Abundance Carbon-13 Nuclear Magnetic Resonance Research Articles

Carbon-13 NMR Investigations of the Orientational Order in a Columnar Liquid Crystal

We report a natural abundance carbon-13 nuclear magnetic resonance (NMR) investigation of benzene dissolved in a columnar liquid crystal formed by the carbohydrate mesogen octa-O-decanoyl-β-cellobiose (Cel-II-10). The alignment of the mesophase in the magnetic field is sensitive to the field strength and to the thermal history of the sample. From carbon-13 line shapes, the director distribution functions and the molecular order parameter of the solute were estimated. In contrast to most columnar phases, Cel-II-10 aligns parallel to the magnetic field. The orientational order parameter of benzene is positive, which is expected for a columnar liquid crystal where the symmetry axis of the disk is aligned parallel to the column axis. However, an unexpected increase of the order parameter with increased temperature was observed. This behavior is probably a consequence of an exchange process between different solvation sites in the columnar mesophase and indicates that the population in the environment with higher order parameter increases when the sample is heated.

13C-NMR studies of membrane lipid-protein interactions upon protein heat denaturation

Spinach chloroplast membranes were studied by natural abundance carbon-13 nuclear magnetic resonance ( 13C-NMR) spectroscopy in their normal state and after heat denaturation of membrane proteins. The membrane proteins were denatured by raising the temperature of the sample to 67°C for 5 minutes [YashRoy, R.C. (1991) J. Biochem. Biophys. Methods 22, 55–59]. Line-broadening of 13C-NMR resonances arising from the 1st (carbonyl), 7th, 9th and 12th carbon atom of fatty-acyl chains with reference to the carbonyl (C-1) group shows increased immobilization of lipid fatty-acyl chains at these locations, obviously caused by changes in interactions between membrane lipids and proteins upon heat denaturation of membrane proteins.

Non-destructive analysis of the oil composition of soybean seeds by natural abundance carbon-13 nuclear magnetic resonance spectroscopy.

The signals of fatty acids in the form of triglycerides were observed in the 13C NMR spectrum of an intact soybean seed. The major fatty acid component composition of triglycerides in a soybean seed, which includes linoleic acid, oleic acid and palmitic acid, was estimated by subtracting the spectra of authentic fatty acids from the spectrum of the intact soybean seeds. The fatty acid compositions of seeds of 11 Japanese soybean cultivars and 5 lines bred at the Asian Vegetable Research and Development Center (AVRDC) were estimated by this rapid (within lhr for one seed) and nondestructive analytical method.

Natural abundance carbon-13 nuclear magnetic resonance studies of histone and DNA dynamics in nucleosome cores.

Natural abundance carbon-13 nuclear magnetic resonance spectra (67.9 MHz) were obtained for native nucleosome cores: cores dissociated in 2 M NaCl and 2 M NaCl, 6 M urea; and cores degraded with DNase I plus proteinase K. Phosphorus-31 NMR spectra of native and dissociated cores and core length DNA were also obtained at 60.7 MHz. The 31P resonance and spin-lattice relaxation time (T1) of DNA were only slightly affected by packaging in nucleosome cores, in agreement with other reports, but 13C resonances of DNA were essentially unobservable. The loss of DNA spectral intensity suggests that rapid internal motions of DNA sugar carbons in protein-free DNA previously demonstrated by 13C NMR methods are partly restricted in nucleosomes. The 13C spectrum of native cores contains many narrow intense resonances assigned to lysine side chain and alpha-carbons, glycine alpha-carbons, alanine alpha- and beta- carbons, and arginine side chain carbons. Several weaker resonances were also assigned. The narrow line widths, short T1 values, and non-minimal nuclear Overhauser enhancements of these resonances, including alpha- and beta-carbons, show that some terminal chain segments of histones in nucleosomes are as mobile as small random coil polypeptides. The mobile segments include about 9% of all histone residues and 25% of all lysines, but only 10% of all arginines. The compositions of these segments indicate that mobile regions are located in amino- or carboxyl-terminal sequences of two or more histones. In addition, high mobility was observed for side chain carbons of 45-50% of all lysines (delta and epsilon carbons) and about 25% of all arginines (zeta carbon) in histones (including those in mobile segments), suggesting that basic residues in terminal histone sequences are not strongly involved in nucleosome structure and may instead help stabilize higher order chromatin structure.

