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Sample records for 1h-13c heteronuclear correlation

  1. Determination of glucan phosphorylation using heteronuclear 1H, 13C double and 1H, 13C, 31P triple-resonance NMR spectra.

    PubMed

    Schmieder, Peter; Nitschke, Felix; Steup, Martin; Mallow, Keven; Specker, Edgar

    2013-10-01

    Phosphorylation and dephosphorylation of starch and glycogen are important for their physicochemical properties and also their physiological functions. It is therefore desirable to reliably determine the phosphorylation sites. Heteronuclear multidimensional NMR-spectroscopy is in principle a straightforward analytical approach even for complex carbohydrate molecules. With heterogeneous samples from natural sources, however, the task becomes more difficult because a full assignment of the resonances of the carbohydrates is impossible to obtain. Here, we show that the combination of heteronuclear (1) H,(13) C and (1) H,(13) C,(31) P techniques and information derived from spectra of a set of reference compounds can lead to an unambiguous determination of the phosphorylation sites even in heterogeneous samples. PMID:23913630

  2. Proton-detected 3D 1H/13C/1H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-01

    A proton-detected 3D 1H/13C/1H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of 13C-1H connectivities, and proximities of 13C-1H and 1H-1H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including 1H-1H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) 1H/1H and 2D 13C/1H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of 1H-1H proximity and 13C-1H connectivity. In addition, the 2D (F1/F2) 1H/13C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of 1H-1H dipolar couplings, enables the measurement of proximities between 13C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of 1H-1H-13C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ṡ H2O ṡ HCl demonstrate the efficiency of the 3D experiment.

  3. Estimation of procyanidin/prodelphinidin and cis/trans flavanol ratios of condensed tannin fractions by 1H-13C HSQC NMR spectroscopy: Correlation with thiolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Integration of cross-peak contours of H/C-2’,6’ signals from prodelphinidin (PD) and of H/C-6’ signals from procyanidin (PC) units in 1H-13C HSQC nuclear magnetic resonance (NMR) spectra of condensed tannins yielded nuclei-adjusted PC/PD estimates that were highly correlated with PC/PD ratios obtain...

  4. Removal of t1 noise from metabolomic 2D 1H- 13C HSQC NMR spectra by Correlated Trace Denoising

    NASA Astrophysics Data System (ADS)

    Poulding, Simon; Charlton, Adrian J.; Donarski, James; Wilson, Julie C.

    2007-12-01

    The presence of t1 noise artefacts in 2D phase-cycled Heteronuclear Single Quantum Coherence (HSQC) spectra constrains the use of this experiment despite its superior sensitivity. This paper proposes a new processing algorithm, working in the frequency-domain, for reducing t1 noise. The algorithm has been developed for use in contexts, such as metabolomic studies, where existing denoising techniques cannot always be applied. Two test cases are presented that show the algorithm to be effective in improving the SNR of peaks embedded within t1 noise by a factor of more than 2, while retaining the intensity and shape of genuine peaks.

  5. 1H-13C/1H-15N Heteronuclear Dipolar Recoupling by R-Symmetry Sequences Under Fast Magic Angle Spinning for Dynamics Analysis of Biological and Organic Solids

    PubMed Central

    Hou, Guangjin; Byeon, In-Ja L.; Ahn, Jinwoo; Gronenborn, Angela M.; Polenova, Tatyana

    2011-01-01

    Fast magic angle spinning (MAS) NMR spectroscopy is becoming increasingly important in structural and dynamics studies of biological systems and inorganic materials. Superior spectral resolution due to the efficient averaging of the dipolar couplings can be attained at MAS frequencies of 40 kHz and higher with appropriate decoupling techniques, while proton detection gives rise to significant sensitivity gains, therefore making fast MAS conditions advantageous across the board compared with the conventional slow- and moderate-MAS approaches. At the same time, many of the dipolar recoupling approaches that currently constitute the basis for structural and dynamics studies of solid materials and that are designed for MAS frequencies of 20 kHz and below, fail above 30 kHz. In this report, we present an approach for 1H-13C/1H-15N heteronuclear dipolar recoupling under fast MAS conditions using R-type symmetry sequences, which is suitable even for fully protonated systems. A series of rotor-synchronized R-type symmetry pulse schemes are explored for the determination of structure and dynamics in biological and organic systems. The investigations of the performance of the various RNnv-symmetry sequences at the MAS frequency of 40 kHz experimentally and by numerical simulations on [U-13C,15N]-alanine and [U-13C,15N]-N-acetyl-valine, revealed excellent performance for sequences with high symmetry number ratio (N/2n > 2.5). Further applications of this approach are presented for two proteins, sparsely 13C/uniformly 15N enriched CAP-Gly domain of dynactin and U-13C,15N-Tyr enriched C-terminal domain of HIV-1 CA protein. 2D and 3D R1632-based DIPSHIFT experiments carried out at the MAS frequency of 40 kHz, yielded site-specific 1H-13C/1H-15N heteronuclear dipolar coupling constants for CAP-Gly and CTD CA, reporting on the dynamic behavior of these proteins on time scales of nano- to microseconds. The R-symmetry based dipolar recoupling under fast MAS is expected to find

  6. Identification of histidine tautomers in proteins by 2D 1H/13C(delta2) one-bond correlated NMR.

    PubMed

    Sudmeier, James L; Bradshaw, Elizabeth M; Haddad, Kristin E Coffman; Day, Regina M; Thalhauser, Craig J; Bullock, Peter A; Bachovchin, William W

    2003-07-16

    If the 13Cdelta2 chemical shift of neutral ("high pH") histidine is >122 ppm, primarily Ndelta1-H tautomer (2) is indicated; if it is <122 ppm, primarily Nepsilon2-H tautomer (1) is indicated. His resonances from the catalytic triad of active serine proteases, for example, are readily distinguished from those of denatured enzyme. The 13Cdelta2 chemical shifts increased by 6.2 ppm for the catalytic histidines in both alpha-lytic protease and subtilisin BPN' in raising the pH from that of imidazolium cation to that of tautomer 2. This tautomer identification method is easy to implement, requiring only bioincorporation of [U-13C] (or the more readily available [U-13C,15N])-histidine. Standard 1H/13C correlation HMQC or HSQC NMR pulse programs then yield the 13Cdelta2 chemical shifts with the benefit of high 1H sensitivity. Because of large one-bond spin-couplings (1JCH approximately 200 Hz), the method should extend to proteins having large 1H and 13C line widths, including very high molecular weights. PMID:12848537

  7. 1H-13C HSQC NMR spectroscopy for estimating procyanidin/prodelphinidin and cis/trans flavan-3-ol ratios of condensed tannin samples: correlation with thiolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Studies with a diverse array of 22 condensed tannin (CT) fractions from 9 plant species demonstrated that procyanidin/prodelphinidin (PC/PD) and cis/trans flavan-3-ol ratios can be appraised by 1H-13C HSQC NMR. The method was developed from fractions containing 44 to ~100% CT, PC/PD ratios ranging f...

  8. Model-free estimation of the effective correlation time for C-H bond reorientation in amphiphilic bilayers: 1H-13C solid-state NMR and MD simulations

    NASA Astrophysics Data System (ADS)

    Ferreira, Tiago Mendes; Ollila, O. H. Samuli; Pigliapochi, Roberta; Dabkowska, Aleksandra P.; Topgaard, Daniel

    2015-01-01

    Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 μs. The reorientational dynamics of the C-H bonds is conventionally verified by measurements of 13C or 2H nuclear magnetic resonance (NMR) longitudinal relaxation rates R1, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomically resolved model-free estimation of the C-H bond effective reorientational correlation time τe, which includes contributions from the entire range of all-atom MD timescales and that can be calculated directly from the MD trajectories. The approach is based on measurements of 13C R1 and R1ρ relaxation rates, as well as 1H-13C dipolar couplings, and is applicable to anisotropic liquid crystalline lipid or surfactant systems using a conventional solid-state NMR spectrometer and samples with natural isotopic composition. The procedure is demonstrated on a fully hydrated lamellar phase of 1-palmitoyl-2-oleoyl-phosphatidylcholine, yielding values of τe from 0.1 ns for the methyl groups in the choline moiety and at the end of the acyl chains to 3 ns for the g1 methylene group of the glycerol backbone. MD simulations performed with a widely used united-atom force-field reproduce the τe-profile of the major part of the acyl chains but underestimate the dynamics of the glycerol backbone and adjacent molecular segments. The measurement of experimental τe-profiles can be used to study subtle effects on C-H bond reorientational motions in anisotropic liquid crystals, as well as to validate the C-H bond reorientation dynamics predicted in MD simulations of amphiphilic bilayers such as lipid membranes.

  9. Structural correlations for (1)H, (13)C and (15)N NMR coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with lutidines and collidine.

    PubMed

    Pazderski, Leszek; Pawlak, Tomasz; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2010-06-01

    (1)H, (13)C and (15)N NMR studies of gold(III), palladium(II) and platinum(II) chloride complexes with dimethylpyridines (lutidines: 2,3-lutidine, 2,3lut; 2,4-lutidine, 2,4lut; 3,5-lutidine, 3,5lut; 2,6-lutidine, 2,6lut) and 2,4,6-trimethylpyridine (2,4,6-collidine, 2,4,6col) having general formulae [AuLCl(3)], trans-[PdL(2)Cl(2)] and trans-/cis-[PtL(2)Cl(2)] were performed and the respective chemical shifts (delta(1H), delta(13C), delta(15N)) reported. The deshielding of protons and carbons, as well as the shielding of nitrogens was observed. The (1)H, (13)C and (15)N NMR coordination shifts (Delta(1H) (coord), Delta(13C) (coord), Delta(15N) (coord); Delta(coord) = delta(complex) - delta(ligand)) were discussed in relation to some structural features of the title complexes, such as the type of the central atom [Au(III), Pd(II), Pt(II)], geometry (trans- or cis-), metal-nitrogen bond lengths and the position of both methyl groups in the pyridine ring system. PMID:20474019

  10. (1)H NMR assignment corrections and (1)H, (13)C, (15)N NMR coordination shifts structural correlations in Fe(II), Ru(II) and Os(II) cationic complexes with 2,2'-bipyridine and 1,10-phenanthroline.

    PubMed

    Pazderski, Leszek; Pawlak, Tomasz; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2010-06-01

    (1)H, (13)C and (15)N NMR studies of iron(II), ruthenium(II) and osmium(II) tris-chelated cationic complexes with 2,2'-bipyridine and 1,10-phenanthroline of the general formula [M(LL)(3)](2+) (M = Fe, Ru, Os; LL = bpy, phen) were performed. Inconsistent literature (1)H signal assignments were corrected. Significant shielding of nitrogen-adjacent protons [H(6) in bpy, H(2) in phen] and metal-bonded nitrogens was observed, being enhanced in the series Ru(II) --> Os(II) --> Fe(II) for (1)H, Fe(II) --> Ru(II) --> Os(II) for (15)N and bpy --> phen for both nuclei. The carbons are deshielded, the effect increasing in the order Ru(II) --> Os(II) --> Fe(II). PMID:20474023

  11. BEBEtr and BUBI: J-compensated concurrent shaped pulses for 1H-13C experiments

    NASA Astrophysics Data System (ADS)

    Ehni, Sebastian; Luy, Burkhard

    2013-07-01

    Shaped pulses designed for broadband excitation, inversion and refocusing are important tools in modern NMR spectroscopy to achieve robust pulse sequences especially in heteronuclear correlation experiments. A large variety of mostly computer-optimized pulse shapes exist for different desired bandwidths, available rf-field strengths, and tolerance to B1-inhomogeneity. They are usually derived for a single spin 1/2, neglecting evolution due to J-couplings. While pulses with constant resulting phase are selfcompensated for heteronuclear coupling evolution as long as they are applied exclusively on a single nucleus, the situation changes for concurrently applied pulse shapes. Using the example of a 1H,13C two spin system, two J-compensated pulse pairs for the application in INEPT-type transfer elements were optimized: a point-to-point pulse sandwich called BEBEtr, consisting of a broadband excitation and time-reversed excitation pulse, and a combined universal rotation and point-to-point pulse pair called BUBI, which acts as a refocusing pulse on 1H and a corresponding inversion pulse on 13C. After a derivation of quality factors and optimization protocols, a theoretical and experimental comparison with conventionally derived BEBOP, BIBOP, and BURBOP-180° pulses is given. While the overall transfer efficiency of a single pulse pair is only reduced by approximately 0.1%, resulting transfer to undesired coherences is reduced by several percent. In experiments this can lead to undesired phase distortions for pairs of uncompensated pulse shapes and even differences in signal intensities of 5-10% in HSQC and up to 68% in more complex COB-HSQC experiments.

  12. Observation of 1H-13C and 1H-1H proximities in a paramagnetic solid by NMR at high magnetic field under ultra-fast MAS.

    PubMed

    Li, Shenhui; Trébosc, Julien; Lafon, Olivier; Zhou, Lei; Shen, Ming; Pourpoint, Frédérique; Amoureux, Jean-Paul; Deng, Feng

    2015-02-01

    The assignment of NMR signals in paramagnetic solids is often challenging since: (i) the large paramagnetic shifts often mask the diamagnetic shifts specific to the local chemical environment, and (ii) the hyperfine interactions with unpaired electrons broaden the NMR spectra and decrease the coherence lifetime, thus reducing the efficiency of usual homo- and hetero-nuclear NMR correlation experiments. Here we show that the assignment of (1)H and (13)C signals in isotopically unmodified paramagnetic compounds with moderate hyperfine interactions can be facilitated by the use of two two-dimensional (2D) experiments: (i) (1)H-(13)C correlations with (1)H detection and (ii) (1)H-(1)H double-quantum↔single-quantum correlations. These methods are experimentally demonstrated on isotopically unmodified copper (II) complex of l-alanine at high magnetic field (18.8 T) and ultra-fast Magic Angle Spinning (MAS) frequency of 62.5 kHz. Compared to (13)C detection, we show that (1)H detection leads to a 3-fold enhancement in sensitivity for (1)H-(13)C 2D correlation experiments. By combining (1)H-(13)C and (1)H-(1)H 2D correlation experiments with the analysis of (13)C longitudinal relaxation times, we have been able to assign the (1)H and (13)C signals of each l-alanine ligand. PMID:25557861

  13. 1H, 13C, 195Pt and 15N NMR structural correlations in Pd(II) and Pt(II) chloride complexes with various alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline.

    PubMed

    Pawlak, Tomasz; Pazderski, Leszek; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2011-02-01

    (1)H, (13)C, (195)Pt and (15)N NMR studies of platinide(II) (M = Pd, Pt) chloride complexes with such alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline as LL = 6,6'-dimethyl-bpy, 5,5'-dimethyl-bpy, 4,4'-di-tert-butyl-bpy, 2,9-dimethyl-phen, 2,9-dimethyl-4,7-diphenyl-phen, 3,4,7,8-tetramethyl-phen, having the general [M(LL)Cl(2)] formula were performed and the respective chemical shifts (δ(1H), δ(13C), δ(195Pt), δ(15N)) reported. (1)H high-frequency coordination shifts (Δ(coord)(1H) = δ(complex)(1H)-δ(ligand)(1H)) mostly pronounced for nitrogen-adjacent protons and methyl groups in the nearest adjacency of nitrogen, as well as (15)N low-frequency coordination shifts (Δ(coord)(15H) = δ(complex)(15H)-δ(ligand)(15H)) were discussed in relation to the molecular structures. PMID:21254225

  14. Rapid and accurate calculation of protein 1H, 13C and 15N chemical shifts.

    PubMed

    Neal, Stephen; Nip, Alex M; Zhang, Haiyan; Wishart, David S

    2003-07-01

    A computer program (SHIFTX) is described which rapidly and accurately calculates the diamagnetic 1H, 13C and 15N chemical shifts of both backbone and sidechain atoms in proteins. The program uses a hybrid predictive approach that employs pre-calculated, empirically derived chemical shift hypersurfaces in combination with classical or semi-classical equations (for ring current, electric field, hydrogen bond and solvent effects) to calculate 1H, 13C and 15N chemical shifts from atomic coordinates. The chemical shift hypersurfaces capture dihedral angle, sidechain orientation, secondary structure and nearest neighbor effects that cannot easily be translated to analytical formulae or predicted via classical means. The chemical shift hypersurfaces were generated using a database of IUPAC-referenced protein chemical shifts--RefDB (Zhang et al., 2003), and a corresponding set of high resolution (<2.1 A) X-ray structures. Data mining techniques were used to extract the largest pairwise contributors (from a list of approximately 20 derived geometric, sequential and structural parameters) to generate the necessary hypersurfaces. SHIFTX is rapid (<1 CPU second for a complete shift calculation of 100 residues) and accurate. Overall, the program was able to attain a correlation coefficient (r) between observed and calculated shifts of 0.911 (1Halpha), 0.980 (13Calpha), 0.996 (13Cbeta), 0.863 (13CO), 0.909 (15N), 0.741 (1HN), and 0.907 (sidechain 1H) with RMS errors of 0.23, 0.98, 1.10, 1.16, 2.43, 0.49, and 0.30 ppm, respectively on test data sets. We further show that the agreement between observed and SHIFTX calculated chemical shifts can be an extremely sensitive measure of the quality of protein structures. Our results suggest that if NMR-derived structures could be refined using heteronuclear chemical shifts calculated by SHIFTX, their precision could approach that of the highest resolution X-ray structures. SHIFTX is freely available as a web server at http

  15. Multi-dimensional 1H- 13C HETCOR and FSLG-HETCOR NMR study of sphingomyelin bilayers containing cholesterol in the gel and liquid crystalline states

    NASA Astrophysics Data System (ADS)

    Holland, Gregory P.; Alam, Todd M.

    2006-08-01

    13C cross polarization magic angle spinning (CP-MAS) and 1H MAS NMR spectra were collected on egg sphingomyelin (SM) bilayers containing cholesterol above and below the liquid crystalline phase transition temperature ( Tm). Two-dimensional (2D) dipolar heteronuclear correlation (HETCOR) spectra were obtained on SM bilayers in the liquid crystalline ( Lα) state for the first time and display improved resolution and chemical shift dispersion compared to the individual 1H and 13C spectra and significantly aid in spectral assignment. In the gel ( Lβ) state, the 1H dimension suffers from line broadening due to the 1H- 1H homonuclear dipolar coupling that is not completely averaged by the combination of lipid mobility and MAS. This line broadening is significantly suppressed by implementing frequency switched Lee-Goldburg (FSLG) homonuclear 1H decoupling during the evolution period. In the liquid crystalline ( Lα) phase, no improvement in line width is observed when FSLG is employed. All of the observed resonances are assignable to cholesterol and SM environments. This study demonstrates the ability to obtain 2D heteronuclear correlation experiments in the gel state for biomembranes, expands on previous SM assignments, and presents a comprehensive 1H/ 13C NMR assignment of SM bilayers containing cholesterol. Comparisons are made to a previous report on cholesterol chemical shifts in dimyristoylphosphatidylcholine (DMPC) bilayers. A number of similarities and some differences are observed and discussed.

  16. Improving the resolution in proton-detected through-space heteronuclear multiple quantum correlation NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Shen, Ming; Trébosc, J.; Lafon, O.; Pourpoint, F.; Hu, Bingwen; Chen, Qun; Amoureux, J.-P.

    2014-08-01

    Connectivities and proximities between protons and low-gamma nuclei can be probed in solid-state NMR spectroscopy using two-dimensional (2D) proton-detected heteronuclear correlation, through Heteronuclear Multiple Quantum Correlation (HMQC) pulse sequence. The indirect detection via protons dramatically enhances the sensitivity. However, the spectra are often broadened along the indirect F1 dimension by the decay of heteronuclear multiple-quantum coherences under the strong 1H-1H dipolar couplings. This work presents a systematic comparison of the performances of various decoupling schemes during the indirect t1 evolution period of dipolar-mediated HMQC (D-HMQC) experiment. We demonstrate that 1H-1H dipolar decoupling sequences during t1, such as symmetry-based schemes, phase-modulated Lee-Goldburg (PMLG) and Decoupling Using Mind-Boggling Optimization (DUMBO), provide better resolution than continuous wave 1H irradiation. We also report that high resolution requires the preservation of 1H isotropic chemical shifts during the decoupling sequences. When observing indirectly broad spectra presenting numerous spinning sidebands, the D-HMQC sequence must be fully rotor-synchronized owing to the rotor-synchronized indirect sampling and dipolar recoupling sequence employed. In this case, we propose a solution to reduce artefact sidebands caused by the modulation of window delays before and after the decoupling application during the t1 period. Moreover, we show that 1H-1H dipolar decoupling sequence using Smooth Amplitude Modulation (SAM) minimizes the t1-noise. The performances of the various decoupling schemes are assessed via numerical simulations and compared to 2D 1H-{13C} D-HMQC experiments on [U-13C]-L-histidineṡHClṡH2O at various magnetic fields and Magic Angle spinning (MAS) frequencies. Great resolution and sensitivity enhancements resulting from decoupling during t1 period enable the detection of heteronuclear correlation between aliphatic protons and

  17. Dynamic nuclear polarization-enhanced 1H-13C double resonance NMR in static samples below 20 K

    NASA Astrophysics Data System (ADS)

    Potapov, Alexey; Thurber, Kent R.; Yau, Wai-Ming; Tycko, Robert

    2012-08-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H-13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H-13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H-13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr-Purcell experiments and numerical simulations of Carr-Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C-13C exchange spectrum of selectively 13C-labeled β-amyloid fibrils.

  18. 1H, 13C and 15N NMR assignments of phenazopyridine derivatives.

    PubMed

    Burgueño-Tapia, Eleuterio; Mora-Pérez, Yolanda; Morales-Ríos, Martha S; Joseph-Nathan, Pedro

    2005-03-01

    Phenazopyridine hydrochloride (1), a drug in clinical use for many decades, and some derivatives were studied by one- and two-dimensional (1)H, (13)C and (15)N NMR methodology. The assignments, combined with DFT calculations, reveal that the preferred protonation site of the drug is the pyridine ring nitrogen atom. The chemoselective acetylation of phenazopyridine (2) and its influence on the polarization of the azo nitrogen atoms were evidenced by the (15)N NMR spectra. Molecular calculations of the phenazopyridines 2-4 show that the pyridine and phenyl groups are oriented in an antiperiplanar conformation with intramolecular hydrogen bonding between the N-b atom and the C-2 amino group preserving the E-azo stereochemistry. PMID:15625718

  19. Changes in Lignin and Polysaccharide Components in 13 Cultivars of Rice Straw following Dilute Acid Pretreatment as Studied by Solution-State 2D 1H-13C NMR

    PubMed Central

    Teramura, Hiroshi; Sasaki, Kengo; Oshima, Tomoko; Aikawa, Shimpei; Matsuda, Fumio; Okamoto, Mami; Shirai, Tomokazu; Kawaguchi, Hideo; Ogino, Chiaki; Yamasaki, Masanori; Kikuchi, Jun; Kondo, Akihiko

    2015-01-01

    A renewable raw material, rice straw is pretreated for biorefinery usage. Solution-state two-dimensional (2D) 1H-13 C hetero-nuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy, was used to analyze 13 cultivars of rice straw before and after dilute acid pretreatment, to characterize general changes in the lignin and polysaccharide components. Intensities of most (15 of 16) peaks related to lignin aromatic regions, such as p-coumarate, guaiacyl, syringyl, p-hydroxyphenyl, and cinnamyl alcohol, and methoxyl, increased or remained unchanged after pretreatment. In contrast, intensities of most (11 of 13) peaks related to lignin aliphatic linkages or ferulate decreased. Decreased heterogeneity in the intensities of three peaks related to cellulose components in acid-insoluble residues resulted in similar glucose yield (0.45–0.59 g/g-dry biomass). Starch-derived components showed positive correlations (r = 0.71 to 0.96) with glucose, 5-hydroxymethylfurfural (5-HMF), and formate concentrations in the liquid hydrolysates, and negative correlations (r = –0.95 to –0.97) with xylose concentration and acid-insoluble residue yield. These results showed the fate of lignin and polysaccharide components by pretreatment, suggesting that lignin aromatic regions and cellulose components were retained in the acid insoluble residues and starch-derived components were transformed into glucose, 5-HMF, and formate in the liquid hydrolysate. PMID:26083431

  20. 1H, 13C and 29Si NMR of tetramethylsilane in liquid crystals

    NASA Astrophysics Data System (ADS)

    Hiltunen, Y.; Jokisaari, J.

    1990-12-01

    The 1H, 13C and 29Si NMR spectra of tetramethylsilane (TMS) dissolved in two nematic liquid crystals (LC) and in their three mixtures were recorded. The proton—proton, proton—carbon and proton—silicon dipolar couplings, which arise from molecular deformation in the LC environment, were determined. The results for the 2DHH, 4DHH, 3DCH and 2DSiH couplings show only a small variation as a function of the composition of the LC mixture. On the contrary, the one-bond CH dipolar coupling is markedly solvent dependent: it varies from -6.22 Hz (in ZLI 1167) to +3.63 Hz (in phase IV). The 1DCH coupling of TMS vanishes in a certain mixture of the two liquid crystals; this mixture, however, is not the same as that in which the corresponding coupling of methane was earlier observed to vanish. This different behaviour of TMS and methane may be due to the additional torques which act on the SiC bonds of TMS.

  1. Topotecan dynamics, tautomerism and reactivity--1H/13C NMR and ESI MS study.

    PubMed

    Hyz, Karolina; Kawecki, Robert; Bednarek, Elzbieta; Bocian, Wojciech; Sitkowski, Jerzy; Kozerski, Lech

    2010-08-01

    Topotecan (TPT) is in clinical use as an antitumor agent, hycamtin. Because of this, it requires both biologically and chemically useful information to be available. TPT acts by binding to the covalent complex formed by nicked DNA and topoisomerase I. This has a poisonous effect since inserted into the single-strand nick and TPT inhibits its religation. We used NMR to trace TPT dynamics, tautomerism and solvolysis products in various solvents and conditions. Chemical stability was assessed in methanol and DMSO as compared to water, and the regioselectivity of the N- and O-methylation was studied using various alkylating agents. The reaction products of quaternization of the nitrogen atom and methylation of the oxygen atom were characterized by means of ESI MS, (1)H/(13)C-HMBC and -HSQCAD NMR. We have focused on the NMR characterization of TPT with an anticipation that its aggregation, tumbling properties and the intramolecular dipolar interactions will be a common feature for other compounds described in this article. These features can also be useful in tracing the interactions of this class of topoisomerase I (TopoI) poisons with DNA. Moreover, the results explained shed light on the recently disclosed problem of lack of stability of TPT in the heart tissue homogenate samples using the analytical assays developed for this class of compounds carried out in the presence of methanol. PMID:20623719

  2. Studies of minute quantities of natural abundance molecules using 2D heteronuclear correlation spectroscopy under 100kHz MAS

    DOE PAGESBeta

    Nishiyama, Y.; Kobayashi, T.; Malon, M.; Singappuli-Arachchige, D.; Slowing, I. I.; Pruski, M.

    2015-02-16

    Two-dimensional 1H{13C} heteronuclear correlation solid-state NMR spectra of naturally abundant solid materials are presented, acquired using the 0.75-mm magic angle spinning (MAS) probe at spinning rates up to 100 kHz. In spite of the miniscule sample volume (290 nL), high-quality HSQC-type spectra of bulk samples as well as surface-bound molecules can be obtained within hours of experimental time. The experiments are compared with those carried out at 40 kHz MAS using a 1.6-mm probe, which offered higher overall sensitivity due to a larger rotor volume. The benefits of ultrafast MAS in such experiments include superior resolution in 1H dimensionmore » without resorting to 1H–1H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. As a result, the HMQC spectra of surface-bound species can be also acquired under 100 kHz MAS, although the dephasing of transverse magnetization has significant effect on the efficiency transfer under MAS alone.« less

  3. (1)H, (13)C and (15)N NMR assignments of a calcium-binding protein from Entamoeba histolytica.

    PubMed

    Verma, Deepshikha; Bhattacharya, Alok; Chary, Kandala V R

    2016-04-01

    We report almost complete sequence specific (1)H, (13)C and (15)N NMR assignments of a 150-residue long calmodulin-like calcium-binding protein from Entamoeba histolytica (EhCaBP6), as a prelude to its structural and functional characterization. PMID:26377206

  4. 1H, 13C and 15N resonance assignments of URNdesign, a computationally redesigned RRM protein

    SciTech Connect

    Dobson, Neil; Dantas, Gautam; Varani, Gabriele

    2005-10-01

    Protein design represents one of the great challenges of computational structural biology. The ability to successfully design new proteins would allow us to generate new reagents and enzymes, while at the same time providing us with an understanding of the principles of protein stability. Here we report 1H, 15N and 13C resonance assignments of a redesigned U1A protein, URNdesign. U1A has been studied extensively by our group and hence was chosen as a design target. For the assignments we sued 2D and 3D heteronuclearNMR experiments with uniformly 13C, 15N-labeled URNdesign. The assignments for the backbone NH, CO,Ca and Cb nuclei are 94%complete. Sidechain 1Hand13C, aromatic andQ/NNH2 resonances are essentially complete with guanidinium and K NH3 residues unassigned. BMRB deposit with accession number 6493

  5. Secondary structure and (1)H, (13)C, (15)N resonance assignments of the endosomal sorting protein sorting nexin 3.

    PubMed

    Overduin, Michael; Rajesh, Sandya; Gruenberg, Jean; Lenoir, Marc

    2015-10-01

    Sorting nexin 3 (SNX3) belongs to a sub-family of sorting nexins that primarily contain a single Phox homology domain capable of binding phosphoinositides and membranes. We report the complete (1)H, (13)C and (15)N resonance assignments of the full-length human SNX3 protein and identification of its secondary structure elements, revealing a canonical fold and unstructured termini. PMID:25893673

  6. Detection of intracellular lactate with localized diffusion { 1H- 13C}-spectroscopy in rat glioma in vivo

    NASA Astrophysics Data System (ADS)

    Pfeuffer, Josef; Lin, Joseph C.; DelaBarre, Lance; Ugurbil, Kamil; Garwood, Michael

    2005-11-01

    The aim of this study was to compare the diffusion characteristic of lactate and alanine in a brain tumor model to that of normal brain metabolites known to be mainly intracellular such as N-acetylaspartate or creatine. The diffusion of 13C-labeled metabolites was measured in vivo with localized NMR spectroscopy at 9.4 T (400 MHz) using a previously described localization and editing pulse sequence known as ACED-STEAM ('adiabatic carbon editing and decoupling'). 13C-labeled glucose was administered and the apparent diffusion coefficients of the glycolytic products, { 1H- 13C}-lactate and { 1H- 13C}-alanine, were determined in rat intracerebral 9L glioma. To obtain insights into { 1H- 13C}-lactate compartmentation (intra- versus extracellular), the pulse sequence used very large diffusion weighting (50 ms/μm 2). Multi-exponential diffusion attenuation of the lactate metabolite signals was observed. The persistence of a lactate signal at very large diffusion weighting provided direct experimental evidence of significant intracellular lactate concentration. To investigate the spatial distribution of lactate and other metabolites, 1H spectroscopic images were also acquired. Lactate and choline-containing compounds were consistently elevated in tumor tissue, but not in necrotic regions and surrounding normal-appearing brain. Overall, these findings suggest that lactate is mainly associated with tumor tissue and that within the time-frame of these experiments at least some of the glycolytic product ([ 13C] lactate) originates from an intracellular compartment.

  7. Benchmark fragment-based (1)H, (13)C, (15)N and (17)O chemical shift predictions in molecular crystals.

    PubMed

    Hartman, Joshua D; Kudla, Ryan A; Day, Graeme M; Mueller, Leonard J; Beran, Gregory J O

    2016-08-21

    The performance of fragment-based ab initio(1)H, (13)C, (15)N and (17)O chemical shift predictions is assessed against experimental NMR chemical shift data in four benchmark sets of molecular crystals. Employing a variety of commonly used density functionals (PBE0, B3LYP, TPSSh, OPBE, PBE, TPSS), we explore the relative performance of cluster, two-body fragment, and combined cluster/fragment models. The hybrid density functionals (PBE0, B3LYP and TPSSh) generally out-perform their generalized gradient approximation (GGA)-based counterparts. (1)H, (13)C, (15)N, and (17)O isotropic chemical shifts can be predicted with root-mean-square errors of 0.3, 1.5, 4.2, and 9.8 ppm, respectively, using a computationally inexpensive electrostatically embedded two-body PBE0 fragment model. Oxygen chemical shieldings prove particularly sensitive to local many-body effects, and using a combined cluster/fragment model instead of the simple two-body fragment model decreases the root-mean-square errors to 7.6 ppm. These fragment-based model errors compare favorably with GIPAW PBE ones of 0.4, 2.2, 5.4, and 7.2 ppm for the same (1)H, (13)C, (15)N, and (17)O test sets. Using these benchmark calculations, a set of recommended linear regression parameters for mapping between calculated chemical shieldings and observed chemical shifts are provided and their robustness assessed using statistical cross-validation. We demonstrate the utility of these approaches and the reported scaling parameters on applications to 9-tert-butyl anthracene, several histidine co-crystals, benzoic acid and the C-nitrosoarene SnCl2(CH3)2(NODMA)2. PMID:27431490

  8. State-of-the-Art Direct 13C and Indirect 1H-[13C] NMR Spectroscopy In Vivo

    PubMed Central

    de Graaf, Robin A.; Rothman, Douglas L.; Behar, Kevin L.

    2013-01-01

    Carbon-13 NMR spectroscopy in combination with 13C-labeled substrate infusion is a powerful technique to measure a large number of metabolic fluxes non-invasively in vivo. It has been used to quantify glycogen synthesis rates, establish quantitative relationships between energy metabolism and neurotransmission and evaluate the importance of different substrates. All measurements can, in principle, be performed through direct 13C NMR detection or via indirect 1H-[13C] NMR detection of the protons attached to 13C nuclei. The choice for detection scheme and pulse sequence depends on the magnetic field strength, whereas substrate selection depends on the metabolic pathways that are studied. 13C NMR spectroscopy remains a challenging technique that requires several non-standard hardware modifications, infusion of 13C-labeled substrates and sophisticated processing and metabolic modeling. Here the various aspects of direct 13C and indirect 1H-[13C] NMR are reviewed with the aim of providing a practical guide. PMID:21919099

  9. Method for determining molar concentrations of metabolites in complex solutions from two-dimensional 1H-13C NMR spectra.

    PubMed

    Lewis, Ian A; Schommer, Seth C; Hodis, Brendan; Robb, Kate A; Tonelli, Marco; Westler, William M; Sussman, Michael R; Markley, John L

    2007-12-15

    One-dimensional (1D) (1)H nuclear magnetic resonance (NMR) spectroscopy is used extensively for high-throughput analysis of metabolites in biological fluids and tissue extracts. Typically, such spectra are treated as multivariate statistical objects rather than as collections of quantifiable metabolites. We report here a two-dimensional (2D) (1)H-(13)C NMR strategy (fast metabolite quantification, FMQ, by NMR) for identifying and quantifying the approximately 40 most abundant metabolites in biological samples. To validate this technique, we prepared mixtures of synthetic compounds and extracts from Arabidopsis thaliana, Saccharomyces cerevisiae, and Medicago sativa. We show that accurate (technical error 2.7%) molar concentrations can be determined in 12 min using our quantitative 2D (1)H-(13)C NMR strategy. In contrast, traditional 1D (1)H NMR analysis resulted in 16.2% technical error under nearly ideal conditions. We propose FMQ by NMR as a practical alternative to 1D (1)H NMR for metabolomics studies in which 50-mg (extract dry weight) samples can be obtained. PMID:17985927

  10. High-resolution heteronuclear correlation spectroscopy based on spatial encoding and coherence transfer in inhomogeneous fields

    NASA Astrophysics Data System (ADS)

    Wang, Kaiyu; Zhang, Zhiyong; Chen, Hao; Cai, Shuhui; Chen, Zhong

    2015-11-01

    Two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy has been proven to be a powerful technique for chemical, biological, and medical studies. Heteronuclear single quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC) are two frequently used 2D NMR methods. In combination with spatially encoded techniques, a heteronuclear 2D NMR spectrum can be acquired in several seconds and may be applied to monitoring chemical reactions. However, it is difficult to obtain high-resolution NMR spectra in inhomogeneous fields. Inspired by the idea of tracing the difference of precession frequencies between two different spins to yield high-resolution spectra, we propose a method with correlation acquisition option and J-resolved-like acquisition option to ultrafast obtain high-resolution HSQC/HMBC spectra and heteronuclear J-resolved-like spectra in inhomogeneous fields.

  11. (1)H, (13)C and (15)N backbone assignment of the EC-1 domain of human E-cadherin.

    PubMed

    Prasasty, Vivitri D; Krause, Mary E; Tambunan, Usman S F; Anbanandam, Asokan; Laurence, Jennifer S; Siahaan, Teruna J

    2015-04-01

    The Extracellular 1 (EC1) domain of E-cadherin has been shown to be important for cadherin-cadherin homophilic interactions. Cadherins are responsible for calcium-mediated cell-cell adhesion located at the adherens junction of the biological barriers (i.e., intestinal mucosa and the blood-brain barrier (BBB)). Cadherin peptides can modulate cadherin interactions to improve drug delivery through the BBB. However, the mechanism of modulating the E-cadherin interactions by cadherin peptides has not been fully elucidated. To provide a basis for subsequent examination of the structure and peptide-binding properties of the EC1 domain of human E-cadherin using solution NMR spectroscopy, the (1)H, (13)C and (15)N backbone resonance of the uniformly labeled-EC1 were assigned and the secondary structure was determined based on the chemical shift values. These resonance assignments are essential for assessing protein-ligand interactions and are reported here. PMID:24510398

  12. 1H, 13C and 15N Backbone Assignment of the EC-1 Domain of Human E-Cadherin

    PubMed Central

    Prasasty, Vivitri D.; Krause, Mary E.; Tambunan, Usman S. F.; Anbanandam, Asokan; Laurence, Jennifer S.; Siahaan, Teruna J.

    2014-01-01

    The EC1 domain of E-cadherin has been shown to be important for cadherin-cadherin homophilic interactions. Cadherins are responsible for calcium-mediated cell-cell adhesion located at the adherens junction of the biological barriers (i.e., intestinal mucosa and the blood-brain barrier (BBB). Cadherin peptides can modulate cadherin interactions to improve drug delivery through the blood-brain barriers (BBB). However, the mechanism of modulating the E-cadherin interactions by cadherin peptides has not been fully elucidated. To provide a basis for subsequent examination of the structure and peptide-binding properties of the EC1 domain of human E-cadherin using solution NMR spectroscopy, the 1H, 13C and 15N backbone resonance of the uniformly labeled-EC1 were assigned and the secondary structure was determined based on the chemical shift values. These resonance assignments are essential for assessing protein-ligand interactions and are reported here. PMID:24510398

  13. Automated structure verification based on a combination of 1D (1)H NMR and 2D (1)H - (13)C HSQC spectra.

    PubMed

    Golotvin, Sergey S; Vodopianov, Eugene; Pol, Rostislav; Lefebvre, Brent A; Williams, Antony J; Rutkowske, Randy D; Spitzer, Timothy D

    2007-10-01

    A method for structure validation based on the simultaneous analysis of a 1D (1)H NMR and 2D (1)H - (13)C single-bond correlation spectrum such as HSQC or HMQC is presented here. When compared with the validation of a structure by a 1D (1)H NMR spectrum alone, the advantage of including a 2D HSQC spectrum in structure validation is that it adds not only the information of (13)C shifts, but also which proton shifts they are directly coupled to, and an indication of which methylene protons are diastereotopic. The lack of corresponding peaks in the 2D spectrum that appear in the 1D (1)H spectrum, also gives a clear picture of which protons are attached to heteroatoms. For all these benefits, combined NMR verification was expected and found by all metrics to be superior to validation by 1D (1)H NMR alone. Using multiple real-life data sets of chemical structures and the corresponding 1D and 2D data, it was possible to unambiguously identify at least 90% of the correct structures. As part of this test, challenging incorrect structures, mostly regioisomers, were also matched with each spectrum set. For these incorrect structures, the false positive rate was observed as low as 6%. PMID:17694570

  14. The Heteronuclear Single-Quantum Correlation (HSQC) Experiment: Vectors versus Product Operators

    ERIC Educational Resources Information Center

    de la Vega-Herna´ndez, Karen; Antuch, Manuel

    2015-01-01

    A vectorial representation of the full sequence of events occurring during the 2D-NMR heteronuclear single-quantum correlation (HSQC) experiment is presented. The proposed vectorial representation conveys an understanding of the magnetization evolution during the HSQC pulse sequence for those who have little or no quantum mechanical background.…

  15. Sequence-specific (1)H, (13)C and (15)N backbone resonance assignments of the plakin repeat domain of human envoplakin.

    PubMed

    Jeeves, Mark; Fogl, Claudia; Al-Jassar, Caezar; Chidgey, Martyn; Overduin, Michael

    2016-04-01

    The plakin repeat domain is a distinctive hallmark of the plakin superfamily of proteins, which are found within all epithelial tissues. Plakin repeat domains mediate the interactions of these proteins with the cell cytoskeleton and are critical for the maintenance of tissue integrity. Despite their biological importance, no solution state resonance assignments are available for any homologue. Here we report the essentially complete (1)H, (13)C and (15)N backbone chemical shift assignments of the singular 22 kDa plakin repeat domain of human envoplakin, providing the means to investigate its interactions with ligands including intermediate filaments. PMID:26590577

  16. Protonation of carbon single-walled nanotubes studied using 13C and 1H-13C cross polarization nuclear magnetic resonance and Raman spectroscopies.

    PubMed

    Engtrakul, Chaiwat; Davis, Mark F; Gennett, Thomas; Dillon, Anne C; Jones, Kim M; Heben, Michael J

    2005-12-14

    The reversible protonation of carbon single-walled nanotubes (SWNTs) in sulfuric acid and Nafion was investigated using solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies. Magic-angle spinning (MAS) was used to obtain high-resolution 13C and 1H-13C cross polarization (CP) NMR spectra. The 13C NMR chemical shifts are reported for bulk SWNTs, H2SO4-treated SWNTs, SWNT-Nafion polymer composites, SWNT-AQ55 polymer composites, and SWNTs in contact with water. Protonation occurs without irreversible oxidation of the nanotube substrate via a charge-transfer process. This is the first report of a chemically induced change in a SWNT 13C resonance brought about by a reversible interaction with an acidic proton, providing additional evidence that carbon nanotubes behave as weak bases. Cross polarization was found to be a powerful technique for providing an additional contrast mechanism for studying nanotubes in contact with other chemical species. The CP studies confirmed polarization transfer from nearby protons to nanotube carbon atoms. The CP technique was also applied to investigate water adsorbed on carbon nanotube surfaces. Finally, the degree of bundling of the SWNTs in Nafion films was probed with the 1H-13C CP-MAS technique. PMID:16332107

  17. 1H, 13C and 15N nuclear magnetic resonance coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with phenylpyridines.

    PubMed

    Pazderski, Leszek; Tousek, Jaromír; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2009-08-01

    1H, 13C and 15N nuclear magnetic resonance studies of gold(III), palladium(II) and platinum(II) chloride complexes with phenylpyridines (PPY: 4-phenylpyridine, 4ppy; 3-phenylpyridine, 3ppy; and 2-phenylpyridine, 2ppy) having the general formulae [Au(PPY)Cl3], trans-/cis-[Pd(PPY)2Cl2] and trans-/cis-[Pt(PPY)2Cl2] were performed and the respective chemical shifts (delta1H, delta13C and delta15N) reported. 1H, 13C and 15N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Delta(coord)(1H) = delta(complex)(1H)-delta(ligand)(1H), Delta(coord)(13C) = delta(complex)(13C)-delta(ligand)(13C), Delta(coord)(15N) = delta(complex)(15N)-delta(ligand)(15N)) were discussed in relation to the type of the central atom (Au(III), Pd(II) and Pt(II)), geometry (trans-/cis-) and the position of a phenyl group in the pyridine ring system. PMID:19472306

  18. 1H, 13C, 15N and 195Pt NMR studies of Au(III) and Pt(II) chloride organometallics with 2-phenylpyridine.

    PubMed

    Pazderski, Leszek; Pawlak, Tomasz; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2009-11-01

    (1)H, (13)C, (15)N and (195)Pt NMR studies of gold(III) and platinum(II) chloride organometallics with N(1),C(2')-chelated, deprotonated 2-phenylpyridine (2ppy*) of the formulae [Au(2ppy*)Cl(2)], trans(N,N)-[Pt(2ppy*)(2ppy)Cl] and trans(S,N)-[Pt(2ppy*)(DMSO-d(6))Cl] (formed in situ upon dissolving [Pt(2ppy*)(micro-Cl)](2) in DMSO-d(6)) were performed. All signals were unambiguously assigned by HMBC/HSQC methods and the respective (1)H, (13)C and (15)N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Delta(1H)(coord) = delta(1H)(complex) - delta(1H)(ligand), Delta(13C)(coord) = delta(13C)(complex) - delta(13C)(ligand), Delta(15N)(coord) = delta(15N)(complex) - delta(15N)(ligand)), as well as (195)Pt chemical shifts and (1)H-(195)Pt coupling constants discussed in relation to the known molecular structures. Characteristic deshielding of nitrogen-adjacent H(6) protons and metallated C(2') atoms as well as significant shielding of coordinated N(1) nitrogens is discussed in respect to a large set of literature NMR data available for related cyclometallated compounds. PMID:19691018

  19. Multinuclear 1H, 13C and 15N NMR study of some substituted 2-amino-4-nitropyridines and their N-oxides

    NASA Astrophysics Data System (ADS)

    Laihia, K.; Kolehmainen, E.; Kauppinen, R.; Lorenc, J.; Puszko, A.

    2002-05-01

    1H, 13C and 15N NMR chemical shift assignments based on pulsed field gradient selected PFG 1H,X (X= 13C and 15N) HMQC and HMBC experiments are reported for three 4-nitropyridine N-oxides and four 4-nitropyridines. It was found that an ortho effect of a methyl group inhibits the deshielding effect of the 4-nitro group and that this effect and the so-called back donation is influenced by electronegativity and position of substituents in the multisubstituted pyridine N-oxides. The shielding effect of N-oxide group is most pronounced in the 15N NMR chemical shifts of the studied compounds. This effect is further modified by methylamino, methylnitramino, 5- or 3-methyl and 4-nitro groups. Among them the 4-nitro group exerts the highest influence on the shielding effect of the N-oxide functionality. Experimental 1H, 13C and 15N NMR chemical shifts and GIAO/DFT theoretical calculations are consistent with each other and supported by the reactivity on nucleophilic substitution, the UV spectral and the dipole moment data.

  20. Generation of heteronuclear 13C 1H chemical-shift correlations using soft pulses

    NASA Astrophysics Data System (ADS)

    Doddrell, David M.; Brooks, William; Field, James; Lynden-Bell, R. M.

    Two multipulse sequences are analyzed which can be used to generate heteronuclear 13C, 1H chemical-shift correlations without 2D NMR techniques. Both sequences utilize polarization-transfer techniques and generate the required chemical-shift correlation using a single soft proton pulse. The most useful technique is an extension of the DEPT method of polarization transfer since not only are the chemical-shift correlations generated in an easy to interpret form, but depending on the specific form of the pulse train used, the method can be employed to obtain information on the CH n group multiplicity. The methods are illustrated by applying them to generate 13C, 1H chemical-shift correlation spectra for menthol and cholesterol.

  1. 1H, 13C, and 15N resonance assignments for the protein coded by gene locus BB0938 of Bordetella bronchiseptica

    SciTech Connect

    Rossi, Paolo; Ramelot, Theresa A.; Xiao, Rong; Ho, Chi K.; Ma, LiChung; Acton, Thomas; Kennedy, Michael A.; Montelione, Gaetano

    2005-11-01

    The product of gene locus BB0938 from Bordetella bronchiseptica (Swiss-Prot ID: Q7WNU7-BORBR; NESG target ID: BoR11; Wunderlich et al., 2004; Pfam ID: PF03476) is a 128-residue protein of unknown function. This broadly conserved protein family is found in eubacteria and eukaryotes. Using triple resonance NMR techniques, we have determined 98% of backbone and 94% of side chain 1H, 13C, and 15N resonance assignments. The chemical shift and 3J(HN?Ha) scalar coupling data reveal a b topology with a seven-residue helical insert, ??????????. BMRB deposit with accession number 6693. Reference: Wunderlich et al. (2004) Proteins, 56, 181?187.

  2. 1H, 13C, and 15N resonance assignments for Escherichia coli ytfP, a member of the broadly conserved UPF0131 protein domain family

    SciTech Connect

    Aramini, James M.; Swapna, G.V.T.; Huang, Yuanpeng; Rajan, Paranji K.; Xiao, Rong; Shastry, Ritu; Acton, Thomas; Cort, John R.; Kennedy, Michael A.; Montelione, Gaetano

    2005-11-01

    Protein ytfP from Escherichia coli (Swiss-Prot ID: YTFP-ECOLI; NESG target ID: ER111; Wunderlich et al., 2004) is a 113-residue member of the UPF0131 protein family (Pfam ID: PF03674) of unknown function. This domain family is found in organisms from all three kingdoms, archaea, eubacteria and eukaryotes. Using triple resonance NMR techniques, we have determined 97% of backbone and 91% of side chain 1H, 13C, and 15N resonance assignments. The chemical shift and 3J(HN?Ha) scalar coupling data reveal a mixed a/b topology,????????. BMRB deposit with Accession No. 6448. Reference: Wunderlich et al. (2004) Proteins, 56, 181?187.

  3. Stereospecificity of (1) H, (13) C and (15) N shielding constants in the isomers of methylglyoxal bisdimethylhydrazone: problem with configurational assignment based on (1) H chemical shifts.

    PubMed

    Afonin, Andrei V; Pavlov, Dmitry V; Ushakov, Igor A; Keiko, Natalia A

    2012-07-01

    In the (13) C NMR spectra of methylglyoxal bisdimethylhydrazone, the (13) C-5 signal is shifted to higher frequencies, while the (13) C-6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the (1) H-6 chemical shift and (1) J(C-6,H-6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the -CH═N- bond does not change. This paradox can be rationalized by the C-H⋯N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum-chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ((1) H-6) and (1) J(C-6,H-6) parameters. The effect of the C-H⋯N hydrogen bond on the (1) H shielding and one-bond (13) C-(1) H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The (1) H, (13) C and (15) N chemical shifts of the 2- and 8-(CH(3) )(2) N groups attached to the -C(CH(3) )═N- and -CH═N- moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8-(CH(3) )(2) N group conjugate effectively with the π-framework, and the 2-(CH(3) )(2) N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N-2- and N-8- nitrogen lone pairs to the π-framework varies, which affects the (1) H, (13) C and (15) N shieldings. PMID:22615146

  4. Extending long-range heteronuclear NMR connectivities by HSQMBC-COSY and HSQMBC-TOCSY experiments

    NASA Astrophysics Data System (ADS)

    Saurí, Josep; Marcó, Núria; Williamson, R. Thomas; Martin, Gary E.; Parella, Teodor

    2015-09-01

    The detection of long-range heteronuclear correlations presenting J(CH) coupling values smaller than 1-2 Hz is a challenge in the structural analysis of small molecules and natural products. HSQMBC-COSY and HSQMBC-TOCSY pulse schemes are evaluated as complementary NMR methods to standard HMBC/HSQMBC experiments. Incorporation of an additional J(HH) transfer step in the basic HSQMBC pulse scheme can favor the sensitive observation of traditionally missing or very weak correlations and, in addition, facilitates the detection of a significant number of still longer-range connectivities to both protonated and non-protonated carbons under optimum sensitivity conditions. A comparative 1H-13C study is performed using strychnine as a model compound and several examples are also provided including 1H-15N applications.

  5. Site-specific analysis of heteronuclear Overhauser effects in microcrystalline proteins.

    PubMed

    del Amo, Juan Miguel Lopez; Agarwal, Vipin; Sarkar, Riddhiman; Porter, Justin; Asami, Sam; Rübbelke, Martin; Fink, Uwe; Xue, Yi; Lange, Oliver F; Reif, Bernd

    2014-08-01

    Relaxation parameters such as longitudinal relaxation are susceptible to artifacts such as spin diffusion, and can be affected by paramagnetic impurities as e.g. oxygen, which make a quantitative interpretation difficult. We present here the site-specific measurement of [(1)H](13)C and [(1)H](15)N heteronuclear rates in an immobilized protein. For methyls, a strong effect is expected due to the three-fold rotation of the methyl group. Quantification of the [(1)H](13)C heteronuclear NOE in combination with (13)C-R 1 can yield a more accurate analysis of side chain motional parameters. The observation of significant [(1)H](15)N heteronuclear NOEs for certain backbone amides, as well as for specific asparagine/glutamine sidechain amides is consistent with MD simulations. The measurement of site-specific heteronuclear NOEs is enabled by the use of highly deuterated microcrystalline protein samples in which spin diffusion is reduced in comparison to protonated samples. PMID:24989039

  6. Sequential acquisition of multi-dimensional heteronuclear chemical shift correlation spectra with 1H detection

    PubMed Central

    Bellstedt, Peter; Ihle, Yvonne; Wiedemann, Christoph; Kirschstein, Anika; Herbst, Christian; Görlach, Matthias; Ramachandran, Ramadurai

    2014-01-01

    RF pulse schemes for the simultaneous acquisition of heteronuclear multi-dimensional chemical shift correlation spectra, such as {HA(CA)NH & HA(CACO)NH}, {HA(CA)NH & H(N)CAHA} and {H(N)CAHA & H(CC)NH}, that are commonly employed in the study of moderately-sized protein molecules, have been implemented using dual sequential 1H acquisitions in the direct dimension. Such an approach is not only beneficial in terms of the reduction of experimental time as compared to data collection via two separate experiments but also facilitates the unambiguous sequential linking of the backbone amino acid residues. The potential of sequential 1H data acquisition procedure in the study of RNA is also demonstrated here. PMID:24671105

  7. Dynamic Nuclear Polarization of 1H, 13C, and 59Co in a Tris(ethylenediamine)cobalt(III) Crystalline Lattice Doped with Cr(III)

    PubMed Central

    2015-01-01

    The study of inorganic crystalline materials by solid-state NMR spectroscopy is often complicated by the low sensitivity of heavy nuclei. However, these materials often contain or can be prepared with paramagnetic dopants without significantly affecting the structure of the crystalline host. Dynamic nuclear polarization (DNP) is generally capable of enhancing NMR signals by transferring the magnetization of unpaired electrons to the nuclei. Therefore, the NMR sensitivity in these paramagnetically doped crystals might be increased by DNP. In this paper we demonstrate the possibility of efficient DNP transfer in polycrystalline samples of [Co(en)3Cl3]2·NaCl·6H2O (en = ethylenediamine, C2H8N2) doped with Cr(III) in varying concentrations between 0.1 and 3 mol %. We demonstrate that 1H, 13C, and 59Co can be polarized by irradiation of Cr(III) with 140 GHz microwaves at a magnetic field of 5 T. We further explain our findings on the basis of electron paramagnetic resonance spectroscopy of the Cr(III) site and analysis of its temperature-dependent zero-field splitting, as well as the dependence of the DNP enhancement factor on the external magnetic field and microwave power. This first demonstration of DNP transfer from one paramagnetic metal ion to its diamagnetic host metal ion will pave the way for future applications of DNP in paramagnetically doped materials or metalloproteins. PMID:25069794

  8. Near-complete 1H, 13C, 15N resonance assignments of dimethylsulfoxide-denatured TGFBIp FAS1-4 A546T.

    PubMed

    Kulminskaya, Natalia V; Yoshimura, Yuichi; Runager, Kasper; Sørensen, Charlotte S; Bjerring, Morten; Andreasen, Maria; Otzen, Daniel E; Enghild, Jan J; Nielsen, Niels Chr; Mulder, Frans A A

    2016-04-01

    The transforming growth factor beta induced protein (TGFBIp) is a major protein component of the human cornea. Mutations occurring in TGFBIp may cause corneal dystrophies, which ultimately lead to loss of vision. The majority of the disease-causing mutations are located in the C-terminal domain of TGFBIp, referred as the fourth fascilin-1 (FAS1-4) domain. In the present study the FAS1-4 Ala546Thr, a mutation that causes lattice corneal dystrophy, was investigated in dimethylsulfoxide using liquid-state NMR spectroscopy, to enable H/D exchange strategies for identification of the core formed in mature fibrils. Isotope-labeled fibrillated FAS1-4 A546T was dissolved in a ternary mixture 95/4/1 v/v/v% dimethylsulfoxide/water/trifluoroacetic acid, to obtain and assign a reference 2D (1)H-(15)N HSQC spectrum for the H/D exchange analysis. Here, we report the near-complete assignments of backbone and aliphatic side chain (1)H, (13)C and (15)N resonances for unfolded FAS1-4 A546T at 25 °C. PMID:26275916

  9. Backbone 1H, 13C and 15N resonance assignments of the 39 kDa staphylococcal hemoglobin receptor IsdH.

    PubMed

    Spirig, Thomas; Clubb, Robert T

    2012-10-01

    During infections Stahpylococcus aureus preferentially uses heme as an iron source, which it captures from human hemoglobin using the Iron regulated surface determinant (Isd) system. On the cell surface two related staphylococcal surface receptors called IsdH and IsdB bind to hemoglobin and extract its heme. Both receptors contain multiple NEAr iron Transporter (NEAT) domains that either bind to hemoglobin, or to heme. All previous structural studies have investigated individual NEAT domains and have not explored how the domains might interact with one another to synergistically extract heme from hemoglobin. Here, we report the near complete (1)H, (13)C and (15)N backbone resonance assignments of a bi-domain unit from IsdH that contains the N2 and N3 NEAT domains, which bind to hemoglobin and heme, respectively (IsdH(N2N3), residues 326-660, 39 kDa). The assigned backbone resonances lay the foundation for future NMR studies that will explore the molecular basis of IsdH function. PMID:22101872

  10. 1H, 13C and 15N resonance assignments of a highly-soluble murine interleukin-3 analogue with wild-type bioactivity.

    PubMed

    Yao, Shenggen; Murphy, James M; Low, Andrew; Norton, Raymond S

    2010-04-01

    Interleukin-3 (IL-3) is a cytokine that acts as a critical mediator of inflammation and immune responses to infections. IL-3, like interleukin-5 (IL-5) and granulocyte-macrophage colony stimulating factor (GM-CSF), exerts its effects on target cells via receptors composed of cytokine-specific alpha-subunits and a common beta-subunit (betac-subunit, shared with IL-5 and GM-CSF). In contrast to humans, mice also possess an additional beta-receptor, beta(IL-3), that can specifically bind IL-3. Except for a study carried out on an analogue of human IL-3 that contains 14 mutations, structure-related studies of IL-3 have been very limited, largely because of its poor solution behaviour. Here we report (1)H, (13)C, and (15)N chemical shift assignments of murine IL-3 comprising residues 33-156 (SWISS-PROT accession number: P01586), in which the only mutation is an alanine substitution of Cys105. The mIL-3 construct used in the present study was engineered by eliminating residues 27-32 of the N-terminus (the first 26 residues of the primary sequence of mIL-3 are cleaved in vivo during secretion), the C-terminal 10 residues (157-166), and a disulfide bond between Cys105 and Cys166 that is poorly conserved in orthologue sequences. The new construct vastly improves the solubility of murine IL-3 while maintaining its wild-type biological activity. PMID:20174897

  11. Assessment of metabolic fluxes in the mouse brain in vivo using 1H-[13C] NMR spectroscopy at 14.1 Tesla.

    PubMed

    Xin, Lijing; Lanz, Bernard; Lei, Hongxia; Gruetter, Rolf

    2015-05-01

    (13)C magnetic resonance spectroscopy (MRS) combined with the administration of (13)C labeled substrates uniquely allows to measure metabolic fluxes in vivo in the brain of humans and rats. The extension to mouse models may provide exclusive prospect for the investigation of models of human diseases. In the present study, the short-echo-time (TE) full-sensitivity (1)H-[(13)C] MRS sequence combined with high magnetic field (14.1 T) and infusion of [U-(13)C6] glucose was used to enhance the experimental sensitivity in vivo in the mouse brain and the (13)C turnover curves of glutamate C4, glutamine C4, glutamate+glutamine C3, aspartate C2, lactate C3, alanine C3, γ-aminobutyric acid C2, C3 and C4 were obtained. A one-compartment model was used to fit (13)C turnover curves and resulted in values of metabolic fluxes including the tricarboxylic acid (TCA) cycle flux VTCA (1.05 ± 0.04 μmol/g per minute), the exchange flux between 2-oxoglutarate and glutamate Vx (0.48 ± 0.02 μmol/g per minute), the glutamate-glutamine exchange rate V(gln) (0.20 ± 0.02 μmol/g per minute), the pyruvate dilution factor K(dil) (0.82 ± 0.01), and the ratio for the lactate conversion rate and the alanine conversion rate V(Lac)/V(Ala) (10 ± 2). This study opens the prospect of studying transgenic mouse models of brain pathologies. PMID:25605294

  12. In vivo quantification of neuro-glial metabolism and glial glutamate concentration using 1H-[13C] MRS at 14.1T.

    PubMed

    Lanz, Bernard; Xin, Lijing; Millet, Philippe; Gruetter, Rolf

    2014-01-01

    Astrocytes have recently become a major center of interest in neurochemistry with the discoveries on their major role in brain energy metabolism. An interesting way to probe this glial contribution is given by in vivo (13) C NMR spectroscopy coupled with the infusion labeled glial-specific substrate, such as acetate. In this study, we infused alpha-chloralose anesthetized rats with [2-(13) C]acetate and followed the dynamics of the fractional enrichment (FE) in the positions C4 and C3 of glutamate and glutamine with high sensitivity, using (1) H-[(13) C] magnetic resonance spectroscopy (MRS) at 14.1T. Applying a two-compartment mathematical model to the measured time courses yielded a glial tricarboxylic acid (TCA) cycle rate (Vg ) of 0.27 ± 0.02 μmol/g/min and a glutamatergic neurotransmission rate (VNT ) of 0.15 ± 0.01 μmol/g/min. Glial oxidative ATP metabolism thus accounts for 38% of total oxidative metabolism measured by NMR. Pyruvate carboxylase (VPC ) was 0.09 ± 0.01 μmol/g/min, corresponding to 37% of the glial glutamine synthesis rate. The glial and neuronal transmitochondrial fluxes (Vx (g) and Vx (n) ) were of the same order of magnitude as the respective TCA cycle fluxes. In addition, we estimated a glial glutamate pool size of 0.6 ± 0.1 μmol/g. The effect of spectral data quality on the fluxes estimates was analyzed by Monte Carlo simulations. In this (13) C-acetate labeling study, we propose a refined two-compartment analysis of brain energy metabolism based on (13) C turnover curves of acetate, glutamate and glutamine measured with state of the art in vivo dynamic MRS at high magnetic field in rats, enabling a deeper understanding of the specific role of glial cells in brain oxidative metabolism. In addition, the robustness of the metabolic fluxes determination relative to MRS data quality was carefully studied. PMID:24117599

  13. NMR profiling of biomolecules at natural abundance using 2D 1H-15N and 1H-13C multiplicity-separated (MS) HSQC spectra

    NASA Astrophysics Data System (ADS)

    Chen, Kang; Freedberg, Darón I.; Keire, David A.

    2015-02-01

    2D NMR 1H-X (X = 15N or 13C) HSQC spectra contain cross-peaks for all XHn moieties. Multiplicity-edited1H-13C HSQC pulse sequences generate opposite signs between peaks of CH2 and CH/CH3 at a cost of lower signal-to-noise due to the 13C T2 relaxation during an additional 1/1JCH period. Such CHn-editing experiments are useful in assignment of chemical shifts and have been successfully applied to small molecules and small proteins (e.g. ubiquitin) dissolved in deuterated solvents where, generally, peak overlap is minimal. By contrast, for larger biomolecules, peak overlap in 2D HSQC spectra is unavoidable and peaks with opposite phases cancel each other out in the edited spectra. However, there is an increasing need for using NMR to profile biomolecules at natural abundance dissolved in water (e.g., protein therapeutics) where NMR experiments beyond 2D are impractical. Therefore, the existing 2D multiplicity-edited HSQC methods must be improved to acquire data on nuclei other than 13C (i.e.15N), to resolve more peaks, to reduce T2 losses and to accommodate water suppression approaches. To meet these needs, a multiplicity-separated1H-X HSQC (MS-HSQC) experiment was developed and tested on 500 and 700 MHz NMR spectrometers equipped with room temperature probes using RNase A (14 kDa) and retroviral capsid (26 kDa) proteins dissolved in 95% H2O/5% D2O. In this pulse sequence, the 1/1JXH editing-period is incorporated into the semi-constant time (semi-CT) X resonance chemical shift evolution period, which increases sensitivity, and importantly, the sum and the difference of the interleaved 1JXH-active and the 1JXH-inactive HSQC experiments yield two separate spectra for XH2 and XH/XH3. Furthermore we demonstrate improved water suppression using triple xyz-gradients instead of the more widely used z-gradient only water-suppression approach.

  14. Heteronuclear proton assisted recoupling

    NASA Astrophysics Data System (ADS)

    De Paëpe, Gaël; Lewandowski, Józef R.; Loquet, Antoine; Eddy, Matt; Megy, Simon; Böckmann, Anja; Griffin, Robert G.

    2011-03-01

    We describe a theoretical framework for understanding the heteronuclear version of the third spin assisted recoupling polarization transfer mechanism and demonstrate its potential for detecting long-distance intramolecular and intermolecular 15N-13C contacts in biomolecular systems. The pulse sequence, proton assisted insensitive nuclei cross polarization (PAIN-CP) relies on a cross term between 1H-15N and 1H-13C dipolar couplings to mediate zero- and/or double-quantum 15N-13C recoupling. In particular, using average Hamiltonian theory we derive effective Hamiltonians for PAIN-CP and show that the transfer is mediated by trilinear terms of the form N±C∓Hz (ZQ) or N±C±Hz (DQ) depending on the rf field strengths employed. We use analytical and numerical simulations to explain the structure of the PAIN-CP optimization maps and to delineate the appropriate matching conditions. We also detail the dependence of the PAIN-CP polarization transfer with respect to local molecular geometry and explain the observed reduction in dipolar truncation. In addition, we demonstrate the utility of PAIN-CP in structural studies with 15N-13C spectra of two uniformly 13C,15N labeled model microcrystalline proteins—GB1, a 56 amino acid peptide, and Crh, a 85 amino acid domain swapped dimer (MW = 2 × 10.4 kDa). The spectra acquired at high magic angle spinning frequencies (ωr/2π > 20 kHz) and magnetic fields (ω0H/2π = 700-900 MHz) using moderate rf fields, yield multiple long-distance intramonomer and intermonomer 15N-13C contacts. We use these distance restraints, in combination with the available x-ray structure as a homology model, to perform a calculation of the monomer subunit of the Crh protein.

  15. Backbone 1H, 13C, and 15N assignments for the tandem ubiquitin binding domains of signal transducing adapter molecule 1.

