Nuclear magnetic resonance correlation spectroscopy COSY

Due to the great complexity of this class of molecules, nuclear magnetic resonance (NMR) and mass spectroscopy (MS) are the tools most widely used to identify cucurbitacins. Both one- and two-dimensional NMR techniques have been employed for the structural elucidation of new compounds 2D NMR, 1H-NMR, 13C-NMR, correlated spectroscopy (COSY), heteronuclear chemical shift correlation (HETCOR), attached proton test (APT), distortionless enhancement by polarization transfer (DEPT), and nuclear Overhauser effect spectroscopy (NOESY) are common techniques for determining the proton and carbon chemical shifts, constants, connectivity, stereochemistry, and chirality of these compounds [1,38,45-47]. 

Carbon peak assignments were not available in the earlier reports, and hence, a comprehensive study utilizing H, correlation spectroscopy (COSY), heteronuclear correlation (HETCOR), and heteronuclear multibond correlation (HMBC) nuclear magnetic resonance was undertaken. NMR CDCI3 (5 ppm vs. TMS (multiplicity H s coupling constant assignment)) 7.36 (d IH J5.4 Hz, H-2),... 

List of Abbreviations NMR, nuclear magnetic resonance O.D.260> optical density at 260 nm at 25 °C NOESY, nuclear Overhauser effect spectroscopy DQF-COSY, double quantum filtered correlation spectroscopy KP, potassium phosphate Tm, UV-melting point ER, endoplasmic reticulum PAGE, polyacrylamide gel electrophoresis TSP, trisilylpropionic acid sodium salt fid, free induction decay ffh, fifty-four-homologue j57iAf, methionine-rich domain of fifty-four-homologue. 

A measurement method that is often used to determine the C-labeling of metabolites is 2D [ C. H] correlation nuclear magnetic resonance spectroscopy (COSY). This method yields relative intensities of multiplets in the NMR spectra that correspond to the relative amounts of groups of isotopomers in which the observed atom is C-labeled and the adjacent carbon atoms in the carbon backbone are either C-labeled or not (Szyperski, 1995). If the compound of which the labeling pattern is measured was synthesized by a microorganism growing on a mixture of uniformly C-labeled and naturally labeled carbon substrate, then the relative intensities of NMR fine structures can be calculated from the fractions of molecules that stem from one or more substrate molecule(s) in the feed medium. This is done using so-called probability equations (Szyperski, 1995) that require as input the fraction of uniformly C-labeled medium substrate and the fraction of naturally C-labeled carbon. 

TTie TOCSY 2D NMR experiment correlates all protons of a spin system, not just those directly connected via three chemical bonds. For the protein example, the alpha proton, Ft , and all the other protons are able to transfer magnetization to the beta, gamma, delta, and epsilon protons if they are connected by a continuous chain—that is, the continuous chain of protons in the side chains of the individual amino acids making up the protein. The COSY and TOCSY experiments are used to build so-called spin systems—that is, a list of resonances of the chemical shift of the peptide main chain proton, the alpha proton(s), and all other protons from each aa side chain. Which chemical shifts correspond to which nuclei in the spin system is determined by the conventional correlation spectroscopy connectivities and the fact that different types of protons have characteristic chemical shifts. To connect the different spin systems in a sequential order, the nuclear Overhauser effect spectroscopy... 

FLZ fluconazole CD cyclodextrin P-CD P-cyclodextrin IH NMR proton Nucleic Magnetic Resonance spectroscopy 2D two dimensional COSY correlation SpectroscopY ROESY Rotating frame Overhauser Effect Spectros-copY NOE Nuclear Overhauser Effect [FI] host [Gj guest MOE Molecular Operating Environment. 

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