High-resolution 1H NMR Spectroscopy Research Articles

Metabolomic studies on the biochemical profile of urine from rats with acute cysteamine supplementation

This study investigates the effect of acute cysteamine (CS) supplementation on rat metabolism. A metabolomic strategy using high-resolution 1H-NMR spectroscopy in conjunction with principal component analysis was applied to examine rat biological responses to CS administration. Half of female Sprague–Dawley rats (2 groups of 6 rats) were each given doses of 150 mg CS/kg body weight intraperitoneally. Urine samples were collected twice daily (0–8 and 8–24 h) from the rats following CS administration. The identifiable biochemical effects associated with CS supplementation included decreased urinary concentrations of hippurate, succinate, citric acid, and 2-oxoglutarate, as well as increased urinary concentrations of dimethylamine, dimethylglycine, glycine, and taurine. These effects were predominately seen within the first 8 h after CS administration. Clear differences in succinate, citric acid, and 2-oxoglutarate were observed 8–24 h following CS. The results suggest that CS supplementation in the rats resulted in modulation of intestinal microbial metabolism and metabolic perturbation of the tricarboxylic acid cycle.

Toward the Self-Assembly of Metal−Organic Nanotubes Using Metal−Metal and π-Stacking Interactions: Bis(pyridylethynyl) Silver(I) Metallo-macrocycles and Coordination Polymers

Shape-persistent macrocycles and planar organometallic complexes are beginning to show considerable promise as building blocks for the self-assembly of a variety of supramolecular materials including nanofibers, nanowires, and liquid crystals. Here we report the synthesis and characterization of a family of planar di- and tri-silver(I) containing metallo-macrocycles designed to self-assemble into novel metal-organic nanotubes through a combination of π-stacking and metal-metal interactions. The silver(I) complexes have been fully characterized by elemental analysis, high resolution electrospray ionization mass spectrometry (HR-ESI-MS), IR, (1)H and (13)C NMR spectroscopy, and the solution data are consistent with the formation of the metallo-macrocycles. Four of the complexes have been structurally characterized using X-ray crystallography. However, only the di-silver(I) complex formed with 1,3-bis(pyridin-3-ylethynyl)benzene is found to maintain its macrocyclic structure in the solid state. The di-silver(I) shape-persistent macrocycle assembles into a nanoporous chicken-wire like structure, and ClO(4)(-) anions and disordered H(2)O molecules fill the pores. The silver(I) complexes of 2,6-bis(pyridin-3-ylethynyl)pyridine and 1,4-di(3-pyridyl)buta-1,3-diyne ring-open and crystallize as non-porous coordination polymers.

Metabolic insights into the yeast response to propionic acid based on high resolution 1H NMR spectroscopy

The experimental model Saccharomyces cerevisiae has been widely used to elucidate the molecular mechanisms behind resistance to weak acids in fungi, an essential knowledge for the development of more suitable preservation strategies. Previous studies, based on transcriptomic and chemogenomic approaches, revealed a number of yeast responses to propionic acid, widely used in the preservation of bakery and fresh dairy products. In the present work we report the metabolic changes occurring during yeast adaptation to, and growth in, the presence of this weak acid (20 mM at pH 4) using high resolution 1H NMR spectroscopy coupled with multivariate statistical analysis. The metabolic profiles highlighted the separation of propionic acid-induced lag-phase in two parts. The initial period of incubation under acid stress (up to 3 h following the inoculation of an unadapted yeast population) was characterized by a decrease of cell viability and of the average intracellular pH (pHi) values. The final part of this incubation period (from 4 to 6 h of incubation) was characterized by the start of cell division in the presence of the acid, an increase of the average pHi and a metabolic profile close to the profile exhibited by cells in the exponential phase of growth in propionic acid supplemented medium. An association between the average pHi values and the levels of glutamate and propionate during growth latency was identified. Changes in the cell content in other amino acids, ATP, NAD+, glycerol and trehalose were also registered during yeast incubation with propionic acid. These alterations are discussed in the context of the global response to this weak acid.

