Magic Angle Spinning NMR Study Research Articles

A continuous flow strategy for the coupled transfer hydrogenation and etherification of 5-(hydroxymethyl)furfural using Lewis acid zeolites.

Hf-, Zr- and Sn-Beta zeolites effectively catalyze the coupled transfer hydrogenation and etherification of 5-(hydroxymethyl)furfural with primary and secondary alcohols into 2,5-bis(alkoxymethyl)furans, thus making it possible to generate renewable fuel additives without the use of external hydrogen sources or precious metals. Continuous flow experiments reveal nonuniform changes in the relative deactivation rates of the transfer hydrogenation and etherification reactions, which impact the observed product distribution over time. We found that the catalysts undergo a drastic deactivation for the etherification step while maintaining catalytic activity for the transfer hydrogenation step. (119) Sn and (29) Si magic angle spinning (MAS) NMR studies show that this deactivation can be attributed to changes in the local environment of the metal sites. Additional insights were gained by studying effects of various alcohols and water concentration on the catalytic reactivity.

X‐ray Absorption Near‐Edge Structure and Nuclear Magnetic Resonance Study of the Lithium–Sulfur Battery and its Components

Understanding the mechanism(s) of polysulfide formation and knowledge about the interactions of sulfur and polysulfides with a host matrix and electrolyte are essential for the development of long-cycle-life lithium-sulfur (Li-S) batteries. To achieve this goal, new analytical tools need to be developed. Herein, sulfur K-edge X-ray absorption near-edge structure (XANES) and (6,7) Li magic-angle spinning (MAS) NMR studies on a Li-S battery and its sulfur components are reported. The characterization of different stoichiometric mixtures of sulfur and lithium compounds (polysulfides), synthesized through a chemical route with all-sulfur-based components in the Li-S battery (sulfur and electrolyte), enables the understanding of changes in the batteries measured in postmortem mode and in operando mode. A detailed XANES analysis is performed on different battery components (cathode composite and separator). The relative amounts of each sulfur compound in the cathode and separator are determined precisely, according to the linear combination fit of the XANES spectra, by using reference compounds. Complementary information about the lithium species within the cathode are obtained by using (7) Li MAS NMR spectroscopy. The setup for the in operando XANES measurements can be viewed as a valuable analytical tool that can aid the understanding of the sulfur environment in Li-S batteries.

23Na magic-angle spinning and double-rotation NMR study of solid forms of sodium valproate

Sodium valproate is a pharmaceutical with applications in the treatment of epilepsy, bipolar disorder, and other ailments. Sodium valproate can exist in many hydrated and acid-stabilized forms in the solid state, and it can be difficult to obtain precise structural information about many of these. Here, we present a 13C and 23Na solid-state NMR study of several forms of sodium valproate, only one of which has been previously structurally characterized by single-crystal X-ray diffraction. 23Na magic-angle spinning (MAS), double-rotation (DOR), and multiple-quantum magic-angle spinning (MQMAS) NMR spectra are shown to provide useful information on the number of molecules in the asymmetric unit, the local coordination geometry of the sodium cations, and the presence of amorphous phases. Two previously identified forms are shown to be highly similar, or identical, according to the 23Na NMR data. The utility of carrying out both DOR and MQMAS NMR experiments to identify all crystallographically unique sites is demonstrated. 13C cross-polarization MAS NMR spectra also provide complementary information on the number of molecules in the asymmetric unit and the crystallinity of the sample.

HR-MAS NMR reveals a pH-dependent LPS alteration by de-O-acetylation at abequose in the O-antigen of Salmonella enterica serovar Typhimurium

NMR spectroscopy can detect biomolecules like lipopolysaccharide directly on the surface of the cell, thus avoiding isolation and purification, and providing a more realistic description than the one derived from in vitro studies. Here we present a high-resolution magic-angle spinning NMR study of the O-antigen of Salmonella enterica serovar Typhimurium (S. Typhimurium) performed directly on the cells showing the alteration of its acetylation state over time. The O-antigen region of S. Typhimurium consists of the repeating unit [→2)-α-d-Manp-(1→4)-α-l-Rhap-(1→3)-α-d-Galp-(1→] where Man stands for mannose, Rha for rhamnose, and Gal for galactose. Man is substituted with abequose (Abe) O-acetylated at carbon 2. Our studies revealed that the appearance of de-O-acetylated O-antigen in the stationary growth phase is due to the de-O-acetylation of already synthesized O-acetylated O-antigen and that this reaction is caused by the metabolism-induced basic pH of the growth medium. The labile O-acetylation of the O-antigen we observed in S. Typhimurium generates non-stoichiometric O-acetylation states and therefore changes the nature of an immunogenic epitope.

