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1.
Suzumura K Takagi Y Orita M Taira K 《Journal of the American Chemical Society》2004,126(47):15504-15511
In the identification of a metal-binding site within enzymes, kinetic analyses based on thio-effects and Cd(2+)-rescues are widely used. In those analyses, kinetic studies using a phosphorothioate have been discussed on the premise that the substitution by a sulfur atom does not change the conformation of a ribozyme. However, our present NMR structural analysis demonstrates the change of the conformation at the metal-binding site by Rp-sulfur but not by Sp-sulfur substitution and warns against incautious interpretations of thio-effects and rescue phenomena in kinetic studies using a phosphorothioate. Our analysis further demonstrates that, in solution, a Cd(2+) ion can interact with an Rp-phosphorothioate (in support of the controversial McKay's structure, Nature 1994, 372, 68-74) and with an Sp-phosphorothioate (in support of the controversial Scott's structure, Cell 1995, 81, 991-1002) at the metal-binding A9/G10.1 site and that, in the former case, the bound Cd(2+) ion can return the ribozyme to an active conformation and rescue its enzymatic activity. 相似文献
2.
Tanaka Y Kojima C Morita EH Kasai Y Yamasaki K Ono A Kainosho M Taira K 《Journal of the American Chemical Society》2002,124(17):4595-4601
An RNA oligomer, r(GGACGAGUCC), which mimics the metal ion-binding motif of hammerhead ribozymes, was shown to fold by itself into a conformation possessing a metal ion binding property which is similar to that of the intact ribozyme (Tanaka, et al. J. Am. Chem. Soc. 2000, 122, 11303-11310). To determine the metal ion-binding site of this motif at an atomic level, we synthesized a series of RNA oligomers which were selectively labeled with a (15)N-labeled guanosine at each of the four guanosine residues. The (15)N-chemical shift perturbation with Cd(II) ions by one-dimensional (1D) (15)N NMR spectra showed that the chemical shift of the N7 of the G7 residue, N7/G7, in the metal ion-binding motif was specifically perturbed. This is the first experimental evidence to prove that the N7/G7 binds with a Cd(II) ion. 相似文献
3.
M. A. M. Khouna M. T. Ben Dhia M. R. Khaddar 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1673-1682
The two octahedral complexes SnCl4·2(O)PF(NR2)2 (R = Me or Et) were prepared from reaction of SnCl4 with the ligand (R2N)2P(O)F in anhydrous CHCl3. The new adducts have been characterized by elemental analysis, IR, and multinuclear (119Sn, 31P, 19F, and 1H) NMR spectroscopy. The NMR data show that the adducts exist in solution as a mixture of cis and trans isomers with markedly different proportions. When compared with previously described hexamethylphosphoramide (HMPA) and trimethylphosphate (TMPA) analogues, our results indicate that the cis isomer is the predominant species in solution. Low temperature 31P and 119Sn NMR spectra show that the compounds partially dissociate in dichloromethane. 相似文献
4.
The reaction of [(THF)Li(Ph(2)PC(H)Py)] with ZnCl(2) in the presence of ZnO yields the zinc complex [Zn(3)(Ph(2)PC(H)Py)(4)O] (1). Deprotonation of the phosphane Ph(2)P(CH(2)Py) with [Fe(N(SiMe(3))(2))2] gives the iron complexes [(Ph(2)P(CH(2)Py))Fe(Ph(2)PC(H)Py)2] (2) and [Fe(Ph(2)PC(H)Py)(N(SiMe(3))(2))]2 (3), depending on the ratio of phosphane. The solid state structures of the metal complexes illustrate the coordination flexibility of the [Ph(2)C(H)Py](-)-anion. Depending on the electronic requirements of the coordinated metal the anion acts as a (P,N)-chelating amide or C-coordinating carbanion with the P- and N-heteroatoms as donor bases. 相似文献
5.
Vogt M Lahiri S Hoogstraten CG Britt RD DeRose VJ 《Journal of the American Chemical Society》2006,128(51):16764-16770
Although site-bound Mg2+ ions have been proposed to influence RNA structure and function, establishing the molecular properties of such sites has been challenging due largely to the unique electrostatic properties of the RNA biopolymer. We have previously determined that, in solution, the hammerhead ribozyme (a self-cleaving RNA) has a high-affinity metal ion binding site characterized by a K(d,app) < 10 microM for Mn2+ in 1 M NaCl and speculated that this site has functional importance in the ribozyme cleavage reaction. Here we determine both the precise location and the hydration level of Mn2+ in this site using ESEEM (electron spin-echo envelope modulation) spectroscopy. Definitive assignment of the high-affinity site to the activity-sensitive A9/G10.1 region is achieved by site-specific labeling of G10.1 with 15N guanine. The coordinated metal ion retains four water ligands as measured by 2H ESEEM spectroscopy. The results presented here show that a functionally important, specific metal binding site is uniquely populated in the hammerhead ribozyme even in a background of high ionic strength. Although it has a relatively high thermodynamic affinity, this ion remains partially hydrated and is chelated to the RNA by just two ligands. 相似文献
6.
