Carbon-13 Spin-lattice Relaxation Research Articles

Pharmacological, conformational and dynamic properties of cycloleucine-2 analogues of oxytocin and [1-penicillamine]oxytocin.

The solid phase syntheses of [2-cycloleucine] oxytocin and [1-penicillamine, 2-cycloleucine] oxytocin are reported. [1-Penicillamine, 2-cycloleucine] oxytocin is an oxytocin antagonist exhibiting no in vitro oxytocic activity. In the in vitro oxytocic assay, [1-penicillamine, 2-cycloleucine] oxytocin has a pA2 value of 6.70 +/- 0.08. [2-Cycloleucine]-oxytocin is a full oxytocin agonist exhibiting 4.9 +/- 0.5 U/mg of oxytocic activity. Neither compound possesses any measurable agonist or antagonist activity in the rat pressor assay. Carbon-13 nuclear magnetic resonance chemical shift parameters and spin-lattice relaxation times (T1) of the antagonist, [1-penicillamine, 2-cycloleucine] oxytocin, indicate that the antagonist exhibits similar conformational and dynamic properties as other oxytocin inhibitors previously studied. The carbon-13 nuclear magnetic resonance shift parameters and spin-lattice relaxation times (T1) of the oxytocin agonist, [2-cycloleucine] oxytocin, indicate that the agonist exhibits similar conformational and dynamic properties as oxytocin. These results are discussed in terms of the different receptor requirements for agonist and antagonist activities. It appears that there are different structural and conformational requirements at the 2-position for oxytocic agonist and antagonist activities.

13C nuclear magnetic resonance spin–lattice relaxation times and conformation of 2-chlorodibenzo-p-dioxine

The carbon-13 spin–lattice relaxation times for the hydrogen-bearing carbon atoms in 2-chlorodibenzo-p-dioxine have been measured for a saturated solution in DMSO + CD3CN (2 : 1) by the inversion–recovery–pulse sequence. The relaxation times were found to be in the range 4.2–6.3 s. Equations based on the extended relaxation equation of Huntress have been developed which allowed the calculation of relaxation times for 2-chlorodibenzo-p-dioxine under the assumption of a rigid model of anisotropic reorientation. These calculations, which were carried out for the conformations with angles of fold of 180, 164 and 150°, suggest that the experimental relaxation times are compatible with a planar (or almost planar) conformation with no internal ‘butterfly’ motion on the n.m.r. timescale. The method applied to 2-chlorodibenzo-p-dioxine may help to elucidate conformational dynamics.

Configuration dependence of carbon-13 spin-lattice relaxation times of poly(α-methylstyrene)

Carbon-13 n.m.r. spin-lattice relaxation times have been measured for atactic poly(α-methylstyrene) in 25% (w/v) solution in o-dichlorobenzene-d 4 as a function of temperature from 100° to 163°C and the results were compared with those for a syndiotactic poly(α-methylstyrene). It was concluded that the carbon-13 spin-lattice relaxation time is dependent on the stereochemical configuration over a relatively short range, but is not sensitive to longer range effects.

Hydrogen bonding in silica-bonded amino groups as probed by carbon-13 spin-lattice relaxation times

Carbon-13 spin-lattice relaxation data showed that internal mobility of silica-bonded amino groups became greater upon protonation, which suggests the motional restriction in the unprotonated state due to hydrogen bonding.

Molecular mobilities and the lowered osmolality of the chromaffin granule aqueous phase

Carbon-13 spin-lattice relaxation times, T 1, have been measured in whole adrenal medullary tissue slices, in suspensions of isolated chromaffin granules, in the reconcentrated chromaffin granule lysate, and in various model solutions containing catecholamines, ATP, chromogranins and Ca 2+. Reorientational correlation times have been calculated at 10°C using T 1 data and nuclear Overhauser enhancemments for protonated carbons on both catecholamines and nucleotides. Correlation times in all media are relatively short and characteristic of highly fluid aqueous phases. Adrenalin and ATP exhibit substantial differences in correlation times in all media, however, the ratio γ R(ATP):γ R(catecholamine) ranging from 2.4 in simple 3:1 adrenalin-ATP solutions to 4 in intact chromaffin granules. This difference, as well as the relatively high absolute reorientational mobilities of both components, confirms the importance of labile ionic interactions between ATP and catecholamines, but rules out the presence of high concentrations of base-stacked structures. Participation of the chromogranins in ternary complexes with catecholamines and ATP appears to be of minor importance. Ionic interactions to the protein are not reflected in either 13C T 1 values or chemical shifts of arginine or glutamate sidechain resonances, or in the 13C chemical shifts of ATP or catecholamines. Very labile protein-ATP binding appears to be reflected in the correlation time measurements, however, which show selective immobilization of ATP relative to catecholamine in the presence of soluble protein. Osmotic measurements indicate that solutions containing adrenaline, ATP and Ca 2+ are highly nonideal, but probably not sufficiently so to account fully for the osmotic stabilization of the chromaffin granule aqueous phase. Even in the absence of specific intermolecular complexation, the chromogranins, through their polyelectrolyte properties, exert a significant influence on the intragranular osmolality. The osmotic lowering due to polyion-counterion interactions has been estimated semiquantitatively using a theory developed by Oosawa.

