[Question from NMRWiki Q&A forum] Method for indirect 13C-1H J-couplings measurements
Method for indirect 13C-1H J-couplings measurements
Dear colleagues! 13C-1H J-couplings are essential in some areas of molecule structure research.
I discovered modern methods implemented in our software and found the following:
<ol> 13C J-resolved (recommended by Braun, Berger, Kalinovksy in 150 and more NMR experiments)
J-HMBC (once I used it, but as I remember, it would't work with J
nmrlearner
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11-12-2011 01:40 AM
[Stan NMR blog] Signs of geminal HH and HD couplings
Signs of geminal HH and HD couplings
A remark on the signs of geminal 2J(HD) and 2J(HH) couplings
Source: Stan blog library
nmrlearner
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02-13-2011 08:54 PM
Residual dipolar couplings: are multiple independent alignments always possible?
Residual dipolar couplings: are multiple independent alignments always possible?
Abstract RDCs for the 14 kDa protein hen egg-white lysozyme (HEWL) have been measured in eight different alignment media. The elongated shape and strongly positively charged surface of HEWL appear to limit the protein to four main alignment orientations. Furthermore, low levels of alignment and the proteinâ??s interaction with some alignment media increases the experimental error. Together with heterogeneity across the alignment media arising from constraints on temperature, pH and ionic strength for some...
nmrlearner
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12-26-2010 04:43 AM
[NMR paper] Residual dipolar couplings in NMR structure analysis.
Residual dipolar couplings in NMR structure analysis.
Related Articles Residual dipolar couplings in NMR structure analysis.
Annu Rev Biophys Biomol Struct. 2004;33:387-413
Authors: Lipsitz RS, Tjandra N
Residual dipolar couplings (RDCs) have recently emerged as a new tool in nuclear magnetic resonance (NMR) with which to study macromolecular structure and function in a solution environment. RDCs are complementary to the more conventional use of NOEs to provide structural information. While NOEs are local-distance restraints, RDCs provide...
nmrlearner
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11-24-2010 09:25 PM
[Question from NMRWiki Q&A forum] NOESY peak signs
NOESY peak signs
I am new to NOESY, so I have a number of question about interpreting resulting 2D spectra. Mixing time is 300 ms, substance - lactic acid. I have a NOESY spectrum (pulse program - noesygphp) with several peaks having sign structure as:
- -+- - I know that the peak with the sign "-" corresponds to dipolar-dipolar interaction, "+" - to chemical exchange. But I don't understand what my result means.
Check if somebody has answered this question on NMRWiki QA forum
nmrlearner
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11-02-2010 11:17 AM
[U. of Ottawa NMR Facility Blog] E.COSY and the Relative Signs of Coupling Constants
E.COSY and the Relative Signs of Coupling Constants
Spin-spin coupling constants can have values greater than or less than zero. The absolute sign of the coupling constants cannot be discerned from the simple examination of a 1H NMR spectrum. The E.COSY1 (Exclusive COrrelation SpectroscopY) technique is one method which can be used to determine the relative signs of coupling constants. E.COSY is a phase sensitive COSY variant which produces off-diagonal signals showing only the active coupling (i.e. the coupling directly responsible for the cross-peak) as 2x2 antiphase square tetrads...
nmrlearner
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08-21-2010 08:15 PM
A simple method for measuring signs of 1HN chemical shift differences between ground
Abstract NMR relaxation dispersion spectroscopy is a powerful method for studying protein conformational dynamics whereby visible, ground and invisible, excited conformers interconvert on the millisecond time-scale. In addition to providing kinetics and thermodynamics parameters of the exchange process, the CPMG dispersion experiment also allows extraction of the absolute values of the chemical shift differences between interconverting states,
ê
ê \Updelta ~
w
ê
ê , opening the way for structure determination of excited state conformers. Central to the goal of structural...
nmrlearner
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08-14-2010 04:19 AM
Measurement of signs of chemical shift differences between ground and excited protein
Abstract Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR spectroscopy has emerged as a powerful tool for quantifying the kinetics and thermodynamics of millisecond exchange processes between a major, populated ground state and one or more minor, low populated and often invisible â??excitedâ?? conformers. Analysis of CPMG data-sets also provides the magnitudes of the chemical shift difference(s) between exchanging states (|Î?Ï?|), that inform on the structural properties of the excited state(s). The sign of Î?Ï? is, however, not available from CPMG data. Here we present...
Signs of geminal HH and HD couplings
Linear Mode
