Related ArticlesThe downfield resonances in the 1H NMR spectra of Azotobacter vinelandii and Pseudomonas putida seven-iron ferredoxins.
J Biol Chem. 1990 Jul 25;265(21):12388-92
Authors: Cheng H, Grohmann K, Sweeney W
Pseudomonas putida and Azotobacter vinelandii ferredoxins each contain one [4Fe-4S] cluster and one [3Fe-4S] cluster. Their polypeptide chains are nearly identical, differing by only 15 residues out of a total of 106. T1 measurements and temperature dependence studies of the 1H NMR spectrum of each ferredoxin demonstrate that all six resolved downfield resonances are near an iron-sulfur center. The five most downfield resonances are shown to arise from protons on cysteinyl beta-carbons by incorporation of cysteine deuterated at the beta-carbon into cell protein. The sixth peak (10.5 ppm) is shown to be a non-cysteinyl proton. This peak resolves into two resonances of approximately equal intensity at temperatures below 15 degrees or above 25 degrees C. A nuclear Overhauser effect observed between the two downfield-most resonances of A. vinelandii ferredoxin indicates that they originate from a geminal pair of beta-cysteinyl protons. An Overhauser effect observed between the resonances at 22.3 and 15.7 ppm, in conjunction with other results, implies that the resonance at 22.3 ppm arises from a beta-proton on the 3Fe-center-bound Cys16, while the resonance at 15.7 ppm arises from Cys45 beta-proton, which is bound to the 4Fe center. The five most downfield resonances are pH-dependent. The sixth peak (10.5 ppm in P. putida ferredoxin) is pH-independent. Possible origins for the observed pH dependencies are discussed.
[Question from NMRWiki Q&A forum] Downfield carbon paired with a upfield proton
Downfield carbon paired with a upfield proton
Dear sirsI have a natural product whose two carbon resoances are appearinga t 46 and 56 ppm but theirs proton resoanances are appearinga at 0.80 and 0.83 ppm respectively. I am unable to understand how there could be a downfield carbon (oxygenated carbon) is paird up with a upfield proton. I request your expert answer.Thanks in advance.
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FEBS Lett. 1995 Apr 10;362(3):333-6
Authors: Bycroft M, Proctor M, Freund SM, St Johnston D
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[NMR paper] NMR studies of Azotobacter vinelandii and Pseudomonas putida seven-iron ferredoxins.
NMR studies of Azotobacter vinelandii and Pseudomonas putida seven-iron ferredoxins. Direct assignment of beta-cysteinyl carbon NMR resonances and further proton NMR assignments of cysteinyl and aromatic resonances.
Related Articles NMR studies of Azotobacter vinelandii and Pseudomonas putida seven-iron ferredoxins. Direct assignment of beta-cysteinyl carbon NMR resonances and further proton NMR assignments of cysteinyl and aromatic resonances.
J Biol Chem. 1992 Apr 25;267(12):8073-80
Authors: Cheng H, Grohmann K, Sweeney W
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NMR of Naphthalene: why are the alpha-protons more downfield than the beta- protons?
Hi, can you please help me explain why the alpha-protons of naphthalene are further downfield? I know that the protons at the alpha position must be more deshielded, but I don't know how to explain why they have less electron density compared to the beta protons. Does this have to do with the number of double bonds that can be drawn in different resonance structures? Thanks for your help!Thanks so much!