Carbon nuclear magnetic resonance spectra of oligosaccharides isolated from human milk and ovarian cyst mucin

Natural abundance Carbon-13 nuclear magnetic resonance spectra at 20 MHz were reported for the three common human milk oligosaccharides, lacto- N-tetraose and lacto- N-fucopentaoses I and II, as well as for two related tetra- and hexasaccharide alditols isolated from the alkaline borohydride degradation products of an ovarian cyst glycoprotein. Spectral assignments made with the help of deuterium-induced shift (DIS), attached proton test (APT), and T 1 data indicated some very irregular glycosylation shifts which were attributed to effects of steric crowding and non-nearest-neighbor interactions. Samples as small as 10 μmol of oligosaccharide gave acceptable 20-MHz spectra with the use of a 5-mm probe coil.

Backbone and side-chain motion in myosin, subfragment 1, and rod determined by natural abundance carbon-13 NMR.

We report natural abundance carbon-13 nuclear magnetic resonance studies of myosin, subfragment 1 (S-1), and myosin rod in solution and of myosin filaments. We measured solution spectra at 37.7 MHz, 20 degrees C with scalar proton decoupling. If the native proteins were rigid particles, only S-1 would have observable intensity. In fact, 30% of myosin, 70% of S-1, and 30% of rod carbons are observable. Observable carbons possess rotational correlation times less than 10(-7) s which effectively average 13C-1H dipolar coupling and anisotropic chemical shift interactions. Short alpha-carbon region spin-lattice relaxation times (T1) and nonminimal 13C-1H nuclear Overhauser enhancements suggest restricted nanosecond motions of backbone atoms. This is direct evidence for internal motion of backbone and side-chain carbons in myosin and its fragments. Double resonance experiments at 15.1 MHz and 5 degrees C with pelleted myosin filaments detected carbon atoms in rigid domains. While most (80%) aliphatic carbons are strongly 13C-1H dipolar coupled due to limited motion, they have short T1 values and large nuclear Overhauser enhancement values; this is evidence for high frequency restricted motion. Cross-polarization experiments show that the 13C carbonyl line width is motionally narrowed, suggesting broad backbone motions in the 100 mus range. Thus, motion in filaments is highly anisotropic.

In vivo detection of cryoprotectants and lipids in overwintering larvae using carbon-13 nuclear magnetic resonance spectroscopy

Natural abundance carbon-13 nuclear magnetic resonance (NMR) spectra of intact, acclimated Eurosta solidaginis larvae have been obtained. The spectra show peaks assignable to lipid components and the presence of one major type of monounsaturated fatty acid. Chloroform-soluble extracts of whole larvae support this. The major nonlipid carbon components were the two cryoprotectant polyols glycerol and sorbitol. Carbon-13 NMR is a useful tool for analysis of cryoprotectant molecules in whole, living cold acclimated freezing tolerant insects.

Revised guidance on acceptable limits of exposure during nuclear magnetic resonance clinical imaging.

Revised guidance on acceptable limits of exposure during nuclear magnetic resonance clinical imaging.

Natural abundance Carbon-13 nuclear magnetic resonance spectroscopy of liver and adipose tissue of the living rat.