Revisiting structure of silica gels from water glass: an 1H and 29Si MAS and CP-MAS NMR study

The silica gels, derived from water glass solution with pH adjusted at 3.0 and 9.9, were revisited to investigate their constitution, although water glass has been studied for last tens of decades on gelation. Solid-state nuclear magnetic resonance spectroscopy was applied to the nuclei 1H and 29Si, by the use of magic angle spinning (MAS), 1H → 29Si CP-MAS (CP: cross-polarization), and modern techniques such as 2D HETCOR (two dimensional heteronuclear correlation), and variable-contact time CP techniques. Gelation time (tgel) showed U-letter shape dependence on pH. All gels consisted of Qn groups (n: 2, 3, and 4), where Qn stands for a silicate unite [(O1/2)nSi (–O−)4−n] (n: 0–4). The analysis of the 1H → 29Si CP kinetics and 1H-29Si HETCOR spectra elucidated the presence of four kinds of 1H nuclei, i.e., those giving a peak at 6.9 ppm in chemical shift δ: 1H–OSi hydrogen bonded to H2O molecules; one at 4.3 ppm: 1H of adsorbed water molecules, hydrogen-bonded to the silanol groups; one at 1.7 ppm: 1H–OSi confined in the gel lattice, including that forming aggregations like Si–OH/NaO–Si; and one at 4.2 ppm: 1H of water molecules on the outermost hydration layer.

Magic angle spinning NMR study of interaction of N-terminal sequence of dermorphin (Tyr-d-Ala-Phe-Gly) with phospholipids

Two modifications of the Tyr-d-Ala-Phe-Gly tetrapeptide with different C-terminal groups (Tyr-d-Ala-Phe-Gly-OH 1 and Tyr-d-Ala-Phe-Gly-NH22) were investigated by various nuclear magnetic resonance sequences under magic angle spinning. The structural constraints obtained from the magic angle spinning nuclear magnetic resonance measurements suggest that both peptides are aligned on the surface of the membrane and that the sandwich-like π-CH3-π arrangement of the pharmacophore is preserved. The influence of the chemical modification of the C-terminal residue of 1 and 2 on their interaction with phosphate group of the phospholipid in the subgel phase Lc and the conformation of the peptides in the liquid crystalline phase Lα are discussed. The correlation between the X-ray structure of 1 in the solid state and 1 embedded into a membrane in the Lc phase is presented on the basis of the comparative analysis of the two‐dimensional 13C–13C dipolar-assisted rotational resonance cross-peaks and the 13C isotropic chemical shifts.

NMR Metabolomics of MTLn3E Breast Cancer Cells Identifies a Role for CXCR4 in Lipid and Choline Regulation

The alpha chemokine receptor CXCR4 is up-regulated in certain types of breast cancer. Truncation of the C-terminus of this receptor alters cell morphology and increases invasiveness and metastatic potential. Here, to better understand the effects of CXCR4 expression and truncation in breast cancer cells, we have used high resolution magic angle spinning (HR-MAS) NMR studies of rat breast carcinoma MtLn3E cells to characterize the metabolite complement of cells heterologously expressing human CXCR4 or its C-terminal truncation mutant, Δ34-CXCR4. Notable reductions in choline levels were detected when either cells expressing wild-type CXCR4 or Δ34-CXCR4 were compared with cells containing an empty expression vector. Cells expressing CXCR4-Δ34 had reduced lipid content when compared with either the wild-type CXCR4 expressing cells or those containing the empty expression vector. Taken together, our results show that distinct effects on the metabolite complement can be linked to either CXCR4 expression or CXCR4 regulation. The metabolite markers for these two effects identified in the present study can, in turn, be used to further investigate the role of CXCR4 in metastasis.

