The cubic mesophase formed by monoacylglycerols and water is an important medium for the in meso crystallogenesis of membrane proteins. To investigate molecular level lipid and additive interactions within the cubic phase, a method was developed for improving the resolution of 1H NMR spectra when using a conventional solution state NMR probe. Using this approach we obtained well-resolved J-coupling multiplets in the one-dimensional NMR spectrum of the cubic-Ia3d phase prepared with hydrated monoolein. A high resolution t-ROESY two-dimensional 1H NMR spectrum of the cubic-Ia3d phase is also reported. Using this new methodology, we have investigated the interaction of two additive molecules, l-tryptophan and ruthenium-tris(2,2-bipyridyl) dichloride (rubipy), with the cubic mesophase. Based on the measured chemical shift differences when changing from an aqueous solution to the cubic phase, we conclude that l-tryptophan experiences specific interactions with the bilayer interface, whereas rubipy remains in the aqueous channels and does not associate with the lipid bilayer.

A sensitivity enhancement method based on selective adiabatic inversion of a satellite transition has been employed in a (π/2)CT–(π)ST1(π)ST1–(π/2)CT spectral editing sequence to both enhance and resolve multisite NMR spectra of quadrupolar nuclei. In addition to a total enhancement of 2.5 times for spin 3/2 nuclei, enhancements up to 2.0 times is reported for the edited sites in a mixture of rubidium salts.

Ab initio   band-structure calculations based on density functional theory have been completed for αα-quartz phase GeO2GeO2 to obtain electric-field gradients (efg) for oxygen atoms, including those for GeO2GeO2 at elevated pressure and temperature. To interpret the resulting efg values and examine correlations between structure and 17O quadrupolar coupling parameters, additional ab initio   self-consistent Hartree-Fock molecular orbital calculations were completed. The quadrupolar coupling constant was found to have a strong dependence on Ge–O distance and ∠Ge–O–Ge∠Ge–O–Ge, with the quadrupolar asymmetry parameter being primarily dependent on ∠Ge–O–Ge∠Ge–O–Ge. Analytical expressions describing these dependencies consistent with earlier investigations of analogous silicate compounds are also reported.

Solid-state 17O magic-angle spinning nuclear magnetic resonance measurements at 19.5 Tesla were performed on 17O-enriched methyl α-d-galactopyranoside (4-17O), methyl β-d-glucopyranoside (2-17O), methyl α-d-glucopyranoside (4-17O), methyl α-d-glucopyranoside (6-17O), and α-d-glucopyranosyl (1 → 6) α-d-glucopyranoside (6-17O). The 17O quadrupolar coupling constants and asymmetry parameters measured can be predicted with a model based entirely on the first-coordination sphere around oxygen. For the hydroxyl sites observed in the methyl glucosides, the quadrupolar coupling parameters are nearly identical, within 10% as predicted, given their nearly identical first-coordination sphere structures.The 17O quadrupolar coupling constants in carbohydrate hydroxyl groups and a glycosidic linkage have been measured, for the first time, using 17O NMR. Our analysis shows that a simple model can be used for relating the 17O electric field gradient to local structure around these functional groups.

Pyrex® is an ubiquitous material that has attained widespread use in laboratory glassware and household utensils due to its properties, cost effectiveness, and ease of fabrication. Despite its importance, the structure of borosilicate glass such as Pyrex® is not fully understood. Here, we report high resolution 29Si, 27Al, and 11B magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic measurements at 9.4 and 19.5 T, combined with 27Al and 11B multiple-quantum MAS (MQ-MAS), and 11B Rotor Assisted Population Transfer (RAPT), to identify structural features in Pyrex®. A distribution of Q4 silicon and aluminum sites is observed, and there is no evidence of five or six coordinated aluminum. The 27Al quadrupolar coupling constants for the tetrahedral aluminum varied from 3.5 to 4.5 MHz, while the isotropic chemical shifts varied from 50 to 65 ppm. Boron-11 measurements resolve four distinct distributions in boron environments: two identified as tetrahedral, BO4, and two as trigonal, BO3. Tetrahedral sites are distinguished by different second coordination spheres, e.g., BO4(0 B, 4 Si) and BO4(1 B, 3 Si), and the trigonal sites based on the symmetry of the boron environments.

We report the application of rotor-assisted population transfer (RAPT) to measure the quadrupolar coupling constant (Cq)(Cq) for spin 52 nuclei. Results from numerical simulations are presented on the magnitude of enhancement factor as a function of frequency offsets, i.e. the RAPT profile. Experimental O17 RAPT profile is traced for the amino acid l-leucine. In addition, results from MQ-MAS experiments are incorporated to determine the quadrupolar asymmetry parameter (ηq)(ηq). Unlike previous reports, the O17 NMR parameters for an amino acid, l-leucine, is reported at a relatively low field of 9.4 T.

We have performed ab initio calculations on the model cluster (OH)3Ge–O–Ge(OH)3 in order to refine the relationships between 17O quadrupolar coupling parameters and the local structure around the bridging oxygen. From these calculations the trend in the bridging oxygen 17O quadrupolar coupling constant, Cq, and asymmetry parameter, ηq, with changing Ge–O–Ge angle was found to be similar to previously established trends in silicate clusters with the overall Cq values being systematically increased in magnitude by approximately 3 MHz. Such a shift can be attributed to differences in cation–oxygen distances as well as coordinating cation electronegativity. In addition, we also investigated the effect of changing intratetrahedron bond angles over a range that has been suggested to exist in germanate systems. While such variations in intratetrahedron bond angles lead to a small variation in Cq, ηq remains relatively unaffected. In such cases, ηq can still be a reliable probe of Ge–O–Ge angle while Cq could serve as a probe of tetrahedron distortions.

A common approach to quantify Q(n) species in silicate glasses is to use 29Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and assume that the overlapping isotropic chemical shift distributions of Q(n) species are Gaussian. We have shown that a two-dimensional isotropic/anisotropic 29Si NMR experiment can not only determine the distributions of Q(n) species without any a priori assumptions about the distribution, but can also provide over an order of magnitude improvement in the precision of Q(n) species quantification in silicate glasses. Using this approach we have investigated an alkali silicate glass of composition 2Na2O · 3SiO2 and have observed a small concentration of Q(4) in a sample mainly having Q(2) and Q(3). We have found that the distribution of isotropic chemical shifts for each of the Q(n) is approximately Gaussian. The relative populations of Q(2), Q(3), and Q(4) obtained from these separated distributions give an equilibrium constant of 0.0129 ± 0.0001 for the disproportionation reaction 2 Q(3) ⇌ Q(2) + Q(4). This value is slightly higher than what is obtained from analyzing the one-dimensional MAS spectrum alone, thus revealing a higher degree of disorder in speciation and configurational entropy for the glass.