Deuterium NMR Study Research Articles

Structure and Dynamics in Alkanethiolate Monolayers Self-Assembled on Gold Nanoparticles: A DSC, FT-IR, and Deuterium NMR Study

Gold nanoparticles, ca. 30 Å in diameter, have been derivatized with specifically deuterated (position 1 and positions 10 to 13) and perdeuterated (positions 2 to 18) octadecanethiols (C18SH). The phase behavior of the octadecanethiolate monolayers chemisorbed onto the colloidal gold surface was characterized by differential scanning calorimetry (DSC). The DSC thermograms show that the C18SH-derivatized Au nanoparticles undergo distinct phase transitions which can be associated with the reversible disordering of the alkyl chains. Despite the highly curved geometry of these Au particles, there is a remarkable degree of conformational order in the alkanethiolate chains and the thermotropic behavior of the thiol-modified gold nanoparticles is very similar to that of conventional, planar self-assembled monolayers. Both the peak maximum temperature and the enthalpy associated with the DSC transition strongly parallel those of the gel-to-liquid crystalline transition of n-diacylphosphatidylcholine lipid bilayer membranes of equivalent chain length. Restricted chain mobility due to covalent bonding of the sulfur head group to the gold surface does not affect the cooperativity of the transition in terms of the transition temperature and enthalpy. Local chain ordering and dynamics in the deuterated C18S/Au nanoparticles have been probed using variable-temperature solid-state deuterium NMR spectroscopy and transmission FT-IR spectroscopy. The temperature dependence of the symmetric CD2 stretching frequency has confirmed that the DSC-detected phase transition involves a thermally-induced change from a predominantly all-trans conformation to a chain disordered state. A comparison of the thermal behavior of d35-C18S/Au and 10,10,11,11,12,12,13,13-d8-C18S/Au shows that disordering originates in the chain terminus region and propagates toward the middle of the chain as the temperature increases. Studies of 1,1-d2-C18S/Au show that the disorder does not extend to the tethered sulfur head group. Deuterium NMR spectroscopy specifically establishes that chain melting arises from an increased frequency of gauche bonds in the alkanethiolate chains. The 2H NMR line shapes further indicate that the tethered alkanethiolate chains are undergoing rapid trans-gauche bond isomerization and axial chain rotation.

Dynamics of trimethoprim bound to dihydrofolate reductase—a deuterium NMR study

We have employed deuterium NMR techniques to determine the dynamics of trimethoprim (TMP) in a binary complex with dihydrofolate reductase (DHFR) or in a ternary complex with DHFR and cofactor NADP + in the fully hydrated state. TMP was deuterated at the following positions: (2′,6′-D 2)TMP, (3′-Ome-D 3)TMP and (3′,4′-Ome-D 6)TMP. Dynamics of TMP were deduced from lineshape simulation and relaxation measurements of the deuterium NMR powder spectra of the three samples obtained at various temperatures. The results showed that in the polycrystalline state the TMP molecule is very rigid. The only detectable motion is the methyl group rotation at a rate of 10 10 s −1 at 25 °C, as determined from simulation of the partially relaxed powder patterns. When bound to DHFR a residual deuterium quadrupole splitting of 140 kHz was observed for (2′,6′-D 2)TMP at temperatures up to 30 °C, suggesting that the benzyl ring in the bound state is also very rigid. In contrast, in the binary complex with DHFR the methoxyl groups of TMP undergo librational motion of 10 7 s −1 about the C 3O bond at an amplitude of 54 ° for the meta methoxyl group and about the C 4O bond at an amplitude of 70 ° and similar rate for the para methoxyl group at 30 °C. The presence of the cofactor, NADP +, appears to tighten up the binding pocket such that the motion freedom of TMP is more restricted. The rigidity of TMP in a protein complex as revealed by our deuterium NMR results is in accord with the tight binding of TMP to DHFR.

Nematic ordering in porous glasses: A deuterium NMR study.

