MS and NMR Analysis of Isotopically Labeled Chloramination Disinfection Byproducts: Hyperlinks and Chemical Reactions.

FT-ICR MS and NMR analysis of an isotopically labeled complex mixture of water disinfection byproducts formed by chloramine disinfection of model phenolic acids is described. A new molecular formula assignment procedure using the CoreMS Python library able to assign isotopically enriched formulas is proposed. Statistical analysis of the assigned formulas showed that the number of compounds, the diversity of the mixture, and the chlorine count increase during the chloramination reaction.

Clean PDI-1 SQ: Suppression of HSQC artifacts in 2D proton-detected INADEQUATE spectra by pulse sequence redesign.

Proton-detected INADEQUATE NMR experiments are widely used for structure elucidation of small molecules, in particular the implementations that display C single-quantum rather than double-quantum frequencies in the indirect dimension of 2D spectra. But unfortunately, such spectra in addition to the desired H-C two-bond correlations also contain HSQC artifacts of comparable magnitude. The redesigned versatile experiment presented in this paper requires no compromise based on different C multiplicities and suppresses the HSQC artifacts that are a source of possible spectral misinterpretation.

SHARPER-DOSY: Sensitivity enhanced diffusion-ordered NMR spectroscopy.

Since its discovery in mid-20 century, the sensitivity of Nuclear Magnetic Resonance (NMR) has increased steadily, in part due to the design of new, sophisticated NMR experiments. Here we report on a liquid-state NMR methodology that significantly increases the sensitivity of diffusion coefficient measurements of pure compounds, allowing to estimate their sizes using a much reduced amount of material. In this method, the diffusion coefficients are being measured by analysing narrow and intense singlets, which are invariant to magnetic field inhomogeneities.

Enhancing F Benchtop NMR Spectroscopy by Combining -Hydrogen Hyperpolarization and Multiplet Refocusing.

Benchtop NMR spectrometers provide a promising alternative to high-field NMR for applications that are limited by instrument size and/or cost. F benchtop NMR is attractive due to the larger chemical shift range of F relative to H and the lack of background signal in most applications. However, practical applications of benchtop F NMR are limited by its low sensitivity due to the relatively weak field strengths of benchtop NMR spectrometers.

More than ADEQUATE: doubling the sensitivity of CH-CH correlations in double-quantum NMR experiments.

We present modifications of the ADEQUATE experiment which more than double the sensitivity of carbon-carbon correlations of CH-CH moieties. Additionally, these improvements can be applied without a sensitivity penalty to obtain spectra with a C chemical shift axis in the indirectly detected dimension, instead of a double-quantum frequency, allowing simpler interpretation of spectra. The modified experiments, which use refocussing of couplings and H decoupling during evolution intervals, were tested on several molecules, including a pentasaccharide (20 mg, 19 mM), where on average a 2.

New F NMR methodology reveals structures of molecules in complex mixtures of fluorinated compounds.

Although the number of natural fluorinated compounds is very small, fluorinated pharmaceuticals and agrochemicals are numerous. F NMR spectroscopy has a great potential for the structure elucidation of fluorinated organic molecules, starting with their production by chemical or chemoenzymatic reactions, through monitoring their structural integrity, to their biotic and abiotic transformation and ultimate degradation in the environment. Additionally, choosing to incorporate F into any organic molecule opens a convenient route to study reaction mechanisms and kinetics.

F-centred NMR analysis of mono-fluorinated compounds.

Addressing limitations of the existing NMR techniques for the structure determination of mono-fluorinated compounds, we have developed methodology that uses F as the focal point of this process. The proposed F-centred NMR analysis consists of a complementary set of broadband, phase-sensitive NMR experiments that utilise the substantial sensitivity of F and its far reaching couplings with H and C to obtain a large number of NMR parameters. The assembled H, C and F chemical shifts, values of , , and coupling constants and the size of C induced F isotopic shifts constitute a rich source of information that enables structure elucidation of fluorinated moieties and even complete structures of molecules.

