For small molecules, 1H 2D NOESY spectra exhibit positive NOE's between protons close to one another in space and the off-diagonal correlations are opposite in phase to those of the diagonals. As molecules become larger and larger the motional correlation times become longer and longer. As the correlation times become longer and longer, the NOE's become less positive, cross zero and then become negative. For large molecules, like proteins, the NOE's are negative and the off-diagonal correlations between close protons are of the same phase as the diagonal peaks. When the correlation times are extremely long, for example in rigid macromolecules or solids, the dipolar coupling among all of the protons is inefficiently averaged by molecular motions and spin diffusion becomes efficient. Spin diffusion allows all of the protons in a dipolar coupled network to exhibit correlations with one another. The sign of the correlations is similar to that observed for chemical exchange or negative NOE's. This phenomenon is demonstrated in the figure below. In the figure, positive contours are represented in black and negative contours are represented in red. The NOESY spectrum on the left is that of a solution of menthol in CDCl3. The off-diagonal correlations between proximate protons is opposite in phase compared to the diagonal responses, typical of small molecules with short correlation times. The NOESY spectrum on the right is that of the same solution of menthol dissolved in a very viscous fluorinated oil. The extreme viscosity of the sample is sufficient to make the correlation time for the molecules very long such that the menthol behaves like a very large macromolecule where spin diffusion is efficient. As a result, off-diagonal responses are of the same phase as those of the diagonal and are observed between all protons in the molecule.This technique has been cleverly applied* to mixtures of molecules immersed in viscous oils where intra-molecular correlations are observed whereas inter-molecular correlations are not observed. The data allow for the observation of the constituent components of complex mixtures.
* Andre J. Simpson, Gwen Woods, and Omid Mehrzad, Anal. Chem, 80, 186-194 (2008).
[Question from NMRWiki Q&A forum] Folding vs. Aliasing (in NOESY spectra)
Folding vs. Aliasing (in NOESY spectra)
Hi everyone
Does anyone happen to know if/how I can tell whether peaks outside the spectral width were either folded or aliased into a (NOESY) spectrum, when all I have is the spectrum file (in .ucsf format, say), and I do not know how the spectrum was recorded? I am not aiming at finding out whether there were any such 'outside peaks', what I would like to know is, in case there were some, where I would have to look for them.
Thanks a lot for your time!
nmrlearner
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02-02-2012 09:43 PM
[Question from NMRWiki Q&A forum] Auto peak picking of N15Edit NOESY and C13 Edit NOESY spectrum
Auto peak picking of N15Edit NOESY and C13 Edit NOESY spectrum
Dear friends,
I am in process of doing structure calculation of a dimeric protein. The problem I faced is regarding the assignment of N15Edit NOESY and C13 Edit NOESY spectrum.I have already processed the fid data and converted to sparky ucsf format. Is there options available in sparky for auto peak picking, integration and assignment of my NOESY spectrum? And second query is regarding the generation of input files for structure calculation. In our Lab we are using ARIA 2.1 software for structure calculation? Is there any...
nmrlearner
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12-14-2011 07:14 PM
Optimization of NMR spectroscopy of encapsulated proteins dissolved in low viscosity fluids
Optimization of NMR spectroscopy of encapsulated proteins dissolved in low viscosity fluids
Abstract Comprehensive application of solution NMR spectroscopy to studies of macromolecules remains fundamentally limited by the molecular rotational correlation time. For proteins, molecules larger than 30 kDa require complex experimental methods, such as TROSY in conjunction with isotopic labeling schemes that are often expensive and generally reduce the potential information available. We have developed the reverse micelle encapsulation strategy as an alternative approach. Encapsulation of...
nmrlearner
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07-15-2011 09:10 PM
[NMR paper] Simplification of protein NOESY spectra using bioorganic precursor synthesis and NMR
Simplification of protein NOESY spectra using bioorganic precursor synthesis and NMR spectral editing.
Related Articles Simplification of protein NOESY spectra using bioorganic precursor synthesis and NMR spectral editing.
J Am Chem Soc. 2004 May 5;126(17):5348-9
Authors: Lichtenecker R, Ludwiczek ML, Schmid W, Konrat R
A novel method is proposed for the analysis of protein NOEs in solution. In this approach, chemically synthesized precursor compounds for the amino acids valine, leucine, and isoleucine are used for amino acid specific labeling...
nmrlearner
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11-24-2010 09:51 PM
[NMR paper] Automated assignment of NOESY NMR spectra using a knowledge based method (KNOWNOE).
Automated assignment of NOESY NMR spectra using a knowledge based method (KNOWNOE).
Related Articles Automated assignment of NOESY NMR spectra using a knowledge based method (KNOWNOE).
J Biomol NMR. 2002 Aug;23(4):271-87
Authors: Gronwald W, Moussa S, Elsner R, Jung A, Ganslmeier B, Trenner J, Kremer W, Neidig KP, Kalbitzer HR
Automated assignment of NOESY spectra is a prerequisite for automated structure determination of biological macromolecules. With the program KNOWNOE we present a novel, knowledge based approach to this problem. KNOWNOE...
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11-24-2010 08:58 PM
[NMR paper] Suppression of diagonal peaks in TROSY-type 1H NMR NOESY spectra of 15N-labeled prote
Suppression of diagonal peaks in TROSY-type 1H NMR NOESY spectra of 15N-labeled proteins.
Related Articles Suppression of diagonal peaks in TROSY-type 1H NMR NOESY spectra of 15N-labeled proteins.
J Magn Reson. 1999 Oct;140(2):499-503
Authors: Meissner A, Sørensen OW
A novel method for suppression of diagonal peaks in the amide region of NOESY NMR spectra of 15N-labeled proteins is presented. The method is particularly useful for larger proteins at high magnetic fields where interference between dipolar and chemical shift anisotropy relaxation...
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11-18-2010 08:31 PM
[NMR paper] The effects of temperature, viscosity, and molecular size on the aluminum-27 QCT NMR
The effects of temperature, viscosity, and molecular size on the aluminum-27 QCT NMR of transferrins.
Related Articles The effects of temperature, viscosity, and molecular size on the aluminum-27 QCT NMR of transferrins.
J Magn Reson B. 1996 Feb;110(2):182-7
Authors: Aramini JM, Vogel HJ
A number of reports in recent years have demonstrated the feasibility of detecting quadrupolar metal ions bound tightly to rather large proteins via the quadrupolar central transition (QCT) NMR approach. In this article, an in-depth investigation of several...
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08-22-2010 02:27 PM
Theoretical Noesy Spectra
Hello
Does anybody know how can i obtain a theoretical Noesy Spectra?
Thanks in advance
J.I. MIranda