Erratum to: Determination of the ionization constants of natural cyclodextrins by high-resolution 1H-NMR and photon correlation spectroscopy

The purpose of this investigation has been to establish reference pKa values in D2O for the three natural CDs by high-resolution 1H-NMR, according to the recent guidelines provided by the IUPAC for the determination of extreme pKa values. The most alkaline conditions achieved in this study than in previous pH potentiometric assays have made possible to deduce the pKa for the three acidic groups of each CD. In addition, we have studied the effects of the ionization of β-CD on the aggregation properties of this macrocycle in H2O by dynamic light scattering (DLS) as a function of pH. This procedure provides an indirect way of measuring the pKa of β-CD either by tracking the percentage of scattered light or the hydrodynamic radii of the species involved and reveals that the aggregates of β-CD break and reduce their size progressively upon ionization of the OH− groups in positions 2 and 3.

1H NMR-based metabonomic investigation of tributyl phosphate exposure in rats

Tributyl phosphate (TBP) is a toxic organophosphorous compound widely used in many industrial applications, including significant usage in nuclear processing. The industrial application of this chemical is responsible for occupational exposure and environmental pollution. In this study, 1H NMR-based metabonomics has been applied to investigate the metabolic response to TBP exposure. Male Sprague-Dawley rats were given a TBP-dose of 15 mg/kg body weight, followed by 24 h urine collection, as was previously demonstrated for finding most of the intermediates of TBP. High-resolution 1H NMR spectroscopy of urine samples in conjunction with statistical pattern recognition and compound identification allowed for the metabolic changes associated with TBP treatment to be identified. Discerning NMR spectral regions corresponding to three TBP metabolites, dibutyl phosphate (DBP), N-acetyl-(S-3-hydroxybutyl)- l-cysteine and N-acetyl-(S-3-oxobutyl)- l-cysteine, were identified in TBP-treated rats. In addition, the 1H NMR spectra revealed TBP-induced variations of endogenous urinary metabolites including benzoate, urea, and trigonelline along with metabolites involved in the Krebs cycle including citrate, cis-aconitate, trans-aconitate, 2-oxoglutarate, succinate, and fumarate. These findings indicate that TBP induces a disturbance to the Krebs cycle energy metabolism and provides a biomarker signature of TBP exposure. We show that three metabolites of TBP, dibutylphosphate, N-acetyl-(S-3-hydroxybutyl)- l-cysteine and N-acetyl-(S-3-oxobutyl)- l-cysteine, which are not present in the control groups, are the most important factors in separating the TBP and control groups ( p < 0.0023), while the endogenous compounds 2-oxoglutarate, benzoate, fumarate, trigonelline, and cis-aconetate were also important ( p < 0.01).

Metabolic profiling of lymph from pigs fed with β-glucan by high-resolution 1H NMR spectroscopy

To gain information about the effect of ingesting different β-glucan sources on intestinal lymph metabolic profile, 10 growing pigs (30–36 kg) were fitted with a catheter in the jejunal lymphatic trunk, and lymph samples collected continuously -1 to 8 h postprandial and again at 24 h after feeding a diet containing either 0.4% added yeast or barley β-glucan and compared to a Control diet. The lymph samples were analysed by proton nuclear magnetic resonance ( 1H NMR) spectroscopy and subsequently subjected to chemometric analysis. The dominant resonances in the 1H NMR spectra of lymph arose primarily from fatty acids and the glycerol backbone in triglycerides. Weak signals from carbohydrates and aromatic compounds were also observed. The chemometric analysis demonstrated that the levels of mono- and poly-unsaturated lipids were reduced by the β-glucan enriched diets. Furthermore, indications of increased lymph viscosity induced by barley β-glucan compared to yeast β-glucan were observed.

