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1.
The accurate measurement of small spin–spin coupling constants in macromolecules dissolved in a liquid crystalline phase is important in the context of molecular structure investigation by modern liquid state NMR. A new spin-state-selection filter, DIPSAP, is presented with significantly reduced sensitivity to J-mismatch of the filter delays compared to previously proposed pulse sequences. DIPSAP presents an attractive new approach for the accurate measurement of small spin–spin coupling constants in molecules dissolved in anisotropic solution. Application to the measurement of 15N–13C′ and 1HN–13C′ coupling constants in the peptide planes of 13C, 15N labeled proteins demonstrates the high accuracy obtained by a DIPSAP-based experiment. 相似文献
2.
Thomas Szyperski Csar Fernndez Akira Ono Kurt Wüthrich Masatsune Kainosho 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,140(2):491
A two-dimensional {31P} spin-echo-difference constant-time [13C, 1H]-HMQC experiment (2D {31P}-sedct-[13C, 1H]-HMQC) is introduced for measurements of 3JC4′P and 3JH3′P scalar couplings in large 13C-labeled nucleic acids and in DNA–protein complexes. This experiment makes use of the fact that 1H–13C multiple-quantum coherences in macromolecules relax more slowly than the corresponding 13C single-quantum coherences. 3JC4′P and 3JH3′P are related via Karplus-type functions with the phosphodiester torsion angles β and ε, respectively, and their experimental assessment therefore contributes to further improved quality of NMR solution structures. Data are presented for a uniformly 13C, 15N-labeled 14-base-pair DNA duplex, both free in solution and in a 17-kDa protein–DNA complex. 相似文献
3.
Katalin E. Kvr Gyula Batta 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,170(2):341
Since the introduction of RDCs in high-resolution NMR studies of macromolecules, there is a growing interest in the development of accurate, and sensitive methods for determining coupling constants. Most methods for extracting these couplings are based on the measurement of the splitting between multiplet components in J-coupled spectra. However, these methods are often unreliable since undesired multiple-bond couplings can considerably broaden the multiplet components and consequently make accurate determination of their position difficult. To demonstrate one approach to this problem, G-BIRD(r) decoupled TROSY sequences are proposed for the measurement of 1JNH and 1JNC′ coupling constants. Resolved or unresolved splittings due to remote protons are removed by a G-BIRD(r) module employed during t1 and as a result, spectra with narrow, well-resolved peaks are obtained from which heteronuclear one-bond couplings can be accurately measured. Moreover, introduction of a spin-state-selective α/β-filter in the TROSY sequence allows the separation of the 1JNC′ doublet components into two subspectra which contain the same number of peaks as the regular TROSY spectrum. The 1JNC′ couplings are obtained from the displacement between the corresponding peaks in the subspectra. 相似文献
4.
Siegel R Trébosc J Amoureux JP Gan Z 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,193(2):321-325
Nitrogen-14 (spin I = 1) has always been a nucleus difficult to observe in solid-state NMR and until recently its observation was restricted to one-dimensional (1D) spectra. We present here the first 3D 1H–13C–14N NMR correlation spectrum. This spectrum was acquired on a test sample l-histidine·HCl·H2O using a recently developed technique, which consists in indirectly observing 14N nuclei via dipolar recoupling with an HMQC-type experiment. 相似文献
5.
A recently proposed 13C–1H recoupling sequence operative under fast magic-angle spinning (MAS) [K. Takegoshi, T. Terao, Solid State Nucl. Magn. Reson. 13 (1999) 203–212.] is applied to observe 13C–1H and 15N–1H dipolar powder patterns in the 1H–15N–13C–1H system of a peptide bond. Both patterns are correlated by 15N-to-13C cross polarization to observe one- or two-dimensional (1D or 2D) correlation spectra, which can be simulated by using a simple analytical expression to determine the H–N–C–H dihedral angle. The 1D and 2D experiments were applied to N-acetyl[1,2-13C,15N]
-valine, and the peptide φ angle was determined with high precision by the 2D experiment to be ±155.0°±1.2°. The positive one is in good agreement with the X-ray value of 154°±5°. The 1D experiment provided the value of φ=±156.0°±0.8°. 相似文献
6.