Analytical13C NMR spectroscopy of fatty quaternary amines

AbstractNatural abundance13C nuclear magnetic resonance spectroscopy (CMR) has been used for the rapid, nondestructive analysis of fatty quaternary ammonium compounds. Quantitative analysis of mixtures of mono‐, di‐and tri‐fatty ammonium chlorides can be accommpublished under conditions that do not involve heat or extremes of pH and that are independent of solvent present. In order to determine optimal conditions for quantitative studies, carbon spin lattice relaxation times (T1) and nuclear Overhauser effects (NOE) were determined for each of the components. The method of internal standard addition was used to determine reproducibility and accuracy of the method for the measurement of mono‐and tri‐fatty quaternary components in material consisting predominantly (i.e., greater than 90%) of di‐fatty‐dimethyl ammonium chloride.

The effect of Torsional vibrations on carbon-13 spin-lattice relaxation times for methyl groups

The effect of Torsional vibrations on carbon-13 spin-lattice relaxation times for methyl groups

Carbon-13 NMR relaxation studies of pre-melt structural dynamics in [4-13C-uracil] labeled E. coli transfer RNAIVal.

We report 67.8 MHz carbon-13 spin-lattice relaxation studies on [4-13C-uracil] labeled tRNAIVal purified from E. coli SO-187. Following 13C-enriched C4 carbonyl resonances from modified and unsubstituted uridines scattered throughout the polymer backbone enables us to determine dynamical features in both loop and helical stem regions. The experimental results have been analyzed in terms of a model of isotropic overall molecular reorientation. "Anomalous" residues for which the experimental data cannot be accounted for in terms of the model provide an assessment of local and regional properties. Thus, "native" tRNAIVal under physiological conditions of magnesium (10 mM) and temperature (20 degrees - 40 degrees C), exhibits the following characteristics: 1) uridines held rigidly in helical stems and tertiary interactions display correlation times for rotational reorientation of 15-20 nsecs, typical for overall tRNA motion; 2) uridines in loops such as the wobble residue uridine-5-oxyacetic acid (V34) are quite accessible to solvent; moreover V34 and another loop residue, D17, exhibit local mobility; 3) the tertiary interactions involving 4-thio uridine (s4U8) and A14 and ribothymidine (rT54) and A58 are weakened as temperature increases.

Carbon-13 spin-lattice relaxation times of 16-membered macrolides: AR-5 (mycinamicins) antibiotics.

Carbon-13 spin-lattice relaxation times of 16-membered macrolides: AR-5 (mycinamicins) antibiotics.

ChemInform Abstract: BINDING OF MANGANESE(II) BY TETRACYCLINE. CARBON‐13 NMR SPIN‐LATTICE RELAXATION STUDY

Chemischer InformationsdienstVolume 12, Issue 49 Article ChemInform Abstract: BINDING OF MANGANESE(II) BY TETRACYCLINE. CARBON-13 NMR SPIN-LATTICE RELAXATION STUDY J. Y. LEE, J. Y. LEESearch for more papers by this authorG. W. JUN. EVERETT, G. W. JUN. EVERETTSearch for more papers by this author J. Y. LEE, J. Y. LEESearch for more papers by this authorG. W. JUN. EVERETT, G. W. JUN. EVERETTSearch for more papers by this author First published: December 8, 1981 https://doi.org/10.1002/chin.198149351AboutPDF 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. Volume12, Issue49December 8, 1981 RelatedInformation

Carbon-13 NMR and Raman Scattering Studies of Potassium Propoxybenzoate and Potassium Butoxybenzoate. Conformational Change Due to Micellization

Abstract Carbon-13 NMR chemical shifts and carbon-13 spin-lattice relaxation times of potassium propoxybenzoate and potassium butoxybenzoate in deuterium oxide solution were measured at various concentrations. For the alkoxy group, the earbon-13 resonance peak of the O-CH2 segment is shifted rapidly up-field upon micellization, while the resonance peaks of other methylene groups are shifted downfield. This observation is ascribed to the conformational change of the alkoxy group on micellization. In the monomolecular solution of potassium butoxybenzoate, the restricted state of the O-CH2 bond was estimated by carbon-13 spin-lattice relaxation time measurement. It was also found that micellization brings about a further restricted internal rotation about the O-CH2 bond.

