High-field Proton Nuclear Magnetic Resonance Research Articles

Analysis of olive oil for authentication and shelf life determination.

High-field proton (1H) nuclear magnetic resonance (NMR) spectroscopy was applied for screening the fatty acyl contents of 33 olive oil samples from five different geographical regions of Turkey to do geographical discrimination analysis. The 1H NMR data were subjected to principal component analysis (PCA) and analysis of variance (ANOVA) to discriminate the origin of olive oils. The combination of discriminative screening by 1H NMR and ANOVA did not require further analysis of olive oil such as gas chromatography (GC). ANOVA was employed for samples from three regions separately: Marmara Region (MR), Aegean Region (AR), and Mediterranean Region (MeR). The best discriminative parameter was the 1H NMR signal of linoleoyl acyl content. Applying both quantitative NMR and statistical analysis indicated that samples from different provinces within each geographical region (MR, AR, and MeR) could be discriminated. Comparing the linoleoyl and oleoyl acyl contents of Turkish olive oils with these of some Mediterranean olive oils showed the possibility of distinguishing the Turkish olive oils. 1H NMR spectra of three olive oil samples with the production years of January 2013, January 2014, and January 2015 were acquired in 2016 for discussing shelf life of olive oil by quantifying fatty acyls content, and determining minor constituents and possible by-products during storage. The effects of altitude and soil quality on fatty acyl contents of olive oil samples from a small olive growing village in Northeastern Turkey were also tested.

A Conformational Study of Linkage Positions in Oligosaccharides Investigated by 2-D NMR Spectroscopy and Molecular Modeling

Eunsun Yoo Yoon School of Natural Science, Honam University, Gwangju 506-714, KoreaReceived November 12, 2002The conformation of synthetic oligosaccharide can be elucidated by employing molecular modeling and high-field proton NMR (nuclear magnetic resonance) spectroscopy. Information with respect to the composition andconfiguration of saccharide residues and the sequence and linkage positions of the oligosaccharide can beobtained by employing a variety of one- and two-dimensional NMR techniques and molecular modeling. Thesetechniques are also useful in establishing the solution conformation of the oligosaccharide moiety. This studyis focused on the elucidation of linkage positions of synthetic trisaccharides, Gal(β1-4)Glc(β1-3)Glc, Gal(β1-4)Glc(β1-4)Glc and Gal(β1-4)Glc(β1-6)Glc.Key Words : Linkage, Oligosaccharide, Conformation, 2-D NMR, Molecular modelingIntroductionThe growing interest in the biological function of oligo-saccharides has stimulated the constant search for newmethods for analyzing their primary and secondary structures.

1H-NMR lipid profiles of human blood platelets; links with coronary artery disease

Blood platelets are closely involved in the early development of atherosclerosis and in the events that lead to thrombosis, both of which are dominating factors in coronary artery disease (CAD). The aim of the present study was to evaluate the platelet lipid profiles of patients suffering from CAD and explore the possibility of a link between platelet lipids and CAD, using high-resolution high-field proton nuclear magnetic resonance spectroscopy as the analytical tool. The total platelet lipid profiles of healthy volunteers were compared with those of patients presenting with chest pain requiring coronary angiography. Two lipid groups changed significantly: cholesterol increased by 16.5% and total diacylglycerophospholipids decreased by 15.7%. There was also a significant decrease of the ethanolamine-containing phospholipids, by 4.7%; the extent of unsaturation of the fatty acid chains, by 0.2, and increase of the linoleate content of the fatty acid chains, by 1.9%. Our results suggest that platelet lipid abnormalities occur in patients with CAD and these changes may predate the development of overt atherosclerosis.

Determination of biophysical parameters of polypeptide retro-inverso isomers and their analogues by capillary electrophoresis.

The relationship between the electrophoretic mobility, microobs, Stokes radius, rs, ionization state, and solution conformation of the all L-alpha-polypeptide, 1, the corresponding retro-all D-alpha-polypeptide, 2, and several truncated analogues, 3-5, has been investigated under low pH buffer conditions by high-performance capillary zonal electrophoresis (HPCZE) with coated capillaries. The results confirm that, under these conditions, the all L-alpha-polypeptide, 1, and its retro-inverso isomer, 2, exhibit nonidentical electrophoretic mobilities and thus different Stokes radii. At higher pH values, i.e., pH 5.0, the electrophoretic behavior of this retro-inverso isomer pair, however, converges. These results indicate that variations in the dipole characteristics of the polypeptide main chain and subtle differences introduced by the spatial constraints of the L-alpha-Pro-->D-alpha-Pro residue replacement lead to differences in the Stokes radii and electrophoretic mobilities of these polypeptides. Since the observed electrophoretic mobilities, microobs, reflect the mean of the mobilities of each charge species participating according to their Stokes radius or their intrinsic charge and mole fraction abundances, the results confirm that polypeptide retro-inverso isomers with unmodified amino and carboxy termini are resolvable. This outcome was achieved despite their notional topographical and conformational similarities as assessed from high-field proton nuclear magnetic resonance (1H NMR) spectroscopy and circular dichroism (CD) spectroscopy.