Florence Cordier Marco Rogowski Stephan Grzesiek Ad Bax 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,140(2):510
It is demonstrated that J connectivity between amide protons and hydrogen-bond-accepting carbonyl carbons can be observed in perdeuterated human ubiquitin. A selective pulse scheme is used to detect these small 2hJHC′ interactions in the presence of the much larger through-covalent-bond 2JHC′ and 3JHC′ couplings. The ratio of the observed through-H-bond correlation intensity and the 2JHC′ connectivity observed in a reference spectrum indicates 2hJHC′ values of ca. 0.4–0.6 Hz, which are only slightly smaller than the corresponding 3hJNC′ values. However, for technical reasons, 2hJHC′ couplings are more difficult to measure than 3hJNC′. 相似文献
7.
Yizhou Liu James H. Prestegard 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(1):109-118
Residual dipolar couplings (RDCs) between NC′ and NCα atoms in polypeptide backbones of proteins contain information on the orientation of bond vectors that is complementary to that contained in NH RDCs. The 1JNCα and 2JNCα scalar couplings between these atoms also display a Karplus relation with the backbone torsion angles and report on secondary structure. However, these N–C couplings tend to be small and they are frequently unresolvable in frequency domain spectra having the broad lines characteristic of large proteins. Here a TROSY-based J-modulated approach for the measurement of small 15N–13C couplings in large proteins is described. The cross-correlation interference effects inherent in TROSY methods improve resolution and signal to noise ratios for large proteins, and the use of J-modulation to encode couplings eliminates the need to remove frequency distortions from overlapping peaks during data analysis. The utility of the method is demonstrated by measurement of 1JNC′, 1JNCα, and 2JNCα scalar couplings and 1DNC′ and 1DNCα residual dipolar couplings for the myristoylated yeast ARF1·GTPγs protein bound to small lipid bicelles, a system with an effective molecule weight of 70 kDa. 相似文献
8.
Perttu Permi Ilkka Kilpelinen Arto Annila 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,146(2):255
Transverse relaxation-optimized NMR experiment (TROSY) for the measurement of three-bond scalar coupling constant between 1Hαi−1 and 15Ni defining the dihedral angle ψ is described. The triple-spin-state-selective experiment allows measurement of 3JHαN from 13Cα, 15N, and 1HN correlation spectra H2O with minimum resonance overlap. Transverse relaxation of 13Cα spin is minimized by using spin-state-selective filtering and by acquiring a signal longer in 15N-dimension in a manner of semi-constant-time TROSY evolution. The 3JHαN values obtained with the proposed α/β-HN(CO)CA-J TROSY scheme are in good agreement with the values measured earlier from ubiquitin in D2O using the HCACO[N] experiment. 相似文献
9.
H Watanabe Y Ishihara K Okamoto K Oshio T Kanamatsu Y Tsukada 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,134(2):214-222
The 3D localized13C spectroscopy methods LINEPT and LODEPT, which are modifications of INEPT and DEPT, are proposed. As long as a13C inversion pulse (180-degree pulse) is applied at 1/(4J) before the proton echo time in LINEPT and a13C excitation pulse (90-degree pulse) is applied at 1/(2J) before the proton echo time in LODEPT, the proton echo time can be set to any value longer than 1/(2J) in LINEPT and longer than 1/Jin LODEPT. As a result, the proton and the13C pulses can be applied separately and these proton pulses can be made slice-selective pulses. These localization features of LINEPT and LODEPT were evaluated using a phantom consisting of a cylinder filled with ethanol placed inside another cylinder filled with oil, and localized ethanol spectra could be obtained.In vivo3D localized13C spectra from the brain of a monkey could be obtained using decoupled LINEPT, and glutamate C-4 appeared directly after the administration of glucose C-1, followed by the appearance of glutamate C-2, C-3 and glutamine C-2, C-3, C-4. 相似文献
10.