A deuterium NMR study of the pentylcyanobiphenyl liquid crystal confined to a controlled pore glass matrix with pore radii of 12, 150, and 200 nm was performed. In the 12-nm sample the nematic to isotropic transition is gradual. In the nematic phase the absorption spectrum is substantially narrowed due to translational diffusion of nematic molecules, which is effective because of the inhomogeneous nematic ordering. The external magnetic field influence is negligible. The onset of nematic ordering is bulklike in the 150- and 200-nm samples. There, the absorption spectrum is strongly affected by the external magnetic field. The 150-nm sample exhibits memory effects depending on history of temperature and external field changes.

Dynamics of the three methionyl side chains of Streptomyces subtilisin inhibitor. Deuterium NMR studies in solution and in the solid state.

Streptomyces subtilisin inhibitor (SSI) contains three methionine residues in a subunit: two (at positions 73 and 70) in the crucial enzyme-recognition sites P1 and P4, respectively, and one (Met 103) in the hydrophobic core. The motions of the side chains of these three Met residues and the changes in mobility on binding with subtilisin were studied by deuterium NMR spectroscopy in solution and in crystalline and powder solids. For this purpose, the wild-type SSI was deuterium-labeled at the methyl groups of all three Met residues, and three artificial mutant proteins were labeled at only one specific Met methyl group each. In solution, for methionines 73 and 70, the effective correlation times were only 0.8-1.0 x 10(-10)s indicating that the two side chains on the surface fluctuate almost freely. On formation of a complex with subtilisin, however, these high mobilities were quenched, giving a correlation time of 1.1 x 10(-8)s for the side chains of methionines 70 and 73. The correlation time of Met 103, located in the hydrophobic core, was at least 1.0 x 10(-8)s in free SSI, showing that its side chain motion is highly restricted. The nature of the internal motions of the three Met side chains was examined in more detail by deuterium NMR spectroscopy of powder and crystalline samples. The spectral patterns of the powder samples depended critically on hydration: immediately after lyophilization, the side-chain motions of the three Met residues were nearly quenched. With gradual hydration to 0.20 gram of water per gram protein-water, the orientational fluctuation of the methyl axes of methionines 70 and 73 was selectively enhanced in both amplitude and frequency (to about 1 MHz) and, at nearly saturating hydration (0.60 gram of water per gram protein-water), became extremely high in amplitude and frequency (> 10 MHz). In contrast, the polycrystalline wild-type SSI spectrum showed fine structures, reflecting characteristic motions of the Met side chains. The polycrystalline spectrum could be reproduced reasonably well by the same motion models and parameters used to simulate the powder spectrum at the final level of hydration, suggesting that the side-chain motions are similar in the fully hydrated powder and in crystals. Spin-lattice relaxation measurements gave evidence that, even in crystals, the methyl axes of all three Met residues undergo rapid motions with correlation times between 10(-8) and 10(-10)s, comparable to the correlation times in solution. Finally, in the hydrated stoichiometric complex of SSI with subtilisin BPN' in the solid state, large-amplitude motions are absent, but the side chains of methionines 70 and/or 73 are likely to have small-amplitude motions.

Deuterium NMR Studies of Water in Oriented Nylon 6 Fibers

Deuterium NMR studies of drawn nylon 6 fibers hydrated with D2O suggest the presence of three types of water and two classes of exchangeable protons. The water exhibits varying degrees of residual orientational order (incompletely averaged quadrupolar interactions) as well as drying characteristics that enable a comparison with interlamellar and interfibrillar water previously defined by small-angle neutron scattering.1 The interfibrillar water is bound the strongest and exhibits the largest (draw-ratio-dependent) quadrupolar splitting in aligned fibers. Dry fibers (whose accessible amide protons have been deuterium exchanged with D2O) show anisotropic powder spectra. The angular dependence of these spectra suggests that two distinct classes of amide deuterons contribute to the spectra, one associated with aligned interfibrillar amorphous chains (with N−D bonds on average normal to the fiber axis) and more isotropic deuterons probably associated with chain folds and variously oriented crystallite surfaces.