    PubMed

    Lim, Jongsoo; Hong, Yoon-Hun; Lee, Bong-Jin; Ahn, Hee-Chul

    2011-04-01

    Signal transducing adapter molecule (STAM) forms the endosomal sorting complex required for transport-0 (ESCRT-0) complex with hepatocyte growth factor-regulated substrate (Hrs) to sort the ubiquitinated cargo proteins from the early endosomes to the ESCRT-1 complex. ESCRT-0 complex, STAM and Hrs, contains multiple ubiquitin binding domains, in which STAM has two ubiquitin binding domains, Vps27/Hrs/Stam (VHS) and ubiquitin interacting motif (UIM) at its N-terminus. By the cooperation of the multiple ubiquitin binding domains, the ESCRT-0 complex recognizes poly-ubiquitin, especially Lys63-linked ubiquitin. Here, we report the backbone resonance assignments and the secondary structure of the N-terminal 191 amino acids of the human STAM1 which includes the VHS domain and UIM. The {(1)H}-(15)N heteronuclear NOE experiments revealed that an unstructured and flexible loop region connects the VHS domain and UIM. Our work provides the basic information for the further NMR investigation of the interaction between STAM1 and poly-ubiquitin. PMID:20927613

  16. Resolution enhancement in spectra of natural products dissolved in weakly orienting media with the help of 1H homonuclear dipolar decoupling during acquisition: Application to 1H- 13C dipolar couplings measurements

    NASA Astrophysics Data System (ADS)

    Farjon, Jonathan; Bermel, Wolfgang; Griesinger, Christian

    2006-05-01

    In weakly orienting media such as poly-γ-benzyl- L-glutamate (PBLG) a polymer that forms a chiral liquid crystal in organic solvents, the spectral resolution for embedded molecules is usually poor because of numerous 1H, 1H dipolar couplings that generally broaden proton spectra. Therefore 1H, 13C dipolar couplings are difficult or impossible to measure. Here, we incorporate Flip-Flop decoupling during detection into an HSQC experiment. Flip-Flop removes the 1H, 1H dipolar couplings and scales the chemical shifts of the protons as well as the 1H, 13C dipolar couplings during detection. A resolution gain by a factor 1.5-4.2 and improved signal intensity by an average factor of 1.6-1.7 have been obtained. This technique is demonstrated on (+)-menthol dissolved in a PBLG/CDCl 3 phase.

  17. (1)H, (13)C and (15)N backbone and side-chain resonance assignment of the LAM-RRM1 N-terminal module of La protein from Dictyostelium discoideum.

    PubMed

    Chasapis, Christos T; Argyriou, Aikaterini I; Apostolidi, Maria; Konstantinidou, Parthena; Bentrop, Detlef; Stathopoulos, Constantinos; Spyroulias, Georgios A

    2015-10-01

    The N-terminal half of La protein consists of two concatenated motifs: La motif (LAM) and the N-terminal RNA recognition motif (RRM1) both of which are responsible for poly(U) RNA binding. Here, we present the backbone and side-chain assignments of the (1)H, (13)C and (15)N resonances of the 191-residue LAM-RRM1 region of the La protein from the lower eukaryote Dictyostelium discoideum and its secondary structure prediction. PMID:25687647

  18. (1)H-(13)C-(29)Si triple resonance and REDOR solid-state NMR-A tool to study interactions between biosilica and organic molecules in diatom cell walls.

    PubMed

    Wisser, Dorothea; Brückner, Stephan I; Wisser, Florian M; Althoff-Ospelt, Gerhard; Getzschmann, Jürgen; Kaskel, Stefan; Brunner, Eike

    2015-01-01

    Triple resonance solid-state NMR experiments using the spin combination (1)H-(13)C-(29)Si are still rarely found in the literature. This is due to the low natural abundance of the two heteronuclei. Such experiments are, however, increasingly important to study hybrid materials such as biosilica and others. A suitable model substance, ideally labeled with both (13)C and (29)Si, is thus very useful to optimize the experiments before applying them to studies of more complex samples such as biosilica. Tetraphenoxysilane could be synthesized in an easy, two-step synthesis including double isotope labelling. Using tetraphenoxysilane, we established a (1)H-(13)C-(29)Si double CP-based HETCOR experiment and applied it to diatom biosilica from the diatom species Thalassiosira pseudonana. Furthermore, we carried out (1)H-(13)C{(29)Si} CP-REDOR experiments in order to estimate the distance between the organic matrix and the biosilica. Our experiments on diatom biosilica strongly indicate a close contact between polyamine-containing parts of the organic matrix and the silica. This corroborates the assumption that the organic matrix is essential for the control of the cell wall formation. PMID:25638422

  19. Heteronuclear J-coupling measurements in grossly inhomogeneous magnetic fields.

    PubMed

    Mandal, S; Song, Y-Q

    2015-06-01

    It is difficult to measure chemical shifts in the small and inhomogeneous magnetic fields found in ex situ and single-sided NMR systems, such as those used for well-logging. However, it is still possible to obtain chemical information from J-coupling constants, which are independent of static field strength and temperature. We describe and analyze (1)H-(13)C double-resonance pulse sequences that are suitable for measuring heteronuclear J-coupling in grossly inhomogeneous fields. We also present preliminary experimental results from a low-frequency fringe-field system. PMID:25898398

  20. Heteronuclear correlations by multiple-quantum evolution. II. Proton-proton "decoupling" and multiplicity labeling in a constant-time experiment using carbon detection

    NASA Astrophysics Data System (ADS)

    Batta, Gyula; Kövér, Katalin E.

    Modified Müller-Bolton type heteronuclear multiple-quantum correlation experiments are analyzed theoretically and experimentally. It is shown that the constant-time version offers homonuclear decoupling, multiplicity labeling, and a very efficient suppression of strong coupling artifacts. Such sequences may have advantages for studying macromolecules.

  1. Hydrothermal liquefaction oil and hydrotreated product from pine feedstock characterized by heteronuclear two-dimensional NMR spectroscopy and FT-ICR mass spectrometry

    SciTech Connect

    Sudasinghe, Nilusha; Cort, John R.; Hallen, Richard; Olarte, Mariefel; Schmidt, Andrew; Schaub, Tanner

    2014-12-01

    Hydrothermal liquefaction (HTL) crude oil and hydrotreated product from pine tree farm waste (forest product residual, FPR) have been analyzed by direct infusion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) in both positive- and negative-ionization modes and high-resolution twodimensional heteronuclear 1H-13C NMR spectroscopy. FT-ICR MS resolves thousands of compounds in complex oils and provides unparalleled compositional details for individual molecules for identification of compound class (heteroatom content), type (number of rings plus double bonds to carbon or double bond equivalents (DBE) and carbon number (degree of alkylation). Heteronuclear 1H-13C NMR spectroscopy provides one-bond and multiple-bond correlations between pairs of 1H and 13C chemical shifts that are characteristic of different organic functional groups. Taken together this information provides a picture of the chemical composition of these oils. Pyrolysis crude oil product from pine wood was characterized for comparison. Generally, pyrolysis oil is comprised of a more diverse distribution of heteroatom classes with higher oxygen number relative to HTL oil as shown by both positive- and negative-ion ESI FT-ICR MS. A total of 300 N1, 594 O1 and 267 O2 compounds were observed as products of hydrotreatment. The relative abundance of N1O1, N1O2, N1O3, N2, N2O1, N2O2 and O3 compounds are reduced to different degrees after hydrotreatment and other higher heteroatom containing species (O4-O10, N1O4, N1O5 and N2O3) are completely removed by hydrotreatment.

  2. A different approach to multiplicity-edited heteronuclear single quantum correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Sakhaii, Peyman; Bermel, Wolfgang

    2015-10-01

    A new experiment for recording multiplicity-edited HSQC spectra is presented. In standard multiplicity-edited HSQC experiments, the amplitude of CH2 signals is negative compared to those of CH and CH3 groups. We propose to reverse the sign of 13C frequencies of CH2 groups in t1 as criteria for editing. Basically, a modified [BIRD]r,x element (Bilinear Rotation Pulses and Delays) is inserted in a standard HSQC pulse sequence with States-TPPI frequency detection in t1 for this purpose. The modified BIRD element was designed in such a way as to pass or stop the evolution of the heteronuclear 1JHC coupling. This is achieved by adding a 180° proton RF pulse in each of the 1/2J periods. Depending on their position the evolution is switched on or off. Usually, the BIRD- element is applied on real and imaginary increments of a HSQC experiment to achieve the editing between multiplicities. Here, we restrict the application of the modified BIRD element to either real or imaginary increments of the HSQC. With this new scheme for editing, changing the frequency and/or amplitude of the CH2 signals becomes available. Reversing the chemical shift axis for CH2 signals simplifies overcrowded frequency regions and thus avoids accidental signal cancellation in conventional edited HSQC experiments. The practical implementation is demonstrated on the protein Lysozyme. Advantages and limitations of the idea are discussed.

  3. A different approach to multiplicity-edited heteronuclear single quantum correlation spectroscopy.

    PubMed

    Sakhaii, Peyman; Bermel, Wolfgang

    2015-10-01

    A new experiment for recording multiplicity-edited HSQC spectra is presented. In standard multiplicity-edited HSQC experiments, the amplitude of CH2 signals is negative compared to those of CH and CH3 groups. We propose to reverse the sign of (13)C frequencies of CH2 groups in t1 as criteria for editing. Basically, a modified [BIRD](r,x) element (Bilinear Rotation Pulses and Delays) is inserted in a standard HSQC pulse sequence with States-TPPI frequency detection in t1 for this purpose. The modified BIRD element was designed in such a way as to pass or stop the evolution of the heteronuclear (1)JHC coupling. This is achieved by adding a 180° proton RF pulse in each of the 1/2J periods. Depending on their position the evolution is switched on or off. Usually, the BIRD- element is applied on real and imaginary increments of a HSQC experiment to achieve the editing between multiplicities. Here, we restrict the application of the modified BIRD element to either real or imaginary increments of the HSQC. With this new scheme for editing, changing the frequency and/or amplitude of the CH2 signals becomes available. Reversing the chemical shift axis for CH2 signals simplifies overcrowded frequency regions and thus avoids accidental signal cancellation in conventional edited HSQC experiments. The practical implementation is demonstrated on the protein Lysozyme. Advantages and limitations of the idea are discussed. PMID:26298081

  4. Experimental and quantum-chemical studies of 1H, 13C and 15N NMR coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with picolines.

    PubMed

    Pazderski, Leszek; Tousek, Jaromír; Sitkowski, Jerzy; Malináková, Katerina; Kozerski, Lech; Szłyk, Edward

    2009-03-01

    (1)H, (13)C and (15)N NMR studies of gold(III), palladium(II) and platinum(II) chloride complexes with picolines, [Au(PIC)Cl(3)], trans-[Pd(PIC)(2)Cl(2)], trans/cis-[Pt(PIC)(2)Cl(2)] and [Pt(PIC)(4)]Cl(2), were performed. After complexation, the (1)H and (13)C signals were shifted to higher frequency, whereas the (15)N ones to lower (by ca 80-110 ppm), with respect to the free ligands. The (15)N shielding phenomenon was enhanced in the series [Au(PIC)Cl(3)] < trans-[Pd(PIC)(2)Cl(2)] < cis-[Pt(PIC)(2)Cl(2)] < trans-[Pt(PIC)(2)Cl(2)]; it increased following the Pd(II) --> Pt(II) replacement, but decreased upon the trans --> cis-transition. Experimental (1)H, (13)C and (15)N NMR chemical shifts were compared to those quantum-chemically calculated by B3LYP/LanL2DZ + 6-31G**//B3LYP/LanL2DZ + 6-31G*. PMID:19097135

  5. 1H, 13C and 15N NMR coordination shifts in gold(III), cobalt(III), rhodium(III) chloride complexes with pyridine, 2,2'-bipyridine and 1,10-phenanthroline.

    PubMed

    Pazderski, Leszek; Tousek, Jaromír; Sitkowski, Jerzy; Kozerski, Lech; Marek, Radek; Szłyk, Edward

    2007-01-01

    Au(III), Co(III) and Rh(III) chloride complexes with pyridine (py), 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) of the general formulae [M1LCl3], trans-[M2L4Cl2]+, mer-[M2L3Cl3], [M1(LL)Cl2]+, cis-[M2(LL)2Cl2]+, where M1=Au; M2=Co, Rh; L=py; LL=bpy, phen, were studied by 1H--13C HMBC and 1H--15N HMQC/HSQC. The 1H, 13C and 15N coordination shifts (the latter from ca-78 to ca-107 ppm) are discussed in relation to the type of metal, electron configuration, coordination sphere geometry and the type of ligand. The 13C and 15N chemical shifts were also calculated by quantum-chemical NMR methods, which reproduced well the experimental tendencies concerning the coordination sphere geometry and the ligand type. PMID:17048265

  6. Comprehensive quantum chemical and spectroscopic (FTIR, FT-Raman, 1H, 13C NMR) investigations of O-desmethyltramadol hydrochloride an active metabolite in tramadol - An analgesic drug

    NASA Astrophysics Data System (ADS)

    Arjunan, V.; Santhanam, R.; Marchewka, M. K.; Mohan, S.

    2014-03-01

    O-desmethyltramadol is one of the main metabolites of tramadol widely used clinically and has analgesic activity. The FTIR and FT-Raman spectra of O-desmethyl tramadol hydrochloride are recorded in the solid phase in the regions 4000-400 cm-1 and 4000-100 cm-1, respectively. The observed fundamentals are assigned to different normal modes of vibration. Theoretical studies have been performed as its hydrochloride salt. The structure of the compound has been optimised with B3LYP method using 6-31G** and cc-pVDZ basis sets. The optimised bond length and bond angles are correlated with the X-ray data. The experimental wavenumbers were compared with the scaled vibrational frequencies determined by DFT methods. The IR and Raman intensities are determined with B3LYP method using cc-pVDZ and 6-31G(d,p) basic sets. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/cc-pVDZ method to display electrostatic potential (electron + nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of O-desmethyltramadol hydrochloride has been performed to indicate the presence of intramolecular charge transfer. The 1H and 13C NMR chemical shifts of the molecule have been anlysed.

  7. Application of unsymmetrical indirect covariance NMR methods to the computation of the (13)C <--> (15)N HSQC-IMPEACH and (13)C <--> (15)N HMBC-IMPEACH correlation spectra.

    PubMed

    Martin, Gary E; Hilton, Bruce D; Irish, Patrick A; Blinov, Kirill A; Williams, Antony J

    2007-10-01

    Utilization of long-range (1)H--(15)N heteronuclear chemical shift correlation has continually grown in importance since the first applications were reported in 1995. More recently, indirect covariance NMR methods have been introduced followed by the development of unsymmetrical indirect covariance processing methods. The latter technique has been shown to allow the calculation of hyphenated 2D NMR data matrices from more readily acquired nonhyphenated 2D NMR spectra. We recently reported the use of unsymmetrical indirect covariance processing to combine (1)H--(13)C GHSQC and (1)H--(15)N GHMBC long-range spectra to yield a (13)C--(15)N HSQC-HMBC chemical shift correlation spectrum that could not be acquired in a reasonable period of time without resorting to (15)N-labeled molecules. We now report the unsymmetrical indirect covariance processing of (1)H--(13)C GHMBC and (1)H--(15)N IMPEACH spectra to afford a (13)C--(15)N HMBC-IMPEACH spectrum that has the potential to span as many as six to eight bonds. Correlations for carbon resonances long-range coupled to a protonated carbon in the (1)H--(13)C HMBC spectrum are transferred via the long-range (1)H--(15)N coupling pathway in the (1)H--(15)N IMPEACH spectrum to afford a much broader range of correlation possibilities in the (13)C--(15)N HMBC-IMPEACH correlation spectrum. The indole alkaloid vincamine is used as a model compound to illustrate the application of the method. PMID:17729230

  8. Determination of size and sign of hetero-nuclear coupling constants from 2D 19F-13C correlation spectra

    NASA Astrophysics Data System (ADS)

    Ampt, Kirsten A. M.; Aspers, Ruud L. E. G.; Dvortsak, Peter; van der Werf, Ramon M.; Wijmenga, Sybren S.; Jaeger, Martin

    2012-02-01

    Fluorinated organic compounds have become increasingly important within the polymer and the pharmaceutical industry as well as for clinical applications. For the structural elucidation of such compounds, NMR experiments with fluorine detection are of great value due to the favorable NMR properties of the fluorine nucleus. For the investigation of three fluorinated compounds, triple resonance 2D HSQC and HMBC experiments were adopted to fluorine detection with carbon and/or proton decoupling to yield F-C, F-C{H}, F-C{Cacq} and F-C{H,Cacq} variants. Analysis of E.COSY type cross-peak patterns in the F-C correlation spectra led, apart from the chemical shift assignments, to determination of size and signs of the JCH, JCF, and JHF coupling constants. In addition, the fully coupled F-C HMQC spectrum of steroid 1 was interpreted in terms of E.COSY type patterns. This example shows how coupling constants due to different nuclei can be determined together with their relative signs from a single spectrum. The analysis of cross-peak patterns, as presented here, not only provides relatively straightforward routes to the determination of size and sign of hetero-nuclear J-couplings in fluorinated compounds, it also provides new and easy ways for the determination of residual dipolar couplings and thus for structure elucidation. The examples and results presented in this study may contribute to a better interpretation and understanding of various F-C correlation experiments and thereby stimulate their utilization.

  9. Heteronuclear 19F-1H statistical total correlation spectroscopy as a tool in drug metabolism: study of flucloxacillin biotransformation.

    PubMed

    Keun, Hector C; Athersuch, Toby J; Beckonert, Olaf; Wang, Yulan; Saric, Jasmina; Shockcor, John P; Lindon, John C; Wilson, Ian D; Holmes, Elaine; Nicholson, Jeremy K

    2008-02-15

    We present a novel application of the heteronuclear statistical total correlation spectroscopy (HET-STOCSY) approach utilizing statistical correlation between one-dimensional 19F/1H NMR spectroscopic data sets collected in parallel to study drug metabolism. Parallel one-dimensional (1D) 800 MHz 1H and 753 MHz 19F{1H} spectra (n = 21) were obtained on urine samples collected from volunteers (n = 6) at various intervals up to 24 h after oral dosing with 500 mg of flucloxacillin. A variety of statistical relationships between and within the spectroscopic datasets were explored without significant loss of the typically high 1D spectral resolution, generating 1H-1H STOCSY plots, and novel 19F-1H HET-STOCSY, 19F-19F STOCSY, and 19F-edited 1H-1H STOCSY (X-STOCSY) spectroscopic maps, with a resolution of approximately 0.8 Hz/pt for both nuclei. The efficient statistical editing provided by these methods readily allowed the collection of drug metabolic data and assisted structure elucidation. This approach is of general applicability for studying the metabolism of other fluorine-containing drugs, including important anticancer agents such as 5-fluorouracil and flutamide, and is extendable to any drug metabolism study where there is a spin-active X-nucleus (e.g., 13C, 15N, 31P) label present. PMID:18211034

  10. 1H, 13C, 15N NMR coordination shifts in Fe(II), Ru(II) and Os(II) cationic complexes with 2,2':6',2″-terpyridine.

    PubMed

    Pazderski, Leszek; Pawlak, Tomasz; Sitkowski, Jerzy; Kozerski, Lech; Szlyk, Edward

    2011-05-01

    (1)H, (13)C and (15)N NMR studies of iron(II), ruthenium(II) and osmium(II) bis-chelated cationic complexes with 2,2':6',2″-terpyridine ([M(terpy)(2) ](2+) ; M = Fe, Ru, Os) were performed. Significant shielding of nitrogen-adjacent H(6) and deshielding of H(3'), H(4') protons were observed, both effects being mostly expressed for Fe(II) compounds. The metal-bonded nitrogens were shielded, this effect being much larger for the outer N(1), N(1″) than the inner N(1') atoms, and enhanced in the Fe(II) → Ru(II) → Os(II) series. PMID:21491480

  11. Spectroscopic characterization of the 1-substituted 3,3-diphenyl-4-(2'-hydroxyphenyl)azetidin-2-ones: Application of 13C NMR, 1H- 13C COSY NMR and mass spectroscopy

    NASA Astrophysics Data System (ADS)

    Singh, Girija S.; Pheko, Tshepo

    2008-08-01

    The article deals with spectroscopic characterization of azetidin-2-ones. The presence of substituents like hydroxyl, fluoro, methoxy and benzhydryl, etc., on the azetidin-2-one ring significantly affects the IR absorption and 13C NMR frequencies of the carbonyl group present in these compounds. The presence of an ester carbonyl group or too many methine protons in the molecule has been observed to limit the scope of IR and 1H NMR spectroscopy in unambiguous assignment of the structure. The application of 13C NMR, 2D NMR ( 1H- 13C COSY) and mass spectroscopy in characterization of complex azetidin-2-ones is discussed. An application of the latter two techniques is described in deciding unequivocally between an azetidin-2-one ring and chroman-2-one ring structure for the product obtained by treatment of the 1-substituted 3,3-diphenyl-4-[2'-( O-diphenylacyl)hydroxyphenyl]-2-azetidinones with ethanolic sodium hydroxide at room temperature.

  12. Studies of minute quantities of natural abundance molecules using 2D heteronuclear correlation spectroscopy under 100kHz MAS

    SciTech Connect

    Nishiyama, Y.; Kobayashi, T.; Malon, M.; Singappuli-Arachchige, D.; Slowing, I. I.; Pruski, M.

    2015-02-16

    Two-dimensional 1H{13C} heteronuclear correlation solid-state NMR spectra of naturally abundant solid materials are presented, acquired using the 0.75-mm magic angle spinning (MAS) probe at spinning rates up to 100 kHz. In spite of the miniscule sample volume (290 nL), high-quality HSQC-type spectra of bulk samples as well as surface-bound molecules can be obtained within hours of experimental time. The experiments are compared with those carried out at 40 kHz MAS using a 1.6-mm probe, which offered higher overall sensitivity due to a larger rotor volume. The benefits of ultrafast MAS in such experiments include superior resolution in 1H dimension without resorting to 1H–1H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. As a result, the HMQC spectra of surface-bound species can be also acquired under 100 kHz MAS, although the dephasing of transverse magnetization has significant effect on the efficiency transfer under MAS alone.

  13. Secondary structure and zinc ligation of human recombinant short-form stromelysin by multidimensional heteronuclear NMR.

    PubMed

    Gooley, P R; Johnson, B A; Marcy, A I; Cuca, G C; Salowe, S P; Hagmann, W K; Esser, C K; Springer, J P

    1993-12-01

    Stromelysin-1, a member of the matrix metalloendoprotease family, is a zinc protease involved in the degradation of connective tissue in the extracellular matrix. As a step toward determining the structure of this protein, multidimensional heteronuclear NMR experiments have been applied to an inhibited truncated form of human stromelysin-1. Extensive 1H, 13C, and 15N sequential assignments have been obtained with a combination of three- and four-dimensional experiments. On the basis of sequential and short-range NOEs and 13C alpha chemical shifts, two helices have been delineated, spanning residues Asp-111 to Val-127 and Leu-195 to Ser-206. A third helix spanning residues Asp-238 to Gly-247 is characterized by sequential NOEs and 13C alpha chemical shifts, but not short-range NOEs. The lack of the latter NOEs suggests that this helix is either distorted or mobile. Similarly, sequential and interstrand NOEs and 13C alpha chemical shifts characterize a four-stranded beta-sheet with three parallel strands (Arg-100 to Ile-101, Ile-142 to Ala-147, Asp-177 to Asp-181) and one antiparallel strand (Ala-165 to Tyr-168). Two zinc sites have been identified in stromelysin [Salowe et al. (1992) Biochemistry 31, 4535-4540]. The NMR spectral properties, including chemical shift, pH dependence, and proton coupling of the imidazole nitrogens of six histidine residues (151, 166, 179, 201, 205, and 211), invariant in the matrix metalloendoprotease family, suggest that these residues are zinc ligands. NOE data indicate that these histidines form two clusters: one ligates the catalytic zinc (His-201, -205, and -211), and the other ligates a structural zinc (His-151, -166, and -179). Heteronuclear multiple quantum correlated spectra and specific labeling experiments indicate His-151, -179, -201, -205, and -211 are in the N delta 1H tautomer and His-166 is in the N epsilon 2H tautomer. PMID:8241164

  14. Experimental and quantum-chemical studies of 1H, 13C and 15N NMR coordination shifts in Pd(II) and Pt(II) chloride complexes with quinoline, isoquinoline, and 2,2'-biquinoline.

    PubMed

    Pazderski, Leszek; Tousek, Jaromír; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2007-12-01

    1H, 13C, and 15N NMR studies of platinide(II) (M=Pd, Pt) chloride complexes with quinolines (L=quinoline-quin, or isoquinoline-isoquin; LL=2,2'-biquinoline-bquin), having the general formulae trans-/cis-[ML2Cl2] and [M(LL)Cl2], were performed and the respective chemical shifts (delta1H, delta13C, delta15N) reported. 1H coordination shifts of various signs and magnitudes (Delta1Hcoord=delta1Hcomplex-delta1Hligand) are discussed in relation to the changes of diamagnetic contribution to the relevant 1H shielding constants. The comparison to the literature data for similar complexes containing auxiliary ligands other than chlorides exhibited a large dependence of delta1H parameters on electron density variations and ring-current effects (inductive and anisotropic phenomena). The influence of deviations from planarity, concerning either MN2Cl2 chromophores or azine ring systems, revealed by the known X-ray structures of [Pd(bquin)Cl2] and [Pt(bquin)Cl2], is discussed in respect to 1H NMR spectra. 15N coordination shifts (Delta15Ncoord=delta15Ncomplex-delta15Nligand) of ca. 78-100 ppm (to lower frequency) are attributed mainly to the decrease of the absolute value of paramagnetic contribution in the relevant 15N shielding constants, this phenomenon being noticeably dependent on the type of a platinide metal and coordination sphere geometry. The absolute magnitude of Delta15Ncoord parameter increased by ca 15 ppm upon Pd(II)-->Pt(II) replacement but decreased by ca. 15 ppm following trans-->cis transition. Experimental 1H, 13C, 15N NMR chemical shifts are compared to those quantum-chemically calculated by B3LYP/LanL2DZ+6-31G**//B3LYP/LanL2DZ+6-31G*, both in vacuo and in CHCl3 or DMF solution. PMID:18044805

  15. Study of stereospecificity of 1H, 13C, 15N and 77Se shielding constants in the configurational isomers of the selenophene-2-carbaldehyde azine by NMR spectroscopy and MP2-GIAO calculations.

    PubMed

    Afonin, Andrei V; Pavlov, Dmitry V; Albanov, Alexander I; Levanova, Ekaterina P; Levkovskaya, Galina G

    2011-11-01

    In the (1)H and (13)C NMR spectra of selenophene-2-carbaldehyde azine, the (1)H-5, (13)C-3 and (13)C-5 signals of the selenophene ring are shifted to higher frequencies, whereas those of the (1)H-1, (13)C-1, (13)C-2 and (13)C-4 are shifted to lower frequencies on going from the EE to ZZ isomer or from the E moiety to the Z moiety of EZ isomer. The (15)N chemical shift is significantly larger in the EE isomer relative to the ZZ isomer and in the E moiety relative to the Z moiety of EZ isomer. A very pronounced difference (60-65 mg/g) between the (77)Se resonance positions is revealed in the studied azine isomers, the (77)Se peak being shifted to higher frequencies in the ZZ isomer and in the Z moiety of EZ isomer. The trends in the changes of the measured chemical shifts are reasonably reproduced by the GIAO calculations at the MP2 level of the (1)H, (13)C, (15)N and (77)Se shielding constants in the energy-favorable conformation with the syn orientation of both selenophene rings relative to the C = N groups. The NBO analysis suggests that such an arrangement of the selenophene rings may take place because of a higher energy of some intramolecular interactions. PMID:22002712

  16. 1H, 13C, 15N backbone and side chain NMR resonance assignments for the N-terminal RNA recognition motif of the HvGR-RBP1 protein involved in the regulation of barley (Hordeum vulgare L.) senescence

    PubMed Central

    Mason, Katelyn E.; Tripet, Brian P.; Parrott, David; Fischer, Andreas M.; Copié, Valérie

    2013-01-01

    Leaf senescence is an important process in the developmental life of all plant species. Senescence efficiency influences important agricultural traits such as grain protein content and plant growth, which are often limited by nitrogen use. Little is known about the molecular mechanisms regulating this highly orchestrated process. To enhance our understanding of leaf senescence and its regulation, we have undertaken the structural and functional characterization of previously unknown proteins that are involved in the control of senescence in barley (Hordeum vulgare L.). Previous microarray analysis highlighted several barley genes whose transcripts are differentially expressed during senescence, including a specific gene which is greater than 40 fold up-regulated in the flag leaves of early- as compared to late-senescing near-isogenic barley lines at 14 and 21 days past flowering (anthesis). From inspection of its amino acid sequence, this gene is predicted to encode a glycine-rich RNA-binding protein herein referred to as HvGR-RBP1. HvGR-RBP1 has been expressed as a recombinant protein in E. coli, and preliminary NMR data analysis has revealed that its glycine-rich C-terminal region [residues: 93–162] is structurally disordered whereas its N-terminal region [residues: 1–92] forms a well-folded domain. Herein, we report the complete 1H, 13C, and 15N resonance assignments of backbone and sidechain atoms, and the secondary structural topology of the N-terminal RNA Recognition Motif (RRM) domain of HvGR-RBP1, as a first step to unraveling its structural and functional role in the regulation of barley leaf senescence. PMID:23417794

  17. Study of conformations and hydrogen bonds in the configurational isomers of pyrrole-2-carbaldehyde oxime by 1H, 13C and 15N NMR spectroscopy combined with MP2 and DFT calculations and NBO analysis.

    PubMed

    Afonin, Andrei V; Ushakov, Igor A; Pavlov, Dmitry V; Ivanov, Andrei V; Mikhaleva, Al'bina I

    2010-09-01

    The (1)H, (13)C and (15)N NMR studies have shown that the E and Z isomers of pyrrole-2-carbaldehyde oxime adopt preferable conformation with the syn orientation of the oxime group with respect to the pyrrole ring. The syn conformation of E and Z isomers of pyrrole-2-carbaldehyde oxime is stabilized by the N-H...N and N-H...O intramolecular hydrogen bonds, respectively. The N-H...N hydrogen bond in the E isomer causes the high-frequency shift of the bridge proton signal by about 1 ppm and increase the (1)J(N, H) coupling by approximately 3 Hz. The bridge proton shows further deshielding and higher increase of the (1)J(N, H) coupling constant due to the strengthening of the N-H...O hydrogen bond in the Z isomer. The MP2 calculations indicate that the syn conformation of E and Z isomers is by approximately 3.5 kcal/mol energetically less favorable than the anti conformation. The calculations of (1)H shielding and (1)J(N, H) coupling in the syn and anti conformations allow the contribution to these constants from the N-H...N and N-H...O hydrogen bondings to be estimated. The NBO analysis suggests that the N-H...N hydrogen bond in the E isomer is a pure electrostatic interaction while the charge transfer from the oxygen lone pair to the antibonding orbital of the N-H bond through the N-H...O hydrogen bond occurs in the Z isomer. PMID:20623827

  18. Measurement of absolute concentrations of individual compounds in metabolite mixtures by gradient-selective time-zero 1H-13C HSQC with two concentration references and fast maximum likelihood reconstruction analysis.

    PubMed

    Hu, Kaifeng; Ellinger, James J; Chylla, Roger A; Markley, John L

    2011-12-15

    Time-zero 2D (13)C HSQC (HSQC(0)) spectroscopy offers advantages over traditional 2D NMR for quantitative analysis of solutions containing a mixture of compounds because the signal intensities are directly proportional to the concentrations of the constituents. The HSQC(0) spectrum is derived from a series of spectra collected with increasing repetition times within the basic HSQC block by extrapolating the repetition time to zero. Here we present an alternative approach to data collection, gradient-selective time-zero (1)H-(13)C HSQC(0) in combination with fast maximum likelihood reconstruction (FMLR) data analysis and the use of two concentration references for absolute concentration determination. Gradient-selective data acquisition results in cleaner spectra, and NMR data can be acquired in both constant-time and non-constant-time mode. Semiautomatic data analysis is supported by the FMLR approach, which is used to deconvolute the spectra and extract peak volumes. The peak volumes obtained from this analysis are converted to absolute concentrations by reference to the peak volumes of two internal reference compounds of known concentration: DSS (4,4-dimethyl-4-silapentane-1-sulfonic acid) at the low concentration limit (which also serves as chemical shift reference) and MES (2-(N-morpholino)ethanesulfonic acid) at the high concentration limit. The linear relationship between peak volumes and concentration is better defined with two references than with one, and the measured absolute concentrations of individual compounds in the mixture are more accurate. We compare results from semiautomated gsHSQC(0) with those obtained by the original manual phase-cycled HSQC(0) approach. The new approach is suitable for automatic metabolite profiling by simultaneous quantification of multiple metabolites in a complex mixture. PMID:22029275

  19. HN-NCA heteronuclear TOCSY-NH experiment for (1)H(N) and (15)N sequential correlations in ((13)C, (15)N) labelled intrinsically disordered proteins.

    PubMed

    Wiedemann, Christoph; Goradia, Nishit; Häfner, Sabine; Herbst, Christian; Görlach, Matthias; Ohlenschläger, Oliver; Ramachandran, Ramadurai

    2015-10-01

    A simple triple resonance NMR experiment that leads to the correlation of the backbone amide resonances of each amino acid residue 'i' with that of residues 'i-1' and 'i+1' in ((13)C, (15)N) labelled intrinsically disordered proteins (IDPs) is presented. The experimental scheme, {HN-NCA heteronuclear TOCSY-NH}, exploits the favourable relaxation properties of IDPs and the presence of (1) J CαN and (2) J CαN couplings to transfer the (15)N x magnetisation from amino acid residue 'i' to adjacent residues via the application of a band-selective (15)N-(13)C(α) heteronuclear cross-polarisation sequence of ~100 ms duration. Employing non-uniform sampling in the indirect dimensions, the efficacy of the approach has been demonstrated by the acquisition of 3D HNN chemical shift correlation spectra of α-synuclein. The experimental performance of the RF pulse sequence has been compared with that of the conventional INEPT-based HN(CA)NH pulse scheme. As the availability of data from both the HCCNH and HNN experiments will make it possible to use the information extracted from one experiment to simplify the analysis of the data of the other and lead to a robust approach for unambiguous backbone and side-chain resonance assignments, a time-saving strategy for the simultaneous collection of HCCNH and HNN data is also described. PMID:26282620

  20. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2016-01-01

    Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D 1H/13C/1H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t1 and t3 periods, respectively. In addition to through-space and through-bond 13C/1H and 13C/13C chemical shift correlations, the 3D 1H/13C/1H experiment also provides a COSY-type 1H/1H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices (1H/1H chemical shift correlation spectrum) at different 13C chemical shift frequencies from the 3D 1H/13C/1H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D 1H/13C/1H experiment would be useful to study the structure and dynamics of a variety of chemical and biological

  1. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS.

    PubMed

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2016-01-21

    Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D (1)H/(13)C/(1)H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t1 and t3 periods, respectively. In addition to through-space and through-bond (13)C/(1)H and (13)C/(13)C chemical shift correlations, the 3D (1)H/(13)C/(1)H experiment also provides a COSY-type (1)H/(1)H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices ((1)H/(1)H chemical shift correlation spectrum) at different (13)C chemical shift frequencies from the 3D (1)H/(13)C/(1)H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D (1)H/(13)C/(1)H experiment would be useful to study the structure and dynamics of

  2. Tailored real-time scaling of heteronuclear couplings

    NASA Astrophysics Data System (ADS)

    Schilling, Franz; Glaser, Steffen J.

    2012-10-01

    Heteronuclear couplings are a valuable source of molecular information, which is measured from the multiplet splittings of an NMR spectrum. Radiofrequency irradiation on one coupled nuclear spin allows to modify the effective coupling constant, scaling down the multiplet splittings in the spectrum observed at the resonance frequency of the other nuclear spin. Such decoupling sequences are often used to collapse a multiplet into a singlet and can therefore simplify NMR spectra significantly. Continuous-wave (cw) decoupling has an intrinsic non-linear offset dependence of the scaling of the effective J-coupling constant. Using optimal control pulse optimization, we show that virtually arbitrary off-resonance scaling of the J-coupling constant can be achieved. The new class of tailored decoupling pulses is named SHOT (Scaling of Heteronuclear couplings by Optimal Tracking). Complementing cw irradiation, SHOT pulses offer an alternative approach of encoding chemical shift information indirectly through off-resonance decoupling, which however makes it possible for the first time to achieve linear J scaling as a function of offset frequency. For a simple mixture of eight aromatic compounds, it is demonstrated experimentally that a 1D-SHOT {1H}-13C experiment yields comparable information to a 2D-HSQC and can give full assignment of all coupled spins.

  3. Electron correlation and relativistic effects in the coinage metal compounds. II. Heteronuclear dimers: CuAg, CuAu, and AgAu

    NASA Astrophysics Data System (ADS)

    Kellö, Vladimir; Sadlej, Andrzej J.

    1995-08-01

    Electric properties of heteronuclear dimers of the coinage metals are calculated at the level of the CCSD(T) approximation applied to 38 electrons of the valence and next-to-valence atomic shells. The relativistic effects are accounted for by using the scalar approximation to the Pauli hamiltonian. Both the pure relativistic and mixed relativistic-correlation contributions to energies and electric properties are computed. All calculations have been carried out by using the recently developed first-order polarized basis sets of the coinage metal atoms. In the non-relativistic approximation all studied dimers show only a moderate degree of polarity; the non-relativistic CuAg turns out to be the most polar dimer with the Cu(-)Ag(+) polarity. The relativistic effects considerably reduce the negative value of the CuAg dipole moment, change the sign of the CuAu dipole moment, and make the AgAu molecule the most polar species in the series. Simultaneously, the parallel component of the dipole polarizability shows only a small relativistic contraction. The calculated quasirelativistic interaction potentials have a correct behavior in the vicinity of their minima and give the Re and ωe values in complete agreement with experiment. Much less satisfactory are the dissociation energy data which seem to suffer from the single reference configuration approximation.

  4. Multiplet-separated heteronuclear two-dimensional NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Levitt, Malcolm H.; Sørensen, O. W.; Ernst, R. R.

    1983-02-01

    Techniques are described for the identification and separation of peaks of different multiplicity in heteronuclear two-dimensional NMR spectroscopy. The methods are applied to the two-dimensional 13C- 1H shift correlation spectrum of menthol.

  5. Design of Heteronuclear Metalloenzymes.

    PubMed

    Bhagi-Damodaran, A; Hosseinzadeh, P; Mirts, E; Reed, J; Petrik, I D; Lu, Y

    2016-01-01

    Heteronuclear metalloenzymes catalyze some of the most fundamentally interesting and practically useful reactions in nature. However, the presence of two or more metal ions in close proximity in these enzymes makes them more difficult to prepare and study than homonuclear metalloenzymes. To meet these challenges, heteronuclear metal centers have been designed into small and stable proteins with rigid scaffolds to understand how these heteronuclear centers are constructed and the mechanism of their function. This chapter describes methods for designing heterobinuclear metal centers in a protein scaffold by giving specific examples of a few heme-nonheme bimetallic centers engineered in myoglobin and cytochrome c peroxidase. We provide step-by-step procedures on how to choose the protein scaffold, design a heterobinuclear metal center in the protein scaffold computationally, incorporate metal ions into the protein, and characterize the resulting metalloproteins, both structurally and functionally. Finally, we discuss how an initial design can be further improved by rationally tuning its secondary coordination sphere, electron/proton transfer rates, and the substrate affinity. PMID:27586347

  6. Synthesis, X-ray crystallography, spectroscopic (FT-IR, 1H &13C NMR and UV), computational (DFT/B3LYP) and enzymes inhibitory studies of 7-hydroximinocholest-5-en-3-ol acetate

    NASA Astrophysics Data System (ADS)

    Ahmad, Faheem; Parveen, Mehtab; Alam, Mahboob; Azaz, Shaista; Malla, Ali Mohammed; Alam, Mohammad Jane; Lee, Dong-Ung; Ahmad, Shabbir

    2016-07-01

    The present study reports the synthesis of 7-Hydroximinocholest-5-en-3-ol acetate (syn. 3β-acetoxycholest-5-en-7-one oxime; in general, steroidal oxime). The identity of steroidal molecule was confirmed by NMR, FT-IR, MS, CHN microanalysis and X-ray crystallography. DFT calculations on the titled molecule have been performed. The molecular structure and spectra interpreted by Gaussian hybrid computational analysis theory (B3LYP) are found to be in good correlation with the experimental data obtained from the various spectrophotometric techniques. The vibrational bands appearing in the FTIR are assigned with great accuracy using harmonic frequencies along with intensities and animated modes. Molecular properties like HOMO-LUMO analysis, chemical reactivity descriptors, MEP mapping, dipole moment and natural atomic charges have been presented at the same level of theory. Moreover, the Hirshfeld analysis was carried out to ascertain the secondary interactions and associated 2D fingerprint plots. The percentages of various interactions are pictorialized by fingerprint plots of Hirshfeld surface. Steroidal oxime exhibited promising inhibitory activity against acetylcholinesterase (AChE) as compared to the reference drug, tacrine. Molecular docking was performed to introduce steroidal molecules into the X-ray crystal structures of acetylcholinesterase at the active site to find out the probable binding mode. The results of molecular docking admitted that steroidal oxime may exhibit enzyme inhibitor activity.

  7. Comprehensive quantum chemical and spectroscopic (FTIR, FT-Raman, 1H, 13C NMR) investigations of O-desmethyltramadol hydrochloride an active metabolite in tramadol--an analgesic drug.

    PubMed

    Arjunan, V; Santhanam, R; Marchewka, M K; Mohan, S

    2014-03-25

    O-desmethyltramadol is one of the main metabolites of tramadol widely used clinically and has analgesic activity. The FTIR and FT-Raman spectra of O-desmethyl tramadol hydrochloride are recorded in the solid phase in the regions 4000-400 cm(-1) and 4000-100 cm(-1), respectively. The observed fundamentals are assigned to different normal modes of vibration. Theoretical studies have been performed as its hydrochloride salt. The structure of the compound has been optimised with B3LYP method using 6-31G(**) and cc-pVDZ basis sets. The optimised bond length and bond angles are correlated with the X-ray data. The experimental wavenumbers were compared with the scaled vibrational frequencies determined by DFT methods. The IR and Raman intensities are determined with B3LYP method using cc-pVDZ and 6-31G(d,p) basic sets. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/cc-pVDZ method to display electrostatic potential (electron+nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of O-desmethyltramadol hydrochloride has been performed to indicate the presence of intramolecular charge transfer. The (1)H and (13)C NMR chemical shifts of the molecule have been anlysed. PMID:24316546

  8. Tautomeric states of the active-site histidines of phosphorylated and unphosphorylated IIIGlc, a signal-transducing protein from Escherichia coli, using two-dimensional heteronuclear NMR techniques.

    PubMed Central

    Pelton, J. G.; Torchia, D. A.; Meadow, N. D.; Roseman, S.

    1993-01-01

    IIIGlc is an 18.1-kDa signal-transducing phosphocarrier protein of the phosphoenolpyruvate:glycose phosphotransferase system from Escherichia coli. The 1H, 15N, and 13C histidine ring NMR signals of both the phosphorylated and unphosphorylated forms of IIIGlc have been assigned using two-dimensional 1H-15N and 1H-13C heteronuclear multiple-quantum coherence (HMQC) experiments and a two-dimensional 13C-13C-1H correlation spectroscopy via JCC coupling experiment. The data were acquired on uniformly 15N-labeled and uniformly 15N/13C-labeled protein samples. The experiments rely on one-bond and two-bond J couplings that allowed for assignment of the signals without the need for the analysis of through-space (nuclear Overhauser effect spectroscopy) correlations. The 15N and 13C chemical shifts were used to determine that His-75 exists predominantly in the N epsilon 2-H tautomeric state in both the phosphorylated and unphosphorylated forms of IIIGlc, and that His-90 exists primarily in the N delta 1-H state in the unphosphorylated protein. Upon phosphorylation of the N epsilon 2 nitrogen of His-90, the N delta 1 nitrogen remains protonated, resulting in the formation of a charged phospho-His-90 moiety. The 1H, 15N, and 13C signals of the phosphorylated and unphosphorylated proteins showed only minor shifts in the pH range from 6.0 to 9.0. These data indicate that the pK alpha values for both His-75 and His-90 in IIIGlc and His-75 in phospho-IIIGlc are less than 5.0, and that the pK alpha value for phospho-His-90 is greater than 10. The results are presented in relation to previously obtained structural data on IIIGlc, and implications for proposed mechanisms of phosphoryl transfer are discussed. PMID:8518729

  9. Experimental and quantum-chemical studies of 1H, 13C and 15N NMR coordination shifts in Pd(II) and Pt(II) chloride complexes with methyl and phenyl derivatives of 2,2'-bipyridine and 1,10-phenanthroline.

    PubMed

    Pazderski, Leszek; Tousek, Jaromír; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2007-12-01

    1H, 13C and 15N NMR studies of platinide(II) (M=Pd, Pt) chloride complexes with methyl and phenyl derivatives of 2,2'-bipyridine and 1,10-phenanthroline [LL=4,4'-dimethyl-2,2'-bipyridine (dmbpy); 4,4'-diphenyl-2,2'-bipyridine (dpbpy); 4,7-dimethyl-1,10-phenanthroline (dmphen); 4,7-diphenyl-1,10-phenanthroline (dpphen)] having a general [M(LL)Cl2] formula were performed and the respective chemical shifts (delta1H, delta13C, delta15N) reported. 1H high-frequency coordination shifts (Delta1Hcoord=delta1Hcomplex-delta1Hligand) were discussed in relation to the changes of diamagnetic contribution in the relevant 1H shielding constants. The comparison to literature data for similar [M(LL)(XX)], [M(LL)X2] and [M(LL)XY] coordination or organometallic compounds containing various auxiliary ligands revealed a large dependence of delta1H parameters on inductive and anisotropic effects. 15N low-frequency coordination shifts (Delta15Ncoord=delta 15Ncomplex-delta15Nligand) of ca 88-96 ppm for M=Pd and ca 103-111 ppm for M=Pt were attributed to both the decrease of the absolute value of paramagnetic contribution and the increase of the diamagnetic term in the expression for 15N shielding constants. The absolute magnitude of Delta15Ncoord parameter increased by ca 15 ppm upon Pd(II)-->Pt(II) transition and by ca 6-7 ppm following dmbpy-->dmphen or dpbpy-->dpphen ligand replacement; variations between analogous complexes containing methyl and phenyl ligands (dmbpy vs dpbpy; dmphen vs dpphen) did not exceed+/-1.5 ppm. Experimental 1H, 13C, 15N NMR chemical shifts were compared to those quantum-chemically calculated by B3LYP/LanL2DZ+6-31G**//B3LYP/LanL2DZ+6-31G*, both in vacuo and in DMSO or DMF solution. PMID:18044804

  10. Heteronuclear decoupling by optimal tracking.

    PubMed

    Neves, Jorge L; Heitmann, Björn; Khaneja, Navin; Glaser, Steffen J

    2009-11-01

    The problem to design efficient heteronuclear decoupling sequences is studied using optimal control methods. A generalized version of the gradient ascent engineering (GRAPE) algorithm is presented that makes it possible to design complex non-periodic decoupling sequences which are characterized by tens of thousands of pulse sequence parameters. In contrast to conventional approaches based on average Hamiltonian theory, the concept of optimal tracking is used: a pulse sequence is designed that steers the evolution of an ensemble of spin systems such that at a series of time points, a specified trajectory of the density operator is tracked as closely as possible. The approach is demonstrated for the case of low-power heteronuclear decoupling in the liquid state for in vivo applications. Compared to conventional sequences, significant gains in decoupling efficiency and robustness with respect to offset and inhomogeneity of the radio-frequency field were found in simulations and experiments. PMID:19695913

  11. A General Assignment Method for Oriented Sample (OS) Solid-state NMR of Proteins Based on The Correlation of Resonances through Heteronuclear Dipolar Couplings in Samples Aligned Parallel and Perpendicular to the Magnetic Field

    PubMed Central

    Lu, George J.; Son, Woo Sung; Opella, Stanley J.

    2011-01-01

    A general method for assigning oriented sample (OS) solid-state NMR spectra of proteins is demonstrated. In principle, this method requires only a single sample of a uniformly 15N-labeled membrane protein in magnetically aligned bilayers, and a previously assigned isotropic chemical shift spectrum obtained either from solution NMR on micelle or isotropic bicelle samples or from magic angle spinning (MAS) solid-state NMR on unoriented proteoliposomes. The sequential isotropic resonance assignments are transferred to the OS solid-state NMR spectra of aligned samples by correlating signals from the same residue observed in protein-containing bilayers aligned with their normals parallel and perpendicular to the magnetic field. The underlying principle is that the resonances from the same residue have heteronuclear dipolar couplings that differ by exactly a factor of two between parallel and perpendicular alignments. The method is demonstrated on the membrane-bound form of Pf1 coat protein in phospholipid bilayers, whose assignments have been previously made using an earlier generation of methods that relied on the preparation of many selectively labeled (by residue type) samples. The new method provides the correct resonance assignments using only a single uniformly 15N-labeled sample, two solid-state NMR spectra, and a previously assigned isotropic spectrum. Significantly, this approach is equally applicable to residues in alpha helices, beta sheets, loops, and any other elements of tertiary structure. Moreover, the strategy bridges between OS solid-state NMR of aligned samples and solution NMR or MAS solid-state NMR of unoriented samples. In combination with the development of complementary experimental methods, it provides a step towards unifying these apparently different NMR approaches. PMID:21316275

  12. Enantiodiscrimination and extraction of short and long range homo- and hetero-nuclear residual dipolar couplings by a spin selective correlation experiment

    NASA Astrophysics Data System (ADS)

    Nath, Nilamoni; Suryaprakash, N.

    2010-08-01

    A two dimensional correlation experiment for the measurement of short and long range homo- and hetero- nuclear residual dipolar couplings (RDCs) from the broad and featureless proton NMR spectra including 13C satellites is proposed. The method employs a single natural abundant 13C spin as a spy nucleus to probe all the coupled protons and permits the determination of RDCs of negligible strengths. The technique has been demonstrated for the study of organic chiral molecules aligned in chiral liquid crystal, where additional challenge is to unravel the overlapped spectrum of enantiomers. The significant advantage of the method is demonstrated in better chiral discrimination using homonuclear RDCs as additional parameters.

  13. Amplitudes of protein backbone dynamics and correlated motions in a small alpha/beta protein: correspondence of dipolar coupling and heteronuclear relaxation measurements.

    PubMed

    Clore, G Marius; Schwieters, Charles D

    2004-08-24

    Backbone residual dipolar coupling (N-H, Calpha-Halpha, N-C', and Calpha-C') data collected in five different media on the B3 IgG binding domain of streptococcal protein G (GB3) have been analyzed by simultaneous refinement of the coordinates and optimization of the magnitudes and orientations of the alignment tensors using single and multiple structure representations. We show, using appropriate error analysis, that agreement between observed and calculated dipolar couplings at the level of experimental uncertainty is obtained with a two-structure (N(e) = 2) ensemble representation which represents the simplest equilibrium description of anisotropic motions. The data permit one to determine the magnitude of the anisotropic motions along the four different backbone bond vectors in terms of order parameters. The order parameters, , for the N-H bond vectors are in qualitative agreement with the generalized order parameters, S(2)NH(relaxation), derived from (15)N relaxation measurements, with a correlation coefficient of 0.84. S(2)NH(relaxation) can be regarded as the product of an anisotropic order parameter, corresponding to derived from the residual dipolar couplings, and an axially symmetric order parameter, S(2)NH(axial), corresponding to bond librations which are expected to be essentially uniform along the polypeptide chain. The current data indicate that the average value of S(2)NH(axial) is approximately 0.9. The close correspondence of and S(2)NH(relaxation) indicates that any large-scale displacements from the mean coordinate positions on time scales longer than the rotational correlation time are rare and hence do not perturb the observed dipolar couplings. Analysis of a set of 100 N(e) = 2 ensembles reveals the presence of some long-range correlated motions of N-H and Calpha-Halpha vectors involving residues far apart in the sequence but close together in space. In addition, direct evidence is

  14. Conditional rotations of heteronuclear coupled spins.

    PubMed

    O'Donnell, Lauren F; Ridge, Clark D; Walls, Jamie D

    2015-01-01

    We present a new pulse sequence that conditionally excites I spin magnetization only in the presence of a nonzero heteronuclear coupling to an S spin. The pulse sequence, referred to as the reverse INEPT pathway selective pulse or RIPSP, generates a pure I spin rotation by an angle that depends upon the heteronuclear coupling constant in InS spin systems. Experimental demonstrations are shown in (13)C labeled chloroform, dichloromethane, and toluene samples and in unlabeled 2,3-dibromopropionic acid and brucine samples. PMID:25506815

  15. Conditional rotations of heteronuclear coupled spins

    NASA Astrophysics Data System (ADS)

    O'Donnell, Lauren F.; Ridge, Clark D.; Walls, Jamie D.

    2015-01-01

    We present a new pulse sequence that conditionally excites I spin magnetization only in the presence of a nonzero heteronuclear coupling to an S spin. The pulse sequence, referred to as the reverse INEPT pathway selective pulse or RIPSP, generates a pure I spin rotation by an angle that depends upon the heteronuclear coupling constant in In S spin systems. Experimental demonstrations are shown in 13C labeled chloroform, dichloromethane, and toluene samples and in unlabeled 2,3-dibromopropionic acid and brucine samples.

  16. Synthesis of 2,4,5,8-tetrabromotricyclo(4. 2. 2. 0/sup 1,5/)decane and determination of its structure by two-dimensional homonuclear and heteronuclear correlation /sup 1/H and /sup 13/C NMR spectroscopy and x-ray crystallographic analysis

    SciTech Connect

    Sekatsis, I.P.; Kemme, A.A.; Liepin'sh, E.E.; Bleidelis, Ya.Ya.; Gavars, M.P.; Raguel, B.P.; Polis, Ya.Yu.

    1988-08-10

    It is known that the bromination of endotricyclo(5.2.1.0/sup 2,6/)decane (I) with bromine in the presence of aluminum bromide leads to the formation of 1,3,5- and 1,3,6-tribromoadamantanes and 1,2,3,5,6,7-hexabromonaphthalene. In view of the complexity of the isomerization of the endo-decane (I) to adamantane the authors studied the bromination of (I) with bromine in order to detect the intermediate products of this isomerization. 2,4,5,8-Tetrabromotricyclo(4.2.2.0/sup 1,5/)decane was synthesized by the bromination of endo-tricyclo(5.2.1.0/sup 2,6/)decane, and its structure was determined by two-dimensional homonuclear and heteronuclear correlation NMR spectroscopy with full assignment of the signals and was confirmed by x-ray crystallographic analysis.

  17. Ultracold Collisions Involving Heteronuclear Alkali Metal Dimers

    SciTech Connect

    Cvitas, Marko T.; Soldan, Pavel; Hutson, Jeremy M.; Honvault, Pascal; Launay, Jean-Michel

    2005-05-27

    We carry out the first quantum dynamics calculations on ultracold atom-diatom collisions in isotopic mixtures. The systems studied are spin-polarized {sup 7}Li+{sup 6}Li{sup 7}Li, {sup 7}Li+{sup 6}Li{sub 2}, {sup 6}Li+{sup 6}Li{sup 7}Li, and {sup 6}Li+{sup 7}Li{sub 2}. Reactive scattering can occur for the first two systems even when the molecules are in their ground rovibrational states, but is slower than vibrational relaxation in homonuclear systems. Implications for sympathetic cooling of heteronuclear molecules are discussed.

  18. Heteronuclear Multidimensional Protein NMR in a Teaching Laboratory

    ERIC Educational Resources Information Center

    Wright, Nathan T.

    2016-01-01

    Heteronuclear multidimensional NMR techniques are commonly used to study protein structure, function, and dynamics, yet they are rarely taught at the undergraduate level. Here, we describe a senior undergraduate laboratory where students collect, process, and analyze heteronuclear multidimensional NMR experiments using an unstudied Ig domain (Ig2…

  19. An effective field theory analysis of Efimov features in heteronuclear mixture of ultracold atomic gases

    NASA Astrophysics Data System (ADS)

    Acharya, Bijaya; Ji, Chen; Platter, Lucas

    2016-05-01

    Recent experimental studies have unveiled Efimov physics in ultracold atomic gases of heteronuclear mixtures. The recombination features of such atomic systems display universal correlations including discrete scaling invariance. We use Effective Field Theory (EFT) to study the Efimov features of the heteronuclear three-atom systems consisting of two identical bosons which interact with each other through a natural scattering length and with the third particle through a large scattering length. We compute the corrections to the universal correlations by perturbative insertions of the interspecies effective range and the intraspecies scattering length. Such an analysis is relevant for mixtures of ultracold atomic gases near the interspecies Feshbach resonance. Supported by the US Department of Energy under Contract No. DE-AC05-00OR22725 and the National Science Foundation under Grant No. PHY-1516077.

  20. Nonnuclear Attractors in Heteronuclear Diatomic Systems.

    PubMed

    Terrabuio, Luiz Alberto; Teodoro, Tiago Quevedo; Matta, Chérif F; Haiduke, Roberto Luiz Andrade

    2016-03-01

    Nonnuclear attractors (NNAs) are observed in the electron density of a variety of systems, but the factors governing their appearance and their contribution to the system's properties remain a mystery. The NNA occurring in homo- and heteronuclear diatomics of main group elements with atomic numbers up to Z = 38 is investigated computationally (at the UCCSD/cc-pVQZ level of theory) by varying internuclear separations. This was done to determine the NNA occurrence window along with the evolution of the respective pseudoatomic basin properties. Two distinct categories of NNAs were detected in the data analyzed by means of catastrophe theory. Type "a" implies electronic charge transfer between atoms mediated by a pseudoatom. Type "b" shows an initial relocation of some electronic charge to a pseudoatom, which posteriorly returns to the same atom that donated this charge in the first place. A small difference of polarizability between the atoms that compose these heteronuclear diatomics seems to favor NNA formation. We also show that the NNA arising tends to result in some perceptible effects on molecular dipole and/or quadrupole moment curves against internuclear distance. Finally, successive cationic ionization results in the fast disappearance of the NNA in Li2 indicating that its formation is mainly governed by the field generated by the quantum mechanical electronic density and only depends parametrically on the bare nuclear field/potential at a given molecular geometry. PMID:26842391

  1. Heteronuclear decoupling by multiple rotating frame technique

    PubMed Central

    Arthanari, Haribabu; Wagner, Gerhard; Khaneja, Navin

    2011-01-01

    The paper describes the multiple rotating frame technique for designing modulated rf fields, that perform broadband heteronuclear decoupling in solution NMR spectroscopy. The decoupling method presented here is understood by performing a sequence of coordinate transformations, each of which demodulates a component of the rf field to a static component, that progressively averages the chemical shift and the dipolar interaction. We show that by increasing the number of modulations in the decoupling field, the ratio of dispersion in the chemical shift to the strength of the static component of the rf field is successively reduced in the progressive frames. The known decoupling methods like continuous wave decoupling, TPPM, etc., can be viewed as special cases of this method and their performance improves by adding additional modulations in the decoupling field. The technique is also expected to find use in design of broadband excitation, inversion and mixing sequences and broadband experiments in solid state NMR. PMID:21227724

  2. High-resolution heteronuclear multi-dimensional NMR spectroscopy in magnetic fields with unknown spatial variations

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiyong; Huang, Yuqing; Smith, Pieter E. S.; Wang, Kaiyu; Cai, Shuhui; Chen, Zhong

    2014-05-01

    Heteronuclear NMR spectroscopy is an extremely powerful tool for determining the structures of organic molecules and is of particular significance in the structural analysis of proteins. In order to leverage the method’s potential for structural investigations, obtaining high-resolution NMR spectra is essential and this is generally accomplished by using very homogeneous magnetic fields. However, there are several situations where magnetic field distortions and thus line broadening is unavoidable, for example, the samples under investigation may be inherently heterogeneous, and the magnet’s homogeneity may be poor. This line broadening can hinder resonance assignment or even render it impossible. We put forth a new class of pulse sequences for obtaining high-resolution heteronuclear spectra in magnetic fields with unknown spatial variations based on distant dipolar field modulations. This strategy’s capabilities are demonstrated with the acquisition of high-resolution 2D gHSQC and gHMBC spectra. These sequences’ performances are evaluated on the basis of their sensitivities and acquisition efficiencies. Moreover, we show that by encoding and decoding NMR observables spatially, as is done in ultrafast NMR, an extra dimension containing J-coupling information can be obtained without increasing the time necessary to acquire a heteronuclear correlation spectrum. Since the new sequences relax magnetic field homogeneity constraints imposed upon high-resolution NMR, they may be applied in portable NMR sensors and studies of heterogeneous chemical and biological materials.

  3. Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers

    SciTech Connect

    Fedorov, Dmitry A.; Varganov, Sergey A.; Derevianko, Andrei

    2014-05-14

    We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X{sup 1}Σ{sup +} electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm{sup −1} for LiNa and by no more than 114 cm{sup −1} for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm{sup −1}, and the discrepancies for the anharmonic correction are less than 0.1 cm{sup −1}. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.

  4. Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers

    NASA Astrophysics Data System (ADS)

    Fedorov, Dmitry A.; Derevianko, Andrei; Varganov, Sergey A.

    2014-05-01

    We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X1Σ+ electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm-1 for LiNa and by no more than 114 cm-1 for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm-1, and the discrepancies for the anharmonic correction are less than 0.1 cm-1. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.

  5. Complexation of oxygen ligands with dimeric rhodium(II) tetrakistrifluoroacetate in chloroform: 1H, 13C NMR and DFT studies

    NASA Astrophysics Data System (ADS)

    Głaszczka, Rafał; Jaźwiński, Jarosław

    2013-03-01

    The complexation of dimeric rhodium(II) tetrakistrifluoroacetylate with 25 ligands containing oxygen atoms: alcohols, ethers, ketones, aldehydes, carboxylic acids and esters in chloroform solution have been investigated by 1H and 13C NMR spectroscopy and Density Functional Theory (DFT) methods. Investigated ligands form 1:1 adducts in our experimental conditions, with stability constants in the order of several hundred mol-1. The exchange of ligands in solution is fast on the NMR spectroscopic timescale. The decrease of longitudinal relaxation times T1 in ligands in the presence of rhodium salt has been tested as the means of determination of the complexation site in ligands. The influence of complexation on chemical shifts in ligands was evaluated by a parameter complexation shift Δδ (Δδ = δadd - δlig). These parameters were positive (>0 ppm) and did not exceed 1 ppm for 1H NMR; and varied from ca. -5 to +15 ppm in the case of 13C NMR. The calculation by DFT methods using the B3LYP functional (structure optimization, electronic energy) and B3PW91 functional (shielding), and combinations of the (6-31G(2d), 6-311G++(2d,p), and LANL2DZ basis sets, followed by scaling procedures reproduced satisfactorily 1H and 13C chemical shifts and, with some limitations, allowed to estimate Δδ parameters.

  6. 1H, 13C, and 15N backbone and side chain resonance assignments of thermophilic Geobacillus kaustophilus cyclophilin-A

    SciTech Connect

    Holliday, Michael; Zhang, Fengli; Isern, Nancy G.; Armstrong, Geoffrey S.; Eisenmesser, Elan Z.

    2014-04-01

    Cyclophilins catalyze the reversible peptidyl-prolyl isomerization of their substrates and are present across all kingdoms of life from humans to bacteria. Although numerous biological roles have now been discovered for cyclophilins, their function was initially ascribed to their chaperone-like activity in protein folding where they catalyze the often rate-limiting step of proline isomerization. This chaperone-like activity may be especially important under extreme conditions where cyclophilins are often over expressed, such as in tumors for human cyclophilins {Lee, 2010 #1167}, but also in organisms that thrive under extreme conditions, such as theromophilic bacteria. Moreover, the reversible nature of the peptidyl-prolyl isomerization reaction catalyzed by cyclophilins has allowed these enzymes to serve as model systems for probing the role of conformational changes during catalytic turnover {Eisenmesser, 2002 #20;Eisenmesser, 2005 #203}. Thus, we present here the resonance assignments of a thermophilic cyclophilin from Geobacillus kaustophilus derived from deep-sea sediment {Takami, 2004 #1384}. This thermophilic cyclophilin may now be studied at a variety of temperatures to provide insight into the comparative structure, dynamics, and catalytic mechanism of cyclophilins.

  7. 1H, 13C MAS NMR and GIAO-CPHF calculations of chloramphenicol, thiamphenicol and their pyrrole analogues

    NASA Astrophysics Data System (ADS)

    Żołek, Teresa; Paradowska, Katarzyna; Krajewska, Dorota; Różański, Andrzej; Wawer, Iwona

    2003-02-01

    The 13C CP MAS and 1H MAS NMR and ab initio (GIAO-CPHF) calculations were used to obtain structural information on two known antibiotics: chloramphenicol, and thiamphenicol, and two new analogues: DL- threo-1-(1-methyl-4-nitro-pyrrole-2-yl)-2-dichloroacetamidopropane-1,3-diol and DL- threo-1-(1-methylsulfonylpyrrole-3-yl)-2-dichloroacetamidopropane-1,3-diol.

  8. Precise and rapid isotopomic analysis by (1)H-(13)C 2D NMR: Application to triacylglycerol matrices.

    PubMed

    Merchak, Noelle; Silvestre, Virginie; Rouger, Laetitia; Giraudeau, Patrick; Rizk, Toufic; Bejjani, Joseph; Akoka, Serge

    2016-08-15

    An optimized HSQC sequence was tested and applied to triacylglycerol matrices to determine their isotopic and metabolomic profiles. Spectral aliasing and non-uniform sampling approaches were used to decrease the experimental time and to improve the resolution, respectively. An excellent long-term repeatability of signal integrals was achieved enabling to perform isotopic measurements. Thirty-two commercial vegetable oils were analyzed by this methodology. The results show that this method can be used to classify oil samples according to their geographical and botanical origins. PMID:27260459

  9. (1)H, (13)C and (15)N resonance assignment of the cytosolic dithiol glutaredoxin 1 from the pathogen Trypanosoma brucei.