We have employed the topical magnetic resonance (TMR) technique to obtain natural abundance 13C nuclear magnetic resonance (NMR) spectra from liver and adipose tissue in the living rat. Experiments were performed in a TMR magnet (20-cm diameter) with a two-turn radio-frequency coil ("surface" coil) combined with a focused static magnetic field. The in vivo spectra that were obtained at 20.2 MHz have been assigned by comparison with those from excised organs obtained in a conventional spectrometer operating at 90.5 MHz. Signals in the TMR spectra corresponding to carbons of the carbohydrates, glucose and glycogen, and of the lipids, triglycerides and phospholipids, have been resolved in vivo and assigned. The effects of chronic modification of dietary fat and carbohydrate on the in vivo spectra have been investigated. The levels of carbohydrates and of saturated and unsaturated fats in the liver as measured by 13C TMR reflect the relative amounts of these compounds in the long-term diet.

A Carbon-13 NMR Assignment Study of Certain 6-Substituted Dibenz [c,e] Azepine 5, 7-Dione

Abstract The natural abundance carbon-13 nuclear magnetic resonance spectra of diphenic acid and some 6-substituted dibenz [c,e] azepine, 5, 7-dione - which can be considered also as N-substituted diphenimide - were recorded using Fourier transform technique. The chemical shifts of various carbon resonance have been assigned on the basis of chemical shift theory, the signal multiplicity observed in the single frequency off-resonance decoupled (SFORD) spectra and comparison with the chemical shifts of the model compounds.

13C nuclear magnetic resonance spectra of some C19-diterpenoid alkaloids and their derivatives

The natural abundance carbon-13 nuclear magnetic resonance spectra of some C19-diterpenoid alkaloids and their alkamines (lappaconitine, lappaconine, lapaconidine, ranaconine, 14-dehydrobrowniine, aconine, pseudoaconine, deoxyaconine, and hypaconine) have been determined at 15.03 MHz. With the aid of proton decoupling techniques, additivity relationships, and comparison with spectra of related alkaloids, self-consistent and unambiguous assignments of nearly all carbon resonances for these alkaloids have been made. Some important chemical shift trends have been observed, which are useful for identifying the basic C19-diterpenoid alkaloid skeleton and the hydroxy and methoxy group substitution patterns in these alkaloids. On the basis of 13C nmr spectra of lappaconitine and lappaconine, the anthranoyl ester moiety is assigned to the C-4 position in lappaconitine. The 13C nmr spectra of lapaconidine, aconine, and pseudoaconine taken in pyridine and chloroform have been compared to determine the conformational changes of the ring A hydroxy groups in these alkaloids.

Carbon-13 Nuclear Magnetic Resonance Spectrum of Xylocaine

Abstract The natural abundance carbon-13 nuclear magnetic resonance spectrum of xylocaine was obtained using the pulse Fourier transform technique. The various carbon resonances in the proton noise decoupled spectrum of xylocaine have been assigned on the basis of chemical shift theory, multiplicity observed in SFORD spectrum, signal intensity, relaxation time and comparison with the structurally related compounds.

Carbon-13 Nuclear Magnetic Resonance Spectrum of Quinacrine

Abstract The natural abundance carbon-13 nuclear magnetic resonance spectrum of quinacrine was determined using the pulse Fourier transform technique. The chemical shift of various carbon resonances have been assigned on the basis of the substituent effects on benzene shifts, multiplicities generated in SFORD spectrum and comparison with structurally related compounds.

Carbon-13 Nuclear Magnetic Resonance Spectra of Substituted-1,2,4-triazoles

Abstract The natural abundance carbon-13 nuclear magnetic resonance spectra of 5-(1-naphthylmethyl)-4-(2-methoxyphenyl)-1, 2, 4-triazol-3-thiol and 5-(1-naphthylmethyl)-4-(2-methoxyphenyl)-1, 2, 4-triazol-3-yl-thioglycolic acid were recorded using Fourier transform techniques. The chemical shift of various carbon resonances of these compounds have been assigned on the basis of the chemical shift theory, the signal multiplicity observed in the single frequency off-resonance decoupled (SFORD) spectra and comparison with the chemical shifts of model compounds.

