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Correlation Spectra (correlation + spectrum)
Selected AbstractsStructural information from quadrupolar nuclei in solid state NMRCONCEPTS IN MAGNETIC RESONANCE, Issue 3 2006Sharon E. Ashbrook Abstract Solid-state NMR has become the method of choice for determining details of molecular-level structure in heterogeneous systems. Though spin-1/2 nuclei still form the core of most such studies, quadrupolar nuclei are increasingly being used. This review assesses what is currently possible, from achieving high-resolution spectra for quadrupolar nuclei (a prerequisite for most structure determination work), to forming correlation spectra which give qualitative details of spatial proximity of nuclei and the determination of internuclear distances, between quadrupolar spins and quadrupolar and spin-1/2 nuclei. Examples are given of each method discussed, and the advantages and disadvantages of the various experiments for different possible applications are assessed. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 183,248, 2006. [source] Semiautomatic sequence-specific assignment of proteins based on the tertiary structure,The program st2nmrJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2002Primo, Pristov Abstract The sequence-specific assignment of resonances is still the most time-consuming procedure that is necessary as the first step in high-resolution NMR studies of proteins. In many cases a reliable three-dimensional (3D) structure of the protein is available, for example, from X-ray spectroscopy or homology modeling. Here we introduce the st2nmr program that uses the 3D structure and Nuclear Overhauser Effect spectroscopy (NOESY) peak list(s) to evaluate and optimize trial sequence-specific assignments of spin systems derived from correlation spectra to residues of the protein. A distance-dependent target function that scores trial assignments based on the presence of expected NOESY crosspeaks is optimized in a Monte Carlo fashion. The performance of the program st2nmr is tested on real NMR data of an ,-helical (cytochrome c) and ,-sheet (lipocalin) protein using homology models and/or X-ray structures; it succeeded in completely reproducing the correct sequence-specific assignments in most cases using 2D and/or 15N/13C Nuclear Overhauser Effect (NOE) data. Additionally to amino acid residues the program can also handle ligands that are bound to the protein, such as heme, and can be used as a complementary tool to fully automated assignment procedures. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 335,340, 2002 [source] Indirect detection of the 183W and 57Fe nuclei using 119Sn-relayed 1H,X correlation spectroscopyMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2010T. Andrew Mobley Abstract Recently reported triple-resonance Y-relayed 1H,X correlation experiments have been utilized to characterize 183W and 57Fe chemical shifts using 119Sn as the Y-relaying nucleus instead of the previously used 31P. Application of an adaptation of Gudat's original INEPT/HMQC sequence results in a significant enhancement of the signal-to-noise (S/N) ratio for two-dimensional 119Sn-relayed 1H,183W and 1H, 57Fe correlation spectra with efficient detection of the transition metal nucleus in tungsten and iron complexes lacking an observable direct scalar coupling between the transition metal and any hydrogen nuclei. Strengths and shortcomings of the novel sequence and the original sequences reported by Gudat are discussed in the context of 119Sn-relayed proton detection of very low frequency transition metal nuclei. Copyright © 2010 John Wiley & Sons, Ltd. [source] Environmentally friendly flame retardants.MAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2007A detailed solid-state NMR study of melamine orthophosphate Abstract We used solid-state NMR spectroscopy to gain detailed information about the proton positions, proximities and the hydrogen-bonding network in the environmentally friendly flame retardant melamine orthophosphate (MP). High-resolution proton one- and two-dimensional solid-state NMR spectra were obtained at high external magnetic field in combination with fast magic angle spinning of the sample. Furthermore, we recorded homo- and heteronuclear correlation spectra of types 15N15N, 1H13C, 1H15N and 1H31P. In addition, we determined the geometry of the NH and NH2 groups in MP by 15N1H heteronuclear recoupling experiments. We were able to completely assign the different isotropic chemical shifts in MP. Furthermore, we could identify the protonation of the melamine and orthophosphate moieties. The experimental results are discussed in connection with the structural model obtained by powder X-ray diffraction together with a combined molecular modeling-Rietveld refinement approach (De Ridder et al. Helv. Chim. Acta 2004; 87: 1894). We show that the geometry of the NH2 groups can only be successfully estimated by solid-state NMR. Copyright © 2007 John Wiley & Sons, Ltd. [source] Fast multidimensional NMR by polarization sharingMAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2007Eriks Kup Abstract The speed of multidimensional NMR spectroscopy can be significantly increased by drastically shortening the customary relaxation delay between scans. The consequent loss of longitudinal magnetization can be retrieved if ,new' polarization is transferred from nearby spins. For correlation spectroscopy involving heteronuclei (X = 13C or 15N), protons not directly bound to X can repeatedly transfer polarization to the directly bound protons through Hartmann,Hahn mixing. An order of magnitude increase in speed has been observed for the 600 MHz two-dimensional HMQC spectra of amikacin and strychnine using this technique, and it also reduces the noisy F1 ridges that degrade many heteronuclear correlation spectra recorded with short recovery times. Copyright © 2007 John Wiley & Sons, Ltd. [source] Multinuclear NMR study of some organoplatinum complexes containing multifunctional azines as chelating ligands,MAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2004Dietrich Gudat Abstract 1H-detected indirect NMR