ChemInform Abstract: High-Resolution Solid-State NMR Spectroscopy in Studies of Conversions of Hydrocarbons and Alcohols on Zeolites

The review surveys advances in high-resolution solid-state 1H and 13C NMR spectroscopy applied to studies of conversions of hydrocarbons and alcohols on zeolite catalysts of an acidic nature. The potential of NMR spectroscopy in studies of mechanisms of chemical reactions and analysis of compounds formed in situ is considered. The bibliography includes 134 references.

Structural Determination of Extem XH 1015 and Its Gas Permeability Comparison with Polysulfone and Ultem via Molecular Simulation

By employing high resolution 1H and 13C NMR spectroscopy combined with elemental analysis and FTIR-ATR, we have determined the basic chemical structure of Extem XH 1015, a new brand of polyetherimi...

Determination of the ionization constants of natural cyclodextrins by high-resolution 1H-NMR and photon correlation spectroscopy

Determination of the ionization constants of natural cyclodextrins by high-resolution 1H-NMR and photon correlation spectroscopy

Deletion of btn1, an orthologue of CLN3, increases glycolysis and perturbs amino acid metabolism in the fission yeast model of Batten disease

The neuronal ceroid lipofuscinoses (NCLs) constitute a group of autosomal recessive neurodegenerative diseases affecting children. To date, the disease pathogenesis remains unknown, although the role of lysosomal impairment is widely recognized across the different diseases. Recently, the creation of simple models of juvenile NCL (Batten disease) has provided additional insights into the disease mechanism at the molecular level. We report defects in metabolism identified in the Schizosacchromyces pombe yeast model, where btn1, the orthologue of CLN3, has been deleted, using a metabolomics approach based on high resolution 1H and 13C NMR spectroscopy. Such changes represent the first documented metabolic changes associated with deletion of btn1. A decrease in extracellular glucose and increases in the concentration of extracellular ethanol and alanine labelling demonstrate increased glycolytic flux that may arise from vacuolar impairment, whilst amino acid changes were detected which were also in accordance with defective vacuolar functionality. That these changes were detected using a metabolomic based approach advocates its use to further analyse other yeast models of human disease to better understand the function of orthologue genes.

High-Resolution Solid-State NMR Investigation of the Phase Transition in Decamethylferrocene−Acenaphthenequinone Charge-Transfer Complex

A charge-transfer complex composed of decamethylferrocene (D) and acenaphthenequinone (A) was prepared. The material was a 1:1 neutral complex with a mixed-stack structure and exhibited a phase transition at -16 degrees C. High-resolution (13)C and (1)H NMR spectroscopy revealed that an inclination of A with respect to D occurs below the phase-transition temperature. The (1)H spin-diffusion rates of the complex undergoing high-speed magic-angle spinning (MAS) were measured to determine the shortest (1)H-(1)H distance r between D and A. To analyze the experimental results, we derived the analytical expression of the spin-diffusion rate W(z) for a homonuclear multispin system undergoing MAS. It was found that W(z) for the complex is proportional only to 1/r(6) under high-speed MAS conditions. On the basis of this relationship and the crystal structure at 20 degrees C, it was determined that the shortest (1)H-(1)H distance r at -27.7 degrees C (below the phase transition temperature) is 0.4 A shorter than that at 20 degrees C. Given this information, a plausible model of the low-temperature structure is discussed.

Nanoparticle Size Determination by 1H NMR Spectroscopy

High-resolution solution (1)H NMR spectroscopy has been used to characterize the size of Pd dendrimer-encapsulated nanoparticles (DENs). The Pd nanoparticles measured by this technique contain 55, 147, 200, or 250 atoms, and they are encapsulated within sixth-generation, hydroxyl-terminated poly(amidoamine) PAMAM dendrimers (G6-OH). Detailed analysis of the NMR data shows that signals arising from the innermost protons of G6-OH(Pd(n)) decrease significantly as the size of the encapsulated nanoparticles increase. A mathematical correlation between this decrease in the integral value and the theoretical number of Pd atoms in the nanoparticle is extracted. It enables the elucidation of the size of Pd DENs by (1)H NMR spectroscopy. NMR pulse-field gradient spin-echo experiments demonstrate that G6-OH with and without DENs have identical hydrodynamic radii, which excludes the presence of dendrimer/nanoparticle aggregates.