Y.-Y. Hu K. Schmidt-Rohr 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,197(2):193-207
In experiments on S–L heteronuclear spin systems with evolution of the S-spin magnetization under the influence of a quadrupolar nucleus (L-spin), effects of longitudinal quadrupolar (T1Q) relaxation of the L-spin coherence on the sub-millisecond time scale have been documented and explored, and methods for minimizing their effect have been demonstrated. The longitudinal relaxation results in heteronuclear dephasing even in the reference signal S0 of S{L} REDOR, REAPDOR, RIDER, or SPIDER experiments, due to T1Q-relaxation of the transiently generated SyLz coherence, reducing or even eliminating the observable dephasing ΔS. Pulse sequences for measuring an improved reference signal S00 with minimal heteronuclear recoupling but the same number of pulses as for S0 and S have been demonstrated. From the observed intensity ΔS0 = S00 − S0 and the SPIDER signal ΔS/S0, T1Q can be estimated. Accelerated decays analogous to the dipolar S0 curves will occur in T2 measurements for J-coupled S–L spin pairs. Even in the absence of recoupling pulses, fast T1Q relaxation of the unobserved nucleus shortens the transverse relaxation time T2S,MAS of the observed nucleus, in particular at low spinning frequencies, due to unavoidable heteronuclear dipolar evolution during a rotation period. The observed spinning-frequency dependence of T2S,MAS matches the theoretical prediction and may be used to estimate T1Q. The effects are demonstrated on several 13C{14N} spin systems, including an arginine derivative, the natural N-acetylated polysaccharide chitin, and a model peptide, (POG)10. 相似文献
11.
Xianzhong Yan Xiangming Kong Youlin Xia Kong Hung Sze Guang Zhu 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,147(2):357
Recent developments in the direct observation of J couplings across hydrogen bonds in proteins and nucleic acids provide additional information for structure and function studies of these molecules by NMR spectroscopy. A JNN-correlated [15N, 1H] TROSY experiment proposed by Pervushin et al. (Proc. Natl. Acad. Sci. USA 95, 14147–14151, 1998) can be applied to measure hJHN in smaller nucleic acids in an E.COSY manner. However, it cannot be effectively applied to large nucleic acids, such as tRNATrp, since one of the peaks corresponding to a fast relaxing component will be too weak to be observed in the spectra of large molecules. In this Communication, we proposed a modified JNN-correlated [15N, 1H] TROSY experiment which enables direct measurement of hJHN in large nucleic acids. 相似文献
12.
Ekaterina Leonova Jekabs Grins Mohammadreza Shariatgorji Leopold L. Ilag Mattias Edn 《Solid state nuclear magnetic resonance》2009,36(1):11-18
We compare 29Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra from the two modifications of silicon nitride, α-Si3N4 and β-Si3N4, with that of a fully (29Si, 15N)-enriched sample 29Si315N4, as well as 15N NMR spectra of Si315N4 (having 29Si at natural abundance) and 29Si315N4. We show that the 15N NMR peak-widths from the latter are dominated by J(29Si–15N) through-bond interactions, leading to significantly broader NMR signals compared to those of Si315N4. By fitting calculated 29Si NMR spectra to experimental ones, we obtained an estimated coupling constant J(29Si–15N) of 20 Hz. We provide 29Si spin-lattice (T1) relaxation data for the 29Si315N4 sample and chemical shift anisotropy results for the 29Si site of β-Si3N4. Various factors potentially contributing to the 29Si and 15N NMR peak-widths of the various silicon nitride specimens are discussed. We also provide powder X-ray diffraction (XRD) and mass spectrometry data of the samples. 相似文献
13.