Fourier Transform13C NMR Analysis of Biotin

Abstract The natural abundance carbon-13 nuclear magnetic resonance spectrum of biotin was recorded using the pulse Fourier transform technique. The chemical shifts of various carbon resonances have been assigned on the basis of the 13C NMR chemical shift theory, multiplicities observed in SFORD spectrum and comparison with structurally related compounds.

Fourier Transform13C NMR Analysis of Some Methaqualone Metabolites

Abstract The natural abundance carbon-13 nuclear magnetic resonance spectra of some methaqualone metabolites were recorded using the pulse fourier transform technique. The chemical shift of various carbon resonances have been assigned on the basis of the chemical shift theory, multiplicities observed in SFORD spectrum and comparison with the chemical shifts of the corresponding carbons of methaqualone.

Photochemical reactivity of keto imino ethers. Determination of the stereochemistry of the type I rearrangement of 2-ethoxypyrrolin-5-ones by natural abundance carbon-13 and nitrogen-15 nuclear magnetic resonance spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochemical reactivity of keto imino ethers. Determination of the stereochemistry of the type I rearrangement of 2-ethoxypyrrolin-5-ones by natural abundance carbon-13 and nitrogen-15 nuclear magnetic resonance spectroscopyJohn M. Burns, Martin E. Ashley, Geoffrey C. Crockett, and Tad H. KochCite this: J. Am. Chem. Soc. 1977, 99, 21, 6924–6928Publication Date (Print):October 1, 1977Publication History Published online1 May 2002Published inissue 1 October 1977https://doi.org/10.1021/ja00463a025RIGHTS & PERMISSIONSArticle Views115Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (649 KB) Get e-Alerts Get e-Alerts

Spinach plastocyanin: Comparison of reduced and oxidized forms by natural abundance carbon-13 nuclear magnetic resonance spectroscopy

Differences between the reduced Cu(I) and oxidized Cu(II) forms of spinach plastocyanin were investigated by natural abundance carbon-13 nuclear magnetic resonance spectroscopy at 67.9 MHz using proton noise decoupling. The spectra confirm that histidines 38 and 91 are copper ligands and demonstrate that coordination is by the N o1 of both imidazole rings. Spectra of reduced plastocyanin yielded 128 separately resolved carbon resonances. Upon oxidation, 16 of these were observed to disappear; yet there was little change in the positions or intensities of other peaks. Those peaks which disappear are assigned to carbons near the metal. The protein evidently does not undergo a substantial change in conformation upon change of redox state.

Observation of ε- N-trimethyllysine residues of proteins by natural abundance carbon-13 nuclear magnetic resonance spectroscopy

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Natural abundance carbon-13 nuclear magnetic resonance studies of bovine white matter and myelin.

Whole bovine white matter yields a poorly resolved natural abundance 13C nuclear magnetic resonance (NMR) spectrum. The spectrum principally reflects carbon atoms of the constituent membrane lipids: several resonances could be specifically assigned but no resonances attributable to cholesterol are detectable. Except for the methyl group at the terminus of fatty acyl chains, lipid carbons giving rise to the 13C NMR spectrum have values of spin-lattice relaxation time between 140 and 500 ms, indicating significant restrictions on segmental and rotational mibolities but consistent with a generally fluid structural organization. The 13C NMR spectrum of myelin isolated from bovine white matter is similar to that for the whole white matter itself. In both white matter and isolated meylin, the integrated intensities for several carbon atoms are considerably less than those for the same carbon atoms in total lipid extracts. The data for white matter and myelin are consistent with a model in which observed line broadening is due to restrictions in the amplitude of chain flexing rather than to severe restrictions on chain segmental motion. Failure to detect resonances of cholesterol ring system carbon atoms may reflect marked anisotropy of rotational reorientation.