Solid-state Nuclear Magnetic Resonance Studies Research Articles

Structural investigations of perlite and expanded perlite using 1H, 27Al and 29Si solid-state NMR

Industrial grade perlite and expanded perlite systems were investigated by multifield and multinuclear Solid State Nuclear Magnetic Resonance (SSNMR), Fourier Transform Infra-Red (FTIR) spectroscopies and Scanning Electron Microscopy (SEM). The SSNMR studies focussed on the 1H, 29Si and 27Al nuclei using single pulse excitation (SPE) and 1H, 29Si cross-polarization Magic-Angle-Spinning (CP-MAS) conditions, with 27Al Triple Quantum Magic-Angle-Spinning (3QMAS) measurements also being implemented. The resonances at ~ 52ppm detected in the 27Al MAS NMR spectra of the industrial grade and expanded systems are tentatively assigned to tetrahedrally coordinated aluminium, while the resonance at ~ 5ppm, which was only observed in the industrial grade perlite spectrum, is attributed to octahedrally coordinated aluminium. In neither case could the pentahedrally coordinated positions be identified using 27Al MAS and 3QMAS techniques. 27Al data suggests that tetrahedrally coordinated aluminium atoms do not have a significant role in the grain expansion process. The broad resonance envelopes found in the 29Si MAS NMR and FTIR data of both perlites were analyzed by the second-order derivative. The analyses confirmed complex Qn configurations for the perlitic structure suggesting the prevalence of Q3 and Q4 species. 1H-29Si CP-MAS spectra support the presence of Q2 units suggested by FTIR and SPE data. SEM micrographs revealed the honeycomb morphology of expanded domains in perlite after heat treatment.

Composite Polymer Electrolytes with Li7La3Zr2O12 Garnet-Type Nanowires as Ceramic Fillers: Mechanism of Conductivity Enhancement and Role of Doping and Morphology.

Composite polymer solid electrolytes (CPEs) containing ceramic fillers embedded inside a polymer-salt matrix show great improvements in Li+ ionic conductivity compared to the polymer electrolyte alone. Lithium lanthanum zirconate (Li7La3Zr2O12, LLZO) with a garnet-type crystal structure is a promising solid Li+ conductor. We show that by incorporating only 5 wt % of the ceramic filler comprising undoped, cubic-phase LLZO nanowires prepared by electrospinning, the room temperature ionic conductivity of a polyacrylonitrile-LiClO4-based composite is increased 3 orders of magnitude to 1.31 × 10-4 S/cm. Al-doped and Ta-doped LLZO nanowires are also synthesized and utilized as fillers, but the conductivity enhancement is similar as for the undoped LLZO nanowires. Solid-state nuclear magnetic resonance (NMR) studies show that LLZO NWs partially modify the PAN polymer matrix and create preferential pathways for Li+ conduction through the modified polymer regions. CPEs with LLZO nanoparticles and Al2O3 nanowire fillers are also studied to elucidate the role of filler type (active vs passive), LLZO composition (undoped vs doped), and morphology (nanowire vs nanoparticle) on the CPE conductivity. It is demonstrated that both intrinsic Li+ conductivity and nanowire morphology are needed for optimal performance when using 5 wt % of the ceramic filler in the CPE.

Preparation, upconversion luminescence, and solid-state NMR studies of water-soluble hexagonal NaScF4:Yb/Er microcrystals

Water-soluble hexagonal NaScF4:Yb/Er upconversion microcrystals (UCMCs) were synthesized using the hydrothermal method. The upconversion photoluminescence properties of NaScF4:xYb/2%Er microcrystals (x = 4–20%) were characterized under a 980-nm-wavelength laser excitation. The dependence of red/green (R/G) ratio on the concentration of Yb3+ ions was investigated. The local environments of dopant ions (Yb3+, Er3+) in NaScF4 were studied using multiple solid-state nuclear magnetic resonance (NMR) techniques. The 19F single pulse and 19F{23Na} and 19F{45Sc} rotational echo double resonance (REDOR) techniques proved that the dopant rare-earth ions (Yb3+, Er3+) preferred to substitute Na+ rather than Sc3+ ions. Such solid-state NMR techniques provide a novel approach to study new phosphors.

The Role of Structural and Compositional Heterogeneities in the Insulator-to-Metal Transition in Hole-Doped APd3O4 (A = Ca, Sr).