    PubMed

    Stefani, Monica; Sturlese, Mattia; Manta, Bruno; Löhr, Frank; Mammi, Stefano; Comini, Marcelo; Bellanda, Massimo

    2016-04-01

    Trypanosomatids are parasites responsible for several tropical and subtropical diseases, such as Chaga's disease, sleeping sickness and Leishmaniasis. In contrast to the mammalian host, the thiol-redox metabolism of these pathogens depends on trypanothione [bis-glutathionylspermidine, T(SH)2] instead of glutathione (GSH) providing a set of lineage-specific proteins as drug target candidates. Glutaredoxins (Grx) are ubiquitous small thiol-disulfide oxidoreductases that belong to the thioredoxin-fold family. They play a central role in redox homeostasis and iron sulfur-cluster biogenesis. Each species, including trypanosomes, possesses its own set of isoforms distributed in different subcellular compartments. The genome of trypanosomatids encodes for two class I (dithiolic) Grxs named 2-C-Grx1 and 2-C-Grx2. Both proteins were shown to efficiently reduce different disulfides at the expenses of T(SH)2 using a mechanism that involves the two cysteines in the active site. Moreover, the cytosolic Trypanosoma brucei 2-C-Grx1 but not the mitochondrial 2-C-Grx2 was able to coordinate an iron-sulfur cluster with T(SH)2 or GSH as ligand. As a first step to unravel the structural basis for the specificity observed in the trypanosomal glutaredoxins, we present here the NMR resonance assignment of 2-C-Grx1 from the parasite T. brucei brucei. PMID:26386962

  10. Symbiotic solitons in heteronuclear multicomponent Bose-Einstein condensates

    SciTech Connect

    Perez-Garcia, Victor M.; Beitia, Juan Belmonte

    2005-09-15

    We show that bright solitons exist in quasi-one-dimensional heteronuclear multicomponent Bose-Einstein condensates with repulsive self-interaction and attractive interspecies interaction. They are remarkably robust to perturbations of initial data and collisions and can be generated by the mechanism of modulational instability. Some possibilities for control and the behavior of the system in fully three-dimensional scenarios are also discussed.

  11. Heteronuclear DNP of protons and deuterons with TEMPOL.

    PubMed

    Kaminker, I; Shimon, D; Hovav, Y; Feintuch, A; Vega, S

    2016-04-28

    Dynamic nuclear polarization (DNP) experiments on samples with several types of magnetic nuclei sometimes exhibit "cross-talk" between the nuclei, such as different nuclei having DNP spectra with similar shapes and enhancements. In this work we demonstrate that while at 20 K the DNP spectra of (1)H and (2)H nuclei, in a sample composed of 50% v/v (1)H2O/DMSO-d6 and containing 40 mM TEMPOL, are different and can be analyzed using the indirect cross effect (iCE) model, at 6 K the DNP spectra of both (1)H and (2)H nuclei become identical. In addition we experimentally demonstrate that there exists an efficient polarization exchange between the two nuclear pools at this temperature. Both of these results are hallmark predictions of the thermal mixing (TM) formalism. However, the origin of these observations cannot, in our case, be explained using the standard TM formalism, as in our sample the electron reservoir cannot be described by a single non-Zeeman spin temperature, which is a prerequisite of TM. This conclusion follows from the analysis of the electron electron double resonance (ELDOR) experiments on our sample and is similar to the previously published results. Consequently, another mechanism must be used in order to explain these "cross-talk" effects. The heteronuclear cross effect (hnCE) DNP mechanism, previously introduced based on the simulations of the spin evolution in small model systems, results in "cross-talk" effects between two types of nuclei that are similar to the experimental ones seen in this work. In particular we show that the hnCE mechanism exhibits polarization transfer between the nuclei and that there exists a clear relationship between the steady state polarizations of the two types of nuclei which may, in the future, be correlated with the phenomenon observed in the two types of bulk nuclear signals in samples during DNP experiments. It is suggested that the hnCE electrons are a possible source for the process that equalizes the bulk

  12. Heteronuclear Micro-Helmholtz Coil Facilitates µm-Range Spatial and Sub-Hz Spectral Resolution NMR of nL-Volume Samples on Customisable Microfluidic Chips

    PubMed Central

    Spengler, Nils; Höfflin, Jens; Moazenzadeh, Ali; Mager, Dario; MacKinnon, Neil; Badilita, Vlad; Wallrabe, Ulrike; Korvink, Jan G.

    2016-01-01

    We present a completely revised generation of a modular micro-NMR detector, featuring an active sample volume of ∼ 100 nL, and an improvement of 87% in probe efficiency. The detector is capable of rapidly screening different samples using exchangeable, application-specific, MEMS-fabricated, microfluidic sample containers. In contrast to our previous design, the sample holder chips can be simply sealed with adhesive tape, with excellent adhesion due to the smooth surfaces surrounding the fluidic ports, and so withstand pressures of ∼2.5 bar, while simultaneously enabling high spectral resolution up to 0.62 Hz for H2O, due to its optimised geometry. We have additionally reworked the coil design and fabrication processes, replacing liquid photoresists by dry film stock, whose final thickness does not depend on accurate volume dispensing or precise levelling during curing. We further introduced mechanical alignment structures to avoid time-intensive optical alignment of the chip stacks during assembly, while we exchanged the laser-cut, PMMA spacers by diced glass spacers, which are not susceptible to melting during cutting. Doing so led to an overall simplification of the entire fabrication chain, while simultaneously increasing the yield, due to an improved uniformity of thickness of the individual layers, and in addition, due to more accurate vertical positioning of the wirebonded coils, now delimited by a post base plateau. We demonstrate the capability of the design by acquiring a 1H spectrum of ∼ 11 nmol sucrose dissolved in D2O, where we achieved a linewidth of 1.25 Hz for the TSP reference peak. Chemical shift imaging experiments were further recorded from voxel volumes of only ∼ 1.5nL, which corresponded to amounts of just 1.5 nmol per voxel for a 1 M concentration. To extend the micro-detector to other nuclei of interest, we have implemented a trap circuit, enabling heteronuclear spectroscopy, demonstrated by two 1H/13C 2D HSQC experiments. PMID

  13. Heteronuclear Micro-Helmholtz Coil Facilitates µm-Range Spatial and Sub-Hz Spectral Resolution NMR of nL-Volume Samples on Customisable Microfluidic Chips.

    PubMed

    Spengler, Nils; Höfflin, Jens; Moazenzadeh, Ali; Mager, Dario; MacKinnon, Neil; Badilita, Vlad; Wallrabe, Ulrike; Korvink, Jan G

    2016-01-01

    We present a completely revised generation of a modular micro-NMR detector, featuring an active sample volume of ∼ 100 nL, and an improvement of 87% in probe efficiency. The detector is capable of rapidly screening different samples using exchangeable, application-specific, MEMS-fabricated, microfluidic sample containers. In contrast to our previous design, the sample holder chips can be simply sealed with adhesive tape, with excellent adhesion due to the smooth surfaces surrounding the fluidic ports, and so withstand pressures of ∼2.5 bar, while simultaneously enabling high spectral resolution up to 0.62 Hz for H2O, due to its optimised geometry. We have additionally reworked the coil design and fabrication processes, replacing liquid photoresists by dry film stock, whose final thickness does not depend on accurate volume dispensing or precise levelling during curing. We further introduced mechanical alignment structures to avoid time-intensive optical alignment of the chip stacks during assembly, while we exchanged the laser-cut, PMMA spacers by diced glass spacers, which are not susceptible to melting during cutting. Doing so led to an overall simplification of the entire fabrication chain, while simultaneously increasing the yield, due to an improved uniformity of thickness of the individual layers, and in addition, due to more accurate vertical positioning of the wirebonded coils, now delimited by a post base plateau. We demonstrate the capability of the design by acquiring a 1H spectrum of ∼ 11 nmol sucrose dissolved in D2O, where we achieved a linewidth of 1.25 Hz for the TSP reference peak. Chemical shift imaging experiments were further recorded from voxel volumes of only ∼ 1.5 nL, which corresponded to amounts of just 1.5 nmol per voxel for a 1 M concentration. To extend the micro-detector to other nuclei of interest, we have implemented a trap circuit, enabling heteronuclear spectroscopy, demonstrated by two 1H/13C 2D HSQC experiments. PMID

  14. Rapid screening for structural integrity of expressed proteins by heteronuclear NMR spectroscopy.

    PubMed Central

    Gronenborn, A. M.; Clore, G. M.

    1996-01-01

    A simple and rapid method based on 15N labeling and 1H-15N heteronuclear single quantum coherence spectroscopy is presented to directly assess the structural integrity of overexpressed proteins in crude Escherichia coli extracts without the need for any purification. The method is demonstrated using two different expression systems and two different proteins, the B1 immunoglobulin-binding domain of streptococcal protein G (56 residues) and human interleukin-1 beta (153 residues). It is shown that high quality 1H-15N correlation spectra, recorded in as little as 15 min and displaying only cross-peaks arising from the overexpressed protein of interest, can be obtained from crude E. coli extracts. PMID:8771212

  15. Strong-field ionization of a heteronuclear diatomic molecule

    SciTech Connect

    Ren, Xianghe; Nakajima, Takashi

    2010-12-15

    We theoretically study strong-field ionization of a heteronuclear diatomic molecule, CO, by calculating the photoelectron angular distributions (PADs) and the total ionization rates using linearly and circularly polarized laser fields. We find that, although the PADs of CO generally do not have inversion symmetry, they become more inversion symmetric as the photoelectron energy increases. Heteronuclear features of CO upon ionization are better understood by comparing the results with those of a representative of homonuclear molecules, N{sub 2}, in that, although there are some similarities between CO and N{sub 2} due to the same orbital symmetry, {sigma}{sub g}, there are some differences between them in terms of the ionization suppression and orientation dependence of the total ionization yield. Namely, CO behaves more like an atom in the low-intensity range in a sense that ionization takes place mainly from the neighborhood of the C core, while it behaves more like a double-core molecule in the high-intensity range since ionization takes place from the neighborhood of both C and O cores. This explains why ionization suppression of CO is not seen at the low intensity but it becomes more visible at the high intensity range.

  16. Highly Repeatable Dissolution Dynamic Nuclear Polarization for Heteronuclear NMR Metabolomics.

    PubMed

    Bornet, Aurélien; Maucourt, Mickaël; Deborde, Catherine; Jacob, Daniel; Milani, Jonas; Vuichoud, Basile; Ji, Xiao; Dumez, Jean-Nicolas; Moing, Annick; Bodenhausen, Geoffrey; Jannin, Sami; Giraudeau, Patrick

    2016-06-21

    At natural (13)C abundance, metabolomics based on heteronuclear NMR is limited by sensitivity. We have recently demonstrated how hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) assisted by cross-polarization (CP) provides a reliable way of enhancing the sensitivity of heteronuclear NMR in dilute mixtures of metabolites. In this Technical Note, we evaluate the precision of this experimental approach, a critical point for applications to metabolomics. The higher the repeatability, the greater the likelihood that one can detect small biologically relevant differences between samples. The average repeatability of our state-of-the-art D-DNP NMR equipment for samples of metabolomic relevance (20 mg dry weight tomato extracts) is 3.6% for signals above the limit of quantification (LOQ) and 6.4% when all the signals above the limit of detection (LOD) are taken into account. This first report on the repeatability of D-DNP highlights the compatibility of the technique with the requirements of metabolomics and confirms its potential as an analytical tool for such applications. PMID:27253320

  17. Application of heteronuclear couplings to conformational analysis of oligonucleotides

    SciTech Connect

    Zhu, G.; Live, D.; Bax, A.

    1994-12-01

    The value of vicinal coupling constants extracted from NMR spectra in deducing torsion angles for conformational analysis is well recognized. Due to the abundance of protons, their couplings have been mostly widely used. In many instances, couplings between protons and other nuclei may be a valuable complement to proton-proton couplings or, in some instances, may be the only coupling available to characterize the torsion angle about a bond. Recently, heteronuclear couplings have been used to great benefit in studies of isotopically enriched proteins, and this general approach has been extended to peptides at natural abundance. The possibility of using this approach to study oligonucleotides is also attractive but has not as yet been widely exploited. With the development of strategies for labeling such molecules, particularly RNAs, this may become an important component in conformational analysis. For DNA, labeling is less accessible, but sufficient quantities of unlabeled material are readily available for measuring these couplings at natural abundance. We chose several DNA systems to explore the usefulness of heteronuclear couplings in addressing the sugar conformation and the glycosidic torsion angle. Intensities of cross peaks in long-range HMQC experiments can be related to the couplings. Crosspeaks involving H1{prime} and C1{prime} atoms have been emphasized because of the superior shift dispersion at these positions between sugar protons and carbon atoms. Results will be shown for the self-complementary Dickerson duplex dodecamer sequence d(CGCGAATTCGCG) and for d(GGTCGG), which dimerizes to form a G-tetrad structure incorporating both syn and anti base orientations. The couplings provide a clear discrimination between presence of C3{prime}-endo and C2{prime}-endo conformations of the sugars and syn and anti bases arrangements.

  18. Characterization and quantification of microstructures of a fluorinated terpolymer by both homonuclear and heteronuclear two-dimensional NMR spectroscopy.

    PubMed

    Ok, Salim

    2015-02-01

    Fluoropolymers are usually insoluble in organic solvents. Insolubility of fluoropolymers limits basic characterization such as microstructural investigations. In the family of fluoropolymers, terpolymer of tetrafluorethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (VDF), named THV is one of the newest members. There are nine grades of THV available. Among the nine grades, THV-221 G is an ideal model polymer for basic characterization purposes. THV-221 G is soluble in solvents such as acetone and ethyl acetate. In the current report, both homonuclear and heteronuclear 2D NMR experiments were employed in solution on THV-221 G. The homonuclear gradient correlation spectroscopy NMR measurement revealed that THV has two adjacent TFE units in addition to TFE-HFP sequence orders. The fraction of the microstructures is quantified by the analysis of 1D solution (19)F NMR spectrum. Further, the gradient heteronuclear single quantum coherence experiment helped with the clarification of chemical environments of the units TFE, HFP, and VDF. The 1D solution (13)C NMR spectrum was helpful in clarifying sequence assignments of VDF. It is concluded that THV is a random polymer with a limited fraction of TFE-TFE and TFE-HFP sequence orders in addition to head-to-tail polymerization of VDF unit. PMID:25327292

  19. Determination of unresolved heteronuclear scalar coupling constants by J(up)-HSQMBC

    NASA Astrophysics Data System (ADS)

    Glanzer, Simon; Kunert, Olaf; Zangger, Klaus

    2016-07-01

    Long-range heteronuclear scalar coupling constants provide important structural information, which is necessary for obtaining stereospecific assignment or dihedral angle information. The measurement of small proton-carbon splittings is particularly difficult due to the low natural abundance of carbon-13 and the presence of homonuclear couplings of similar size. Here we present a real-time J-upscaled HSQMBC, which allows the measurement of heteronuclear coupling constants even if they are hidden in the signal linewidth of a regular spectrum.

  20. Simulating spin dynamics in organic solids under heteronuclear decoupling.

    PubMed

    Frantsuzov, Ilya; Ernst, Matthias; Brown, Steven P; Hodgkinson, Paul

    2015-09-01

    Although considerable progress has been made in simulating the dynamics of multiple coupled nuclear spins, predicting the evolution of nuclear magnetisation in the presence of radio-frequency decoupling remains challenging. We use exact numerical simulations of the spin dynamics under simultaneous magic-angle spinning and RF decoupling to determine the extent to which numerical simulations can be used to predict the experimental performance of heteronuclear decoupling for the CW, TPPM and XiX sequences, using the methylene group of glycine as a model system. The signal decay times are shown to be strongly dependent on the largest spin order simulated. Unexpectedly large differences are observed between the dynamics with and without spin echoes. Qualitative trends are well reproduced by modestly sized spin system simulations, and the effects of finite spin-system size can, in favourable cases, be mitigated by extrapolation. Quantitative prediction of the behaviour in complex parameter spaces is found, however, to be very challenging, suggesting that there are significant limits to the role of numerical simulations in RF decoupling problems, even when specialist techniques, such as state-space restriction, are used. PMID:26073419

  1. Two dimensional heteronuclear complexes with cyanide and 4-aminomethylpyridine ligands

    NASA Astrophysics Data System (ADS)

    Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla; Yeşilel, Okan Zafer; MuratTaş

    2014-09-01

    Two new cyano-bridged two-dimensional heteronuclear complexes, [Cd(NH3)2(μ-ampy)Ni(μ-CN)2(CN)2]n (1) and [Cd(H2O)2(μ-ampy)Pt(μ-CN)2(CN)2]n (2) (ampy = 4-aminomethylpyridine), were synthesized and characterized by FT-IR and Raman spectroscopic, thermal (TG, DTG and DTA) and elemental analyses and single crystal X-ray diffraction techniques. They crystallize in the triclinic system and P-1 space group. The Ni(II) or Pt(II) ions are four coordinate with four cyanide-carbon atoms in a square planar geometry and the Cd(II) ion exhibits a distorted octahedral coordination by two different N-atoms from two symmetrically equivalent ampy ligands, two ammine or aqua ligands and two bridging cyano groups.The most important features of the complexes are the presence of obvious M⋯π (M = Ni(II) or Pt(II)) interactions.

  2. Bruker AMX Y Channel Heteronuclear Decoupling Using a Linear Amplifier

    SciTech Connect

    Alam, Todd M.; Lang, David P.

    1999-08-02

    Under both static and common MAS conditions (< 15 kHz) the question of residual X-Y heteronuclear decoupling can become a complicating factor in the analysis of various NMR results. In our lab the impact of {sup 31}P-{sup 23}Na dipolar coupling on the observed {sup 23}Na M{sub 2} relaxation for a series of sodium phosphate glasses was recently investigated by employing continuous wave {sup 31}P decoupling during the entire pulse sequence. Initially these efforts were complicate by the inability to provide a gating pulse during the data acquisition using the standard Bruker nomenclature, go=2, for the acquisition loop. A pulse sequence to overcome these restrictions is given below. Our AMX400 instrument is configured with a 3 channel MCI, but utilizes a linear AMT amplifier on the 3rd channel (requiring gating pulse via the C4 program call during the entire time it is on). The standard acquisition loop has been replaced by direct adc and aq commands for data acquisition. Unlike the go=2 statement which does not allow a C4 gating command to be included, these individual acquisition commands can all include distinct C4 gating.

  3. Mixed frequency/time domain optical analogues of heteronuclear multidimensional NMR.

    PubMed

    Pakoulev, Andrei V; Rickard, Mark A; Meyer, Kent A; Kornau, Kathryn; Mathew, Nathan A; Thompson, David E; Wright, John C

    2006-03-16

    Ultrafast spectroscopy is dominated by time domain methods such as pump-probe and, more recently, 2D-IR spectroscopies. In this paper, we demonstrate that a mixed frequency/time domain ultrafast four wave mixing (FWM) approach not only provides similar capabilities, but it also provides optical analogues of multiple- and zero-quantum heteronuclear nuclear magnetic resonance (NMR). The method requires phase coherence between the excitation pulses only over the dephasing time of the coherences. It uses twelve coherence pathways that include four with populations, four with zero-quantum coherences, and four with double-quantum coherences. Each pathway provides different capabilities. The population pathways correspond to those of two-dimensional (2D) time domain spectroscopies, while the double- and zero-quantum coherence pathways access the coherent dynamics of coupled quantum states. The three spectral and two temporal dimensions enable the isolation and characterization of the spectral correlations between different vibrational and/or electronic states, coherence and population relaxation rates, and coupling strengths. Quantum-level interference between the direct and free-induction decay components gives a spectral resolution that exceeds that of the excitation pulses. Appropriate parameter choices allow isolation of individual coherence pathways. The mixed frequency/time domain approach allows one to access any set of quantum states with coherent multidimensional spectroscopy. PMID:16526612

  4. Studies in protein dynamics using heteronuclear nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Vugmeyster, Liliya

    Dynamic processes in proteins are important for their biological function. Several issues in protein dynamics are addressed by applying existing NMR methodologies to investigate dynamics of several small proteins. Amide H/D exchange rates have been measured for the N-terminal domain of the ribosomal protein L9, residues 1--56. The results suggest that the structure of the domain is preserved in isolation and that the stability of the isolated domain is comparable to the stability of this domain in intact L9. Single domain proteins can fold in vitro at rates in excess of 1 x 104 s-1. Measurement of folding rates of this magnitude poses a considerable technical challenge. Off-resonance 15N R1rho measurements are shown to be capable of measuring such fast protein folding rates. The measurements were performed on a sample of the peripheral subunit-binding domain from the dihydrolopoamide acetyltransferase component of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus 15N labeled at Ala 11. Fast intramolecular motions (on ps-ns time scale) can be studied by heteronuclear laboratory frame NMR relaxation. The temperature dependence of the backbone dynamics of the 36-resiude subdomain of the F-actin bundling protein villin has been investigated by studying the temperature dependence of order parameters obtained from 15N relaxation measurements. The results support the hypothesis that one of the possible mechanisms of thermostability is to lower the heat capacity difference between the folded and unfolded states by lowering the contribution from the backbone dynamics. A commonly used model-free approach for the interpretation of the relaxation data for macromolecules in solution is modified to correct for the decoupling approximation between the overall and internal motions.

  5. Heteronuclear three-body parameter pinned down by multichannel spinor model

    NASA Astrophysics Data System (ADS)

    Wang, Yujun; Julienne, Paul S.; Greene, Chris H.

    2015-05-01

    Although a quantitative study of ultracold three-body collisions has been recently performed for homonuclear atomic systems, a similar theoretical study for heteronuclear ones has not been available. In this work we show progress in predicting Efimov-like three-body resonances using multichannel spinor models. In particular, we show that our calculations correctly predict the experimental observed isotope dependence of the atom-diatomic resonances in 87Rb-87Rb-40K and 87Rb-87Rb-41K systems without fitting parameters. Our study demonstrates that with our simple spinor models, quantitative characterization of ultracold chemical processes for heteronuclear systems is in principle feasible. Application of our model to other heteronuclear alkali-metal systems is also discussed. The authors acknowledge the support of an AFOSR-MURI FA9550-09-1-0617, Y.W. also acknowledges the support of Department of Physics, Kansas State University.

  6. Heteronuclear refocusing by nonlinear phase and amplitude modulation on a single transmitter channel.

    PubMed

    Moore, Jay; Colón, Raul D; Tadanki, Sasidhar; Waddell, Kevin W

    2014-08-01

    The application of low magnetic fields to heteronuclear NMR has expanded recently alongside the emergence of methods for achieving near unity polarization of spin ensembles, independent of magnetic field strength. The parahydrogen induced hyperpolarization methods in particular, often use a hybrid arrangement where a high field spectrometer is used to detect or image polarized molecules that have been conjured on a separate, dedicated polarizer instrument operating at fields in the mT regime where yields are higher. For controlling polarizer chemistry, spare TTL channels of portable NMR spectrometers can be used to pulse program reaction timings in synchrony with heteronuclear RF transformations. The use of a spectrometer as a portable polarizer control module has the advantage of allowing detection in situ, simplifying the process of optimizing polarization yields prior to in vivo experimental trials. Suitable heteronuclear spectrometers compatible with this application are becoming more common, but are still sparsely available in comparison to a large existing infrastructure of single channel NMR consoles. With the goal of expanding the range of these systems to multinuclear applications, the feasibility of rotating a pair of heteronuclear spins ((13)C and (1)H) at 12mT was investigated in this study. Nonlinear phase and amplitude modulated waveforms designed to simultaneously refocus magnetization at 128kHz ((13)C) and 510kHz ((1)H) were generated numerically with optimal control. Although precise quantitative comparisons were not attempted due to limitations of the experimental setup, signals refocused at heteronuclear frequencies with this PANORAMIC approach (Precession And Nutation for Observing Rotation At Multiple Intervals about the Carrier) yielded amplitudes comparable to signals which were refocused using traditional block pulses on heteronuclear channels. Using this PANORAMIC approach to heteronuclear NMR at low field would reduce expense as well as

  7. Determination of unresolved heteronuclear scalar coupling constants by J(up)-HSQMBC.

    PubMed

    Glanzer, Simon; Kunert, Olaf; Zangger, Klaus

    2016-07-01

    Long-range heteronuclear scalar coupling constants provide important structural information, which is necessary for obtaining stereospecific assignment or dihedral angle information. The measurement of small proton-carbon splittings is particularly difficult due to the low natural abundance of carbon-13 and the presence of homonuclear couplings of similar size. Here we present a real-time J-upscaled HSQMBC, which allows the measurement of heteronuclear coupling constants even if they are hidden in the signal linewidth of a regular spectrum. PMID:27183090

  8. Engineering of an all-heteronuclear 5-qubit NMR quantum computer.

    PubMed

    Marx, Raimund; Pomplun, Nikolas; Bermel, Wolfgang; Zeiger, Heinz; Engelke, Frank; Fahmy, Amr F; Glaser, Steffen J

    2015-06-01

    The realization of an all-heteronuclear 5-qubit nuclear magnetic resonance quantum computer is reported, from the design and synthesis of a suitable molecule through the engineering of a prototype 6-channel probe head. Full control over the quantum computer is shown by a benchmark experiment. PMID:25854330

  9. 1H, 13C and 15N resonance assignments and secondary structure analysis of CmPI-II, a serine protease inhibitor isolated from marine snail Cenchritis muricatus.

    PubMed

    Cabrera-Muñoz, Aymara; Rojas, Laritza; Alonso-del-Rivero Antigua, Maday; Pires, José Ricardo

    2016-04-01

    A protease inhibitor (CmPI-II) (UNIPROT: IPK2_CENMR) from the marine mollusc Cenchritis muricatus, has been isolated and characterized. It is the first member of a new group (group 3) of non-classical Kazal-type inhibitors. CmPI-II is a tight-binding inhibitor of serine proteases: trypsin, human neutrophil elastase (HNE), subtilisin A and pancreatic elastase. This specificity is exceptional in the members of Kazal-type inhibitor family. Several models of three-dimensional structure of CmPI-II have been constructed by homology with other inhibitors of the family but its structure has not yet been solved experimentally. Here we report the (1)H, (15)N and (13)C chemical shift assignments of CmPI-II as basis for NMR structure determination and interaction studies. Secondary structure analyses deduced from the NMR chemical shift data have identified three β-strands β1: residues 14-19, β2: 23-35 and β3: 43-45 and one helix α1: 28-37 arranged in the sequential order β1-β2-α1-β3. These secondary structure elements suggest that CmPI-II adopts the typical scaffold of a Kazal-type inhibitor. PMID:26547437

  10. Backbone and Ile-δ1, Leu, Val Methyl 1H, 13C and 15N NMR chemical shift assignments for human interferon-stimulated gene 15 protein

    SciTech Connect

    Yin, Cuifeng; Aramini, James M.; Ma, LiChung; Cort, John R.; Swapna, G.V.T.; Krug, R. M.; Montelione, Gaetano

    2011-10-01

    Human interferon-stimulated gene 15 protein (ISG15), also called ubiquitin cross-reactive protein (UCRP), is the first identified ubiquitin-like protein containing two ubiquitin-like domains fused in tandem. The active form of ISG15 is conjugated to target proteins via the C-terminal glycine residue through an isopeptide bond in a manner similar to ubiquitin. The biological role of ISG15 is strongly associated with the modulation of cell immune function, and there is mounting evidence suggesting that many viral pathogens evade the host innate immune response by interfering with ISG15 conjugation to both host and viral proteins in a variety of ways. Here we report nearly complete backbone 1HN, 15N, 13CO, and 13Ca, as well as side chain 13Cb, methyl (Ile-d1, Leu, Val), amide (Asn, Gln), and indole NH (Trp) NMR resonance assignments for the 157-residue human ISG15 protein. These resonance assignments provide the basis for future structural and functional solution NMR studies of the biologically important human ISG15 protein.

  11. Primidone - An antiepileptic drug - characterisation by quantum chemical and spectroscopic (FTIR, FT-Raman, 1H, 13C NMR and UV-Visible) investigations

    NASA Astrophysics Data System (ADS)

    Arjunan, V.; Santhanam, R.; Subramanian, S.; Mohan, S.

    2013-05-01

    The solid phase FTIR and FT-Raman spectra of primidone were recorded in the regions 4000-400 cm-1 and 4000-100 cm-1, respectively. The vibrational spectra were analysed and the observed fundamentals were assigned and analysed. The experimental wavenumbers were compared with the theoretical scaled vibrational wavenumbers determined by DFT methods. The Raman intensities were also determined with B3LYP/6-31G(d,p) method. The total electron density and molecular electrostatic potential surface of the molecule were constructed by using B3LYP/6-311++G(d,p) method to display electrostatic potential (electron + nuclei) distribution. The HOMO and LUMO energies were measured. Natural bond orbital analysis of primidone has been performed to indicate the presence of intramolecular charge transfer. The 1H and 13C NMR spectra were recorded and the chemical shifts of the molecule were calculated.

  12. Use of dipolar 1H-15N and 1H-13C couplings in the structure determination of magnetically oriented macromolecules in solution.

    PubMed

    Tjandra, N; Omichinski, J G; Gronenborn, A M; Clore, G M; Bax, A

    1997-09-01

    Anisotropy of the molecular magnetic susceptibility gives rise to a small degree of alignment. The resulting residual dipolar couplings, which can now be measured with the advent of higher magnetic fields in NMR, contain information on the orientation of the internuclear vectors relative to the molecular magnetic susceptibility tensor, thereby providing information on long range order that is not accessible by any of the solution NMR parameters currently used in structure determination. Thus, the dipolar couplings constitute unique and powerful restraints in determining the structures of magnetically oriented macromolecules in solution. The method is demonstrated on a complex of the DNA-binding domain of the transcription factor GATA-1 with a 16 base pair oligodeoxyribonucleotide. PMID:9303001

  13. 1H, 13C and 15N NMR assignments of the E. coli peptide deformylase in complex with a natural inhibitor called actinonin.

    PubMed

    Larue, Valéry; Seijo, Bili; Tisne, Carine; Dardel, Frédéric

    2009-06-01

    In eubacteria, the formyl group of nascent polypeptides is removed by peptide deformylase protein (PDF). This is the reason why PDF has received special attention in the course of the search for new antibacterial agents. We observed by NMR that actinonin, a natural inhibitor, induced drastic changes in the HSQC spectrum of E. coli PDF. We report here the complete NMR chemical shift assignments of PDF resonances bound to actinonin. PMID:19636969

  14. (1)H, (13)C, and (15)N chemical shift assignments of cyanobacteriochrome NpR6012g4 in the green-absorbing photoproduct state.

    PubMed

    Lim, Sunghyuk; Yu, Qinhong; Rockwell, Nathan C; Martin, Shelley S; Lagarias, J Clark; Ames, James B

    2016-04-01

    Cyanobacteriochromes (CBCRs) are cyanobacterial photosensory proteins with a tetrapyrrole (bilin) chromophore that belong to the phytochrome superfamily. Like phytochromes, CBCRs photoconvert between two photostates with distinct spectral properties. NpR6012g4 from Nostoc punctiforme is a model system for widespread CBCRs with conserved red/green photocycles. Atomic-level structural information for the photoproduct state in this subfamily is not known. Here, we report NMR backbone chemical shift assignments of the light-activated state of NpR6012g4 (BMRB no. 26577) as a first step toward determining its atomic resolution structure. PMID:26537963

  15. FT-IR, 1H, 13C NMR, ESI-MS and semiempirical investigation of the structures of Monensin phenyl urethane complexes with the sodium cation.

    PubMed

    Huczyński, Adam

    2013-06-01

    In this paper three forms of phenyl urethane of Monensin i.e. its acid form (H-MU) and its 1:1 complex with NaClO4 (H-MU-Na) and its sodium salt (Na-MU) were obtained and their structures were studied by FT-IR, (1)H and (13)C NMR, ESI MS and PM5 methods. The FT-IR data of Na-MU complexes demonstrate that the C=O urethane group is not engaged in the complexation of the sodium cation. However spectroscopic studies of H-MU-Na complex show that the structure in which this C=O urethane groups participate in the complexation is also present, but it is in the minority. The PM5 semiempirical calculations allow visualisation of all structures and determination of the hydrogen bond parameters. PMID:23578536

  16. (1)H-, (13)C- and (15)N-NMR assignment of the N-terminal domain of human cerebral dopamine neurotrophic factor (CDNF).

    PubMed

    Latgé, Cristiane; Cabral, Kátia M S; Almeida, Marcius S; Foguel, Débora

    2013-04-01

    Parkinson's disease (PD) is a neurodegenerative disorder that is caused by the death of midbrain dopaminergic neurons. Current therapies for PD do not halt the neurodegeneration nor repair the affected neurons. Therefore, search for novel neurotrophic factors (NTF) for midbrain dopaminergic neurons, which could be used in novel therapeutic approaches, is highly wanted. In 2007, a potent NTF for dopaminergic neurons was described as the conserved dopamine neurotrophic factor (CDNF). Single doses of this protein protect and restore dopaminergic neurons in experimental models of PD. CDNF has two domains; an N-terminal saposin-like domain, which may bind to membranes; and a presumably intrinsically unstructured C-terminal which contains an internal cysteine bridge in a CXXC motif similar to that of thiol/disulphide oxidoreductases and isomerases, and may thus reduce the endoplasmic reticulum stress caused by incorrectly folded proteins. We show for the first time the nuclear magnetic resonance assignment of N-terminal domain of recombinant CDNF (residues 1-105) by solution 2D and 3D NMR spectroscopy. We were able to obtain a nearly complete resonance assignment, which is the first step toward the solution structure determination of this neurotrophic factor. PMID:22528768

  17. Homo- and heteronuclear 2D NMR approaches to analyse a mixture of deuterated unlike/like stereoisomers using weakly ordering chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Ben Ali, Karim; Lafon, Olivier; Zimmermann, Herbert; Guittet, Eric; Lesot, Philippe

    2007-08-01

    We describe several homo- and heteronuclear 2D NMR strategies dedicated to the analysis of anisotropic 2H spectra of a mixture of dideuterated unlike/like stereoisomers with two remote stereogenic centers, using weakly orienting chiral liquid crystals. To this end, we propose various 2D correlation experiments, denoted "D(H) nD" or "D(H) nC" (with n = 1, 2), that involve two heteronuclear polarization transfers of INEPT-type with one or two proton relays. The analytical expressions of correlation signals for four pulse sequences reported here were calculated using the product-operators formalism for spin I = 1 and S = 1/2. The features and advantages of each scheme are presented and discussed. The efficiency of these 2D sequences is illustrated using various deuterated model molecules, dissolved in organic solutions of polypeptides made of poly- γ-benzyl- L-glutamate (PBLG) or poly- ɛ-carbobenzyloxy- L-lysine (PCBLL) and NMR numerical simulations.

  18. Heteronuclear NMR of DNA with the heteronucleus in natural abundance: facilitated assignment and extraction of coupling constants.

    PubMed Central

    Schmieder, P; Ippel, J H; van den Elst, H; van der Marel, G A; van Boom, J H; Altona, C; Kessler, H

    1992-01-01

    Two heteronuclear proton-carbon NMR experiments are applied to the DNA-octamer d(TTGGCCAA)2 with carbon in natural abundance. They lead to a complete assignment of the carbon resonances of the sugars and bases. In addition, several heteronuclear coupling constants, proton-carbon as well as proton-phosphorous and phosphorous-carbon, were determined. The information can be obtained in a reasonable measuring time and offers valuable information for a detailed picture of DNA structure. PMID:1408787

  19. Characterization of heteronuclear decoupling through proton spin dynamics in solid-state nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    De Paëpe, Gaël; Eléna, Bénédicte; Emsley, Lyndon

    2004-08-01

    The work presented here aims at understanding the performance of phase modulated heteronuclear decoupling sequences such as Cosine Modulation or Two Pulse Phase Modulation. To that end we provide an analytical description of the intrinsic behavior of Cosine Modulation decoupling with respect to radio-frequency-inhomogeneity and the proton-proton dipolar coupling network. We discover through a Modulation Frame average Hamiltonian analysis that best decoupling is obtained under conditions where the heteronuclear interactions are removed but notably where homonuclear couplings are recoupled at a homonuclear Rotary Resonance (HORROR) condition in the Modulation Frame. These conclusions are supported by extensive experimental investigations, and notably through the introduction of proton nutation experiments to characterize spin dynamics in solids under decoupling conditions. The theoretical framework presented in this paper allows the prediction of the optimum parameters for a given set of experimental conditions.

  20. Measurement of Heteronuclear Dipolar Coupling by Transferred-Echo Double-Resonance NMR

    NASA Astrophysics Data System (ADS)

    Hing, A. W.; Vega, S.; Schaefer, J.

    A magic-angle spinning experiment called transferred-echo double resonance (TEDOR) has been introduced recently to measure the I-S dipolar coupling of heteronuclear I-S pairs of spin- {1}/{2} nuclei while eliminating unwanted background signals from uncoupled I and S spins via a coherence-transfer process. In this paper, a quantitative description of the TEDOR experiment is given in terms of the evolution of the density matrix for a pair of heteronuclear spins. The resulting equations provide a theoretical basis for evaluating the selectivity and sensitivity of TEDOR and suggest strategies for determining dipolar coupling constants directly from TEDOR data. Experimental examples illustrating these aspects of TEDOR are provided by studies performed on a range of 13C- 15N dipolar couplings found in double-labeled asparagine, alanine, glycine, and the linear peptide antibiotic, gramicidin.

  1. The possibility of laser action in ionic heteronuclear molecules. I - Spectroscopy. II - Kinetics

    NASA Astrophysics Data System (ADS)

    Basov, N. G.; Voitik, M. G.; Zuev, V. S.; Kutakhov, V. P.

    1985-11-01

    A theoretical study is presented of the electronic structure of levels of ionic heteronuclear molecules (IHM) consisting of atoms and ions of inert gases, halogens, the oxygen group, and alkali metals. Electron transitions are found which are promising for the generation of laser action in the visible, UV, and far UV (greater than 70 nm). In addition, the feasibility of a new family of IHM gas lasers emitting in the above-mentioned ranges is demonstrated theoretically.

  2. Long-range dispersion interactions. I. Formalism for two heteronuclear atoms

    SciTech Connect

    Zhang, J.-Y.; Mitroy, J.

    2007-08-15

    A general procedure for systematically evaluating the long-range dispersion interaction between two heteronuclear atoms in arbitrary states is outlined. The C{sub 6} dispersion parameter can always be written in terms of sum rules involving oscillator strengths only and formulas for a number of symmetry cases are given. The dispersion coefficients for excited alkali-metal atoms interacting with the ground-state H and He are tabulated.

  3. Resolution and measurement of heteronuclear dipolar couplings of a noncrystalline protein immobilized in a biological supramolecular assembly by proton-detected MAS solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Park, Sang Ho; Yang, Chen; Opella, Stanley J.; Mueller, Leonard J.

    2013-12-01

    Two-dimensional 15N chemical shift/1H chemical shift and three-dimensional 1H-15N dipolar coupling/15N chemical shift/1H chemical shift MAS solid-state NMR correlation spectra of the filamentous bacteriophage Pf1 major coat protein show single-site resolution in noncrystalline, intact-phage preparations. The high sensitivity and resolution result from 1H detection at 600 MHz under 50 kHz magic angle spinning using ∼0.5 mg of perdeuterated and uniformly 15N-labeled protein in which the exchangeable amide sites are partially or completely back-exchanged (reprotonated). Notably, the heteronuclear 1H-15N dipolar coupling frequency dimension is shown to select among 15N resonances, which will be useful in structural studies of larger proteins where the resonances exhibit a high degree of overlap in multidimensional chemical shift correlation spectra.

  4. A unified heteronuclear decoupling strategy for magic-angle-spinning solid-state NMR spectroscopy

    SciTech Connect

    Equbal, Asif; Bjerring, Morten; Nielsen, Niels Chr. E-mail: ncn@inano.au.dk; Madhu, P. K. E-mail: ncn@inano.au.dk

    2015-05-14

    A unified strategy of two-pulse based heteronuclear decoupling for solid-state magic-angle spinning nuclear magnetic resonance is presented. The analysis presented here shows that different decoupling sequences like two-pulse phase-modulation (TPPM), X-inverse-X (XiX), and finite pulse refocused continuous wave (rCW{sup A}) are basically specific solutions of a more generalized decoupling scheme which incorporates the concept of time-modulation along with phase-modulation. A plethora of other good decoupling conditions apart from the standard, TPPM, XiX, and rCW{sup A} decoupling conditions are available from the unified decoupling approach. The importance of combined time- and phase-modulation in order to achieve the best decoupling conditions is delineated. The consequences of different indirect dipolar interactions arising from cross terms comprising of heteronuclear and homonuclear dipolar coupling terms and also those between heteronuclear dipolar coupling and chemical-shift anisotropy terms are presented in order to unfold the effects of anisotropic interactions under different decoupling conditions. Extensive numerical simulation results are corroborated with experiments on standard amino acids.

  5. Methodology for solid state NMR off-resonance study of molecular dynamics in heteronuclear systems.

    PubMed

    Jurga, Kazimierz; Woźniak-Braszak, Aneta; Baranowski, Mikołaj

    2015-10-01

    Methodology for the study of dynamics in heteronuclear systems in the laboratory frame was described in the previous paper [1]. Now the methodology for the study of molecular dynamics in the solid state heteronuclear systems in the rotating frame is presented. The solid state NMR off-resonance experiments were carried out on a homemade pulse spectrometer operating at the frequency of 30.2 MHz for protons. This spectrometer includes a specially designed probe which contains two independently tuned and electrically isolated coils installed in the coaxial position on the dewar. A unique probe design allows working at three slightly differing frequencies off and on resonance for protons and at the frequency of 28.411 MHz for fluorine nuclei with complete absence of their electrical interference. The probe allows simultaneously creating rf magnetic fields at off-resonance frequencies within the range of 30.2-30.6 MHz and at the frequency of 28.411 MHz. Presented heteronuclear cross-relaxation off-resonance experiments in the rotating frame provide information about molecular dynamics. PMID:26272112

  6. High-order-harmonic generation in homonuclear and heteronuclear diatomic molecules: Exploration of multiple orbital contributions

    SciTech Connect

    Heslar, John; Telnov, Dmitry; Chu, Shih-I

    2011-04-15

    We present a time-dependent density functional theory (TDDFT) approach with proper asymptotic long-range potential for nonperturbative treatment of high-order harmonic generation (HHG) of diatomic molecules with their molecular axis parallel to the laser field polarization. A time-dependent two-center generalized pseudospectral method in prolate spheroidal coordinate system is used for accurate and efficient treatment of the TDDFT equations in space and time. The theory is applied to a detailed all-electron nonperturbative investigation of HHG processes of homonuclear (N{sub 2} and F{sub 2}) and heteronuclear (CO, BF, and HF) molecules in intense ultrashort laser pulses with the emphasis on the role of multiple molecular orbitals (MOs). The results reveal intriguing and substantially different nonlinear optical response behaviors for homonuclear and heteronuclear molecules. In particular, we found that the HHG spectrum for homonuclear molecules features a destructive interference of MO contributions while heteronuclear molecules show mostly constructive interference of orbital contributions.

  7. Three-dimensional solution structure of mouse [Cd7]-metallothionein-1 by homonuclear and heteronuclear NMR spectroscopy.

    PubMed Central

    Zangger, K.; Oz, G.; Otvos, J. D.; Armitage, I. M.

    1999-01-01

    Sequential 1H-NMR assignments of mouse [Cd7]-metallothionein-1 (MT1) have been carried out by standard homonuclear NMR methods and the use of an accordion-heteronuclear multiple quantum correlation (HMQC) experiment for establishing the metal, 113Cd2+, to cysteine connectivities. The three-dimensional structure was then calculated using the distance constraints from two-dimensional nuclear Overhauser effect (NOE) spectroscopy spectra and the Cys-Cd connectivities as input for a distance geometry-dynamical simulated annealing protocol in X-PLOR 3.851. Similar to the mammalian MT2 isoforms, the homologous primary structure of MT1 suggested two separate domains, each containing one metal cluster. Because there were no interdomain constraints, the structure calculation for the N-terminal beta- and the C-terminal alpha-domain were carried out separately. The structures are based on 409 NMR constraints, consisting of 381 NOEs and 28 cysteine-metal connectivities. The only elements of regular secondary structure found were two short stretches of 3(10) helices along with some half-turns in the alpha-domain. Structural comparison with rat liver MT2 showed high similarity, with the beta-domain structure in mouse MT1 showing evidence of increased flexibility compared to the same domain in MT2. The latter was reflected by the presence of fewer interresidue NOEs, no slowly exchanging backbone amide protons, and enhanced cadmium-cadmium exchange rates found in the beta-domain of MT1. PMID:10631978

  8. Heteronuclear dipolar couplings, total spin coherence, and bilinear rotations in NMR spectroscopy

    SciTech Connect

    Garbow, J.R.

    1983-07-01

    In Chapter 1 a variety of different introductory topics are presented. The potential complexity of the nuclear magnetic resonsnace (NMR) spectra of molecules dissolved in liquid crystal solvents serves to motivate the development of multiple quantum (MQ) spectroscopy. The basics of MQ NMR are reviewed in Chapter 2. An experimental search procedure for the optimization of MQ pulse sequences is introduced. Chapter 3 discusses the application of MQ NMR techniques to the measurement of dipolar couplings in heteronuclear spin systems. The advantages of MQ methods in such systems are developed and experimental results for partially oriented (1-/sup 13/C) benzene are presented. Several pulse sequences are introduced which employ a two-step excitation of heteronuclear MQ coherence. A new multiple pulse method, involving the simultaneous irradiation of both rare and abundant spin species, is described. The problem of the broadening of MQ transitions due to magnetic field inhomogeneity is considered in Chapter 4. The method of total spin coherence transfer echo spectroscopy (TSCTES) is presented, with experimets on partially oriented acetaldehyde serving to demonstrate this new technique. TSCTES results in MQ spectra which are sensitive to all chemical shifts and spin-spin couplings and which are free of inhomogeneous broadening. In Chapter 5 the spectroscopy of spin systems of several protons and a /sup 13/C nucleus in the isotropic phase is discussed. The usefulness of the heteronuclear bilinear rotation as a calculational tool is illustrated. Compensated bilinear ..pi.. rotations, which are relatively insensitive to timing parameter missets, are presented. A new technique for homonuclear proton decoupling, Bilinear Rotation Decoupling, is described and its success in weakly coupled systems is demonstrated.

  9. Selective charge asymmetric distribution in heteronuclear diatomic molecules in strong laser fields

    NASA Astrophysics Data System (ADS)

    Lai, Wei; Guo, Chunlei

    2015-07-01

    In this paper we study double-ionization-induced charge asymmetric dissociation (CAD) in heteronuclear diatomic molecules. In CO we find a selective charge distribution in two CAD channels, i.e., C2 ++O is abundantly produced but C +O2 + is nearly nonexistent. This cannot be explained by the ionization energy difference between the two channels alone. Our study shows that the C2 ++O channel is sequentially formed through an intermediate state C++O and the selective charge distribution is the result of electron distribution in CO when exposed to intense laser fields.

  10. Quantum atom-heteronuclear molecule dark state: Role of population imbalance

    SciTech Connect

    Jing Hui; Cui Shuai

    2010-08-15

    Recently, the finite-number effect of initial atoms in coherent atom-molecule conversion was investigated by Zhao et al. [Phys. Rev. Lett. 101, 010401 (2008)]. Here, by extending to the atom-heteronuclear molecule dark state, we find that the initial populations imbalance of the atoms plays a significant role in quantum conversion rate and adiabatic fidelity. In particular, even for the finite total number of imbalanced two-species atoms, the mean-field conversion rate, contrary to the general belief, still can be remarkably close to the exact quantum results.

  11. Achievement of 1 H-19 F heteronuclear experiments using the conventional spectrometer with a shared single high band amplifier.

    PubMed

    Sakuma, Chiseko; Kurita, Jun-ichi; Furihata, Kazuo; Tashiro, Mitsuru

    2015-05-01

    The (1)H-(19) F heteronuclear NMR experiments were achieved using the conventional spectrometer equipped with a single high band amplifier and a (1)H/(19)F/(13) C double-tuned probe. Although double high band amplifiers are generally required to perform such experiments, a simple modification of pathway in the conventional spectrometer was capable of acquiring various (1)H-(19)F heteronuclear spectra. The efficiency of the present technique was demonstrated in an application for (19)F{(1)H} and (1)H{(19)F} saturation transfer difference experiments. PMID:25808615

  12. Secondary structure and side-chain sup 1 H and sup 13 C resonance assignments of calmodulin in solution by heteronuclear multidimensional NMR spectroscopy

    SciTech Connect

    Ikura, Mitsuhiko; Spera, S.; Barbato, G.; Kay, L.E.; Bax, A. ); Krinks, M. )

    1991-09-24

    Heteronuclear 2D and 3D NMR experiments were carried out on recombinant Drosophila calmodulin (CaM), a protein of 148 residues and with molecular mass of 16.7 kDa, that is uniformly labeled with {sup 15}N and {sup 13}C to a level of > 95%. Nearly complete {sup 1}H and {sup 13}C side-chain assignments for all amino acid residues are obtained by using the 3D HCCH-COSY and HCCH-TOCSY experiments that rely on large heteronuclear one-bond scalar couplings to transfer magnetization and establish through-bond connectivities. The secondary structure of this protein in solution has been elucidated by a qualitative interpretation of nuclear Overhauser effects, hydrogen exchange data, and {sup 3}J{sub HNH{alpha}} coupling constants. A clear correlation between the {sup 13}C{alpha} chemical shift and secondary structure is found. The secondary structure in the two globular domains of Drosophila CaM in solution is essentially identical with that of the X-ray crystal structure of mammalian CaM which consists of two pairs of a helix-loop-helix motif in each globular domain. The existence of a short antiparallel {beta}-sheet between the two loops in each domain has been confirmed. The eight {alpha}-helix segments identified from the NMR data are located at Glu-6 to Phe-19, thr-29 to Ser-38, Glu-45 to Glu-54, Phe-65 to Lys-77, Glu-82 to Asp-93, Ala-102 to Asn-111, Asp-118 to Glu-127, and Tyr-138 to Thr-146. Although the crystal structure has a long central helix from Phe-65 to Phe-92 that connects the two globular domains, NMR data indicate that residues Asp-78 to Ser-81 of this central helix adopt a nonhelical conformation with considerable flexibility.

  13. Primitive models of chemical association. IV. Polymer Percus{endash}Yevick ideal-chain approximation for heteronuclear hard-sphere chain fluids

    SciTech Connect

    Kalyuzhnyi, Y.V. |; Lin, C.; Stell, G.

    1998-04-01

    We continue here our series of studies in which integral-equation theory is developed and used for the monomer-monomer correlation functions in a fluid of multicomponent freely jointed hard-sphere polymers. In this study our approach is based on Wertheim{close_quote}s polymer Percus{endash}Yevick (PPY) theory supplemented by the ideal-chain approximation; it can be regarded as a simplified version of Wertheim{close_quote}s four-density PPY approximation for associating fluids considered in the complete-association limit. The numerical procedure of this simplified theory is much easier than that of the original Wertheim{close_quote}s four-density PPY approximation, but the degree of accuracy is reduced. The theory can also be regarded as an extension of the PPY theory for the homonuclear polymer system proposed by Chang and Sandler [J. Chem. Phys. {bold 102}, 437 (1995)]. Their work is based upon a description of a system of hard-sphere monomers that associate into a polydisperse system of chains of prescribed mean length. Our theory instead directly describes a multicomponent system of associating monomers that form monodisperse chains of prescribed length upon complete association. An analytical solution of the PPY ideal-chain approximation for the general case of a multicomponent mixture of heteronuclear hard-sphere linear chain molecules is given. Its use is illustrated by numerical results for two models of copolymer fluids, a symmetrical diblock copolymer system, and an alternating copolymer system. The comparison with Monte Carlo simulations is given to gauge the accuracy of the theory. We find for the molecules we study here that predictions of our theory for heteronuclear chain systems have the same degree of accuracy as Chang and Sandler{close_quote}s theory for homonuclear chain systems. {copyright} {ital 1998 American Institute of Physics.}

  14. Preparation of 13C and 15N labelled RNAs for heteronuclear multi-dimensional NMR studies.

    PubMed

    Nikonowicz, E P; Sirr, A; Legault, P; Jucker, F M; Baer, L M; Pardi, A

    1992-09-11

    A procedure is described for the efficient preparation of isotopically enriched RNAs of defined sequence. Uniformly labelled nucleotide 5'triphosphates (NTPs) were prepared from E.coli grown on 13C and/or 15N isotopically enriched media. These procedures routinely yield 180 mumoles of labelled NTPs per gram of 13C enriched glucose. The labelled NTPs were then used to synthesize RNA oligomers by in vitro transcription. Several 13C and/or 15N labelled RNAs have been synthesized for the sequence r(GGCGCUUGCGUC). Under conditions of high salt or low salt, this RNA forms either a symmetrical duplex with two U.U base pairs or a hairpin containing a CUUG loop respectively. These procedures were used to synthesize uniformly labelled RNAs and a RNA labelled only on the G and C residues. The ability to generate milligram quantities of isotopically labelled RNAs allows application of multi-dimensional heteronuclear magnetic resonance experiments that enormously simplify the resonance assignment and solution structure determination of RNAs. Examples of several such heteronuclear NMR experiments are shown. PMID:1383927

  15. Application of Natural Isotopic Abundance ¹H-¹³C- and ¹H-¹⁵N-Correlated Two-Dimensional NMR for Evaluation of the Structure of Protein Therapeutics.

    PubMed

    Arbogast, Luke W; Brinson, Robert G; Marino, John P

    2016-01-01

    Methods for characterizing the higher-order structure of protein therapeutics are in great demand for establishing consistency in drug manufacturing, for detecting drug product variations resulting from modifications in the manufacturing process, and for comparing a biosimilar to an innovator reference product. In principle, solution NMR can provide a robust approach for characterization of the conformation(s) of protein therapeutics in formulation at atomic resolution. However, molecular weight limitations and the perceived need for stable isotope labeling have to date limited its practical applications in the biopharmaceutical industry. Advances in NMR magnet and console technologies, cryogenically cooled probes, and new rapid acquisition methodologies, particularly selective optimized flip-angle short transient pulse schemes and nonuniform sampling, have greatly ameliorated these limitations. Here, we describe experimental methods for the collection and analysis of 2D (1)H(N)-(15)N-amide- and (1)H-(13)C-methyl-correlated spectra applied to protein drug products at natural isotopic abundance, including representatives from the rapidly growing class of monoclonal antibody (mAb) therapeutics. Practical aspects of experimental setup and data acquisition for both standard and rapid acquisition NMR techniques are described. Furthermore, strategies for the statistical comparison of 2D (1)H(N)-(15)N-amide- and (1)H-(13)C-methyl-correlated spectra are detailed. PMID:26791974

  16. Energetics and Control of Ultracold Isotope-Exchange Reactions between Heteronuclear Dimers in External Fields

    NASA Astrophysics Data System (ADS)

    Tomza, Michał

    2015-08-01

    We show that isotope-exchange reactions between ground-state alkali-metal, alkaline-earth-metal, and lanthanide heteronuclear dimers consisting of two isotopes of the same atom are exothermic with an energy change in the range of 1-8000 MHz, thus resulting in cold or ultracold products. For these chemical reactions, there are only one rovibrational and at most several hyperfine possible product states. The number and energetics of open and closed reactive channels can be controlled by the laser and magnetic fields. We suggest a laser-induced isotope- and state-selective Stark shift control to tune the exothermic isotope-exchange reactions to become endothermic, thus providing the ground for testing models of the chemical reactivity. The present proposal opens the way for studying the state-to-state dynamics of ultracold chemical reactions beyond the universal limit with a meaningful control over the quantum states of both reactants and products.

  17. Energetics and Control of Ultracold Isotope-Exchange Reactions between Heteronuclear Dimers in External Fields.

    PubMed

    Tomza, Michał

    2015-08-01

    We show that isotope-exchange reactions between ground-state alkali-metal, alkaline-earth-metal, and lanthanide heteronuclear dimers consisting of two isotopes of the same atom are exothermic with an energy change in the range of 1-8000 MHz, thus resulting in cold or ultracold products. For these chemical reactions, there are only one rovibrational and at most several hyperfine possible product states. The number and energetics of open and closed reactive channels can be controlled by the laser and magnetic fields. We suggest a laser-induced isotope- and state-selective Stark shift control to tune the exothermic isotope-exchange reactions to become endothermic, thus providing the ground for testing models of the chemical reactivity. The present proposal opens the way for studying the state-to-state dynamics of ultracold chemical reactions beyond the universal limit with a meaningful control over the quantum states of both reactants and products. PMID:26296115

  18. Two-center interference in high-order harmonic generation from heteronuclear diatomic molecules.

    PubMed

    Zhu, Xiaosong; Zhang, Qingbin; Hong, Weiyi; Lan, Pengfei; Lu, Peixiang

    2011-01-17

    Two-center interference for heteronuclear diatomic molecules (HeDM) is investigated. The minimum in the high-order harmonic spectrum, as a consequence of the destructive interference, is shifted to lower harmonic orders compared with that in a homonuclear case. This phenomenon is explained by performing phase analysis. It is found that, for an HeDM, the high harmonic spectrum contains information not only on the internuclear separation but also on the properties of the two separate centers, which implies the potential application of estimating the asymmetry of molecules and judging the linear combination of atomic orbitals (LCAO) for the highest occupied molecular orbital (HOMO). Moreover, the possibility to monitor the evolution of HOMO itself in molecular dynamics is also promised. PMID:21263583

  19. Heteronuclear decoupling in MAS NMR in the intermediate to fast sample spinning regime

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Bjerring, Morten; Sharma, Kshama; Madhu, P. K.; Nielsen, Niels Chr.

    2016-01-01

    Heteronuclear spin decoupling in solid-state magic-angle spinning NMR is investigated to present methods overcoming interferences between rf irradiation and sample spinning in the intermediate to fast spinning regime. We demonstrate that a recent phase-alternated variant of refocused CW irradiation (rCWApA) provides efficient and robust decoupling in this regime. An extensive experimental and numerical comparison is presented for rCWApA and PISSARRO (phase-inverted supercycled sequence for attenuation of rotary resonance), previously introduced to quench rotary-resonance recoupling effects, under conditions with spinning frequencies between 30 and 60 kHz. Simulations are used to identify the effect of decoupling for various nuclear spin interactions.

  20. Interaction-induced decay of a heteronuclear two-atom system

    PubMed Central

    Xu, Peng; Yang, Jiaheng; Liu, Min; He, Xiaodong; Zeng, Yong; Wang, Kunpeng; Wang, Jin; Papoular, D. J.; Shlyapnikov, G. V.; Zhan, Mingsheng

    2015-01-01

    Two-atom systems in small traps are of fundamental interest for understanding the role of interactions in degenerate cold gases and for the creation of quantum gates in quantum information processing with single-atom traps. One of the key quantities is the inelastic relaxation (decay) time when one of the atoms or both are in a higher hyperfine state. Here we measure this quantity in a heteronuclear system of 87Rb and 85Rb in a micro optical trap and demonstrate experimentally and theoretically the presence of both fast and slow relaxation processes, depending on the choice of the initial hyperfine states. This experimental method allows us to single out a particular relaxation process thus provides an extremely clean platform for collisional physics studies. Our results have also implications for engineering of quantum states via controlled collisions and creation of two-qubit quantum gates. PMID:26199051

  1. Interactions between Nafion resin and protonated dodecylamine modified montmorillonite: a solid state NMR study.

    PubMed

    Zhang, Limin; Xu, Jun; Hou, Guangjin; Tang, Huiru; Deng, Feng

    2007-07-01

    A series of nanocomposites have been prepared from perfluorosulfonylfluoride copolymer resin (Nafion) and layered montmorillonite (MMT) modified with protonated dodecylamine by conventional sol-gel intercalation. The structure of these nanocomposite materials have been characterized using FT-IR, elemental analysis, XRD and solid state NMR techniques, including 19F magic-angle spinning (MAS) NMR, 19F NMR relaxation time measurements, 29Si MAS, 1H MAS, 1H-13C cross-polarization magic-angle spinning (CPMAS), and 1H-13C heteronuclear correlation (HETCOR) 2D NMR. The results showed that thermal stability of Nafion was improved moderately by the addition of dodecylamine modified MMT without intercalation. FT-IR and 29Si MAS NMR results indicated that dodecylamine modification did not result in obvious changes in the MMT lattice structure. The XRD results showed that the protonated dodecylamine has been embedded and intercalated into the MMT interlayers, whereas Nafion was not. Elemental analysis results also suggested that some dodecylamine was adsorbed on the surface of MMT. 1H-13C HETCOR 2D NMR experiment clearly indicated that strong electrostatic interactions were present between the NH+3 group of dodecylamine and the fluorine-containing groups (CF3, OCF2, and SCF2) of Nafion resin. Such electrostatic interactions are probably the major contributors for the improved thermal stability of the resultant composite materials. PMID:17382953

  2. Epitope Mapping of Antigenic MUC1 Peptides to Breast Cancer Antibody Fragment B27.29: A Heteronuclear NMR Study

    SciTech Connect

    Grinstead, Jeffrey S.; Schuman, Jason T.; Campbell, Ann P.

    2003-11-13

    MUC1 mucin is a breast cancer-associated transmembrane glycoprotein, of which the extracellular domain is formed by the repeating 20-amino acid sequence GVTSAPDTRPAPGSTAPPAH. In neoplastic breast tissue, the highly immunogenic sequence PDTRPAP (in bold above) is exposed. Antibodies raised directly against MUC1-expressing tumors offer unique access to this neoplastic state, as they represent immunologically relevant ''reverse templates'' of the tumor-associated mucin. In a previous study [Grinstead, J. S., et al. (2002) Biochemistry 41, 9946-9961], 1H NMR methods were used to correlate the effects of cryptic glycosylation outside of the PDTRPAP core epitope sequence on the recognition and binding of Mab B27.29, a monoclonal antibody raised against breast tumor cells. In the study presented here, isotope-edited NMR methods, including 15N and 13C relaxation measurements, were used to probe the recognition and binding of the PDTRPAP epitope sequence to Fab B27.29. Two peptides were studied: a one-repeat MUC1 16mer peptide of the sequence GVTSAPDTRPAPGSTA and a two-repeat MUC1 40mer peptide of the sequence (VTSAPDTRPAPGSTAPPAHG)2. 15N and 13C NMR relaxation parameters were measured for both peptides free in solution and bound to Fab B27.29. The 13CR T1 values best represent changes in the local correlation time of the peptide epitope upon binding antibody, and demonstrate that the PDTRPAP sequence is immobilized in the antibody-combining site. This result is also reflected in the appearance of the 15N- and 13C-edited HSQC spectra, where line broadening of the same peptide epitope resonances is observed. The PDTRPAP peptide epitope expands upon the peptide epitope identified previously in our group as PDTRP by homonuclear NMR experiments [Grinstead, J. S., et al. (2002) Biochemistry 41, 9946-9961], and illustrates the usefulness of the heteronuclear NMR experiments. The implications of these results are discussed within the context of MUC1 breast cancer vaccine design.

  3. Trace level detection of compounds related to the chemical weapons convention by 1H-detected 13C NMR spectroscopy executed with a sensitivity-enhanced, cryogenic probehead.

    PubMed

    Cullinan, David B; Hondrogiannis, George; Henderson, Terry J

    2008-04-15

    Two-dimensional 1H-13C HSQC (heteronuclear single quantum correlation) and fast-HMQC (heteronuclear multiple quantum correlation) pulse sequences were implemented using a sensitivity-enhanced, cryogenic probehead for detecting compounds relevant to the Chemical Weapons Convention present in complex mixtures. The resulting methods demonstrated exceptional sensitivity for detecting the analytes at trace level concentrations. 1H-13C correlations of target analytes at < or = 25 microg/mL were easily detected in a sample where the 1H solvent signal was approximately 58,000-fold more intense than the analyte 1H signals. The problem of overlapping signals typically observed in conventional 1H spectroscopy was essentially eliminated, while 1H and 13C chemical shift information could be derived quickly and simultaneously from the resulting spectra. The fast-HMQC pulse sequences generated magnitude mode spectra suitable for detailed analysis in approximately 4.5 h and can be used in experiments to efficiently screen a large number of samples. The HSQC pulse sequences, on the other hand, required roughly twice the data acquisition time to produce suitable spectra. These spectra, however, were phase-sensitive, contained considerably more resolution in both dimensions, and proved to be superior for detecting analyte 1H-13C correlations. Furthermore, a HSQC spectrum collected with a multiplicity-edited pulse sequence provided additional structural information valuable for identifying target analytes. The HSQC pulse sequences are ideal for collecting high-quality data sets with overnight acquisitions and logically follow the use of fast-HMQC pulse sequences to rapidly screen samples for potential target analytes. Use of the pulse sequences considerably improves the performance of NMR spectroscopy as a complimentary technique for the screening, identification, and validation of chemical warfare agents and other small-molecule analytes present in complex mixtures and environmental

  4. NMR characterization of sodium carboxymethyl cellulose 2: Chemical shift assignment and conformation analysis of substituent groups.

    PubMed

    Kono, Hiroyuki; Oshima, Kazuhiro; Hashimoto, Hisaho; Shimizu, Yuuichi; Tajima, Kenji

    2016-10-01

    The chemical shifts of the substituent groups of sodium carboxymethyl cellulose (CMC) were assigned by examining a series of CMC samples with different degrees of substitution. Comparative analysis of the (1)H-(13)C heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) spectra allowed the complete assignment of the substituent groups at the 2-, 3-, and 6-positions of the seven substituted monomers comprising the CMC chains, namely, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted anhydroglucose units (AGUs). In addition, the mole fractions of the monomers were determined by lineshape analysis of the carbonyl carbon resonances. The comparison between the chemical shifts of the substituents revealed strong interactions between 2- and 3-substituents in the same AGU, and showed that the steric hindrance by a substituent at the 2- or 3-position suppresses subsequent substitution at the adjacent position. PMID:27312635

  5. Dressed-bound-state molecular strong-field approximation: Application to above-threshold ionization of heteronuclear diatomic molecules

    SciTech Connect

    Hasovic, E.; Busuladzic, M.; Becker, W.; Milosevic, D. B.

    2011-12-15

    The molecular strong-field approximation (MSFA), which includes dressing of the molecular bound state, is introduced and applied to above-threshold ionization of heteronuclear diatomic molecules. Expressions for the laser-induced molecular dipole and polarizability as functions of the laser parameters (intensity and frequency) and molecular parameters [molecular orientation, dipole, and parallel and perpendicular polarizabilities of the highest occupied molecular orbital (HOMO)] are presented. Our previous MSFA theory, which incorporates the rescattering effects, is generalized from homonuclear to heteronuclear diatomic molecules. Angle- and energy-resolved high-order above-threshold ionization spectra of oriented heteronuclear diatomic molecules, exemplified by the carbon monoxide (CO) molecule, exhibit pronounced minima, which can be related to the shape of their HOMO-electron-density distribution. For the CO molecule we have found an analytical condition for the positions of these minima. We have also shown that the effect of the dressing of the HOMO is twofold: (i) the laser-induced Stark shift decreases the ionization yield and (ii) the laser-induced time-dependent dipole and polarizability change the oscillatory structure of the spectra.

