Deuterium-induced Isotope Shifts Research Articles

NMR Analyses of Carbohydrate–Water and Water–Water Interactions in Water/DMSO Mixed Solvents, Highlighting Various Hydration Behaviors of Monosaccharides Glucose, Galactose and Mannose

Abstract Interaction with water molecules is a potential factor for regulating carbohydrate functions. We analyzed the influences of methyl α-glucoside, methyl α-galactoside and methyl α-mannoside on water in solution through NMR measurements. In order to compare the hydration behaviors according to the geometric characteristics of monosaccharides, proton exchanges between the carbohydrate and water and between water molecules were observed using H2O/D2O and dimethylsulfoxide mixed solvents to employ deuterium-induced isotope shifts. 13C NMR analyses focused on the carbohydrate hydroxy groups revealed that the carbohydrate–water proton exchange in the mannoside solution proceeded slower than in others. Meanwhile, the frequent proton exchange between waters in the mannoside solution was shown by NMR observations of water signals. Our NMR experimental results shed light on the variation of solvation environments of carbohydrates according to their geometric characteristics. Mannose presumably allows for unique orientations of the adjacent water molecules to induce the expansion of water networks efficiently.

New NMR Tools for Characterizing the Dynamic Conformations and Interactions of Oligosaccharides

Abstract Oligosaccharides play pivotal roles in various molecular recognition events on cell surfaces and in intracellular environments. Although information about the three-dimensional structure of oligosaccharides is crucial for understanding the mechanisms underlying their biological functions and for designing drugs targeting carbohydrate recognition systems, their inherent flexibility hampers detailed conformational analysis. NMR spectroscopy has immense potential for providing atomic details of oligosaccharide structures in solution as well as in complexes with other biomolecules. However, the traditional NMR approach based on local conformational information provided by the nuclear Overhauser effect (NOE) is often precluded by insufficient information about long interatomic distances and hydrogen bonds involving hydroxy groups. To address these issues, new NMR techniques have recently been developed, exploiting the effects of introduced paramagnetic probes and stable isotopes to target oligosaccharides. Lanthanoid tagging and the spin labeling of oligosaccharides induce paramagnetic effects such as pseudocontact shift and paramagnetic relaxation enhancement, offering NOE-independent sources of long-distance information. Deuterium-induced isotope shifts of neighboring 13C resonances provide an experimental tool for the identification of hydrogen bonds involving oligosaccharide hydroxy groups. The uniform and position-selective 13C enrichment of oligosaccharides can be achieved by metabolic labeling using genetically engineered yeast cells. Furthermore, small ganglioside-embedding bicelles have been used for detailed NMR analyses of intermolecular interactions involving glycolipids in membrane environments. These NMR approaches, in conjunction with computational simulation, have opened up new vistas for the analysis of oligosaccharide conformations and interactions at atomic level.

ChemInform Abstract: Selected Topics from Recent NMR Studies of Organolithium Compounds

After a short introduction to NMR spectroscopy of alkali and alkaline earth metals the review concentrates on NMR investigations of organolithium compounds. The isotopic fingerprint method, which rests on deuterium-induced isotope shifts for 6Li resonances, is introduced and exemplified with applications from the aggregation behavior of cyclopropyllithium systems and mixed aggregate formation between methyllithium and lithium salts. In the following chapter, one- and two-dimensional pulse experiments, both for homo- and for heteronuclear spin systems are discussed. Finally, the structural aspects associated with benzyllithium are outlined and the formation of polylithium systems by lithium reduction of biphenylenes is described.

Nuclear motion effects on the [formula omitted], [formula omitted] and [formula omitted] shielding in methyl fluoride

The 19 F , 13 C and 1 H shielding in methyl fluoride and its deuterated isotopomers has been calculated from ab initio shielding surfaces for selected temperatures. In each case it is the stretching which contributes most to the nuclear motion corrections which total −9.425 ppm for the 19 F shielding, −4.558 ppm for the 13 C shielding and −0.601 ppm for the proton shielding. However, some second-order stretching and bending contributions are significant. The deuterium induced isotope shifts are substantial and should be easily measurable. There is a predicted nonadditivity in the 19 F and 13 C isotope shifts which can be traced to two of the bending contributions.

Isotopic perturbation of resonance in a homologous series of metal complexes with allylic cation character

Deuterium-induced isotope shifts in a series of ML n (L = statistical mixture of 3-oxido-2-phenylpropenal-d0, -1-d and -1,3-d2) were measured. The 13C NMR isotope shifts, δC(D) − δC(H), for the aldehydic CH of AlL3, Al(OiPr)2L, (CH3)2AlL, SiBr3L, SiL3+HBr2−, (CF3)3GeL, (EtO)4NbL, Rh(CO)2L, PdL2, SbCl4L and (EtO)4TaL are small and positive. The positive isotope shifts are unusual, but since they are small and temperature independent they are intrinsic. A relationship between these isotope shifts and the chemical shifts can be discerned and attributed to isotopic perturbation of resonance in an allylic cation. Copyright © 2000 John Wiley & Sons, Ltd.