Solid-State NMR Studies of Form I of Atorvastatin Calcium

Solid-state (13)C, (19)F, and (15)N magic angle spinning NMR studies of Form I of atorvastatin calcium are reported, including chemical shift tensors of all resolvable carbon sites and fluorine sites. The complete (13)C and (19)F chemical shift assignments are given based on an extensive analysis of (13)C-(1)H HETCOR and (13)C-(19)F HETCOR results. The solid-state NMR data indicate that the asymmetric unit of this material contains two atorvastatin molecules. A possible structure of Form I of atorvastatin calcium (ATC-I), derived from solid-state NMR data and density functional theory calculations of various structures, is proposed for this important active pharmaceutical ingredient (API).

Coordination Polymers Based on [Cp*Fe(η5‐P5)]: Solid‐State Structure and MAS NMR Studies

Slow diffusion reactions of the pentaphosphaferrocene [Cp*Fe(η(5)-P(5))] (Cp*=η(5)-C(5)Me(5) (1)) with CuX (X=Cl, Br, I) in different stoichiometric ratios and solvent mixtures result in the formation of one- and two-dimensional polymeric compounds 2-6 with molecular formula [{Cu(μ-X)}{Cp*Fe(μ(3),η(5):η(1):η(1)-P(5))}](n) (X=Cl (2a), I (2'c)), [{Cu(μ-I)}{Cp*Fe(μ(3),η(5):η(1):η(1)-P(5))}](n) (3), [{CuX}{Cp*Fe(μ(4),η(5):η(1):η(1):η(1)-P(5))}](n) (X=Cl (4a), Br (4b), I (4c), Br (4'b), I (4'c)), [{Cu(3)(μ-I)(2)(μ(3)-I)}{Cp*Fe(μ(5),η(5):η(1):η(1):η(1):η(1)-P(5))}](n) (5) and [{Cu(4)(μ-X)(4)(CH(3)CN)}{Cp*Fe(μ(7),η(5):η(2):η(1):η(1):η(1):η(1):η(1)-P(5))}](n) (X=Cl (6a), Br (6b)), respectively. The polymeric compounds have been characterised by single-crystal X-ray diffraction analyses and, for selected examples, by magic angle spinning (MAS) NMR spectroscopy. The solid-state structures demonstrate the versatile coordination modes of the cyclo-P(5) ligand of 1, extending from two to five coordinating phosphorus atoms in either σ or σ-and-π fashion. In compounds 2a, 2'c and 3, two phosphorus atoms of 1 coordinate to copper atoms in a 1,2 coordination mode (2a, 2'c) and an unprecedented 1,3 coordination mode (3) to form one-dimensional polymers. Compounds 4a-c, 4'b, 4'c and 5 represent two-dimensional coordination polymers. In compounds 4, three phosphorus atoms coordinate to copper atoms in a 1,2,4 coordination mode, whereas in 5 the cyclo-P(5) ligand binds in an unprecedented 1,2,3,4 coordination mode. The crystal structures of 6a,b display a tilted tube, in which all P atoms of the cyclo-P(5) ligand are coordinated to copper atoms in σ- and π-bonding modes.

Paramagnetic interactions in the 31P NMR spectroscopy of rare earth element orthophosphate (REPO4, monazite/xenotime) solid solutions

We present the results of a variable-temperature (VT) 31P magic angle spinning NMR (MAS-NMR) study of a series of solid solutions between different synthetic rare earth (RE = Y, La, Ce, Pr, Nd, Eu, Dy) orthophosphates (REPO4) taking either the monoclinic monazite or tetragonal xenotime (zircon) crystal structure. Solid solutions were formed by mixing a small amount of a paramagnetic REPO4 material (RE = Ce, Pr, Nd, Eu, Dy) with either diamagnetic LaPO4 or YPO4, which take the monoclinic and tetragonal crystal structures, respectively. Mixtures were made with up to 10 mol% (nominal content) of the paramagnetic component. 31P spectra of these materials contained several paramagnetically shifted resonances indicating some dissolution of the paramagnetic rare earth into the host LaPO4 or YPO4 phase; however, it is clear that none of the samples studied here reached a state of complete solid solution. The use of multiple paramagnetic species in dilute solid solution with two diamagnetic materials taking different crystal structures enabled an investigation of the probable mechanisms of paramagnetic interactions in the 31P NMR experiments. A peak assignment model is introduced for the 31P spectra. Our analysis indicates that the paramagnetic interactions are dominated by the Fermi contact shift with a secondary contribution from the so-called “pseudocontact” shift.