Synthesis and characterization of polycyclic aromatic hydrocarbon o-quinone depurinating N7-guanine adducts.

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants which may cause cancer and require metabolic activation to exert their carcinogenic effects. One pathway of activation involves the dihydrodiol dehydrogenase-catalyzed oxidation of non-K region trans-dihydrodiols to yield catechols, which autoxidize to form reactive o-quinones. As a step toward identifying the spectrum of PAH o-quinone-DNA adducts that may form in biological systems, depurinating PAH o-quinone-guanine adducts were synthesized. Naphthalene-1,2-dione, phenanthrene-1,2-dione, and benzo[a]pyrene-7, 8-dione were reacted with 5 equiv of 2'-deoxyguanosine (dGuo) under acidic conditions (1:1 acetic acid/water). The products were purified by reversed-phase HPLC, characterized by a combination of UV spectroscopy, electrospray ionization/tandem mass spectrometry, and high-field proton nuclear magnetic resonance spectroscopy, and identified as 7-(naphthalene-1,2-dion-4-yl)guanine (MH+, m/z 308), 7-(phenanthrene-1,2-dion-4-yl)guanine (MH+, m/z 358), and 7-(benzo[a]pyrene-7,8-dion-10-yl)guanine (MH+, m/z 432), respectively. Reaction at N7 of dGuo leads to cleavage of the glycosidic bond, producing depurinating adducts. Reaction of phenanthrene-1,2-dione with calf thymus DNA led to the formation of the corresponding depurinating adduct. The loss of modified bases in DNA generates apurinic sites which, if unrepaired, can lead to mutations and thus cellular transformation. These synthesized PAH o-quinone-N7-guanine adducts can be used as standards to identify such adducts in vitro and in vivo.

NMR microscopy of trabecular bone and its role in skeletal dosimetry.

One of the more intractable problems in internal dosimetry is the assessment of energy deposition by alpha and beta particles within trabecular, or cancellous, bone. In the past few years, new technologies have emerged that allow for the direct and nondestructive 3D imaging of trabecular bone with sufficient spatial resolution to characterize trabecular bone structure in a manner needed for radiation dosimetry models. High-field proton nuclear magnetic resonance (NMR) imaging is one such technology. NMR is an ideal modality for imaging trabecular bone due to the sharp contrast in proton density between the bone matrix and bone marrow regions. In this study, images of the trabecular regions within the bodies of a human thoracic vertebra have been obtained at a field strength of 14.1 T. These images were digitally processed to measure chord length distribution data through both the bone trabeculae and marrow cavities. These distributions, which were found to be qualitatively consistent with those measured by F. W. Spiers and colleagues at the University of Leeds using physical sectioning and automated light microscopy, yielded a mean trabecular thickness of 201 microm and a mean marrow cavity thickness of 998 microm. The NMR techniques developed here for vertebral imaging may be extended to other skeletal sites, allowing for improved site-specific skeletal dosimetry.

Characterization of Italian Extra Virgin Olive Oils Using 1H-NMR Spectroscopy

High-field (600-MHz) proton nuclear magnetic resonance (1H-NMR) spectroscopy was applied to the analysis of 55 extra virgin olive oil samples from four Italian regions (Campania, Lazio, Sicily, and Umbria) and obtained from diffrent olive varieties. The multivariate statistical analysis (PCA, hierarchical clustering) performed on the normalized intensities of 1H- NMR resonances due to minor components (β-sitosterol, n-alkenals, trans-2-alkenals, and other volatile compounds) allows a good classification of oil samples obtained from traditional varieties with respect to the region of origin (96% of oils correctly classified). Samples obtained from one new experimental cultivar (FS-17) were not correctly classified, indicating a strong contribution of olive variety on the chemical composition of virgin olive oils. The potential contribution and limits of NMR in the authentication of virgin olive oil geographical origin and variety are discussed. Keywords: Proton NMR spectroscopy; virgin olive oil; hierarchi...