Shape-Dominated Ordering in Nematic Solvents. A Deuterium NMR Study of Cycloalkane Solutes

We examine a series of closely related, relatively inert, cyclic aliphatic solutescyclohexane, methylcyclohexane, 1,1-dimethylcyclohexane, 1,4-trans-dimethylcyclohexane, 1,4-cis-dimethylcyclohexane, trans-decalin, and cis-decalinin a nematic solvent and demonstrate that their orientational ordering can be accurately described in terms of purely hard-body interactions with the solvent molecules. These interactions are treated explicitly in the context of a statistical mechanical approximation wherein the orientational correlations among the solvent molecules are not taken into account directly. We test the theory by predicting the observed order parameters of the aliphatic solutes as determined with deuterium nuclear magnetic resonance. The utility and limitations of a description of solute ordering derived exclusively from hard-body interactions is discussed.

Chain length mismatch and packing constraints of free fatty acids in a hexagonal detergent host phase. A wide line deuterium NMR study

The conformational and dynamical constraints of a series of deuterated free fatty acids with increasing chain length were studied in a hexagonal (H 1) host phase of the nonionic detergent octaethyleneglycolmono- n-dodecylether (C 12E 8) by deuterium nuclear magnetic resonance spectroscopy ( 2H-NMR). The nonionic detergent and free fatty acids ranging from decanoic to octadecanoic acid were chosen as a paradigm of the capacity of detergent micelles to solubilize lipids within a broad range of molecular weights. Segmental order parameters were obtained from the 2H-quadrupolar splittings. The parallel increase of the order parameter profiles in the plateau region indicates that slow, whole body motion of the fatty acid molecules decreases with increasing chain length. The unusual shape of the ordering profiles and the decreasing ordering of the terminal segments as the chain length increases suggest that mismatch between the average radius of the host phase and the length of the fatty acids results in chain backbending and interpenetration. Longitudinal and transverse relaxation rates R 1z and R 2, respectively, of individual chain segments were determined in order to correlate the segmental ordering with chain dynamics. The relation between R 1z and the 2H order parameters indicates that theories of molecular motion that require time-scale separation between fast segmental and slow whole body motions are not applicable in the highly curved hexagonal phase structure. The relaxation rate R 2 is related to diffusional motion of the fatty acids about the long axis of the cylindrical aggregate. Motions other than axial diffusion however, significantly contribute to R 2.

Bacteriorhodopsin: the mechanism of 2D-array formation and the structure of retinal in the protein

Bacteriorhodopsin, the light driven proton pump of the extreme halophilic bacterium H. salinarium, is an integral membrane protein ( M r ca. 26000) which forms 2D arrays in the purple membrane of the bacterium. It is this feature which has permitted the use of electron diffraction methods to resolve the protein structure to some degree of atomic detail, although the prosthetic group has not been fully resolved. However, the features which induce the protein to form these arrays have not been previously clarified. We have now shown that the protein array formation is driven by specific interaction of the protein with the charged phospholipid, phosphatidyl glycerol phosphate (or the sulphate derivative), a major (ca. 60%) lipid of the bacterial host membrane. In addition, in an effort to provide further structural information about the chromophore, retinal, of this protein, the orientation of the individual methyl groups of retinal have been determined from solid state deuterium NMR studies of the deuterated chromophore when in the protein binding site. This approach to structural resolution of the prosthetic group is ab initio, agrees with other studies on the chromophore and resolves new features of the bound retinal to a high degree (±2°) of precision. Here, these two studies on this integral membrane protein will be reviewed.