SHARPER-enhanced benchtop NMR: improving SNR by removing couplings and approaching natural linewidths.

We present a signal enhancement strategy for benchtop NMR that produces SNR increases on the order of 10 to 30 fold by collapsing the target resonance into an extremely narrow singlet. Importantly, the resultant signal is amenable to quantitative interpretation and therefore can be applied to analytical applications such as reaction monitoring.

Methane emissions and rumen metabolite concentrations in cattle fed two different silages.

In this study, 18 animals were fed two forage-based diets: red clover (RC) and grass silage (GS), in a crossover-design experiment in which methane (CH) emissions were recorded in respiration chambers. Rumen samples obtained through naso-gastric sampling tubes were analysed by NMR. Methane yield (g/kg DM) was significantly lower from animals fed RC (17.

Monitoring off-resonance signals with SHARPER NMR - the MR-SHARPER experiment.

We demonstrate an extension to the SHARPER (Sensitive Homogenous and Refocussed Peaks in Real Time) NMR experiment which allows more than one signal to be monitored simultaneously, while still giving ultra-sharp, homo- and hetero-decoupled NMR signals. This is especially valuable in situations where magnetic field inhomogeneity would normally make NMR a problematic tool, for example when gas evolution is occurring during reaction monitoring. The originally reported SHARPER experiment only works for a single, on-resonance NMR signal, but here we demonstrate the Multiple Resonance SHARPER approach can be developed, which in principle can acquire multiple on-/off-resonance signals simultaneously while retaining the desirable properties of the parent sequence.

Comparison of HPLC and NMR for quantification of the main volatile fatty acids in rumen digesta.

Accurate quantification of volatile fatty acid (VFA) concentrations in rumen fluid are essential for research on rumen metabolism. The study comprehensively investigated the pros and cons of High-performance liquid chromatography (HPLC) and H Nuclear magnetic resonance (H-NMR) analysis methods for rumen VFAs quantification. We also investigated the performance of several commonly used data pre-treatments for the two sets of data using correlation analysis, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA).

Rapid Estimation of for Quantitative NMR.

Quantitative NMR spectroscopy (qNMR) is an essential tool in organic chemistry, with applications including reaction monitoring, mechanistic analysis, and purity determination. Establishing the correct acquisition rate for consecutive qNMR scans requires knowledge of the longitudinal relaxation time constants () for all of the nuclei being monitored. We report a simple method that is about 10-fold faster than the conventional inversion recovery technique for the estimation of .

Quantification of whisky congeners by H NMR spectroscopy.

Whisky is a complex mixture made up of thousands of compounds originating in different stages of its production. Analysis of whisky congeners is critical to our understanding of the manufacturing process, quality control, and the detection of counterfeit products. The current chromatographic methods have a long analysis time, can require milliliters of sample and may not detect all required compounds in a single analysis.

Nuclear Magnetic Resonance to Detect Rumen Metabolites Associated with Enteric Methane Emissions from Beef Cattle.

This study presents the application of metabolomics to evaluate changes in the rumen metabolites of beef cattle fed with three different diet types: forage-rich, mixed and concentrate-rich. Rumen fluid samples were analysed by H-NMR spectroscopy and the resulting spectra were used to characterise and compare metabolomic profiles between diet types and assess the potential for NMR metabolite signals to be used as proxies of methane emissions (CH in g/kg DMI). The dataset available consisted of 128 measurements taken from 4 experiments with CH measurements taken in respiration chambers.

Group A, B, C, and G Lancefield antigen biosynthesis is initiated by a conserved α-d-GlcNAc-β-1,4-l-rhamnosyltransferase.