High-pressure magic angle spinning nuclear magnetic resonance

A high-pressure magic angle spinning (MAS) NMR capability, consisting of a reusable high-pressure MAS rotor, a high-pressure rotor loading/reaction chamber for in situ sealing and re-opening of the high-pressure MAS rotor, and a MAS probe with a localized RF coil for background signal suppression, is reported. The unusual technical challenges associated with development of a reusable high-pressure MAS rotor are addressed in part by modifying standard ceramics for the rotor sleeve by abrading the internal surface at both ends of the cylinder. In this way, not only is the advantage of ceramic cylinders for withstanding very high-pressure utilized, but also plastic bushings can be glued tightly in place so that other removable plastic sealing mechanisms/components and O-rings can be mounted to create the desired high-pressure seal. Using this strategy, sealed internal pressures exceeding 150 bars have been achieved and sustained under ambient external pressure with minimal loss of pressure for 72 h. As an application example, in situ 13C MAS NMR studies of mineral carbonation reaction intermediates and final products of forsterite (Mg 2SiO 4) reacted with supercritical CO 2 and H 2O at 150 bar and 50 °C are reported, with relevance to geological sequestration of carbon dioxide.

Resonance assignments and secondary structure analysis of dynein light chain 8 by magic-angle spinning NMR spectroscopy

Dynein light chain LC8 is the smallest subunit of the dynein motor complex and has been shown to play important roles in both dynein dependent and dynein independent physiological functions via its interaction with a number of its binding partners. It has also been linked to pathogenesis including roles in viral infections and tumorigenesis. Structural information for LC8-target proteins is critical to understanding the underlying function of LC8 in these complexes. However, some LC8-target interactions are not amenable for structural characterization by conventional structural biology techniques due to their large size, low solubility and crystallization difficulties. Here, we report magic angle spinning (MAS) NMR studies of the homodimeric apo-LC8 protein as a first effort in addressing more complex, multi-partner LC8-based protein assemblies. We have established site-specific backbone and side chain resonance assignments for the majority of the residues of LC8, and show TALOS+ predicted torsion angles ϕ and ψ in close agreement with most residues in the published LC8 crystal structure. Data obtained through these studies will provide the first step toward using MAS NMR to examine the LC8 structure, which will eventually be used to investigate protein-protein interactions in larger systems, which cannot be determined by conventional structural studies.

Variable-temperature 27Al and 29Si NMR studies of synthetic forsterite and Fe-bearing Dora Maira pyrope garnet: Temperature dependence and mechanisms of paramagnetically shifted peaks

We present variable-temperature (VT, 31 to 204 °C) 29 Si magic angle spinning NMR (MAS-NMR) spectra of a synthetic forsterite containing dilute paramagnetic impurities and 27 Al and 29 Si spectra of two iron-bearing natural pyrope garnet specimens from the Dora Maira ultrahigh-pressure metamorphism locality. Previous NMR studies of these materials reported multiple “anomalous” resonances outside the range of expected frequencies. It has been hypothesized that these peaks were caused by interactions between paramagnetic centers and the resonating nuclei. Our VT MAS-NMR study shows a linear relationship between peak position and inverse temperature for the “anomalous” resonances, confirming their assignment as paramagnetic shifts. A detailed analysis of the peaks in the pyropes indicates that the “anomalous” resonances are caused by a combination of the Fermi contact and pseudocontact interactions. The paramagnetic shifts in the 29 Si spectra are likely caused by Fe 2+ in the first, second, and third nearest dodecahedral sites while those in the 27 Al spectra are likely caused by one or two Fe 2+ in the first shell dodecahedral site.

Controlled atmosphere 13C and 1H MAS NMR study of reforming route of methane with carbon dioxide over Rh/SBA-15

The mechanism of methane reforming with carbon dioxide over 1.0 wt.% Rh/SBA-15 catalyst has been studied by the 13C and 1H magic-angle spinning (MAS) NMR spectroscopies under controlled atmosphere condition using 13CH 4 + 12CO 2 and 12CH 4 + 13CO 2 as reactants. The effect of temperature in the region of 298–1023 K on the reaction was investigated and the contents of various 13C and 1H species were obtained quantitatively by the NMR technique. When treated at 573 K, the carbon exchange between methane and carbon dioxide can be observed. With the temperature rising to 773 K, the adsorbed CH 3O* species is formed but no reforming reaction occurs. In the high temperature range of 873–1023 K, the reforming reaction was observed with concomitant appearance of the adsorbed CH 2O* species and the intensity of both CH 3O* and CH 2O* increases with increasing temperature, indicating that the decomposition of CH 3O* to CH 2O* occurs and the products of dry reforming are formed from decomposition of the adsorbed CH 2O* species.

