I am a beginner in NMR spectroscopy and I would like to learn more about relaxation editing experiments vs PRE. A colleague of mine is doing the 13C CP-MAS NMR experim. and he using cellulose II powder, regenerated cellulose and milled reg cellulose. We are interested in C4 resonance of cellulose II, good resolved resonance, to better understand the supramolecular structure of cellulose II. As experiments: long relaxation experiments - PRE with aqueous CuSO4 solution of certain concentration, does the CuSO4 sol conc has any effect on the experim? What is the difference between relaxation editing experiments and PRE? Thank you for your help.
asked Oct 15 '10 at 01:13
Hello Nico T,
I work with solution NMR; nonetheless, I will put in my two cents.
One type of "Editing" can mean to reduce the long T1 delays in some solid state samples, and thus, reducing the recycle delay. See "Linser, R., Chevelkov, V., Diehl, A., and Reif, B. (2007) Sensitivity enhancement using paramagnetic relaxation in MAS solid-state NMR of perdeuterated proteins, J Magn Reson 189, 209-216"
Another type of editing with the same principles may be two reduce the crowding of NMR peaks in solution NMR. One method is termed SEMPRE( It is Italian to mean "always", as well as an acronym. Its from an Italian group :) ) : Concentration does matter .
"Kellner, R., Mangels, C., Schweimer, K., Prasch, S. J., Weiglmeier, P. R., Rosch, P., and Schwarzinger, S. (2009) SEMPRE: spectral editing mediated by paramagnetic relaxation enhancement, J Am Chem Soc 131, 18016-18017" "Fawzi, N. L., Doucleff, M., Suh, J. Y., and Clore, G. M. (2010) Mechanistic details of a protein-protein association pathway revealed by paramagnetic relaxation enhancement titration measurements, Proc Natl Acad Sci U S A 107, 1379-1384"
"Editing" in solution NMR can also mean, but I doubt this is what you are talking about. For instance, one could do a 15N/13C edited Noesy which can select for 12C attached protons of ligands. See "Andersson, P., and Otting, G. (2000) Time-shared X(omega(1))-half-filter for improved sensitivity in subspectral editing, J Magn Reson 144, 168-170."
To answer your next question, "PRE" is mainly used to get quantitative information. In this way the Solomon-Bloembergen equation is used: See wiki link: paramagnetic relaxation enhancement (!updated!) It can also mean assays like paramagnetic protection assays. (For a paramagnetic protection assay, See:
"editing": Is more used as a qualitative term (when referring to paramagnetic NMR) to enhance the spectra or select for certain characteristics.
Incidentally, did you go to the Midwest NMR GRASP meeting? I remember a Nico (that worked with solid state NMR) presenting there.
answered Jan 25 '11 at 12:29