Tran Nghia Pham Tibor Liptaj Krystyna Bromek Du
an Uhrín 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,157(2):200
Two 2D J-modulated HSQC-based experiments were designed for precise determination of small residual dipolar one-bond carbon–proton coupling constants in 13C natural abundance carbohydrates. Crucial to the precision of a few hundredths of Hz achieved by these methods was the use of long modulation intervals and BIRD pulses, which acted as semiselective inversion pulses. The BIRD pulses eliminated effective evolution of all but 1JCH couplings, resulting in signal modulation that can be described by simple modulation functions. A thorough analysis of such modulation functions for a typical four-spin carbohydrate spin system was performed for both experiments. The results showed that the evolution of the 1H–1H and long-range 1H–13C couplings during the BIRD pulses did not necessitate the introduction of more complicated modulation functions. The effects of pulse imperfections were also inspected. While weakly coupled spin systems can be analyzed by simple fitting of cross peak intensities, in strongly coupled spin systems the evolution of the density matrix needs to be considered in order to analyse data accurately. However, if strong coupling effects are modest the errors in coupling constants determined by the “weak coupling” analysis are of similar magnitudes in oriented and isotropic samples and are partially cancelled during dipolar coupling calculation. Simple criteria have been established as to when the strong coupling treatment needs to be invoked. 相似文献
14.
J. Emery Y. Laligant J. Y. Buzar L. Smiri F. Hlel T. Ben-Chaabane 《Solid state nuclear magnetic resonance》2000,16(4)
To understand the surprising behavior between the variations of the P′–P–P″ angles and the correlated variations of the O′–P–O″ ones, two lithium cyclohexaphosphate compounds Li6P6O18·3H2O and Li6P6O18 are studied by solid state nuclear magnetic resonance (NMR) spectroscopy. The two compounds exhibit the same [P6O18]6− ring anions but with 3m or
internal symmetry, respectively. Such symmetries induce local distortions that are exhibited by NMR spectroscopy. One-dimensional (1D) NMR gives information on structural sites of 7Li and 31P ions and the crystallographic non-equivalencies are observed. Nevertheless, in the anhydrous compound, X-ray diffraction and NMR results do not completely agree and some discrepancy exists between the number of sites observed with the first technique and the number of lines exhibited in the NMR spectra either for 7Li or 31P nuclei. This problem is elucidated by using 2D double quantum NMR spectroscopy coupled with theoretical considerations. We find that the 31P chemical shift tensor is dependent on the deviations of the O–P–O angles from those in the regular tetrahedron. Within the same empirical model, we suggest that the surprising behavior between the variations of the P′–P–P″ and the ones of the O′–P–O″ is related to the overall charge on the PO4 group. We also find the positions of the isotropic lines for 7Li essentially depend on the site co-ordination of this nuclei. 相似文献
15.
Gary A. Lorigan Ronald McNamara Roger A. Jones Stanley J. Opella 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,140(2):315
The magnitudes and orientations of the 15N chemical shift tensor of [1-15N]-2′-deoxyguanosine were determined from a polycrystalline sample using the two-dimensional PISEMA experiment. The magnitudes of the principal values of the 15N chemical shift tensor of the N1 nitrogen of [1-15N]-2′-deoxyguanosine were found to be ς11 = 54 ppm, ς22 = 148 ppm, and ς33 = 201 ppm with respect to (15NH4)2SO4 in aqueous solution. Comparisons of experimental and simulated two-dimensional powder pattern spectra show that ς33N is approximately collinear with the N–H bond. The tensor orientation of ς33N for N1 of [1-15N]-2′-deoxyguanosine is similar to the values obtained for the side chain residues of 15Nε1-tryptophan and 15Nπ-histidine even though the magnitudes differ significantly. 相似文献
16.
