Nuclear magnetic resonance resolving power

Nuclear magnetic resonance A powerful method for studies with proteins, as there is such a large number of resolved signals. 

Generally, the most powerful method for stmctural elucidation of steroids is nuclear magnetic resonance (nmr) spectroscopy. There are several classical reviews on the one-dimensional (1-D) proton H-nmr spectroscopy of steroids (267). C-nmr, a technique used to observe individual carbons, is used for stmcture elucidation of steroids. In addition, C-nmr is used for biosynthesis experiments with C-enriched precursors (268). The availability of higher magnetic field instmments coupled with the arrival of 1-D and two-dimensional (2-D) techniques such as DEPT, COSY, NOESY, 2-D J-resolved, HOHAHA, etc, have provided powerful new tools for the stmctural elucidation of complex natural products including steroids (269). 

Until quite recently, X-ray crystallography was the technique used almost exclusively to resolve the 3-D structure of proteins. As well as itself being technically challenging, a major limitation of X-ray crystallography is the requirement for the target protein in crystalline form. It has thus far proved difficult or impossible to induce the majority of proteins to crystallize. Nuclear magnetic resonance (NMR) is an analytical technique which can also be used to determine the three-dimensional structure of a molecule without the necessity for crystallization. For many years, even the most powerful NMR machines could resolve the 3-D structure of only relatively small proteins (less than 20-25 kDa). However, recent analytical advances now render it possible to successfully analyse much larger proteins by this technique. 

Nuclear magnetic resonance, especially NMR, offers a powerful means of characterizing and identifying individual phosphorus species in soils and sediments. In the case of waters, there is usually the need for preconcentration, and interferences may arise because of the corresponding increase in concentration of paramagnetic substances. However, if these difficulties are resolved, NMR provides a qualitative means of detecting the presence of functionally different phosphorus groups, such as phosphonates, orthophosphates, orthophosphate mono-and diesters, and pyrophosphates, within a sample. 

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