Deuterium NMR Study of Phenyl Group Motion in Glassy Polystyrene and a Blend of Polystyrene with Polyphenylene Oxide

Deuterium solid echo line shapes were measured as a function of temperature and echo delay time on glassy polystyrene and a blend of polystyrene with poly(2,6-dimethyl-1,4-phenylene oxide). The spectra were strongly temperature dependent from room temperature to the glass transition, indicating motion on the time scale of tens to hundreds of microseconds. The line shape signature of π flips is present in these spectra. The time scale and temperature range overlap the π process seen in dynamic mechanical spectroscopy on both pure polystyrene and in the blend. A quantitative interpretation of the phenyl dynamics was based on a simultaneous description of phenyl group rotation which allows for small angle jumps and π flips. A fairly broad distribution of correlation times was introduced through the use of the stretched exponential correlation function. The quantitative interpretation reinforces the time/temperature overlap of the phenyl group motion with the β process though the apparent activation energies from different approaches are difficult to compare due to the limited temperature range and the overlap with the α process

Proton and deuterium NMR studies of the glass transition in a 10% water-maltose solution

High power proton and deuterium NMR techniques are used to probe the molecular mobility of water in a 10% maltose-water system over a range of temperatures covering the viscous solution and the glassy state. It is shown that even in the glassy state, water still retains a high degree of rotational and translational mobility. A model where the water molecules diffuse in channels formed between maltose molecules is used to interpret the data.

Dynamics of the interface in a model composite system

AbstractA review of recent experiments from the authors laboratory on the dynamics of aminofunctional silane coupling agents is given. Of special emphasis are two coupling agents, aminopropylsilane (APS) and aminobutylsilane (ABS) which were deuterated in the γ‐position. These two coupling agents have similar chemical behavior, but different dynamics. Deuterium NMR studies reveal that the APS moves slower on the silica surface than ABS. The mobility of the interfacial ABS was also found to be significantly slowed when it was overcoated with a polymerized layer of bismaleimide to form a composite. When the composite was treated with water, the interfacial mobility of the ABS increased. The flexural strength of the APS treated composite was the highest compared to ABS‐treated and bulk glass in an epoxy‐glass composite.

Deuterium NMR Studies of the Local Ordering and Dynamics of Sodium Dodecyl Sulfate at the Alumina/Water Interface

Deuterium NMR Studies of the Local Ordering and Dynamics of Sodium Dodecyl Sulfate at the Alumina/Water Interface

Director fluctuations and anisotropic reorientation of a liquid crystal: A deuterium NMR study.

Director fluctuations and anisotropic reorientation of a liquid crystal: A deuterium NMR study.

Structure and packing of phosphatidylcholines in lamellar and hexagonal liquid-crystalline mixtures with a nonionic detergent: a wide-line deuterium and phosphorus-31 NMR study

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure and packing of phosphatidylcholines in lamellar and hexagonal liquid-crystalline mixtures with a nonionic detergent: a wide-line deuterium and phosphorus-31 NMR studyRobin L. Thurmond, Doerte Otten, Michael F. Brown, and Klaus BeyerCite this: J. Phys. Chem. 1994, 98, 3, 972–983Publication Date (Print):January 1, 1994Publication History Published online1 May 2002Published inissue 1 January 1994https://doi.org/10.1021/j100054a038RIGHTS & PERMISSIONSArticle Views172Altmetric-Citations39LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts

Segmental order in uniaxially strained bimodal polymer networks: a deuterium-NMR study

The segmental orientational order generated in bimodal poly(dimethylsiloxane) networks under uniaxial stress is probed using 2 H-NMR. The induced segmental order is measured either on «short» chains (M n = 3000 g /mol) or on «long» chains (M n = 25000 g/mol). The segmental orientation is very similar for both kinds of chains and decreases linearly as the volume fraction Φ L of «long» chain increases. A mean field analysis including orientational correlations between segments is developed and accounts for these observations. Additionally, this study has been carried out on twosets of samples with different crosslinkers. It shows clearly that the induced orientational order depends on the nature of the crosslinking junctions

Oblate hexaalkoxytriphenylene solutes in a prolate nematic solvent: a deuterium NMR study of alkyl chain ordering