Brian J. Drouin Shanshan Yu John C. Pearson Holger S.P. Müller 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(18):2077-2081
Extensions in frequency coverage coupled with sensitive spectroscopic techniques have enabled high resolution measurements of pure rotational spectra of deuteromethane and its 13-C substituted counterpart up to J′=7. The current work reveals a small inconsistency in previously reported frequency measurements of 12CH3D at J′=5. 相似文献
17.
18.
Bidisha Bose-Basu Jaroslav Zajicek Gail Bondo Shikai Zhao Meredith Kubsch Ian Carmichael Anthony S. Serianni 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,144(2):207
13C and 2H spin–lattice relaxation times have been determined by inversion recovery in a range of site-specific 13C- and 2H-labeled saccharides under identical solution conditions, and the data were used to calculate deuterium nuclear quadrupolar coupling constants (2H NQCC) at specific sites within cyclic and acyclic forms in solution. 13C T1 values ranged from 0.6 to 8.2 s, and 2H T1 values ranged from 79 to 450 ms, depending on molecular structure (0.4 M sugar in 5 mM EDTA (disodium salt) in 2H2O-depleted H2O, pH 4.8, 30°C). In addition to providing new information on 13C and 2H relaxation behavior of saccharides in solution, the resulting 2H1 NQCC values reveal a dependency on anomeric configuration within aldopyranose rings, whereas 2H NQCC values at other ring sites appear less sensitive to configuration at C1. In contrast, 2H NQCC values at both anomeric and nonanomeric sites within aldofuranose rings appear to be influenced by anomeric configuration. These experimental observations were confirmed by density functional theory (DFT) calculations of 2H NQCC values in model aldopyranosyl and aldofuranosyl rings. 相似文献
19.
The effects of cubic crystal fields on the saturation magnetic moment of Sm3+ ion in ferromagnetic compounds have been investigated. In samarium compounds with magnetic elements, the exchange fieldH
ex acting on Sm3+ ion is taken to be proportional to the sublattice magnetization of the magnetic element, while in compounds with nonmagnetic
elementsH
ex is taken to be proportional to the spin average of the Sm3+ ion and is determined self-consistently. In both types of compoundsH
ex is assumed to be along [001] direction. The saturation magnetic moment is calculated by taking into account the admixture
of excited (J=7/2 andJ=9/2) levels into the ground (J=5/2) level of Sm3+ ion by crystal fields and exchange fields. It is shown that depending upon the strength, the crystal fields quench or enhance
the magnetic moment from the free ion value, and in some cases force Sm3+ ion to behave effectively like an (L+S) ion rather than an (L−S)ion. The crystal fields may have important bearing on the performance of samarium compounds as permanent magnet materials. 相似文献
20.
Jürgen M. Schmidt 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,124(2):298-309
High-precision heteronuclear three-bond coupling constants including3J(HN, C′),3J(HN, Cβ),3J(Hα,Cγ), and3J(Hβ, C′) are determined for the nonproline residues in uniformly13C-enrichedantamanide,cyclo-(-Val1-Pro2-Pro3-Ala4-Phe5-Phe6-Pro7-Pro8-Phe9- Phe10-), using quantitative numerical 2D NMR spectrum evaluation based on the product-operator formalism. The experimental basis comprises two-dimensional1H,13C-heteronuclear relayed E.COSY spectra [J. M. Schmidt, R. R. Ernst, S. Aimoto, and M. Kainosho,J. Biomol. NMR6,95 (1995)], the multiplet patterns of which are subjected to iterative least-squares 2D multiplet-simulation procedures. Accuracy and precision of the spectrum fit are assessed byFstatistics and analysis of variances (ANOVA) leading to confidence intervals for the optimized spin-system parameters. The long-range J coupling constants obtained and their standard deviations provide the experimental foundation for a later detailed analysis of φ and χ1dihedral-angle equilibrium conformations contributing to the flexible peptide structure. 相似文献