  6. Measurement of hetero-nuclear distances using a symmetry-based pulse sequence in solid-state NMR.

    PubMed

    Chen, Lei; Wang, Qiang; Hu, Bingwen; Lafon, Olivier; Trébosc, Julien; Deng, Feng; Amoureux, Jean-Paul

    2010-08-28

    A Symmetry-based Resonance-Echo DOuble-Resonance (S-REDOR) method is proposed for measuring hetero-nuclear dipolar couplings between two different spin-1/2 nuclei, under fast magic-angle spinning. The hetero-nuclear dipolar couplings are restored by employing the SR4 sequence, which requires the rf-field strength to be only twice the spinning frequency. The S-REDOR experiment is extended to S-RESPDOR (Symmetry-based Resonance-Echo Saturation-Pulse DOuble-Resonance) for determining dipolar coupling between a spin-1/2 nucleus (e.g.(13)C) and (14)N. It is demonstrated that S-REDOR and S-RESPDOR methods suppress efficiently the homo-nuclear dipolar interaction of the irradiated nucleus and benefit from high robustness to the rf-field inhomogeneity, chemical shielding and dipolar truncation. Therefore, these methods allow the measurement of (13)C/(14,15)N distances, with (13)C observation, in uniformly (13)C-labeled samples. Furthermore, we provide analytical solutions for the S-REDOR and S-RESPDOR dephasing curves. These solutions facilitate the measurement of hetero-nuclear distances from experimental data. PMID:20577687

  7. Regulation of charge delocalization in a heteronuclear Fe2 ru system by a stepwise photochromic process.

    PubMed

    Xu, Guang-Tao; Li, Bin; Wang, Jin-Yun; Zhang, Dao-Bin; Chen, Zhong-Ning

    2015-02-16

    Heteronuclear complexes FeCp2 -DTE-C≡C-Ru(dppe)2 Cl (1 o; dppe=1,2-bis(diphenylphosphino)ethane, Cp=cyclopentadienyl, DTE=dithienylethene) and FeCp2-DTE-C≡C-Ru(dppe)2-C≡C-DTE-FeCp2 (2 oo), with redox-active ferrocenyl and ruthenium centers separated by a photochromic DTE moiety, were prepared to achieve photoswitchable charge delocalization and Fe⋅⋅⋅Ru electronic communication. Upon UV-light irradiation of 2 oo, the Fe⋅⋅⋅Ru heterometallic electronic interaction is increasingly facilitated with stepwise photocyclization, 2 oo→2 co→2 cc; this is ascribed to the gradual increase in π-conjugated systems. The near-infrared absorptions in mixed-valence species [2 oo](+) /[2 co](+) /[2 cc](+) are gradually intensified following the conversion of [2 oo](+) →[2 co](+) →[2 cc](+) , which demonstrates that the extent of charge delocalization shows progressive enhancement with stepwise photocyclization. As revealed by electrochemical, spectroscopic, and theoretical studies, complex 2 exhibits nine switchable states through stepwise photochromic and reversible redox processes. PMID:25640650

  8. NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning.

    PubMed

    Shmyreva, Anna A; Safdari, Majid; Furó, István; Dvinskikh, Sergey V

    2016-06-14

    Orders of magnitude decrease of (207)Pb and (199)Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. The effect is magnetic-field dependent but independent of the spinning speed in the range 200-15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time. PMID:27306000

  9. NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Shmyreva, Anna A.; Safdari, Majid; Furó, István; Dvinskikh, Sergey V.

    2016-06-01

    Orders of magnitude decrease of 207Pb and 199Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. The effect is magnetic-field dependent but independent of the spinning speed in the range 200-15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time.

  10. Structural dynamics and folding of beta-lactoglobulin probed by heteronuclear NMR.

    PubMed

    Sakurai, Kazumasa; Konuma, Tsuyoshi; Yagi, Masanori; Goto, Yuji

    2009-06-01

    Bovine beta-lactoglobulin (beta LG) has been one of the most extensively studied proteins in the history of protein science mainly because its abundance in cow's milk makes it readily available to researchers. However, compared to other textbook proteins, progress in the study of beta LG has been slow because of obstacles such as a low reversibility from denaturation linked with thiol-disulfide exchange or monomer-dimer equilibrium preventing a detailed NMR analysis. Recently, the expression of various types of recombinant beta LGs combined with heteronuclear NMR analysis has significantly improved understanding of the physico-chemical properties of beta LG. In this review, we address several topics including pH-dependent structural dynamics, ligand binding, and the complex folding mechanism with non-native intermediates. These unique properties might be brought about by conformational frustration of the beta LG structure, partly attributed to the relatively large molecular size of beta LG. We expect studies with beta LG to continue to reveal various important findings, difficult to obtain with small globular proteins, leading to a more comprehensive understanding of the conformation, dynamics and folding of proteins. PMID:19362581

  11. Observation of Resonant Effects in Ultracold Collisions between Heteronuclear Feshbach Molecules

    NASA Astrophysics Data System (ADS)

    Ye, Xin; Wang, Fudong; Zhu, Bing; Guo, Mingyang; Lu, Bo; Wang, Dajun

    2016-05-01

    Magnetic field dependent dimer-dimer collisional losses are studied with ultracold 23 Na87 Rb Feshbach molecules. By ramping the magnetic field across the 347.8 G inter-species Feshbach resonance and removing residual atoms with a magnetic field gradient, ~ 8000 pure NaRb Feshbach molecules with a temperature below 1 μK are produced. By holding the pure molecule sample in a crossed optical dipole trap and measuring the time-dependent loss curves under different magnetic fields near the Feshbach resonance, the dimer-dimer loss rates with respect to the atomic scattering length a are mapped out. We observe a resonant feature at around a = 600a0 and a rising tail at above a = 1600a0 . This behavior resembles previous theoretical works on homonuclear Feshbach molecule, where resonant effects between dimer-dimer collisions tied to tetramer bound states were predicted. Our work shows the possibility of exploring four-body physics within a heteronuclear system. We are supported by Hong Kong RGC General Research Fund no. CUHK403813.

  12. A Cross-Polarization Based Rotating-Frame Separated-Local-Field NMR Experiment Under Ultrafast MAS Conditions

    PubMed Central

    Zhang, Rongchun; Damron, Joshua; Vosegaard, Thomas

    2014-01-01

    Rotating-frame separated-local-field solid-state NMR experiments measure highly resolved heteronuclear dipolar couplings which, in turn, provide valuable interatomic distances for structural and dynamic studies of molecules in the solid-state. Though many different rotating-frame SLF sequences have been put forth, recent gains in ultrafast MAS technology have considerably simplified pulse sequence requirements due to the suppression of proton-proton dipolar interactions. In this study we revisit a simple two-dimensional 1H-13C dipolar coupling/chemical shift correlation experiment using 13C detected Cross-Polarization with a Variable Contact time (CPVC) and systematically study the conditions for its optimal performance at 60 kHz MAS. In addition, we demonstrate the feasibility of a proton-detected version of the CPVC experiment. The theoretical analysis of the CPVC pulse sequence under different Hartmann-Hahn matching conditions confirms that it performs optimally under the ZQ (w1H-w1C=±wr) condition for polarization transfer. The limits of the cross polarization process are explored and precisely defined as a function of offset and Hartmann-Hahn mismatch via spin dynamics simulation and experiments on a powder sample of uniformly 13C-labeled L-isoleucine. Our results show that the performance of the CPVC sequence and subsequent determination of 1H-13C dipolar couplings are insensitive to 1H/13C frequency offset frequency when high RF fields are used on both RF channels. Conversely, the CPVC sequence is quite sensitive to the Hartmann-Hahn mismatch, particularly for systems with weak heteronuclear dipolar couplings. We demonstrate the use of the CPVC based SLF experiment as a tool to identify different carbon groups, and hope to motivate the exploration of more sophisticated 1H detected avenues for ultrafast MAS. PMID:25486635

  13. Flexible Stoichiometry and Asymmetry of the PIDDosome Core Complex by Heteronuclear NMR Spectroscopy and Mass Spectrometry

    PubMed Central

    Nematollahi, Lily A.; Garza-Garcia, Acely; Bechara, Chérine; Esposito, Diego; Morgner, Nina; Robinson, Carol V.; Driscoll, Paul C.

    2015-01-01

    Homotypic death domain (DD)–DD interactions are important in the assembly of oligomeric signaling complexes such as the PIDDosome that acts as a platform for activation of caspase-2-dependent apoptotic signaling. The structure of the PIDDosome core complex exhibits an asymmetric three-layered arrangement containing five PIDD-DDs in one layer, five RAIDD-DDs in a second layer and an additional two RAIDD-DDs. We addressed complex formation between PIDD-DD and RAIDD-DD in solution using heteronuclear nuclear magnetic resonance (NMR) spectroscopy, nanoflow electrospray ionization mass spectrometry and size-exclusion chromatography with multi-angle light scattering. The DDs assemble into complexes displaying molecular masses in the range 130–158 kDa and RAIDD-DD:PIDD-DD stoichiometries of 5:5, 6:5 and 7:5. These data suggest that the crystal structure is representative of only the heaviest species in solution and that two RAIDD-DDs are loosely attached to the 5:5 core. Two-dimensional 1H,15N-NMR experiments exhibited signal loss upon complexation consistent with the formation of high-molecular-weight species. 13C-Methyl-transverse relaxation optimized spectroscopy measurements of the PIDDosome core exhibit signs of differential line broadening, cross-peak splitting and chemical shift heterogeneity that reflect the presence of non-equivalent sites at interfaces within an asymmetric complex. Experiments using a mutant RAIDD-DD that forms a monodisperse 5:5 complex with PIDD-DD show that the spectroscopic signature derives from the quasi- but non-exact equivalent environments of each DD. Since this characteristic was previously demonstrated for the complex between the DDs of CD95 and FADD, the NMR data for this system are consistent with the formation of a structure homologous to the PIDDosome core. PMID:25528640

  14. Heteronuclear Adiabatic Relaxation Dispersion (HARD) for quantitative analysis of conformational dynamics in proteins

    NASA Astrophysics Data System (ADS)

    Traaseth, Nathaniel J.; Chao, Fa-An; Masterson, Larry R.; Mangia, Silvia; Garwood, Michael; Michaeli, Shalom; Seelig, Burckhard; Veglia, Gianluigi

    2012-06-01

    NMR relaxation methods probe biomolecular motions over a wide range of timescales. In particular, the rotating frame spin-lock R1ρ and Carr-Purcell-Meiboom-Gill (CPMG) R2 experiments are commonly used to characterize μs to ms dynamics, which play a critical role in enzyme folding and catalysis. In an effort to complement these approaches, we introduced the Heteronuclear Adiabatic Relaxation Dispersion (HARD) method, where dispersion in rotating frame relaxation rate constants (longitudinal R1ρ and transverse R2ρ) is created by modulating the shape and duration of adiabatic full passage (AFP) pulses. Previously, we showed the ability of the HARD method to detect chemical exchange dynamics in the fast exchange regime (kex ˜ 104-105 s-1). In this article, we show the sensitivity of the HARD method to slower exchange processes by measuring R1ρ and R2ρ relaxation rates for two soluble proteins (ubiquitin and 10C RNA ligase). One advantage of the HARD method is its nominal dependence on the applied radio frequency field, which can be leveraged to modulate the dispersion in the relaxation rate constants. In addition, we also include product operator simulations to define the dynamic range of adiabatic R1ρ and R2ρ that is valid under all exchange regimes. We conclude from both experimental observations and simulations that this method is complementary to CPMG-based and rotating frame spin-lock R1ρ experiments to probe conformational exchange dynamics for biomolecules. Finally, this approach is germane to several NMR-active nuclei, where relaxation rates are frequency-offset independent.

  15. Heteronuclear cross-polarization in multinuclear multidimensional NMR: Prospects for triple-resonance CP

    SciTech Connect

    Majumdar, A.; Zuiderweg, E.R.P.

    1994-12-01

    Heteronuclear multiple-pulse-based Cross Polarization (HECP) between scalar coupled spins is gaining an important role in high-resolution multidimensional NMR of isotopically labeled biomolecules, especially in experiments involving net magnetization transfer. It has generally been observed that in these situations, the performance of HECP is superior to that of INEPT-based sequences. In particular, HECP-based three-dimensional HCCH spectroscopy is more efficient than the INEPT version of the same experiment. Differences in sensitivity have been intuitively attributed to relaxation effects and technical factors such as radiofrequency (rf) inhomogeneity We present theoretical analyses and computer simulations to probe the effects of these factors. Relaxation effects were treated phenomenologically; we found that relaxation differences are relatively small (up to 25%) between pulsed-free-precession (INEPT) and HECP-although always in favor of HECP. We explored the rf effects by employing a Gaussian distribution of rf amplitude over sample volume. We found that inhomogeneity effects significantly favor HECP over INEPT, especially under conditions of {open_quotes}matched {close_quotes} inhomogeneity in the two rf coils. The differences in favor of HECP indicate that an extension of HECP to triple resonance experiments (TRCP) in I -> S -> Q net transfers might yield better results relative to analogous INEPT-based net transfers. We theoretically analyze the possibilities of TRCP and find that transfer functions are critically dependent on the ratio J{sub IS}/J{sub SQ}. When J{sub IS} equals J{sub SQ}, we find that 100% transfer is possible for truly simultaneous TRCP and this transfer is obtained in a time 1.41 /J. The TRCP time requirement compares favorably with optimally concatenated INEPT-transfers, where net transfer I -> S -> Q is complete at 1.5 /J.

  16. Structural studies of the activation of the two component receiver domain NTRC by multidimensional heteronuclear NMR

    SciTech Connect

    Nohaile, M J

    1996-05-01

    Multidimensional heteronuclear NMR spectroscopy was used to investigate the N-terminal domain of the transcriptional enhancer NTRC (NiTrogen Regulatory protein C). This domain belongs to the family of receiver domains of two-component regulatory systems involved in signal transduction. Phosphorylation of NTRC at D54 leads to an activated form of the molecule which stimulates transcription of genes involved in nitrogen regulation. Three and four dimensional NMR techniques were used to determine an intermediate resolution structure of the unphosphorylated, inactive form of the N-terminal domain of NTRC. The structure is comprised of five {alpha}-helices and a five-stranded {beta}-sheet in a ({beta}/{alpha}){sub 5} topology. Analysis of the backbone dynamics of NTRC indicate that helix 4 and strand 5 are significantly more flexible than the rest of the secondary structure of the protein and that the loops making up the active site are flexible. The short lifetime of phospho-NTRC hampers the study of this form. However, conditions for determining the resonance assignments and, possibly, the three dimensional structure of phosphorylated NTRC have been obtained. Tentative assignments of the phosphorylated form indicate that the majority of the changes that NTRC experiences upon phosphorylation occur in helix 3, strand 4, helix 4, strand 5, and the loop between strand 5 and helix 5 (the 3445 face of NTRC) as well as near the site of phosphorylation. In order to examine a stable, activated form of the protein, constitutively active mutants of NTRC were investigated.

  17. Flexible stoichiometry and asymmetry of the PIDDosome core complex by heteronuclear NMR spectroscopy and mass spectrometry.

    PubMed

    Nematollahi, Lily A; Garza-Garcia, Acely; Bechara, Chérine; Esposito, Diego; Morgner, Nina; Robinson, Carol V; Driscoll, Paul C

    2015-02-27

    Homotypic death domain (DD)-DD interactions are important in the assembly of oligomeric signaling complexes such as the PIDDosome that acts as a platform for activation of caspase-2-dependent apoptotic signaling. The structure of the PIDDosome core complex exhibits an asymmetric three-layered arrangement containing five PIDD-DDs in one layer, five RAIDD-DDs in a second layer and an additional two RAIDD-DDs. We addressed complex formation between PIDD-DD and RAIDD-DD in solution using heteronuclear nuclear magnetic resonance (NMR) spectroscopy, nanoflow electrospray ionization mass spectrometry and size-exclusion chromatography with multi-angle light scattering. The DDs assemble into complexes displaying molecular masses in the range 130-158kDa and RAIDD-DD:PIDD-DD stoichiometries of 5:5, 6:5 and 7:5. These data suggest that the crystal structure is representative of only the heaviest species in solution and that two RAIDD-DDs are loosely attached to the 5:5 core. Two-dimensional (1)H,(15)N-NMR experiments exhibited signal loss upon complexation consistent with the formation of high-molecular-weight species. (13)C-Methyl-transverse relaxation optimized spectroscopy measurements of the PIDDosome core exhibit signs of differential line broadening, cross-peak splitting and chemical shift heterogeneity that reflect the presence of non-equivalent sites at interfaces within an asymmetric complex. Experiments using a mutant RAIDD-DD that forms a monodisperse 5:5 complex with PIDD-DD show that the spectroscopic signature derives from the quasi- but non-exact equivalent environments of each DD. Since this characteristic was previously demonstrated for the complex between the DDs of CD95 and FADD, the NMR data for this system are consistent with the formation of a structure homologous to the PIDDosome core. PMID:25528640

  18. Efficient heteronuclear decoupling in MAS solid-state NMR using non-rotor-synchronized rCW irradiation.

    PubMed

    Equbal, Asif; Paul, Subhradip; Mithu, Venus Singh; Madhu, P K; Nielsen, Niels Chr

    2014-09-01

    We present new non-rotor-synchronized variants of the recently introduced refocused continuous wave (rCW) heteronuclear decoupling method significantly improving the performance relative to the original rotor-synchronized variants. Under non-rotor-synchronized conditions the rCW decoupling sequences provide more efficient decoupling, are easier to setup, and prove more robust towards experimental parameters such as radio frequency (rf) field amplitude and spinning frequency. This is demonstrated through numerical simulations substantiated with experimental results under different sample spinning and rf field amplitude conditions for powder samples of U-(13)C-glycine and U-(13)C-L-histidine·HCl·H2O. PMID:25123538

  19. Multiple acquisition/multiple observation separated local field/chemical shift correlation solid-state magic angle spinning NMR spectroscopy.

    PubMed

    Das, Bibhuti B; Opella, Stanley J

    2014-08-01

    Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies. PMID:25023566

  20. Multiple Acquisition/Multiple Observation Separated Local Field/Chemical Shift Correlation Solid-state Magic Angle Spinning NMR Spectroscopy

    PubMed Central

    Das, Bibhuti B.; Opella, Stanley J.

    2014-01-01

    Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies. PMID:25023566

  1. Z and E rotamers of N-formyl-1-bromo-4-hydroxy-3-methoxymorphinan-6-one and their interconversion as studied by 1H/13C NMR spectroscopy and quantum chemical calculations

    PubMed Central

    Sulima, Agnieszka; Cheng, Kejun; Jacobson, Arthur E.; Rice, Kenner C.; Gawrisch, Klaus; Lee, Yong-Sok

    2012-01-01

    N-Formyl-1-bromo-4-hydroxy-3-methoxymorphinan-6-one (2), an important intermediate in the NIH Opiate Total Synthesis, presumably exists as a mixture of two rotamers (Z and E) in both CHCl3 and DMSO at room temperature due to the hindered rotation of its N-C18 bond in the amide moiety. By comparing the experimental 1H and 13C chemical shifts of a single rotamer and the mixture of 2 in CDCl3 with the calculated chemical shifts of the geometry optimized Z and E rotamers utilizing density functional theory, the crystalline rotamer of 2 was characterized as having the E configuration. The energy barrier between the two rotamers was also determined with the temperature dependence of 1H and 13C NMR coalescence experiments, and then compared with that from the reaction path for the interconversion of the two rotamers calculated at the level of B3LYP/6-31G*. Detailed geometry of the ground state and the transition states of both rotamers are given and discussed. PMID:23233124

  2. Spectroscopic (FT-IR, (1)H, (13)C NMR and UV-vis) characterization and DFT studies of novel 8-((4-(methylthio)-2,5-diphenylfuran-3-yl)methoxy)quinoline.

    PubMed

    Diwaker; Chidan Kumar, C S; Kumar, Ashwani; Chandraju, Siddegowda

    2015-11-01

    In this study, computational calculations of a new quinoline derivative: 8-((4-(methylthio)-2,5-diphenylfuran-3-yl)methoxy)quinoline is carried out using ab initio methods. The geometry optimization as well as fundamental frequencies of the most stable configuration of the title compound is reported. A detailed study of Infrared spectrum, chemical shifts and electronic spectrum of the title compound is also presented. The Gauge-Invariant Atomic Orbital approach is used to calculate the proton and carbon chemical shifts of the title compound. The natural bond orbital analysis of the title compound is also reported in order to understand the stability of the molecule which arises from hyper conjugative interactions and charge delocalization. The theoretical electronic absorption spectrum is also reported using the time dependent density functional approach. The molecular structure along with vibrational frequencies as simulated for binding of iron with the title compound is also reported using ab initio methods. PMID:26079516

  3. Comprehensive quantum chemical and spectroscopic (FTIR, FT-Raman, 1H, 13C NMR) investigations of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane

    NASA Astrophysics Data System (ADS)

    Arjunan, V.; Anitha, R.; Devi, L.; Mohan, S.; Yang, Haifeng

    2015-01-01

    Aromatic epoxides are causative factors for mutagenic and carcinogenic activity of polycyclic arenes. The 1,2- or 2,3-epoxy compounds are widely used to a considerable extent in the textile, plastics, pharmaceutical, cosmetics, detergent and photochemical industries. The FTIR and FT-Raman spectra of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane are recorded in the regions 4000-400 cm-1 and 4000-100 cm-1, respectively. The observed fundamentals are assigned to different normal modes of vibration. The structure of the compound has been optimised with B3LYP method using 6-311++G** and cc-pVTZ basis sets. The IR and Raman intensities are determined. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/6-311++G(d,p) method to display electrostatic potential (electron + nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of the compounds has been performed to indicate the presence of intramolecular charge transfer. The 1H and 13C NMR chemical shifts of the molecules have been analysed.

  4. 1H, 13C NMR, FT-IR, ESI MS and PM5 studies of a new 3,6,9-trioxadecylamide of monensin A and its complexes with Li +, Na + and K + cations

    NASA Astrophysics Data System (ADS)

    Łowicki, Daniel; Huczyński, Adam; Brzezinski, Bogumil; Bartl, Franz

    2011-03-01

    A new 3,6,9-trioxadecylamide of monensin A (M-AM4) has been synthesised and its ability to form complexes with Li +, Na + and K + cations has been studied by ESI mass spectrometry, 1H and 13C NMR, FT-IR spectroscopy and PM5 semiempirical method. The ESI MS data indicate that M-AM4 forms complexes with Li +, Na + and K + of exclusively 1:1 stoichiometry which are stable up to cv = 70 V. The formation of the M-AM4-Na + is strongly favoured. Above cv = 70 the fragmentation process is observed. The spectroscopic studies show that the structures of the M-AM4 and its complexes with the cations of 1:1 stoichiometry are stabilized by intramolecular hydrogen bonds in which the OH groups are always involved. The C dbnd O amide group is engaged in the complexation process of each cation. The M-AM4-K + complex can also assume a structure in which the C dbnd O amide group does not participate in the complexation but the complexes of such structure do not dominate.

  5. Comprehensive quantum chemical and spectroscopic (FTIR, FT-Raman, (1)H, (13)C NMR) investigations of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane.

    PubMed

    Arjunan, V; Anitha, R; Devi, L; Mohan, S; Yang, Haifeng

    2015-01-25

    Aromatic epoxides are causative factors for mutagenic and carcinogenic activity of polycyclic arenes. The 1,2- or 2,3-epoxy compounds are widely used to a considerable extent in the textile, plastics, pharmaceutical, cosmetics, detergent and photochemical industries. The FTIR and FT-Raman spectra of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane are recorded in the regions 4000-400 cm(-1) and 4000-100 cm(-1), respectively. The observed fundamentals are assigned to different normal modes of vibration. The structure of the compound has been optimised with B3LYP method using 6-311++G(**) and cc-pVTZ basis sets. The IR and Raman intensities are determined. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/6-311++G(d,p) method to display electrostatic potential (electron+nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of the compounds has been performed to indicate the presence of intramolecular charge transfer. The (1)H and (13)C NMR chemical shifts of the molecules have been analysed. PMID:25062058

  6. Spectroscopic (FT-IR, FT-Raman, 1H, 13C NMR, UV/VIS), thermogravimetric and antimicrobial studies of Ca(II), Mn(II), Cu(II), Zn(II) and Cd(II) complexes of ferulic acid

    NASA Astrophysics Data System (ADS)

    Kalinowska, M.; Piekut, J.; Bruss, A.; Follet, C.; Sienkiewicz-Gromiuk, J.; Świsłocka, R.; Rzączyńska, Z.; Lewandowski, W.

    2014-03-01

    The molecular structure of Mn(II), Cu(II), Zn(II), Cd(II) and Ca(II) ferulates (4-hydroxy-3-methoxycinnamates) was studied. The selected metal ferulates were synthesized. Their composition was established by means of elementary and thermogravimetric analysis. The following spectroscopic methods were used: infrared (FT-IR), Raman (FT-Raman), nuclear magnetic resonance (13C, 1H NMR) and ultraviolet-visible (UV/VIS). On the basis of obtained results the electronic charge distribution in studied metal complexes in comparison with ferulic acid molecule was discussed. The microbiological study of ferulic acid and ferulates toward Escherichia coli, Bacillus subtilis, Candida albicans, Pseudomonas aeruginosa, Staphylococcus aureus and Proteus vulgaris was done.

  7. (1)H, (13)C, and (15)N backbone resonance assignments of the full-length 40 kDa S. acidocaldarius Y-family DNA polymerase, dinB homolog.

    PubMed

    Moro, Sean L; Cocco, Melanie J

    2015-10-01

    The dinB homolog (Dbh) is a member of the Y-family of translesion DNA polymerases, which are specialized to accurately replicate DNA across from a wide variety of lesions in living cells. Lesioned bases block the progression of high-fidelity polymerases and cause detrimental replication fork stalling; Y-family polymerases can bypass these lesions. The active site of the translesion synthesis polymerase is more open than that of a replicative polymerase; consequently Dbh polymerizes with low fidelity. Bypass polymerases also have low processivity. Short extension past the lesion allows the high-fidelity polymerase to switch back onto the site of replication. Dbh and the other Y-family polymerases have been used as structural models to investigate the mechanisms of DNA polymerization and lesion bypass. Many high-resolution crystal structures of Y-family polymerases have been reported. NMR dynamics studies can complement these structures by providing a measure of protein motions. Here we report the (15)N, (1)H, and (13)C backbone resonance assignments at two temperatures (35 and 50 °C) for Sulfolobus acidocaldarius Dbh polymerase. Backbone resonance assignments have been obtained for 86 % of the residues. The polymerase active site is assigned as well as the majority of residues in each of the four domains. PMID:26154586

  8. Homonuclear and Heteronuclear NMR Studies of a Statherin Fragment Bound to Hydroxyapatite Crystals

    SciTech Connect

    Raghunathan, Vinodhkumar; Gibson, James M.; Goobes, Gil; Popham, Jennifer M.; Louie, Elizabeth; Stayton, Patrick; Drobny, Gary P.

    2006-05-11

    Acidic proteins found in mineralized tissues act as nature's crystal engineers, where they play a key role in promoting or inhibiting the growth of minerals such as hydroxyapatite (HAP), Ca10(PO4)6(OH)2, the main mineral component of bone and teeth. Key to understanding the structural basis of protein-crystal recognition and protein control of hard tissue growth is the nature of interactions between the protein side chains and the crystal surface. In an earlier work we have measured the proximity of the lysine (K6) side chain in an SN-15 peptide fragment of the salivary protein statherin adsorbed to the Phosphorus-rich surface of HAP using solid-state NMR recoupling experiments. 15N(31P) rotational echo double resonance (REDOR) NMR data on the side-chain nitrogen in K6 gave rise to three different models of protein-surface interaction to explain the experimental data acquired. In this work we extend the analysis of the REDOR data by examining the contribution of interactions between surface phosphorus atoms to the observed 15N REDOR decay. We performed 31P-31P recoupling experiments in HAP and (NH4)2HPO4 (DHP) to explore the nature of dipolar coupled 31P spin networks. These studies indicate that extensive networks of dipolar coupled 31P spins can be represented as stronger effective dipolar couplings, the existence of which must be included in the analysis of REDOR data. We carried out 15N(31P) REDOR in the case of DHP to determine how the size of the dephasing spin network influences the interpretation of the REDOR data. Although use of an extended 31P coupled spin network simulates the REDOR data well, a simplified 31P dephasing system composed of two spins with a larger dipolar coupling also simulates the REDOR data and only perturbs the heteronuclear couplings very slightly. The 31P-31P dipolar couplings between phosphorus nuclei in HAP can be replaced by an effective dipolar interaction of 600 Hz between two 31P spins. We incorporated this coupling and

  9. Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR.

    PubMed

    Basse, Kristoffer; Shankar, Ravi; Bjerring, Morten; Vosegaard, Thomas; Nielsen, Niels Chr; Nielsen, Anders B

    2016-09-01

    We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization ((RESPIRATION)CP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer. In this description, it becomes transparent that the main attribute leading to non-ideal performance is a fictitious field along the rf field axis, which is generated from second-order cross terms arising mainly between chemical shift tensors and themselves. This insight is useful for the development of improved recoupling experiments. We discuss the validity of this approach and present quaternion calculations to determine the effective resonance conditions in a combined rf field and chemical shift offset interaction frame transformation. Based on this, we derive a broad-banded version of the (RESPIRATION)CP experiment. The new sequence is experimentally verified using SNNFGAILSS amyloid fibrils where simultaneous (15)N → (13)CO and (15)N → (13)Cα coherence transfer is demonstrated on high-field NMR instrumentation, requiring great offset stability. PMID:27608995

  10. Matter-wave solitons in heteronuclear atomic Bose-Einstein condensates with synchronously controllable interactions and potentials

    SciTech Connect

    Ding, Cai-Ying; Zhang, Xiao-Fei; Liu, W. M.; Zhao, Dun; Luo, Hong-Gang

    2011-11-15

    We investigate exact matter-wave soliton pairs of two-component heteronuclear atomic Bose-Einstein condensates with tunable interactions and harmonic potentials by using a combination of the homogeneous balance principle and the F-expansion technique. Our results show that exact matter-wave soliton pairs are asymmetric where their existence requires some restrictive conditions corresponding to experimentally controllable interactions and harmonic potential parameters. In contrast to homonuclear systems, the potentials for two components in heteronuclear systems are different, which is due to the mass of two components being unequal. Considering two explicit situations of the interaction parameters, we further explore the collision dynamics of the soliton pairs with opposite velocities by synchronously controlling the interaction and potential parameters. The collision dynamics occur during and after the simultaneous evaporative cooling of two condensates. The results show that collisions are elastic and that the solitons after the collision can keep their identities. In addition, we find that the amplitudes of the soliton pairs periodically grow with time during the cooling process and, for the same initial conditions, the collision time of the soliton pair without gain is delayed compared with that with gain. We also discuss how to observe these new phenomena in future experiments.

  11. IPAP-HSQMBC: measurement of long-range heteronuclear coupling constants from spin-state selective multiplets.

    PubMed

    Gil, Sergi; Espinosa, Juan Félix; Parella, Teodor

    2010-12-01

    A new NMR approach is proposed for the measurement of long-range heteronuclear coupling constants ((n)J(XH), n>1) in natural abundance molecules. Two complementary in-phase (IP) and anti-phase (AP) data are separately recorded from a modified HSQMBC experiment and then added/subtracted to provide spin-state-selective α/β-HSQMBC spectra. The magnitude of (n)J(XH) can be directly determined by simple analysis of the relative displacement between α- and β-cross-peaks. The robustness of this IPAP-HSQMBC experiment is evaluated experimentally and by simulation using a variety of different conditions. Important aspects such as signal intensity dependence and presence of unwanted cross-talk effects are discussed and examples on the measurement of small proton-carbon ((n)J(CH)) and proton-nitrogen ((n)J(NH)) coupling constants are provided. PMID:20952232

  12. Electron spin density on the axial His ligand of high-spin and low-spin Nitrophorin 2 probed by heteronuclear NMR spectroscopy

    PubMed Central

    Abriata, Luciano A.; Zaballa, María-Eugenia; Berry, Robert E.; Yang, Fei; Zhang, Hongjun; Walker, F. Ann; Vila, Alejandro J.

    2013-01-01

    The electronic structure of heme proteins is exquisitely tuned by the interaction of the iron center with the axial ligands. NMR studies of paramagnetic heme systems have been focused on the heme signals, but signals from the axial ligands have been rather difficult to detect and assign. We report an extensive assignment of the 1H, 13C and 15N resonances of the axial His ligand in the NO-carrying protein nitrophorin 2 (NP2) in the paramagnetic high-spin and low-spin forms, as well as in the diamagnetic NO complex. We find that the high-spin protein has σ spin delocalization to all atoms in the axial His57, which decreases in size as the number of bonds between Fe(III) and the atom in question increase, except that within the His57 imidazole ring the contact shifts are a balance between positive σ and negative π contributions. In contrast, the low-spin protein has π spin delocalization to all atoms of the imidazole ring. Our strategy, adequately combined with a selective residue labeling scheme, represents a straightforward characterization of the electron spin density in heme axial ligands. PMID:23327568

  13. Correlation consistent basis sets for the atoms In–Xe

    SciTech Connect

    Mahler, Andrew; Wilson, Angela K.

    2015-02-28

    In this work, the correlation consistent family of Gaussian basis sets has been expanded to include all-electron basis sets for In–Xe. The methodology for developing these basis sets is described, and several examples of the performance and utility of the new sets have been provided. Dissociation energies and bond lengths for both homonuclear and heteronuclear diatomics demonstrate the systematic convergence behavior with respect to increasing basis set quality expected by the family of correlation consistent basis sets in describing molecular properties. Comparison with recently developed correlation consistent sets designed for use with the Douglas-Kroll Hamiltonian is provided.

  14. Comprehensive description of NMR cross-correlated relaxation under anisotropic molecular tumbling and correlated local dynamics on all time scales

    NASA Astrophysics Data System (ADS)

    Vögeli, Beat

    2010-07-01

    A simple general expression for the NMR cross-correlated relaxation rate under anisotropic molecular tumbling is presented for globular proteins. The derivation includes effects of fast and slow motion of the interaction tensors and correlation between them. Expressions suitable for practical analysis are tailored in dependence of standard order parameters of the individual interactions. It is shown that these order parameters must be sensitive to slow motion (slower than molecular tumbling) for detection of slow correlated motion. Such order parameters are those obtained from residual dipolar couplings but not those obtained from T1, T2, and heteronuclear Nuclear Overhauser Enhancement measurements.

  15. Fluorine detected 2D NMR experiments for the practical determination of size and sign of homonuclear F-F and heteronuclear C-F multiple bond J-coupling constants in multiple fluorinated compounds

    NASA Astrophysics Data System (ADS)

    Aspers, Ruud L. E. G.; Ampt, Kirsten A. M.; Dvortsak, Peter; Jaeger, Martin; Wijmenga, Sybren S.

    2013-06-01

    The use of fluorine in molecules obtained from chemical synthesis has become increasingly important within the pharmaceutical and agricultural industry. NMR characterization of these compounds is of great value with respect to their structure elucidation, their screening in metabolomics investigations and binding studies. The favorable NMR properties of the fluorine nucleus make NMR with fluorine detection of great value in this respect. A suite of NMR 2D F-F- and F-C-correlation experiments with fluorine detection was applied to the assignment of resonances, nJCF- and nJFF-couplings as well as the determination of their size and sign. The utilization of this experiment suite was exemplarily demonstrated for a highly fluorinated vinyl alkyl ether. Especially F-C HSQC and J-scaled F-C HMBC experiments allowed determining the size of the J-couplings of this compound. The relative sign of its homo- and heteronuclear couplings was achieved by different combinations of 2D NMR experiments, including non-selective and F2-selective F-C XLOC, F2-selective F-C HMQC, and F-F COSY. The F2-one/two-site selective F-C XLOC versions were found highly useful, as they led to simplifications of the common E.COSY patterns and resulted in a higher confidence level of the assignment by using selective excitation. The combination of F2-one/two-site selective F-C XLOC experiments with a F2-one-site selective F-C HMQC experiment provided the signs of all nJCF- and nJFF-couplings in the vinyl moiety of the test compound. Other combinations of experiments were found useful as well for special purposes when focusing for example on homonuclear couplings a combination of F-F COSY-10 with a F2-one-site selective F-C HMQC could be used. The E.COSY patterns in the spectra demonstrated were analyzed by use of the spin-selective displacement vectors, and in case of the XLOC also by use of the DQ- and ZQ-displacement vectors. The variety of experiments presented shall contribute to facilitate the

  16. Structural studies of a polysaccharide from Vibrio parahaemolyticus strain AN-16000.

    PubMed

    Fontana, Carolina; Zaccheus, Mona; Weintraub, Andrej; Ansaruzzaman, Mohammad; Widmalm, Göran

    2016-09-01

    The structure of a polysaccharide from Vibrio parahaemolyticus strain AN-16000 has been investigated. The sugar and absolute configuration analysis revealed d-Glc, d-GalN, d-QuiN and l-FucN as major components. The PS was subjected to dephosphorylation with aqueous 40% HF to obtain an oligosaccharide that was analyzed by (1)H and (13)C NMR spectroscopy. The HR-MS spectrum of the oligosaccharide revealed a pentasaccharide composed of two Glc residues, one QuiNAc and one GalNAc, one FucNAc, as well as a glycerol moiety. The structure of the PS was determined using (1)H, (13)C, (15)N and (31)P NMR spectroscopy; inter-residue correlations were identified by (1)H,(13)C-heteronuclear multiple-bond correlation, (1)H,(1)H-NOESY and (1)H,(31)P-hetero-TOCSY experiments. The PS backbone has the following teichoic acid-like structure: →3)-d-Gro-(1-P-6)-β-d-Glcp-(1→4)-α-l-FucpNAc-(1→3)-β-d-QuipNAc-(1→ with a side-chain consisting of α-d-Glcp-(1→6)-α-d-GalpNAc-(1→ linked to the O3 position of the FucNAc residue. PMID:27392309

  17. Multi-Spectroscopic Analysis of Seed Quality and 13C-Stable-Iotopologue Monitoring in Initial Growth Metabolism of Jatropha curcas L.

    PubMed Central

    Komatsu, Takanori; Ohishi, Risa; Shino, Amiu; Akashi, Kinya; Kikuchi, Jun

    2014-01-01

    In the present study, we applied nuclear magnetic resonance (NMR), as well as near-infrared (NIR) spectroscopy, to Jatropha curcas to fulfill two objectives: (1) to qualitatively examine the seeds stored at different conditions, and (2) to monitor the metabolism of J. curcas during its initial growth stage under stable-isotope-labeling condition (until 15 days after seeding). NIR spectra could non-invasively distinguish differences in storage conditions. NMR metabolic analysis of water-soluble metabolites identified sucrose and raffinose family oligosaccharides as positive markers and gluconic acid as a negative marker of seed germination. Isotopic labeling patteren of metabolites in germinated seedlings cultured in agar-plate containg 13C-glucose and 15N-nitrate was analyzed by zero-quantum-filtered-total correlation spectroscopy (ZQF-TOCSY) and 13C-detected 1H-13C heteronuclear correlation spectroscopy (HETCOR). 13C-detected HETOCR with 13C-optimized cryogenic probe provided high-resolution 13C-NMR spectra of each metabolite in molecular crowd. The 13C-13C/12C bondmer estimated from 1H-13C HETCOR spectra indicated that glutamine and arginine were the major organic compounds for nitrogen and carbon transfer from roots to leaves. PMID:25401292

  18. Profiling planktonic biomass using element-specific, multicomponent nuclear magnetic resonance spectroscopy.

    PubMed

    Komatsu, Takanori; Kobayashi, Toshiya; Hatanaka, Minoru; Kikuchi, Jun

    2015-06-01

    Planktonic metabolism plays crucial roles in Earth's elemental cycles. Chemical speciation as well as elemental stoichiometry is important for advancing our understanding of planktonic roles in biogeochemical cycles. In this study, a multicomponent solid-state nuclear magnetic resonance (NMR) approach is proposed for chemical speciation of cellular components, using several advanced NMR techniques. Measurements by ssNMR were performed on (13)C and (15)N-labeled Euglena gracilis, a flagellated protist. 3D dipolar-assisted rotational resonance, double-cross-polarization (1)H-(13)C correlation spectroscopy, and (1)H-(13)C solid-state heteronuclear single quantum correlation spectroscopy successively allowed characterization of cellular components. These techniques were then applied to E. gracilis cultured in high and low ammonium media to demonstrate the power of this method for profiling and comparing cellular components. Cellular NMR spectra indicated that ammonium induced both paramylon degradation and amination. Arginine was stored as a nitrogen reserve and ammonium replaced by arginine catabolism via the arginine dihydrolase pathway. (15)N and (31)P cellular ssNMR indicated arginine and polyphosphate accumulation in E. gracilis, respectively. This chemical speciation technique will contribute to environmental research by providing detailed information on environmental chemical properties. PMID:25973714

  19. Relative merits of rCWA and XiX heteronuclear spin decoupling in solid-state magic-angle-spinning NMR spectroscopy: A bimodal Floquet analysis

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Leskes, Michal; Nielsen, Niels Chr.; Madhu, P. K.; Vega, Shimon

    2016-02-01

    We present a bimodal Floquet analysis of the recently introduced refocused continuous wave (rCW) solid-state NMR heteronuclear dipolar decoupling method and compare it with the similar looking X-inverse X (XiX) scheme. The description is formulated in the rf interaction frame and is valid for both finite and ideal π pulse rCW irradiation that forms the refocusing element in the rCW scheme. The effective heteronuclear dipolar coupling Hamiltonian up to first order is described. The analysis delineates the difference between the two sequences to different orders of their Hamiltonians for both diagonal and off-diagonal parts. All the resonance conditions observed in experiments and simulations have been characterised and their influence on residual line broadening is highlighted. The theoretical comparison substantiates the numerical simulations and experimental results to a large extent.

  20. Isotope-detected 1H NMR studies of proteins: a general strategy for editing interproton nuclear Overhauser effects by heteronuclear decoupling, with application to phage lambda repressor.

    PubMed Central

    Weiss, M A; Redfield, A G; Griffey, R H

    1986-01-01

    A strategy for editing interproton nuclear Overhauser effects (NOEs) in proteins is proposed and illustrated. Selective incorporation of 13C- (or 15N)-labeled amino acids into a protein permits NOEs involving the labeled residues to be identified by heteronuclear difference decoupling. Such heteronuclear editing simplifies the NOE difference spectrum and avoids ambiguities due to spin diffusion. Isotope-detected 1H NMR thus opens to study proteins too large for conventional one- and two-dimensional NMR methods (20-75 kDa). We have applied this strategy to the N-terminal domain of phage lambda repressor, a protein of dimer molecular mass 23 kDa. A tertiary NOE from an internal aromatic ring (Phe-51) to a beta-13C-labeled alanine residue (Ala-62) is demonstrated. PMID:3006046

  1. Na/Ca Intermixing around Silicate and Phosphate Groups in Bioactive Phosphosilicate Glasses Revealed by Heteronuclear Solid-State NMR and Molecular Dynamics Simulations.

    PubMed

    Mathew, Renny; Stevensson, Baltzar; Edén, Mattias

    2015-04-30

    We characterize the intermixing of network-modifying Na(+)/Ca(2+) ions around the silicate (QSi(n)) and phosphate (QP(n)) tetrahedra in a series of 16 Na2O–CaO–SiO2–P2O5 glasses, whose P content and silicate network connectivity were varied independently. The set includes both bioactive and bioinactive compositions and also encompasses two soda-lime-silicate members devoid of P, as well as two CaO–SiO2 glasses and one Na2O–SiO2–P2O5 glass. The various Si/P↔Na/Ca contacts were probed by molecular dynamics (MD) simulations together with heteronuclear magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experimentation utilizing (23)Na{(31)P} and (23)Na{(29)Si} REDOR, as well as (31)P{ (23)Na} and (29)Si{(23)Na} REAPDOR. We introduce an approach for quantifying the extent of Na(+)/Ca(2+) ordering around a given QP(n) or QSi(n) group, encoded by the preference factor 0⩽ PM ⩽ 1 conveying the relative weights of a random cation intermixing (PM = 0) and complete preference/ordering (PM = 1) for one of the species M, which represents either Na(+) or Ca(2+). The MD-derived preference factors reveal phosphate and silicate species surrounded by Na(+)/Ca(2+) ions intermixed nearly randomly (PM ≲ 0.15), except for the QSi(4) and QSi(1) groups, which manifest more significant cation ordering with preference for Na+ and Ca2+, respectively. The overall weak preferences are essentially independent of the Si and P contents of the glass, whereas PM primarily correlates with the total amount of network modifiers: as the latter is increased, the Na/Ca distribution around the {QP(0), QSi(1), QSi(2)} groups with preference for Ca2(+ )tend to randomize (i.e., PCa decreases), while the PNa-values grow slightly for the {QP(1), QSi(3), QSi(4)} species already preferring coordination of Na. The set of experimental preference factors {PCa} for the orthophosphate (QP(0)) groups extracted from (31)P{(23)Na} REAPDOR NMR-derived M2(P–Na) dipolar second moments agrees

  2. Pf1 bacteriophage hydration by magic angle spinning solid-state NMR

    NASA Astrophysics Data System (ADS)

    Sergeyev, Ivan V.; Bahri, Salima; Day, Loren A.; McDermott, Ann E.

    2014-12-01

    High resolution two- and three-dimensional heteronuclear correlation spectroscopy (1H-13C, 1H-15N, and 1H-13C-13C HETCOR) has provided a detailed characterization of the internal and external hydration water of the Pf1 virion. This long and slender virion (2000 nm × 7 nm) contains highly stretched DNA within a capsid of small protein subunits, each only 46 amino acid residues. HETCOR cross-peaks have been unambiguously assigned to 25 amino acids, including most external residues 1-21 as well as residues 39-40 and 43-46 deep inside the virion. In addition, the deoxyribose rings of the DNA near the virion axis are in contact with water. The sets of cross-peaks to the DNA and to all 25 amino acid residues were from the same hydration water 1H resonance; some of the assigned residues do not have exchangeable side-chain protons. A mapping of the contacts onto structural models indicates the presence of water "tunnels" through a highly hydrophobic region of the capsid. The present results significantly extend and modify results from a lower resolution study, and yield a comprehensive hydration surface map of Pf1. In addition, the internal water could be distinguished from external hydration water by means of paramagnetic relaxation enhancement. The internal water population may serve as a conveniently localized magnetization reservoir for structural studies.

  3. Simple, efficient protocol for enzymatic synthesis of uniformly 13C, 15N-labeled DNA for heteronuclear NMR studies.

    PubMed Central

    Masse, J E; Bortmann, P; Dieckmann, T; Feigon, J

    1998-01-01

    The use of uniformly 13C,15N-labeled RNA has greatly facilitated structural studies of RNA oligonucleotides by NMR. Application of similar methodologies for the study of DNA has been limited, primarily due to the lack of adequate methods for sample preparation. Methods for both chemical and enzymatic synthesis of DNA oligonucleotides uniformly labeled with 13C and/or 15N have been published, but have not yet been widely used. We have developed a modified procedure for preparing uniformly 13C,15N-labeled DNA based on enzymatic synthesis using Taq DNA polymerase. The highly efficient protocol results in quantitative polymerization of the template and approximately 80% incorporation of the labeled dNTPs. Procedures for avoiding non-templated addition of nucleotides or for their removal are given. The method has been used to synthesize several DNA oligonucleotides, including two complementary 15 base strands, a 32 base DNA oligonucleotide that folds to form an intramolecular triplex and a 12 base oligonucleotide that dimerizes and folds to form a quadruplex. Heteronuclear NMR spectra of the samples illustrate the quality of the labeled DNA obtained by these procedures. PMID:9592146

  4. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems.

    PubMed

    Baranowski, M; Woźniak-Braszak, A; Jurga, K

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2MHz and 28.411MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins (1)H are polarized in the magnetic field B0 while fluorine spins (19)F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal. PMID:26705906

  5. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems

    NASA Astrophysics Data System (ADS)

    Baranowski, M.; Woźniak-Braszak, A.; Jurga, K.

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2 MHz and 28.411 MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins 1H are polarized in the magnetic field B0 while fluorine spins 19F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal.

  6. Interaction of yeast iso-1-cytochrome c with cytochrome c peroxidase investigated by [15N, 1H] heteronuclear NMR spectroscopy.

    PubMed

    Worrall, J A; Kolczak, U; Canters, G W; Ubbink, M

    2001-06-19

    The interaction of yeast iso-1-cytochrome c with its physiological redox partner cytochrome c peroxidase has been investigated using heteronuclear NMR techniques. Chemical shift perturbations for both 15N and 1H nuclei arising from the interaction of isotopically enriched 15N cytochrome c with cytochrome c peroxidase have been observed. For the diamagnetic, ferrous cytochrome c, 34 amides are affected by binding, corresponding to residues at the front face of the protein and in agreement with the interface observed in the 1:1 crystal structure of the complex. In contrast, for the paramagnetic, ferric protein, 56 amides are affected, corresponding to residues both at the front and toward the rear of the protein. In addition, the chemical shift perturbations were larger for the ferric protein. Using experimentally observed pseudocontact shifts the magnetic susceptibility tensor of yeast iso-1-cytochrome c in both the free and bound forms has been calculated with HN nuclei as inputs. In contrast to an earlier study, the results indicate that there is no change in the geometry of the magnetic axes for cytochrome c upon binding to cytochrome c peroxidase. This leads us to conclude that the additional effects observed for the ferric protein arise either from a difference in binding mode or from the more flexible overall structure causing a transmittance effect upon binding. PMID:11401551

  7. Synthesis, crystal structures and Hirshfeld surface analyses of two new Salen type nickel/sodium heteronuclear complexes

    NASA Astrophysics Data System (ADS)

    Mahlooji, Niloofar; Behzad, Mahdi; Tarahhomi, Atekeh; Maroney, Michael; Rudbari, Hadi Amiri; Bruno, Giuseppe; Ghanbari, Bahram

    2016-04-01

    Two new heteronuclear Nickel(II)/Sodium(I) complexes of a side-off compartmental Schiff base ligand were synthesized and characterized by spectroscopic methods. Crystal structures of both of the complexes were also obtained. The Schiff base ligand was synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with 2-hydroxy-3-methoxybenzaldehyde. In both of the complexes the Ni(II) ion is coordinated to the inner N2O2 coordination sphere with square-planar geometry and the Na(I) ion is coordinated to the outer O2O2‧ coordination sphere. In Complex (1) with general formula [Ni(L)Na(CH3OH)(ClO4)] the sodium ion is seven coordinated while in (2) with general formula [{Ni(L)Na(OH2)}2(μ-Ni(CN)4)] the sodium ion is six coordinated. Intermolecular interactions in two studied complexes were analyzed using 3D Hirshfeld surfaces and corresponding 2D fingerprint plots. This analysis showed that the H … H and C … H/H … C contacts for both structures (altogether 67.5% of total Hirshfeld surface area for (1) and 77.6% for (2)) and the O … H/H … O (24.2%) for (1) and the N … H/H … N (8.1%) contacts for (2) were the characteristic intermolecular contacts in the related crystal structures.

  8. Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls MNi(CO)3 (-) (M = Mg, Ca, Al).

    PubMed

    Xie, Hua; Zou, Jinghan; Yuan, Qinqin; Fan, Hongjun; Tang, Zichao; Jiang, Ling

    2016-03-28

    The heteronuclear metal carbonyl anions MNi(CO)3 (-) (M = Mg, Ca, Al) have been investigated using photoelectron velocity-map imaging spectroscopy. Electron affinities of neutral MNi(CO)3 (M = Mg, Ca, Al) are measured from the photoelectron spectra to be 1.064 ± 0.063, 1.050 ± 0.064, and 1.541 ± 0.040 eV, respectively. The C-O stretching mode in these three clusters is observed and the vibrational frequency is determined to be 2049, 2000, and 2041 cm(-1) for MgNi(CO)3, CaNi(CO)3, and AlNi(CO)3, respectively. Density functional theory calculations are carried out to elucidate the geometric and electronic structures and to aid the experimental assignments. It has been found that three terminal carbonyls are preferentially bonded to the nickel atom in these heterobinuclear nickel carbonyls MNi(CO)3 (-1/0), resulting in the formation of the Ni(CO)3 motif. Ni remains the 18-electron configuration for MgNi(CO)3 and CaNi(CO)3 neutrals, but not for AlNi(CO)3. This is different from the homobinuclear nickel carbonyl Ni-Ni(CO)3 with the involvement of three bridging ligands. Present findings would be helpful for understanding CO adsorption on alloy surfaces. PMID:27036444

  9. Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls MNi(CO)3- (M = Mg, Ca, Al)

    NASA Astrophysics Data System (ADS)

    Xie, Hua; Zou, Jinghan; Yuan, Qinqin; Fan, Hongjun; Tang, Zichao; Jiang, Ling

    2016-03-01

    The heteronuclear metal carbonyl anions MNi(CO)3- (M = Mg, Ca, Al) have been investigated using photoelectron velocity-map imaging spectroscopy. Electron affinities of neutral MNi(CO)3 (M = Mg, Ca, Al) are measured from the photoelectron spectra to be 1.064 ± 0.063, 1.050 ± 0.064, and 1.541 ± 0.040 eV, respectively. The C-O stretching mode in these three clusters is observed and the vibrational frequency is determined to be 2049, 2000, and 2041 cm-1 for MgNi(CO)3, CaNi(CO)3, and AlNi(CO)3, respectively. Density functional theory calculations are carried out to elucidate the geometric and electronic structures and to aid the experimental assignments. It has been found that three terminal carbonyls are preferentially bonded to the nickel atom in these heterobinuclear nickel carbonyls MNi(CO)3-1/0, resulting in the formation of the Ni(CO)3 motif. Ni remains the 18-electron configuration for MgNi(CO)3 and CaNi(CO)3 neutrals, but not for AlNi(CO)3. This is different from the homobinuclear nickel carbonyl Ni-Ni(CO)3 with the involvement of three bridging ligands. Present findings would be helpful for understanding CO adsorption on alloy surfaces.

  10. Broadband cross-polarization-based heteronuclear dipolar recoupling for structural and dynamic NMR studies of rigid and soft solids.

    PubMed

    Kharkov, B B; Chizhik, V I; Dvinskikh, S V

    2016-01-21

    Dipolar recoupling is an essential part of current solid-state NMR methodology for probing atomic-resolution structure and dynamics in solids and soft matter. Recently described magic-echo amplitude- and phase-modulated cross-polarization heteronuclear recoupling strategy aims at efficient and robust recoupling in the entire range of coupling constants both in rigid and highly dynamic molecules. In the present study, the properties of this recoupling technique are investigated by theoretical analysis, spin-dynamics simulation, and experimentally. The resonance conditions and the efficiency of suppressing the rf field errors are examined and compared to those for other recoupling sequences based on similar principles. The experimental data obtained in a variety of rigid and soft solids illustrate the scope of the method and corroborate the results of analytical and numerical calculations. The technique benefits from the dipolar resolution over a wider range of coupling constants compared to that in other state-of-the-art methods and thus is advantageous in studies of complex solids with a broad range of dynamic processes and molecular mobility degrees. PMID:26801025

  11. Direct writing of CoFe alloy nanostructures by focused electron beam induced deposition from a heteronuclear precursor

    NASA Astrophysics Data System (ADS)

    Porrati, F.; Pohlit, M.; Müller, J.; Barth, S.; Biegger, F.; Gspan, C.; Plank, H.; Huth, M.

    2015-11-01

    Recently, focused electron beam-induced deposition has been employed to prepare functional magnetic nanostructures with potential in nanomagnetic logic and sensing applications by using homonuclear precursor gases like Fe(CO)5 or Co2(CO)8. Here we show that an extension towards the fabrication of bi-metallic compounds is possible by using a single-source heteronuclear precursor gas. We have grown CoFe alloy magnetic nanostructures from the HFeCo3(CO)12 metal carbonyl precursor. The compositional analysis indicates that the samples contain about 80 at% of metal and 10 at% of carbon and oxygen. Four-probe magnetotransport measurements are carried out on nanowires of various sizes down to a width of 50 nm, for which a room temperature resistivity of 43 μΩcm is found. Micro-Hall magnetometry reveals that 50 nm × 250 nm nanobars of the material are ferromagnetic up to the highest measured temperature of 250 K. Finally, the transmission electron microscopy (TEM) microstructural investigation shows that the deposits consist of a bcc Co-Fe phase mixed with a FeCo2 O4 spinel oxide phase with nanograins of about 5 nm diameter.

  12. Drug solubilization mechanism of α-glucosyl stevia by NMR spectroscopy.

    PubMed

    Zhang, Junying; Higashi, Kenjirou; Ueda, Keisuke; Kadota, Kazunori; Tozuka, Yuichi; Limwikrant, Waree; Yamamoto, Keiji; Moribe, Kunikazu

    2014-04-25

    We investigated the drug solubilization mechanism of α-glucosyl stevia (Stevia-G) which was synthesized from stevia (rebaudioside-A) by transglycosylation. (1)H and (13)C NMR peaks of Stevia-G in water were assigned by two-dimensional (2D) NMR experiments including (1)H-(1)H correlation, (1)H-(13)C heteronuclear multiple bond correlation, and (1)H-(13)C heteronuclear multiple quantum coherence spectroscopies. The (1)H and (13)C peaks clearly showed the incorporation of two glucose units into rebaudioside-A to produce Stevia-G, supported by steviol glycoside and glucosyl residue assays. The concentration-dependent chemical shifts of Stevia-G protons correlated well with a mass-action law model, indicating the self-association of Stevia-G molecules in water. The critical micelle concentration (CMC) was 12.0 mg/mL at 37°C. The aggregation number was 2 below the CMC and 12 above the CMC. Dynamic light scattering and 2D (1)H-(1)H nuclear Overhauser effect spectroscopy (NOESY) NMR experiments demonstrated that Stevia-G self-associated into micelles of a few nanometers in size with a core-shell structure, containing a kaurane diterpenoid-based hydrophobic core and a glucose-based shell. 2D (1)H-(1)H NOESY NMR measurements also revealed that a poorly water-soluble drug, naringenin, was incorporated into the hydrophobic core of the Stevia-G micelle. The Stevia-G self-assembly behavior and micellar drug inclusion capacity can achieve significant enhancement in drug solubility. PMID:24508331

  13. Review of NMR characterization of pyrolysis oils

    DOE PAGESBeta

    Hao, Naijia; Ben, Haoxi; Yoo, Chang Geun; Adhikari, Sushil; Ragauskas, Arthur J.

    2016-08-24

    Here, pyrolysis of renewable biomass has been developed as a method to produce green fuels and chemicals in response to energy security concerns as well as to alleviate environmental issues incurred with fossil fuel usage. However, pyrolysis oils still have limited commercial application, mainly because unprocessed oils cannot be readily blended with current petroleum-based transportation fuels. To better understand these challenges, researchers have applied diverse characterization techniques in the development of bio-oil studies. In particular, nuclear magnetic resonance (NMR) is a key spectroscopic characterization method through analysis of bio-oil components. This review highlights the NMR strategies for pyrolysis oil characterizationmore » and critically discusses the applications of 1H, 13C, 31P, 19F, and two-dimensional (2-D NMR) analyses such as heteronuclear single quantum correlation (HSQC) in representative pyrolysis oil studies.« less

  14. Diagonal free homonuclear correlation using heteronuclei at natural abundance.

    PubMed

    Baishya, Bikash

    2015-07-01

    Homonuclear correlated spectroscopy such as COSY and TOCSY provides crucial structural information. In all homonuclear correlation, the most intense peaks are represented by the diagonal. As a result, the useful cross peaks close to the diagonal get obscured by the huge tails of diagonal peaks. Herein, we show that by editing the proton magnetization by a 13C nucleus in natural abundance, it is possible to eliminate the inphase coherence or untransferred magnetization that leads to the diagonal peak while retaining the antiphase coherence or transferred magnetization required for creation of cross peak. After the coherence transfer step, the untransferred magnetization directly attached to 13C evolves under one bond heteronuclear coupling while the transferred transverse magnetization directly attached to remote 12C does not. As a result, the untransferred magnetization directly attached to 13C can be converted to an unobservable heteronuclear multiple quantum coherence leading to a diagonal free correlated spectrum with a sensitivity penalty of two orders of magnitude but comparable to HSQC kind of experiments at natural abundance. The method demonstrated for COSY and TOCSY allows all proton-proton correlations to be observed except the geminal proton-proton correlations. Further, protons directly attached to heteronuclei other than 13C must be scalar coupled to protons directly attached to 13C to have a detectable cross peak. PMID:26001137

  15. Distinct mechanistic differences in the hydrogen-atom transfer from methane and water by the heteronuclear oxide cluster [Ga2 MgO4](.).

    PubMed

    Li, Jilai; Wu, Xiao-Nan; Zhou, Shaodong; Tang, Shiya; Schlangen, Maria; Schwarz, Helmut

    2015-10-12

    The thermal reactions of the heteronuclear oxide cluster [Ga2 MgO4 ](.+) with methane and water have been studied using state-of-the-art gas-phase experiments in conjunction with quantum-chemical calculations. The significant reactivity differences, favoring activation of the strong OH bond, can be ascribed to a proton-coupled electron transfer (PCET) mechanism operative in the activation of water. This study deepens our mechanistic understanding on how inert RH bonds are cleaved by metal oxides. PMID:26136380

  16. Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Sharma, Kshama; Madhu, P. K.; Agarwal, Vipin

    2016-09-01

    The performance of heteronuclear spin decoupling sequences in solid-state NMR severely degrades when the proton radiofrequency (RF) nutation frequencies (ν1) are close to or at multiples of magic-angle spinning (MAS) frequency (νr) that are referred to as rotary-resonance recoupling conditions (ν1 = n · νr). Recently, two schemes, namely, PISSARRO and rCWApA, have been shown to be less affected by the problem of MAS and RF interference, specifically at the n = 2 rotary-resonance recoupling condition, especially in the fast MAS regime. Here, we systematically evaluate the loss in intensity of several heteronuclear spin decoupling sequences at the n = 1, 2 conditions compared to high-power decoupling in the fast-MAS regime. We propose that in the fast-MAS regime (above 40 kHz) the entire discussion about RF and MAS interference can be avoided by using appropriate low-power decoupling sequences which give comparable performance to decoupling sequences with high-power 1H irradiation of ca.195 kHz.

  17. Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning.

    PubMed

    Sharma, Kshama; Madhu, P K; Agarwal, Vipin

    2016-09-01

    The performance of heteronuclear spin decoupling sequences in solid-state NMR severely degrades when the proton radiofrequency (RF) nutation frequencies (ν1) are close to or at multiples of magic-angle spinning (MAS) frequency (νr) that are referred to as rotary-resonance recoupling conditions (ν1=n·νr). Recently, two schemes, namely, PISSARRO and rCW(ApA), have been shown to be less affected by the problem of MAS and RF interference, specifically at the n=2 rotary-resonance recoupling condition, especially in the fast MAS regime. Here, we systematically evaluate the loss in intensity of several heteronuclear spin decoupling sequences at the n=1, 2 conditions compared to high-power decoupling in the fast-MAS regime. We propose that in the fast-MAS regime (above 40kHz) the entire discussion about RF and MAS interference can be avoided by using appropriate low-power decoupling sequences which give comparable performance to decoupling sequences with high-power (1)H irradiation of ca.195kHz. PMID:27472380

  18. Unexpected effects of third-order cross-terms in heteronuclear spin systems under simultaneous radio-frequency irradiation and magic-angle spinning NMR

    NASA Astrophysics Data System (ADS)

    Tatton, Andrew S.; Frantsuzov, Ilya; Brown, Steven P.; Hodgkinson, Paul

    2012-02-01

    We recently noted [R. K. Harris, P. Hodgkinson, V. Zorin, J.-N. Dumez, B. Elena, L. Emsley, E. Salager, and R. Stein, Magn. Reson. Chem. 48, S103 (2010), 10.1002/mrc.2636] anomalous shifts in apparent 1H chemical shifts in experiments using 1H homonuclear decoupling sequences to acquire high-resolution 1H NMR spectra for organic solids under magic-angle spinning (MAS). Analogous effects were also observed in numerical simulations of model 13C,1H spin systems under homonuclear decoupling and involving large 13C,1H dipolar couplings. While the heteronuclear coupling is generally assumed to be efficiently suppressed by sample spinning at the magic angle, we show that under conditions typically used in solid-state NMR, there is a significant third-order cross-term from this coupling under the conditions of simultaneous MAS and homonuclear decoupling for spins directly bonded to 1H. This term, which is of the order of 100 Hz under typical conditions, explains the anomalous behaviour observed on both 1H and 13C spins, including the fast dephasing observed in 13C{1H} heteronuclear spin-echo experiments under 1H homonuclear decoupling. Strategies for minimising the impact of this effect are also discussed.

  19. Tuning the electronic properties and work functions of graphane/fully hydrogenated h-BN heterobilayers via heteronuclear dihydrogen bonding and electric field control.

    PubMed

    Liang, Qiuhua; Jiang, Junke; Meng, Ruishen; Ye, Huaiyu; Tan, Chunjian; Yang, Qun; Sun, Xiang; Yang, Daoguo; Chen, Xianping

    2016-06-28

    Using density functional theory calculations with van der Waals correction, we show that the electronic properties (band gap and carrier mobility) and work functions of graphane/fully hydrogenated hexagonal boron nitride (G/fHBN) heterobilayers can be favorably tuned via heteronuclear dihydrogen bonding (C-HH-B and C-HH-N) and an external electric field. Our results reveal that G/fHBN heterobilayers have different direct band gaps of ∼1.2 eV and ∼3.5 eV for C-HH-B and C-HH-N bonds, respectively. In particular, these band gaps can be effectively modulated by altering the direction and strength of the external electric field (E-field), and correspondingly exhibit a semiconductor-metal transition. The conformation and stability of G/fHBN heterobilayers show a strong dependence on the heteronuclear dihydrogen bonding. Fantastically, these bonds are stable enough under a considerable external E-field as compared with other van der Waals (vdW) 2D layered materials. The mobilities of G/fHBN heterobilayers we predicted are hole-dominated, reasonably high (improvable up to 200 cm(2) V(-1) s(-1)), and extremely isotropic. We also demonstrate that the work function of G/fHBN heterobilayers is very sensitive to the external E-field and is extremely low. These findings make G/fHBN heterobilayers very promising materials for field-effect transistors and light-emitting devices, and inspire more efforts in the development of 2D material systems using weak interlayer interactions and electric field control. PMID:27265511

  20. Primitive models of chemical association. III. Totally flexible sticky two-point model for multicomponent heteronuclear fixed-chain-length polymerization

    SciTech Connect

    Lin, C.; Kalyuzhnyi, Y.V. |; Stell, G.

    1998-04-01

    A multidensity integral-equation theory for polymerization into freely jointed hard-sphere homonuclear chain fluids proposed earlier [J. Chem. Phys. {bold 106}, 1940 (1997)] is extended to the case of multicomponent heteronuclear chain polymerization. The theory is based on the analytical solution of the polymer Percus{endash}Yevick (PPY) approximation for the totally flexible sticky two-point (S2P) model of associating fluids. The model consists of an n-component mixture of hard spheres of different sizes with species 2,{hor_ellipsis},n{minus}1 bearing two sticky sites A and B, randomly distributed on its surface, and species 1 and n with only one B and A site per particle, respectively. Due to some specific restrictions imposed on the possibility of forming bonds between particles of various species, the present version of the S2P model represents an associating fluid that is able to polymerize into a mixture of heteronuclear chain macromolecules. The structural properties of such a model are studied in the complete-association limit and compared with computer-simulation results for homonuclear hard-sphere chain mixtures, symmetrical diblock copolymers, alternating copolymers, and homonuclear hard-sphere chains in a hard-sphere solvent. Some results for the case of partial association are also presented. The PPY theory represents a quantitatively successful theory for the mixtures of short homonuclear chains and the short copolymer systems studied here. We also expect that the theory will prove to be of the same order of accuracy in investigating the case of partial association. {copyright} {ital 1998 American Institute of Physics.}

  1. Regioselective syntheses of [13C]4-labelled sodium 1-carboxy-2-(2-ethylhexyloxycarbonyl)ethanesulfonate and sodium 2-carboxy-1-(2-ethylhexyloxycarbonyl)ethanesulfonate from [13C]4-maleic anhydride.