The cubic semiconducting compounds APd3O4 (A = Ca, Sr) can be hole-doped by Na substitution on the A site and driven toward more conducting states. This process has been followed here by a number of experimental techniques to understand the evolution of electronic properties. While an insulator-to-metal transition is observed in Ca1-xNaxPd3O4 for x ≥ 0.15, bulk metallic behavior is not observed for Sr1-xNaxPd3O4 up to x = 0.20. Given the very similar crystal and (calculated) electronic structures of the two materials, the distinct behavior is a matter of interest. We present evidence of local disorder in the A = Sr materials through the analysis of the neutron pair distribution function, which is potentially at the heart of the distinct behavior. Solid-state 23Na nuclear magnetic resonance studies additionally suggest a percolative insulator-to-metal transition mechanism, wherein presumably small regions with a signal resembling metallic NaPd3O4 form almost immediately upon Na substitution, and this signal grows monotonically with substitution. Some signatures of increased local disorder and a propensity for Na clustering are seen in the A = Sr compounds.

Solid-state NMR studies for the development of non-woven biomaterials based on silk fibroin and polyurethane

Silk fibroin (SF) possesses several characteristics that are favorable for tissue engineering. However, the mechanical properties must be modified in some cases. For instance, soft tissues such as those of the circulatory system are more elastic than tissue-engineered materials. The development of polymer blends is a simple method with the potential to provide materials with extended useful properties. In this study, we developed a non-woven SF and thermoplastic polyurethane-blend sheet from a polymer solution. The structure and miscibility of the blend sheet was evaluated using solid-state nuclear magnetic resonance (NMR) methods. In the 13C cross-polarization and magic angle spinning NMR spectra, no peak shift was observed between the pure and blended samples. The miscibility of the sample was investigated using proton spin-lattice relaxation times in the laboratory frame (T1H). The T1H measurement clearly revealed that the molecular chains of SF and Pellethane exist in close proximity of several tens of nanometers. The development of polymer blends is a simple method with the potential to provide materials with extended useful properties. Here, the SF and Pellethane were observed to be highly miscible with each other even though SF maintained the strong β-sheet crystal structure. This result suggests that SF/Pellethane-blended sheets possess strength that is derived from SF and elasticity that is derived from Pellethane. Therefore, this blended sheet should be a good medical material for soft tissue engineering.

Calcium-Induced Sculpturing of the Plasma Membrane: Lipid Microclusters Cast by Anionic Lipids

The plasma membrane of the cell is a complex, tightly-controlled heterogeneous environment. While anionic lipids constitute a small part of all phospholipids in the plasma membrane, they play key functional roles in regulation of vital cellular processes such as blood clotting, signaling, vesicle fusion, and apoptosis. Lipid composition and distribution in the plasma membrane are highly dynamic, with anionic phosphatidylserine (PS) lipids typically found on the interior leaflet. In turn, the concentration of divalent Ca2+ ions, an important cellular messenger, is three orders of magnitude greater outside of the cell, spatially separating the ions from anionic lipids. PS lipids can become externalized to the outer leaflet of the plasma membrane in the case of cell injury, disease, or apoptotic changes allowing them to interact with Ca2+, resulting in changes in the plasma membrane structure and initiation of signaling cascades. Nonetheless, the molecular details of lipid-Ca2+ interactions are not completely understood. We performed molecular dynamics simulations of binary mixtures of PS and phosphatidylcholine (PC) lipids using highly mobile membrane mimetic model (HMMM) that enabled extended sampling. Simulations revealed that lipid microclusters are formed by higher order (three or more) lipid oligomers coordinated by Ca2+, with two distinct conformations of the PS headgroup serving as building blocks. In parallel, 13C-dephased 31P-observed solid-state nuclear magnetic resonance (SSNMR) rotational-echo double-resonance (REDOR) experiments were performed with spin-diluted Nanodisc samples to report on 31P-13C distances. Experimental data are consistent with both intra- and inter-molecular lipid headgroup characteristic distances of approximately 4.8 +/- 0.5 A that match well with all-atom MD results. To our knowledge, this is one of the first joint MD and high-resolution SSNMR studies to characterize how lipid microclusters are formed at the atomic level and how they reshape the plasma membrane.