techniques were used to determine 15N and 195Pt NMR parameters for a series of organoplatinum(IV) complexes and one platinum(II) complex containing nitrogen-based azobispyridine, bispyridyltetrazine, and bipyrimidine ligands. The inverse technique permitted the detection of small 4J(Pt,H) and 5J(Pt,H) long-range couplings and the acquisition of 15N NMR data in natural isotopic abundance via nJ(N,H) intra- and inter-ligand couplings, but failed in cases where coherence transfer is quenched by rapid relaxation of the metal atom. In one case, analysis of satellite patterns in a set of 1H,15N, 1H,195Pt and 1H,13C correlation spectra allowed a positive sign to be determined for 1J(Pt,15N). Qualitative arguments are presented to explain the observed 15N coordination shifts in complexes with different azine ligands in terms of azine,M dative bond formation and LnM,azine back-donation. Copyright © 2004 John Wiley & Sons, Ltd. [source] Temperature dependence and resonance assignment of 13C NMR spectra of selectively and uniformly labeled fusion peptides associated with membranesMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2004Michele L. Bodner Abstract HIV-1 and influenza viral fusion peptides are biologically relevant model fusion systems and, in this study, their membrane-associated structures were probed by solid-state NMR 13C chemical shift measurements. The influenza peptide IFP-L2CF3N contained a 13C carbonyl label at Leu-2 and a 15N label at Phe-3 while the HIV-1 peptide HFP-UF8L9G10 was uniformly 13C and 15N labeled at Phe-8, Leu-9 and Gly-10. The membrane composition of the IFP-L2CF3N sample was POPC,POPG (4:1) and the membrane composition of the HFP-UF8L9G10 sample was a mixture of lipids and cholesterol which approximately reflects the lipid headgroup and cholesterol composition of host cells of the HIV-1 virus. In one-dimensional magic angle spinning spectra, labeled backbone 13C were selectively observed using a REDOR filter of the 13C,15N dipolar coupling. Backbone chemical shifts were very similar at ,50 and 20°C, which suggests that low temperature does not appreciably change the peptide structure. Relative to ,50°C, the 20°C spectra had narrower signals with lower integrated intensity, which is consistent with greater motion at the higher temperature. The Leu-2 chemical shift in the IFP-L2CF3N sample correlates with a helical structure at this residue and is consistent with detection of helical structure by other biophysical techniques. Two-dimensional 13C,13C correlation spectra were obtained for the HFP-UF8L9G10 sample and were used to assign the chemical shifts of all of the 13C labels in the peptide. Secondary shift analysis was consistent with a ,-strand structure over these three residues. The high signal-to-noise ratio of the 2D spectra suggests that membrane-associated fusion peptides with longer sequences of labeled amino acids can also be assigned with 2D and 3D methods. Copyright © 2004 John Wiley & Sons, Ltd. [source] A new technique for differentiating between 2J(C,H) and 3/4J(C,H) connectivitiesMAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2003Thomas Sprang Abstract We present a new pulse sequence that yields two simultaneously detected types of long-range correlation spectra. The one spectrum is to show all nJ(C,H) connectivities and the other is to show exclusively 2J(C,H) connectivities. The method is demonstrated by using strychnine as a test sample. A comparison with HMBC shows that the 2J(C,H)/nJ(C,H) experiment supplies a nJ(C,H) spectrum that is of equal standard with regard to sensitivity and spectral information. The additional 2J(C,H) spectrum allows the disentanglement of 2J(C,H) and nJ(C,H) signals (n > 2) in HMBC type spectra, which greatly simplifies signal assignment and structure elucidation in general. Copyright © 2003 John Wiley & Sons, Ltd. [source] Bacterial IscU is a well folded and functional single domain proteinFEBS JOURNAL, Issue 11 2004Salvatore Adinolfi Iron,sulfur clusters are widely represented in most organisms, but the mechanism of their formation is not fully understood. Of the two main proteins involved in cluster formation, NifS/IscS and NifU/IscU, only the former has been well studied from a structural point of view. Here we report an extensive structural characterization of Escherichia coli IscU. We show by a variety of physico-chemical techniques that E. coli IscU construct can be expressed to high purity as a monomeric protein, characterized by an ,, fold with high ,-helix content. The high melting temperature and the reversibility of the thermal unfolding curve (as measured by CD spectroscopy) hint at a well ordered stable fold. The excellent dispersion of cross peaks in the 1H- 15N correlation spectrum is consistent with these observations. Monomeric E. coli IscU is able to provide a scaffold for Iron,sulfur cluster assembly, but has no direct interaction with either Fe(II) or Fe(III) ions, suggesting the need of further partners to achieve a stable interaction. [source] Chemical shift assignment of the transmembrane helices of DsbB, a 20-kDa integral membrane enzyme, by 3D magic-angle spinning NMR spectroscopyPROTEIN SCIENCE, Issue 2 2008Ying Li Abstract The Escherichia coli inner membrane enzyme DsbB catalyzes disulfide bond formation in periplasmic proteins, by transferring electrons to ubiquinone from DsbA, which in turn directly oxidizes cysteines in substrate proteins. We have previously shown that DsbB can be prepared in a state that gives highly resolved magic-angle spinning (MAS) NMR spectra. Here we report sequential 13C and 15N chemical shift assignments for the majority of the residues in the transmembrane helices, achieved by three-dimensional (3D) correlation experiments on a uniformly 13C, 15N-labeled sample at 750-MHz 1H frequency. We also present a four-dimensional (4D) correlation spectrum, which confirms assignments in some highly congested regions of the 3D spectra. Overall, our results show the potential to assign larger membrane proteins using 3D and 4D correlation experiments and form the basis of further structural and dynamical studies of DsbB by MAS NMR. [source] | ||||||||||