    PubMed

    Barsamian, Adam L; Perkins, Matt J; Field, Jennifer A; Blakemore, Paul R

    2014-05-15

    The entitled monohydrolysis products, also known as α-ethylhexyl and β-ethylhexyl sulfosuccinate (EHSS), of the surfactant diisooctyl sulfosuccinate (DOSS) were synthesized in stable isotope-labelled form from [(13)C]4 -maleic anhydride. Sodium [(13)C]4 -1-carboxy-2-(2-ethylhexyloxycarbonyl)ethanesulfonate (α-EHSS) was prepared by the method of Larpent by reaction of 2-ethylhexan-1-ol with [(13)C]4 -maleic anhydride followed by regioselective conjugate addition of sodium bisulfite to the resulting monoester (38% overall yield). The regiochemical outcome of bisulfite addition was confirmed by a combination of (13)C/(13)C (incredible natural abundance double quantum transfer) and (1)H/(13)C (heteronuclear multiple-bond correlation (HMBC)) NMR spectral correlation experiments. Sodium [(13)C]4 -2-carboxy-1-(2-ethylhexyloxycarbonyl)ethanesulfonate (β-EHSS) was prepared in four steps by reaction of 4-methoxybenzyl alcohol with [(13)C]4 -maleic anhydride, regioselective sodium bisulfite addition, N,N'-dicyclohexylcarbodiimide-mediated esterification with 2-ethylhexan-1-ol, and p-methoxybenzyl ester deprotection with trifluoroacetic acid (13% overall yield). The regiochemical outcome of the second synthesis was confirmed by a combination of (1)JCC scalar coupling constant analysis and (1)H/(13)C (HMBC) NMR spectral correlation. The materials prepared are required as internal standards for the liquid chromatography-mass spectrometry (LC-MS)/MS trace analysis of the degradation products of DOSS, the anionic surfactant found in Corexit, the oil dispersant used during emergency response efforts connected to the Deepwater Horizon oil spill of April 2010. PMID:24700711

  2. Coupled long-range carbon-hydrogen correlation experiment without refocusing delay

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, V. V.; Nunlist, Rudi

    In long-range carbon-hydrogen correlation experiments with standard heteronuclear shift correlation sequences cross-peak intensities can be severely attenuated due to modulation by "interfering" long-range couplings with other protons. Often cross peaks, even if the polarization transfer delay, Δ1, is optimized, can be missed due to the wrong choice of the refocusing delay, Δ2. A useful improvement is to eliminate the Δ2 delay and acquire without proton decoupling. A one-step low-pass J filter is introduced before evolution to suppress one-bond correlations and this sequence is compared to decoupled versions (the standard heteronuclear shift correlation sequence and the COLOC sequence with one-step low-pass J filter before evolution and a BIRD pulse midway through Δ2). Using rotenone as an example we show the advantages of removing the "refocusing" ("defocusing") delay and retaining 1H coupling in the F2 dimension. It is suggested that the decrease in S/ N (by a factor of 2 or less) is often not very significant compared to the danger of accidental missing of cross peaks due to the wrong choice of Δ2.

  3. Structures and standard molar enthalpies of formation of a series of Ln(III)–Cu(II) heteronuclear compounds with pyrazine-2,3-dicarboxylic acid

    SciTech Connect

    Yang, Qi; Xie, Gang; Wei, Qing; Chen, Sanping Gao, Shengli

    2014-07-01

    Fifteen lanthanide–copper heteronuclear compounds, formulated as [CuLn{sub 2}(pzdc){sub 4}(H{sub 2}O){sub 6}]·xH{sub 2}O (1–6(x=2), 8(x=3), 9–10(x=4)); [CuLn{sub 2}(pzdc){sub 4}(H{sub 2}O){sub 4}]·xH{sub 2}O (7, 12–13, 15(x=4), 14(x=5), 11(x=8)) (Ln(III)=La(1); Ce(2); Pr(3); Nd(4); Sm(5); Eu(6); Gd(7); Tb(8); Dy(9); Ho(10); Er(11); Tm(12); Yb(13); Lu(14); Y(15); H{sub 2}pzdc (C{sub 6}H{sub 4}N{sub 2}O{sub 4})=pyrazine-2,3-dicarboxylic acid) have been hydrothermally synthesized. All compounds were characterized by element analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. X-ray diffraction analyses confirm that all compounds are isostructural and feature a 3D brick-like framework structure with (4.6{sup 2}){sub 2}(4{sup 2}.6{sup 2}.8{sup 2})(6{sup 3}){sup 2}(6{sup 5}.8){sub 2} topology. Using 1 mol cm{sup −3} HCl(aq) as calorimetric solvent, with an isoperibol solution–reaction calorimeter, the standard molar enthalpies of formation of all compounds were determined by a designed thermochemical cycle. In addition, solid state luminescence properties of compounds 5, 6, 8 and 9 were studied in the solid state. - Graphical abstract: According to Hess' rule, the standard molar enthalpies of formation of Ln–Cu heterometallic coordination compounds were determined by a designed thermochemical cycle. - Highlights: • Fifteen lanthanide–copper heteronuclear isostructural compounds. • Structurally characterization by IR, X-ray diffraction and thermal analysis. • The standard molar enthalpy of formation. • Isoperibol solution–reaction calorimetry.

  4. Correlation Spectroscopy with Two Simultaneous Soft Pulses (TSETSE)

    NASA Astrophysics Data System (ADS)

    Nuzillard, J. M.; Freeman, R.

    An analysis is presented of a new correlation experiment where two self-focusing soft pulses are applied simultaneously to two coupled spins I and S. It is shown that for a certain pulse duration, antiphase dispersion-mode doublets are observed at both sites, although the corresponding single-excitation experiment displays only in-phase absorption. At longer pulse durations appreciable amounts of multiple-quantum coherence are created. Simulations of this behavior are presented in the form of magnetization trajectories during a pair of soft E-BURP-2 pulses, and these predictions are compared with experiments on heteronuclear two-spin systems. The effect (called "TSETSE") shows promise as a one-dimensional correlation experiment and as a practical method of determining scalar coupling constants. An application to the determination of long-range C-H couplings in brucine is reported.

  5. Determination of NH proton chemical shift anisotropy with 14N-1H heteronuclear decoupling using ultrafast magic angle spinning solid-state NMR

    NASA Astrophysics Data System (ADS)

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-12-01

    The extraction of chemical shift anisotropy (CSA) tensors of protons either directly bonded to 14N nuclei (I = 1) or lying in their vicinity using rotor-synchronous recoupling pulse sequence is always fraught with difficulty due to simultaneous recoupling of 14N-1H heteronuclear dipolar couplings and the lack of methods to efficiently decouple these interactions. This difficulty mainly arises from the presence of large 14N quadrupolar interactions in comparison to the rf field that can practically be achieved. In the present work it is demonstrated that the application of on-resonance 14N-1H decoupling with rf field strength ∼30 times weaker than the 14N quadrupolar coupling during 1H CSA recoupling under ultrafast MAS (90 kHz) results in CSA lineshapes that are free from any distortions from recoupled 14N-1H interactions. With the use of extensive numerical simulations we have shown the applicability of our proposed method on a naturally abundant L-Histidine HCl·H2O sample.

  6. pH-Dependent two novel heteronuclear Cu(II)/Sr(II) coordination polymers constructed from 1,3,5-benzenetricarboxylic acid: Synthesis, crystal structures and properties

    NASA Astrophysics Data System (ADS)

    Sun, Qiao-Zhen; Yin, Yi-Biao; Pan, Jun-Qiao; Chai, Li-Yuan; Su, Nan; Liu, Hui; Zhao, Yi-Lin; Liu, Xing-Tao

    2016-02-01

    Two novel heteronuclear coordination polymers, namely, [CuSr2(BTC)2]·10H2O (1) and [Cu2Sr(H4TMA)2]·4H2O (2) (H3BTC = 1,3,5-benzenetricarboxylic acid, H4TMA = 2-hydroxytrimesic acid) were hydrothermally synthesized as pH-dependent products and characterized by elemental analysis (EA), infrared spectroscopy (IR) and single crystal X-ray diffraction. For compound 1, it displays a 3D structure with (2,5,6)-connected net topology. For 2, the H3BTC ligand is oxidized into H4TMA and compound 2 features a 2D layer structure, which is further linked by Cu⋯Cu and Cu⋯O supramolecular interactions into a 3D structure. The results show that the pH plays a crucial role in determining the structure of the compounds. In addition, thermalgravimetric analysis of compounds 1-2 and luminescence property of 1 are also investigated.

  7. Structures and standard molar enthalpies of formation of a series of Ln(III)-Cu(II) heteronuclear compounds with pyrazine-2,3-dicarboxylic acid

    NASA Astrophysics Data System (ADS)

    Yang, Qi; Xie, Gang; Wei, Qing; Chen, Sanping; Gao, Shengli

    2014-07-01

    Fifteen lanthanide-copper heteronuclear compounds, formulated as [CuLn2(pzdc)4(H2O)6]·xH2O (1-6(x=2), 8(x=3), 9-10(x=4); [CuLn2(pzdc)4(H2O)4]·xH2O (7, 12-13, 15(x=4), 14(x=5), 11(x=8) (Ln(III)=La(1); Ce(2); Pr(3); Nd(4); Sm(5); Eu(6); Gd(7); Tb(8); Dy(9); Ho(10); Er(11); Tm(12); Yb(13); Lu(14); Y(15); H2pzdc (C6H4N2O4)=pyrazine-2,3-dicarboxylic acid) have been hydrothermally synthesized. All compounds were characterized by element analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. X-ray diffraction analyses confirm that all compounds are isostructural and feature a 3D brick-like framework structure with {4.62}2{42.62.82}{63}2{65.8}2 topology. Using 1 mol cm-3 HCl(aq) as calorimetric solvent, with an isoperibol solution-reaction calorimeter, the standard molar enthalpies of formation of all compounds were determined by a designed thermochemical cycle. In addition, solid state luminescence properties of compounds 5, 6, 8 and 9 were studied in the solid state.

  8. A molecular dynamics simulation-based interpretation of nuclear magnetic resonance multidimensional heteronuclear spectra of α-synuclein·dopamine adducts.

    PubMed

    Dibenedetto, Domenica; Rossetti, Giulia; Caliandro, Rocco; Carloni, Paolo

    2013-09-24

    Multidimensional heteronuclear nuclear magnetic resonance (NMR) spectroscopy provides valuable structural information about adducts between naturally unfolded proteins and their ligands. These are often highly pharmacologically relevant. Unfortunately, the determination of the contributions to observed chemical shifts changes upon ligand binding is complicated. Here we present a tool that uses molecular dynamics (MD) trajectories to help interpret two-dimensional (2D) NMR data. We apply this tool to the naturally unfolded protein human α-synuclein interacting with dopamine, an inhibitor of fibril formation, and with its oxidation products in water solutions. By coupling 2D NMR experiments with MD simulations of the adducts in explicit water, the tool confirms with experimental data that the ligands bind preferentially to (125)YEMPS(129) residues in the C-terminal region and to a few residues of the so-called NAC region consistently. It also suggests that the ligands might cause conformational rearrangements of distal residues located at the N-terminus. Hence, the performed analysis provides a rationale for the observed changes in chemical shifts in terms of direct contacts with the ligand and conformational changes in the protein. PMID:23964651

  9. Heteronuclear transverse and longitudinal relaxation in AX4 spin systems: Application to 15N relaxations in 15NH4+

    PubMed Central

    Werbeck, Nicolas D.; Hansen, D. Flemming

    2014-01-01

    The equations that describe the time-evolution of transverse and longitudinal 15N magnetisations in tetrahedral ammonium ions, 15NH4+, are derived from the Bloch-Wangsness-Redfield density operator relaxation theory. It is assumed that the relaxation of the spin-states is dominated by (1) the intra-molecular 15N–1H and 1H–1H dipole–dipole interactions and (2) interactions of the ammonium protons with remote spins, which also include the contribution to the relaxations that arise from the exchange of the ammonium protons with the bulk solvent. The dipole–dipole cross-correlated relaxation mechanisms between each of the 15N–1H and 1H–1H interactions are explicitly taken into account in the derivations. An application to 15N-ammonium bound to a 41 kDa domain of the protein DnaK is presented, where a comparison between experiments and simulations show that the ammonium ion rotates rapidly within its binding site with a local correlation time shorter than approximately 1 ns. The theoretical framework provided here forms the basis for further investigations of dynamics of AX4 spin systems, with ammonium ions in solution and bound to proteins of particular interest. PMID:25128779

  10. Opposite Dysregulation of Fragile-X Mental Retardation Protein and Heteronuclear Ribonucleoprotein C Protein Associates with Enhanced APP Translation in Alzheimer Disease.

    PubMed

    Borreca, Antonella; Gironi, Katia; Amadoro, Giusy; Ammassari-Teule, Martine

    2016-07-01

    Amyloid precursor protein (APP) is overexpressed in familiar and sporadic Alzheimer Disease (AD) patients suggesting that, in addition to abnormalities in APP cleavage, enhanced levels of APP full length might contribute to the pathology. Based on data showing that the two RNA binding proteins (RBPs), Fragile-X Mental Retardation Protein (FMRP) and heteronuclear Ribonucleoprotein C (hnRNP C), exert an opposite control on APP translation, we have analyzed whether expression and translation of these two RBPs vary in relation to changes in APP protein and mRNA levels in the AD brain at 1, 3, and 6 months of age. Here, we show that, as expected, human APP is overexpressed in hippocampal total extract from Tg2576 mice at all age points. APP overexpression, however, is not stable over time but reaches its maximal level in 1-month-old mutants in association with the stronger (i) reduction of FMRP and (ii) augmentation of hnRNP C. APP levels then decrease progressively as a function of age in close relationship with the gradual normalization of FMRP and hnRNP C levels. Consistent with the mouse data, expression of FMRP and hnRNP C are, respectively, decreased and increased in hippocampal synaptosomes from sporadic AD patients. Our findings identify two RBP targets that might be manipulated for reducing abnormally elevated levels of APP in the AD brain, with the hypothesis that acting upstream of amyloidogenic processing might contribute to attenuate the amyloid burden. PMID:26048669

  11. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Hou, Guangjin; Lu, Xingyu; Vega, Alexander J.; Polenova, Tatyana

    2014-09-01

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear 1H-X (X = 13C, 15N, 31P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the 1H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the 1H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from 1H chemical shift anisotropy, while keeping the 1H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [15N]-N-acetyl-valine and [U-13C,15N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate 1H-15N dipolar couplings in the context of 3D experiments is presented on U-13C,15N-enriched dynein light chain protein LC8.

  12. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    SciTech Connect

    Hou, Guangjin E-mail: tpolenov@udel.edu; Lu, Xingyu E-mail: lexvega@comcast.net; Vega, Alexander J. E-mail: lexvega@comcast.net; Polenova, Tatyana E-mail: tpolenov@udel.edu

    2014-09-14

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear {sup 1}H-X (X = {sup 13}C, {sup 15}N, {sup 31}P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the {sup 1}H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the {sup 1}H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from {sup 1}H chemical shift anisotropy, while keeping the {sup 1}H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [{sup 15}N]-N-acetyl-valine and [U-{sup 13}C,{sup 15}N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate {sup 1}H-{sup 15}N dipolar couplings in the context of 3D experiments is presented on U-{sup 13}C,{sup 15}N-enriched dynein light chain protein LC8.

  13. The role of interleukin-6 in mitogenic T-cell activation: detection of interleukin-2 heteronuclear RNA by polymerase chain reaction.

    PubMed

    Walz, G; Stevens, C; Zanker, B; Melton, L B; Clark, S C; Suthanthiran, M; Strom, T B

    1991-05-01

    It has been documented that interleukin-6 (IL-6) supports the proliferation of purified, anti-CD3-stimulated murine T cells. We found that stimulation of human peripheral blood mononuclear cells (PBMCs) with anti-CD3 induced a significant accumulation of IL-6 mRNA, indicating that antigen-mediated T-cell activation may involve IL-6 release from accessory cells. Phytohemagglutinin (PHA) had little effect upon IL-6 gene expression. In keeping with these findings, anti-IL-6 reduced but did not abolish anti-CD3-mediated proliferation of PBMCs, but had no significant effect upon PHA-stimulated proliferation. The addition of recombinant (r) IL-6 enhanced the proliferation of anti-CD3-stimulated PBMCs and increased the accumulation of IL-2 mRNA in PHA-stimulated PBMCs during the first 5 hr of culture. Nuclear run-off experiments did not reveal significant changes in IL-2 transcription in PHA plus rIL-6-treated PBMCs attempting to assume that IL-6 mediates stabilization of IL-2 mRNA. However, monitoring of partially spliced IL-2 mRNA by polymerase chain reaction revealed a clear increase in IL-2 heteronuclear RNA. Thus IL-6 increases the rate of IL-2 transcription which was not detectable by conventional in vitro transcription assays. We conclude that anti-CD3 triggers T-cell proliferation through a process that is partially but not entirely dependent upon release of IL-6. IL-6, in turn, supports IL-2 transcription. Insofar as anti-CD3 mimics antigen-triggered activation of the T-cell receptor complex, IL-6 appears to support the early immune response by augmenting antigen-triggered IL-2 gene expression. PMID:1827050

  14. Two heteronuclear dipolar results at the price of one: Quantifying Na/P contacts in phosphosilicate glasses and biomimetic hydroxy-apatite

    NASA Astrophysics Data System (ADS)

    Stevensson, Baltzar; Mathew, Renny; Yu, Yang; Edén, Mattias

    2015-02-01

    The analysis of S{I} recoupling experiments applied to amorphous solids yields a heteronuclear second moment M2 (S-I) that represents the effective through-space dipolar interaction between the detected S spins and the neighboring I-spin species. We show that both M2 (S-I) and M2 (I-S) values are readily accessible from a sole S{I} or I{S} experiment, which may involve either S or I detection, and is naturally selected as the most favorable option under the given experimental conditions. For the common case where I has half-integer spin, an I{S} REDOR implementation is preferred to the S{I} REAPDOR counterpart. We verify the procedure by 23Na{31P} REDOR and 31P{23Na} REAPDOR NMR applied to Na2O-CaO-SiO2-P2O5 glasses and biomimetic hydroxyapatite, where the M2 (P-Na) values directly determined by REAPDOR agree very well with those derived from the corresponding M2 (Na-P) results measured by REDOR. Moreover, we show that dipolar second moments are readily extracted from the REAPDOR NMR protocol by a straightforward numerical fitting of the initial dephasing data, in direct analogy with the well-established procedure to determine M2 (S-I) values from REDOR NMR experiments applied to amorphous materials; this avoids the problems with time-consuming numerically exact simulations whose accuracy is limited for describing the dynamics of a priori unknown multi-spin systems in disordered structures.

  15. Origin of the step structure of molecular exchange-correlation potentials.

    PubMed

    Kohut, Sviataslau V; Polgar, Alexander M; Staroverov, Viktor N

    2016-08-21

    The exact exchange-correlation potential of a stretched heteronuclear diatomic molecule exhibits a localized upshift in the region around the more electronegative atom; by this device the Kohn-Sham scheme ensures that the molecule dissociates into neutral atoms. Baerends and co-workers showed earlier that the upshift originates in the response part of the exchange-correlation potential. We describe a reliable numerical method for constructing the response potential of a given many-electron system and report accurate plots of this quantity. We also demonstrate that the step feature itself can be obtained directly from the interacting wavefunction of the system by computing the so-called average local electron energy. These findings illustrate in previously unavailable detail the mechanism of the formation of the upshift and the role played by static correlation in this process. PMID:26983370

  16. Synthesis of rhodium(III) complexes with tris/tetrakis-benzimidazoles and benzothiazoles--quick identification of cyclometallation by nuclear magnetic resonance spectroscopy.

    PubMed

    Chandrashekhar, N; Gayathri, V; Nanje Gowda, N M

    2009-08-01

    Reactions of rhodium(III) halides with multidentate N,S-heterocycles, (LH3) 1,3,5-tris(benzimidazolyl)benzene (L1H3; 1), 1,3,5-tris(N-methylbenzimidazolyl) benzene (L2H3; 2) and 1,3,5-tris(benzothiazolyl)benzene (L3H3; 3), in the molar ratio 1:1 in methanol-chloroform produced mononuclear cyclometallated products of the composition [RhX2(LH2)(H2O)] (X = Cl, Br, I; LH2 = L1H2, L2H2, L3H2). When the metal to ligand (1-3 or 1,2,4,5-tetrakis(benzothiazolyl)benzene [L4H2; 4]) molar ratio was 2:1, the reactions yielded binuclear complexes of the compositions [Rh2Cl5(LH2)(H2O)3] (LH2 = L1H2, L2H2, L3H2) and [Rh2X4(L4)(H2O)2] (X = Cl, Br, I). Elemental analysis, IR and 1H nuclear magnetic resonance (NMR) chemical shifts supported the binuclear nature of the complexes. Cyclometallation was detected by conventional 13C NMR spectra that showed a doublet around approximately 190 ppm. Cyclometallation was also detected by gradient-enhanced heteronuclear multiple bond correlation (g-HMBC) experiment that showed cross-peaks between the cyclometallated carbon and the central benzene ring protons of 1-3. Cyclometallation was substantiated by two-dimensional 1H-1H correlated experiments (gradient-correlation spectroscopy and rotating frame Overhauser effect spectroscopy) and 1H-13C single bond correlated two-dimensional NMR experiments (gradient-enhanced heteronuclear single quantum coherence). The 1H-15N g-HMBC experiment suggested the coordination of the heterocycles to the metal ion via tertiary nitrogen. PMID:19444858

  17. Analysis of amorphous solid dispersions using 2D solid-state NMR and (1)H T(1) relaxation measurements.

    PubMed

    Pham, Tran N; Watson, Simon A; Edwards, Andrew J; Chavda, Manisha; Clawson, Jacalyn S; Strohmeier, Mark; Vogt, Frederick G

    2010-10-01

    Solid-state NMR (SSNMR) can provide detailed structural information about amorphous solid dispersions of pharmaceutical small molecules. In this study, the ability of SSNMR experiments based on dipolar correlation, spin diffusion, and relaxation measurements to characterize the structure of solid dispersions is explored. Observation of spin diffusion effects using the 2D (1)H-(13)C cross-polarization heteronuclear correlation (CP-HETCOR) experiment is shown to be a useful probe of association between the amorphous drug and polymer that is capable of directly proving glass solution formation. Dispersions of acetaminophen and indomethacin in different polymers are examined using this approach, as well as (1)H double-quantum correlation experiments to probe additional structural features. (1)H-(19)F CP-HETCOR serves a similar role for fluorinated drug molecules such as diflunisal in dispersions, providing a rapid means to prove the formation of a glass solution. Phase separation is detected using (13)C, (19)F, and (23)Na-detected (1)H T(1) experiments in crystalline and amorphous solid dispersions that contain small domains. (1)H T(1) measurements of amorphous nanosuspensions of trehalose and dextran illustrate the ability of SSNMR to detect domain size effects in dispersions that are not glass solutions via spin diffusion effects. Two previously unreported amorphous solid dispersions involving up to three components and containing voriconazole and telithromycin are analyzed using these experiments to demonstrate the general applicability of the approach. PMID:20681586

  18. Myo-inositol hexakisphosphate, isolated from female gametophyte tissue of loblolly pine, inhibits growth of early-stage somatic embryos.

    PubMed

    Wu, Di; Sullards, M Cameron; Oldham, Charlie D; Gelbaum, Les; Lucrezi, Jacob; Pullman, Gerald S; May, Sheldon W

    2012-01-01

    • Myo-inositol hexakisphosphate (InsP(6)), abundant in animals and plants, is well known for its anticancer activity. However, many aspects of InsP(6) function in plants remain undefined. We now report the first evidence that InsP(6) can inhibit cellular proliferation in plants under growth conditions where phosphorus is not limited. • A highly anionic molecule inhibitory to early-stage somatic embryo growth of loblolly pine (LP) was purified chromatographically from late-stage LP female gametophytes (FGs), and then characterized structurally using mass spectrometry (MS) and nuclear magnetic resonance (NMR) analyses. • Exact mass and mass spectrometry-mass spectrometry (MS-MS) fragmentation identified the bioactive molecule as an inositol hexakisphosphate. It was then identified as the myo-isomer (i.e. InsP(6)) on the basis of (1)H-, (31)P- and (13)C-NMR, (1)H-(1)H correlation spectroscopy (COSY), (1)H-(31)P heteronuclear single quantum correlation (HSQC) and (1)H-(13)C HSQC. Topical application of InsP(6) to early-stage somatic embryos indeed inhibits embryonic growth. • Recently evidence has begun to emerge that InsP(6) may also play a regulatory role in plant cells. We anticipate that our findings will help to stimulate additional investigations aimed at elucidating the roles of inositol phosphates in cellular growth and development in plants. PMID:22023391

  19. Identification of endogenous metabolites in human sperm cells using proton nuclear magnetic resonance ((1) H-NMR) spectroscopy and gas chromatography-mass spectrometry (GC-MS).

    PubMed

    Paiva, C; Amaral, A; Rodriguez, M; Canyellas, N; Correig, X; Ballescà, J L; Ramalho-Santos, J; Oliva, R

    2015-05-01

    The objective of this study was to contribute to the first comprehensive metabolomic characterization of the human sperm cell through the application of two untargeted platforms based on proton nuclear magnetic resonance ((1) H-NMR) spectroscopy and gas chromatography coupled to mass spectrometry (GC-MS). Using these two complementary strategies, we were able to identify a total of 69 metabolites, of which 42 were identified using NMR, 27 using GC-MS and 4 by both techniques. The identity of some of these metabolites was further confirmed by two-dimensional (1) H-(1) H homonuclear correlation spectroscopy (COSY) and (1) H-(13) C heteronuclear single-quantum correlation (HSQC) spectroscopy. Most of the metabolites identified are reported here for the first time in mature human spermatozoa. The relationship between the metabolites identified and the previously reported sperm proteome was also explored. Interestingly, overrepresented pathways included not only the metabolism of carbohydrates, but also of lipids and lipoproteins. Of note, a large number of the metabolites identified belonged to the amino acids, peptides and analogues super class. The identification of this initial set of metabolites represents an important first step to further study their function in male gamete physiology and to explore potential reasons for dysfunction in future studies. We also demonstrate that the application of NMR and MS provides complementary results, thus constituting a promising strategy towards the completion of the human sperm cell metabolome. PMID:25854681

  20. Regioselective deprotection of the monosaccharide-bearing thiocyanomethyl group at the anomeric position monitored by reversed-phase HPLC method.

    PubMed

    Abualassal, Qais; Al Azzam, Khaldun M; Jilani, Jamal A

    2016-09-01

    In the current work, the investigation and development of a chemo-enzymatic approach for the synthesis of neo-glycoproteins have been studied. This strategy is based on the regioselective enzymatic hydrolysis of peracetylated monosaccharide, functionalized at the anomeric position (C1) as 1-thio-(S-cyanomethyl) group, a precursor of the 2- iminomethoxyethyl thioglycosides-linker for protein glycosylation, catalyzed by immobilized enzymes to obtain selectively monodeprotected compounds. The use of this activation in C1 is the most frequently used strategy for glycoprotein preparation. The selected biocatalysts are the lipase from Candida rugosa and the acetyl xylan esterase from Bacillus pumilus. A reversed-phase high-performance liquid-chromatographic (HPLC) method for monitoring the regioselective deprotection reaction has been developed. The developed HPLC method was used as a fingerprint to follow the hydrolysis of substrate 1 to substrate 1a and to determine its purity and yield. Moreover, the obtained compound was further purified by flash chromatography. The obtained compound 1a was further characterized using (1) H, (13) C NMR, correlation spectroscopy (COSY) and heteronuclear multiple bond correlation. The resulting product can be used as an intermediate for the preparation of di- and more complex oligosaccharides aimed at protein conjugation. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26864255

  1. Structure of the O-specific polysaccharide of Hafnia alvei PCM 1222 containing 2-aminoethyl phosphate.

    PubMed

    Toukach, F V; Shashkov, A S; Katzenellenbogen, E; Kocharova, N A; Czarny, A; Knirel, Y A; Romanowska, E; Kochetkov, N K

    1996-12-13

    The O-specific polysaccharide of H. alvei strain PCM 1222 has a branched hexasaccharide repeating unit containing D-galactose, L-rhamnose, D-ribose, D-galacturonic acid, and 2-acetamido-2-deoxy-D-glucose in the ratios 1:2:1:1:1, as well as 2-aminoethyl phosphate (EtNP) and O-acetyl groups in nonstoichiometric amounts. The polysaccharide was modified by carboxyl reduction, O-deacetylation, and dephosphorylation with 48% hydrofluoric acid, the last reaction being accompanied by removal of the lateral residue of beta-galactofuranose. The modified polysaccharides were studied by methylation analysis and 1H and 13C NMR spectroscopy, including 2D correlation spectroscopy (COSY), H-detected 1H,13C and 1H,31P heteronuclear multiple-quantum coherence (HMQC), 1D NOE, 2D rotating-frame NOE spectroscopy (ROESY), and 2D combined total correlation spectroscopy (TOCSY) and ROESY (TORO). The following structure of the O-deacetylated polysaccharide was established: [formula: see text] In different batches of the polysaccharide, the content of EtNP varied from 0.35 to 0.55 and that of the O-acetyl groups from 0.05 to 0.4 per repeating unit. It was tentatively suggested that the O-acetyl group is located at position 4 of a rhamnosyl residue. PMID:9002188

  2. Electron-correlation effects in enhanced ionization of molecules: A time-dependent generalized-active-space configuration-interaction study

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, S.; Bauch, S.; Madsen, L. B.

    2015-12-01

    We numerically study models of H2 and LiH molecules, aligned collinearly with the linear polarization of the external field, to elucidate the possible role of correlation in the enhanced-ionization (EI) phenomena. Correlation is considered at different levels of approximation with the time-dependent generalized-active-space configuration-interaction method. The results of our studies show that enhanced ionization occurs in multielectron molecules and that correlation is important, and they also demonstrate significant deviations between the results of the single-active-electron approximation and more accurate configuration-interaction methods. We further investigate the role of low-lying excited states in the EI phenomena. With the inclusion of correlation we show strong carrier-envelope-phase effects in the enhanced ionization of the asymmetric heteronuclear LiH -like molecule. The correlated calculation shows an intriguing feature of crossover in enhanced ionization with two carrier-envelope phases at critical internuclear separation.

  3. Electronic Origins of the Variable Efficiency of Room-Temperature Methane Activation by Homo- and Heteronuclear Cluster Oxide Cations [XYO2](+) (X, Y = Al, Si, Mg): Competition between Proton-Coupled Electron Transfer and Hydrogen-Atom Transfer.

    PubMed

    Li, Jilai; Zhou, Shaodong; Zhang, Jun; Schlangen, Maria; Weiske, Thomas; Usharani, Dandamudi; Shaik, Sason; Schwarz, Helmut

    2016-06-29

    The reactivity of the homo- and heteronuclear oxide clusters [XYO2](+) (X, Y = Al, Si, Mg) toward methane was studied using Fourier transform ion cyclotron resonance mass spectrometry, in conjunction with high-level quantum mechanical calculations. The most reactive cluster by both experiment and theory is [Al2O2](•+). In its favorable pathway, this cluster abstracts a hydrogen atom by means of proton-coupled electron transfer (PCET) instead of following the conventional hydrogen-atom transfer (HAT) route. This mechanistic choice originates in the strong Lewis acidity of the aluminum site of [Al2O2](•+), which cleaves the C-H bond heterolytically to form an Al-CH3 entity, while the proton is transferred to the bridging oxygen atom of the cluster ion. In addition, a comparison of the reactivity of heteronuclear and homonuclear oxide clusters [XYO2](+) (X, Y = Al, Si, Mg) reveals a striking doping effect by aluminum. Thus, the vacant s-p hybrid orbital on Al acts as an acceptor of the electron pair from methyl anion (CH3(-)) and is therefore eminently important for bringing about thermal methane activation by PCET. For the Al-doped cluster ions, the spin density at an oxygen atom, which is crucial for the HAT mechanism, acts here as a spectator during the course of the PCET mediated C-H bond cleavage. A diagnostic plot of the deformation energy vis-à-vis the barrier shows the different HAT/PCET reactivity map for the entire series. This is a strong connection to the recently discussed mechanism of oxidative coupling of methane on magnesium oxide surfaces proceeding through Grignard-type intermediates. PMID:27241233

  4. Structure determination of a bio-inspired self-assembled light-harvesting antenna by solid-state NMR and molecular modeling.

    PubMed

    Pandit, Anjali; Ocakoglu, Kasim; Buda, Francesco; van Marle, Thomas; Holzwarth, Alfred R; de Groot, Huub J M

    2013-09-26

    The molecular stacking of an artificial light-harvesting antenna self-assembled from 3(1)-aminofunctionalized zinc-chlorins was determined by solid-state NMR in combination with quantum-chemical and molecular-mechanics modeling. A library of trial molecular stacking arrangements was generated based on available structural data for natural and semisynthetic homologues of the Zn-chlorins. NMR assignments obtained for the monomer in solution were validated for self-assembled aggregates and refined with (1)H-(13)C heteronuclear correlation spectroscopy data collected from samples with (13)C at natural abundance. Solid-state ring-current shifts for the (1)H provided spatial constraints to determine the molecular overlap. This procedure allows for a discrimination between different self-assembled structures and a classification of the stacking mode in terms of electric dipole alignment and π-π interactions, parameters that determine the functional properties of light-harvesting assemblies and conducting nanowires. The combination with quantum-mechanical modeling then allowed building a low-resolution packing model in silico from molecular stacks. The method allows for moderate disorder and residual polymorphism at the stack or molecular level and is generally applicable to determine molecular packing structures of aromatic molecules with structural asymmetry, such as is commonly provided by functionalized side chains that serve to tune the self-assembly process. PMID:23566216

  5. Zinc chlorins for artificial light-harvesting self-assemble into antiparallel stacks forming a microcrystalline solid-state material

    PubMed Central

    Ganapathy, Swapna; Sengupta, Sanchita; Wawrzyniak, Piotr K.; Huber, Valerie; Buda, Francesco; Baumeister, Ute; Würthner, Frank; de Groot, Huub J. M.

    2009-01-01

    We introduce a concept to solve the structure of a microcrystalline material in the solid-state at natural abundance without access to distance constraints, using magic angle spinning (MAS) NMR spectroscopy in conjunction with X-ray powder diffraction and DFT calculations. The method is applied to a novel class of materials that form (semi)conductive 1D wires for supramolecular electronics and artificial light-harvesting. The zinc chlorins 3-devinyl-31-hydroxymethyl-132-demethoxycarbonylpheophorbide a (3′,5′-bis-dodecyloxy)benzyl ester zinc complex 1 and 3-devinyl-31-methoxymethyl-132-demethoxycarbonylpheophorbide a (3′,5′-bis-dodecyloxy)benzyl ester zinc complex 2, self-assemble into extended excitonically coupled chromophore stacks. 1H-13C heteronuclear dipolar correlation MAS NMR experiments provided the 1H resonance assignment of the chlorin rings that allowed accurate probing of ring currents related to the stacking of macrocycles. DFT ring-current shift calculations revealed that both chlorins self-assemble in antiparallel π-stacks in planar layers in the solid-state. Concomitantly, X-ray powder diffraction measurements for chlorin 2 at 80 °C revealed a 3D lattice for the mesoscale packing that matches molecular mechanics optimized aggregate models. For chlorin 2 the stacks alternate with a periodicity of 0.68 nm and a 3D unit cell with an approximate volume of 6.28 nm3 containing 4 molecules, which is consistent with space group P21221. PMID:19587237

  6. Secondary Structures in a Freeze-Dried Lignite Humic Acid Fraction Caused by Hydrogen-Bonding of Acidic Protons with Aromatic Rings.

    PubMed

    Cao, Xiaoyan; Drosos, Marios; Leenheer, Jerry A; Mao, Jingdong

    2016-02-16

    A lignite humic acid (HA) was separated from inorganic and non-HA impurities (i.e., aluminosilicates, metals) and fractionated by a combination of dialysis and XAD-8 resin. Fractionation revealed a more homogeneous structure of lignite HA. New and more specific structural information on the main lignite HA fraction is obtained by solid-state nuclear magnetic resonance (NMR) spectroscopy. Quantitative (13)C multiple cross-polarization (multiCP) NMR indicated oxidized phenyl propane structures derived from lignin. MultiCP experiments, conducted on potassium HA salts titrated to pH 10 and pH 12, revealed shifts consistent with carboxylate and phenolate formation, but structural changes associated with enolate formation from aromatic beta keto acids were not detected. Two-dimensional (1)H-(13)C heteronuclear correlation (2D HETCOR) NMR indicated aryl-aliphatic ketones, aliphatic and aromatic carboxyl groups, phenol, and methoxy phenyl ethers. Acidic protons from carboxyl groups in both the lignite HA fraction and a synthetic HA-like polycondensate were found to be hydrogen-bonded with electron-rich aromatic rings. Our results coupled with published infrared spectra provide evidence for the preferential hydrogen bonding of acidic hydrogens with electron-rich aromatic rings rather than adjacent carbonyl groups. These hydrogen-bonding interactions likely result from stereochemical arrangements in primary structures and folding. PMID:26836017

  7. NMR characterization of HIV-1 reverse transcriptase binding to various non-nucleoside reverse transcriptase inhibitors with different activities

    PubMed Central

    Thammaporn, Ratsupa; Yagi-Utsumi, Maho; Yamaguchi, Takumi; Boonsri, Pornthip; Saparpakorn, Patchreenart; Choowongkomon, Kiattawee; Techasakul, Supanna; Kato, Koichi; Hannongbua, Supa

    2015-01-01

    Human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) is an important target for antiviral therapy against acquired immunodeficiency syndrome. However, the efficiency of available drugs is impaired most typically by drug-resistance mutations in this enzyme. In this study, we applied a nuclear magnetic resonance (NMR) spectroscopic technique to the characterization of the binding of HIV-1 RT to various non-nucleoside reverse transcriptase inhibitors (NNRTIs) with different activities, i.e., nevirapine, delavirdine, efavirenz, dapivirine, etravirine, and rilpivirine. 1H-13C heteronuclear single-quantum coherence (HSQC) spectral data of HIV-1 RT, in which the methionine methyl groups of the p66 subunit were selectively labeled with 13C, were collected in the presence and absence of these NNRTIs. We found that the methyl 13C chemical shifts of the M230 resonance of HIV-1 RT bound to these drugs exhibited a high correlation with their anti-HIV-1 RT activities. This methionine residue is located in proximity to the NNRTI-binding pocket but not directly involved in drug interactions and serves as a conformational probe, indicating that the open conformation of HIV-1 RT was more populated with NNRTIs with higher inhibitory activities. Thus, the NMR approach offers a useful tool to screen for novel NNRTIs in developing anti-HIV drugs. PMID:26510386

  8. Chemical structures of manure from conventional and phytase transgenic pigs investigated by advanced solid-state NMR spectroscopy.

    PubMed

    Mao, Jingdong; Ajakaiye, Ayodele; Lan, Yeqing; Olk, Dan C; Ceballos, Michael; Zhang, Tiequan; Fan, Ming Z; Forsberg, Cecil W

    2008-03-26

    Nonpoint phosphorus (P) pollution from animal manure is becoming a serious global problem. The current solution for the swine industry includes the enzyme phytase as a component in oil meal and cereal grain-based swine diets. A long-term approach is the production of transgenic phytase pigs that express phytase in the salivary glands and secrete it in the saliva. This study provides a detailed comparison of chemical structures of manure from conventional pigs and transgenic pigs that express phytase under growing and finishing phases using new solid-state NMR techniques. Spectral editing techniques and quantitative NMR techniques were used to identify and quantify specific functional groups. Two-dimensional (1)H- (13)C heteronuclear correlation NMR was used to detect their connectivity. Manure from conventional and transgenic pigs had similar peptide, carbohydrate, and fatty acid components, while those from transgenic pigs contained more carbohydrates and fewer nonpolar alkyls. There was no consistent effect from diets with or without supplemental phosphate or growth stages. PMID:17973446

  9. On the road to improve the bioremediation and electricity-harvesting skills of Geobacter sulfurreducens: functional and structural characterization of multihaem cytochromes.

    PubMed

    Morgado, Leonor; Fernandes, Ana P; Dantas, Joana M; Silva, Marta A; Salgueiro, Carlos A

    2012-12-01

    Extracellular electron transfer is one of the physiological hallmarks of Geobacter sulfurreducens, allowing these bacteria to reduce toxic and/or radioactive metals and grow on electrode surfaces. Aiming to functionally optimize the respiratory electron-transfer chains, such properties can be explored through genetically engineered strains. Geobacter species comprise a large number of different multihaem c-type cytochromes involved in the extracellular electron-transfer pathways. The functional characterization of multihaem proteins is particularly complex because of the coexistence of several microstates in solution, connecting the fully reduced and oxidized states. NMR spectroscopy has been used to monitor the stepwise oxidation of each individual haem and thus to obtain information on each microstate. For the structural study of these proteins, a cost-effective isotopic labelling of the protein polypeptide chains was combined with the comparative analysis of 1H-13C HSQC (heteronuclear single-quantum correlation) NMR spectra obtained for labelled and unlabelled samples. These new methodological approaches allowed us to study G. sulfurreducens haem proteins functionally and structurally, revealing functional mechanisms and key residues involved in their electron-transfer capabilities. Such advances can now be applied to the design of engineered haem proteins to improve the bioremediation and electricity-harvesting skills of G. sulfurreducens. PMID:23176471

  10. Stable isotope-enhanced two- and three-dimensional diffusion ordered 13C NMR spectroscopy (SIE-DOSY 13C NMR)

    NASA Astrophysics Data System (ADS)

    Vermillion, Karl; Price, Neil P. J.

    2009-06-01

    The feasibility of obtaining high quality homonuclear or heteronuclear diffusion-ordered 13C NMR data is shown to be greatly improved by using 13C isotopically-enriched samples. Stable isotope-enhanced diffusion ordered (SIE-DOSY) 13C NMR has been applied to 13C-enriched carbohydrates, and has been used to determine diffusion coefficients for pentose and hexose monosaccharides, and a disaccharide and trisaccharide. These 2D spectra were obtained with as little as 8 min of acquisition time. Fully resolved 3D DOSY-HMQC NMR spectra of [U- 13C]xylose, [U- 13C]glucose, and [1- 13C gal]lactose were obtained in 5 h. Sample derivatization with [ carbonyl- 13C]acetate (peracetylation) extends the usefulness of the technique to included non-labeled sugars; the 13C-carbonyl - carbohydrate ring proton 1H- 13C correlations also provide additional structural information, as shown for the 3-D DOSY-HMQC analysis of a mixture of maltotriose and lactose per-[ carbonyl- 13C]acetates.

  11. Superadditive correlation.

    PubMed

    Giraud, B G; Heumann, J M; Lapedes, A S

    1999-05-01

    The fact that correlation does not imply causation is well known. Correlation between variables at two sites does not imply that the two sites directly interact, because, e.g., correlation between distant sites may be induced by chaining of correlation between a set of intervening, directly interacting sites. Such "noncausal correlation" is well understood in statistical physics: an example is long-range order in spin systems, where spins which have only short-range direct interactions, e.g., the Ising model, display correlation at a distance. It is less well recognized that such long-range "noncausal" correlations can in fact be stronger than the magnitude of any causal correlation induced by direct interactions. We call this phenomenon superadditive correlation (SAC). We demonstrate this counterintuitive phenomenon by explicit examples in (i) a model spin system and (ii) a model continuous variable system, where both models are such that two variables have multiple intervening pathways of indirect interaction. We apply the technique known as decimation to explain SAC as an additive, constructive interference phenomenon between the multiple pathways of indirect interaction. We also explain the effect using a definition of the collective mode describing the intervening spin variables. Finally, we show that the SAC effect is mirrored in information theory, and is true for mutual information measures in addition to correlation measures. Generic complex systems typically exhibit multiple pathways of indirect interaction, making SAC a potentially widespread phenomenon. This affects, e.g., attempts to deduce interactions by examination of correlations, as well as, e.g., hierarchical approximation methods for multivariate probability distributions, which introduce parameters based on successive orders of correlation. PMID:11969452

  12. Washington Correlator

    NASA Technical Reports Server (NTRS)

    Hall, David M.; Boboltz, David

    2013-01-01

    This report summarizes the activities of the Washington Correlator for 2012. The Washington Correlator provides up to 80 hours of attended processing per week plus up to 40 hours of unattended operation, primarily supporting Earth Orientation and astrometric observations. In 2012, the major programs supported include the IVS-R4, IVS-INT, APSG, and CRF observing sessions.

  13. Fluorine-Decoupled Carbon Spectroscopy for the Determination of Configuration at Fully Substituted, Trifluoromethyl- and Perfluoroalkyl-Bearing Carbons: Comparison with 19F–1H Heteronuclear Overhauser Effect Spectroscopy

    PubMed Central

    2016-01-01

    The synthesis of a series of α-trifluoromethylcyclohexanols and analogous trimethylsilyl ethers by addition of the Ruppert–Prakash reagent to substituted cyclohexanones is presented. A method for the assignment of configuration of such compounds, of related α-trifluoromethylcyclohexylamines and of quaternary trifluoromethyl-substituted carbons is described based on the determination of the 3JCH coupling constant between the fluorine-decoupled 13CF3 resonance and the vicinal hydrogens. This method is dubbed fluorine-decoupled carbon spectroscopy and abbreviated FDCS. The method is also applied to the configurational assignment of substances bearing mono-, di-, and perfluoroalkyl rather than trifluoromethyl groups. The configuration of all substances was verified by either 19F−1H heteronuclear Overhauser spectroscopy (HOESY) or X-ray crystallography. The relative merits of FDCS and HOESY are compared and contrasted. 2JCH, 3JCH, and 4JCH coupling constants to 19F decoupled CF3 groups in alkenes and arenes have also been determined and should prove to be useful in the structural assignment of trifluoromethylated alkenes and arenes. PMID:25561269

  14. Interaction with DNA of a heteronuclear [Na2Cu4] coordination cluster obtained from the assembly of two hydroxo-bridged [Cu(II)2] units by a dimeric sodium nitrate template.

    PubMed

    Mandal, Debashree; Chauhan, Mala; Arjmand, Farukh; Aromí, Guillem; Ray, Debashis

    2009-11-14

    The heteronuclear [Na(2)Cu(4)(bemp)(2)(OH)(2)(NO(3))(2)(OH(2))(4)] x 5 H(2)O (1 x 5H(2)O; H(3)bemp: 2,6-bis-[(2-hydroxyethylimino)-methyl]-4-methyl-phenol) cluster has been synthesized in aqueous-methanol at room temperature and structurally characterized. The water soluble complex is obtained from the template assembly of two [Cu(2)(bemp)(OH)] neutral fragments through their weak oxophillic interactions with two interconnected NaNO(3) units as core. Four [Na(2)Cu(4)] units form a metal-organic cage arrangement in the crystal lattice that traps a (H(2)O)(7) cluster. Variable-temperature magnetic susceptibility measurements (2-300 K) reveals a strong antiferromagnetic coupling between the Cu(II) ions within the dimers with J = -124.1 cm(-1) (in the H = -2JS(1)S(2) convention). The interaction of complex 1 x 3H(2)O with calf thymus DNA (binding constant K(b), 4.6 x 10(4) M(-1)) in Tris buffer was studied by UV-visible and emission titration, and cyclic voltammetry. The hexanuclear Na(2)Cu(4) complex also binds double-stranded supercoiled plasmid pBR322 DNA and displays efficient hydrolytic cleavage. The hydrolytic mechanism is supported by evidence from DNA relegation employing T4 ligase assay and reactive oxygen species (ROS) quenching cleavage experiments. PMID:20449195

  15. Bond Functions and Core Correlation Energy Contributions To HeBe Potential

    NASA Astrophysics Data System (ADS)

    Shalabi, A. S.; Nour, E. M.; Abdel Halim, W. S.

    An empirical scheme for implementation of bond functions in heteronuclear diatomics is suggested and applied to HeBe using universal even-tempered functions. The effects of bond functions and core-correlation energy on the interaction potential of HeBe calculated at the uncorrelated (SCF) and correlated (MBPT and CC) levels are examined. The results confirm that an accuracy of sub μ Hartree level can be obtained using even-tempered functions with s-, p-, and d- symmetry and that bond functions of size {4s2p} for He and {6s3p} for Be recovers 100% of energy lowering obtained from the addition of 10d atom-centered functions to He and 13d atom centred functions to Be. The various treatments of the electron correlation, conclude that the system is interacting weakly with a well depth from 14.5-24.7 μEh at a separation near 9.1a0 compared with 20.7-25.5 μEh previously reported with a rather limited basis set. The most reliable well depth corrected for BSSE (19.0 μEh) was obtained at the CC-SD(T)level at separation of 8.71a0 taking into account the effects of bond functions and core correlation energy. Potential energy curves at the CC-SD(T) valence and CC-SD(T) valence + core correlation levels are analyzed in analytical forms in terms of exchange repulsion, induction and dispersion components.

  16. A theoretical study on the molecular structure and vibrational (FT-IR and Raman) spectra of cyano-bridged heteronuclear polymeric complex of triethylenetetramine

    NASA Astrophysics Data System (ADS)

    Kürkçüoğlu, Güneş Süheyla; Çetinkaya, Fulya; Arslan, Taner

    The cyano bridged complex of triethylenetetramine was characterized by FT-IR, Raman spectroscopy and X-ray single crystal diffraction analysis. The molecular geometry and vibrational frequencies of the complex in the ground state have been calculated by using B3LYP density functional method with LANL2DZ basis set. A good correlation was found via comparison of the experimental and theoretical vibrational frequencies of complex. The complex of the type [Zn(teta)Ni(μ-CN)2(CN)2]n has been studied in the 4000-250 cm-1 region and assignment of all the observed bands were made. The analysis of the FT-IR and Raman spectra indicates that there are some structure spectra correlations.

  17. HCCCH Experiment for Through-Bond Correlation of Thymine Resonances in 13C-Labeled DNA Oligonucleotides

    NASA Astrophysics Data System (ADS)

    Sklenář, Vladimír.; Masse, James E.; Feigon, Juli

    1999-04-01

    Application of heteronuclear magnetic resonance pulse methods to13C,15N-labeled nucleic acids is important for the accurate structure determination of larger RNA and DNA oligonucleotides and protein-nucleic acid complexes. These methods have been applied primarily to RNA, due to the availability of labeled samples. The two major differences between DNA and RNA are at the C2‧ of the ribose and deoxyribose and the additional methyl group on thymine versus uracil. We have enzymatically synthesized a13C,15N-labeled 32 base DNA oligonucleotide that folds to form an intramolecular triplex. We present two- and three-dimensional versions of a new HCCCH-TOCSY experiment that provides intraresidue correlation between the thymine H6 and methyl resonances via the intervening carbons (H6-C6-C5-Cme-Hme).

  18. Correlative Tomography

    NASA Astrophysics Data System (ADS)

    Burnett, T. L.; McDonald, S. A.; Gholinia, A.; Geurts, R.; Janus, M.; Slater, T.; Haigh, S. J.; Ornek, C.; Almuaili, F.; Engelberg, D. L.; Thompson, G. E.; Withers, P. J.

    2014-04-01

    Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative tomography where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed tomography, serial section FIB-SEM tomography, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques.

  19. Correlative tomography.

    PubMed

    Burnett, T L; McDonald, S A; Gholinia, A; Geurts, R; Janus, M; Slater, T; Haigh, S J; Ornek, C; Almuaili, F; Engelberg, D L; Thompson, G E; Withers, P J

    2014-01-01

    Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative tomography where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed tomography, serial section FIB-SEM tomography, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques. PMID:24736640

  20. Correlative Tomography

    PubMed Central

    Burnett, T. L.; McDonald, S. A.; Gholinia, A.; Geurts, R.; Janus, M.; Slater, T.; Haigh, S. J.; Ornek, C.; Almuaili, F.; Engelberg, D. L.; Thompson, G. E.; Withers, P. J.

    2014-01-01

    Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative tomography where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed tomography, serial section FIB-SEM tomography, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques. PMID:24736640

  1. A latent reactive handle for functionalising heparin-like and LMWH deca- and dodecasaccharides† †Electronic supplementary information (ESI) available: Details of experimental procedures not contained in the main text and also 1H, 13C, COSY, HMQC/HSQC NMR and MS data for compounds 2–27. CCDC 998097–998099. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5ob01706h

    PubMed Central

    Miller, Gavin J.; Broberg, Karl. R.; Rudd, Claire; Helliwell, Madeleine R.; Jayson, Gordon C.

    2015-01-01

    d-Glucosamine derivatives bearing latent O4 functionality provide modified H/HS-type disaccharide donors for a final stage capping approach enabling introduction of conjugation-suitable, non-reducing terminal functionality to biologically important glycosaminoglycan oligosaccharides. Application to the synthesis of the first O4-terminus modified synthetic LMWH decasaccharide and an HS-like dodecasaccharide is reported. PMID:26381107

  2. NMR assignments of mitochondrial cyclophilin Cpr3 from Saccharomyces cerevisiae.

    PubMed

    Shukla, Vaibhav Kumar; Singh, Jai Shankar; Trivedi, Dipesh; Hosur, Ramakrishna V; Kumar, Ashutosh

    2016-04-01

    Cyclophilins regulate protein folding, transport and signalling through catalysis of proline isomerization, and are ubiquitously expressed in both prokaryotes and eukaryotes. Cpr3 is the yeast mitochondrial cyclophilin and it is structurally and biophysically uncharacterized so far. Yeast cyclophilin gene cpr3 is essential for the lactate metabolism. Here, we report (1)H, (13)C, and (15)N chemical shift assignments of Cpr3 protein determined by various 2D and 3D heteronuclear NMR experiments at pH 6.5, and temperature 298 K. PMID:26897529

  3. Structural features of a bituminous coal and their changes during low-temperature oxidation and loss of volatiles investigated by advanced solid-state NMR spectroscopy

    USGS Publications Warehouse

    Mao, J.-D.; Schimmelmann, A.; Mastalerz, Maria; Hatcher, P.G.; Li, Y.

    2010-01-01

    Quantitative and advanced 13C solid-state NMR techniques were employed to investigate (i) the chemical structure of a high volatile bituminous coal, as well as (ii) chemical structural changes of this coal after evacuation of adsorbed gases, (iii) during oxidative air exposure at room temperature, and (iv) after oxidative heating in air at 75 ??C. The solid-state NMR techniques employed in this study included quantitative direct polarization/magic angle spinning (DP/MAS) at a high spinning speed of 14 kHz, cross polarization/total sideband suppression (CP/TOSS), dipolar dephasing, CH, CH2, and CHn selection, 13C chemical shift anisotropy (CSA) filtering, two-dimensional (2D) 1H-13C heteronuclear correlation NMR (HETCOR), and 2D HETCOR with 1H spin diffusion. With spectral editing techniques, we identified methyl CCH 3, rigid and mobile methylene CCH2C, methine CCH, quaternary Cq, aromatic CH, aromatic carbons bonded to alkyls, small-sized condensed aromatic moieties, and aromatic C-O groups. With direct polarization combined with spectral-editing techniques, we quantified 11 different types of functional groups. 1H-13C 2D HETCOR NMR experiments indicated spatial proximity of aromatic and alkyl moieties in cross-linked structures. The proton spin diffusion experiments indicated that the magnetization was not equilibrated at a 1H spin diffusion time of 5 ms. Therefore, the heterogeneity in spatial distribution of different functional groups should be above 2 nm. Recoupled C-H long-range dipolar dephasing showed that the fraction of large charcoal-like clusters of polycondensed aromatic rings was relatively small. The exposure of this coal to atmospheric oxygen at room temperature for 6 months did not result in obvious chemical structural changes of the coal, whereas heating at 75 ??C in air for 10 days led to oxidation of coal and generated some COO groups. Evacuation removed most volatiles and caused a significant reduction in aliphatic signals in its DP

  4. Carbon-proton scalar couplings in RNA. 3D heteronuclear and 2D isotope-edited NMR of a [sup 13]C-labeled extra-stable hairpin

    SciTech Connect

    Hines, J.V.; Landry, S.M.; Varani, G.; Tinoco, I. Jr. Lawrence Berkeley Lab., CA )

    1994-06-29

    Long range carbon-proton scalar couplings were measured for an RNA hairpin of 12 nucleotides using 3D and [sup 13]C-edited 2D NMR. The large one-bond carbon-proton scalar couplings ([sup 1]J[sub CH]) and small n-bond couplings ([sup 1]J[sub CH]) produce ECOSY type cross-peaks, thus facilitating the determination of the sign and magnitude of the smaller [sup 2]J[sub CH] or [sup 3]J[sub CH]. The UUCGRNA hairpin (5[prime]-rGGACUUCGGUCC-3[prime]), whose structure has been determined by our laboratory, was uniformly [sup 13]C-labeled at 30% isotopic enrichment. The observed [sup 1]J[sub CH] couplings were then correlated to the known structure. The signs of [sup 2]J[sub C4[prime]H5[prime

  5. Correlative microscopy.

    PubMed

    Loussert Fonta, Céline; Humbel, Bruno M

    2015-09-01

    In recent years correlative microscopy, combining the power and advantages of different imaging system, e.g., light, electrons, X-ray, NMR, etc., has become an important tool for biomedical research. Among all the possible combinations of techniques, light and electron microscopy, have made an especially big step forward and are being implemented in more and more research labs. Electron microscopy profits from the high spatial resolution, the direct recognition of the cellular ultrastructure and identification of the organelles. It, however, has two severe limitations: the restricted field of view and the fact that no live imaging can be done. On the other hand light microscopy has the advantage of live imaging, following a fluorescently tagged molecule in real time and at lower magnifications the large field of view facilitates the identification and location of sparse individual cells in a large context, e.g., tissue. The combination of these two imaging techniques appears to be a valuable approach to dissect biological events at a submicrometer level. Light microscopy can be used to follow a labelled protein of interest, or a visible organelle such as mitochondria, in time, then the sample is fixed and the exactly same region is investigated by electron microscopy. The time resolution is dependent on the speed of penetration and fixation when chemical fixatives are used and on the reaction time of the operator for cryo-fixation. Light microscopy can also be used to identify cells of interest, e.g., a special cell type in tissue or cells that have been modified by either transfections or RNAi, in a large population of non-modified cells. A further application is to find fluorescence labels in cells on a large section to reduce searching time in the electron microscope. Multiple fluorescence labelling of a series of sections can be correlated with the ultrastructure of the individual sections to get 3D information of the distribution of the marked proteins: array

  6. Correlation spectrometer

    DOEpatents

    Sinclair, Michael B.; Pfeifer, Kent B.; Flemming, Jeb H.; Jones, Gary D.; Tigges, Chris P.

    2010-04-13

    A correlation spectrometer can detect a large number of gaseous compounds, or chemical species, with a species-specific mask wheel. In this mode, the spectrometer is optimized for the direct measurement of individual target compounds. Additionally, the spectrometer can measure the transmission spectrum from a given sample of gas. In this mode, infrared light is passed through a gas sample and the infrared transmission signature of the gasses present is recorded and measured using Hadamard encoding techniques. The spectrometer can detect the transmission or emission spectra in any system where multiple species are present in a generally known volume.

  7. Proton-detected 3D 14N/14N/1H isotropic shift correlation experiment mediated through 1H-1H RFDR mixing on a natural abundant sample under ultrafast MAS

    NASA Astrophysics Data System (ADS)

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-09-01

    In this contribution, we have demonstrated a proton detection-based approach on a natural abundant powdered L-Histidine HCl-H2O sample at ultrafast magic angle spinning (MAS) to accomplish 14N/14N correlation from a 3D 14N/14N/1H isotropic shift correlation experiment mediated through 1H finite-pulse radio frequency-driven recoupling (fp-RFDR). Herein the heteronuclear magnetization transfer between 14N and 1H has been achieved by HMQC experiment, whereas 14N/14N correlation is attained through enhanced 1H-1H spin diffusion process due to 1H-1H dipolar recoupling during the RFDR mixing. While the use of ultrafast MAS (90 kHz) provides sensitivity enhancement through increased 1H transverse relaxation time (T2), the use of micro-coil probe which can withstand strong 14N radio frequency (RF) fields further improves the sensitivity per unit sample volume.

  8. Synthesis, X-ray structure, and spectroscopic and electrochemical properties of novel heteronuclear ruthenium-osmium complexes with an asymmetric triazolate bridge

    SciTech Connect

    Hage, R.; Haasnoot, J.G.; Nieuwenhuis, H.A.; Reedijk, J. ); De Ridder, D.J.A. ); Vos, J.G. )

    1990-12-05

    The heterodinuclear compounds ((bpy){sub 2}Ru(bpt)Os(bpy){sub 2})(PF{sub 6}){sub 3} (RuOs) and ((bpy){sub 2}Os(bpt)Ru(bpy){sub 2})(PF{sub 6}){sub 3} (OsRu), where Hbpt = 3,5-bis(pyridin-2-yl)-1,2,4-triazole and bpy = 2,2{prime}-bipyridine, have been prepared and characterized. The crystal and molecular structures of ((Ru(bpy){sub 2}){sub 2}(bpt))(CF{sub 3}SO{sub 3}){sub 3}{center dot}4H{sub 2}O and ((bpy){sub 2}Ru(bpt)Os(bpy){sub 2})(CF{sub 3}SO{sub 3}){sub 3}{center dot}4H{sub 2}O have been determined. Only one of the two possible geometrical isomers of the ruthenium dinuclear compound was found in the crystal structure. The two metal centers are coordinated via N(1) and N(4) of the triazole ring. The metal-metal distance is 6.184 (2) {angstrom}. The NMR data revealed that the OsRu isomer has a similar structure, but with the osmium center bound via N(1) and the ruthenium ion coordinated via N(4) of the triazole ring. The electrochemical potentials of the two heterodinuclear compounds are significantly different; for the RuOs compound the oxidation potentials are 0.73 and 1.20 V, while for the OsRu isomer the oxidation potentials are at 0.65 and 1.30 V vs SCE. These differences in electrochemical behavior between the two isomeric RuOs and OsRu compounds suggest that the N(1) atom of the triazole ring is a better {sigma}-donor than N(4). The mixed-valence dinuclear systems all exhibit rather intense intervalence transition (IT) bands in the near-infrared region, suggesting a moderately strong metal-metal interaction for the bpt systems. A correlation between the energy of the IT bands of the mixed-valence dinuclear complexes and the oxidation potentials has been observed.

  9. Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 2: 2D NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Deshmukh, Ashish P.; Pacheco, Carlos; Hay, Michael B.; Myneni, Satish C. B.

    2007-07-01

    Carboxyl groups are abundant in natural organic molecules (NOM) and play a major role in their reactivity. The structural environments of carboxyl groups in IHSS soil and river humic samples were investigated using 2D NMR (heteronuclear and homonuclear correlation) spectroscopy. Based on the 1H- 13C heteronuclear multiple-bond correlation (HMBC) spectroscopy results, the carboxyl environments in NOM were categorized as Type I (unsubstituted and alkyl-substituted aliphatic/alicyclic), Type II (functionalized carbon substituted), Type IIIa, b (heteroatom and olefin substituted), and Type IVa, b (5-membered heterocyclic aromatic and 6-membered aromatic). The most intense signal in the HMBC spectra comes from the Type I carboxyl groups, including the 2JCH and 3JCH couplings of unsubstituted aliphatic and alicyclic acids, though this spectral region also includes the 3JCH couplings of Type II and III structures. Type II and III carboxyls have small but detectable 2JCH correlations in all NOM samples except for the Suwannee River humic acid. Signals from carboxyls bonded to 5-membered aromatic heterocyclic fragments (Type IVa) are observed in the soil HA and Suwannee River FA, while correlations to 6-membered aromatics (Type IVb) are only observed in Suwannee River HA. In general, aromatic carboxylic acids may be present at concentrations lower than previously imagined in these samples. Vibrational spectroscopy results for these NOM samples, described in an accompanying paper [Hay M. B. and Myneni S. C. B. (2007) Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1: Infrared spectroscopy. Geochim. Cosmochim. Acta (in press)], suggest that Type II and Type III carboxylic acids with α substituents (e.g., -OH, -OR, or -CO 2H) constitute the majority of carboxyl structures in all humic substances examined. Furoic and salicylic acid structures (Type IV) are also feasible fragments, albeit as minor constituents. The

  10. [Structural analysis of vinorelbine in solution determined by nuclear magnetic resonance spectrometry].

    PubMed

    Ribet, J P; Zalavari, P; Commenges, G; Fahy, J; Duflos, A; Schambel, P

    1997-01-01

    An active partnership between the National Centre for Scientific Research (CNRS) and the laboratories Pierre Fabre is underpinning the development of a new molecule, vinorelbine, whose tartrate received marketing authorization in France in 1989, under the name of Navelbine. This medicine was first recommended for the treatment of bronchial cancer "not small cell", then, in 1991, for the treatment of metastatic breast cancer. In 1994, its registration in United States was granted for the treatment of bronchial cancer "not small cell". Vinorelbine is obtained by hemisynthesis using two antecedent monomeric alkaloids, catharanthine and vindoline, followed by a modification of the catharanthine nucleus, so as to produce the first 5' nor vinca-alkaloid. The chemical structure of vinorelbine has been examined in our laboratory using nuclear magnetic resonance spectrometry. Bearing in mind their complexity, the total attribution of the proton spectrum and the carbon-13 spectrum has required experiments for homonuclear (1H-1H) and heteronuclear (1H-13C and 1H-15N) correlation. These experiments have been carried out using a BRUKER spectrometer operating at the nominal proton frequency of 200 MHz in direct detection mode, then with a 400 MHz spectrometer equipped with the reverse detection mode. The chemical structure has thus been analyzed with no ambiguity. The results of this structural study will be presented in due course. We have also undertaken a comparative conformational study between base vinorelbine in chloroform solution and ditartrate vinorelbine (Navelbine) in methanolic solution. The conformation of the vinorelbine molecule in solution in these different solvents have been studied with NOESY (Nuclear Overhauser Effect Spectroscopy) experiments. The results of these experiments have been confirmed by data stemming from molecular modelization. PMID:9138318

  11. Advanced solid-state NMR characterization of marine dissolved organic matter isolated using the coupled reverse osmosis/electrodialysis method.