How High Concentrations of Proteins Stabilize the Amorphous State of Calcium Orthophosphate: A Solid-State Nuclear Magnetic Resonance (NMR) Study of the Casein Case.

Understanding how proteins stabilize amorphous calcium ortho-phosphate (ACP) phases is of great importance in biology and for pharmaceutical or food applications. Until now, most of the former investigations about ACP-protein stability and equilibrium were performed under conditions where ACP colloidal nanoclusters are surrounded by low to moderate concentrations of peptides or proteins (15-30 g L-1). As a result, the question of ACP-protein interactions in highly concentrated protein systems has clearly been overlooked, whereas it corresponds to actual industrial conditions such as drying or membrane filtration in the dairy industry for instance. In this study, the structure of an ACP phase is monitored in association with one model phosphorylated protein (casein) using solid-state nuclear magnetic resonance (ssNMR) under two conditions of high protein concentration (300 and 400 g L-1). At both concentrations and at 25 °C, it is found that the caseins maintain the mineral phase in an amorphous form with no detectable influence on its structure or size. Interestingly, and in both cases, a significant amount of the nonphosphorylated side chains interacts with ACP through hydrogen bonds. The number of these interacting side chains is found to be higher at the highest casein concentration. At 45 °C, which is a destabilizing temperature of ACP under protein-free conditions, the amorphous structure of the mineral phase is partially transformed at a casein concentration of 300 g L-1, while it remains almost intact at a casein concentration of 400 g L-1. Therefore, these results clearly indicate that increasing the concentration of proteins favors ACP-protein interactions and stabilizes the ACP clusters more efficiently.

Structure of Chemisorbed CO(2) Species in Amine-Functionalized Mesoporous Silicas Studied by Solid-State NMR and Computer Modeling.

Two-dimensional (2D) solid-state nuclear magnetic resonance (SSNMR) experiments on samples loaded with 13C-labeled CO2, "under controlled partial pressures", have been performed in this work, revealing unprecedented structural details about the formation of CO2 adducts from its reaction with various amine-functionalized SBA-15 containing amines having distinct steric hindrances (e.g., primary, secondary) and similar loadings. Three chemisorbed CO2 species were identified by NMR from distinct carbonyl environments resonating at δC ≈ 153, 160, and 164 ppm. The newly reported chemisorbed CO2 species at δC ≈ 153 ppm was found to be extremely moisture dependent. A comprehensive 1H-based SSNMR study [1D 1H and 2D 1H-X heteronuclear correlation (HETCOR, X = 13C, 29Si) experiments] was performed on samples subjected to different treatments. It was found that all chemisorbed CO2 species are involved in hydrogen bonds (HBs) with either surface silanols or neighboring alkylamines. 1H chemical shifts up to 11.8 ppm revealed that certain chemisorbed CO2 species are engaged in very strong HBs. We effectively demonstrate that NMR may help in discriminating among free and hydrogen-bonded functional groups. 13C{14N} dipolar-recoupling NMR showed that the formation of carbonate or bicarbonate is excluded. Density functional theory calculations on models of alkylamines grafted into the silica surface assisted the 1H/13C assignments and validated various HB arrangements that may occur upon formation of carbamic acid. This work extends the understanding of the chemisorbed CO2 structures that are formed upon bonding of CO2 with surface amines and readily released from the surface by pressure swing.

Solid-state NMR study on changes of phosphate and proton species in metal pyrophosphate composite (MP2 O7 -MO2 ) ceramics.

In order to investigate the effects of composite production and the role of the counter cation for metal phosphate conductors, changes in the solid-state nuclear magnetic resonance (NMR) spectra and magnetic relaxation times caused by the removal of volatile products and water washing were examined for various metal pyrophosphate (MP2 O7 -MO2 ; M = Sn, Si, Ti, and Zr). Acidic species could be detected by 1 H MAS NMR spectra for all the composites except ZrP2 O7 -ZrO2 that had the lowest conductivity. The 31 P DD-MAS NMR spectra for MP2 O7 -MO2 composites showed different signal patterns depending on the counter cations participating in the ion exchange as a result of different microstructures. Combinational analysis of 31 P DD-MAS and 31 P CP-MAS NMR spectra of the composites indicated that protonic bulk phosphates were observed at slightly lower fields than non-protonic bulk phosphates in all of the MP2 O7 -MO2 composites. After water washing, the acidic species and the protonic bulk phosphates of MP2 O7 -MO2 composites disappeared or were reduced to trace amounts. The T1 H values of the water-washed composites lengthened because of removal of orthophosphoric acid, although the T1 P values remained almost unchanged. The results of the solid-state NMR studies suggest that the protonic bulk phosphates of MP2 O7 -MO2 composites do not generally distribute in the bulk but exist in the interface between excess H3 PO4 and the bulk. Copyright © 2016 John Wiley & Sons, Ltd.