A New Inorganic−Organic Hybrid Zinc Phosphate Prepared with l-Histidine with an Unusual Stability in Water

A new layered zinc phosphate (Mu-39) has been synthesized by hydrothermal treatment with biomolecules as original templates. It was synthesized with the l-histidine amino acid (C6H9N3O2). The structure was determined by a single crystal X-ray diffraction study combined with exhaustive solid-state NMR experiments. These last ones [1H → 13C HETCOR, 1H single quantum/double quantum (DQ), 31P, 1H → 31P CPMAS, 1H → 31P HETCOR] ascertained the formulation of Mu-39 as {[C6H10N3O2+][Zn2(HPO4)(PO4)−]·H2O}n with a hydrogen phosphate and phosphate ligands, and ruled out partial protonation such as (H1−xPO4)(HxPO4). A 31P magic angle spinning (MAS) NMR study supported the almost complete racemization of l-histidine during the hydrothermal synthesis with only a small enantiomeric excess of 25% remaining. The compound crystallizes in the triclinic symmetry (space group P1) with a = 8.6109(6) A, b = 9.0319(6) A, c = 9.9523(7) A, and α = 84.481(2)°, β = 83.279(2)°, γ = 74.652(2)°, V = 739.56(9) A3, Z = 2. The inorganic ...

Magic angle spinning NMR analysis of beta2-microglobulin amyloid fibrils in two distinct morphologies.

Beta(2)-microglobulin (beta(2)m) is the major structural component of amyloid fibrils deposited in a condition known as dialysis-related amyloidosis. Despite numerous studies that have elucidated important aspects of the fibril formation process in vitro, and a magic angle spinning (MAS) NMR study of the fibrils formed by a small peptide fragment, structural details of beta(2)m fibrils formed by the full-length 99-residue protein are largely unknown. Here, we present a site-specific MAS NMR analysis of fibrils formed by the full-length beta(2)m protein and compare spectra of fibrils prepared under two different conditions. Specifically, long straight (LS) fibrils are formed at pH 2.5, while a very different morphology denoted as worm-like (WL) fibrils is observed in preparations at pH 3.6. High-resolution MAS NMR spectra have allowed us to obtain (13)C and (15)N resonance assignments for 64 residues of beta(2)m in LS fibrils, including part of the highly mobile N-terminus. Approximately 25 residues did not yield observable signals. Chemical shift analysis of the sequentially assigned residues indicates that these fibrils contain an extensive beta-sheet core organized in a non-native manner, with a trans-P32 conformation. In contrast, WL fibrils exhibit more extensive dynamics and appear to have a smaller beta-sheet core than LS fibrils, although both cores seem to share some common elements. Our results suggest that the distinct macroscopic morphological features observed for the two types of fibrils result from variations in structure and dynamics at the molecular level.

Evidence for the co-existence of distorted tetrahedral and trigonal bipyramidal aluminium sites in SrAl 12O 19 from 27Al NMR studies

Strontium aluminate, SrAl 12O 19, is a ceramic material having the hexagonal magnetoplumbite-type structure, with multiple Al coordination environments. An earlier low-field 27Al solid-state NMR study reported five different Al sites in this system: one AlO 4, one AlO 5, and three AlO 6 sites; whereas a later high-field study showed that the AlO 5 site is a distorted AlO 4 site with a very large quadrupolar coupling constant ( ∼ 20 MHz). Our magic angle spinning (MAS) and 3-quantum magic angle spinning (3QMAS) NMR studies at 7.05 T unambiguously show evidence for an AlO 5 site. However, evidence for the presence of a distorted AlO 4 site is obtained from studies at high fields (16.4 and 17.6 T), in addition to the AlO 5 site. Thus the present solid-state NMR studies give evidence for the simultaneous presence of both the five-coordinated and distorted four-coordinated sites in this system.

