Super-conducting NMR magnets are cooled with liquid helium. The boil off rate of the liquid helium is minimized by surrounding it with a high vacuum and a liquid nitrogen cryostat. The liquid nitrogen cryostat may either be vented directly to the atmosphere or it may be maintained at a pressure slightly above atmospheric pressure with the use of pressure relief valves. NMR users should be aware that the homogeneity of an NMR magnet is affected drastically by the pressure in the liquid nitrogen cryostat. The left-hand panel of the figure below shows a well resolved 400 MHz 1H NMR spectrum of the methyl triplet of ethylbenzene in a well shimmed magnet where the nitrogen cryostat was maintained slightly above atmospheric pressure with pressure relief valves for several days. The spectrum in the right-hand panel was run under identical conditions after the cap to the nitrogen fill port was removed, relieving the pressure in the nitrogen cryostat.
[U. of Ottawa NMR Facility Blog] Resolution During a Liquid Nitrogen Refill
Resolution During a Liquid Nitrogen Refill
Just as it is not advisable to collect high resolution NMR data during (and shortly after) a liquid helium refill, it is similarly not advisable to collect data during a liquid nitrogen fill. The figure below illustrates this point. A 300 MHz NMR spectrometer was set up to collect an NMR spectrum every minute before, during and after a liquid nitrogen refill. The resolution deteriorates as soon as the one-way valves are removed from the nitrogen cryostat. One can see that the resolution during the fill is much worse than before the fill. Even 60...
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09-28-2011 07:25 PM
[NMR paper] Nitrogen-15 NMR studies of nitrogen metabolism in Picea glauca buds.
Nitrogen-15 NMR studies of nitrogen metabolism in Picea glauca buds.
Related Articles Nitrogen-15 NMR studies of nitrogen metabolism in Picea glauca buds.
Plant Physiol Biochem. 2004 Dec;42(10):803-9
Authors: Bagh K, Hiraoki T, Thorpe TA, Vogel HJ
In vivo (15)N nuclear magnetic resonance (NMR) as well as (15)N solid-state magic angle spinning (MAS) NMR spectroscopy were used to investigate nitrogen metabolism in cultured white spruce (Picea glauca) buds. Long-term as well as short-term experiments were carried out involving the use of...
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11-24-2010 10:03 PM
[NMR images] High pressure NMR spectroscopy
http://www.biologie.uni-regensburg.de/Biophysik/Kalbitzer/c2c/Grafik/pArnold_1.jpg
biologie.uni-regensburg.de
1/11/2010 8:48:44 AM GMT
High pressure NMR spectroscopy
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11-01-2010 09:23 AM
[NMR paper] High-resolution NMR study of the pressure-induced unfolding of lysozyme.
High-resolution NMR study of the pressure-induced unfolding of lysozyme.
Related Articles High-resolution NMR study of the pressure-induced unfolding of lysozyme.
Biochemistry. 1992 Sep 1;31(34):7773-8
Authors: Samarasinghe SD, Campbell DM, Jonas A, Jonas J
The pressure-induced reversible unfolding of lysozyme was investigated by high-resolution proton magnetic resonance spectroscopy by following the proton spectra of the following residues: His-15 epsilon 1, Trp-28 epsilon 3, Leu-17 delta 2, Cys-64 alpha, and Trp-108 epsilon 3. The...