PRESS echo time behavior of triglyceride resonances at 1.5 T: Detecting ω-3 fatty acids in adipose tissue in vivo

Aim This study investigated the impact of fatty acid (FA) composition on the echo time behavior of triglyceride resonances in a clinical setting. The feasibility of 1H NMR spectroscopy to detect these resonances was also evaluated in human adipose tissue in vivo. Method Ten edible oils chosen to cover a wide spectrum of FA compositions were used as phantom material. The detailed FA composition and intrinsic proton spectra of the oils were characterized by gas chromatography and high-resolution 1H NMR spectroscopy (11.7 T), respectively. The detailed echo time behavior of the oils were subsequently measured by 1H NMR spectroscopy in a clinical scanner (1.5 T) using PRESS. The effect of temperature was investigated in five oils. Results The olefinic (5.3 ppm) and diallylic (2.8 ppm) resonances exhibited distinct J-modulation patterns independent of oil FA composition. The methylene resonance (1.3 ppm) displayed an exponential decay, with the apparent T 2 showing a weak positive correlation with oil unsaturation ( R = 0.628, P = 0.052), probably a result of changes in viscosity. For the methyl resonance (0.9 ppm), oils high in ω-3 FA displayed a markedly different J-modulation pattern compared to non-ω-3 oils. The characteristic J-modulation of the ω-3 methyl group could be attributed to the phase behavior of the ω-3 methyl triplet signal (all triplet lines in-phase at TE of 135 ms), a result of the ω-3 methyl end forming a first order spin system. The ω-3 methyl outer triplet line at 1.08 ppm of the TE = 140 ms spectrum was found to be useful for determining the ω-3 content of the oils ( R = 0.999, standard error of estimate (SE) 0.80). The olefinic and diallylic proton resonance (measured at TE = 50 ms) areas correlated with the olefinic ( R = 0.993, SE 0.33) and diallylic ( R = 0.997, SE 0.19) proton contents calculated from the GC data. Information derived from long echo time spectra (TE = 200) demonstrated good correlations to GC data and showed no change with increasing temperature (and T 2). In 1H NMR spectra (1.5 T) of adipose tissue in five healthy subjects, the analytically important olefinic and diallylic resonances were clearly resolved with a coefficient of variation of 1.6% and 8.4%, respectively, for repeated measurements. The characteristic phase behavior of the ω-3 methyl outer triplet line at 1.08 ppm could also be detected at very long echo times (470 and 540 ms). Conclusion Fatty acid composition has an impact on the echo time behavior of triglyceride resonances. Long TE spectra can resolve ω-3 FA in adipose tissue in vivo. These findings will benefit long TE studies of tissue lipids.

Microstructure of polyisoprene produced by cationic polymerization: NMR spectroscopic study

High-resolution 1H and 13C NMR spectroscopy, including two-dimensional heteronuclear experiments, has been used to study the microstructure of polyisoprene produced by cationic polymerization. It is shown that macromolecules resulting from both regular and inverse additions are predominantly composed of trans-1,4-units, while 1,2- and 3,4-units are present in small amounts. NMR spectra demonstrate the absence of cis-1,4-units in the polymer, whereas broad signals (pedestals) are related to the presence of saturated structures. It is proposed to determine the content of trans-1,4-, 1,2-, and 3,4-units in cationic polyisoprene via the combined measurements of intensities of signals in the olefinic regions of 1H and 13C NMR spectra.