Selected topics from recent NMR studies of organolithium compounds

After a short introduction to NMR spectroscopy of alkali and alkaline earth metals the review concentrates on NMR investigations of organolithium compounds. The isotopic fingerprint method, which rests on deuterium-induced isotope shifts for 6Li resonances, is introduced and exemplified with applications from the aggregation behavior of cyclopropyllithium systems and mixed aggregate formation between methyllithium and lithium salts. In the following chapter, one- and two-dimensional pulse experiments, both for homo- and for heteronuclear spin systems are discussed. Finally, the structural aspects associated with benzyllithium are outlined and the formation of polylithium systems by lithium reduction of biphenylenes is described.

Dependence of one‐bond deuterium isotope shifts in 13C NMR on CH bond lengths for substituted and unsubstituted aromatic compounds

AbstractOne‐bond deuterium‐induced isotope shifts of 13C NMR (1Δ) for 106 sp2‐hybridized carbons are discussed in terms of CH bond lengths. 1Δ correlates linearly with the related CH bond length calculated by the MNDO MO method by the equation 1Δ(ppb)=8350 rCH (Å) – 8824.

The vibrational and temperature dependence of the magnetic properties of the oxonium ion (H 3O +)

First-and second-order polarization propagator calculations of magnetizability, rotational g-factor, spin-rotation constant, and hydrogen and oxygen shielding propterty surfaces are reported for the gas phase oxomium ion. Using these surfaces and the nonrigid inverter ro-vibrational eigenfunctions, effective magnetic molecular constants are obtained for the lowest ro-inversional states of H 3 17O + and D 3 17O +. The predicted constants exhibit sizable and non-monotonic dependence on the vibrational and rotational quantum numbers. We find nearly temperature independence of both the 1H and 17O shieldings, mainly due to cancellation effects between contributions from the inversional and the symmetric stretching modes. We compute a downfield shift in 1H as well as 17O shieldings of H 3O + relative to pure water in agreement with earlier observations. The influence of hydrogen bonding on these shifts, as well as on the deuterium-induced isotope shifts on the 17O shielding, is discussed.

Isotopic multiplets in the carbon-13 nuclear magnetic resonance spectra due to partial deuteriation of co-ordinated NH2 and NH groups of cobalt(III) complexes containing an N-glycoside. Importance of sugar ring oxygen atoms in the long-range isotope shifts

Carbon-13 n.m.r. measurements have been made in H2O–D2O solutions of cobalt(III) complexes containing an N-glycoside derived from ethylenediamine and an aldose (D-ribose or L-rhamnose). Partial deuteriation of exchangeable protons on the co-ordinated nitrogen atoms permits direct observation of the individual isotopomers and the resonances are observed as a series of multiplets, which can be analysed in terms of the two-bond and three-bond isotope effects that contribute to the deuterium-induced isotope shifts. The C–N bond formation between ethylenediamine and an aldose in the cobalt(III) complexes has been unambiguously confirmed by the information derived from the isotopic multiplets together with complete assignments of 13C signals from the sugar units by means of two-dimensional n.m.r. spectroscopy. An extra doublet originating from the four-bond isotope effect is observed for the D-ribosyl residue, which suggests that the sugar ring takes the furanose form. The importance of sugar ring oxygen atoms in the long-range deuterium isotope shifts is discussed including an examination by use of C1-methine proton deuteriated aldoses.

77Se NMR on an XL-100 spectrometer. An investigation of isotope effects and spin-lattice relaxation in H 2Se

The design of a voltage-controlled oscillator (VCO), phase-locked to the 1-MHz output of a commercial frequency synthesizer (General Radio 1061), is described. The output frequency of the VCO, capable of producing either 15.400000 or 15.300000 MHz, has been injected into the lock channel of a Varian XL-100 spectrometer as the deuterium field/frequency lock transmitter frequency. This modification allows “normal” proton-decoupled 77Se FT NMR spectra to be obtained on this spectrometer. Secondary deuterium-induced isotope shifts of more than 7 ppm have been observed in the 77Se NMR spectrum of a solution of H 2−nD nSe ( n = 0, 1, and 2) in deuteriochloroform. Primary and secondary isotope effects on the 77Se- 1H coupling constants are also observed. Also, it is shown that 77Se spin-lattice relaxation in hydrogen selenide is dominated completely by the spin-rotation mechanism.

Modular IC tester is easily optimized : William F. Arnold. Electronics p. 155 (5 July 1979)

The design of a voltage-controlled oscillator (VCO), phase-locked to the 1-MHz output of a commercial frequency synthesizer (General Radio 1061), is described. The output frequency of the VCO, capable of producing either 15.400000 or 15.300000 MHz, has been injected into the lock channel of a Varian XL-100 spectrometer as the deuterium field/frequency lock transmitter frequency. This modification allows “normal” proton-decoupled 77Se FT NMR spectra to be obtained on this spectrometer. Secondary deuterium-induced isotope shifts of more than 7 ppm have been observed in the 77Se NMR spectrum of a solution of H2−nDnSe (n = 0, 1, and 2) in deuteriochloroform. Primary and secondary isotope effects on the 77Se-1H coupling constants are also observed. Also, it is shown that 77Se spin-lattice relaxation in hydrogen selenide is dominated completely by the spin-rotation mechanism.