Soft−Hard Acid−Base Interactions: Probing Coordination Preferences of Sulfur and Selenium in Mixed Chalcophosphates in the Family APbPS4−xSex(A = K, Rb, Cs;x= 0−4)

The synthesis and structures of the three new compounds, KPbPS(1.84)Se(2.16) (1), RbPbPS(1.56)Se(2.43) (2), and CsPbPS(3.46)Se(0.54) (3), are reported. The solid state structures of 1-3 consist of two-dimensional layers of [PbP(S/Se)(4)] separated by alkali metal ions. The structure of 1 was solved in the orthorhombic space group Pna2(1). Compounds 2 and 3 possess the CsSmGeS(4) structure type, crystallizing in the orthorhombic space group P2(1)2(1)2(1). All compounds were refined as racemic twins. All chalcogen sites around the tetrahedrally coordinated P atoms show mixed S/Se occupancy; however, there is a preference for Se binding to Pb ions and S binding to alkali ions. A (31)P magic angle spinning NMR study on 1 suggests that, in mixed seleno-/thiophosphates, all of the anions [PS(x)Se(4-x)](3-) (x = 0, 1, 2, 3, 4) are present. The different amount of sulfur and selenium present in KPbPS(1.84)Se(2.16) (1), RbPbPS(1.56)Se(2.43) (2), and CsPbPS(3.46)Se(0.54) (3) is reflected in the solid state absorption spectra from which bandgaps of 2.2 eV were determined for 1 and 2, and a blue-shift to 2.5 eV was observed because of the higher sulfur-content in 3. Thermogravimetric analysis experiments indicated that, upon heating, compound 1 decomposes forming PbSe and sulfur together with other unidentified products. A Raman spectrum of compound 1 showed more bands than are usually observed in seleno- or thiophosphate salts and is another indicator of the mixed seleno-/thiophosphate anions found in 1.

Microcrystalline Hexagonal Tungsten Bronze. 2. Dehydration Dynamics

Low-temperature (25-600 degrees C) thermal transformations have been studied for hydrothermally prepared, microcrystalline hexagonal tungsten bronze (HTB) phases A(x)WO(3+x/2).zH(2)O as a function of temperature, where A is an exchangeable cation (in this case Na(+) or Cs(+)) located in hexagonal structural tunnels. Thermal treatment of the as-prepared sodium- and cesium-exchanged phases in air were monitored using a conventional laboratory-based X-ray diffractometer, while thermal transformations in vacuum were studied using synchrotron X-ray and neutron diffraction. Concurrent thermogravimetric, diffuse reflectance infrared (DRIFT), and (23)Na and (133)Cs magic angle spinning (MAS) NMR spectroscopic studies have also been undertaken. For the cesium variant, cell volume contraction occurred from room temperature to about 350 degrees C, the regime in which water was "squeezed" out of tunnel sites. This was followed by a lattice expansion in the 350-600 degrees C temperature range. Over the entire temperature range, a net thermal contraction was observed, and this was the result of an anisotropic change in the cell dimensions which included a shortening of the A-O2 bond length. These changes explain why Cs(+) ions are locked into tunnel positions at temperatures as low as 400 degrees C, subsequently inducing a significant reduction in Cs(+) extractability under low pH (nitric acid) conditions. The changing Cs(+) speciation as detected by (133)Cs MAS NMR showed a condensation from multiple Cs sites, presumably associated with differing modes of Cs(+) hydration in the tunnels, to a single Cs(+) environment upon thermal transformation and water removal. While similar lattice contraction was observed for the as-prepared sodium variant, the smaller radius of Na(+) caused it to be relatively easily removed with acid in comparison to the Cs(+) variant. From (23)Na MAS NMR studies of the parent material, complex Na(+) speciation was observed with dehydrated and various hydrated Na(+) species being identified, and a subsequent dynamic interchange within this speciation was observed upon thermal treatment.

A Dynamic Magic Angle Spinning NMR Study of the Local Mobility of Alanine in an Aqueous Environment at the Inner Surface of Mesoporous Materials

Dynamic deuterium magic angle spinning NMR has been applied to study the slow motion of small molecules close to a silica surface. In particular, alanine-d(3) molecules dissolved in an aqueous solution were loaded into the pores of the mesoporous materials SBA-15 and MCM-41. Deuterium spectra were measured as a function of the water content of these materials and the temperature. From the analysis of these spectra and the corresponding proton spectra, using a simple molecular exchange model, relatively slow desorption rates of the binding of alanine to the inner pore surface were obtained and were correlated with the low proton concentrations at the pore surfaces.