Analysis of nitrophenols and other polar nitroaromatic compounds in ammunition wastewater by high-field proton nuclear magnetic resonance (1H-NMR) spectroscopy and chromatographic methods

It is shown that by using high-field proton nuclear magnetic resonance (1H-NMR) spectroscopy it is possible, without prior separation, to analyse nitrophenols and other acidic nitroaromatic compounds in the “pH 2 extract” of ammunition wastewater. The 1H-NMR chemical shifts data of a variety of reference compounds are presented. Two groundwater samples from the former ammunition plant in Elsnig (Saxony) were analysed by 1H-NMR and also by chromatographic methods (GC/MS, HPLC). The results are compared and discussed.

Application of high-field proton nuclear magnetic resonance ((1)H-NMR) spectroscopy for the analysis of explosives and related compounds in groundwater samples - a comparison with the high-performance liquid chromatography (HPLC) method.

High-field proton nuclear magnetic resonance ((1)H-NMR) spectroscopy was applied to the analysis of nitroaromatics and nitramines in ammunition waste water. The (1)H-chemical shifts data of a variety of reference compounds are presented. Three groundwater samples, taken near the former ammunition plant Elsnig (Saxony), were analysed by high-performance liquid chromatography (HPLC) and by proton nuclear magnetic resonance spectroscopy. The results of HPLC and NMR analyses are compared and discussed.

Quantitative analysis of trabecular microstructure by 400 MHz nuclear magnetic resonance imaging

A new approach for the quantitative analysis of trabecular microstructure, based on high-field proton nuclear magnetic resonance (NMR) imaging, is presented. NMR is ideal because it provides high contrast between the marrow proton signal and the bone, which appears with background intensity. Images from 1 cm3 defatted specimens of trabecular bone, suspended in water doped with 1 mM Gd(DTPA) to shorten T1 to about 300 ms, can be obtained at a resolution on the order of 30-50 microns and slice thickness of 150 microns, in 10 minutes at 400 MHz proton frequency. Digital image processing algorithms were designed and evaluated for the measurement of bone area fraction, perimeter length, mean trabecular thickness, and separation. Bone area fraction derived from the NMR images was found to be in excellent agreement with bone volume fraction measured independently (slope = 0.96, r2 = 0.924, p < 0.0001). Errors in the mean trabecular thickness and separation were < 6%. The effects of finite imaging slice thickness and signal-to-noise ratio (SNR) were also evaluated. The data suggest a resolution of 50 x 50 x 200 microns 3 and an SNR on the order of 10 to provide safe margins for precise and accurate structural analysis by means of the algorithms presented in this paper. The method allows simultaneous measurement at multiple locations within the specimen volume without the need for physical sectioning.

Multicomponent analysis of radiolytic products in human body fluids using high field proton nuclear magnetic resonance (NMR) spectroscopy

High field proton Hahn spin-echo nuclear magnetic resonance (NMR) spectroscopy has been employed to investigate radiolytic damage to biomolecules present in intact human body fluids. γ-Radiolysis of healthy or rheumatoid human serum (5.00 kGy) in the presence of atmospheric O 2 gave rise to reproducible elevations in the concentration of NMR-detectable acetate which are predominantly ascribable to the prior oxidation of lactate to pyruvate by hydroxyl radical (·OH) followed by oxidative decarboxylation of pyruvate by radiolytically-generated hydrogen peroxide (H 2O 2) and/or further ·OH radical. Increases in the serum levels of non-protein-bound, low-molecular-mass components such as citrate and glutamine were also observed subsequent to γ-radiolysis, an observation which may reflect their mobilisation from protein binding-sites by ·OH radical, superoxide anion and/or H 2O 2. Moreover, substantial radiolytically-mediated elevations in the concentration of serum formate were also detectable. In addition to the above modifications, γ-radiolysis of inflammatory knee-joint synovial fluid (SF) generated a low-molecular-mass oligosaccharide species derived from the radiolytic fragmentation of hyaluronate. The radiolytically-mediated production of acetate in SF samples was markedly greater than that observed in serum samples, a consequence of the much higher levels of ·OH radical-scavenging lactate present. Indeed, increases in SF acetate concentration were detectable at doses as low as 48 Gy. We conclude that high field proton NMR analysis provides much useful information regarding the relative radioprotectant abilities of endogenous components and the nature, status and levels of radiolytic products generated in intact biofluids. We also suggest that NMR-detectable radiolytic products with associated toxicological properties (e.g. formate) may play a role in contributing to the deleterious effects observed following exposure of living organisms to sources of ionising radiation.

