Carbon-13 Nuclear Magnetic Resonance Relaxation Research Articles

The viscosity of polymer–surfactant mixtures in water

The viscosity of aqueous solutions of poly(ethyleneoxide) (PEO) in the dilute and semidilute regimes exhibits a maximum as a function of sodium dodecyl sulfate (SDS) concentration. The maximum is shown to correspond to the point at which the polymer coils are saturated with surfactant. From intrinsic viscosity and small angle neutron scattering (SANS), we obtain a value of 0.65 for the excluded volume exponent of PEO at saturation. Carbon-13 nuclear magnetic resonance (NMR) relaxation measurements indicate that the correlation time for local segmental motion for polymer segments attached to micelles is reduced from about 10−11 to 10−9 s. However, only a relatively small fraction of the total coil is in direct contact with the micelles at saturation. A model for the polymer–surfactant complex is presented based on these considerations.

Carbon-13 nuclear magnetic resonance relaxation study of chymotrypsin inhibitor 2 (CI-2)

Carbon-13 T1 and NOE measurements were used to study the internal motions of the single phenylalanine residue in CI-2 and in a mutant in which an arginine residue adjacent to the Phe had been replaced with an alanine residue. Each protein was specifically enriched with [13C6-ring]phenylalanine. The arginine to alanine modification resulted in a reduction of the order parameter, S2, from 0.39 to 0.32 for the internal motions of the aromatic ring. This is consistent with the aromatic side-chain of Phe 69 being less restricted, as a consequence of the removal of the neighbouring bulky side chain. Wild-type CI-2 was also successfully enriched with [2-13C]glycine. An average order parameter of 0.60 was obtained for the α-carbon positions of the three glycine residues. When bound to the serine protease chymotrypsin, S2 remains unchanged within experimental error. However, the overall tumbling, derived from NMR, slows by a factor of 5, consistent with the increase in molecular weight.

A carbon-13 nuclear magnetic resonance relaxation study of the reentrant 60CB–80CB

The carbon-13 spin-lattice relaxation times of the protonated ring carbons of octyloxycyanobiphenyl (80CB) in a 26 wt.% mixture of perdeuterated hexyloxycyanobiphenyl (60CB–d21) in 80CB are measured as a function of temperature at 22.63 MHz in the nematic (N), smectic A(SA), and reentrant nematic (RN) phases. The deuterium spectral densities of the ring deuterons of 60CB–d21 in the same sample were studied previously, and the diffusion coefficients [Formula: see text] and [Formula: see text] found in that study are used to calculate the theoretical carbon-13 relaxation times of the protonated ring carbons of 60CB. The general agreement of the theoretical values for 60CB with the experimental values for 80CB demonstrates that the two constituent molecules of the reentrant have similar motions. Small differences, similar in nature to those encountered in other studies of this interesting reentrant, however, do exist in the nematic and reentrant nematic phases and are discussed in terms of the molecular pairing model proposed by Cladis. (Phys. Rev. Lett. 35, 48 (1975).)

Carbon-13 nuclear magnetic resonance relaxation of amylose and dynamic behavior of the hydroxymethyl group

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbon-13 nuclear magnetic resonance relaxation of amylose and dynamic behavior of the hydroxymethyl groupPhotis Dais and R. H. MarchessaultCite this: Macromolecules 1991, 24, 16, 4611–4614Publication Date (Print):August 1, 1991Publication History Published online1 May 2002Published inissue 1 August 1991https://doi.org/10.1021/ma00016a021RIGHTS & PERMISSIONSArticle Views39Altmetric-Citations15LEARN 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 (431 KB) Get e-Alerts Get e-Alerts

Effect of internal librational motions on the carbon-13 nuclear magnetic resonance relaxation times of poly(.beta.-hydroxybutyrate) in tetrachloroethane solution

Effect of internal librational motions on the carbon-13 nuclear magnetic resonance relaxation times of poly(.beta.-hydroxybutyrate) in tetrachloroethane solution

Interpretation of the Carbon-13 Nuclear Magnetic Resonance Relaxation Time Data by the Computer-Assisted Method of Analysis: Application to Strychnine in Solution

Nuclear magnetic resonance relaxation times of carbons including quaternary ones have been measured for strychnine in CDCl3 at 11.74T. A computer-assisted method of analysis has been applied to interpret the data based on the three models of molecular reorientational motion. The contribution of dipole-dipole relaxation is estimated for the quaternary carbons in the method of analysis without invoking a separate time-consuming measurement of nuclear Overhauser effect factors; this enables us to discuss the mechanism of relaxation in these carbons. The dipolar part is dominant for the quaternary sp3 carbon, whereas contributions other than the Bipolar part are also significant for the quaternary sp2 carbons.