A 13C NMR study of the solution dynamics of 1,3,5-triphenylbenzene; analysis of motion about the phenyl-phenyl bond

Carbon-13 spin-lattice relaxation rates were determined for 1,3,5-triphenylbenzene in CDCl 3 over a temperature range of 86°C, and the results interpreted in terms of the molecular dynamics. Dynamic models appropriate to the problem, including the effects of anisotropic motion and internal jumping between two or four states, were derived and the results evaluated comparatively for several different models. Similarities in the activation energies based on temperature-dependent measurements for all carbons suggests that either fortuitously similar barriers characterize both overall and internal motion, or that all relaxation rates depend primarily on a single type of motion, with the individual T 1 differences reflecting geometric factors. The latter interpretation leads to a rapid internal jump motion with a range of ∼60°, as would be predicted on the basis of theoretical conformational energy calculations. Application of a four-state jump model in which the jump rates are assumed to depend on the 0 and 90° theoretically determined rotational barriers allow an estimation of the rates of internal motion consistent with the relaxation data. The physical basis for complex terms which occur in the bistable (and tristable) jump models is discussed.

Effect of solvents on carbon-13 spin-lattice relaxation in 1-phenyladamantane

Rotational diffusion of 1-phenyladamantane was studied by means of carbon-13 spin-lattice relaxation. Seven different solvents were used. Rotational correlation times showed a linear dependence on solvent viscosity, except for chloroform and 1,1,2,2-tetrachloroethane which retarded motion of the phenyl moiety through specific interactions.

Molecular motion in liquid toluene and perfluorotoluene from carbon-13 spin-lattice relaxation measurements

Abstract Carbon-13 spin-lattice relaxation times and nuclear Overhauser enhancement factors are reported for neat toluene and octafluorotoluene at 301 K. A thorough analysis of the experimental data shows the overall reorientation of these molecules to be that of an axially symmetric ellipsoid, with diffusion coefficients D⊥ = 6.45 and and D// = 14.20 and respectively. The internal rotation of the attached methyl group is consistent with a 60° random jump model. The rotational barrier heights are of the same order of magnitude in both compounds : 5.1 and 6.1 kJ.mol−1, thus showing that the decreased mobility of the perfluoromethyl group in perfluorotoluene with respect to that of the methyl substituent in toluene should be traced to inertial and not to structural factors. The dipolar relaxation time of the substituted carbon atom C1 of toluene can be computed from these data and is shown to coincide with the experimental value within 4 % (349 and 363 s).

Studies on phenethylamine hallucinogens. 2. Conformations of arylmethoxyl groups using 13C NMR.

Carbon-13 chemical shift (delta) and spin-lattice relaxation time (T1) measurements were used to determine the conformation around the Ar-OCH3 bond of the arylmethoxyl groups in a series of substituted phenethylamines. Methoxyl groups flanked by two ortho substituents have delta 13C values higher (60.5-62.5 ppm) than those with one or no ortho substituents ((55.5-57.5 ppm) and T1 values considerably longer than those of the other methoxyl groups in the same molecule. These measurements indicate that methoxyl groups with two ortho substituents acquire the out-of-plane conformation, while those with one or no ortho substitutents exist in the planar conformation. Phenethylamine analogues with methoxyl groups in the out-of-plane conformation have low or no psychotomimetic activity. A possible explanation is that the out-of-plane methoxyl group interferes with the binding of the electron-rich methoxy-substituted aromatic ring to a corresponding electron-deficient component on the active site of the receptor.