Structural evolution of turbostratic carbon: Implications in H2 storage

Structural evolution of turbostratic carbon samples as a function of annealing temperature has been investigated in detail using small angle X-ray scattering (SAXS), solid state nuclear magnetic resonance (NMR) and Raman spectroscopic techniques. From these studies, it is established that, samples heated at lower temperatures (700 °C and 800 °C) consist carbon particles with rough surfaces forming structure of surface fractal in nature. Whereas the sample heated at higher temperature (900 °C) consists of larger clusters with nearly smooth surface as well as smaller size particles forming dense mass fractal structure. For this sample, solid state NMR and Raman Spectroscopic studies indicate an increased extent of overlapping of 2pz orbital of carbon atoms due to improved long range ordering and clustering. Hydrogen adsorption studies further substantiated that energetically more homogeneous surface exists for particles of 900 °C heated sample as compared to those of 700 °C and 800 °C heated samples. A highest hydrogen storage capacity of 0.152 H/M has been observed at 123 K and 45 bar pressure for the sample heated at 900 °C.

Chemical nature of humic substances in two typical Chinese soils (upland vs paddy soil): A comparative advanced solid state NMR study

Knowledge of the structural features of humic substances (HSs) is essential for elucidating the mechanisms of humification in different soil environments and realizing their profound roles in environmental issues. The aim of this work was to investigate the chemical structures of fulvic acid (FA), humic acid (HA) and humin (HM) fractions isolated from an upland soil (Fluvisol) and a paddy soil (Anthrosol) typical in China using advanced solid-state 13C nuclear magnetic resonance (NMR) techniques. The results revealed that there were great structural differences of HSs between the two soils. The two FAs showed distinct quantitative differences in aliphatics with more polysaccharides in the FA from the upland soil than from the paddy soil. The HM from the upland soil differed from the paddy soil HM in having more proteins/peptides (23% vs 20%), total aromatics (21% vs 12%) as well as fewer lipids (24% vs 35%) and polysaccharides (27% vs 31%). The HM fractions represented the most different components of organic matter between the two soils. The degree of difference between the two HAs fell in between that of FAs and HM fractions. In particular, the HA from the upland soil had relatively greater degree of aromaticity. Our study indicated that the upland soil exhibited a higher degree of humification compared with the paddy soil. Among the three humic fractions, the FAs featured COO/N-CO groups, and the HAs were more enriched in protonated aromatic C for both soils. In contrast, the two HM fractions contained more O-alkyl C and fewer aromatics than did the other humic fractions, being closer to the original organic materials in soils. We speculate that the evolutionary route of HSs is likely to be the transformation of original organic materials into HM, followed by increased degradation, further oxidization and conversion into HA, and then into FA.

Direct Evidence of Chelated Geometry of Catechol on TiO2 by a Combined Solid-State NMR and DFT Study

Catechol on TiO2 is a model system for a class of molecules that bind and interact very strongly with metal oxides. This interaction gives rise to a marked charge-transfer absorption band that can be used to sensitize the complex to visible light. In solar cells, these are called type II sensitizers in contrast with type I sensitizers where an excitation of the molecule with subsequent charge injection is the main mechanism for placing an electron in the conduction band of the semiconductor. The adsorption geometry of these molecules is critical in their functioning. Nuclear magnetic resonance (NMR) spectroscopic methods can be used to elucidate structural information about the local geometry at the substrate–molecule interface. NMR methods coupled with density functional theory (DFT) allow for the detailed characterization of molecular binding modes. In the present work, we report a solid-state NMR and DFT study of catechol on TiO2. DFT-GIPAW chemical shift predictions for the 13C CP-MAS experiments unam...