Dielectric, ultrasonic and carbon-13 nuclear magnetic resonance relaxation measurements of t-butyl alcohol–water mixtures

Dielectric, ultrasonic and 13C nuclear magnetic resonance relaxation measurements are reported on mixtures of t-butyl alcohol and water over the temperature range 278–308 K. Supporting measurements of the refractive index, density and viscosity are also presented. Deviations from ideal mixing behaviour are observed in the volumes of mixing, permittivities and adiabatic compressibilities of the mixtures. The location of the minima in the excess occurring at different compositions depend upon the method of measurement. Similarly the relaxation behaviour, as observed using different techniques, reveals different aspects of the motion of the molecules in the fluid. The various effects observed are rationalized in terms of a model in which it is assumed that t-butyl alcohol dimers and trimers and various hydrated forms play an important role in determining the structure of these mixtures.

Molecular Geometry Approximations for Chlorinated Dibenzodioxins by Fourier Transform Infrared Spectroscopy

Reference infrared vapor-phase spectra of 15 polychlorinated dibenzodioxin- p-dioxin (PCDD) isomers were recorded at low microgram concentrations. Ether linkage (COC) bond angles for these isomers and for the 22 tetrachlorodibenzodioxin (TCDD) isomers were calculated from infrared data, with the use of mass approximations for the terminal atom in a nonlinear XY2 model and by neglecting the valence force equation symmetric stretch bending term. Calculated bond angles show a good correlation with x-ray diffraction (XRD) and carbon-13 nuclear magnetic resonance (13C NMR) relaxation results. Molecular geometries in PCDD isomers, as defined by the COC bond angle and the COC stretching frequencies, were found to range from near planar, in laterally substituted isomers with high electron withdrawing capacity aromatic rings, to tetrahedral, for isomers with low electron withdrawing capacity rings. Non-bonded interactions were also found to influence molecular geometry. Molecular geometry was used to assign structures for the 1,2,3,6,7,8- and 1,2,3,7,8,9-hexachlorodibenzodioxin isomer mixture and was found to be an important factor in estimations of COC bond strength from empirical data. Correlations between infrared data and PCDD LD50 values suggest that molecular geometry, polarizability, and steric PCDD/receptor interactions are associated with isomer toxicity.

Notes. Carbon-13 and oxygen-17 nuclear magnetic resonance relaxation studies of [M3(CO)12] derivatives (M = Fe, Ru, or Os)

The combined use of 13C and 17O spin–lattice relaxation times for co-ordinated carbonyl ligands in [M3(CO)12] clusters (M = Fe, Ru, or Os) allows the determination of 17O quadrupolar coupling constants and the correlation times for molecular tumbling at different temperatures.

Structure and dynamics of porcine submaxillary mucin as determined by natural abundance carbon-13 NMR spectroscopy.

Nearly all of the resonances in the 13C NMR spectrum of porcine submaxillary mucin glycoprotein (PSM) have been assigned to the peptide core carbons and to the carbons in the eight different oligosaccharide side chains that arise from the incomplete biosynthesis of the sialylated A blood group pentasaccharide (alpha-GalNAc(1-3) [alpha-Fuc(1-2)]-beta-Gal(1-3) [alpha-NeuNGl(2-6)]- alpha-GalNAc-O-Ser/Thr). By use of these assignments, a nearly complete structural analysis of intact PSM has been performed without resorting to degradative chemical methods. Considerable structural variability in the carbohydrate side chains was observed between mucins obtained from different animals, while no variability was observed between glands in a single animal. The dynamics of the PSM core and carbohydrate side chains were examined by using the carbon-13 nuclear magnetic resonance relaxation times and nuclear Overhauser enhancements of each assigned carbon resonance. The peptide core of PSM exhibits internal segmental flexibility that is virtually identical with that of ovine submaxillary mucin (OSM), whose carbohydrate side chain consists of the alpha-NeuNAc(2-6)alpha-GalNAc disaccharide. The longer oligosaccharide side chains of PSM, therefore, have no significant effect on peptide core mobility compared to the shorter side chains of native OSM or asialo-OSM. Although the dynamics of the shorter carbohydrate side chains shared by both OSM and PSM appear to be identical, the A and H blood group structures in PSM have reduced mobilities, indicating that the glycosidic linkages of the terminal sugars in these determinants are relatively inflexible. These results differ from most reports of glycoprotein dynamics, which typically find the terminal carbohydrate residues to be undergoing rapid internal rotation about their terminal glycosidic bonds. The results reported here are consistent with previous studies on the conformations of the A and H determinants derived from model oligosaccharides and further indicate that the conformations of these determinants are unchanged when covalently bound to the mucin peptide core. In spite of their carbohydrate side-chain heterogeneity, mucins appear to be ideal glycoproteins for the study of O-linked oligosaccharide conformation and dynamics and for the study of the effects of glycosylation on polypeptide conformation and dynamics.

