-6 Structural Biochemistry
Research Centre Juelich
52425 Juelich, Germany
phone: +49 2461 61 2117
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Re: R2 from R1rho & R1