    PubMed

    Mao, Jingdong; Kong, Xueqian; Schmidt-Rohr, Klaus; Pignatello, Joseph J; Perdue, E Michael

    2012-06-01

    Advanced (13)C solid-state techniques were employed to investigate the major structural characteristics of two surface-seawater dissolved organic matter (DOM) samples isolated using the novel coupled reverse osmosis/electrodialysis method. The NMR techniques included quantitative (13)C direct polarization/magic angle spinning (DP/MAS) and DP/MAS with recoupled dipolar dephasing, (13)C cross-polarization/total sideband suppression (CP/TOSS), (13)C chemical shift anisotropy filter, CH, CH(2), and CH(n) selection, two-dimensional (1)H-(13)C heteronuclear correlation NMR (2D HETCOR), 2D HETCOR combined with dipolar dephasing, and (15)N cross-polarization/magic angle spinning (CP/MAS). The two samples (Coastal and Marine DOM) were collected at the mouth of the Ogeechee River and in the Gulf Stream, respectively. The NMR results indicated that they were structurally distinct. Coastal DOM contained significantly more aromatic and carbonyl carbons whereas Marine DOM was markedly enriched in alkoxy carbon (e.g., carbohydrate-like moieties). Both samples contained significant amide N, but Coastal DOM had nitrogen bonded to aromatic carbons. Our dipolar-dephased spectra indicated that a large fraction of alkoxy carbons were not protonated. For Coastal DOM, our NMR results were consistent with the presence of the major structural units of (1) carbohydrate-like moieties, (2) lignin residues, (3) peptides or amino sugars, and (4) COO-bonded alkyls. For Marine DOM, they were (1) carbohydrate-like moieties, (2) peptides or amino sugars, and (3) COO-bonded alkyls. In addition, both samples contained significant amounts of nonpolar alkyl groups. The potential sources of the major structural units of DOM were discussed in detail. Nonprotonated O-alkyl carbon content was proposed as a possible index of humification. PMID:22553962

  12. NMR-based Structural Analysis of the Complete Rough-type Lipopolysaccharide Isolated from Capnocytophaga canimorsus*

    PubMed Central

    Zähringer, Ulrich; Ittig, Simon; Lindner, Buko; Moll, Hermann; Schombel, Ursula; Gisch, Nicolas; Cornelis, Guy R.

    2014-01-01

    We here describe the NMR analysis of an intact lipopolysaccharide (LPS, endotoxin) in water with 1,2-dihexanoyl-sn-glycero-3-phosphocholine as detergent. When HPLC-purified rough-type LPS of Capnocytophaga canimorsus was prepared, 13C,15N labeling could be avoided. The intact LPS was analyzed by homonuclear (1H) and heteronuclear (1H,13C, and 1H,31P) correlated one- and two-dimensional NMR techniques as well as by mass spectrometry. It consists of a penta-acylated lipid A with an α-linked phosphoethanolamine attached to C-1 of GlcN (I) in the hybrid backbone, lacking the 4′-phosphate. The hydrophilic core oligosaccharide was found to be a complex hexasaccharide with two mannose (Man) and one each of 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo), Gal, GalN, and l-rhamnose residues. Position 4 of Kdo is substituted by phosphoethanolamine, also present in position 6 of the branched ManI residue. This rough-type LPS is exceptional in that all three negative phosphate residues are “masked” by positively charged ethanolamine substituents, leading to an overall zero net charge, which has so far not been observed for any other LPS. In biological assays, the corresponding isolated lipid A was found to be endotoxically almost inactive. By contrast, the intact rough-type LPS described here expressed a 20,000-fold increased endotoxicity, indicating that the core oligosaccharide significantly contributes to the endotoxic potency of the whole rough-type C. canimorsus LPS molecule. Based on these findings, the strict view that lipid A alone represents the toxic center of LPS needs to be reassessed. PMID:24993825

  13. Influences of Dilute Organic Adsorbates on the Hydration of Low-Surface-Area Silicates.

    PubMed

    Sangodkar, Rahul P; Smith, Benjamin J; Gajan, David; Rossini, Aaron J; Roberts, Lawrence R; Funkhouser, Gary P; Lesage, Anne; Emsley, Lyndon; Chmelka, Bradley F

    2015-07-01

    Competitive adsorption of dilute quantities of certain organic molecules and water at silicate surfaces strongly influence the rates of silicate dissolution, hydration, and crystallization. Here, we determine the molecular-level structures, compositions, and site-specific interactions of adsorbed organic molecules at low absolute bulk concentrations on heterogeneous silicate particle surfaces at early stages of hydration. Specifically, dilute quantities (∼0.1% by weight of solids) of the disaccharide sucrose or industrially important phosphonic acid species slow dramatically the hydration of low-surface-area (∼1 m(2)/g) silicate particles. Here, the physicochemically distinct adsorption interactions of these organic species are established by using dynamic nuclear polarization (DNP) surface-enhanced solid-state NMR techniques. These measurements provide significantly improved signal sensitivity for near-surface species that is crucial for the detection and analysis of dilute adsorbed organic molecules and silicate species on low-surface-area particles, which until now have been infeasible to characterize. DNP-enhanced 2D (29)Si{(1)H}, (13)C{(1)H}, and (31)P{(1)H} heteronuclear correlation and 1D (29)Si{(13)C} rotational-echo double-resonance NMR measurements establish hydrogen-bond-mediated adsorption of sucrose at distinct nonhydrated and hydrated silicate surface sites and electrostatic interactions with surface Ca(2+) cations. By comparison, phosphonic acid molecules are found to adsorb electrostatically at or near cationic calcium surface sites to form Ca(2+)-phosphonate complexes. Although dilute quantities of both types of organic molecules effectively inhibit hydration, they do so by adsorbing in distinct ways that depend on their specific architectures and physicochemical interactions. The results demonstrate the feasibility of using DNP-enhanced NMR techniques to measure and assess dilute adsorbed molecules and their molecular interactions on low

  14. Characterization of a buried neutral histidine residue in Bacillus circulans xylanase: NMR assignments, pH titration, and hydrogen exchange.

    PubMed Central

    Plesniak, L. A.; Connelly, G. P.; Wakarchuk, W. W.; McIntosh, L. P.

    1996-01-01

    Bacillus circulans xylanase contains two histidines, one of which (His 156) is solvent exposed, whereas the other (His 149) is buried within its hydrophobic core. His 149 is involved in a network of hydrogen bonds with an internal water and Ser 130, as well as a potential weak aromatic-aromatic interaction with Tyr 105. These three residues, and their network of interactions with the bound water, are conserved in four homologous xylanases. To probe the structural role played by His 149, NMR spectroscopy was used to characterize the histidines in BCX. Complete assignments of the 1H, 13C, and 15N resonances and tautomeric forms of the imidazole rings were obtained from two-dimensional heteronuclear correlation experiments. An unusual spectroscopic feature of BCX is a peak near 12 ppm arising from the nitrogen bonded 1H epsilon 2 of His 149. Due to its solvent inaccessibility and hydrogen bonding to an internal water molecule, the exchange rate of this proton (4.0 x 10(-5) s-1 at pH*7.04 and 30 degrees C) is retarded by > 10(6)-fold relative to an exposed histidine. The pKa of His 156 is unperturbed at approximately 6.5, as measured from the pH dependence of the 15N- and 1H-NMR spectra of BCX. In contrast, His 149 has a pKa < 2.3, existing in the neutral N epsilon 2H tautomeric state under all conditions examined. BCX unfolds at low pH and 30 degrees C, and thus His 149 is never protonated significantly in the context of the native enzyme. The structural importance of this buried histidine is confirmed by the destablizing effect of substituting a phenylalanine or glutamine at position 149 in BCX. PMID:8931150

  15. Cavity as a Source of Conformational Fluctuation and High-Energy State: High-Pressure NMR Study of a Cavity-Enlarged Mutant of T4Lysozyme

    PubMed Central

    Maeno, Akihiro; Sindhikara, Daniel; Hirata, Fumio; Otten, Renee; Dahlquist, Frederick W.; Yokoyama, Shigeyuki; Akasaka, Kazuyuki; Mulder, Frans A.A.; Kitahara, Ryo

    2015-01-01

    Although the structure, function, conformational dynamics, and controlled thermodynamics of proteins are manifested by their corresponding amino acid sequences, the natural rules for molecular design and their corresponding interplay remain obscure. In this study, we focused on the role of internal cavities of proteins in conformational dynamics. We investigated the pressure-induced responses from the cavity-enlarged L99A mutant of T4 lysozyme, using high-pressure NMR spectroscopy. The signal intensities of the methyl groups in the 1H/13C heteronuclear single quantum correlation spectra, particularly those around the enlarged cavity, decreased with the increasing pressure, and disappeared at 200 MPa, without the appearance of new resonances, thus indicating the presence of heterogeneous conformations around the cavity within the ground state ensemble. Above 200 MPa, the signal intensities of >20 methyl groups gradually decreased with the increasing pressure, without the appearance of new resonances. Interestingly, these residues closely matched those sensing a large conformational change between the ground- and high-energy states, at atmospheric pressure. 13C and 1H NMR line-shape simulations showed that the pressure-induced loss in the peak intensity could be explained by the increase in the high-energy state population. In this high-energy state, the aromatic side chain of F114 gets flipped into the enlarged cavity. The accommodation of the phenylalanine ring into the efficiently packed cavity may decrease the partial molar volume of the high-energy state, relative to the ground state. We suggest that the enlarged cavity is involved in the conformational transition to high-energy states and in the volume fluctuation of the ground state. PMID:25564860

  16. Multidimensional J-driven NMR correlations by single-scan offset-encoded recoupling.

    PubMed

    Lin, Yulan; Lupulescu, Adonis; Frydman, Lucio

    2016-04-01

    Two-dimensional (2D) correlations between bonded heteroatoms, lie at the cornerstone of many uses given to contemporary nuclear magnetic resonance (NMR). Improving the efficiency with which these correlations are established is an important topic in modern NMR, with potential applications in rapid chemical analysis and dynamic biophysical studies. Alternatives have been developed over the last decade to speed up these experiments, based among others on reducing the number of data points that need to be sampled, and/or shortening the inter-scan delays. Approaches have also been proposed to forfeit multi-scan schemes altogether, and complete full 2D correlations in a single shot. Here we explore and discuss a new alternative enabling the collection of such very fast - in principle, single-scan - acquisitions of 2D heteronuclear correlations among bonded species, which operates on the basis of a partial reintroduction of J couplings. Similar approaches had been proposed in the past based on collecting coupled spectra for arrays of off-resonance decoupling values; the proposal that is here introduced operates on the basis of suitably incorporating frequency-swept pulses, into spin-echo sequences. Thanks to the offset-dependent amplitude modulations of the in- and anti-phase components that such sequences impart, chemical shifts of coupled but otherwise unobserved nuclear species, can be extracted from the relative intensities and phases of J-coupled multiplets observed in one-dimensional acquisitions. A description of the steps needed to implement this rapid acquisition approach in a quantitative fashion, as well as applications of the ensuing sequences, are presented. PMID:26852416

  17. Multidimensional J-driven NMR correlations by single-scan offset-encoded recoupling

    NASA Astrophysics Data System (ADS)

    Lin, Yulan; Lupulescu, Adonis; Frydman, Lucio

    2016-04-01

    Two-dimensional (2D) correlations between bonded heteroatoms, lie at the cornerstone of many uses given to contemporary nuclear magnetic resonance (NMR). Improving the efficiency with which these correlations are established is an important topic in modern NMR, with potential applications in rapid chemical analysis and dynamic biophysical studies. Alternatives have been developed over the last decade to speed up these experiments, based among others on reducing the number of data points that need to be sampled, and/or shortening the inter-scan delays. Approaches have also been proposed to forfeit multi-scan schemes altogether, and complete full 2D correlations in a single shot. Here we explore and discuss a new alternative enabling the collection of such very fast - in principle, single-scan - acquisitions of 2D heteronuclear correlations among bonded species, which operates on the basis of a partial reintroduction of J couplings. Similar approaches had been proposed in the past based on collecting coupled spectra for arrays of off-resonance decoupling values; the proposal that is here introduced operates on the basis of suitably incorporating frequency-swept pulses, into spin-echo sequences. Thanks to the offset-dependent amplitude modulations of the in- and anti-phase components that such sequences impart, chemical shifts of coupled but otherwise unobserved nuclear species, can be extracted from the relative intensities and phases of J-coupled multiplets observed in one-dimensional acquisitions. A description of the steps needed to implement this rapid acquisition approach in a quantitative fashion, as well as applications of the ensuing sequences, are presented.

  18. Correlation of tryptophan fluorescence intensity decay parameters with sup 1 H NMR-determined rotamer conformations: (tryptophan sup 2 )oxytocin

    SciTech Connect

    Ross, J.B.A.; Schwartz, G.P.; Laws, W.R. ); Wyssbrod, H.R.; Porter, R.A. ); Michaels, C.A. )

    1992-02-18

    While the fluorescence decay kinetics of tyrosine model compounds can be explained in terms of heterogeneity derived from the three ground-state {chi}{sup 1} rotamers, a similar correlation has yet to be directly observed for a tryptophan residue. In addition, the asymmetric indole ring might also lead to heterogeneity from {chi}{sup 2} rotations. In this paper, the time-resolved and steady-state fluorescence properties of (tryptophan{sup 2})oxytocin at pH 3 are presented and compared with {sup 1}H NMR results. According to the unrestricted analyses of individual fluorescence decay curves taken as a function of emission wavelength-independent decay constants, only three exponential terms are required. In addition, the preexponential weighting factors (amplitudes) have the same relative relationship (weights) as the {sup 1}H NMR-determined {chi}{sup 1} rotamer populations of the indole side chain. {sup 15}N was used in heteronuclear coupling experiments to confirm the rotamer assignments. Inclusion of a linked function restricting the decay amplitudes to the {chi}{sup 1} rotamer populations in the individual decay curve analyses and in the global analysis confirms this correlation. According to qualitative nuclear Overhauser data, there are two {chi}{sup 2} populations.

  19. HyperSPASM NMR: A new approach to single-shot 2D correlations on DNP-enhanced samples

    NASA Astrophysics Data System (ADS)

    Donovan, Kevin J.; Frydman, Lucio

    2012-12-01

    Dissolution DNP experiments are limited to a single or at most a few scans, before the non-Boltzmann magnetization has been consumed. This makes it impractical to record 2D NMR data by conventional, t1-incremented schemes. Here a new approach termed HyperSPASM to establish 2D heteronuclear correlations in a single scan is reported, aimed at dealing with this kind of challenge. The HyperSPASM experiment relies on imposing an amplitude-modulation of the data by a single Δt1 indirect-domain evolution time, and subsequently monitoring the imparted encoding on separate echo and anti-echo pathway signals within a single continuous acquisition. This is implemented via the use of alternating, switching, coherence selection gradients. As a result of these manipulations the phase imparted by a heteronucleus over its indirect domain evolution can be accurately extracted, and 2D data unambiguously reconstructed with a single-shot excitation. The nature of this sequence makes the resulting experiment particularly well suited for collecting indirectly-detected HSQC data on hyperpolarized samples. The potential of the ensuing HyperSPASM method is exemplified with natural-abundance hyperpolarized correlations on model systems.

  20. Codes with special correlation.

    NASA Technical Reports Server (NTRS)

    Baumert, L. D.

    1964-01-01

    Uniform binary codes with special correlation including transorthogonality and simplex code, Hadamard matrices and difference sets uniform binary codes with special correlation including transorthogonality and simplex code, Hadamard matrices and difference sets

  1. IAA Correlator Center

    NASA Technical Reports Server (NTRS)

    Surkis, Igor; Ken, Voitsekh; Melnikov, Alexey; Mishin, Vladimir; Sokolova, Nadezda; Shantyr, Violet; Zimovsky, Vladimir

    2013-01-01

    The activities of the six-station IAA RAS correlator include regular processing of national geodetic VLBI programs Ru-E, Ru-U, and Ru-F. The Ru-U sessions have been transferred in e-VLBI mode and correlated in the IAA Correlator Center automatically since 2011. The DiFX software correlator is used at the IAA in some astrophysical experiments.

  2. Correlation in business networks

    NASA Astrophysics Data System (ADS)

    Souma, Wataru; Aoyama, Hideaki; Fujiwara, Yoshi; Ikeda, Yuichi; Iyetomi, Hiroshi; Kaizoji, Taisei

    2006-10-01

    This paper considers business networks. Through empirical study, we show that business networks display characteristics of small-world networks and scale-free networks. In this paper, we characterize firms as sales and bankruptcy probabilities. A correlation between sales and a correlation between bankruptcy probabilities in business networks are also considered. The results reveal that the correlation between sales depends strongly on the type of network, whereas the correlation between bankruptcy probabilities does so only weakly.

  3. What Is Strong Correlation?

    ERIC Educational Resources Information Center

    Kozak, Marcin

    2009-01-01

    Interpretation of correlation is often based on rules of thumb in which some boundary values are given to help decide whether correlation is non-important, weak, strong or very strong. This article shows that such rules of thumb may do more harm than good, and instead of supporting interpretation of correlation--which is their aim--they teach a…

  4. Reverse Correlation in Neurophysiology

    ERIC Educational Resources Information Center

    Ringach, Dario; Shapley, Robert

    2004-01-01

    This article presents a review of reverse correlation in neurophysiology. We discuss the basis of reverse correlation in linear transducers and in spiking neurons. The application of reverse correlation to measure the receptive fields of visual neurons using white noise and m-sequences, and classical findings about spatial and color processing in…

  5. Constrained Canonical Correlation.

    ERIC Educational Resources Information Center

    DeSarbo, Wayne S.; And Others

    1982-01-01

    A variety of problems associated with the interpretation of traditional canonical correlation are discussed. A response surface approach is developed which allows for investigation of changes in the coefficients while maintaining an optimum canonical correlation value. Also, a discrete or constrained canonical correlation method is presented. (JKS)

  6. VLBI Correlators in Kashima

    NASA Technical Reports Server (NTRS)

    Sekido, Mamoru; Takefuji, Kazuhiro

    2013-01-01

    Kashima Space Technology Center (KSTC) is making use of two kinds of software correlators, the multi-channel K5/VSSP software correlator and the fast wide-band correlator 'GICO3,' for geodetic and R&D VLBI experiments. Overview of the activity and future plans are described in this paper.

  7. Correlations in Werner States

    NASA Astrophysics Data System (ADS)

    Luo, Shun-Long; Li, Nan

    2008-02-01

    Werner states are paradigmatic examples of quantum states and play an innovative role in quantum information theory. In investigating the correlating capability of Werner states, we find the curious phenomenon that quantum correlations, as quantified by the entanglement of formation, may exceed the total correlations, as measured by the quantum mutual information. Consequently, though the entanglement of formation is so widely used in quantifying entanglement, it cannot be interpreted as a consistent measure of quantum correlations per se if we accept the folklore that total correlations are measured (or rather upper bounded) by the quantum mutual information.

  8. Complementarity and Correlations

    NASA Astrophysics Data System (ADS)

    Maccone, Lorenzo; Bruß, Dagmar; Macchiavello, Chiara

    2015-04-01

    We provide an interpretation of entanglement based on classical correlations between measurement outcomes of complementary properties: States that have correlations beyond a certain threshold are entangled. The reverse is not true, however. We also show that, surprisingly, all separable nonclassical states exhibit smaller correlations for complementary observables than some strictly classical states. We use mutual information as a measure of classical correlations, but we conjecture that the first result holds also for other measures (e.g., the Pearson correlation coefficient or the sum of conditional probabilities).

  9. Complementarity and correlations.

    PubMed

    Maccone, Lorenzo; Bruß, Dagmar; Macchiavello, Chiara

    2015-04-01

    We provide an interpretation of entanglement based on classical correlations between measurement outcomes of complementary properties: States that have correlations beyond a certain threshold are entangled. The reverse is not true, however. We also show that, surprisingly, all separable nonclassical states exhibit smaller correlations for complementary observables than some strictly classical states. We use mutual information as a measure of classical correlations, but we conjecture that the first result holds also for other measures (e.g., the Pearson correlation coefficient or the sum of conditional probabilities). PMID:25884117

  10. High-resolution correlation

    NASA Astrophysics Data System (ADS)

    Nelson, D. J.

    2007-09-01

    In the basic correlation process a sequence of time-lag-indexed correlation coefficients are computed as the inner or dot product of segments of two signals. The time-lag(s) for which the magnitude of the correlation coefficient sequence is maximized is the estimated relative time delay of the two signals. For discrete sampled signals, the delay estimated in this manner is quantized with the same relative accuracy as the clock used in sampling the signals. In addition, the correlation coefficients are real if the input signals are real. There have been many methods proposed to estimate signal delay to more accuracy than the sample interval of the digitizer clock, with some success. These methods include interpolation of the correlation coefficients, estimation of the signal delay from the group delay function, and beam forming techniques, such as the MUSIC algorithm. For spectral estimation, techniques based on phase differentiation have been popular, but these techniques have apparently not been applied to the correlation problem . We propose a phase based delay estimation method (PBDEM) based on the phase of the correlation function that provides a significant improvement of the accuracy of time delay estimation. In the process, the standard correlation function is first calculated. A time lag error function is then calculated from the correlation phase and is used to interpolate the correlation function. The signal delay is shown to be accurately estimated as the zero crossing of the correlation phase near the index of the peak correlation magnitude. This process is nearly as fast as the conventional correlation function on which it is based. For real valued signals, a simple modification is provided, which results in the same correlation accuracy as is obtained for complex valued signals.

  11. Almost quantum correlations.

    PubMed

    Navascués, Miguel; Guryanova, Yelena; Hoban, Matty J; Acín, Antonio

    2015-01-01

    Quantum theory is not only successfully tested in laboratories every day but also constitutes a robust theoretical framework: small variations usually lead to implausible consequences, such as faster-than-light communication. It has even been argued that quantum theory may be special among possible theories. Here we report that, at the level of correlations among different systems, quantum theory is not so special. We define a set of correlations, dubbed 'almost quantum', and prove that it strictly contains the set of quantum correlations but satisfies all-but-one of the proposed principles to capture quantum correlations. We present numerical evidence that the remaining principle is satisfied too. PMID:25697645

  12. Local available quantum correlations

    NASA Astrophysics Data System (ADS)

    Mundarain, Douglas F.; de Guevara, María L. Ladrón

    2015-12-01

    In this work, local available quantum correlations are studied. They are defined in terms of mutual information of bipartite local measurements done over an optimal local basis complementary to the local basis which defines the respective classical correlations. For two qubits, it is always possible to choose the basis of classical correlations as the set of eigenvectors of σ _z (the third Pauli matrix) and complementary bases become the sets of eigenvectors of the observables orthogonal to σ _z. It is shown that all states with zero local available quantum correlations are separable but not necessarily strictly classical; this fact puts this kind of correlations in the middle between discord and entanglement. Since in many cases it may suffice to know whether a given state has quantum correlations, the structure of the states with zero local available quantum correlations is presented. It is also shown that there is a close connection between local available quantum correlations and the protocol of entanglement activation developed by Piani et al. (Phys Rev Lett 106:220403, 2011). If a state satisfies the sufficient condition for the entanglement swapping associated with this protocol, this state has nonzero local available quantum correlations.

  13. Site-resolved multiple-quantum filtered correlations and distance measurements by magic-angle spinning NMR: Theory and applications to spins with weak to vanishing quadrupolar couplings.

    PubMed

    Eliav, U; Haimovich, A; Goldbourt, A

    2016-01-14

    We discuss and analyze four magic-angle spinning solid-state NMR methods that can be used to measure internuclear distances and to obtain correlation spectra between a spin I = 1/2 and a half-integer spin S > 1/2 having a small quadrupolar coupling constant. Three of the methods are based on the heteronuclear multiple-quantum and single-quantum correlation experiments, that is, high rank tensors that involve the half spin and the quadrupolar spin are generated. Here, both zero and single-quantum coherence of the half spins are allowed and various coherence orders of the quadrupolar spin are generated, and filtered, via active recoupling of the dipolar interaction. As a result of generating coherence orders larger than one, the spectral resolution for the quadrupolar nucleus increases linearly with the coherence order. Since the formation of high rank tensors is independent of the existence of a finite quadrupolar interaction, these experiments are also suitable to materials in which there is high symmetry around the quadrupolar spin. A fourth experiment is based on the initial quadrupolar-driven excitation of symmetric high order coherences (up to p = 2S, where S is the spin number) and subsequently generating by the heteronuclear dipolar interaction higher rank (l + 1 or higher) tensors that involve also the half spins. Due to the nature of this technique, it also provides information on the relative orientations of the quadrupolar and dipolar interaction tensors. For the ideal case in which the pulses are sufficiently strong with respect to other interactions, we derive analytical expressions for all experiments as well as for the transferred echo double resonance experiment involving a quadrupolar spin. We show by comparison of the fitting of simulations and the analytical expressions to experimental data that the analytical expressions are sufficiently accurate to provide experimental (7)Li-(13)C distances in a complex of lithium, glycine, and water. Discussion

  14. Correlates of Academic Procrastination.

    ERIC Educational Resources Information Center

    Milgram, Norman A.; And Others

    1993-01-01

    Investigated concurrent correlates of academic procrastination in Israeli college preparatory students (n=113). Procrastination in one course of study was found to be moderately correlated with procrastination in another but not to procrastination in routine tasks of daily living. Procrastination was weakly related to emotional upset about it and…

  15. ALMA correlator computer systems

    NASA Astrophysics Data System (ADS)

    Pisano, Jim; Amestica, Rodrigo; Perez, Jesus

    2004-09-01

    We present a design for the computer systems which control, configure, and monitor the Atacama Large Millimeter Array (ALMA) correlator and process its output. Two distinct computer systems implement this functionality: a rack- mounted PC controls and monitors the correlator, and a cluster of 17 PCs process the correlator output into raw spectral results. The correlator computer systems interface to other ALMA computers via gigabit Ethernet networks utilizing CORBA and raw socket connections. ALMA Common Software provides the software infrastructure for this distributed computer environment. The control computer interfaces to the correlator via multiple CAN busses and the data processing computer cluster interfaces to the correlator via sixteen dedicated high speed data ports. An independent array-wide hardware timing bus connects to the computer systems and the correlator hardware ensuring synchronous behavior and imposing hard deadlines on the control and data processor computers. An aggregate correlator output of 1 gigabyte per second with 16 millisecond periods and computational data rates of approximately 1 billion floating point operations per second define other hard deadlines for the data processing computer cluster.

  16. Harmonic electron correlation operator.

    PubMed

    Rassolov, Vitaly A

    2011-07-21

    An appealing way to model electron correlation within the single determinant wave function formalism is through the expectation value of a linear two-electron operator. For practical reasons, it is desirable for such an operator to be universal, i.e., not depend on the positions and types of nuclei in a molecule. We show how a perturbation theory applied to a hookium atom provides for a particular form of a correlation operator, hence called the harmonic correlation operator. The correlation operator approach is compared and contrasted to the traditional ways to describe electron correlation. To investigate the two-electron approximation of this operator, we apply it to many-electron hookium systems. To investigate the harmonic approximation, we apply it to the small atomic systems. Directions of future research are also discussed. PMID:21786991

  17. Strongly-correlated heterostructures

    SciTech Connect

    Okamoto, Satoshi

    2012-01-01

    Electronic phase behavior in correlated-electron systems is a fundamental problem of condensed matter physics. The change in the phase behavior near surfaces and interfaces, i.e., {\\em electronic reconstruction}, is therefore the fundamental issue of the correlated-electron surface or interface science. In addition to basic science, understanding of such a phase behavior is of crucial importance for potential devices exploiting the novel properties of the correlated systems. In this article, we present a general overview of the field, and then discuss the recent theoretical progress mainly focusing on the correlation effects. We illustrate the general concept of {\\em electronic reconstruction} by studying model heterostructures consisting of strongly-correlated systems. Future directions for research are also discussed.

  18. In-situ annotation of carbohydrate diversity, abundance, and degradability in highly complex mixtures using NMR spectroscopy.

    PubMed

    Meier, Sebastian

    2014-12-01

    Many functions of carbohydrates depend on the detection of short structural motifs, approximately up to hexasaccharide length, by receptors or catalysts. This study investigates the usefulness of state-of-the-art (1)H-(13)C nuclear-magnetic-resonance (NMR) spectroscopy for characterizing the diversity, abundance, and degradability of such short structural motifs in plant-derived carbohydrates. Assignments of carbohydrate signals for (1)H-(13)C NMR spectra of beer, wine, and fruit juice yield up to >130 assignments in situ, i.e. in individual samples without separation or derivatization. More than 500 structural motifs can be resolved over a concentration range of ~10(3) in experiments of a few hours duration. The diversity of carbohydrate units increases according to power laws at lower concentrations for both cereal and fruit-derived samples. Simple graphs resolve the smaller overall contribution of more diverse but less abundant motifs to carbohydrate biomass. Susceptibility to enzymatic degradation is probed simultaneously for hundreds of structural motifs to reduce uncertainties in the identification of motifs and to probe enzyme specificity with assigned motifs. Several properties of fundamental biotechnological importance can thus be assessed in situ by heteronuclear NMR methods. PMID:25342297

  19. Correlation reflectometry at TEXTOR

    SciTech Connect

    Kraemer-Flecken, A.; Soldatov, S.; Vowinkel, B.; Mueller, P.

    2010-11-15

    In high temperature fusion plasmas the transport of energy and particles is commonly believed to be driven by turbulence. Turbulence quantities as correlation length and decorrelation time are important for the confinement properties of a plasma. Besides other diagnostics, correlation reflectometry has proven to be a suitable tool for the measurement of turbulence properties. At the medium sized Toroidal EXperiment for Technical Oriented Research (TEXTOR) the existing correlation reflectometry has been recently upgraded. A new reflectometer based on a microwave synthesizer has been developed and installed for the investigation of turbulence properties in a fusion plasma. Together with the existing reflectometer the measurement of radial correlation length and decorrelation time becomes available. Both reflectometers are computer controlled and allow to program individual frequency sequences and the duration of each frequency step. With the existing poloidal antenna array at {theta}=0 deg. and on top of the vacuum vessel, the system allows the measurement of radial correlation and poloidal correlations at the same time. First experiments have been performed and the results on the radial correlation length of density fluctuations in a fusion plasma are presented.

  20. Hadronic Correlations and Fluctuations

    SciTech Connect

    Koch, Volker

    2008-10-09

    We will provide a review of some of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. We will discuss Lattice QCD results on fluctuations and correlations and will put them into context with observables which have been measured in heavy-ion collisions. Special attention will be given to the QCD critical point and the first order co-existence region, and we will discuss how the measurement of fluctuations and correlations can help in an experimental search for non-trivial structures in the QCD phase diagram.

  1. Haystack Observatory VLBI Correlator

    NASA Technical Reports Server (NTRS)

    Titus, Mike; Cappallo, Roger; Corey, Brian; Dudevoir, Kevin; Niell, Arthur; Whitney, Alan

    2013-01-01

    This report summarizes the activities of the Haystack Correlator during 2012. Highlights include finding a solution to the DiFX InfiniBand timeout problem and other DiFX software development, conducting a DBE comparison test following the First International VLBI Technology Workshop, conducting a Mark IV and DiFX correlator comparison, more broadband delay experiments, more u- VLBI Galactic Center observations, and conversion of RDV session processing to the Mark IV/HOPS path. Non-real-time e-VLBI transfers and engineering support of other correlators continued.

  2. Correlation Plenoptic Imaging.

    PubMed

    D'Angelo, Milena; Pepe, Francesco V; Garuccio, Augusto; Scarcelli, Giuliano

    2016-06-01

    Plenoptic imaging is a promising optical modality that simultaneously captures the location and the propagation direction of light in order to enable three-dimensional imaging in a single shot. However, in standard plenoptic imaging systems, the maximum spatial and angular resolutions are fundamentally linked; thereby, the maximum achievable depth of field is inversely proportional to the spatial resolution. We propose to take advantage of the second-order correlation properties of light to overcome this fundamental limitation. In this Letter, we demonstrate that the correlation in both momentum and position of chaotic light leads to the enhanced refocusing power of correlation plenoptic imaging with respect to standard plenoptic imaging. PMID:27314718

  3. Entropic Nonsignaling Correlations

    NASA Astrophysics Data System (ADS)

    Chaves, Rafael; Budroni, Costantino

    2016-06-01

    We introduce the concept of entropic nonsignaling correlations, i.e., entropies arising from probabilistic theories that are compatible with the fact that we cannot transmit information instantaneously. We characterize and show the relevance of these entropic correlations in a variety of different scenarios, ranging from typical Bell experiments to more refined descriptions such as bilocality and information causality. In particular, we apply the framework to derive the first entropic inequality testing genuine tripartite nonlocality in quantum systems of arbitrary dimension and also prove the first known monogamy relation for entropic Bell inequalities. Further, within the context of complex Bell networks, we show that entropic nonlocal correlations can be activated.

  4. Statistics of atmospheric correlations.

    PubMed

    Santhanam, M S; Patra, P K

    2001-07-01

    For a large class of quantum systems, the statistical properties of their spectrum show remarkable agreement with random matrix predictions. Recent advances show that the scope of random matrix theory is much wider. In this work, we show that the random matrix approach can be beneficially applied to a completely different classical domain, namely, to the empirical correlation matrices obtained from the analysis of the basic atmospheric parameters that characterize the state of atmosphere. We show that the spectrum of atmospheric correlation matrices satisfy the random matrix prescription. In particular, the eigenmodes of the atmospheric empirical correlation matrices that have physical significance are marked by deviations from the eigenvector distribution. PMID:11461326

  5. Correlation Plenoptic Imaging

    NASA Astrophysics Data System (ADS)

    D'Angelo, Milena; Pepe, Francesco V.; Garuccio, Augusto; Scarcelli, Giuliano

    2016-06-01

    Plenoptic imaging is a promising optical modality that simultaneously captures the location and the propagation direction of light in order to enable three-dimensional imaging in a single shot. However, in standard plenoptic imaging systems, the maximum spatial and angular resolutions are fundamentally linked; thereby, the maximum achievable depth of field is inversely proportional to the spatial resolution. We propose to take advantage of the second-order correlation properties of light to overcome this fundamental limitation. In this Letter, we demonstrate that the correlation in both momentum and position of chaotic light leads to the enhanced refocusing power of correlation plenoptic imaging with respect to standard plenoptic imaging.

  6. Tsukuba VLBI Correlator

    NASA Technical Reports Server (NTRS)

    Kurihara, Shinobu; Nozawa, Kentaro

    2013-01-01

    The K5/VSSP software correlator (Figure 1), located in Tsukuba, Japan, is operated by the Geospatial Information Authority of Japan (GSI). It is fully dedicated to processing the geodetic VLBI sessions of the International VLBI Service for Geodesy and Astrometry. All of the weekend IVS Intensives (INT2) and the Japanese domestic VLBI observations organized by GSI were processed at the Tsukuba VLBI Correlator.

  7. Correlations and droplet growth

    NASA Technical Reports Server (NTRS)

    Marder, M.

    1985-01-01

    Consideration is given to the time development of a system in which small spheres of a stable phase grow out of a supersaturated melt. The spheres then grow and shrink in a manner similar to Ostwald ripening. The growth process of pairs of particles in an effective background accounts for can be used to explain the long time correlations which develop in the system. The correlations broaden the distribution of particles sizes, even for relatively dilute systems.

  8. Exploration of structure and function in biomolecules through solid-state NMR and computational methods

    NASA Astrophysics Data System (ADS)

    Heider, Elizabeth M.

    dephasing experiments and 1H-- 13C heteronuclear correlation (HETCOR) experiments. A comparison of spectral data confirms the presence of two molecules in the asymmetric unit for form II (Z'=2) and regions of conformational variation between the two forms are posited. Structural rigidity is found throughout both forms and extends into the alkyl groups at the amine with similarties between form I and form II in this moiety. Likely regions of motion are found around the bond axes formed by C1--C5 in form I. This motion is also observed in one of the two molecules of form II. Tensor differences between the two forms at the tetrahydro-pyrrole center indicate that conformational variation between form I and form II exists in the dihedral angles formed by the atoms C14--C13--C3--C2, O--C12--C2--C1, C10--C5--C1--N1 and C21--C20--N1--C4. Finally, SSNMR is applied in conjunction with quantum mechanical calculations in the analysis of a novel polymorph of the anticancer drug paclitaxel. The three dimensional structure of paclitaxel is established through a combination of SSNMR tensor (13C & 15N) and 1H--13C HETCOR data. With two molecules in the asymmetric unit (Z'=2), this represents the first conformational characterization with Z'>1 established solely by SSNMR. Semi-empirical models are constructed and fitted to experimental data by adjusting the conformation of the paclitaxel models and selecting those conformers which minimize the difference between predicted and measured tensors. This computational grid search exhausively samples the conformation of paclitaxel, utilizing more than 600 independent models. HETCOR data at thirteen key positions provide shift assignment to the asymmetric unit for each comparison. The two distinct molecules of the asymmetric unit possess nearly identical baccatin III moieties with matching conformations of the C10 acetyl moiety. Additionally, both are found to exhibit an extended conformation of the phenylisoserine sidechain at the C13 position

  9. Nonclassicality of Temporal Correlations.

    PubMed

    Brierley, Stephen; Kosowski, Adrian; Markiewicz, Marcin; Paterek, Tomasz; Przysiężna, Anna

    2015-09-18

    The results of spacelike separated measurements are independent of distant measurement settings, a property one might call two-way no-signaling. In contrast, timelike separated measurements are only one-way no-signaling since the past is independent of the future but not vice versa. For this reason some temporal correlations that are formally identical to nonclassical spatial correlations can still be modeled classically. We propose a new formulation of Bell's theorem for temporal correlations; namely, we define nonclassical temporal correlations as the ones which cannot be simulated by propagating in time the classical information content of a quantum system given by the Holevo bound. We first show that temporal correlations between results of any projective quantum measurements on a qubit can be simulated classically. Then we present a sequence of general measurements on a single m-level quantum system that cannot be explained by propagating in time an m-level classical system and using classical computers with unlimited memory. PMID:26430975

  10. Correlational Neural Networks.

    PubMed

    Chandar, Sarath; Khapra, Mitesh M; Larochelle, Hugo; Ravindran, Balaraman

    2016-02-01

    Common representation learning (CRL), wherein different descriptions (or views) of the data are embedded in a common subspace, has been receiving a lot of attention recently. Two popular paradigms here are canonical correlation analysis (CCA)-based approaches and autoencoder (AE)-based approaches. CCA-based approaches learn a joint representation by maximizing correlation of the views when projected to the common subspace. AE-based methods learn a common representation by minimizing the error of reconstructing the two views. Each of these approaches has its own advantages and disadvantages. For example, while CCA-based approaches outperform AE-based approaches for the task of transfer learning, they are not as scalable as the latter. In this work, we propose an AE-based approach, correlational neural network (CorrNet), that explicitly maximizes correlation among the views when projected to the common subspace. Through a series of experiments, we demonstrate that the proposed CorrNet is better than AE and CCA with respect to its ability to learn correlated common representations. We employ CorrNet for several cross-language tasks and show that the representations learned using it perform better than the ones learned using other state-of-the-art approaches. PMID:26654210

  11. Correlation ion mobility spectroscopy

    DOEpatents

    Pfeifer, Kent B.; Rohde, Steven B.

    2008-08-26

    Correlation ion mobility spectrometry (CIMS) uses gating modulation and correlation signal processing to improve IMS instrument performance. Closely spaced ion peaks can be resolved by adding discriminating codes to the gate and matched filtering for the received ion current signal, thereby improving sensitivity and resolution of an ion mobility spectrometer. CIMS can be used to improve the signal-to-noise ratio even for transient chemical samples. CIMS is especially advantageous for small geometry IMS drift tubes that can otherwise have poor resolution due to their small size.

  12. FONO: A difficult case for theory. The ELF and ELI-D topological studies on the chemical bonding using correlated wavefunctions

    NASA Astrophysics Data System (ADS)

    Berski, Slawomir; Gordon, Agnieszka J.; Latajka, Zdzislaw

    2013-04-01

    The complicated nature of the chemical bonding in cis and trans isomers of F-O-N=O is discussed based on the results obtained from the topological analysis of electron localization function (η) (ELF), electron localizability index (Y_D^σ), and electron density (ρ). The calculations have been performed for correlated wavefunctions using the CCSD and CASSCF methods. The F-O1 bond with non-bonding basins, V(F) and V'(O1), belongs to the protocovalent type (η,Y_D^σ) and its total population ranges between 0.2 and 0.4e. The central N-O1 bond in the cis form is protocovalent (η, Y_D^σ) with two basins, V(N) and V(O1). The total population oscillates between 0.7 and 0.9e. In the trans isomer, topology of ELF depends on used method. At the CCSD level only one non-bonding basin, V(N), is observed (η). Its population is about 0.5e. According to the definition of a heteronuclear charge-shift (CS) bond, only N-O1 bond in trans-FONO belongs to the CS class. A relation between η- and ρ-topology and N-O1 bond length is discussed.

  13. Cross-Correlated Relaxation of Dipolar Coupling and Chemical-Shift Anisotropy in Magic-Angle Spinning R1ρ NMR Measurements: Application to Protein Backbone Dynamics Measurements.

    PubMed

    Kurauskas, Vilius; Weber, Emmanuelle; Hessel, Audrey; Ayala, Isabel; Marion, Dominique; Schanda, Paul

    2016-09-01

    Transverse relaxation rate measurements in magic-angle spinning solid-state nuclear magnetic resonance provide information about molecular motions occurring on nanosecond-to-millisecond (ns-ms) time scales. The measurement of heteronuclear ((13)C, (15)N) relaxation rate constants in the presence of a spin-lock radiofrequency field (R1ρ relaxation) provides access to such motions, and an increasing number of studies involving R1ρ relaxation in proteins have been reported. However, two factors that influence the observed relaxation rate constants have so far been neglected, namely, (1) the role of CSA/dipolar cross-correlated relaxation (CCR) and (2) the impact of fast proton spin flips (i.e., proton spin diffusion and relaxation). We show that CSA/D CCR in R1ρ experiments is measurable and that the CCR rate constant depends on ns-ms motions; it can thus provide insight into dynamics. We find that proton spin diffusion attenuates this CCR due to its decoupling effect on the doublet components. For measurements of dynamics, the use of R1ρ rate constants has practical advantages over the use of CCR rates, and this article reveals factors that have so far been disregarded and which are important for accurate measurements and interpretation. PMID:27500976

  14. Sensory Correlations in Autism

    ERIC Educational Resources Information Center

    Kern, Janet K.; Trivedi, Madhukar H.; Grannemann, Bruce D.; Garver, Carolyn R.; Johnson, Danny G.; Andrews, Alonzo A.; Savla, Jayshree S.; Mehta, Jyutika A.; Schroeder, Jennifer L.

    2007-01-01

    This study examined the relationship between auditory, visual, touch, and oral sensory dysfunction in autism and their relationship to multisensory dysfunction and severity of autism. The Sensory Profile was completed on 104 persons with a diagnosis of autism, 3 to 56 years of age. Analysis showed a significant correlation between the different…

  15. CORRELATION AND REGRESSION

    EPA Science Inventory

    Webcast entitled Statistical Tools for Making Sense of Data, by the National Nutrient Criteria Support Center, N-STEPS (Nutrients-Scientific Technical Exchange Partnership. The section "Correlation and Regression" provides an overview of these two techniques in the context of nut...

  16. Multivariate Intraclass Correlation.

    ERIC Educational Resources Information Center

    Wiley, David E.; Hawkes, Thomas H.

    This paper is an explication of a statistical model which will permit an interpretable intraclass correlation coefficient that is negative, and a generalized extension of that model to cover a multivariate problem. The methodological problem has its practical roots in an attempt to find a statistic which could indicate the degree of similarity or…

  17. Neuroanatomical Correlates of Intelligence

    ERIC Educational Resources Information Center

    Luders, Eileen; Narr, Katherine L.; Thompson, Paul M.; Toga, Arthur W.

    2009-01-01

    With the advancement of image acquisition and analysis methods in recent decades, unique opportunities have emerged to study the neuroanatomical correlates of intelligence. Traditional approaches examining global measures have been complemented by insights from more regional analyses based on pre-defined areas. Newer state-of-the-art approaches…

  18. Correlates of School Stress.

    ERIC Educational Resources Information Center

    Matthews, Doris B.

    As part of a continuing series of research studies on stress in schools, this study examined the construct validity of peripheral temperature at the fingertips as a measure of school stress. Measurements were made in classes selected at random from 11 volunteer schools in South Carolina. Three types of correlational studies were undertaken: (1)…

  19. Correlates of Adolescent Parenting.

    ERIC Educational Resources Information Center

    Reis, Janet S.; Herz, Elicia J.

    1987-01-01

    Studied correlates of teenage parenting in self-selected sample of 177 teenage parents. Parental race, punitive attitudes toward child rearing, and parental age were statistically significant predictors of total Home Observation for Measurement of the Environment scores. Older, white adolescent mothers with less punitive attitudes toward child…

  20. HIM Correlational Study

    ERIC Educational Resources Information Center

    Powell, Evan R.

    1977-01-01

    This study uses two methods of analysis to examine the degree to which items within the cells of the Hill Interaction Matrix correlate. It is found that the table of specifications does not hold up. But the author recommends caution in interpreting this finding. (Author/BP)

  1. CMB Lensing Cross Correlations

    NASA Astrophysics Data System (ADS)

    Bleem, Lindsey

    2014-03-01

    A new generation of experiments designed to conduct high-resolution, low-noise observations of the Cosmic Microwave Background (CMB)--including ACTpol, Planck, POLARBEAR and SPTpol--are producing exquisite measurements of the gravitational lensing of the CMB. Such measurements, covering large fractions of the sky, provide detailed maps of the projected mass distribution extending to the surface of the CMB's last scattering. Concurrently, a large number of deep, wide-area imaging and spectroscopic surveys (e.g., the Dark Energy Survey (DES),WISE all-sky survey, Subaru HyperSuprimeCam Survey, LSST, MS-DESI, BigBoss, etc.) are, or will soon be, providing maps of the distribution of galaxies in the Universe. Correlations of such tracer populations with lensing data allows new probes of where and how galaxies form in the dark matter skeleton of the Universe. Recent correlations of maps of galaxy and quasar densities with lensing convergence maps have produced significant measurements of galaxy bias. The near-term prospect for improvements in such measurements is notable as more precise lensing data from CMB polarization experiments will help to break cosmological and astrophysical parameter degeneracies. Work by the Planck, SPT, and POLARBEAR collaborations has also focused on the correlation of the Cosmic Infrared Background (CIB) with CMB lensing convergence maps. This correlation is particularly strong as the redshifts of the CIB and CMB lensing kernel are well matched. Such correlations probe high-redshift structure, constraining models of star-formation and the characteristic mass scale for halos hosting CIB galaxies and have also been used to demonstrate the first detection of CMB B-mode polarization--an important milestone in CMB observations. Finally, combining galaxy number density, cosmic shear and CMB lensing maps has the potential to provide valuable systematic tests for upcoming cosmological results from large optical surveys such as LSST.

  2. Multi baseline Grid Software Correlator

    NASA Astrophysics Data System (ADS)

    Moritaka, Kimura; Nakajima, Junichi; Kondo, Tetsuro

    Software VLBI correlation is regarded as a solution for next generation VLBI. With a flexibility of the software correlation programming, appropriate scientific correlations by scientists are possible as well as the post processing. As the first experiment to handle Gbps VLBI data, multi baseline Grid correlator have been developing at CRL. The performance of software correlation adopted multi CPUs, SIMD architectures and Grid computing technology has nearly reached hardware correlator performance.

  3. Correlators in nontrivial backgrounds

    SciTech Connect

    Mello Koch, Robert de; Ives, Norman; Stephanou, Michael

    2009-01-15

    Operators in N=4 super Yang-Mills theory with an R-charge of O(N{sup 2}) are dual to backgrounds which are asymtotically AdS{sub 5}xS{sup 5}. In this article we develop efficient techniques that allow the computation of correlation functions in these backgrounds. We find that (i) contractions between fields in the string words and fields in the operator creating the background are the field theory accounting of the new geometry, (ii) correlation functions of probes in these backgrounds are given by the free field theory contractions but with rescaled propagators and (iii) in these backgrounds there are no open string excitations with their special end point interactions; we have only closed string excitations.

  4. Correlations and Ostwald ripening

    NASA Technical Reports Server (NTRS)

    Marder, M.

    1987-01-01

    A previously developed model (Weins and Cahn, 1973) describing the growth of spheres of a second phase in metal alloys (Ostwald coarsening) is slightly modified to make it possible to study the complete time evolution of the system rather than simply the late-stage scaling behavior. Closed equations are obtained which describe the time evolution of two-particle correlations in the system. The development of the correlations is analyzed, and simpler expressions are found and solved numerically. The results are compared with experimental data for different systems (e.g., Ni-Al, Ni-Cr-Al, Co-Ni-Cr-Ti, Cu-Co, and MgO-Fe), alternate methods, and existing theories.

  5. Digital demodulator-correlator

    NASA Technical Reports Server (NTRS)

    Layland, J. W.; Martin, W. L.; Zygielbaum, A. I.; Goldstein, R. M.; Hubbard, W. P. (Inventor)

    1978-01-01

    An apparatus for demodulation and correlation of a code modulated 10 MHz signal is presented. The apparatus is comprised of a sample and hold analog-to-digital converter synchronized by a frequency coherent 40 MHz pulse to obtain four evenly spaced samples of each of the signal. Each sample is added or subtracted to or from one of four accumulators to or from the separate sums. The correlation functions are then computed. As a further feature of the invention, multipliers are each multiplied by a squarewave chopper signal having a period that is long relative to the period of the received signal to foreclose contamination of the received signal by leakage from either of the other two terms of the multipliers.

  6. Correlation dimension Wonderland theorems

    NASA Astrophysics Data System (ADS)

    Carvalho, Silas L.; de Oliveira, César R.

    2016-06-01

    Existence of generic sets of self-adjoint operators, related to correlation dimensions of spectral measures, is investigated in separable Hilbert spaces. Typical results say that, given an orthonormal basis, the set of operators whose corresponding spectral measures are both 0-lower and 1-upper correlation dimensional is generic. The proofs rely on details of the relations among Fourier transform of spectral measures and Hausdorff and packing measures on the real line. Then such results are naturally combined with the Wonderland theorem. Applications are to classes of discrete one-dimensional Schrödinger operators and general (bounded) self-adjoint operators as well. Physical consequences include a proof of exotic dynamical behavior of singular continuous spectrum in some settings.

  7. Correlation, coherence and context

    NASA Astrophysics Data System (ADS)

    Eberly, J. H.

    2016-08-01

    The modern theory of coherence is based on correlation functions. A generic example could be written < {{V}\\ast}≤ft({{t}1}\\right)V≤ft({{t}2}\\right)> , denoting an average of products of the values of a signal V(t) at two specified times. Here we infer that t is a degree of freedom that the signal depends on. Typically, physical variables depend on more than one degree of freedom, and recognition of this has prompted attention to some interesting questions for the correlation functions and the several coherences that can be attributed to the same optical field. We examine some of the questions arising from the standpoint of experimental contexts. Degree of polarizability and degree of entanglement (classical non-separability) can serve as starting points for quantitative assignments.

  8. Correlative pediatric imaging

    SciTech Connect

    Garty, I.; Delbeke, D.; Sandler, M.P.

    1989-01-01

    Nuclear medicine, ultrasound, and magnetic resonance imaging (MRI) are considered ideal imaging modalities for pediatric patients. The future is even more promising for pediatric imaging with the development of newer and improved radiopharmaceuticals, instrumentation and diagnostic modalities such as positron emission tomography, labeled monoclonal antibodies, and faster dynamic and contrast enhanced MRI methods. However, correlation of more conventional imaging modalities with nuclear medicine, ultrasound and MRI remain essential for optimal patient care. 43 references.

  9. Neural correlates of gratitude.

    PubMed

    Fox, Glenn R; Kaplan, Jonas; Damasio, Hanna; Damasio, Antonio

    2015-01-01

    Gratitude is an important aspect of human sociality, and is valued by religions and moral philosophies. It has been established that gratitude leads to benefits for both mental health and interpersonal relationships. It is thus important to elucidate the neurobiological correlates of gratitude, which are only now beginning to be investigated. To this end, we conducted an experiment during which we induced gratitude in participants while they underwent functional magnetic resonance imaging. We hypothesized that gratitude ratings would correlate with activity in brain regions associated with moral cognition, value judgment and theory of mind. The stimuli used to elicit gratitude were drawn from stories of survivors of the Holocaust, as many survivors report being sheltered by strangers or receiving lifesaving food and clothing, and having strong feelings of gratitude for such gifts. The participants were asked to place themselves in the context of the Holocaust and imagine what their own experience would feel like if they received such gifts. For each gift, they rated how grateful they felt. The results revealed that ratings of gratitude correlated with brain activity in the anterior cingulate cortex and medial prefrontal cortex, in support of our hypotheses. The results provide a window into the brain circuitry for moral cognition and positive emotion that accompanies the experience of benefitting from the goodwill of others. PMID:26483740

  10. Cots Correlator Platform

    NASA Astrophysics Data System (ADS)

    Schaaf, Kjeld; Overeem, Ruud

    2004-06-01

    Moore’s law is best exploited by using consumer market hardware. In particular, the gaming industry pushes the limit of processor performance thus reducing the cost per raw flop even faster than Moore’s law predicts. Next to the cost benefits of Common-Of-The-Shelf (COTS) processing resources, there is a rapidly growing experience pool in cluster based processing. The typical Beowulf cluster of PC’s supercomputers are well known. Multiple examples exists of specialised cluster computers based on more advanced server nodes or even gaming stations. All these cluster machines build upon the same knowledge about cluster software management, scheduling, middleware libraries and mathematical libraries. In this study, we have integrated COTS processing resources and cluster nodes into a very high performance processing platform suitable for streaming data applications, in particular to implement a correlator. The required processing power for the correlator in modern radio telescopes is in the range of the larger supercomputers, which motivates the usage of supercomputer technology. Raw processing power is provided by graphical processors and is combined with an Infiniband host bus adapter with integrated data stream handling logic. With this processing platform a scalable correlator can be built with continuously growing processing power at consumer market prices.

  11. Neural correlates of gratitude

    PubMed Central

    Fox, Glenn R.; Kaplan, Jonas; Damasio, Hanna; Damasio, Antonio

    2015-01-01

    Gratitude is an important aspect of human sociality, and is valued by religions and moral philosophies. It has been established that gratitude leads to benefits for both mental health and interpersonal relationships. It is thus important to elucidate the neurobiological correlates of gratitude, which are only now beginning to be investigated. To this end, we conducted an experiment during which we induced gratitude in participants while they underwent functional magnetic resonance imaging. We hypothesized that gratitude ratings would correlate with activity in brain regions associated with moral cognition, value judgment and theory of mind. The stimuli used to elicit gratitude were drawn from stories of survivors of the Holocaust, as many survivors report being sheltered by strangers or receiving lifesaving food and clothing, and having strong feelings of gratitude for such gifts. The participants were asked to place themselves in the context of the Holocaust and imagine what their own experience would feel like if they received such gifts. For each gift, they rated how grateful they felt. The results revealed that ratings of gratitude correlated with brain activity in the anterior cingulate cortex and medial prefrontal cortex, in support of our hypotheses. The results provide a window into the brain circuitry for moral cognition and positive emotion that accompanies the experience of benefitting from the goodwill of others. PMID:26483740

  12. Energy calibration via correlation

    NASA Astrophysics Data System (ADS)

    Maier, Daniel; Limousin, Olivier

    2016-03-01

    The main task of an energy calibration is to find a relation between pulse-height values and the corresponding energies. Doing this for each pulse-height channel individually requires an elaborated input spectrum with an excellent counting statistics and a sophisticated data analysis. This work presents an easy to handle energy calibration process which can operate reliably on calibration measurements with low counting statistics. The method uses a parameter based model for the energy calibration and concludes on the optimal parameters of the model by finding the best correlation between the measured pulse-height spectrum and multiple synthetic pulse-height spectra which are constructed with different sets of calibration parameters. A CdTe-based semiconductor detector and the line emissions of an 241Am source were used to test the performance of the correlation method in terms of systematic calibration errors for different counting statistics. Up to energies of 60 keV systematic errors were measured to be less than ~ 0.1 keV. Energy calibration via correlation can be applied to any kind of calibration spectra and shows a robust behavior at low counting statistics. It enables a fast and accurate calibration that can be used to monitor the spectroscopic properties of a detector system in near realtime.

  13. Correlation Algorithm Library

    2013-08-02

    CorAL is a software Library designed to aid in the analysis of femtoscipic data. Femtoscopic data are a class of measured quantities used in heavy-ion collisions to characterize particle emitting source sizes. The most common type of this data is two-particle correleations induced by the Hanbury-Brown/Twiss (HBT) Effect, but can also include correlations induced by final-state interactions between pairs of emitted particles in a heavy-ion collision. Because heavy-ion collisions are complex many particle systems, modelingmore » hydrodynamical models or hybrid techniques. Using the CRAB module, CorAL can turn the output from these models into something that can be directley compared to experimental data. CorAL can also take the raw experimentally measured correlation functions and image them by inverting the Koonin-Pratt equation to extract the space-time emission profile of the particle emitting source. This source function can be further analyzed or directly compared to theoretical calculations.« less

  14. Correlation Algorithm Library

    SciTech Connect

    2013-08-02

    CorAL is a software Library designed to aid in the analysis of femtoscipic data. Femtoscopic data are a class of measured quantities used in heavy-ion collisions to characterize particle emitting source sizes. The most common type of this data is two-particle correleations induced by the Hanbury-Brown/Twiss (HBT) Effect, but can also include correlations induced by final-state interactions between pairs of emitted particles in a heavy-ion collision. Because heavy-ion collisions are complex many particle systems, modeling hydrodynamical models or hybrid techniques. Using the CRAB module, CorAL can turn the output from these models into something that can be directley compared to experimental data. CorAL can also take the raw experimentally measured correlation functions and image them by inverting the Koonin-Pratt equation to extract the space-time emission profile of the particle emitting source. This source function can be further analyzed or directly compared to theoretical calculations.

  15. Variable angle correlation spectroscopy

    SciTech Connect

    Lee, Y K

    1994-05-01

    In this dissertation, a novel nuclear magnetic resonance (NMR) technique, variable angle correlation spectroscopy (VACSY) is described and demonstrated with {sup 13}C nuclei in rapidly rotating samples. These experiments focus on one of the basic problems in solid state NMR: how to extract the wealth of information contained in the anisotropic component of the NMR signal while still maintaining spectral resolution. Analysis of the anisotropic spectral patterns from poly-crystalline systems reveal information concerning molecular structure and dynamics, yet in all but the simplest of systems, the overlap of spectral patterns from chemically distinct sites renders the spectral analysis difficult if not impossible. One solution to this problem is to perform multi-dimensional experiments where the high-resolution, isotropic spectrum in one dimension is correlated with the anisotropic spectral patterns in the other dimensions. The VACSY technique incorporates the angle between the spinner axis and the static magnetic field as an experimental parameter that may be incremented during the course of the experiment to help correlate the isotropic and anisotropic components of the spectrum. The two-dimensional version of the VACSY experiments is used to extract the chemical shift anisotropy tensor values from multi-site organic molecules, study molecular dynamics in the intermediate time regime, and to examine the ordering properties of partially oriented samples. The VACSY technique is then extended to three-dimensional experiments to study slow molecular reorientations in a multi-site polymer system.

  16. Bootstrapped Deattenuated Correlation: Nonnormal Distributions

    ERIC Educational Resources Information Center

    Padilla, Miguel A.; Veprinsky, Anna

    2014-01-01

    Correlation attenuation due to measurement error and a corresponding correction, the deattenuated correlation, have been known for over a century. Nevertheless, the deattenuated correlation remains underutilized. A few studies in recent years have investigated factors affecting the deattenuated correlation, and a couple of them provide alternative…

  17. Digital Image Correlation Engine

    SciTech Connect

    Turner, Dan; Crozier, Paul; Reu, Phil

    2015-10-06

    DICe is an open source digital image correlation (DIC) tool intended for use as a module in an external application or as a standalone analysis code. It's primary capability is computing full –field displacements and strains from sequences of digital These images are typically of a material sample undergoing a materials characterization experiment, but DICe is also useful for other applications (for example, trajectory tracking). DICe is machine portable (Windows, Linux and Mac) and can be effectively deployed on a high performance computing platform. Capabilities from DICe can be invoked through a library interface, via source code integration of DICe classes or through a graphical user interface.

  18. Correlative Measurements Program

    NASA Technical Reports Server (NTRS)

    Parsons, C. L.

    1988-01-01

    The GSFC Correlative Measurements Program at the Wallops Flight Facility was represented on the Satellite/Satellite Intercomparisons Working Group. The Correlative Measurements Program uses the Rocket Ozonesonde (ROCOZ-A) and the Electrochemical Concentration Cell (ECC) balloon borne ozonesonde to measure the vertical profile of ozone amount in the atmosphere. The balloon work is described in a separate report. The ROCOZ-A instrument was used for many years to provide in situ truth data for various satellite ozone measuring systems, such as SBUV on Nimbus-7, SAGE-II, SBUV-II on the NOAA series of polar orbiting satellites, SME, LIMS, etc. The particular data sets of interest to the Ozone Trends Panel Working Group were collected at Natal, Brazil. The major results produced for and used by the Ozone Trends Panel are shown. The ROCOZ-A average ozone density profile is plotted versus altitude on the left. ECC ozonesondes were used for the portion of the profile below 20 km, the lower limit for ROCOZ-A. The difference between SAGE-II and ROCOZ-A average density profiles is shown.

  19. Grayscale Optical Correlator Workbench

    NASA Technical Reports Server (NTRS)

    Hanan, Jay; Zhou, Hanying; Chao, Tien-Hsin

    2006-01-01

    Grayscale Optical Correlator Workbench (GOCWB) is a computer program for use in automatic target recognition (ATR). GOCWB performs ATR with an accurate simulation of a hardware grayscale optical correlator (GOC). This simulation is performed to test filters that are created in GOCWB. Thus, GOCWB can be used as a stand-alone ATR software tool or in combination with GOC hardware for building (target training), testing, and optimization of filters. The software is divided into three main parts, denoted filter, testing, and training. The training part is used for assembling training images as input to a filter. The filter part is used for combining training images into a filter and optimizing that filter. The testing part is used for testing new filters and for general simulation of GOC output. The current version of GOCWB relies on the mathematical software tools from MATLAB binaries for performing matrix operations and fast Fourier transforms. Optimization of filters is based on an algorithm, known as OT-MACH, in which variables specified by the user are parameterized and the best filter is selected on the basis of an average result for correct identification of targets in multiple test images.

  20. Sensitivity enhanced (14)N/(14)N correlations to probe inter-beta-sheet interactions using fast magic angle spinning solid-state NMR in biological solids.

    PubMed

    Pandey, Manoj Kumar; Amoureux, Jean-Paul; Asakura, Tetsuo; Nishiyama, Yusuke

    2016-08-10

    (14)N/(14)N correlations are vital for structural studies of solid samples, especially those in which (15)N isotopic enrichment is challenging, time-consuming and expensive. Although (14)N nuclei have high isotopic abundance (99.6%), there are inherent difficulties in observing (14)N/(14)N correlations due to limited resolution and sensitivity related to: (i) low (14)N gyromagnetic ratio (γ), (ii) large (14)N quadrupolar couplings, (iii) integer (14)N spin quantum number (I = 1), and (iv) very weak (14)N-(14)N dipolar couplings. Previously, we demonstrated a proton-detected 3D (14)N/(14)N/(1)H correlation experiment at fast magic angle spinning (MAS) on l-histidine·HCl·H2O utilizing a through-bond (J) and residual dipolar-splitting (RDS) based heteronuclear multiple quantum correlation (J-HMQC) sequence mediated through (1)H/(1)H radio-frequency driven recoupling (RFDR). As an extension of our previous work, in this study we show the utility of dipolar-based HMQC (D-HMQC) in combination with (1)H/(1)H RFDR mixing to obtain sensitivity enhanced (14)N/(14)N correlations in more complex biological solids such as a glycyl-l-alanine (Gly-l-Ala) dipeptide, and parallel (P) and antiparallel (AP) β-strand alanine tripeptides (P-(Ala)3 and AP-(Ala)3, respectively). These systems highlight the mandatory necessity of 3D (14)N/(14)N/(1)H measurements to get (14)N/(14)N correlations when the amide proton resonances are overlapped. Moreover, the application of long selective (14)N pulses, instead of short hard ones, is shown to improve the sensitivity. Globally, we demonstrate that replacing J-scalar with dipolar interaction and hard- with selective-(14)N pulses allows gaining a factor of ca. 360 in experimental time. On the basis of intermolecular NH/NH distances and (14)N quadrupolar tensor orientations, (14)N/(14)N correlations are effectively utilized to make a clear distinction between the parallel and antiparallel arrangements of the β-strands in (Ala)3 through the

  1. Digital Image Correlation Engine

    2015-10-06

    DICe is an open source digital image correlation (DIC) tool intended for use as a module in an external application or as a standalone analysis code. It's primary capability is computing full –field displacements and strains from sequences of digital These images are typically of a material sample undergoing a materials characterization experiment, but DICe is also useful for other applications (for example, trajectory tracking). DICe is machine portable (Windows, Linux and Mac) and canmore » be effectively deployed on a high performance computing platform. Capabilities from DICe can be invoked through a library interface, via source code integration of DICe classes or through a graphical user interface.« less

  2. Strongly correlated electronic materials

    SciTech Connect

    Bedell, K.; Albers, R.; Balatsky, A.; Bishop, A.; Bonca, J.; Gubernatis, J.; Gulasci, M.; Silver, R.; Trugman, S.

    1996-04-01

    This is the final report of a 3-year project. Novel electronic materials characterized by strong electronic correlations display a number of unexpected, often extraordinary, properties. These are likely to play a major role in purpose-specific high-technology electronic materials of the future developed for electronic, magnetic, and optical applications. This project sought to develop predictive control of the novel properties by formulating, solving and applying many-body models for the underlying microscopic physics. This predictive control required the development of new analytical and numerical many-body techniques and strategies for materials of varying strengths of interactions, dimensionality and geometry. Results are compared with experiment on classes of novel materials, and the robust techniques are used to predict additional properties and motivate key additional experiments.

  3. Flatbands under Correlated Perturbations

    NASA Astrophysics Data System (ADS)

    Bodyfelt, Joshua D.; Leykam, Daniel; Danieli, Carlo; Yu, Xiaoquan; Flach, Sergej

    2014-12-01

    Flatband networks are characterized by the coexistence of dispersive and flatbands. Flatbands (FBs) are generated by compact localized eigenstates (CLSs) with local network symmetries, based on destructive interference. Correlated disorder and quasiperiodic potentials hybridize CLSs without additional renormalization, yet with surprising consequences: (i) states are expelled from the FB energy EFB, (ii) the localization length of eigenstates vanishes as ξ ˜1 /ln (E -EFB) , (iii) the density of states diverges logarithmically (particle-hole symmetry) and algebraically (no particle-hole symmetry), and (iv) mobility edge curves show algebraic singularities at EFB . Our analytical results are based on perturbative expansions of the CLSs and supported by numerical data in one and two lattice dimensions.