Nanosecond fluctuations of the molecular backbone of collagen in hard and soft tissues: a carbon-13 nuclear magnetic resonance relaxation study.

We have determined the amplitude of nanosecond fluctuations of the collagen azimuthal orientation in intact tissues and reconstituted fibers from an analysis of 13C NMR relaxation data. We have labeled intact rat calvaria and tibia collagen (mineralized and cross-linked), intact rat tail tendon and demineralized bone collagen (cross-linked), and reconstituted lathyritic (non-cross-linked) chick calvaria collagen with [2-13C]glycine. This label was chosen because one-third of the amino acid residues in collagen are glycine and because the 1H-13C dipolar coupling is the dominant relaxation mechanism. Spin-lattice relaxation times (T1) and nuclear Overhauser enhancements were measured at 15.09 and 62.98 MHz at 22 and -35 degrees C. The measured NMR parameters have been analyzed by using a dynamic model in which the azimuthal orientation of the molecule fluctuates as a consequence of reorientation about the axis of the triple helix. We have shown that if root mean square fluctuations in the azimuthal orientations are small, gamma rms much less than 1 rad, the correlation function decays with a single correlation time tau and T1 depends only upon tau and gamma rms and not the detailed model of motion. Our analysis shows that, at 22 degrees C, tau is in the 1-5-ns range for all samples and gamma rms is 10 degrees, 9 degrees, and 5.5 degrees for the non-cross-linked, cross-linked, and mineralized samples, respectively. At -35 degrees C, gamma rms is less than 3 degrees for all samples. These results show that mineral and low temperature significantly restrict the amplitude of nanosecond motions of the collagen backbone.(ABSTRACT TRUNCATED AT 250 WORDS)

High-resolution carbon-13 nuclear magnetic resonance spectrometry and relaxation behavior of organic solids from fossil fuels

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh-resolution carbon-13 nuclear magnetic resonance spectrometry and relaxation behavior of organic solids from fossil fuelsMichael A. Wilson, Anthony M. Vassallo, Philip J. Collin, and Horst. RottendorfCite this: Anal. Chem. 1984, 56, 3, 433–436Publication Date (Print):March 1, 1984Publication History Published online1 May 2002Published inissue 1 March 1984https://doi.org/10.1021/ac00267a031RIGHTS & PERMISSIONSArticle Views57Altmetric-Citations31LEARN 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 (524 KB) Get e-Alerts Get e-Alerts

A determination of the activation energy of cyclopentadienyl group rotation and molecular tumbling in [Fe(? 5-C5H5)(? 5-C5H4R)](R = CMe2Et or Bun) using carbon-13 nuclear magnetic resonance relaxation measurements

From variable-temperature 13C spin-lattice relaxation time and nuclear Overhauser enhancement measurements in [2H8]toluene solution at 25 and 100 MHz, the activation energies for ring rotation and molecular tumbling have been determined for n-butylferrocene and t-pentylferrocene.