We present deuterium NMR spectra of a series of hexaalkoxytriphenylene solutes (THEn, where n=5, 6, 7, and 8 is the number of carbons in the labeled alkoxy chains) dissolved in the calamitic solvent phase V. The observed methylene quadrupolar splitting patterns (segmental order profiles) are markedly different from those obtained in the neat columnar discotic phases of the THEn mesogens; they also differ significantly from order profiles of alkoxy chains attached to calamitic mesogens. Theoretical simulations of the spectra give the assignment of the splittings and, moreover, enable studies of the accommodation of the oblate THEn solute in the calamitic solvent's orientationally biased mean field

2H NMR studies of the effect of pulmonary surfactant SP-C on the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine headgroup: a model for transbilayer peptides in surfactant and biological membranes.

Surfactant protein C (SP-C) was isolated from solvent extracts of porcine pulmonary surfactant by gel filtration chromatography. The surfactant protein was combined with dipalmitoylphosphatidylcholine deuterated at the alpha and beta positions of the choline headgroup (DPPC-d4) Deuterium nuclear magnetic resonance spectra were collected as a function of temperature for a series of protein concentrations. The splitting of the alpha-deuteron spectrum in the liquid-crystalline phase was insensitive to temperature but decreased with increasing protein concentration. The response of headgroup conformation to protein concentration was consistent with an interaction between the lipid headgroup dipole and the net positive surface charge associated with the protein. The observed effect per charge on the alpha splitting was less than that reported for singly-charged amphiphiles [Scherer, P. G., & Seelig, J. (1989) Biochemistry 28, 7720-7728] but was similar to that obtained using a multipled-charged amphiphilic polypeptide [Roux, M., Neumann, J.-M., Hodges, R. S., Devaux, P. F., & Bloom, M. (1989) Biochemistry 28, 2313-2321]. This comparison suggests that the charges on SP-C are located near the bilayer surface. The possibility that the headgroup response is sensitive to the degree of clustering of surface charge is discussed. The beta-deuteron splitting in the liquid-crystalline phase decreased with increasing temperature but was relatively insensitive to protein concentration, suggesting that the torsion angle about the C alpha-C beta bond might be sensitive to steric interactions between the lipid headgroup and the protein.

Evidence for two pools of cholesterol in the Acholeplasma laidlawii strain B membrane: a deuterium NMR and DSC study.

Recent investigations have indicated that there exists a well-defined range of membrane hydrocarbon order compatible with good growth of the microorganism Acholeplasma laidlawii B [Monck, M., Bloom, M., Lafleur, M., Lewis, R. N. A. H., McElhaney, R. N., & Cullis, P. R. (1992) Biochemistry 31, 10037-10043]. Since cholesterol increases hydrocarbon order in membranes, it was of interest to examine the effect of cholesterol on the hydrocarbon order and growth characteristics of A. laidlawii B. Cholesterol is normally absent from A. laidlawii membranes since it is neither biosynthesized nor required for the growth or survival of the microorganism. However, cholesterol will be incorporated into the membrane if exogenously supplied to the A. laidlawii culture. For membranes prepared from cells grown in the presence of cholesterol, chemical determinations indicated cholesterol represented as much as 40 mol% of the total membrane lipid. However, 2H NMR order parameter measurements and DSC studies of the same membrane preparation suggested that cholesterol was present at significantly lower levels (approximately 10-15 mol%) in the membrane lipid bilayer. Further incorporation of cholesterol into the A. laidlawii lipid bilayer was found to occur with an increase in temperature or by lyophilization and rehydration at high temperatures, suggesting that sterol present in a separate pool in the membrane preparation could then gain access to the bilayer. 2H NMR spectra of A. laidlawii membrane preparations containing deuterium-labeled cholesterol indicate that the bulk of the cholesterol present in this separate pool is in a solid form.