Top-Down Systems Biology Modeling of Host Metabotype−Microbiome Associations in Obese Rodents

Covariation in the structural composition of the gut microbiome and the spectroscopically derived metabolic phenotype (metabotype) of a rodent model for obesity were investigated using a range of multivariate statistical tools. Urine and plasma samples from three strains of 10-week-old male Zucker rats (obese (fa/fa, n=8), lean (fa/-, n=8) and lean (-/-, n=8)) were characterized via high-resolution 1H NMR spectroscopy, and in parallel, the fecal microbial composition was investigated using fluorescence in situ hydridization (FISH) and denaturing gradient gel electrophoresis (DGGE) methods. All three Zucker strains had different relative abundances of the dominant members of their intestinal microbiota (FISH), with the novel observation of a Halomonas and a Sphingomonas species being present in the (fa/fa) obese strain on the basis of DGGE data. The two functionally and phenotypically normal Zucker strains (fa/- and -/-) were readily distinguished from the (fa/fa) obese rats on the basis of their metabotypes with relatively lower urinary hippurate and creatinine, relatively higher levels of urinary isoleucine, leucine and acetate and higher plasma LDL and VLDL levels typifying the (fa/fa) obese strain. Collectively, these data suggest a conditional host genetic involvement in selection of the microbial species in each host strain, and that both lean and obese animals could have specific metabolic phenotypes that are linked to their individual microbiomes.

Metabonomics studies of intact hepatic and renal cortical tissues from diabetic db/db mice using high-resolution magic-angle spinning 1H NMR spectroscopy

A metabonomics approach based on high-resolution magic-angle spinning (HRMAS) (1)H NMR spectroscopy was applied to investigate the metabolite composition in intact hepatic tissues and renal cortical tissues from db/db mice of 8 weeks old, an animal model of type 2 diabetes mellitus. Compared to the control group, the hepatic tissues of diabetic mice have elevated levels of triglyceride and bile acid and declined levels of trimethylamine-N-oxide, phosphocholine, glycerophosphocholine, and choline. The biochemical changes are less obvious in renal cortical tissues of diabetic mice. The WET_CPMG pulse sequence was selected for our metabonomics study after the quality and reproducibility of the spectra obtained from the NOEPR, NOEPR_CPMG, and WET_CPMG pulse sequences were analyzed together with principal component analysis. The influence of line-broadening factor of exponential window function for spectral manipulation on class separation was paid attention to for the first time, and an optimal value was obtained under our experimental conditions. These studies show the efficiency of HRMAS (1)H NMR spectroscopy for tissue metabonomics study in combination with multivariate statistical analysis, which may help to explore the etiological factor of diabetes mellitus from a new perspective.

Improved impurity fingerprinting of heparin by high resolution 1H NMR spectroscopy

For improving the identification of potential heparin impurities such as oversulfated chondroitin sulfate (OSCS) the standard 2D 1H- 1H NMR NOESY was applied. Taking advantage of spin diffusion and adjusting the experimental parameters accordingly additional contaminant-specific signals of the corresponding sugar ring protons can easily be detected. These are usually hidden by the more intense heparin signals. Compared to the current 1D 1H procedure proposed for screening commercial unfractionated heparin samples and focusing on the contaminants acetyl signals more informative and unique fingerprints may be obtained. Correspondingly measured 1H fingerprints of a few potential impurities are given and their identification in two contaminated commercial heparin samples is demonstrated. The proposed 2D NOESY method is not intended to replace the current 1D method for detecting and quantifying heparin impurities but may be regarded as a valuable supplement for an improved and more reliable identification of these contaminants.

Impact of the salt stress on the photosynthetic carbon flux and 13C-label distribution within floridoside and digeneaside in Solieria chordalis

