The quality of the tuning and matching of an NMR probe on a Bruker NMR spectrometer can be monitored by using the wobble (or "wobb") routine in the TOPSPIN software. This routine sweeps the frequency using low power and displays a plot corresponding roughly to the absorbance vs frequency for the probe electronics. If the probe has very high sensitivity (eg: a cryoprobe) and contains a sample rich in protons (eg: water) then one is able to observe the proton spectrum in the frequency swept wobble curve. This is demonstrated in the figure below which shows wobble curves for a 600 MHz cryoprobe containing a sample of water.
The curves show the tuning profile of the probe with an anomaly at the proton frequency. The anomaly is the proton signal of the water in the NMR probe. The top panel is the wobble curve for the probe in a well-shimmed magnet and the bottom panel is the same curve after the magnet shims had been grossly maladjusted. One can see that the anomaly is much more broad in the wobble curve collected on a poorly shimmed magnet as one would expect the signal from the water to be much broader in an inhomogeneous magnetic field.
Thank you to Stan Woodman of Bruker Canada for pointing this phenomenon out to me.
Journal Highlight: On the tuning of high-resolution NMR probes
Journal Highlight: On the tuning of high-resolution NMR probes
http://www.spectroscopynow.com/common/images/thumbnails/14a0562f4b6.jpgThree optimum conditions for the tuning of NMR probes are compared: the conventional tuning optimum, the spin noise tuning optimum and the newly introduced frequency shift tuning optimum.
Read the rest at Spectroscopynow.com
nmrlearner
General
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12-01-2014 12:17 PM
[NMR paper] Ionization Behavior of Polyphosphoinositides Determined via the Preparation of pH Titration Curves Using Solid-State (31)P NMR.
Ionization Behavior of Polyphosphoinositides Determined via the Preparation of pH Titration Curves Using Solid-State (31)P NMR.
Ionization Behavior of Polyphosphoinositides Determined via the Preparation of pH Titration Curves Using Solid-State (31)P NMR.
Methods Mol Biol. 2013;1009:129-42
Authors: Graber ZT, Kooijman EE
Abstract
Detailed knowledge of the degree of ionization of lipid titratable groups is important for the evaluation of protein-lipid and lipid-lipid interactions. The degree of ionization is commonly evaluated by...
nmrlearner
Journal club
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05-18-2013 09:42 PM
[U. of Ottawa NMR Facility Blog] Cable Length and Probe Tuning
Cable Length and Probe Tuning
NMR probes can be tuned and matched on the bench or while in the magnet using a sweep generator and oscilloscope or a specialized tuning box such as the one available through Morris Instruments. More typically, probe tuning and matching are monitored using the electronics in the NMR console and preamplifier. In either case, it is important to realize that any filter or cable between the preamplifier and the probe is part of the rf circuit being tuned and should therefore be present while adjusting the tuning and matching capacitors of the probe. This is...
nmrlearner
News from NMR blogs
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04-04-2013 08:50 PM
[NMR paper] NMR for direct determination of K(m) and V(max) of enzyme reactions based on the Lambert W function-analysis of progress curves.
NMR for direct determination of K(m) and V(max) of enzyme reactions based on the Lambert W function-analysis of progress curves.
http://www.bionmr.com//www.ncbi.nlm.nih.gov/corehtml/query/egifs/http:--linkinghub.elsevier.com-ihub-images-PubMedLink.gif Related Articles NMR for direct determination of K(m) and V(max) of enzyme reactions based on the Lambert W function-analysis of progress curves.
Biochim Biophys Acta. 2012 Mar;1824(3):443-9
Authors: Exnowitz F, Meyer B, Hackl T
Abstract
(1)H NMR spectroscopy was used to follow the...
nmrlearner
Journal club
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04-03-2013 08:22 PM
A 250 GHz Gyrotron with a 3 GHz Tuning Bandwidth for Dynamic Nuclear Polarization
A 250 GHz Gyrotron with a 3 GHz Tuning Bandwidth for Dynamic Nuclear Polarization
Publication year: 2012
Source:Journal of Magnetic Resonance</br>
Alexander B. Barnes, Emilio A. Nanni, Judith Herzfeld, Robert G. Griffin, Richard J. Temkin</br>
We describe the design and implementation of a novel tunable 250 GHz gyrotron oscillator with >10 W output power over most of a 3 GHz band and >35 W peak power. The tuning bandwidth and power are sufficient to generate a >1 MHz nutation frequency across the entire nitroxide EPR lineshape for cross effect DNP, as well as to...
nmrlearner
Journal club
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03-30-2012 10:45 AM
[Question from NMRWiki Q&A forum] Tuning and matching problem on atma command
Tuning and matching problem on atma command
hello nmr wikier I am using Z-gradiant BBI probe on bruker AV-500 since last weak I am facing tuning and matching problem both by atma command and manually atmm command.ON atma command it is abroted in all standard sample and on atmm the coarse button did not arive only fine button active on proton channel while carbon channel work fine and befor reaching in mid of the curve the button reaches at end and curve goes away from center.I have tried by enlarging wbsw by 2o 40 60 but it is not working.I have also tried all command which are in BASH...
nmrlearner
News from other NMR forums
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10-05-2011 08:57 PM
[U. of Ottawa NMR Facility Blog] Probe Tuning and 90 Degree Pulses
Probe Tuning and 90 Degree Pulses
In order to get meaningful results from multiple-pulse NMR pulse sequences, it is essential that the 90° and 180° pulses are calibrated at the power levels used in the sequences (see this post for example). The calibrations are usually done on a standard sample in a well tuned and matched probe. The calibrations are typically stored in a file which is called up when setting up particular NMR experiments. It is important to know that these calibrations are correct for the particular sample of interest only when the probe is well tuned and matched. For...
NMR Signals in Tuning Curves
Linear Mode
