We describe a novel approach to the rapid collection and processing of multidimensional NMR data: "high-resolution iterative frequency identification for NMR" (HIFI-NMR). As with other reduced dimensionality approaches, HIFI-NMR collects n-dimensional data as a set of two-dimensional (2D) planes. The HIFI-NMR algorithm incorporates several innovative features. (1) Following the initial collection of two orthogonal 2D planes, tilted planes are selected adaptively, one-by-one. (2) Spectral space is analyzed in a rigorous statistical manner. (3) An online algorithm maintains a model that provides a probabilistic representation of the three-dimensional (3D) peak positions, derives the optimal angle for the next plane to be collected, and stops data collection when the addition of another plane would not improve the data model. (4) A robust statistical algorithm extracts information from the plane projections and is used to drive data collection. (5) Peak lists with associated probabilities are generated directly, without total reconstruction of the 3D spectrum; these are ready for use in subsequent assignment or structure determination steps. As a proof of principle, we have tested the approach with 3D triple-resonance experiments of the kind used to assign protein backbone and side-chain resonances. Peaks extracted automatically by HIFI-NMR, for both small and larger proteins, included ~98% of real peaks obtained from control experiments in which data were collected by conventional 3D methods. HIFI-NMR required about one-tenth the time for data collection and avoided subsequent data processing and peak-picking. The approach can be implemented on commercial NMR spectrometers and is extensible to higher-dimensional NMR.
[NMR paper] Effective rotational correlation times of proteins from NMR relaxation interference.
Effective rotational correlation times of proteins from NMR relaxation interference.
Related Articles Effective rotational correlation times of proteins from NMR relaxation interference.
J Magn Reson. 2006 Jan;178(1):72-6
Authors: Lee D, Hilty C, Wider G, Wüthrich K
Knowledge of the effective rotational correlation times, tauc, for the modulation of anisotropic spin-spin interactions in macromolecules subject to Brownian motion in solution is of key interest for the practice of NMR spectroscopy in structural biology. The value of tauc enables...
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12-01-2010 06:56 PM
[U. of Ottawa NMR Facility Blog] Faster Relaxation Time Measurements in Solids
Faster Relaxation Time Measurements in Solids
T1 relaxation times are typically measured with the inversion recovery technique. In this method the magnetization is inverted and its recovery is monitored as a function of time. For nuclei with long T1's, the measurements are very time consuming as a recycle delay of at least five times T1 must be used between scans. Typical T1's for 13C in the solid state range from several seconds to tens of minutes, so their direct measurement via the inversion recovery method could be prohibitively long.
High resolution 13C solid state NMR spectra of...
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08-21-2010 08:15 PM
[NMR software blog] Faster Faster Faster
Faster Faster Faster
Our machines, even when hitting an apparent performance peak, only run at one small fraction of their true potential speed. I feel that today's computers and their software are OK for routine spectra. I couldn't ask for more. Other spectra are quite large, however, and I must wait a few seconds during processing. Without going into the third dimension, consider these novel experiments to measure long range heteronuclear Js. Each row contains at least 4096 points. Quite likely we are going to see larger rows in the next few years. The time required to compute the FFT is...
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08-21-2010 06:29 PM
[NMR paper] Assessing potential bias in the determination of rotational correlation times of prot
Assessing potential bias in the determination of rotational correlation times of proteins by NMR relaxation.
Related Articles Assessing potential bias in the determination of rotational correlation times of proteins by NMR relaxation.
J Biomol NMR. 1999 Feb;13(2):101-12
Authors: Lee AL, Wand AJ
The various factors that influence the reliable and efficient determination of the correlation time describing molecular reorientation of proteins by NMR relaxation methods are examined. Nuclear Overhauser effects, spin-lattice, and spin-spin relaxation...
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08-21-2010 04:03 PM
HIFI-C: a robust and fast method for determining NMR couplings from adaptive 3D to 2D projections
HIFI-C: a robust and fast method for determining NMR couplings from adaptive 3D to 2D projections
Gabriel Cornilescu, Arash Bahrami, Marco Tonelli, John L. Markley and Hamid R. Eghbalnia
Journal of Biomolecular NMR; 2007; 38(4); pp 341-351
Abstract:
We describe a novel method for the robust, rapid, and reliable determination of J couplings in multi-dimensional NMR coupling data, including small couplings from larger proteins. The method, “High-resolution Iterative Frequency Identification of Couplings” (HIFI-C) is an extension of the adaptive and intelligent data collection approach...