  4. Flatbands under correlated perturbations.

    PubMed

    Bodyfelt, Joshua D; Leykam, Daniel; Danieli, Carlo; Yu, Xiaoquan; Flach, Sergej

    2014-12-01

    Flatband networks are characterized by the coexistence of dispersive and flatbands. Flatbands (FBs) are generated by compact localized eigenstates (CLSs) with local network symmetries, based on destructive interference. Correlated disorder and quasiperiodic potentials hybridize CLSs without additional renormalization, yet with surprising consequences: (i) states are expelled from the FB energy E_{FB}, (ii) the localization length of eigenstates vanishes as ξ∼1/ln(E-E_{FB}), (iii) the density of states diverges logarithmically (particle-hole symmetry) and algebraically (no particle-hole symmetry), and (iv) mobility edge curves show algebraic singularities at E_{FB}. Our analytical results are based on perturbative expansions of the CLSs and supported by numerical data in one and two lattice dimensions. PMID:25526142

  5. Paths correlation matrix.

    PubMed

    Qian, Weixian; Zhou, Xiaojun; Lu, Yingcheng; Xu, Jiang

    2015-09-15

    Both the Jones and Mueller matrices encounter difficulties when physically modeling mixed materials or rough surfaces due to the complexity of light-matter interactions. To address these issues, we derived a matrix called the paths correlation matrix (PCM), which is a probabilistic mixture of Jones matrices of every light propagation path. Because PCM is related to actual light propagation paths, it is well suited for physical modeling. Experiments were performed, and the reflection PCM of a mixture of polypropylene and graphite was measured. The PCM of the mixed sample was accurately decomposed into pure polypropylene's single reflection, pure graphite's single reflection, and depolarization caused by multiple reflections, which is consistent with the theoretical derivation. Reflection parameters of rough surface can be calculated from PCM decomposition, and the results fit well with the theoretical calculations provided by the Fresnel equations. These theoretical and experimental analyses verify that PCM is an efficient way to physically model light-matter interactions. PMID:26371930

  6. Correlation monitor materials

    SciTech Connect

    Corwin, W.R.

    1995-10-01

    This task has been established with the explicit purpose of ensuring the continued availability of the pedigreed and extremely well-characterized material now required for inclusion in all additional and future surveillance capsules in commercial light-water reactors. During this reporting period, concrete was poured and pallets storage racks were installed to provide adequate room for the storage of the correlation monitor material being transferred from its location at the Y-12 Plant to its archival storage location at ORNL. The racks came from surplus material storage at ORNL and hence were obtained at no cost to the HSSI Program. Inquiries into cost-effective means of sheltering the blocks of correlation monitor materials from further weather-related deteriorization were initiated. The most likely approach would be to procure a turn-key sheet metal building installed over the storage racks by an outside contractor to minimize costs. Most of the material has now been transferred from Y-12 to the ORNL storage area. It has been repositioned on new storage pallets and placed into the storage racks, An update of the detailed material inventory was initiated to ascertain the revised location of all blocks. Pieces of HSST plate O3 were distributed to participants in the ASTM cross-comparison exercise on subsize specimen testing technology. The use of the HSST O3 will provide for data from the many varieties of tests to be performed to be compared with the standardized data previously developed. The testing techniques will focus on ways to measure transition temperature and fracture toughness.

  7. Understanding Correlations: Two Computer Exercises.

    ERIC Educational Resources Information Center

    Goldstein, Miriam D.; Strube, Michael J.

    1995-01-01

    Describes two QuickBASIC programs that provide students direct experience with interpreting correlation scatter-plots. Maintains that the programs can be used in classroom exercises to highlight factors that influence the size of a Pearson correlation coefficient. (CFR)

  8. Magnitude correlations in global seismicity

    SciTech Connect

    Sarlis, N. V.

    2011-08-15

    By employing natural time analysis, we analyze the worldwide seismicity and study the existence of correlations between earthquake magnitudes. We find that global seismicity exhibits nontrivial magnitude correlations for earthquake magnitudes greater than M{sub w}6.5.

  9. Standard Errors for Matrix Correlations.

    ERIC Educational Resources Information Center

    Ogasawara, Haruhiko

    1999-01-01

    Derives the asymptotic standard errors and intercorrelations for several matrix correlations assuming multivariate normality for manifest variables and derives the asymptotic standard errors of the matrix correlations for two factor-loading matrices. (SLD)

  10. The 512-channel correlator controller

    NASA Technical Reports Server (NTRS)

    Brokl, S. S.

    1976-01-01

    A high-speed correlator for radio and radar observations was developed and a controller was designed so that the correlator could run automatically without computer intervention. The correlator controller assumes the role of bus master and keeps track of data and properly interrupts the computer at the end of the observation.

  11. Liquid-Crystal Optical Correlator

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang

    1989-01-01

    Optical correlator uses commercially-available liquid-crystal television (LCTV) screen as spatial light modulator. Correlations with this device done at video frame rates, making such operations as bar-code recognition possible at reasonable cost. With further development, such correlator useful in automation, robotic vision, and optical image processing.

  12. Estimating the Polyserial Correlation Coefficient.

    ERIC Educational Resources Information Center

    Bedrick, Edward J.; Breslin, Frederick C.

    1996-01-01

    Simple noniterative estimators of the polyserial correlation coefficient are developed by exploiting a general relationship between the polyserial correlation and the point polyserial correlation to give extensions of the biserial estimators of K. Pearson (1909), H. E. Brogden (1949), and F. M. Lord (1963) to the multicategory setting. (SLD)

  13. Lagged correlation networks

    NASA Astrophysics Data System (ADS)

    Curme, Chester

    Technological advances have provided scientists with large high-dimensional datasets that describe the behaviors of complex systems: from the statistics of energy levels in complex quantum systems, to the time-dependent transcription of genes, to price fluctuations among assets in a financial market. In this environment, where it may be difficult to infer the joint distribution of the data, network science has flourished as a way to gain insight into the structure and organization of such systems by focusing on pairwise interactions. This work focuses on a particular setting, in which a system is described by multivariate time series data. We consider time-lagged correlations among elements in this system, in such a way that the measured interactions among elements are asymmetric. Finally, we allow these interactions to be characteristically weak, so that statistical uncertainties may be important to consider when inferring the structure of the system. We introduce a methodology for constructing statistically validated networks to describe such a system, extend the methodology to accommodate interactions with a periodic component, and show how consideration of bipartite community structures in these networks can aid in the construction of robust statistical models. An example of such a system is a financial market, in which high frequency returns data may be used to describe contagion, or the spreading of shocks in price among assets. These data provide the experimental testing ground for our methodology. We study NYSE data from both the present day and one decade ago, examine the time scales over which the validated lagged correlation networks exist, and relate differences in the topological properties of the networks to an increasing economic efficiency. We uncover daily periodicities in the validated interactions, and relate our findings to explanations of the Epps Effect, an empirical phenomenon of financial time series. We also study bipartite community

  14. Self-assembly of highly luminescent heteronuclear coordination cages.

    PubMed

    Schmidt, Andrea; Hollering, Manuela; Han, Jiaying; Casini, Angela; Kühn, Fritz E

    2016-08-01

    Exo-functionalized Pd2L4 cage compounds with attached Ru(ii) pyridine complexes were prepared via coordination-driven self-assembly. Unlike most of the previously reported palladium(ii) cages, one of these metallocages exhibits an exceptionally high quantum yield of 66%. The presented approach is promising to obtain luminescent coordination complexes for various applications. PMID:27436541

  15. Facile Separation of Regioisomeric Compounds by a Heteronuclear Organometallic Capsule.

    PubMed

    Zhang, Wen-Ying; Lin, Yue-Jian; Han, Ying-Feng; Jin, Guo-Xin

    2016-08-24

    Owing to the often-similar physical and chemical properties of structural isomers of organic molecules, large efforts have been made to develop efficient strategies to isolate specific isomers. However, facile separation of regioisomeric compounds remains difficult. Here we demonstrate a universal organometallic capsule in which two silver centers are rigidly separated from each other by two tetranuclear [Rh4] pyramidal frustums, which selectively encapsulate a specific isomer from mixtures. Not only is the present heterometallic capsule suitable as a host for the encapsulation of a series of aromatic compounds, but also the receptor shows widely differing specificity for the various isomers. Direct experimental evidence is provided for the selective encapsulation of a series of para (p)-disubstituted benzene derivatives, such as p-xylene, p-dichlorobenzene, p-dibromobenzene, and p-diiodobenzene. The size and shape matching, as well as the Ag-π interactions, are the main forces governing the extent of molecular recognition. The encapsulated guest p-xylene can be released by using the solid-liquid solvent washing strategy, and the other guest molecules are easily liberated by using light stimulus. PMID:27463561

  16. Correlational effect size benchmarks.

    PubMed

    Bosco, Frank A; Aguinis, Herman; Singh, Kulraj; Field, James G; Pierce, Charles A

    2015-03-01

    Effect size information is essential for the scientific enterprise and plays an increasingly central role in the scientific process. We extracted 147,328 correlations and developed a hierarchical taxonomy of variables reported in Journal of Applied Psychology and Personnel Psychology from 1980 to 2010 to produce empirical effect size benchmarks at the omnibus level, for 20 common research domains, and for an even finer grained level of generality. Results indicate that the usual interpretation and classification of effect sizes as small, medium, and large bear almost no resemblance to findings in the field, because distributions of effect sizes exhibit tertile partitions at values approximately one-half to one-third those intuited by Cohen (1988). Our results offer information that can be used for research planning and design purposes, such as producing better informed non-nil hypotheses and estimating statistical power and planning sample size accordingly. We also offer information useful for understanding the relative importance of the effect sizes found in a particular study in relationship to others and which research domains have advanced more or less, given that larger effect sizes indicate a better understanding of a phenomenon. Also, our study offers information about research domains for which the investigation of moderating effects may be more fruitful and provide information that is likely to facilitate the implementation of Bayesian analysis. Finally, our study offers information that practitioners can use to evaluate the relative effectiveness of various types of interventions. PMID:25314367

  17. Spectral correlates lexical prosody

    NASA Astrophysics Data System (ADS)

    Okobi, Anthony

    2005-09-01

    The purpose of this study is to derive a quantitative acoustic model of lexical-prosodic characteristics of stressed vowels by looking at several spectral properties associated with the articulatory mechanisms used in speech production. Native speakers of American English were asked to name disyllabic visualizable nouns. Words containing liquids or glides were not used in this study because of their effect on the spectra of adjacent vowels. Subjects uttered short phrases in which the target word was pitch accent half of the time and unaccented the other half. Results show that within the category of full vowels, unstressed and stressed vowels can be distinguished by syllable/vowel durations and spectral tilt. Spectral tilt (SpT) is an acoustic measure related to the degree of glottal spreading. Stressed full vowels had longer duration and less SpT. Distinction between unaccented and accented stressed vowels can be made by amplitude of voicing (AV), F0 (pitch), and intensity contour differences. Accented stressed vowels have higher pitch, and greater AV and intensity. These results suggest that there are acoustic correlates to lexical stress that can be used to determine the stressed syllable of a word, regardless of whether or not it is pitch accented. [Work supported by NIH T32-DC00038.

  18. Direct measure of quantum correlation

    SciTech Connect

    Yu, Chang-shui; Zhao, Haiqing

    2011-12-15

    The quantumness of the correlation known as quantum correlation is usually measured by quantum discord. So far various quantum discords can be roughly understood as indirect measure by some special discrepancy of two quantities. We present a direct measure of quantum correlation by revealing the difference between the structures of classically and quantum correlated states. Our measure explicitly includes the contributions of the inseparability and local nonorthogonality of the eigenvectors of a density matrix. Besides its relatively easy computability, our measure can provide a unified understanding of quantum correlation of all the present versions.

  19. Allowing for Correlations between Correlations in Random-Effects Meta-Analysis of Correlation Matrices

    ERIC Educational Resources Information Center

    Prevost, A. Toby; Mason, Dan; Griffin, Simon; Kinmonth, Ann-Louise; Sutton, Stephen; Spiegelhalter, David

    2007-01-01

    Practical meta-analysis of correlation matrices generally ignores covariances (and hence correlations) between correlation estimates. The authors consider various methods for allowing for covariances, including generalized least squares, maximum marginal likelihood, and Bayesian approaches, illustrated using a 6-dimensional response in a series of…

  20. SAW correlator spread spectrum receiver

    DOEpatents

    Brocato, Robert W

    2014-04-01

    A surface acoustic wave (SAW) correlator spread-spectrum (SS) receiver is disclosed which utilizes a first demodulation stage with a chip length n and a second demodulation stage with a chip length m to decode a transmitted SS signal having a code length l=n.times.m which can be very long (e.g. up to 2000 chips or more). The first demodulation stage utilizes a pair of SAW correlators which demodulate the SS signal to generate an appropriate code sequence at an intermediate frequency which can then be fed into the second demodulation stage which can be formed from another SAW correlator, or by a digital correlator. A compound SAW correlator comprising two input transducers and a single output transducer is also disclosed which can be used to form the SAW correlator SS receiver, or for use in processing long code length signals.

  1. Closed sets of nonlocal correlations

    SciTech Connect

    Allcock, Jonathan; Linden, Noah; Brunner, Nicolas; Popescu, Sandu; Skrzypczyk, Paul; Vertesi, Tamas

    2009-12-15

    We present a fundamental concept - closed sets of correlations - for studying nonlocal correlations. We argue that sets of correlations corresponding to information-theoretic principles, or more generally to consistent physical theories, must be closed under a natural set of operations. Hence, studying the closure of sets of correlations gives insight into which information-theoretic principles are genuinely different, and which are ultimately equivalent. This concept also has implications for understanding why quantum nonlocality is limited, and for finding constraints on physical theories beyond quantum mechanics.

  2. Why Are Experts Correlated? Decomposing Correlations between Judges

    ERIC Educational Resources Information Center

    Broomell, Stephen B.; Budescu, David V.

    2009-01-01

    We derive an analytic model of the inter-judge correlation as a function of five underlying parameters. Inter-cue correlation and the number of cues capture our assumptions about the environment, while differentiations between cues, the weights attached to the cues, and (un)reliability describe assumptions about the judges. We study the relative…

  3. Canonical Correlation: Terms and Descriptions.

    ERIC Educational Resources Information Center

    Pugh, Richard C.; Hu, Yuehluen

    The use of terms to describe and interpret results from canonical correlation analysis has been inconsistent across research studies. This study assembled the terminology related to the use and interpretation of canonical correlation analysis from research articles, textbooks, and computer manuals. Research articles using canonical correlation…

  4. Correlation Weights in Multiple Regression

    ERIC Educational Resources Information Center

    Waller, Niels G.; Jones, Jeff A.

    2010-01-01

    A general theory on the use of correlation weights in linear prediction has yet to be proposed. In this paper we take initial steps in developing such a theory by describing the conditions under which correlation weights perform well in population regression models. Using OLS weights as a comparison, we define cases in which the two weighting…

  5. Regularized Generalized Canonical Correlation Analysis

    ERIC Educational Resources Information Center

    Tenenhaus, Arthur; Tenenhaus, Michel

    2011-01-01

    Regularized generalized canonical correlation analysis (RGCCA) is a generalization of regularized canonical correlation analysis to three or more sets of variables. It constitutes a general framework for many multi-block data analysis methods. It combines the power of multi-block data analysis methods (maximization of well identified criteria) and…

  6. Optical Correlator Performs Novelty Filtering

    NASA Technical Reports Server (NTRS)

    Liu, Duncan Tsuen-Hsi; Chao, Tien-Hsin; Cheng, Li-Jen

    1994-01-01

    Experimental real-time optical correlator performs correlation and novelty filtering in photorefractive crystal. Crystal oriented enabling cross-polarization diffraction: together with polarizing beam splitter, increases signal-to-noise ratio. Laser and optical components expand, collimate, and divide laser beam.

  7. Polarization correlations of Dirac particles

    SciTech Connect

    Caban, Pawel; Dziegielewska, Agnieszka; Karmazyn, Anna; Okrasa, Malgorzata

    2010-03-15

    We calculate the polarization correlation function in the Einstein-Podolsky-Rosen-type experiments with relativistic spin-1/2 particles. This function depends monotonically on the particle momenta. Moreover, we also show that the polarization correlation function violates the Clauser-Horn-Shimony-Holt inequality and the degree of this violation can depend on the particle momenta and the motion of observers.

  8. Correlation filters for orientation estimation

    NASA Technical Reports Server (NTRS)

    Kumar, B. V. K. Vijaya; Lee, Andrew J.; Connelly, James M.

    1988-01-01

    An important task in many vision applications is that of rapidly estimating the orientation of an object with respect to some frame of reference. Because of their speed and parallel processing capabilities, optical correlators should prove valuable in this application. This paper considers two algorithms for object orientation estimation based on optical correlations and presents some initial simulation results.

  9. Personality Correlates of Polydrug Abuse.

    ERIC Educational Resources Information Center

    Kilpatrick, Dean G.; And Others

    Although the personality correlates of heroin addiction, LSD use, and marijuana smoking have been frequently investigated, relatively few data are available to describe the personality or lifestyle variables correlated with the pattern of polydrug abuse. In an attempt to gather such information, 17 polydrug users, selected from a group of 224…

  10. Proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-10-28

    A proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of {sup 13}C-{sup 1}H connectivities, and proximities of {sup 13}C-{sup 1}H and {sup 1}H-{sup 1}H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including {sup 1}H-{sup 1}H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) {sup 1}H/{sup 1}H and 2D {sup 13}C/{sup 1}H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of {sup 1}H-{sup 1}H proximity and {sup 13}C-{sup 1}H connectivity. In addition, the 2D (F1/F2) {sup 1}H/{sup 13}C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of {sup 1}H-{sup 1}H dipolar couplings, enables the measurement of proximities between {sup 13}C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of {sup 1}H-{sup 1}H-{sup 13}C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H{sub 2}O ⋅ HCl demonstrate the efficiency of the 3D experiment.

  11. Correlation transfer: Development and application

    NASA Astrophysics Data System (ADS)

    Dougherty, R. L.; Ackerson, B. J.; Reguigui, N. M.; Dorri-Nowkoorani, F.; Nobbmann, U.

    1994-12-01

    A correlation transfer equation for multiple scattering of light through suspensions of diffusing particles is derived from multiple scattering theory. Because of the formal similarity between the correlation equation and the radiative transfer equation, radiative transport solution techniques are applied to obtain solutions for the field correlation function in isotropic one-dimensional media. A three-term Legendre expansion for the angularly dependent single scattering function (g(sup 1)) in the correlation integral equation is used to obtain approximate numerical solutions for the correlation function. Graphical results are presented for the correlation in both the forward and backward directions for a finite medium and for backscattering in the case of an infinite medium. Experimental results are also presented and they show improved agreement with the three-term Legendre expansion of g(sup 1) as compared to the one or two-term expansions. Correlation transfer results are shown to agree well with both the diffusion limit and the single scattering limit predictions.

  12. 25 ns software correlator for photon and fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Magatti, Davide; Ferri, Fabio

    2003-02-01

    A 25 ns time resolution, multi-tau software correlator developed in LABVIEW based on the use of a standard photon counting unit, a fast timer/counter board (6602-PCI National Instrument) and a personal computer (PC) (1.5 GHz Pentium 4) is presented and quantitatively discussed. The correlator works by processing the stream of incoming data in parallel according to two different algorithms: For large lag times (τ⩾100 μs), a classical time-mode (TM) scheme, based on the measure of the number of pulses per time interval, is used; differently, for τ⩽100 μs a photon-mode (PM) scheme is adopted and the time sequence of the arrival times of the photon pulses is measured. By combining the two methods, we developed a system capable of working out correlation functions on line, in full real time for the TM correlator and partially in batch processing for the PM correlator. For the latter one, the duty cycle depends on the count rate of the incoming pulses, being ˜100% for count rates ⩽3×104 Hz, ˜15% at 105 Hz, and ˜1% at 106 Hz. For limitations imposed by the fairly small first-in, first-out (FIFO) buffer available on the counter board, the maximum count rate permissible for a proper functioning of the PM correlator is limited to ˜105 Hz. However, this limit can be removed by using a board with a deeper FIFO. Similarly, the 25 ns time resolution is only limited by maximum clock frequency available on the 6602-PCI and can be easily improved by using a faster clock. When tested on dilute solutions of calibrated latex spheres, the overall performances of the correlator appear to be comparable with those of commercial hardware correlators, but with several nontrivial advantages related to its flexibility, low cost, and easy adaptability to future developments of PC and data acquisition technology.

  13. Cluster identification based on correlations

    NASA Astrophysics Data System (ADS)

    Schulman, L. S.

    2012-04-01

    The problem addressed is the identification of cooperating agents based on correlations created as a result of the joint action of these and other agents. A systematic method for using correlations beyond second moments is developed. The technique is applied to a didactic example, the identification of alphabet letters based on correlations among the pixels used in an image of the letter. As in this example, agents can belong to more than one cluster. Moreover, the identification scheme does not require that the patterns be known ahead of time.

  14. Correlation, Cost Risk, and Geometry

    NASA Technical Reports Server (NTRS)

    Dean, Edwin B.

    1992-01-01

    The geometric viewpoint identifies the choice of a correlation matrix for the simulation of cost risk with the pairwise choice of data vectors corresponding to the parameters used to obtain cost risk. The correlation coefficient is the cosine of the angle between the data vectors after translation to an origin at the mean and normalization for magnitude. Thus correlation is equivalent to expressing the data in terms of a non orthogonal basis. To understand the many resulting phenomena requires the use of the tensor concept of raising the index to transform the measured and observed covariant components into contravariant components before vector addition can be applied. The geometric viewpoint also demonstrates that correlation and covariance are geometric properties, as opposed to purely statistical properties, of the variates. Thus, variates from different distributions may be correlated, as desired, after selection from independent distributions. By determining the principal components of the correlation matrix, variates with the desired mean, magnitude, and correlation can be generated through linear transforms which include the eigenvalues and the eigenvectors of the correlation matrix. The conversion of the data to a non orthogonal basis uses a compound linear transformation which distorts or stretches the data space. Hence, the correlated data does not have the same properties as the uncorrelated data used to generate it. This phenomena is responsible for seemingly strange observations such as the fact that the marginal distributions of the correlated data can be quite different from the distributions used to generate the data. The joint effect of statistical distributions and correlation remains a fertile area for further research. In terms of application to cost estimating, the geometric approach demonstrates that the estimator must have data and must understand that data in order to properly choose the correlation matrix appropriate for a given estimate

  15. Electronic correlations in the ironpnictides

    SciTech Connect

    Qazilbash, M. M.; Hamlin, J. J.; Baumbach, R. E.; Zhang, Lijun; Singh, David J; Maple, M. B.; Basov, D. N.

    2009-01-01

    In correlated metals derived from Mott insulators, the motion of an electron is impeded by Coulomb repulsion due to other electrons. This phenomenon causes a substantial reduction in the electron's kinetic energy, leading to remarkable experimental manifestations in optical spectroscopy. The high-transition-temperature (Tc) superconducting cuprates are perhaps the most studied examples of such correlated metals. The occurrence of high-Tc superconductivity in the iron pnictides puts a spotlight on the relevance of correlation effects in these materials. Here, we present an infrared and optical study on single crystals of the iron pnictide superconductor LaFePO. We find clear evidence of electronic correlations in metallic LaFePO with the kinetic energy of the electrons reduced to half of that predicted by band theory of nearly free electrons. We deduce that electronic many-body effects are important in the iron pnictides despite the absence of a Mott transition.

  16. Largescale QSO - Galaxy Correlations Revisited

    NASA Astrophysics Data System (ADS)

    Bartelmann, M.; Schneider, P.

    1993-04-01

    Fugmann (1990) claimed indications for correlations between Lick galaxies and high-redshift, radio-loud background sources. We re- analyze these correlations using an improved statistical method based on Spearman's rank-order test, which we have introduced recently (Bartelmann & Schneider 1993). To our surprise, we are not able to reproduce Fugmann's results, but we detect a significant correlation between moderate-redshift sources from the 1-Jansky catalog and Lick galaxies, which increases when we apply an optical flux limit to the source sample. We interpret these empirical results in terms of an amplification bias caused by gravitational light deflection by dark matter; in particular, we argue that the observed large-scale QSO-galaxy correlations can provide a proof for the association of luminous matter (galaxies) with dark matter.

  17. Correlations and Neuronal Population Information.

    PubMed

    Kohn, Adam; Coen-Cagli, Ruben; Kanitscheider, Ingmar; Pouget, Alexandre

    2016-07-01

    Brain function involves the activity of neuronal populations. Much recent effort has been devoted to measuring the activity of neuronal populations in different parts of the brain under various experimental conditions. Population activity patterns contain rich structure, yet many studies have focused on measuring pairwise relationships between members of a larger population-termed noise correlations. Here we review recent progress in understanding how these correlations affect population information, how information should be quantified, and what mechanisms may give rise to correlations. As population coding theory has improved, it has made clear that some forms of correlation are more important for information than others. We argue that this is a critical lesson for those interested in neuronal population responses more generally: Descriptions of population responses should be motivated by and linked to well-specified function. Within this context, we offer suggestions of where current theoretical frameworks fall short. PMID:27145916

  18. Glassy correlations in nematic elastomers

    NASA Astrophysics Data System (ADS)

    Lu, Bing; Goldbart, Paul; Mao, Xiaoming

    2009-03-01

    We address the physical properties of an isotropic melt or solution of nematogenic polymers that is then cross-linked beyond the vulcanization point. To do this, we construct a replica Landau theory involving a coupled pair of order- parameter fields: one describing vulcanization, the other describing local nematic order. Thermal nematic fluctuations, present at the time of cross-linking, are trapped by cross- linking into the vulcanized network. The resulting glassy nematic fluctuations are analyzed in the Gaussian approximation in two regimes. When the localization length is shorter than the thermal nematic correlation length, the nematic correlations are well captured as glassy correlations. In the opposite regime, fluctuations in the positions of the localized polymers partially wash out the glassy nematic correlations.

  19. Digital correlator with fewer IC's

    NASA Technical Reports Server (NTRS)

    Apple, G. G.; Rubin, L.

    1979-01-01

    Digital correlator requires only few integrated circuits to determine synchronization of two 24-bit digital words. Circuit is easily reduced or expanded to accommodate shorter or longer words and can be utilized in industrial and commercial data processing and telecommunications.

  20. Correlated Lloyd model: Exact solution

    NASA Astrophysics Data System (ADS)

    Kozlov, G. G.

    2014-11-01

    We describe an exactly solvable model of a disordered system that is a generalized Lloyd model; it differs from the classical model because the random potential is not a δ-correlated random process. We show that the exact average Green's function in this case is independent of the correlation radius of the random potential and, as in the classical Lloyd model, is a crystal Green's function whose energy argument acquires an imaginary part dependent on the disorder degree.

  1. NASA SERC digital correlator projects

    NASA Technical Reports Server (NTRS)

    Canaris, John

    1992-01-01

    Interest in custom digital correlator processors is growing, in both the radio astronomy and earth sensing communities, as scientists realize that VLSI technology is available to them. This paper presents three digital correlator projects currently underway at the NASA SERC for VLSI Systems Design. The projects are as follows: a 60MHz chip for the ESTAR satellite; a 100MHz, 1024 channel autocorrelator; and a 64 MHz, VLSI system consisting of 8 32- channel complex crosscorrelators including phase rotators.

  2. Why Waveform Correlation Sometimes Fails

    NASA Astrophysics Data System (ADS)

    Carmichael, J.

    2015-12-01

    Waveform correlation detectors used in explosion monitoring scan noisy geophysical data to test two competing hypotheses: either (1) an amplitude-scaled version of a template waveform is present, or, (2) no signal is present at all. In reality, geophysical wavefields that are monitored for explosion signatures include waveforms produced by non-target sources that are partially correlated with the waveform template. Such signals can falsely trigger correlation detectors, particularly at low thresholds required to monitor for smaller target explosions. This challenge is particularly formidable when monitoring known test sites for seismic disturbances, since uncatalogued natural seismicity is (generally) more prevalent at lower magnitudes, and could be mistaken for small explosions. To address these challenges, we identify real examples in which correlation detectors targeting explosions falsely trigger on both site-proximal earthquakes (Figure 1, below) and microseismic "noise". Motivated by these examples, we quantify performance loss when applying these detectors, and re-evaluate the correlation-detector's hypothesis test. We thereby derive new detectors from more general hypotheses that admit unknown background seismicity, and apply these to real data. From our treatment, we derive "rules of thumb'' for proper template and threshold selection in heavily cluttered signal environments. Last, we answer the question "what is the probability of falsely detecting an earthquake collocated at a test site?", using correlation detectors that include explosion-triggered templates. Figure Top: An eight-channel data stream (black) recorded from an earthquake near a mine. Red markers indicate a detection. Middle: The correlation statistic computed by scanning the template against the data stream at top. The red line indicates the threshold for event declaration, determined by a false-alarm on noise probability constraint, as computed from the signal-absent distribution using

  3. Local Realism of Macroscopic Correlations

    NASA Astrophysics Data System (ADS)

    Ramanathan, R.; Paterek, T.; Kay, A.; Kurzyński, P.; Kaszlikowski, D.

    2011-08-01

    We identify conditions under which correlations resulting from quantum measurements performed on macroscopic systems (systems composed of a number of particles of the order of the Avogadro number) can be described by local realism. We argue that the emergence of local realism at the macroscopic level is caused by an interplay between the monogamous nature of quantum correlations and the fact that macroscopic measurements do not reveal properties of individual particles.

  4. The Murchison Widefield Array Correlator

    NASA Astrophysics Data System (ADS)

    Ord, S. M.; Crosse, B.; Emrich, D.; Pallot, D.; Wayth, R. B.; Clark, M. A.; Tremblay, S. E.; Arcus, W.; Barnes, D.; Bell, M.; Bernardi, G.; Bhat, N. D. R.; Bowman, J. D.; Briggs, F.; Bunton, J. D.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; deSouza, L.; Ewell-Wice, A.; Feng, L.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Herne, D.; Hewitt, J. N.; Hindson, L.; Hurley-Walker, N.; Jacobs, D.; Johnston-Hollitt, M.; Kaplan, D. L.; Kasper, J. C.; Kincaid, B. B.; Koenig, R.; Kratzenberg, E.; Kudryavtseva, N.; Lenc, E.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Offringa, A.; Pathikulangara, J.; Pindor, B.; Prabu, T.; Procopio, P.; Remillard, R. A.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Salah, J. E.; Sault, R. J.; Udaya Shankar, N.; Srivani, K. S.; Stevens, J.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.; Wyithe, J. S. B.

    2015-03-01

    The Murchison Widefield Array is a Square Kilometre Array Precursor. The telescope is located at the Murchison Radio-astronomy Observatory in Western Australia. The MWA consists of 4 096 dipoles arranged into 128 dual polarisation aperture arrays forming a connected element interferometer that cross-correlates signals from all 256 inputs. A hybrid approach to the correlation task is employed, with some processing stages being performed by bespoke hardware, based on Field Programmable Gate Arrays, and others by Graphics Processing Units housed in general purpose rack mounted servers. The correlation capability required is approximately 8 tera floating point operations per second. The MWA has commenced operations and the correlator is generating 8.3 TB day-1 of correlation products, that are subsequently transferred 700 km from the MRO to Perth (WA) in real-time for storage and offline processing. In this paper, we outline the correlator design, signal path, and processing elements and present the data format for the internal and external interfaces.

  5. Nonglobal correlations in collider physics

    DOE PAGESBeta

    Moult, Ian; Larkoski, Andrew J.

    2016-01-13

    Despite their importance for precision QCD calculations, correlations between in- and out-of-jet regions of phase space have never directly been observed. These so-called non-global effects are present generically whenever a collider physics measurement is not explicitly dependent on radiation throughout the entire phase space. In this paper, we introduce a novel procedure based on mutual information, which allows us to isolate these non-global correlations between measurements made in different regions of phase space. We study this procedure both analytically and in Monte Carlo simulations in the context of observables measured on hadronic final states produced in e+e- collisions, though itmore » is more widely applicable.The procedure exploits the sensitivity of soft radiation at large angles to non-global correlations, and we calculate these correlations through next-to-leading logarithmic accuracy. The bulk of these non-global correlations are found to be described in Monte Carlo simulation. They increase by the inclusion of non-perturbative effects, which we show can be incorporated in our calculation through the use of a model shape function. As a result, this procedure illuminates the source of non-global correlations and has connections more broadly to fundamental quantities in quantum field theory.« less

  6. Nonglobal correlations in collider physics

    NASA Astrophysics Data System (ADS)

    Larkoski, Andrew J.; Moult, Ian

    2016-01-01

    Despite their importance for precision QCD calculations, correlations between in- and out-of-jet regions of phase space have never directly been observed. These so-called nonglobal effects are present generically whenever a collider physics measurement is not explicitly dependent on radiation throughout the entire phase space. In this paper, we introduce a novel procedure based on mutual information, which allows us to isolate these nonglobal correlations between measurements made in different regions of phase space. We study this procedure both analytically and in Monte Carlo simulations in the context of observables measured on hadronic final states produced in e+e- collisions, though it is more widely applicable. The procedure exploits the sensitivity of soft radiation at large angles to nonglobal correlations, and we calculate these correlations through next-to-leading logarithmic accuracy. The bulk of these nonglobal correlations are found to be described in Monte Carlo simulation. They increase by the inclusion of nonperturbative effects, which we show can be incorporated in our calculation through the use of a model shape function. This procedure illuminates the source of nonglobal correlations and has connections more broadly to fundamental quantities in quantum field theory.

  7. Dual allosteric activation mechanisms in monomeric human glucokinase

    PubMed Central

    Whittington, A. Carl; Larion, Mioara; Bowler, Joseph M.; Ramsey, Kristen M.; Brüschweiler, Rafael; Miller, Brian G.

    2015-01-01

    Cooperativity in human glucokinase (GCK), the body’s primary glucose sensor and a major determinant of glucose homeostatic diseases, is fundamentally different from textbook models of allostery because GCK is monomeric and contains only one glucose-binding site. Prior work has demonstrated that millisecond timescale order-disorder transitions within the enzyme’s small domain govern cooperativity. Here, using limited proteolysis, we map the site of disorder in unliganded GCK to a 30-residue active-site loop that closes upon glucose binding. Positional randomization of the loop, coupled with genetic selection in a glucokinase-deficient bacterium, uncovers a hyperactive GCK variant with substantially reduced cooperativity. Biochemical and structural analysis of this loop variant and GCK variants associated with hyperinsulinemic hypoglycemia reveal two distinct mechanisms of enzyme activation. In α-type activation, glucose affinity is increased, the proteolytic susceptibility of the active site loop is suppressed and the 1H-13C heteronuclear multiple quantum coherence (HMQC) spectrum of 13C-Ile–labeled enzyme resembles the glucose-bound state. In β-type activation, glucose affinity is largely unchanged, proteolytic susceptibility of the loop is enhanced, and the 1H-13C HMQC spectrum reveals no perturbation in ensemble structure. Leveraging both activation mechanisms, we engineer a fully noncooperative GCK variant, whose functional properties are indistinguishable from other hexokinase isozymes, and which displays a 100-fold increase in catalytic efficiency over wild-type GCK. This work elucidates specific structural features responsible for generating allostery in a monomeric enzyme and suggests a general strategy for engineering cooperativity into proteins that lack the structural framework typical of traditional allosteric systems. PMID:26283387

  8. A scalable correlator for multichannel diffuse correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Stapels, Christopher J.; Kolodziejski, Noah J.; McAdams, Daniel; Podolsky, Matthew J.; Fernandez, Daniel E.; Farkas, Dana; Christian, James F.

    2016-03-01

    Diffuse correlation spectroscopy (DCS) is a technique which enables powerful and robust non-invasive optical studies of tissue micro-circulation and vascular blood flow. The technique amounts to autocorrelation analysis of coherent photons after their migration through moving scatterers and subsequent collection by single-mode optical fibers. A primary cost driver of DCS instruments are the commercial hardware-based correlators, limiting the proliferation of multi-channel instruments for validation of perfusion analysis as a clinical diagnostic metric. We present the development of a low-cost scalable correlator enabled by microchip-based time-tagging, and a software-based multi-tau data analysis method. We will discuss the capabilities of the instrument as well as the implementation and validation of 2- and 8-channel systems built for live animal and pre-clinical settings.

  9. Community Detection for Correlation Matrices

    NASA Astrophysics Data System (ADS)

    MacMahon, Mel; Garlaschelli, Diego

    2015-04-01

    A challenging problem in the study of complex systems is that of resolving, without prior information, the emergent, mesoscopic organization determined by groups of units whose dynamical activity is more strongly correlated internally than with the rest of the system. The existing techniques to filter correlations are not explicitly oriented towards identifying such modules and can suffer from an unavoidable information loss. A promising alternative is that of employing community detection techniques developed in network theory. Unfortunately, this approach has focused predominantly on replacing network data with correlation matrices, a procedure that we show to be intrinsically biased because of its inconsistency with the null hypotheses underlying the existing algorithms. Here, we introduce, via a consistent redefinition of null models based on random matrix theory, the appropriate correlation-based counterparts of the most popular community detection techniques. Our methods can filter out both unit-specific noise and system-wide dependencies, and the resulting communities are internally correlated and mutually anticorrelated. We also implement multiresolution and multifrequency approaches revealing hierarchically nested subcommunities with "hard" cores and "soft" peripheries. We apply our techniques to several financial time series and identify mesoscopic groups of stocks which are irreducible to a standard, sectorial taxonomy; detect "soft stocks" that alternate between communities; and discuss implications for portfolio optimization and risk management.

  10. Recirculating cross-correlation detector

    DOEpatents

    Andrews, W.H. Jr.; Roberts, M.J.

    1985-01-18

    A digital cross-correlation detector is provided in which two time-varying signals are correlated by repetitively comparing data samples stored in digital form to detect correlation between the two signals. The signals are sampled at a selected rate converted to digital form, and stored in separate locations in separate memories. When the memories are filled, the data samples from each memory are first fed word-by-word through a multiplier and summing circuit and each result is compared to the last in a peak memory circuit and if larger than the last is retained in the peak memory. Then the address line to leading signal memory is offset by one byte to affect one sample period delay of a known amount in that memory and the data in the two memories are then multiplied word-by-word once again and summed. If a new result is larger than a former sum, it is saved in the peak memory together with the time delay. The recirculating process continues with the address of the one memory being offset one additional byte each cycle until the address is shifted through the length of the memory. The correlation between the two signals is indicated by the peak signal stored in the peak memory together with the delay time at which the peak occurred. The circuit is faster and considerably less expensive than comparable accuracy correlation detectors.

  11. Electronic correlations in Hund metals

    NASA Astrophysics Data System (ADS)

    Fanfarillo, L.; Bascones, E.

    2015-08-01

    To clarify the nature of correlations in Hund metals and its relationship with Mott physics we analyze the electronic correlations in multiorbital systems as a function of intraorbital interaction U , Hund's coupling JH, and electronic filling n . We show that the main process behind the enhancement of correlations in Hund metals is the suppression of the double occupancy of a given orbital, as it also happens in the Mott insulator at half-filling. However, contrary to what happens in Mott correlated states the reduction of the quasiparticle weight Z with JH can happen in spite of increasing charge fluctuations. Therefore, in Hund metals the quasiparticle weight and the mass enhancement are not good measurements of the charge localization. Using simple energetic arguments we explain why the spin polarization induced by Hund's coupling produces orbital decoupling. We also discuss how the behavior at moderate interactions, with correlations controlled by the atomic spin polarization, changes at large U and JH due to the proximity to a Mott insulating state.

  12. Biometric verification with correlation filters.

    PubMed

    Vijaya Kumar, B V K; Savvides, Marios; Xie, Chunyan; Venkataramani, Krithika; Thornton, Jason; Mahalanobis, Abhijit

    2004-01-10

    Using biometrics for subject verification can significantly improve security over that of approaches based on passwords and personal identification numbers, both of which people tend to lose or forget. In biometric verification the system tries to match an input biometric (such as a fingerprint, face image, or iris image) to a stored biometric template. Thus correlation filter techniques are attractive candidates for the matching precision needed in biometric verification. In particular, advanced correlation filters, such as synthetic discriminant function filters, can offer very good matching performance in the presence of variability in these biometric images (e.g., facial expressions, illumination changes, etc.). We investigate the performance of advanced correlation filters for face, fingerprint, and iris biometric verification. PMID:14735958

  13. Biometric verification with correlation filters

    NASA Astrophysics Data System (ADS)

    Vijaya Kumar, B. V. K.; Savvides, Marios; Xie, Chunyan; Venkataramani, Krithika; Thornton, Jason; Mahalanobis, Abhijit

    2004-01-01

    Using biometrics for subject verification can significantly improve security over that of approaches based on passwords and personal identification numbers, both of which people tend to lose or forget. In biometric verification the system tries to match an input biometric (such as a fingerprint, face image, or iris image) to a stored biometric template. Thus correlation filter techniques are attractive candidates for the matching precision needed in biometric verification. In particular, advanced correlation filters, such as synthetic discriminant function filters, can offer very good matching performance in the presence of variability in these biometric images (e.g., facial expressions, illumination changes, etc.). We investigate the performance of advanced correlation filters for face, fingerprint, and iris biometric verification.

  14. Sequence correlations shape protein promiscuity

    NASA Astrophysics Data System (ADS)

    Lukatsky, David B.; Afek, Ariel; Shakhnovich, Eugene I.

    2011-08-01

    We predict analytically that diagonal correlations of amino acid positions within protein sequences statistically enhance protein propensity for nonspecific binding. We use the term "promiscuity" to describe such nonspecific binding. Diagonal correlations represent statistically significant repeats of sequence patterns where amino acids of the same type are clustered together. The predicted effect is qualitatively robust with respect to the form of the microscopic interaction potentials and the average amino acid composition. Our analytical results provide an explanation for the enhanced diagonal correlations observed in hubs of eukaryotic organismal proteomes [J. Mol. Biol. 409, 439 (2011)], 10.1016/j.jmb.2011.03.056. We suggest experiments that will allow direct testing of the predicted effect.

  15. Softc: An Operational Software Correlator

    NASA Technical Reports Server (NTRS)

    Lowe, Stephen T.

    2004-01-01

    Softc has been used operationally for spacecraft navigation at JPL for over 2 years and will be JPL's Mark 5 correlator next year. Softc was written to be as close to an ideal correlator as possible, making approximations only below 10(exp -13) seconds. The program can correlate real USB, real LSB, or complex I/Q data sampled with 1, 2, 4. or 8-bit resolution, and was developed with strong debugging tools that made final debugging relatively quick. Softc's algorithms and program structure are fully documented. Timing tests on a recent Intel CPU show Softc processes 8 lags of 1-bit sampled data at 10 MSamples/sec, independent of sample rate.

  16. Correlated optical and isotopic nanoscopy

    NASA Astrophysics Data System (ADS)

    Saka, Sinem K.; Vogts, Angela; Kröhnert, Katharina; Hillion, François; Rizzoli, Silvio O.; Wessels, Johannes T.

    2014-04-01

    The isotopic composition of different materials can be imaged by secondary ion mass spectrometry. In biology, this method is mainly used to study cellular metabolism and turnover, by pulsing the cells with marker molecules such as amino acids labelled with stable isotopes (15N, 13C). The incorporation of the markers is then imaged with a lateral resolution that can surpass 100 nm. However, secondary ion mass spectrometry cannot identify specific subcellular structures like organelles, and needs to be correlated with a second technique, such as fluorescence imaging. Here, we present a method based on stimulated emission depletion microscopy that provides correlated optical and isotopic nanoscopy (COIN) images. We use this approach to study the protein turnover in different organelles from cultured hippocampal neurons. Correlated optical and isotopic nanoscopy can be applied to a variety of biological samples, and should therefore enable the investigation of the isotopic composition of many organelles and subcellular structures.

  17. Correlative Fluorescence and Electron Microscopy

    PubMed Central

    Schirra, Randall T.; Zhang, Peijun

    2014-01-01

    Correlative fluorescence and electron microscopy (CFEM) is a multimodal technique that combines dynamic and localization information from fluorescence methods with ultrastructural data from electron microscopy, to give new information about how cellular components change relative to the spatiotemporal dynamics within their environment. In this review, we will discuss some of the basic techniques and tools of the trade for utilizing this attractive research method, which is becoming a very powerful tool for biology labs. The information obtained from correlative methods has proven to be invaluable in creating consensus between the two types of microscopy, extending the capability of each, and cutting the time and expense associate with using each method separately for comparative analysis. The realization of the advantages of these methods in cell biology have led to rapid improvement in the protocols and have ushered in a new generation of instruments to reach the next level of correlation – integration. PMID:25271959

  18. Quantum correlation via quantum coherence

    NASA Astrophysics Data System (ADS)

    Yu, Chang-shui; Zhang, Yang; Zhao, Haiqing

    2014-06-01

    Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition—quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes of quantum coherence. We propose a revised measure for total coherence and find that this measure can lead to a symmetric version of geometric quantum correlation, which is analytic for two qubits. In particular, this measure can also arrive at a monogamy equality on the distribution of quantum coherence. Finally, we also quantify a remaining type of quantum coherence and find that for two qubits, it is directly connected with quantum nonlocality.

  19. Minimum Bayes risk image correlation

    NASA Technical Reports Server (NTRS)

    Minter, T. C., Jr.

    1980-01-01

    In this paper, the problem of designing a matched filter for image correlation will be treated as a statistical pattern recognition problem. It is shown that, by minimizing a suitable criterion, a matched filter can be estimated which approximates the optimum Bayes discriminant function in a least-squares sense. It is well known that the use of the Bayes discriminant function in target classification minimizes the Bayes risk, which in turn directly minimizes the probability of a false fix. A fast Fourier implementation of the minimum Bayes risk correlation procedure is described.

  20. Top Quark Spin Correlations - Theory

    SciTech Connect

    Parke, Stephen J.; /Fermilab

    2012-02-01

    The top quark decay width (G{sub F}m{sub t}{sup 3} {approx} 1 GeV) is much larger than the QCD hadronization scale ({Lambda}{sub QCD} {approx} 0.1 GeV) and much larger than the spin decorrelation scale ({Lambda}{sub QCD}{sup 2}/m{sub t} {approx} 0.1 MeV). Therefore, spin correlations in top quark pair production are reflected in angular correlations of the decay products, see [1] and [2].

  1. Petascale cross correlation in software

    NASA Astrophysics Data System (ADS)

    Barsdell, Benjamin R.; Clark, M. A.; Greenhill, L. J.

    2014-04-01

    The exascale computational demands of back-end processing in the era of the SKA and HERA, headlined by the needs of cross-correlation, are likely to require solutions that differ significantly from traditional approaches on smaller arrays. The rapid growth of massively-parallel general-purpose computing hardware presents an alternative to ASIC- or FPGA-based designs and promises several advantages. In this talk we present strong scaling results for an FX correlator that runs entirely in software on GPU-based off-the-shelf HPC clusters.

  2. Converting Coherence to Quantum Correlations

    NASA Astrophysics Data System (ADS)

    Ma, Jiajun; Yadin, Benjamin; Girolami, Davide; Vedral, Vlatko; Gu, Mile

    2016-04-01

    Recent results in quantum information theory characterize quantum coherence in the context of resource theories. Here, we study the relation between quantum coherence and quantum discord, a kind of quantum correlation which appears even in nonentangled states. We prove that the creation of quantum discord with multipartite incoherent operations is bounded by the amount of quantum coherence consumed in its subsystems during the process. We show how the interplay between quantum coherence consumption and creation of quantum discord works in the preparation of multipartite quantum correlated states and in the model of deterministic quantum computation with one qubit.

  3. Correlation properties of loose groups

    SciTech Connect

    Maia, M.A.G.; Da Costa, L.N. )

    1990-02-01

    The two-point spatial correlation function for loose groups of galaxies is computed, using the recently compiled catalog of groups in the southern hemisphere. It is found that the correlation function for groups has a similar slope to that of galaxies but with a smaller amplitude, confirming an earlier result obtained from a similar analysis of the CfA group catalog. This implies that groups of galaxies are more randomly distributed than galaxies, which may be consistent with the predictions of Kashlinsky (1987) for a gravitational clustering scenario for the formation of large-scale structures. 21 refs.

  4. Reveal quantum correlation in complementary bases

    PubMed Central

    Wu, Shengjun; Ma, Zhihao; Chen, Zhihua; Yu, Sixia

    2014-01-01

    An essential feature of genuine quantum correlation is the simultaneous existence of correlation in complementary bases. We reveal this feature of quantum correlation by defining measures based on invariance under a basis change. For a bipartite quantum state, the classical correlation is the maximal correlation present in a certain optimum basis, while the quantum correlation is characterized as a series of residual correlations in the mutually unbiased bases. Compared with other approaches to quantify quantum correlation, our approach gives information-theoretical measures that directly reflect the essential feature of quantum correlation. PMID:24503595

  5. PREFACE: Strongly correlated electron systems Strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Saxena, Siddharth S.; Littlewood, P. B.

    2012-07-01

    This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The selected papers derived from invited presentations seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The focus is on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity and metal-insulator transitions. Both experimental and theoretical work is presented. Based on fundamental advances in the understanding of electronic materials, much of 20th century materials physics was driven by miniaturisation and integration in the electronics industry to the current generation of nanometre scale devices. The achievements of this industry have brought unprecedented advances to society and well-being, and no doubt there is much further to go—note that this progress is founded on investments and studies in the fundamentals of condensed matter physics from more than 50 years ago. Nevertheless, the defining challenges for the 21st century will lie in the discovery in science, and deployment through engineering, of technologies that can deliver the scale needed to have an impact on the sustainability agenda. Thus the big developments in nanotechnology may lie not in the pursuit of yet smaller transistors, but in the design of new structures that can revolutionise the performance of solar cells, batteries, fuel cells, light-weight structural materials, refrigeration, water purification, etc. The science presented in the papers of this special section also highlights the underlying interest in energy-dense materials, which

  6. EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Ronning, Filip; Batista, Cristian

    2011-03-01

    Strongly correlated electrons is an exciting and diverse field in condensed matter physics. This special issue aims to capture some of that excitement and recent developments in the field. Given that this issue was inspired by the 2010 International Conference on Strongly Correlated Electron Systems (SCES 2010), we briefly give some history in order to place this issue in context. The 2010 International Conference on Strongly Correlated Electron Systems was held in Santa Fe, New Mexico, a reunion of sorts from the 1989 International Conference on the Physics of Highly Correlated Electron Systems that also convened in Santa Fe. SCES 2010—co-chaired by John Sarrao and Joe Thompson—followed the tradition of earlier conferences, in this century, hosted by Buzios (2008), Houston (2007), Vienna (2005), Karlsruhe (2004), Krakow (2002) and Ann Arbor (2001). Every three years since 1997, SCES has joined the International Conference on Magnetism (ICM), held in Recife (2000), Rome (2003), Kyoto (2006) and Karlsruhe (2009). Like its predecessors, SCES 2010 topics included strongly correlated f- and d-electron systems, heavy-fermion behaviors, quantum-phase transitions, non-Fermi liquid phenomena, unconventional superconductivity, and emergent states that arise from electronic correlations. Recent developments from studies of quantum magnetism and cold atoms complemented the traditional subjects and were included in SCES 2010. 2010 celebrated the 400th anniversary of Santa Fe as well as the birth of astronomy. So what's the connection to SCES? The Dutch invention of the first practical telescope and its use by Galileo in 1610 and subsequent years overturned dogma that the sun revolved about the earth. This revolutionary, and at the time heretical, conclusion required innovative combinations of new instrumentation, observation and mathematics. These same combinations are just as important 400 years later and are the foundation of scientific discoveries that were discussed

  7. Sample Size and Correlational Inference

    ERIC Educational Resources Information Center

    Anderson, Richard B.; Doherty, Michael E.; Friedrich, Jeff C.

    2008-01-01

    In 4 studies, the authors examined the hypothesis that the structure of the informational environment makes small samples more informative than large ones for drawing inferences about population correlations. The specific purpose of the studies was to test predictions arising from the signal detection simulations of R. B. Anderson, M. E. Doherty,…

  8. Multilevel Modeling with Correlated Effects

    ERIC Educational Resources Information Center

    Kim, Jee-Seon; Frees, Edward W.

    2007-01-01

    When there exist omitted effects, measurement error, and/or simultaneity in multilevel models, explanatory variables may be correlated with random components, and standard estimation methods do not provide consistent estimates of model parameters. This paper introduces estimators that are consistent under such conditions. By employing generalized…

  9. Echoes in correlated neural systems

    NASA Astrophysics Data System (ADS)

    Helias, M.; Tetzlaff, T.; Diesmann, M.

    2013-02-01

    Correlations are employed in modern physics to explain microscopic and macroscopic phenomena, like the fractional quantum Hall effect and the Mott insulator state in high temperature superconductors and ultracold atoms. Simultaneously probed neurons in the intact brain reveal correlations between their activity, an important measure to study information processing in the brain that also influences the macroscopic signals of neural activity, like the electroencephalogram (EEG). Networks of spiking neurons differ from most physical systems: the interaction between elements is directed, time delayed, mediated by short pulses and each neuron receives events from thousands of neurons. Even the stationary state of the network cannot be described by equilibrium statistical mechanics. Here we develop a quantitative theory of pairwise correlations in finite-sized random networks of spiking neurons. We derive explicit analytic expressions for the population-averaged cross correlation functions. Our theory explains why the intuitive mean field description fails, how the echo of single action potentials causes an apparent lag of inhibition with respect to excitation and how the size of the network can be scaled while maintaining its dynamical state. Finally, we derive a new criterion for the emergence of collective oscillations from the spectrum of the time-evolution propagator.

  10. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-08-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  11. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-01-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  12. Resistant multiple sparse canonical correlation.

    PubMed

    Coleman, Jacob; Replogle, Joseph; Chandler, Gabriel; Hardin, Johanna

    2016-04-01

    Canonical correlation analysis (CCA) is a multivariate technique that takes two datasets and forms the most highly correlated possible pairs of linear combinations between them. Each subsequent pair of linear combinations is orthogonal to the preceding pair, meaning that new information is gleaned from each pair. By looking at the magnitude of coefficient values, we can find out which variables can be grouped together, thus better understanding multiple interactions that are otherwise difficult to compute or grasp intuitively. CCA appears to have quite powerful applications to high-throughput data, as we can use it to discover, for example, relationships between gene expression and gene copy number variation. One of the biggest problems of CCA is that the number of variables (often upwards of 10,000) makes biological interpretation of linear combinations nearly impossible. To limit variable output, we have employed a method known as sparse canonical correlation analysis (SCCA), while adding estimation which is resistant to extreme observations or other types of deviant data. In this paper, we have demonstrated the success of resistant estimation in variable selection using SCCA. Additionally, we have used SCCA to find multiple canonical pairs for extended knowledge about the datasets at hand. Again, using resistant estimators provided more accurate estimates than standard estimators in the multiple canonical correlation setting. R code is available and documented at https://github.com/hardin47/rmscca. PMID:26963062

  13. Tetrachoric Correlation: A Permutation Alternative

    ERIC Educational Resources Information Center

    Long, Michael A.; Berry, Kenneth J.; Mielke, Paul W., Jr.

    2009-01-01

    An exact permutation test is provided for the tetrachoric correlation coefficient. Comparisons with the conventional test employing Student's t distribution demonstrate the necessity of using the permutation approach for small sample sizes and/or disproportionate marginal frequency totals. (Contains 4 tables.)

  14. Time correlators from deferred measurements

    NASA Astrophysics Data System (ADS)

    Oehri, D.; Lebedev, A. V.; Lesovik, G. B.; Blatter, G.

    2016-01-01

    Repeated measurements that typically occur in two-time or multitime correlators rely on von Neumann's projection postulate, telling how to restart the system after an intermediate measurement. We invoke the principle of deferred measurement to describe an alternative procedure in which coevolving quantum memories extract system information through entanglement, combined with a final readout of the memories described by Born's rule. Our approach to repeated quantum measurements respects the unitary evolution of quantum mechanics during intermediate times, unifies the treatment of strong and weak measurements, and reproduces the projected and (anti)symmetrized correlators in the two limits. As an illustration, we apply our formalism to the calculation of the electron charge correlator in a mesoscopic physics setting, where single electron pulses assume the role of flying memory qubits. We propose an experimental setup that reduces the measurement of the time correlator to the measurement of currents and noise, exploiting the (pulsed) injection of electrons to cope with the challenge of performing short-time measurements.

  15. Unorthodox Uses of Correlation Coefficients.

    ERIC Educational Resources Information Center

    Kraemer, Helena Chmura

    While the potential use of correlation methods has spread to wide contexts and these uses have permeated behavioral research, their scope remains the orthodox applications: to test independence, and to measure association. It is well worth noticing that problems having no obstensible connection to dependence, independence, or association have been…

  16. Dynamics of electricity market correlations

    NASA Astrophysics Data System (ADS)

    Alvarez-Ramirez, J.; Escarela-Perez, R.; Espinosa-Perez, G.; Urrea, R.

    2009-06-01

    Electricity market participants rely on demand and price forecasts to decide their bidding strategies, allocate assets, negotiate bilateral contracts, hedge risks, and plan facility investments. However, forecasting is hampered by the non-linear and stochastic nature of price time series. Diverse modeling strategies, from neural networks to traditional transfer functions, have been explored. These approaches are based on the assumption that price series contain correlations that can be exploited for model-based prediction purposes. While many works have been devoted to the demand and price modeling, a limited number of reports on the nature and dynamics of electricity market correlations are available. This paper uses detrended fluctuation analysis to study correlations in the demand and price time series and takes the Australian market as a case study. The results show the existence of correlations in both demand and prices over three orders of magnitude in time ranging from hours to months. However, the Hurst exponent is not constant over time, and its time evolution was computed over a subsample moving window of 250 observations. The computations, also made for two Canadian markets, show that the correlations present important fluctuations over a seasonal one-year cycle. Interestingly, non-linearities (measured in terms of a multifractality index) and reduced price predictability are found for the June-July periods, while the converse behavior is displayed during the December-January period. In terms of forecasting models, our results suggest that non-linear recursive models should be considered for accurate day-ahead price estimation. On the other hand, linear models seem to suffice for demand forecasting purposes.

  17. Separating Spike Count Correlation from Firing Rate Correlation

    PubMed Central

    Vinci, Giuseppe; Ventura, Valérie; Smith, Matthew A.; Kass, Robert E.

    2016-01-01

    Populations of cortical neurons exhibit shared fluctuations in spiking activity over time. When measured for a pair of neurons over multiple repetitions of an identical stimulus, this phenomenon emerges as correlated trial-to-trial response variability via spike count correlation (SCC). However, spike counts can be viewed as noisy versions of firing rates, which can vary from trial to trial. From this perspective, the SCC for a pair of neurons becomes a noisy version of the corresponding firing-rate correlation (FRC). Furthermore, the magnitude of the SCC is generally smaller than that of the FRC, and is likely to be less sensitive to experimental manipulation. We provide statistical methods for disambiguating time-averaged drive from within-trial noise, thereby separating FRC from SCC. We study these methods to document their reliability, and we apply them to neurons recorded in vivo from area V4, in an alert animal. We show how the various effects we describe are reflected in the data: within-trial effects are largely negligible, while attenuation due to trial-to-trial variation dominates, and frequently produces comparisons in SCC that, because of noise, do not accurately reflect those based on the underlying FRC. PMID:26942746

  18. In Vivo Fluorescence Correlation and Cross-Correlation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mütze, Jörg; Ohrt, Thomas; Petrášek, Zdeněk; Schwille, Petra

    In this manuscript, we describe the application of Fluorescence Correlation Spectroscopy (FCS), Fluorescence Cross-Correlation Spectroscopy (FCCS), and scanning FCS (sFCS) to two in vivo systems. In the first part, we describe the application of two-photon standard and scanning FCS in Caenorhabditis elegans embryos. The differentiation of a single fertilized egg into a complex organism in C. elegans is regulated by a number of protein-dependent processes. The oocyte divides asymmetrically into two daughter cells of different developmental fate. Two of the involved proteins, PAR-2 and NMY-2, are studied. The second investigated system is the mechanism of RNA interference in human cells. An EGFP based cell line that allows to study the dynamics and localization of the RNA-induced silencing complex (RISC) with FCS in vivo is created, which has so far been inaccessible with other experimental methods. Furthermore, Fluorescence Cross-Correlation Spectroscopy is employed to highlight the asymmetric incorporation of labeled siRNAs into RISC.

  19. Separating Spike Count Correlation from Firing Rate Correlation.

    PubMed

    Vinci, Giuseppe; Ventura, Valérie; Smith, Matthew A; Kass, Robert E

    2016-05-01

    Populations of cortical neurons exhibit shared fluctuations in spiking activity over time. When measured for a pair of neurons over multiple repetitions of an identical stimulus, this phenomenon emerges as correlated trial-to-trial response variability via spike count correlation (SCC). However, spike counts can be viewed as noisy versions of firing rates, which can vary from trial to trial. From this perspective, the SCC for a pair of neurons becomes a noisy version of the corresponding firing rate correlation (FRC). Furthermore, the magnitude of the SCC is generally smaller than that of the FRC and is likely to be less sensitive to experimental manipulation. We provide statistical methods for disambiguating time-averaged drive from within-trial noise, thereby separating FRC from SCC. We study these methods to document their reliability, and we apply them to neurons recorded in vivo from area V4 in an alert animal. We show how the various effects we describe are reflected in the data: within-trial effects are largely negligible, while attenuation due to trial-to-trial variation dominates and frequently produces comparisons in SCC that, because of noise, do not accurately reflect those based on the underlying FRC. PMID:26942746

  20. Correlates of hysterectomy in Australia.

    PubMed

    Santow, G; Bracher, M

    1992-04-01

    With around one in five women undergoing hysterectomy by the age of 50, the prevalence of hysterectomy in Australia is greater than in Europe but less than in the United States. In this paper, data from a nationally representative sample survey of 2547 Australian women aged 20-59 years are employed to identify correlates of hysterectomy and tubal sterilization over the last 30 years. Physiological, socio-economic and supply-side factors all influence the propensity to undergo hysterectomy, and a comparison with the correlates of tubal sterilization reveals parallels and contrasts between the determinants of the two operations. Age and parity are important predictors of hysterectomy. In addition, use of oral contraceptives for at least five years reduces the risk of hysterectomy, as do tubal sterilization, tertiary education and birthplace in Southern Europe. Conversely, risk increases after experiencing side effects with the IUD or repeated foetal losses, or after bearing a third child before the age of 25. PMID:1604382

  1. Softness Correlations Across Length Scales

    NASA Astrophysics Data System (ADS)

    Ivancic, Robert; Shavit, Amit; Rieser, Jennifer; Schoenholz, Samuel; Cubuk, Ekin; Durian, Douglas; Liu, Andrea; Riggleman, Robert

    In disordered systems, it is believed that mechanical failure begins with localized particle rearrangements. Recently, a machine learning method has been introduced to identify how likely a particle is to rearrange given its local structural environment, quantified by softness. We calculate the softness of particles in simulations of atomic Lennard-Jones mixtures, molecular Lennard-Jones oligomers, colloidal systems and granular systems. In each case, we find that the length scale characterizing spatial correlations of softness is approximately a particle diameter. These results provide a rationale for why localized rearrangements--whose size is presumably set by the scale of softness correlations--might occur in disordered systems across many length scales. Supported by DOE DE-FG02-05ER46199.

  2. Bootstrapping N=2 chiral correlators

    NASA Astrophysics Data System (ADS)

    Lemos, Madalena; Liendo, Pedro

    2016-01-01

    We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.

  3. Correlated Electrons in Reduced Dimensions

    SciTech Connect

    Bonesteel, Nicholas E

    2015-01-31

    This report summarizes the work accomplished under the support of US DOE grant # DE-FG02-97ER45639, "Correlated Electrons in Reduced Dimensions." The underlying hypothesis of the research supported by this grant has been that studying the unique behavior of correlated electrons in reduced dimensions can lead to new ways of understanding how matter can order and how it can potentially be used. The systems under study have included i) fractional quantum Hall matter, which is realized when electrons are confined to two-dimensions and placed in a strong magnetic field at low temperature, ii) one-dimensional chains of spins and exotic quasiparticle excitations of topologically ordered matter, and iii) electrons confined in effectively ``zero-dimensional" semiconductor quantum dots.

  4. Correlations in avalanche critical points.

    PubMed

    Cerruti, Benedetta; Vives, Eduard

    2009-07-01

    Avalanche dynamics and related power-law statistics are ubiquitous in nature, arising in phenomena such as earthquakes, forest fires, and solar flares. Very interestingly, an analogous behavior is associated with many condensed-matter systems, such as ferromagnets and martensites. Bearing it in mind, we study the prototypical random-field Ising model at T=0. We find a finite correlation between waiting intervals and the previous avalanche size. This correlation is not found in other models for avalanches but it is experimentally found in earthquakes and in forest fires. Our study suggests that this effect occurs in critical points that are at the end of a first-order discontinuity separating two regimes: one with high activity from another with low activity. PMID:19658651

  5. Supercritical Angle Fluorescence Correlation Spectroscopy

    PubMed Central

    Ries, Jonas; Ruckstuhl, Thomas; Verdes, Dorinel; Schwille, Petra

    2008-01-01

    We explore the potential of a supercritical angle (SA) objective for fluorescence correlation spectroscopy (FCS). This novel microscope objective combines tight focusing by an aspheric lens with strong axial confinement of supercritical angle fluorescence collection by a parabolic mirror lens, resulting in a small detection volume. The tiny axial extent of the detection volume features an excellent surface sensitivity, as is demonstrated by diffusion measurements in model membranes with an excess of free dye in solution. All SA-FCS measurements are directly compared to standard confocal FCS, demonstrating a clear advantage of SA-FCS, especially for diffusion measurements in membranes. We present an extensive theoretical framework that allows for accurate and quantitative evaluation of the SA-FCS correlation curves. PMID:17827221

  6. Velocity correlations of galaxy clusters

    NASA Technical Reports Server (NTRS)

    Cen, Renyue; Bahcall, Neta A.; Gramann, Mirt

    1994-01-01

    We determine the velocity correlation function, pairwise peculiar velocity difference, and rms pairwise peculiar velocity dispersion of rich clusters of galaxies, as a function of pair separation, for three cosmological models: Omega = 1 and Omega = 0.3 cold dark matter (CDM), and Omega = 0.3 primeval baryonic isocurvature (PBI) models (all flat and Cosmic Background Explorer (COBE)-normalized). We find that close cluster pairs, with separation r is less than or equal to 10/h Mpc, exhibit strong attractive peculiar velocities in all models; the cluster pairwise velocities depend sensitively on the model. The mean pairwise attractive velocity of clusters on 5/h Mpc scale ranges from approximately 1700 km/s for Omega = 1 CDM to approximately 1000 km/s for PBI to approximately 700 km/s for Omega = 0.3 CDM. The small-scale pairwise velocities depend also on cluster mass: richer, more massive clusters exhibit stronger attractive velocities than less massive clusters. On large scales, from approximately 20 to 200/h Mpc, the cluster peculiar velocities are increasingly dominated by bulk and random motions; they are independent of cluster mass. The cluster velocity correlation function is negative on small scales for Omega = 1 and Omega = 0.3 CDM, indicating strong pairwise motion relative to bulk motion on small scales; PBI exhibits relatively larger bulk motions. The cluster velocity correlation function is positive on very large scales, from r approximately 10/h Mpc to r approximately 200/h Mpc, for all models. These positive correlations, which decrease monotonically with scale, indicate significant bulk motions of clusters up to approximately 200/h Mpc. The strong dependence of the cluster velocity functions on models, especially at small separations, makes them useful tools in constraining cosmological models when compared with observations.