ChemInform Abstract: CARBON‐13 NUCLEAR MAGNETIC RESONANCE RELAXATION IN MICROEMULSIONS. AGGREGATION IN THE EXTENSIVE SOLUTION PHASE OF THE SODIUM OCTANOATE‐OCTANOIC ACID‐WATE SYSTEM

Chemischer InformationsdienstVolume 14, Issue 25 Article ChemInform Abstract: CARBON-13 NUCLEAR MAGNETIC RESONANCE RELAXATION IN MICROEMULSIONS. AGGREGATION IN THE EXTENSIVE SOLUTION PHASE OF THE SODIUM OCTANOATE-OCTANOIC ACID-WATE SYSTEM T. + AHLNAES, T. + AHLNAESSearch for more papers by this authorO. + SOEDERMAN, O. + SOEDERMANSearch for more papers by this authorC. HJELM, C. HJELMSearch for more papers by this authorB. LINDMAN, B. LINDMANSearch for more papers by this author T. + AHLNAES, T. + AHLNAESSearch for more papers by this authorO. + SOEDERMAN, O. + SOEDERMANSearch for more papers by this authorC. HJELM, C. HJELMSearch for more papers by this authorB. LINDMAN, B. LINDMANSearch for more papers by this author First published: June 21, 1983 https://doi.org/10.1002/chin.198325070AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue25June 21, 1983 RelatedInformation

Carbon-13 nuclear magnetic resonance relaxation in microemulsions. Aggregation in the extensive solution phase of the sodium octanoate-octanoic acid-water system

Carbon-13 nuclear magnetic resonance relaxation in microemulsions. Aggregation in the extensive solution phase of the sodium octanoate-octanoic acid-water system

A carbon-13 nuclear magnetic resonance relaxation time study of streptoxotocin-deoxyguanosine-5′-monophosphate-deoxycytidine-5′-monophosphate interactions

We wish to report the observation of Watson-Crick base pairing between deoxyguanosine-5′-monophosphate (dGMP) and deoxycytidine-5′-monophosphate (dCMP), and the nature of the interaction of streptozotocin, an anticancer agent, with these mononucleotides, all in aqueous solution. Fourier transform carbon-13 ( 13C) nuclear magnetic resonance (nmr) relaxation time (T 1) measurements provided the evidence for complex formation. The dCMP 13C relaxation times are far more sensitive to the presence of dGMP rather than the antibiotic, whereas dGMP interacts strongly with both dCMP and streptozotocin. A description of these complexes and a correlation of these results with the observed clinical behavior of streptozotocin will be given.

An analysis of the β transition of linear and branched polyethylenes by carbon-13 NMR

Carbon-13 nuclear magnetic resonance relaxation parameters have been obtained as a function of temperature for a set of branched polyethylenes whose β transition temperatures were determined independently. Resolvable spectra could be obtained at temperatures either corresponding to or very close to the temperature of the β transition. Together with results for other systems, these observations preclude the indentification of the β transition with the glass temperature. From the measured spin relaxation times and nuclear Overhauser enhancements average correlation times were calculated as a function of temperature. The average correlation times were calculated as a function of temperature. The average correlation time is on the order of 10−8−10−9 s at the β transition. These results argue strongly against it being assigned to the glass temperature.

Carbon-13 nuclear magnetic resonance relaxation in crosslinked polystyrene gels

Carbon-13 nuclear magnetic resonance relaxation in crosslinked polystyrene gels

Carbon-13 nuclear magnetic resonance relaxation studies of internal mobility of the polypeptide chain in basic pancreatic trypsin inhibitor and a selectively reduced analogue.

Carbon-13 nuclear magnetic resonance relaxation studies of internal mobility of the polypeptide chain in basic pancreatic trypsin inhibitor and a selectively reduced analogue.

Conformational mobility of deoxyribonucleic acid, transfer ribonucleic acid, and poly(adenylic acid) as monitored by carbon-13 nuclear magnetic resonance relaxation.

The molecular motion of DNA, the native form of tRNA, and partially denatured poly(A) has been investigated by carbon-13 nuclear magnetic resonance (13C NMR). The nuclear Overhauser effect of the RNA samples was measured at 25.1 and 50.3 MHZ, and the spin-lattice relaxation time of all the samples was measured at 50.3 MHZ. The NMR data indicate that the local motion of the ribose carbons is much less restricted than that of the bases for DNA and tRNA. The local motion correlation times of the ribose carbons are in the range of 1-7 ns for the samples investigated. The local motion correlation times of the different nucleic acids are quite similar with the exception that the 2' carbon of DNA and poly(A) is apparently less restricted than that for tRNA. The local motion correlation times of the ribose carbons, except perhaps the 2', do not appear to be strongly coupled to the conformation of the polynucleotide. The 13C NMR results can be combined with those of other investigations to obtain a consistent picture of the internal and overall motions of polynucleotides which have a backbone that is much more flexible than that of the bases.