Generation of substance P carbamate in neutral aqueous solution: Relevance to inflammatory joint diseases

High-field proton ( 1H) nuclear magnetic resonance (NMR) spectroscopy has been employed to evaluate the formation of substance P carbamate in aqueous solution. Equilibration of substance P with physiologically relevant concentrations of bicarbonate (2.50 × 10 −2 mol·dm −3) at pH 7.00 generated a new multiplet signal centred at 4.13 ppm in its NMR spectrum, characteristic of the α-proton of peptide carbamate species. High-field 1H NMR spectroscopy also demonstrated that the model dipeptide, Arg-Gly, formed a carbamate in neutral aqueous solutions containing 2.50 × 10 −2 mol·dm −3 HCO 3. The physiological significance of these results is discussed in view of the central roles of vasoactive neuropeptides in human joint diseases and the hypercapnic environment of the inflamed rheumatoid joint.

High-performance liquid chromatography coupled to high-field proton nuclear magnetic resonance spectroscopy: application to the urinary metabolites of ibuprofen

The use of coupled reversed-phase high-performance liquid chromatography and high-field proton nuclear magnetic resonance spectroscopy (HPLC-NMR) for the detection and identification of the urinary metabolites of ibuprofen is described. Urine was obtained from a healthy human volunteer following a normal therapeutic dose of 400 mg of ibuprofen. Analysis was performed on both a freeze-dried urine concentrate and partially purified extracts obtained by solid-phase extraction onto C-18 bonded silica gel. Both continuous and stop-flow methods were used to obtain spectra enabling the major urinary metabolites of ibuprofen to be detected and identified.

High field proton NMR investigations of the metabolic profiles of multidrug-sensitive and -resistant leukaemic cell lines: evidence for diminished taurine levels in multidrug-resistant cells.

High field proton (1H) nuclear magnetic resonance (NMR) spectroscopy has for the first time been employed to investigate and compare the metabolic profiles of vinblastine-sensitive and -resistant T-lymphoid leukaemic cell lines (CCRF-CEM and CEM/VLB100 respectively) and evidence is presented for a significantly lower taurine content in the CEM/VLB100 resistant subline when expressed relative to that of its drug-sensitive parental counterpart. These data suggest differences in the nature and relative involvements of taurine biosynthetic pathways between the two cell lines, a phenomenon that may be related to their differing sensitivities towards chemotherapeutic agents such as adriamycin which promote the generation of cytotoxic reactive oxygen species (ROS) in vivo. However, the 1H NMR data obtained provided no evidence for an increased metabolic consumption of hypotaurine (a metabolic precursor of taurine with powerful .OH radical scavenging properties) in CCRF-CEM cells since differences observed in the hypotaurine: taurine concentration ratio between the drug-sensitive and -resistant cell lines were not statistically significant. Furthermore, hypotaurine is unlikely to compete with alternative endogenous .OH radical scavengers present such as lactate since its level in either of the two cell lines investigated (ca. 6.0 x 10(-8) mol./10(8) cells) is insufficient for it to act as an antioxidant in this context. The biochemical and therapeutic significance of these results are discussed.

Appearance of Aminorex as a Designer Analog of Methylaminorex

Abstract A case in which aminorex (cis ± 4,5-dihydro-5-phenyl-2-oxazolamine) was prepared as a “designer” analog of a controlled substance, methylaminorex (cis ± 4,5-dihydro-4-methyl-5-phenyl-2-oxazolamine) is described. The confiscated drug sample was analyzed by high-field (300-mHz) proton nuclear magnetic resonance (NMR) and carbon-13 NMR spectroscopy, as well as electron impact mass spectrometry (70 eV). These examinations proved conclusively that the material in question was aminorex.

1H-NMR studies of synthetic peptide analogues of calcium-binding site III of rabbit skeletal troponin C: effect on the lanthanum affinity of the interchange of aspartic acid and asparagine residues at the metal ion coordinating positions.