Carbon-13 and nitrogen-15 spin-lattice relaxation studies of poly(vinylamine) and poly(iminoethylene)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbon-13 and nitrogen-15 spin-lattice relaxation studies of poly(vinylamine) and poly(iminoethylene)Peter L. Rinaldi, Chin Yu, and George C. LevyCite this: Macromolecules 1981, 14, 3, 551–554Publication Date (Print):May 1, 1981Publication History Published online1 May 2002Published inissue 1 May 1981https://doi.org/10.1021/ma50004a018RIGHTS & PERMISSIONSArticle Views82Altmetric-Citations16LEARN 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 (510 KB) Get e-Alerts Get e-Alerts

Formation and Molecular Dynamics of Cycloamylose Inclusion Complexes with Phenylalanine

Abstract The molecular dynamics of the inclusion complexes of cycloamyloses with phenylalanine in aqueous solution at different pD have been studied by means of carbon-13 NMR spectroscopy. As host cycloamyloses we have chosen cyclohexaamylose, cycloheptaamylose, and cyclooctaamylose. The influences of the cavity size of cycloamyloses and of medium pD values on the molecular dynamics of inclusion complexes were studied by using the NT1η values, where T1 is the carbon-13 spin-lattice relaxation time, N the number of directly bonded proton to a given carbon, and η is the viscosity of solution. Upon complexation, the NT1η values of phenyl carbons of guest phenylalanine show larger decreases than those of other carbons, indicating that the guest forms the inclusion complexes with the host by the insertion of its phenyl ring into the host cavity even in the case of cyclooctaamylose. It was found that the strength of the dynamic coupling between host and guest depends on the cavity size and pD values of medium. The strongest coupling was observed for the cycloheptaamylose–phenylalanine system at pD 11.3, where the phenyl ring is deeply and tightly included into the cavity. The inclusion of phenyl ring is shallow and loose in the case of cyclohexaamylose and deep and loose in the case of cyclooctaamylose.

Carbon-13 spin-lattice relaxation times and conformation of rosaramicin.

Carbon-13 spin-lattice relaxation times and conformation of rosaramicin.

Polybrominated oxydiphenol derivatives from the sponge dysidea herbacea: Structure determination by analysis of 13C spin-lattice relaxation data for quaternary carbons and 13C- 1H coupling constants

Five polybrominated oxydiphenol derivatives have been isolated from various Great Barrier Reef collections and one Fijian collection of the sponge Dysidea herbacea: 3,4',5,6,6'-hexabromo-2, 2'-oxydiphenol ( 11), 3,4',5,6,6'-pentabromo-2,2'-oxydiphenol ( 12), 3.4',5,6,6'-pentabromo-2,2'-oxydiphenol 1-methyl ether ( 13), 3,4,4',5,6'-pentabromo-2,2'-oxydiphenol 1,1'-dimethyl ether ( 14) and 3,4',5,6'-tetrabromo-2,2'-oxydiphenol 1'-methyl ether (15). The structure of the first member of this series is determined by a new method involving 13C spin-lattice relaxation data. The contributions of nearby hydrogens to quaternary carbon spin-lattice relaxation times are calculated for various possible structures and compared with the experimental data, leading to an unequivocal proof of structure. The structures of the remaining compounds in the series are established principally by analysis of 13C chemical shifts and 13C- 1H coupling constants.

Synthesis, pharmacological, conformational, and dynamic studies of the potent hormone antagonists [1-penicillamine, 4-threonine]-oxytocin and [1-penicillamine, 2-phenylalanine, 4-threonine]-oxytocin. Conformational and dynamic considerations in the design of antagonists.

The solid phase synthesis of [1-penicillamine, 4-threonine]-oxytocin and [1-penicillamine, 2-phenylalanine, 4-threonine]-oxytocin is reported. The two compounds have no in vitro milk ejecting activity and no in vivo or in vitro oxytocic activity, but both are potent antagonists in these three assay systems. In the in vitro oxytocic assay, [1-penicillamine, 4-threonine]- and [1-penicillamine, 2-phenylalanine, 4-threonine]-oxytocin have pA2 values of 7.55 +/- 0.04 and 7.67 +/- 0.02, respectively, and both inhibit the uterine contractile response to oxytocin in nonpregnant and pregnant rats. [1-Penicillamine, 2-phenylalanine, 4-threonine]-oxytocin has a weak antipressor activity and at high doses, consistently caused a weak and transient fall in blood pressure in the rat. Carbon-13 nuclear magnetic resonance chemical shift parameters and spin-lattice relaxation times (T1) indicate that these two new oxytocin antagonists have very similar conformation and dynamic properties to oxytocin inhibitors which have previously been examined. These results are discussed in terms of conformational and dynamic models of oxytocin antagonism at the uterus. It is suggested that conformational restrictions at the 2- and 4-positions of penicillamine-1 analogues of oxytocin are important to antagonist activity and potency.