Group A carbohydrate (GAC) is a bacterial peptidoglycan-anchored surface rhamnose polysaccharide (RhaPS) that is essential for growth of and contributes to its ability to infect the human host. In this study, using molecular and synthetic biology approaches, biochemistry, radiolabeling techniques, and NMR and MS analyses, we examined the role of GacB, encoded in the GAC gene cluster, in the GAC biosynthesis pathway. We demonstrate that GacB is the first characterized α-d-GlcNAc-β-1,4-l-rhamnosyltransferase that synthesizes the committed step in the biosynthesis of the GAC virulence determinant.

Analysis of Scotch Whisky by H NMR and chemometrics yields insight into its complex chemistry.

Scotch Whisky has been analysed as a complex mixture in its raw form using high resolution Nuclear Magnetic Resonance (NMR) and previously developed water and ethanol suppression techniques. This has allowed for the positive identification of 25 compounds in Scotch Whisky by means of comparison to reference standards, spike-in experiments, and advanced 1D and 2D NMR experiments. Quantification of compounds was hindered by signal overlap, though peak alignment strategies were largely successful.

Complementary Ionization Techniques for the Analysis of Scotch Whisky by High Resolution Mass Spectrometry.

Fourier transform mass spectrometry (FTMS) is widely used to characterize the chemical complexity of mixtures, such as natural organic matter (NOM), petroleum, and agri-food products (including Scotch whisky). Although electrospray ionization (ESI) is by far the most widely used ionization source in these studies, other ionization techniques are available and may offer complementary information. In a recent study, we found matrix free laser desorption/ionization (LDI) to be effective for the analysis of Suwannee river fulvic acid (SRFA), and to provide complementary chemical insights.

Order in disorder: solution and solid-state studies of [MM] wheels (M = Cr, Al; M = Ni, Zn).

A family of heterometallic Anderson-type 'wheels' of general formula [MIII2MII5(hmp)12](ClO4)4 (where MIII = Cr or Al and MII = Ni or Zn giving [Cr2Ni5] (1), [Cr2Zn5] (2), [Al2Ni5] (3) and [Al2Zn5] (4); hmpH = 2-pyridinemethanol) have been synthesised solvothermally. The metallic skeleton common to all structures describes a centred hexagon with the MIII sites disordered around the outer wheel. The structural disorder has been characterised via single crystal X-ray crystallography, 1-3D 1H and 13C solution-state NMR spectroscopy of the diamagnetic analogue (4), and solid-state 27Al MAS NMR spectroscopy of compounds (3) and (4).

(3, 2)D H, C BIRD-HSQC-TOCSY for NMR structure elucidation of mixtures: application to complex carbohydrates.

Overlap of NMR signals is the major cause of difficulties associated with NMR structure elucidation of molecules contained in complex mixtures. A 2D homonuclear correlation spectroscopy in particular suffers from low dispersion of H chemical shifts; larger dispersion of C chemical shifts is often used to reduce this overlap, while still providing the proton-proton correlation information e.g.

SHARPER Reaction Monitoring: Generation of a Narrow Linewidth NMR Singlet, without X-Pulses, in an Inhomogeneous Magnetic Field.

We report a new pure-shift method, termed SHARPER (Sensitive, Homogeneous, And Resolved PEaks in Real time) designed for the analysis of reactions and equilibria by NMR. By focusing on a single selected signal, SHARPER removes all heteronuclear couplings of a selected nucleus without the need to pulse on X channels, thus overcoming hardware limitations of conventional spectrometers. A more versatile decoupling scheme, termed sel-SHARPER, removes all heteronuclear and homonuclear couplings of the selected signal.

Advanced solvent signal suppression for the acquisition of 1D and 2D NMR spectra of Scotch Whisky.

A simple and robust solvent suppression technique that enables acquisition of high-quality 1D H nuclear magnetic resonance (NMR) spectra of alcoholic beverages on cryoprobe instruments was developed and applied to acquire NMR spectra of Scotch Whisky. The method uses 3 channels to suppress signals of water and ethanol, including those of C satellites of ethanol. It is executed in automation allowing high throughput investigations of alcoholic beverages.