Quantitative NEXAFS and solid-state NMR studies of sp3/(sp2 + sp3) ratio in the hydrogenated DLC films

The classification of diamond-like carbon (DLC) films is imperative in guiding large-scale industrial productions. However, it is not easy to classify this issue based on the structural composition and obtained properties, especially, when the film contains a certain amount of hydrogen. In the present study, two types of hydrogenated DLC films were prepared by electron-cyclotron-resonance chemical-vapor-deposition method with pure C2H2 and Ar gasses with applied negative bias voltages of 0 and 0.5kV. The structural and surface analyses of these films have shown significant changes of physical and mechanical properties with high reproducibility and low oxygen contents. The comparison of H/C atomic ratio extracted from the combination of Rutherford backscattering and elastic recoil detection analysis and the solid-state nuclear magnetic resonance (NMR) illustrated that the NMR analysis of the present work provides a significant contribution. Therefore, we compared quantitatively the sp3/(sp2+sp3) ratios in the hydrogenated DLC films using the near-edge X-ray absorption fine-structure (NEXAFS) and solid-state NMR methods. The signals of hydrocarbon sp3 (CH, CH2 and CH3) and a network of sp3 hybridized carbon (C-sp3) can be separated by the solid-state 13C NMR measurement, from which it is concluded that the former do not enable a detailed interpretation for the internal structural changes of the hydrogenated DLC films with the increase of applied bias voltage.

Multidimensional Solid-State Nuclear Magnetic Resonance of a Functional Multiprotein Chemoreceptor Array.

The bacterial chemoreceptor complex governs signal detection and the upstream elements of chemotactic behavior, but the detailed molecular mechanism is still unclear. We have assembled nativelike functional arrays of an aspartate receptor cytoplasmic fragment (CF) with its two cytoplasmic protein partners (CheA and CheW) for solid-state nuclear magnetic resonance (NMR) studies of structural changes involved in signaling. In this initial study of the uniformly (13)C- and (15)N-enriched CF in these >13.8 MDa size arrays, residue-type assignments are made for amino acids that together make up 90% of the protein. We demonstrate that homo- and heteronuclear two-dimensional spectra are consistent with structure-based chemical shift predictions: a number of major assignable correlations are consistent with the predominantly α-helical secondary structure, and minor correlations are consistent with the disordered C-terminal tail. Sub-parts per million line widths and spectral changes upon freezing of samples suggest these arrays are structurally homogeneous and sufficiently immobilized for efficient solid-state NMR.

Conformational Analysis of Oxygen-Induced Higher Ordered Structure of A, B-Alternating Poly(arylene vinylene) Copolymers by Solid-State NMR and Molecular Dynamics Simulations

Two types of poly(arylene vinylene) copolymer derivatives, one containing heptoxy side chains and the other containing octyl side chains, are investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulation in order to understand the effect of the chemical structure of the side chains on the molecular packing structure and the charge transport properties. Solid-state NMR study shows that octyl-functionalized polymer has higher side chain mobility, indicating a higher degree of molecular stacking disorder than heptoxy-functionalized polymer. MD simulations suggest that these differences in molecular packing and mobility are associated with the different side chain geometry. Overall, we demonstrate how the new poly(arylene vinylene) copolymer derivatives with a small change in polymer side chain (alkyl vs alkoxy) lead to large changes in the molecular packing arrangement and thereby the improved hole mobility in organic thin-film transistors.

On the molecular dynamics in long-acting calcium channel blocker lacidipine: solid-state NMR, neutron scattering and periodic DFT study

A new-generation lipophilic calcium channel blocker lacidipine (LCDP) has been thoroughly explored by combining solid-state nuclear magnetic resonance (NMR) with high-flux quasi-elastic (QENS) and inelastic neutron scattering (INS) experiments.

Solid state NMR studies of gels derived from low molecular mass gelators.