Effect of glycosphingolipid fatty acid chain length on behavior in unsaturated phosphatidylcholine bilayers: A deuterium NMR study

Deuterium-labeled glycosphingolipids, N-lignoceroyl[d47]galactosylceramide (24:0 fatty acid form) and N-stearoyl[d35]galactosylceramide (18:0 fatty acid form) were prepared by partial synthesis. These probe-labeled species, differing only in the lengths of their fatty acids, were compared via 2H NMR with regard to arrangement and behavior in bilayers of the monounsaturated phospholipid 1-stearoyl-2-oleoylphosphatidylcholine (SOPC). Results were used to consider the physical significance of the great range of common acyl chain lengths that is a frequent feature of cell membrane glycosphingolipids. N-lignoceroyl[d47]- and N-stearoyl[d35]galactosylceramide were incorporated at concentrations ranging from 5 to 50 mol % into unsonicated phospholipid liposomes, and their spectra were analyzed in the range +73 to -14 degrees C. For the 18:0 fatty acid derivative, first spectral moments, M1, were calculated and plotted as a function of temperature for each sample composition. Spectral inspection for regions of phase coexistence, in conjunction with consideration of M1 curves, permitted derivation of phase diagram boundaries which were then refined using spectral subtraction techniques. The phase diagram for galactosylceramide with short fatty acid in SOPC was compared to the corresponding phase diagram for its long-chain analogue, derived previously in the same fashion [Morrow, M. R., Singh, D., Lu, D., & Grant, C. W. M. (1992) Biochim. Biophys. Acta 1106, 85-93]. The binary phase diagrams referred to above, which reflect the behavior of short- and long-chain glycolipids in a common phospholipid host matrix, displayed important similarities and differences. In fluid membranes, the behavior appeared to be remarkably alike, as reflected in superimposable fluidus curves over the concentration range studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical shift and electric field gradient tensors for the amide and carboxyl hydrogens in the model peptide N-acetyl-D,L-valine. Single-crystal deuterium NMR study

Solid-state NMR spectroscopy is well established as a method for describing molecular structure with resolution on the atomic scale. Many of the NMR observables result from anisotropic interactions between the nuclear spin and its environment. These observables can be described by second-rank tensors. For example, the eigenvalues of the traceless symmetric part of the hydrogen chemical shift (CS) tensor provide information about the strength of inter- or intramolecular hydrogen bonding. On the other hand, the eigenvectors of the deuterium electric field gradient (EFG) tensor give deuteron/proton bond directions with an accuracy rivalled only by neutron diffraction. In this paper the authors report structural information of this type for the amide and carboxyl hydrogen sites in a single crystal of the model peptide N-acetyl-D,L-valine (NAV). They use deuterium NMR to infer both the EFG and CS tensors at the amide and carboxyl hydrogen sites in NAV. Advantages of this technique over multiple-pulse proton NMR are that it works in the presence of {sup 14}N spins which are very hard to decouple from protons and that additional information in form of the EFG tensors can be derived. The change in the CS and EFG tensors upon exchange of a deuteron for amore » proton (the isotope effect) is anticipated to be very small; the effect on the CS tensors is certainly smaller than the experimental errors. NAV has served as a model peptide before in a variety of NMR studies, including those concerned with developing solid-state NMR spectroscopy as a method for determining the structure of proteins. NMR experiments on peptide or protein samples which are oriented in at least one dimension can provide important information about the three-dimensional structure of the peptide or the protein. In order to interpret the NMR data in terms of the structure of the polypeptide, the relationship of the CS and EFG tensors to the local symmetry elements of an amino acide, e.g., the peptide plane, is essential. The main purpose of this work is to investigate this relationship for the amide hydrogen CS tensor. The amide hydrogen CS tensor will also provide orientational information for peptide bonds in proteins complementary to that from the nitrogen CS and EFG tensors and the nitrogen-hydrogen heteronuclear dipole-dipole coupling which have been used previously to determine protein structures by solid-state NMR spectroscopy. This information will be particularly valuable because the amide hydrogen CS tensor is not axially symmetric. In addition, the use of the amide hydrogen CS interaction in high-field solid-state NMR experiments will increase the available resolution among peptide sites.« less