The flux of photosynthetic carbon used in the synthesis of low-molecular weight carbohydrates (digeneaside and floridoside) was investigated by 13C and 1H NMR spectroscopy in samples of the red seaweed, Solieria chordalis, incubated at different salinities (22, 34 and 50 psu). Carbohydrates were labelled, by pulse-chase, with the stable isotope 13C from NaH 13CO 3. In vivo NMR analyses carried out with a cryogenic probe optimised for 13C detection were performed directly on the living algal tissues to evidence the labelling of the carbohydrates with neither preliminary extraction nor purification step(s). The isotopic enrichment of each compound was determined by high-resolution 1H and 13C NMR spectroscopy. These analyses evidenced different orientations of the flux of the photosynthetic carbon in the algae according to the salt stress. At normal and low salinities, the photosynthetic carbon flux was responsible of 70% and 67% of the floridoside synthetized during the pulse period, respectively, whereas it was only of 30% in the thalli exposed to the high salinity, meaning a biosynthesis of high floridoside amount from endogen source leading to the osmotic regulation. Under normal and hyper-osmotic conditions, the stock of floridoside was used for cellular needs during the chase period, whereas it was not under hypo-osmotic conditions. The characterization of isotopomers composition of floridoside and digeneaside and the analysis of adjacent 13C-labelling gives much more details on the effects of salinity on the metabolic pathways leading to the synthesis or the degradation of these molecules. High turnover of floridoside was evidenced at normal salinity during the chase period and products issued from the degradation of floridoside would not be used for the novo biosynthesis. That suggests that synthesis and degradation of floridoside may be realized in two different cellular compartments. The presence of more numerous 13C– 13C blocks in the carbon skeleton of the molecules from the up salt stressed thalli than in those from no salt stressed algae, concomitant with a slower degree of isotopic enrichment of the molecule, provided evidence that the two metabolic pathways (endogen and photosynthetic) may not share the precursor molecules involved in the floridoside synthesis and that these two routes may be totally separate until the constitution of floridoside molecule.

Detection and quantification of phenolic compounds in olive oil by high resolution 1H nuclear magnetic resonance spectroscopy

High resolution 1H NMR spectroscopy has been employed as a versatile and rapid method to analyze the polar fraction of extra virgin olive oils containing various classes of phenolic compounds. The strategy for identification of phenolic compounds is based on the NMR chemical shifts of a large number of model compounds assigned by using two-dimensional (2D) NMR spectroscopy. Furthermore, 2D NMR was applied to phenolic extracts in an attempt to discover additional phenolic compounds. The 1H NMR methodology was successful in detecting simple phenols, such as p-coumaric acid, vanillic acid, homovanillyl alcohol, vanillin, free tyrosol, and free hydroxytyrosol, the flavonols apigenin and luteolin, the lignans (+) pinoresinol, (+) 1-acetoxypinoresinol and syringaresinol, two isomers of the aldehydic form of oleuropein and ligstroside, the dialdehydic form of oleuropein and ligstroside lacking a carboxymethyl group, and finally total hydroxytyrosol and total tyrosol reflecting the total amounts of free and esterified hydroxytyrol and tyrosol, respectively. The absolute amount of each phenolic constituent was determined in the polar fraction by using anhydrous 1,3,5-triazine as an internal standard.

Structural Influence of Calcium on the Heme Cavity of Cationic Peanut Peroxidase as Determined by 1H-NMR Spectroscopy

The cationic isozyme of peanut peroxidase (CPRx) is one of many peroxidases which requires calcium for enzyme activity. It has been previously shown that it requires 2 mol calcium to coordinate to 1 mol CPRx, and its related peroxidases from the basidiomycete Phanerochaete chrysosporium (LiP) and isozyme C of horseradish (HRPc). X-ray crystallographic studies of LiP have shown that calcium is ligated near the C-terminus of helices proximal and distal to the heme, where it has been suggested to maintain the active site. To determine if such a mechanism was possible in CPRx, high resolution 1H-NMR spectroscopy was used to study the effect of calcium on the environment of its heme group and the coordinating histidine residues. The low-spin cyano complex of the enzyme (CPRxCN) was studied in order to assign the majority of the resonances arising from the protons in the heme pocket in both the presence and absence of bound calcium ions using two dimensional nuclear Overhauser effect spectroscopy (NOESY). The two calcium ions present in CPRxCN were removed by a non-denaturing method and a calcium titration was performed and monitored by 1H-NMR spectroscopy. These studies showed that the binding of both calcium ions in CPRx influenced the heme environment in a similar manner (Kd = 0.1 microM). In particular, calcium-dependent changes in several heme resonances and the proximal and distal histidine residues suggest that calcium binding to CPRx causes some reorientation of these residues with respect to the active site.