Since its invention more than six decades ago, nuclear magnetic resonance (NMR) spectroscopy has evolved as an inevitable part of chemical as well as structural analysis of small molecules, polymers, biomaterials and hybrid materials. In the solution state, due to the increased viscosity of complex viscoelastic fluids such as gels, liquid crystals and other soft materials, the rate of molecular tumbling is reduced, which in turn affects the chemical shift anisotropy, dipolar and quadrupolar interactions. As a consequence the solution state NMR spectra show broad lines, and therefore, extracting detailed structural information is a challenging task. In this context, solid state (SS) NMR has the ability to distinguish between a minute amount of polymorphic forms, conformational changes, and the number of non-equivalent molecules in an asymmetric unit of a crystal lattice, and to provide both qualitative as well as quantitative analytical data with a short-range order. Therefore, SS NMR has continued to evolve as an indispensable tool for structural analysis and gave birth to a new field called NMR crystallography. Solid state cross polarization (CP) and high resolution (HR) magic angle spinning (MAS) NMR spectroscopy has been used to study weak interactions in polymer gels. However, the application of SS NMR spectroscopy to study gels derived from low molecular weight gelators has been limited until recently. In this review, we will focus on the importance of solid state NMR spectroscopy in understanding and elucidating the structure of supramolecular gels derived from low molecular weight gelators with selected examples.

Mechanochemical Production of Halogen-Bonded Solids Featuring P═O···I–C Motifs and Characterization via X-ray Diffraction, Solid-State Multinuclear Magnetic Resonance, and Density Functional Theory

A series of phosphine oxide-iodofluorobenzene cocrystals featuring relatively strongly halogen-bonded P═O···I–C motifs has been prepared mechanochemically and characterized by 31P and 17O solid-state nuclear magnetic resonance (SSNMR) spectroscopy and single-crystal X-ray diffraction. Direct insights were obtained into the correlation between several NMR observables (chemical shift tensors, electric field gradient tensors, and J(31P, 17O) coupling) and the molecular and electronic structure of the halogen bonds. The 31P isotropic chemical shift and span, the 17O quadrupolar coupling constant and asymmetry parameter, as well as J(31P, 17O) coupling can be strong indicators of the presence of a halogen bond. Density functional theory calculations using periodic boundary conditions have revealed several notable trends. For example, the oxygen isotropic chemical shift and J(31P, 17O) values were found to correlate linearly with the strength of the halogen bond. An additional natural localized molecular orbital (NLMO) investigation shows that the three main contributions to J(31P, 17O) coupling are the P═O bonding orbitals, the oxygen lone pair orbital, and oxygen core orbitals, and that they all together determine the overall trend observed experimentally. Further NLMO analysis revealed a linear correlation between the contribution of the oxygen pz lone pair orbital to the quadrupolar coupling constant and the strength of the halogen bond. This work, encompassing the first 17O SSNMR studies of halogen bonds, demonstrates how NMR observables provide a useful means to characterize halogen bonds and also improve our understanding of the correlation between the electronic structure of the halogen bond and NMR properties.

A 2H magic-angle spinning solid-state NMR characterisation of lipid membranes in intact bacteria

This work proposes a new approach to characterize cell membranes in intact cells by 2H solid-state nuclear magnetic resonance (NMR) in only a few hours using magic-angle spinning (MAS) and spectral moment analysis. The method was first validated on model dipalmitoylphosphatidylcholine (DPPC) membranes, allowing the detection of lipid fluctuations below the main transition temperature. Then the lipid dynamics in Escherichia coli membranes was compared in bacteria grown under different diets. More specifically, deuterated palmitic acid was used to isotopically label the phospholipid acyl chains in bacteria membranes, with or without the presence of protonated oleic acid. Our results showed improved lipid fluidity when bacteria were grown in the presence of oleic acid, which helps preserving the natural fatty acid profile in E. coli membranes. The MAS 2H solid-state NMR study of membranes combined with spectral moment analysis showed to be a fast method compatible with in vivo bacterial studies, and should also be applicable to other micro-organisms to obtain molecular information on living cells by solid-state NMR.

Solid-state 13C NMR study of banana liquid crystals – 3: Alkyl-tail-group packing environments of an acute-angle bent-core molecule in the hexagonal columnar and cubic phases

Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed on the hexagonal columnar and cubic phases of an acute-angle banana-shaped molecule, N(1,7)-S30. In the hexagonal columnar phase, three peaks appear at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that the two alkyl tails have different packing structures, and one of the tails has two different conformations within a single molecule. Combined cross-polarization/magic-angle spinning and pulse saturation transfer/magic-angle spinning measurements show that one of the alkyl chains is located inside and the other is located outside the columnar structure. In the cubic phase, pulse saturation transfer/magic-angle spinning measurement shows that only one peak appears at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that both of the alkyl chains are located outside the cubic structure.