  7. Electron correlation energies in atoms

    NASA Astrophysics Data System (ADS)

    McCarthy, Shane Patrick

    This dissertation is a study of electron correlation energies Ec in atoms. (1) Accurate values of E c are computed for isoelectronic sequences of "Coulomb-Hooke" atoms with varying mixtures of Coulombic and Hooke character. (2) Coupled-cluster calculations in carefully designed basis sets are combined with fully converged second-order Moller-Plesset perturbation theory (MP2) computations to obtain fairly accurate, non-relativistic Ec values for the 12 closed-shell atoms from Ar to Rn. The complete basis-set (CBS) limits of MP2 energies are obtained for open-shell atoms by computations in very large basis sets combined with a knowledge of the MP2/CBS limit for the next larger closed-shell atom with the same valence shell structure. Then higher-order correlation corrections are found by coupled-cluster calculations using basis sets that are not quite as large. The method is validated for the open-shell atoms from Al to Cl and then applied to get E c values, probably accurate to 3%, for the 4th-period open-shell atoms: K, Sc-Cu, and Ga-Br. (3) The results show that, contrary to quantum chemical folklore, MP2 overestimates |Ec| for atoms beyond Fe. Spin-component scaling arguments are used to provide a simple explanation for this overestimation. (4) Eleven non-relativistic density functionals, including some of the most widely-used ones, are tested on their ability to predict non-relativistic, electron correlation energies for atoms and their cations. They all lead to relatively poor predictions for the heavier atoms. Several novel, few-parameter, density functionals for the correlation energy are developed heuristically. Four new functionals lead to improved predictions for the 4th-period atoms without unreasonably compromising accuracy for the lighter atoms. (5) Simple models describing the variation of E c with atomic number are developed.

  8. Correlation and simple linear regression.

    PubMed

    Eberly, Lynn E

    2007-01-01

    This chapter highlights important steps in using correlation and simple linear regression to address scientific questions about the association of two continuous variables with each other. These steps include estimation and inference, assessing model fit, the connection between regression and ANOVA, and study design. Examples in microbiology are used throughout. This chapter provides a framework that is helpful in understanding more complex statistical techniques, such as multiple linear regression, linear mixed effects models, logistic regression, and proportional hazards regression. PMID:18450049

  9. Correlated Temporal and Spectral Variability

    NASA Technical Reports Server (NTRS)

    Swank, Jean H.

    2007-01-01

    The variability of neutron star and black hole X-ray sources has several dimensions, because of the roles played by different important time-scales. The variations on time scales of hours, weeks, and months, ranging from 50% to orders of magnitude, arise out of changes in the flow in the disk. The most important driving forces for those changes are probably various possible instabilities in the disk, though there may be effects with other dominant causes. The changes in the rate of flow appear to be associated with changes in the flow's configuration, as the accreting material approaches the compact object, for there are generally correlated changes in both the Xray spectra and the character of the faster temporal variability. There has been a lot of progress in tracking these correlations, both for Z and Atoll neutron star low-mass X-ray binaries, and for black hole binaries. I will discuss these correlations and review briefly what they tell us about the physical states of the systems.

  10. Neuropsychological correlates of domestic violence.

    PubMed

    Cohen, R A; Rosenbaum, A; Kane, R L; Warnken, W J; Benjamin, S

    1999-01-01

    Neuropsychological functioning was assessed in 39 males who had committed domestic violence (batterers) and compared to 63 nonviolent (both maritally discordant and satisfied) subjects recruited by advertisement. Subjects were subsequently divided into two groups (head injured, nonhead injured) and these groups were also contrasted as a function of batterer status. Tests were administered to assess for cognitive and behavioral functions, including executive dysfunction, hypothesized to be a factor contributing to propensity for violence. Questionnaires and structured clinical interviews were used to assess marital discord, emotional distress, and violent behaviors. Batterers differed from nonbatterers across several cognitive domains: executive, learning, memory, and verbal functioning. Batterers were reliably discriminated from nonbatterers based on three neuropsychological tasks: Digit Symbol, Recognition Memory Test-Words, Wisconsin Card Sorting Test. Neuropsychological performance was the strongest correlate of domestic violence of all clinical variables measured. However, the inclusion of two other variables, severity of emotional distress and history of head injury, together with the neuropsychological indices provided the strongest correlation with batterers status. Among batterers, neuropsychological performance did not vary as a function of head injury status, indicating that while prior head injury was correlated with batterer status, it was not the sole basis for their impairments. The findings suggest that current cognitive status, prior brain injury, childhood academic problems, as well as psychosocial influences, contribute along with coexisting emotional distress to a propensity for domestic violence. PMID:10751047

  11. Quantum correlations beyond Tsirelson's bound

    NASA Astrophysics Data System (ADS)

    Berry, Dominic; Ringbauer, Martin; Fedrizzi, Alessandro; White, Andrew

    2014-03-01

    Violations of Bell inequalities show that there are correlations that cannot explained by any classical theory. Further violation, beyond Tsirelson's bound, shows that there are correlations that are not explained by quantum mechanics. Such super-quantum correlations would enable violation of information causality, where communication of one bit provides more than one bit of information [Nature 461, 1101 (2009)]. An unavoidable feature of all realistic Bell inequality experiments is loss. If one postselects on successful measurements, unentangled states can violate Bell inequalities. On the other hand, loss can be used to enhance the violation of Bell inequalities for entangled states. This can improve the ability to distinguish between entangled and unentangled states, despite loss. Here we report an optical experiment providing maximal violation of the CHSH-Bell inequality with entangled states. Due to loss and postselection, Tsirelson's bound is also violated. This enables us to more easily distinguish between entangled and unentangled states. In addition, it provides violation of information causality for the postselected data.

  12. Correlated genotypes in friendship networks

    PubMed Central

    Fowler, James H.; Settle, Jaime E.; Christakis, Nicholas A.

    2011-01-01

    It is well known that humans tend to associate with other humans who have similar characteristics, but it is unclear whether this tendency has consequences for the distribution of genotypes in a population. Although geneticists have shown that populations tend to stratify genetically, this process results from geographic sorting or assortative mating, and it is unknown whether genotypes may be correlated as a consequence of nonreproductive associations or other processes. Here, we study six available genotypes from the National Longitudinal Study of Adolescent Health to test for genetic similarity between friends. Maps of the friendship networks show clustering of genotypes and, after we apply strict controls for population stratification, the results show that one genotype is positively correlated (homophily) and one genotype is negatively correlated (heterophily). A replication study in an independent sample from the Framingham Heart Study verifies that DRD2 exhibits significant homophily and that CYP2A6 exhibits significant heterophily. These unique results show that homophily and heterophily obtain on a genetic (indeed, an allelic) level, which has implications for the study of population genetics and social behavior. In particular, the results suggest that association tests should include friends’ genes and that theories of evolution should take into account the fact that humans might, in some sense, be metagenomic with respect to the humans around them. PMID:21245293

  13. Wolfram syndrome: a clinicopathologic correlation

    PubMed Central

    Merchant, Saumil N.; Adams, Joe C.; Joseph, Jeffrey T.

    2009-01-01

    Wolfram syndrome or DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy and deafness) is a neurodegenerative disorder characterized by diabetes mellitus and optic atrophy as well as diabetes insipidus and deafness in many cases. We report the post-mortem neuropathologic findings of a patient with Wolfram syndrome and correlate them with his clinical presentation. In the hypothalamus, neurons in the paraventricular and supraoptic nuclei were markedly decreased and minimal neurohypophyseal tissue remained in the pituitary. The pontine base and inferior olivary nucleus showed gross shrinkage and neuron loss, while the cerebellum was relatively unaffected. The visual system had moderate to marked loss of retinal ganglion neurons, commensurate loss of myelinated axons in the optic nerve, chiasm and tract, and neuron loss in the lateral geniculate nucleus but preservation of the primary visual cortex. The patient’s inner ear showed loss of the organ of Corti in the basal turn of the cochleae and mild focal atrophy of the stria vascularis. These findings correlated well with the patient’s high-frequency hearing loss. The pathologic findings correlated closely with the patient’s clinical symptoms and further support the concept of Wolfram syndrome as a neurodegenerative disorder. Our findings extend prior neuropathologic reports of Wolfram syndrome by providing contributions to our understanding of eye, inner ear and olivopontine pathology in this disease. PMID:19449020

  14. PREFACE: Strongly correlated electron systems Strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Saxena, Siddharth S.; Littlewood, P. B.

    2012-07-01

    This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The selected papers derived from invited presentations seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The focus is on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity and metal-insulator transitions. Both experimental and theoretical work is presented. Based on fundamental advances in the understanding of electronic materials, much of 20th century materials physics was driven by miniaturisation and integration in the electronics industry to the current generation of nanometre scale devices. The achievements of this industry have brought unprecedented advances to society and well-being, and no doubt there is much further to go—note that this progress is founded on investments and studies in the fundamentals of condensed matter physics from more than 50 years ago. Nevertheless, the defining challenges for the 21st century will lie in the discovery in science, and deployment through engineering, of technologies that can deliver the scale needed to have an impact on the sustainability agenda. Thus the big developments in nanotechnology may lie not in the pursuit of yet smaller transistors, but in the design of new structures that can revolutionise the performance of solar cells, batteries, fuel cells, light-weight structural materials, refrigeration, water purification, etc. The science presented in the papers of this special section also highlights the underlying interest in energy-dense materials, which

  15. Manifest and concealed correlations in quantum mechanics

    NASA Astrophysics Data System (ADS)

    de la Torre, A. C.; Iguain, J. L.

    1998-11-01

    The quantum covariance function is used to study correlations in quantum systems. Besides the obvious correlations due to the conservation of some quantity, the appearance of concealed quantum correlations like non-locality or non-separability is studied. The choice of an appropriate basis allows a complete analysis relating correlations with conservation laws and factorizability.

  16. Iterative method for generating correlated binary sequences

    NASA Astrophysics Data System (ADS)

    Usatenko, O. V.; Melnik, S. S.; Apostolov, S. S.; Makarov, N. M.; Krokhin, A. A.

    2014-11-01

    We propose an efficient iterative method for generating random correlated binary sequences with a prescribed correlation function. The method is based on consecutive linear modulations of an initially uncorrelated sequence into a correlated one. Each step of modulation increases the correlations until the desired level has been reached. The robustness and efficiency of the proposed algorithm are tested by generating sequences with inverse power-law correlations. The substantial increase in the strength of correlation in the iterative method with respect to single-step filtering generation is shown for all studied correlation functions. Our results can be used for design of disordered superlattices, waveguides, and surfaces with selective transport properties.

  17. Correlation, functional analysis and optical pattern recognition

    SciTech Connect

    Dickey, F.M.; Lee, M.L.; Stalker, K.T.

    1994-03-01

    Correlation integrals have played a central role in optical pattern recognition. The success of correlation, however, has been limited. What is needed is a mathematical operation more complex than correlation. Suitably complex operations are the functionals defined on the Hilbert space of Lebesgue square integrable functions. Correlation is a linear functional of a parameter. In this paper, we develop a representation of functionals in terms of inner products or equivalently correlation functions. We also discuss the role of functionals in neutral networks. Having established a broad relation of correlation to pattern recognition, we discuss the computation of correlation functions using acousto-optics.

  18. Synthesis of a water-soluble analog of 6-methyl-3-N-alkyl catechol labeled with carbon 13: NMR approach to the reactivity of poison ivy/oak sensitizers toward proteins.

    PubMed

    Goetz, G; Meschkat, E; Lepoittevin, J P

    1999-04-19

    A 13-C labeled water soluble derivative of alkylcatechol was synthesized and reacted with human serum albumin in phosphate buffer at pH 7.4 in air to allow a slow oxidation of the catechol into orthoquinone. The formation of several adducts was evidenced by a combination of 13C and 1H-13C correlation NMR. Although some adducts could result from a classical o-quinone formation - Michael type addition, our results suggest that a second pathway, involving a direct reaction of a carbon centered radical with proteins could be an important mechanism in the formation of modified proteins. PMID:10328301

  19. Bioactive terpenes from the soft coral Heteroxenia sp. from Mindoro, Philippines.

    PubMed

    Edrada, R A; Wray, V; Witte, L; van Ofwegen, L; Proksch, P

    2000-01-01

    A marine soft coral species of the genus Heteroxenia collected from Mindoro Island, Philippines yielded two cadinene sesquiterpenes, (+)-alpha-muurolene (1) and a novel derivative (+)-6-hydroxy-alpha-muurolene (2), as well as the biologically active polyhydroxysterol, sarcoaldosterol A (3). The structure of the novel compound was unambiguously established on the basis of NMR spectroscopic (1H, 13C, COSY, 1H-detected direct and long range 13C-1H correlations) and mass spectrometric (EIMS) data. All compounds were active against the phytopathogenic fungus Cladosporium cucumerinum. The isolated terpenes were also active in the brine shrimp lethality test. PMID:10739105

  20. Variable Selection through Correlation Sifting

    NASA Astrophysics Data System (ADS)

    Huang, Jim C.; Jojic, Nebojsa

    Many applications of computational biology require a variable selection procedure to sift through a large number of input variables and select some smaller number that influence a target variable of interest. For example, in virology, only some small number of viral protein fragments influence the nature of the immune response during viral infection. Due to the large number of variables to be considered, a brute-force search for the subset of variables is in general intractable. To approximate this, methods based on ℓ1-regularized linear regression have been proposed and have been found to be particularly successful. It is well understood however that such methods fail to choose the correct subset of variables if these are highly correlated with other "decoy" variables. We present a method for sifting through sets of highly correlated variables which leads to higher accuracy in selecting the correct variables. The main innovation is a filtering step that reduces correlations among variables to be selected, making the ℓ1-regularization effective for datasets on which many methods for variable selection fail. The filtering step changes both the values of the predictor variables and output values by projections onto components obtained through a computationally-inexpensive principal components analysis. In this paper we demonstrate the usefulness of our method on synthetic datasets and on novel applications in virology. These include HIV viral load analysis based on patients' HIV sequences and immune types, as well as the analysis of seasonal variation in influenza death rates based on the regions of the influenza genome that undergo diversifying selection in the previous season.

  1. Correlates of increased sexual satisfaction.

    PubMed

    Haavio-Mannila, E; Kontula, O

    1997-08-01

    Comparisons of nationally representative survey data of the population ages 18-54 years in 1971 (N = 2252) and 1992 (N = 1718) from Finland show that sexual satisfaction has greatly increased particularly among women. Some predictors of sexual satisfaction of men and women are examined on the basis of the 1992 survey data on people ages 18-74 years (N = 2250). Correlations between social background factors, sexual ideas and assertiveness, optional relationships, sexual practices, organism, and satisfaction with sexual intercourse were calculated. To control the simultaneous effect of the variables explaining satisfaction, path analyses were conducted. Results show that young age, a sexually unreserved and a nonreligious childhood home, early start of sexual life, high education, sexual assertiveness, considering sexuality important in life, reciprocal feeling of love, use of sex materials, frequent intercourse, many-sided (versatile) sexual techniques, and frequent orgasm correlate with finding sexual intercourse pleasurable. There were some gender differences in the connections between the independent factors and satisfaction with coitus. The importance of sexuality in life, love, and the use of sexual materials were connected directly to physical sexual satisfaction among men but only indirectly among women. For women, but not for men, young age and early start of sexual life correlated with enjoyment of intercourse. The greater sexual dissatisfaction of women compared to men, which still prevails, may be due to their late start of sexual life, conservative sexual attitudes, unimportance of sexuality in life, lack of sexual assertiveness, and use of restricted sexual techniques. The emancipation of women may change these ideas and practices of women. This might lessen the gender gap in physical sexual satisfaction. PMID:9251837

  2. Correlation-induced spectral changes

    NASA Astrophysics Data System (ADS)

    Wolf, Emil; James, Daniel F. V.

    1996-06-01

    This paper presents a review of research, both theoretical and experimental, concerning the influence of coherence properties of fluctuating light sources and of correlation properties of scattering media on the spectra of radiated and scattered fields. Much of this research followed a discovery made in 1986, that the spectrum of light may change on propagation, even in free space. More than 100 papers on this topic have been published to date and many of them are reviewed, or at least mentioned, in this article. After an introduction and a summary of some of the main mathematical results relating to second-order coherence theory of statistically stationary optical fields, spectral changes that may take place on superposing fields produced by two partially correlated sources are discussed. Spectral effects in fields produced by two-dimensional secondary sources and by three-dimensional primary sources are then considered. The section which follows describes spectral changes that may arise when polychromatic light is scattered on media whose physical properties vary randomly either in space and/or in time. A review is also presented of recent research, which has revealed that under certain circumstances the changes in the spectrum of light scattered on random media may imitate the Doppler effect, even though the source, the medium and the observer are all at rest with respect to one another. In the final section a brief review is given of a new emerging technique sometimes called spatial-coherence spectroscopy. It is based on the discovery that it is possible, under certain circumstances, to determine field correlations from spectral measurements.

  3. Precision protection through indirect correlations

    NASA Astrophysics Data System (ADS)

    Jin, Yao

    2016-04-01

    The dynamics of the quantum Fisher information of the parameters of the initial atomic state is studied, in the framework of open quantum systems, for a pair of static two-level atoms coupled to a bath of fluctuating vacuum scalar fields. Our results show that the correlations between the two atoms as well as the precision limit in quantum metrology are determined by the separation between the two atoms. Remarkably, when the separation between the two atoms approaches zero, the quantum Fisher information, thus the precision limit of the estimation of the parameters of the initial atomic state will be survived from the vacuum fluctuations after long time evolution.

  4. Boundary anomalies and correlation functions

    NASA Astrophysics Data System (ADS)

    Huang, Kuo-Wei

    2016-08-01

    It was shown recently that boundary terms of conformal anomalies recover the universal contribution to the entanglement entropy and also play an important role in the boundary monotonicity theorem of odd-dimensional quantum field theories. Motivated by these results, we investigate relationships between boundary anomalies and the stress tensor correlation functions in conformal field theories. In particular, we focus on how the conformal Ward identity and the renormalization group equation are modified by boundary central charges. Renormalized stress tensors induced by boundary Weyl invariants are also discussed, with examples in spherical and cylindrical geometries.

  5. Speeding up local correlation methods

    NASA Astrophysics Data System (ADS)

    Kats, Daniel

    2014-12-01

    We present two techniques that can substantially speed up the local correlation methods. The first one allows one to avoid the expensive transformation of the electron-repulsion integrals from atomic orbitals to virtual space. The second one introduces an algorithm for the residual equations in the local perturbative treatment that, in contrast to the standard scheme, does not require holding the amplitudes or residuals in memory. It is shown that even an interpreter-based implementation of the proposed algorithm in the context of local MP2 method is faster and requires less memory than the highly optimized variants of conventional algorithms.

  6. Speeding up local correlation methods

    SciTech Connect

    Kats, Daniel

    2014-12-28

    We present two techniques that can substantially speed up the local correlation methods. The first one allows one to avoid the expensive transformation of the electron-repulsion integrals from atomic orbitals to virtual space. The second one introduces an algorithm for the residual equations in the local perturbative treatment that, in contrast to the standard scheme, does not require holding the amplitudes or residuals in memory. It is shown that even an interpreter-based implementation of the proposed algorithm in the context of local MP2 method is faster and requires less memory than the highly optimized variants of conventional algorithms.

  7. Biological correlates of binge eating.

    PubMed

    Yanovski, S Z

    1995-01-01

    Eating disorders are associated with numerous biological perturbations; however, sorting out cause from effect is difficult. Neuroendocrine and metabolic abnormalities are seen in both anorexia nervosa and bulimia nervosa, but they have not been described in binge eating disorder, in which neither starvation nor compensatory behaviors are present. Although these findings may reflect biologic differences among subgroups of binge eaters, an alternative explanation is that many of the biological correlates of binge eating are the result of metabolic derangement secondary to starvation and/or purging. The identification of binge eating disorder provides an opportunity to study the causes and concomitants of binge eating in the absence of compensatory behaviors. PMID:8820523

  8. Preselected Sub-Poissonian Correlations

    NASA Technical Reports Server (NTRS)

    Pavicic, Mladen

    1996-01-01

    The simplest possible photon-number-squeezed states containing only two photons and exhibiting sub-poissonian statistics with the Fano factor approaching 0.5 have been used for a proposal of a loophole-free Bell experiment requiring only 67 percent of detection efficiency. The states are obtained by the fourth order interference first of two downconverted photons at an asymmetrical beam splitter and thereupon of two photons from two independent singlets at an asymmetrical beam splitter. In the latter set-up, the other two photons which nowhere interacted and whose paths never crossed appear entangled in a singlet-like correlated state.

  9. Short Range Correlations in Nuclei

    SciTech Connect

    L. B. Weinstein

    2006-11-01

    Short range correlations (SRC) are an extremely important part of nuclear structure. They are responsible for the high momentum part of the nuclear wavefunction. Instantaneous densities can significantly exceed the average neutron star density. Recent (e,e[prime]) measurements at Jefferson Lab have shown that SRC are universal in nuclei from deuterium to gold, that the probability of two-nucleon SRC is 5-25%, and that the probability of three-nucleon SRC is less than 1%. Recent (e,e[prime]pn) measurements have measured the SRC probabilities as a function of proton momentum and have measured the joint NN momentum distributions.

  10. Development of "active correlation" technique

    NASA Astrophysics Data System (ADS)

    Tsyganov, Yu. S.

    2016-01-01

    With reaching to extremely high intensities of heavy-ion beams new requirements for the detection system of the Dubna Gas-Filled Recoil Separator (DGFRS) will definitely be set. One of the challenges is how to apply the "active correlations" method to suppress beam associated background products without significant losses in the whole long-term experiment efficiency value. Different scenarios and equations to develop the method according this requirement are under consideration in the present paper. The execution time to estimate the dead time parameter associated with the optimal choice of the life-time parameter is presented.

  11. Correlation dimension of complex networks.

    PubMed

    Lacasa, Lucas; Gómez-Gardeñes, Jesús

    2013-04-19

    We propose a new measure to characterize the dimension of complex networks based on the ergodic theory of dynamical systems. This measure is derived from the correlation sum of a trajectory generated by a random walker navigating the network, and extends the classical Grassberger-Procaccia algorithm to the context of complex networks. The method is validated with reliable results for both synthetic networks and real-world networks such as the world air-transportation network or urban networks, and provides a computationally fast way for estimating the dimensionality of networks which only relies on the local information provided by the walkers. PMID:23679650

  12. Pairing Correlations at High Spins

    NASA Astrophysics Data System (ADS)

    Ma, Hai-Liang; Dong, Bao-Guo; Zhang, Yan; Fan, Ping; Yuan, Da-Qing; Zhu, Shen-Yun; Zhang, Huan-Qiao; Petrache, C. M.; Ragnarsson, I.; Carlsson, B. G.

    The pairing correcting energies at high spins in 161Lu and 138Nd are studied by comparing the results of the cranked-Nilsson-Strutinsky (CNS) and cranked-Nilsson-Strutinsky-Bogoliubov (CNSB) models. It is concluded that the Coriolis effect rather than the rotational alignment effect plays a major role in the reduction of the pairing correlations in the high spin region. Then we proposed an average pairing correction method which not only better reproduces the experimental data comparing with the CNS model but also enables a clean-cut tracing of the configurations thus the full-spin-range discussion on the various rotating bands.

  13. EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Ronning, Filip; Batista, Cristian

    2011-03-01

    Strongly correlated electrons is an exciting and diverse field in condensed matter physics. This special issue aims to capture some of that excitement and recent developments in the field. Given that this issue was inspired by the 2010 International Conference on Strongly Correlated Electron Systems (SCES 2010), we briefly give some history in order to place this issue in context. The 2010 International Conference on Strongly Correlated Electron Systems was held in Santa Fe, New Mexico, a reunion of sorts from the 1989 International Conference on the Physics of Highly Correlated Electron Systems that also convened in Santa Fe. SCES 2010—co-chaired by John Sarrao and Joe Thompson—followed the tradition of earlier conferences, in this century, hosted by Buzios (2008), Houston (2007), Vienna (2005), Karlsruhe (2004), Krakow (2002) and Ann Arbor (2001). Every three years since 1997, SCES has joined the International Conference on Magnetism (ICM), held in Recife (2000), Rome (2003), Kyoto (2006) and Karlsruhe (2009). Like its predecessors, SCES 2010 topics included strongly correlated f- and d-electron systems, heavy-fermion behaviors, quantum-phase transitions, non-Fermi liquid phenomena, unconventional superconductivity, and emergent states that arise from electronic correlations. Recent developments from studies of quantum magnetism and cold atoms complemented the traditional subjects and were included in SCES 2010. 2010 celebrated the 400th anniversary of Santa Fe as well as the birth of astronomy. So what's the connection to SCES? The Dutch invention of the first practical telescope and its use by Galileo in 1610 and subsequent years overturned dogma that the sun revolved about the earth. This revolutionary, and at the time heretical, conclusion required innovative combinations of new instrumentation, observation and mathematics. These same combinations are just as important 400 years later and are the foundation of scientific discoveries that were discussed

  14. Solvation and crystal effects in bilirubin studied by NMR spectroscopy and density functional theory.

    PubMed

    Rohmer, Thierry; Matysik, Jörg; Mark, Franz

    2011-10-27

    The open-chain tetrapyrrole compound bilirubin was investigated in chloroform and dimethyl sulfoxide solutions by liquid-state NMR and as solid by (1)H, (13)C, and (15)N magic-angle spinning (MAS) solid-state NMR spectroscopy. Density functional theory (DFT) calculations were performed to interpret the data, using the B3LYP exchange-correlation functional to optimize geometries and to compute NMR chemical shieldings by the gauge-including atomic orbital method. The dependence of geometries and chemical shieldings on the size of the basis sets was investigated for the reference molecules tetramethylsilane, NH(3), and H(2)O, and for bilirubin as a monomer and in clusters consisting of up to six molecules. In order to assess the intrinsic errors of the B3LYP approximation in calculating NMR shieldings, complete basis set estimates were obtained for the nuclear shielding values of the reference molecules. The experimental liquid-state NMR data of bilirubin are well reproduced by a monomeric bilirubin molecule using the 6-311+G(2d,p) basis set for geometry optimization and for calculating chemical shieldings. To simulate the bilirubin crystal, a hexameric model was required. It was constructed from geometry-optimized monomers using information from the X-ray structure of bilirubin to fix the monomeric entities in space and refined by partial optimization. Combining experimental (1)H-(13)C and (1)H-(15)N NMR correlation spectroscopy and density functional theory, almost complete sets of (1)H, (13)C, and (15)N chemical shift assignments were obtained for both liquid and solid states. It is shown that monomeric bilirubin in chloroform solution is formed by 3-vinyl anti conformers, while bilirubin crystals are formed by 3-vinyl syn conformers. This conformational change leads to characteristic differences between the liquid- and solid-state NMR resonances. PMID:21846145

  15. Strongly correlated perovskite fuel cells.

    PubMed

    Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D; Ramanathan, Shriram

    2016-06-01

    Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations. PMID:27279218

  16. Fiducial marker for correlating images

    DOEpatents

    Miller, Lisa Marie; Smith, Randy J.; Warren, John B.; Elliott, Donald

    2011-06-21

    The invention relates to a fiducial marker having a marking grid that is used to correlate and view images produced by different imaging modalities or different imaging and viewing modalities. More specifically, the invention relates to the fiducial marking grid that has a grid pattern for producing either a viewing image and/or a first analytical image that can be overlaid with at least one other second analytical image in order to view a light path or to image different imaging modalities. Depending on the analysis, the grid pattern has a single layer of a certain thickness or at least two layers of certain thicknesses. In either case, the grid pattern is imageable by each imaging or viewing modality used in the analysis. Further, when viewing a light path, the light path of the analytical modality cannot be visualized by viewing modality (e.g., a light microscope objective). By correlating these images, the ability to analyze a thin sample that is, for example, biological in nature but yet contains trace metal ions is enhanced. Specifically, it is desired to analyze both the organic matter of the biological sample and the trace metal ions contained within the biological sample without adding or using extrinsic labels or stains.

  17. Correlated metals as transparent conductors.

    PubMed

    Zhang, Lei; Zhou, Yuanjun; Guo, Lu; Zhao, Weiwei; Barnes, Anna; Zhang, Hai-Tian; Eaton, Craig; Zheng, Yuanxia; Brahlek, Matthew; Haneef, Hamna F; Podraza, Nikolas J; Chan, Moses H W; Gopalan, Venkatraman; Rabe, Karin M; Engel-Herbert, Roman

    2016-02-01

    The fundamental challenge for designing transparent conductors used in photovoltaics, displays and solid-state lighting is the ideal combination of high optical transparency and high electrical conductivity. Satisfying these competing demands is commonly achieved by increasing carrier concentration in a wide-bandgap semiconductor with low effective carrier mass through heavy doping, as in the case of tin-doped indium oxide (ITO). Here, an alternative design strategy for identifying high-conductivity, high-transparency metals is proposed, which relies on strong electron-electron interactions resulting in an enhancement in the carrier effective mass. This approach is experimentally verified using the correlated metals SrVO3 and CaVO3, which, despite their high carrier concentration (>2.2 × 10(22) cm(-3)), have low screened plasma energies (<1.33 eV), and demonstrate excellent performance when benchmarked against ITO. A method is outlined to rapidly identify other candidates among correlated metals, and strategies are proposed to further enhance their performance, thereby opening up new avenues to develop transparent conductors. PMID:26657329

  18. Correlated metals as transparent conductors

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Zhou, Yuanjun; Guo, Lu; Zhao, Weiwei; Barnes, Anna; Zhang, Hai-Tian; Eaton, Craig; Zheng, Yuanxia; Brahlek, Matthew; Haneef, Hamna F.; Podraza, Nikolas J.; Chan, Moses H. W.; Gopalan, Venkatraman; Rabe, Karin M.; Engel-Herbert, Roman

    2016-02-01

    The fundamental challenge for designing transparent conductors used in photovoltaics, displays and solid-state lighting is the ideal combination of high optical transparency and high electrical conductivity. Satisfying these competing demands is commonly achieved by increasing carrier concentration in a wide-bandgap semiconductor with low effective carrier mass through heavy doping, as in the case of tin-doped indium oxide (ITO). Here, an alternative design strategy for identifying high-conductivity, high-transparency metals is proposed, which relies on strong electron-electron interactions resulting in an enhancement in the carrier effective mass. This approach is experimentally verified using the correlated metals SrVO3 and CaVO3, which, despite their high carrier concentration (>2.2 × 1022 cm-3), have low screened plasma energies (<1.33 eV), and demonstrate excellent performance when benchmarked against ITO. A method is outlined to rapidly identify other candidates among correlated metals, and strategies are proposed to further enhance their performance, thereby opening up new avenues to develop transparent conductors.

  19. A correlated nickelate synaptic transistor

    NASA Astrophysics Data System (ADS)

    Shi, Jian; Ha, Sieu D.; Zhou, You; Schoofs, Frank; Ramanathan, Shriram

    2013-10-01

    Inspired by biological neural systems, neuromorphic devices may open up new computing paradigms to explore cognition, learning and limits of parallel computation. Here we report the demonstration of a synaptic transistor with SmNiO3, a correlated electron system with insulator-metal transition temperature at 130°C in bulk form. Non-volatile resistance and synaptic multilevel analogue states are demonstrated by control over composition in ionic liquid-gated devices on silicon platforms. The extent of the resistance modulation can be dramatically controlled by the film microstructure. By simulating the time difference between postneuron and preneuron spikes as the input parameter of a gate bias voltage pulse, synaptic spike-timing-dependent plasticity learning behaviour is realized. The extreme sensitivity of electrical properties to defects in correlated oxides may make them a particularly suitable class of materials to realize artificial biological circuits that can be operated at and above room temperature and seamlessly integrated into conventional electronic circuits.

  20. CCD correlated quadruple sampling processor

    NASA Technical Reports Server (NTRS)

    Gaalema, S. D. (Inventor)

    1981-01-01

    A correlated quadruple sampling processor for improved signal-to-noise ratio in the output of a charge-coupled device (CCD) is comprised of: switching means for momentarily clamping a CCD signal line at a first reference level A before a CCD data pulse and then obtaining a first data sample B with respect to the reference A during a CCD data pulse, and storing the positive sample B-A; switching means for momentarily clamping the CCD signal line a second time at the level C during the presence of the CCD data pulse and then obtaining a second data sample D with respect to the reference level C after the CCD data pulse, and storing the negative sample D-C; and means for obtaining the difference between the stored samples +(B-A) and -(D-C), thus increasing the net signal amplitude by a factor of about 2 while the noise would be increased by only a factor of square root of 2 since there will be no correlation in the noise between the double samples +(B-A) and -(D-C) effectively added.

  1. PREFACE: Correlation Dynamics in Nuclei

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshio; Otsuka, Takaharu; Ichimura, Munetake

    2005-01-01

    The International Symposium on `Correlation Dynamics in Nuclei' was held at the Sanjo Kaikan, the University of Tokyo, from the 31 January to 4 February 2005. This symposium was organized on the occasion of the 50th anniversary of the Configuration Mixing theory of Arima and Horie. The symposium was hosted by the University of Tokyo, and supported by the Inoue Foundation for Science, the Japan Atomic Energy Research Institute and the Ministry of Education, Culture, Sports, Science and Technology. The purpose of the symposium was to discuss theoretical and experimental developments and future prospects in physics of correlation dynamics in nuclei, including topics such as effective interactions, shell model studies of configuration mixing and spin-isospin modes in nuclei. It was shown in many ways and angles that the Arima-Horie theory has been a starting point of a variety of developments of the studies in these fields over many decades. The developments have been enhanced by the expansion of computational capabilities and the progress in accelerators, detectors and radioactive beam facilities. We enjoyed 28 excellent and lively invited talks and 30 oral presentations in the symposium with about 90 participants. A special session was dedicated to celebrate the 80th birthday of Professor Igal Talmi, who made invaluable and pioneering works in the shell model theory. Finally, we would like to thank all the speakers and the participants as well as the other organizers for their contributions which made the symposium very successful.

  2. Strongly correlated perovskite fuel cells

    NASA Astrophysics Data System (ADS)

    Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D.; Ramanathan, Shriram

    2016-06-01

    Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations.

  3. ASTROCHEMICAL CORRELATIONS IN MOLECULAR CLOUDS

    SciTech Connect

    Gaches, Brandt A. L.; Offner, Stella S. R.; Rosolowsky, Erik W.; Bisbas, Thomas G. E-mail: soffner@astro.umass.edu E-mail: tb@star.ucl.ac.uk

    2015-02-01

    We investigate the spectral correlations between different species used to observe molecular clouds. We use hydrodynamic simulations and a full chemical network to study the abundances of over 150 species in typical Milky Way molecular clouds. We perform synthetic observations in order to produce emission maps of a subset of these tracers. We study the effects of different lines of sight and spatial resolution on the emission distribution and perform a robust quantitative comparison of the species to each other. We use the Spectral Correlation Function (SCF), which quantifies the root mean squared difference between spectra separated by some length scale, to characterize the structure of the simulated cloud in position-position-velocity (PPV) space. We predict the observed SCF for a broad range of observational tracers, and thus identify homologous species. In particular, we show that the pairs C and CO, C{sup +} and CN, and NH{sub 3} and H{sub 2}CS have very similar SCFs. We measure the SCF slope variation as a function of beam size for all species and demonstrate that the beam size has a distinct effect on different species emission. However, for beams of up to 10'', placing the cloud at 1 kpc, the change is not large enough to move the SCF slopes into different regions of parameter space. The results from this study provide observational guidance for choosing the best tracer to probe various cloud length scales.

  4. Oral health correlates of captivity.

    PubMed

    Kapoor, Varsha; Antonelli, Tyler; Parkinson, Jennifer A; Hartstone-Rose, Adam

    2016-08-01

    The predominant diet fed to captive carnivores in North America consists of ground meat formulated to provide full nutritional requirements. However, this ground meat diet completely lacks the mechanical properties (i.e., toughness and hardness) of the foods these animals would consume in the wild. The goal of this study is to evaluate the effect of captivity on oral health by comparing the prevalence of periodontal disease and dental calculus accumulation in wild and captive lions and tigers (Panthera leo and Panthera tigris), and to also correlate oral health with cranial morphology in these specimens. To achieve this, 34 adult lion and 29 adult tiger skulls were scored for the presence and extent of dental calculus and periodontal disease. These oral health scores were also compared to cranial deformations examined in a previous study. We found that the occurrence and severity of calculus buildup and periodontal disease was significantly higher in captive felids compared to their wild counterparts. Further, higher calculus accumulation occurred on the posterior teeth when compared to the anterior teeth, while an opposite trend for periodontal disease was observed. We also found a significant correlation between oral health and cranial morphology of lions and tigers. The results suggest that food mechanical properties are significant factors contributing to oral health in felids. PMID:27473998

  5. The Neurogenetic Correlates of Consciousness

    NASA Astrophysics Data System (ADS)

    Grandy, John K.

    2013-09-01

    The neurogenetic correlates of consciousness (NgCC) is a new field of consciousness studies that focuses on genes that have an effect on or are involved in the continuum of neuron-based consciousness. A framework of consciousness based on the neural correlates of consciousness (NCC) has already been established by Francis Crick and Christof Kock. In this work I propose that there are NgCC underlying the NCC which are both active during the conscious experience. So how are genes involved? There are two significant connections between DNA and neurons that are involved in the conscious experience. First, any brain system can be adversely affected by underlying genetic abnormalities which can be expressed in an individual at birth, in adulthood, or later in life. Second, the DNA molecule does not lay dormant while the neuron runs on autopilot. DNA is active in translating and transcribing RNA and protein products that are utilized during neuron functioning. Without these products being continuously produced by the DNA during a conscious experience the neurons would cease to function correctly and be rendered unable to provide a continuum of human consciousness. Consequently, in addition to NCC, NgCC must be factored in when appreciating a conscious event. In this work I will discuss and explain some NgCC citing several examples.

  6. A correlated nickelate synaptic transistor.

    PubMed

    Shi, Jian; Ha, Sieu D; Zhou, You; Schoofs, Frank; Ramanathan, Shriram

    2013-01-01

    Inspired by biological neural systems, neuromorphic devices may open up new computing paradigms to explore cognition, learning and limits of parallel computation. Here we report the demonstration of a synaptic transistor with SmNiO₃, a correlated electron system with insulator-metal transition temperature at 130°C in bulk form. Non-volatile resistance and synaptic multilevel analogue states are demonstrated by control over composition in ionic liquid-gated devices on silicon platforms. The extent of the resistance modulation can be dramatically controlled by the film microstructure. By simulating the time difference between postneuron and preneuron spikes as the input parameter of a gate bias voltage pulse, synaptic spike-timing-dependent plasticity learning behaviour is realized. The extreme sensitivity of electrical properties to defects in correlated oxides may make them a particularly suitable class of materials to realize artificial biological circuits that can be operated at and above room temperature and seamlessly integrated into conventional electronic circuits. PMID:24177330

  7. Correlations in cosmic density fields

    NASA Technical Reports Server (NTRS)

    Bromley, B. C.

    1994-01-01

    A method is proposed to place constraints on the functional form of the high-order correlation functions zeta(sub n) that arise in cosmic density fields at large scales. This technique is based on a mass-in-cell statistic and a difference of mass in partitions of a cell. The relationship between these measures is sensitive to the formal structure of the zeta(sub n) as well as their amplitudes. This relationship is quantified in several theoretical models of structure, based on the hierarchical clustering paradigm. The results lead to a test for specific types of hierarchical clustering that is sensitive to correlations of all orders. The method is applied to examples of simulated large-scaled structure dominated by cold dark matter. In the preliminary study, the hierarchical paradigm appears to be a realistic approximation over a broad range of the scales. Furthermore, there is evidence that graphs of low-order vertices are dominant. On the basis of simulated data a phenomological model is specified that gives a good representation of clustering from linear scales to the strongly clustered regime (zeta(sub 2) approximately 500).

  8. Dipolar correlations in liquid water

    SciTech Connect

    Zhang, Cui; Galli, Giulia

    2014-08-28

    We present an analysis of the dipolar correlations in water as a function of temperature and density and in the presence of simple ionic solutes, carried out using molecular dynamics simulations and empirical potentials. We show that the dipole-dipole correlation function of the liquid exhibits sizable oscillations over nanodomains of about 1.5 nm radius, with several isosbestic points as a function of temperature; the size of the nanodomains is nearly independent on temperature and density, between 240 and 400 K and 0.9 and 1.3 g/cm{sup 3}, but it is substantially affected by the presence of solvated ions. In the same range of thermodynamic conditions, the decay time (τ) of the system dipole moment varies by a factor of about 30 and 1.5, as a function of temperature and density, respectively. At 300 K, we observed a maximum in τ as a function of density, and a corresponding shallow maximum in the tetrahedral order parameter, in a range where the diffusion coefficient, the pressure and the dielectric constant increase monotonically.

  9. The dynamics of correlated novelties.

    PubMed

    Tria, F; Loreto, V; Servedio, V D P; Strogatz, S H

    2014-01-01

    Novelties are a familiar part of daily life. They are also fundamental to the evolution of biological systems, human society, and technology. By opening new possibilities, one novelty can pave the way for others in a process that Kauffman has called "expanding the adjacent possible". The dynamics of correlated novelties, however, have yet to be quantified empirically or modeled mathematically. Here we propose a simple mathematical model that mimics the process of exploring a physical, biological, or conceptual space that enlarges whenever a novelty occurs. The model, a generalization of Polya's urn, predicts statistical laws for the rate at which novelties happen (Heaps' law) and for the probability distribution on the space explored (Zipf's law), as well as signatures of the process by which one novelty sets the stage for another. We test these predictions on four data sets of human activity: the edit events of Wikipedia pages, the emergence of tags in annotation systems, the sequence of words in texts, and listening to new songs in online music catalogues. By quantifying the dynamics of correlated novelties, our results provide a starting point for a deeper understanding of the adjacent possible and its role in biological, cultural, and technological evolution. PMID:25080941

  10. Exact exchange for correlated electrons

    NASA Astrophysics Data System (ADS)

    Novák, P.; Kune?, J.; Chaput, L.; Pickett, W. E.

    The cover picture is taken from the article by Pavel Novák that was chosen as Editor's Choice of this issue [1]. The figure shows the density of minority spin states in nickel oxide calculated by three commonly used approximations (LSDA, GGA, LDA+U) as well as using the newly proposed ?Exact Exchange for Correlated Electrons? (EECE) method. The EECE method treats the interactions between correlated electrons in a Hartree-Fock way, while all other interactions are described by the density functional theory. EECE is a promising starting point for the improvement of orbital-dependent functionals within the density functional theory.Pavel Novák is the head of the ?Spectroscopy of Magnetic Oxides? group at the Institute of Physics of ASCR, Prague, Czech Republic. Most of his scientific activity is devoted to the calculation of the electronic structure of solids, but he also closely cooperates with several experimental groups. Particular attention is focused on the nuclear magnetic resonance and electronic structure of magnetic oxides with mixed valency of the cations

  11. The dynamics of correlated novelties

    NASA Astrophysics Data System (ADS)

    Tria, F.; Loreto, V.; Servedio, V. D. P.; Strogatz, S. H.

    2014-07-01

    Novelties are a familiar part of daily life. They are also fundamental to the evolution of biological systems, human society, and technology. By opening new possibilities, one novelty can pave the way for others in a process that Kauffman has called ``expanding the adjacent possible''. The dynamics of correlated novelties, however, have yet to be quantified empirically or modeled mathematically. Here we propose a simple mathematical model that mimics the process of exploring a physical, biological, or conceptual space that enlarges whenever a novelty occurs. The model, a generalization of Polya's urn, predicts statistical laws for the rate at which novelties happen (Heaps' law) and for the probability distribution on the space explored (Zipf's law), as well as signatures of the process by which one novelty sets the stage for another. We test these predictions on four data sets of human activity: the edit events of Wikipedia pages, the emergence of tags in annotation systems, the sequence of words in texts, and listening to new songs in online music catalogues. By quantifying the dynamics of correlated novelties, our results provide a starting point for a deeper understanding of the adjacent possible and its role in biological, cultural, and technological evolution.

  12. Holographic lens for optical correlator

    NASA Astrophysics Data System (ADS)

    Semenov, G. B.; Koreshev, S. N.; Pavlov, A. V.; Shubnikov, Y. I.

    1984-08-01

    Aberrations in holographic optics place limitations on the information capacity of the data that can be processed by holographic optical correlators. Nonetheless, the aberrations can be reduced sufficiently for an extensive class of devices such as those for real time data input using space-time light modulators and a TV channel. This paper analyzes the aberrations of holographic lenses, demonstrating the feasibility of an off-axis lens for correlation image analysis with aberrations similar to an axial lens. A requirement that the wave aberrations not exceed a quarter-wavelength was placed on the lens. Equations are solved for coma and astigmatism, and used to plot the maximum wave aberrations as a function of the spatial frequency of the proposed signal for three cases: (1) normal propagation of a diverging beam and oblique propagation of a plane beam; (2) oblique propagation of diverging and parallel beams, symmetrical with respect to the normal to the photographic plate; (3) oblique propagation of the diverging beam and normal propagation of the parallel beam. The angle between the beam axes was 45 deg in all cases, with a lens focal length of 350 mm and an operture of 32 mm.

  13. Development of Software Correlator for KJJVC

    NASA Astrophysics Data System (ADS)

    Yeom, J. H.; Oh, S. J.; Roh, D. G.; Kang, Y. W.; Park, S. Y.; Lee, C. H.; Chung, H. S.

    2009-12-01

    Korea-Japan Joint VLBI Correlator (KJJVC) is being developed by collaborating KASI (Korea Astronomy and Space Science Institute), Korea, and NAOJ(National Observatory of Japan), Japan. In early 2010, KJJVC will work in normal operation. In this study, we developed the software correlator which is based on VCS (VLBI Correlation Subsystem) hardware specification as the core component of KJJVC. The main specification of software correlator is 8 Gbps, 8192 output channels, and 262,144-points FFT (Fast Fourier Transform) function same as VCS. And the functional algorithm which is same as specification of VCS and arithmetic register are adopted in this software correlator. To verify the performance of developed software correlator, the correlation experiments were carried out using the spectral line and continuum sources which were observed by VERA (VLBI Exploration of Radio Astrometry), NAOJ. And the experimental results were compared to the output of Mitaka FX correlator by referring spectrum shape, phase rate, and fringe detection and so on. Through the experimental results, we confirmed that the correlation results of software correlator are the same as Mitaka FX correlator and verified the effectiveness of it. In future, we expect that the developed software correlator will be the possible software correlator of KVN (Korean VLBI Network) with KJJVC by introducing the correlation post-processing and modifying the user interface as like GUI (Graphic User Interface).

  14. A Two Factor ANOVA-like Test for Correlated Correlations: CORANOVA

    ERIC Educational Resources Information Center

    Bilker, Warren B.; Brensinger, Colleen; Gur, Ruben C.

    2004-01-01

    Testing homogeneity of correlations with Fisher's Z is inappropriate when correlations are themselves correlated. Suppose measurements of brain activation and performance are taken before and during a verbal memory task. Of interest are changes in activity gradients in specific regions, R1, R2, R3, and performance, V. The "correlated correlations"…

  15. The Effect of Error Correlation on Interfactor Correlation in Psychometric Measurement

    ERIC Educational Resources Information Center

    Westfall, Peter H.; Henning, Kevin S. S.; Howell, Roy D.

    2012-01-01

    This article shows how interfactor correlation is affected by error correlations. Theoretical and practical justifications for error correlations are given, and a new equivalence class of models is presented to explain the relationship between interfactor correlation and error correlations. The class allows simple, parsimonious modeling of error…

  16. Physiological correlates of mental workload

    NASA Technical Reports Server (NTRS)

    Zacharias, G. L.

    1980-01-01

    A literature review was conducted to assess the basis of and techniques for physiological assessment of mental workload. The study findings reviewed had shortcomings involving one or more of the following basic problems: (1) physiologic arousal can be easily driven by nonworkload factors, confounding any proposed metric; (2) the profound absence of underlying physiologic models has promulgated a multiplicity of seemingly arbitrary signal processing techniques; (3) the unspecified multidimensional nature of physiological "state" has given rise to a broad spectrum of competing noncommensurate metrics; and (4) the lack of an adequate definition of workload compels physiologic correlations to suffer either from the vagueness of implicit workload measures or from the variance of explicit subjective assessments. Using specific studies as examples, two basic signal processing/data reduction techniques in current use, time and ensemble averaging are discussed.

  17. Correlation effects in metallic cohesion

    NASA Astrophysics Data System (ADS)

    Haydock, Roger

    2014-03-01

    The electronic contribution to the cohesive energy of a correlated metal is the sum of the transition energies for adding successive electrons at successive Fermi levels until the system reaches its final electron density. This can be computed as the integral of energy over the projected density of transitions for adding single electrons to localized orbitals. In the case of independent electrons, this reduces to the usual integral over the projected density of states. As an example, cohesive energies for some simple transition metal structures are calculated using the recursion method* with a Hubbard repulsion between electrons. * Phys. Rev. B 61, 7953-64 Work supported by the Richmond F. Snyder gift to the University of Oregon.

  18. Neural correlates of face detection.

    PubMed

    Xu, Xiaokun; Biederman, Irving

    2014-06-01

    Although face detection likely played an essential adaptive role in our evolutionary past and in contemporary social interactions, there have been few rigorous studies investigating its neural correlates. MJH, a prosopagnosic with bilateral lesions to the ventral temporal-occipital cortices encompassing the posterior face areas (fusiform and occipital face areas), expresses no subjective difficulty in face detection, suggesting that these posterior face areas do not mediate face detection exclusively. Despite his normal contrast sensitivity and visual acuity in foveal vision, the present study nevertheless revealed significant face detection deficits in MJH. Compared with controls, MJH showed a lower tolerance to noise in the phase spectrum for faces (vs. cars), reflected in his higher detection threshold for faces. MJH's lesions in bilateral occipito-temporal cortices thus appear to have produced a deficit not only in face individuation, but also in face detection. PMID:23365211

  19. Correlation functions in stochastic inflation

    NASA Astrophysics Data System (ADS)

    Vennin, Vincent; Starobinsky, Alexei A.

    2015-09-01

    Combining the stochastic and formalisms, we derive non-perturbative analytical expressions for all correlation functions of scalar perturbations in single-field, slow-roll inflation. The standard, classical formulas are recovered as saddle-point limits of the full results. This yields a classicality criterion that shows that stochastic effects are small only if the potential is sub-Planckian and not too flat. The saddle-point approximation also provides an expansion scheme for calculating stochastic corrections to observable quantities perturbatively in this regime. In the opposite regime, we show that a strong suppression in the power spectrum is generically obtained, and we comment on the physical implications of this effect.

  20. Correlation method of electrocardiogram analysis

    NASA Astrophysics Data System (ADS)

    Strinadko, Marina M.; Timochko, Katerina B.

    2002-02-01

    The electrocardiograph method is the informational source for functional heart state characteristics. The electrocardiogram parameters are the integrated map of many component characteristics of the heart system and depend on disturbance requirements of each device. In the research work the attempt of making the skeleton diagram of perturbation of the heart system is made by the characteristic description of its basic components and connections between them through transition functions, which are written down by the differential equations of the first and second order with the purpose to build-up and analyze electrocardiogram. Noting the vector character of perturbation and the various position of heart in each organism, we offer own coordinate system connected with heart. The comparative analysis of electrocardiogram was conducted with the usage of correlation method.

  1. Correlating thalamocortical connectivity and activity

    NASA Astrophysics Data System (ADS)

    da Fontoura Costa, Luciano; Sporns, Olaf

    2006-07-01

    The segregated regions of the mammalian cerebral cortex and thalamus form an extensive and complex network, whose structure and function are still only incompletely understood. The present letter describes an application of the concepts of complex networks and random walks that allows the identification of nonrandom, highly structured features of thalamocortical connections and their potential effects on dynamic interactions between cortical areas in the cat brain. Utilizing large-scale anatomical data sets of this thalamocortical system, we investigate uniform random walks in such a network by considering the steady state eigenvector of the respective stochastic matrix. It is shown that thalamocortical connections are organized in such a way as to guarantee strong correlation between the outdegree and occupancy rate (a stochastic measure potentially related to activation) of each cortical area. Possible organizational principles underlying this effect are identified and discussed.

  2. Investigation of correlation classification techniques

    NASA Technical Reports Server (NTRS)

    Haskell, R. E.

    1975-01-01

    A two-step classification algorithm for processing multispectral scanner data was developed and tested. The first step is a single pass clustering algorithm that assigns each pixel, based on its spectral signature, to a particular cluster. The output of that step is a cluster tape in which a single integer is associated with each pixel. The cluster tape is used as the input to the second step, where ground truth information is used to classify each cluster using an iterative method of potentials. Once the clusters have been assigned to classes the cluster tape is read pixel-by-pixel and an output tape is produced in which each pixel is assigned to its proper class. In addition to the digital classification programs, a method of using correlation clustering to process multispectral scanner data in real time by means of an interactive color video display is also described.

  3. Vibration analysis using digital correlation

    NASA Technical Reports Server (NTRS)

    Gilbert, John A.; Lehner, David L.; Dudderar, T. Dixon; Matthys, Donald R.

    1988-01-01

    This paper demonstrates the use of a computer-based optical method for locating the positions of nodes and antinodes in vibrating members. Structured light patterns are projected at an angle onto the vibrating surface using a 35 mm slide projector. The vibrating surface and the projected images are captured in a time averaged photograph which is subsequently digitized. The inherent fringe patterns are filtered to determine amplitudes of vibration, and computer programs are used to compare the time averaged images to images recorded prior to excitation to locate nodes and antinodes. Some of the influences of pattern regularity on digital correlation are demonstrated, and a speckle-based method for determining the mode shapes and the amplitudes of vibration with variable sensitivity is suggested.

  4. CORRELATIONS IN CONFINED QUANTUM PLASMAS

    SciTech Connect

    DUFTY J W

    2012-01-11

    This is the final report for the project 'Correlations in Confined Quantum Plasmas', NSF-DOE Partnership Grant DE FG02 07ER54946, 8/1/2007 - 7/30/2010. The research was performed in collaboration with a group at Christian Albrechts University (CAU), Kiel, Germany. That collaboration, almost 15 years old, was formalized during the past four years under this NSF-DOE Partnership Grant to support graduate students at the two institutions and to facilitate frequent exchange visits. The research was focused on exploring the frontiers of charged particle physics evolving from new experimental access to unusual states associated with confinement. Particular attention was paid to combined effects of quantum mechanics and confinement. A suite of analytical and numerical tools tailored to the specific inquiry has been developed and employed

  5. Multiagency VLBI Correlator Facility opens

    NASA Astrophysics Data System (ADS)

    Carter, William E.

    A new $1.2 million facility to process geodetic Very Long Baseline Interferometry (VLBI) observational data was dedicated August 25, 1986, at the U.S. Naval Observatory headquarters, Washington, D.C., by representatives of the National Oceanic and Atmospheric Administration (NOAA), the Naval Research Laboratory (NRL), the U.S. Naval Observatory (USNO), and the National Aeronautics and Space Administration (NASA). The new facility will provide timely correlation of the data tapes produced by the POLARIS (Polar (Motion) Analysis by Radio Interferometric Surveying) earth orientation monitoring network. The new facility will also be used to process VLBI data collected by the NASA Crustal Dynamics Project (CDP) and by NRL and USNO programs in astrometry and basic research.

  6. Correlated randomness and switching phenomena

    NASA Astrophysics Data System (ADS)

    Stanley, H. E.; Buldyrev, S. V.; Franzese, G.; Havlin, S.; Mallamace, F.; Kumar, P.; Plerou, V.; Preis, T.

    2010-08-01

    One challenge of biology, medicine, and economics is that the systems treated by these serious scientific disciplines have no perfect metronome in time and no perfect spatial architecture-crystalline or otherwise. Nonetheless, as if by magic, out of nothing but randomness one finds remarkably fine-tuned processes in time and remarkably fine-tuned structures in space. Further, many of these processes and structures have the remarkable feature of “switching” from one behavior to another as if by magic. The past century has, philosophically, been concerned with placing aside the human tendency to see the universe as a fine-tuned machine. Here we will address the challenge of uncovering how, through randomness (albeit, as we shall see, strongly correlated randomness), one can arrive at some of the many spatial and temporal patterns in biology, medicine, and economics and even begin to characterize the switching phenomena that enables a system to pass from one state to another. Inspired by principles developed by A. Nihat Berker and scores of other statistical physicists in recent years, we discuss some applications of correlated randomness to understand switching phenomena in various fields. Specifically, we present evidence from experiments and from computer simulations supporting the hypothesis that water’s anomalies are related to a switching point (which is not unlike the “tipping point” immortalized by Malcolm Gladwell), and that the bubbles in economic phenomena that occur on all scales are not “outliers” (another Gladwell immortalization). Though more speculative, we support the idea of disease as arising from some kind of yet-to-be-understood complex switching phenomenon, by discussing data on selected examples, including heart disease and Alzheimer disease.

  7. 2004 Photon Correlation and Scattering Conference

    NASA Technical Reports Server (NTRS)

    Meyer, William (Editor); Smart, Anthony (Editor); Wegdam, Gerard (Editor); Dogariu, Aristide (Editor); Carpenter, Bradley (Editor)

    2004-01-01

    The Photon Correlation and Scattering (PCS) meeting welcomes all who are interested in the art and science of photon correlation and its application to optical scattering. The meeting is intended to enhance interactions between theory, applications, instrument design, and participants.

  8. Arousal and Anxiety Correlates of Gymnastic Performance

    ERIC Educational Resources Information Center

    Basler, Marilyn L.; And Others

    1976-01-01

    Tests on a women's gymnastic team to explore correlation between arousal, anxiety, and performance, revealed limited relationships between performance and arousal/anxiety measures and indicated that gymnastic ability is the best correlate of gymnastic performance. (JD)

  9. Postulates for measures of genuine multipartite correlations

    SciTech Connect

    Bennett, Charles H.; Grudka, Andrzej; Horodecki, Michal; Horodecki, Ryszard; Horodecki, Pawel

    2011-01-15

    A lot of research has been done on multipartite correlations, but the problem of satisfactorily defining genuine multipartite correlations--those not trivially reducible to lower partite correlations--remains unsolved. In this paper we propose three reasonable postulates which each measure or indicator of genuine multipartite correlations (or genuine multipartite entanglement) should satisfy. We also introduce the concept of degree of correlations, which gives partial characterization of multipartite correlations. Then, we show that covariance does not satisfy two postulates and hence it cannot be used as an indicator of genuine multipartite correlations. Finally, we propose a candidate for a measure of genuine multipartite correlations based on the work that can be drawn from a local heat bath by means of a multipartite state.

  10. Structural dynamics analyses testing and correlation

    NASA Technical Reports Server (NTRS)

    Caughey, T. K.

    1982-01-01

    Some aspects of the lack of close correlation between the predictions of analytical modeling of dynamic structures and the results of vibration tests on such structures are examined. Ways in which the correlation may be improved are suggested.

  11. Quantum Correlations, Chaos and Information

    NASA Astrophysics Data System (ADS)

    Madhok, Vaibhav

    Quantum chaos is the study of quantum systems whose classical description is chaotic. How does chaos manifest itself in the quantum world? In this spirit, we study the dynamical generation of entanglement as a signature of chaos in a system of periodically kicked coupled-tops, where chaos and entanglement arise from the same physical mechanism. The long-time entanglement as a function of the position of an initially localized wave packet very closely correlates with the classical phase space surface of section - it is nearly uniform in the chaotic sea, and reproduces the detailed structure of the regular islands. The uniform value in the chaotic sea is explained by the random state conjecture. As classically chaotic dynamics take localized distributions in phase space to random distributions, quantized versions take localized coherent states to pseudo-random states in Hilbert space. Such random states are highly entangled, with an average value near that of the maximally entangled state. For a map with global chaos, we derive that value based on new analytic results for the entropy of random states. For a mixed phase space, we use the Percival conjecture to identify a "chaotic subspace" of the Hilbert space. The typical entanglement, averaged over the unitarily invariant Haar measure in this subspace, agrees with the long-time averaged entanglement for initial states in the chaotic sea. In all cases the dynamically generated entanglement is that of a random complex vector, even though the system is time-reversal invariant, and the Floquet operator is a member of the circular orthogonal ensemble. Continuing on our journey to find the footprints of chaos in the quantum world, we explore quantum signatures of classical chaos by studying the rate of information gain in quantum tomography. The measurement record is obtained as a sequence of expectation values of a Hermitian operator evolving under repeated application of the Floquet operator of the quantum kicked top on

  12. Wind-Tunnel/Flight Correlation, 1981

    NASA Technical Reports Server (NTRS)

    Mckinney, L. W. (Editor); Baals, D. D. (Editor)

    1982-01-01

    Wind-tunnel/flight correlation activities are reviewed to assure maximum effectiveness of the early experimental programs of the National Transonic Facility (NTF). Topics included a status report of the NTF, the role of tunnel-to-tunnel correlation, a review of past flight correlation research and the resulting data base, the correlation potential of future flight vehicles, and an assessment of the role of computational fluid dynamics.

  13. Survey of current correlators and applications

    NASA Technical Reports Server (NTRS)

    Lahmeyer, C. R.; Brokl, S. S.

    1987-01-01

    With this summary an attempt is made to contact as many users as possible so as to provide summary data on correlation systems, both in use and as planned. Data on currently available very large scale integration (VLSI) chips and complete systems are included. Also, several planned correlator systems are described and summarized in tabular form. Finally, a description is given of the work being done in the Communications Systems Research Section on VLSI correlator chips and complete correlator systems.

  14. Prototype Optical Correlator For Robotic Vision System

    NASA Technical Reports Server (NTRS)

    Scholl, Marija S.

    1993-01-01

    Known and unknown images fed in electronically at high speed. Optical correlator and associated electronic circuitry developed for vision system of robotic vehicle. System recognizes features of landscape by optical correlation between input image of scene viewed by video camera on robot and stored reference image. Optical configuration is Vander Lugt correlator, in which Fourier transform of scene formed in coherent light and spatially modulated by hologram of reference image to obtain correlation.

  15. Wavelet correlations in the [ital p] model

    SciTech Connect

    Greiner, M. Institut fuer Theoretische Physik, Justus Liebig Universitaet, 35392 Geien ); Lipa, P.; Carruthers, P. )

    1995-03-01

    We suggest applying the concept of wavelet transforms to the study of correlations in multiparticle physics. Both the usual correlation functions as well as the wavelet transformed ones are calculated for the [ital p] model, which is a simple but tractable random cascade model. For this model, the wavelet transform decouples correlations between fluctuations defined on different scales. The advantageous properties of factorial moments are also shared by properly defined factorial wavelet correlations.

  16. Functional Multiple-Set Canonical Correlation Analysis

    ERIC Educational Resources Information Center

    Hwang, Heungsun; Jung, Kwanghee; Takane, Yoshio; Woodward, Todd S.

    2012-01-01

    We propose functional multiple-set canonical correlation analysis for exploring associations among multiple sets of functions. The proposed method includes functional canonical correlation analysis as a special case when only two sets of functions are considered. As in classical multiple-set canonical correlation analysis, computationally, the…

  17. Problems with the Method of Correlated Vectors

    ERIC Educational Resources Information Center

    Ashton, M.C.; Lee, K.

    2005-01-01

    The method of correlated vectors has been used widely to identify variables that are associated with general intelligence (g). Briefly, this method involves finding the correlation between the vector of intelligence subtests' g-loadings and the vector of those subtests' correlations with the variable in question. We describe two major problems…

  18. Economic and Educational Correlates of TIMSS Results

    ERIC Educational Resources Information Center

    Mikk, Jaan

    2005-01-01

    The good knowledge of the correlates of educational achievement highlights the ways to the efficient use of economic and human capital in raising the efficiency of education. The present paper investigates the correlates and compares the values of the correlates for the Republic of Lithuania with the average international values. The data for the…

  19. Structural Correlates of Prospective Memory

    PubMed Central

    Gordon, Brian A; Shelton, Jill T; Bugg, Julie M; McDaniel, Mark A; Head, Denise

    2011-01-01

    Prospective memory (PM) includes the encoding and maintenance of an intention, and the retrieval and execution of this intention at the proper moment in the future. The present study expands upon previous behavioral, electrophysiological, and functional work by examining the association between grey matter volume and PM. Estimates of grey matter volume in theoretically relevant regions of interest (prefrontal, parietal, and medial temporal) were obtained in conjunction with performance on two PM tasks in a sample of 39 cognitively normal and very mildly demented older adults. The first PM task, termed focal in the literature, is supported by spontaneous retrieval of the PM intention whereas the second, termed non-focal, relies on strategic monitoring processes for successful intention retrieval. A positive relationship was observed between medial temporal volume and accuracy on the focal PM task. An examination of medial temporal lobe subregions revealed that this relationship was strongest for the hippocampus, which is considered to support spontaneous memory retrieval. There were no significant structure-behavior associations for the non-focal PM task. These novel results confirm a relationship between behavior and underlying brain structure proposed by the multiprocess theory of PM, and extend findings on cognitive correlates of medial temporal lobe integrity. PMID:21982698

  20. Magnetoencephalographic correlates of audiotactile interaction.

    PubMed

    Lütkenhöner, B; Lammertmann, C; Simões, C; Hari, R

    2002-03-01

    To seek for correlates of an interaction between auditory and somatosensory processing, the brain's magnetic field in response to simultaneously presented auditory (A) and tactile (T) stimuli was compared with the sum of the respective unimodal responses (A+T). The stimuli were binaural 1047-Hz tone bursts of 60 dB sensation level and tactile pressure pulses to the right thumb. The mean interval between two stimuli of the same modality was 1.95 s. The magnetic field was recorded using a 306-channel whole-scalp neuromagnetometer. A clear audiotactile interaction was revealed in the hemisphere contralateral to the side of tactile stimulation in six of eight subjects, whereas in the ipsilateral hemisphere an interaction was noticed in only three subjects. The time courses of these audiotactile interaction fields typically showed major deflections of opposite polarities around 140 and 220 ms. The first deflection appeared to arise in the region of the secondary somatosensory cortex (SII). The polarity of this interaction was consistent with the view that the auditory stimulus resulted in a partial inhibition in SII. In two subjects, strong indications of auditory contributions to the interaction were available, although in different hemispheres. The relatively high interindividual variability of the observed interaction, which represents potential neural substrates for multisensory integration, could indicate that the way subjects perceive the simultaneous presentation of auditory and tactile stimuli differs. PMID:11848694