The present work determines the contribution of liganding aspartic acid (Asp) residues, at the +X, +Y, and +Z metal ion coordinating positions, to the lanthanum(3+) (La3+) ion binding affinity of synthetic analogues of calcium-binding site III of rabbit skeletal troponin C. Eight 13-residue synthetic analogues were prepared by solid-phase synthesis; the primary sequences of these analogues represent all possible combinations having aspartic acid and asparagine at the +X, +Y, and +Z positions. High-field proton nuclear magnetic resonance (NMR) spectroscopy was used to monitor the binding of the La3+ ion to each of the analogues. Comparison of the chemical shift changes showed large variations in the magnitude of the shift; these were reflected in the La3+ ion association constants determined for each analogue. The association constants ranged from 9.1 x 10(2) M-1 to 2.5 x 10(5) M-1. It was observed that those analogues with the larger number of acidic residues to coordinate the La3+ ion yielded the higher association constants. The La3+ ion binding results demonstrate that the Asp residues at the positions of study contribute equally and in an additive manner to the association constant and that the presence of neighboring Asp residues at either the +X and +Y, the +Y and +Z, or the +X and +Y and +Z metal ion coordinating positions introduced dentate-dentate repulsion, which, acts as to detract from the La3+ ion association constant of the analogues.

Glucuronidation of 6 alpha-hydroxy bile acids by human liver microsomes.

The glucuronidation of 6-hydroxylated bile acids by human liver microsomes has been studied in vitro; for comparison, several major bile acids lacking a 6-hydroxyl group were also investigated. Glucuronidation rates for 6 alpha-hydroxylated bile acids were 10-20 times higher than those of substrates lacking a hydroxyl group in position 6. The highest rates measured were for hyodeoxy- and hyocholic acids, and kinetic analyses were carried out using these substrates. Rigorous product identification by high-field proton nuclear magnetic resonance and by electron impact mass spectrometry of methyl ester/peracetate derivatives revealed that 6-O-beta-D-glucuronides were the exclusive products formed in these enzymatic reactions. These results, together with literature data, indicate that 6 alpha-hydroxylation followed by 6-O-glucuronidation constitutes an alternative route of excretion of toxic hydrophobic bile acids.

Schmidt reaction on camphor. Part I. Structure of the products

A reinvestigation of the major product from the Schmidt reaction on camphor has led to the assignment of the structure as 1,9,9-trimethyl-3-oxo-2,8-diazabicyclo[3.3.1]nonane (5). The structure has been established by high-field proton and carbon-13 nuclear magnetic resonance, as well as degradation to the imine ester 4. Confirmation of the structure of 5 was achieved by X-ray crystallography. Compound 5, C10H18N2O, crystallized in space group P21/a with a = 14.934(1) Å, b = 10.973(1) Å, c = 12.341(1) Å, β = 92.0°, and Z = 8. The relatively rare cis amide linkage is present in the molecule. In addition to the amino amide 5, the Schmidt reaction on camphor leads to small amounts of the tetrazole 8 and the imine nitrile 9.

Elucidation of glycolipid structure by proton nuclear magnetic resonance spectroscopy

The primary structure of the oligosaccharide moiety of a glycosphingolipid can be elucidated by employing high-field proton nuclear magnetic resonance (NMR) spectroscopy. Information with respect to the composition and configuration of its sugar residues, and the sequence and linkage sites of the oligosaccharide chain can be obtained by employing a variety of one- and two-dimensional techniques. The latter include both scalar and dipolar correlated two-dimensional NMR spectroscopy. These techniques are also useful in establishing the solution conformation (secondary structure) of the oligosaccharide moiety. Examples in utilizing these techniques in elucidating the primary and secondary structures of glycolipids are presented.

High-field proton and carbon-13 nuclear magnetic resonance studies of the conformational dynamic properties of seven-membered rings. 1,5-Benzodithiepin and 3-substituted derivatives

The conformational and dynamic properties of 1,5-benzodithiepin (1), its 3,3-dimethyl (2), 3-methyl (3), and 3-methoxy (4) derivatives have been investigated by high-field 1H and 13C dynamic nuclear magnetic resonance methods. Analyses of the spectra at low temperatures indicate that, in CS2, both 1 and 2 exist as a mixture of C and TB forms (97:3 for 1; 63:37 for 2). In contrast, both 3 and 4 exist as a mixture of three equilibrating conformations Ce, Ca, and TB in ratios of 55:25:20 and 88:8:4 respectively. Comparison with analogues derived from 1,5-benzodioxepins (1a–4a) indicates that the replacement of O by S decreases the amount of the TB form for all four compounds studied. The observation that Ce is the most abundant form for 4 while it is not observed for 4a can be explained by a repulsive S/O gauche interaction in 4 compared to an attractive O/O interaction in 4a.