Ion exchange distribution of the phenylphosphoric acid has been studied on various types of chloride form strong base resins as a function of pH at 25 °C, at 0.1 M ionic strength. Equilibrium measurements were supplemented by the study of pH dependence of the 31P NMR spectra of the resin-phase phenylphosphate species. Equations were derived to describe the pH dependence of the overall distribution coefficient and the chemical shift of the resin-phase solute species. Experimental data were evaluated by using these model equations and the values of the individual distribution coefficients, ion exchange selectivity coefficients and the resin-phase 31P chemical shifts of the mono- and divalent ions have been calculated. Comparison of distribution data of the individual species corroborated the significance of the role of hydrophobic interaction in the selectivity of organic ion exchange processes. A well-defined correlation between the ion exchange selectivity and the resin-phase 31P NMR chemical shift data has been pointed out. 相似文献
7.
Alice J. Boyall Keith B. Dillon Philippa K. Monks Jennifer C. Potts 《Heteroatom Chemistry》2007,18(6):609-612
The di‐ium dication formed by triflic acid protonation of the cyclic triphosphenium ion derived from 1,4‐bis‐diphenylphosphinobutane, (dppb), and P3(X = Br or Cl) decomposes via an acyclic dication bearing a PHX group; this intermediate is reduced by SnX2 in the presence of HX to yield a dication with a PH2 primary phosphane terminal group, which is comparatively stable. The structure of this species has been unequivocally confirmed by 31P solution‐state NMR spectroscopy. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:609–612, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20302 相似文献
8.
Du J Yao S Seitz WR Bencivenga NE Massing JO Planalp RP Jackson RK Kennedy DP Burdette SC 《The Analyst》2011,136(23):5006-5011
The fluorescence emission of poly(N-isopropylacrylamide) (PNIPAM) covalently tagged with a 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) fluorophore and an iminodiacetic acid (IDA) chelator changes with temperature and with Cu(II) complexation. Increasing the temperature above the lower critical solution temperature (LCST) causes the polymer to collapse from a coil to a compact globule. This changes the environment experienced by the fluorophore causing a shift in maximum emission wavelength from 546 to 508 nm and an increase in the ratio of emission intensity at 508 nm to emission intensity at 546 nm from 0.70 to almost 1.40. Metal ions can be sensed by working at a temperature where the uncomplexed polymer is in an expanded state due to the charges on the ligand. Complexation with a metal ion such as Cu(II) neutralizes the charges on the ligand causing the polymer to collapse. At 35 °C, the emission intensity maximum shifted from 535 to 510 nm as Cu(II) concentration was increased and the intensity ratio increased from 0.84 to 1.28. By decoupling complexation from fluorescence, we have prepared a ratiometric fluorescent indicator for a metal ion that normally quenches fluorescence. The affinity for Cu(II) was found to be thermally tunable. The log apparent formation constants for the indicator-Cu(II) complex were estimated as the half way point in the intensity ratio vs. pCu curve. The values were determined to be 4.3 at 35 °C and 3.2 at 34 °C respectively. 相似文献
9.
A.-R. Grimmer D. Müller G. Gözel R. Kniep 《Analytical and bioanalytical chemistry》1997,357(5):485-488
11B and 31P MAS NMR spectroscopy of three borophosphates was used to monitor their phase composition via the isotropic chemical shifts.
CaBPO5 and BPO4 represent nearly pure samples, SrBPO5 contains β-Sr2P2O7 as well as BPO4 as impurities. The anisotropic chemical shift data provide additional information on the geometry and connectivity of the
BO4 and PO4 building units.
Received: 25 July 1996 / Revised: 19 August 1996 / Accepted: 23 August 1996 相似文献
10.
A.-R. Grimmer D. Müller G. G?zel R. Kniep 《Fresenius' Journal of Analytical Chemistry》1997,357(5):485-488
11B and 31P MAS NMR spectroscopy of three borophosphates was used to monitor their phase composition via the isotropic chemical shifts.
CaBPO5 and BPO4 represent nearly pure samples, SrBPO5 contains β-Sr2P2O7 as well as BPO4 as impurities. The anisotropic chemical shift data provide additional information on the geometry and connectivity of the
BO4 and PO4 building units.
Received: 25 July 1996 / Revised: 19 August 1996 / Accepted: 23 August 1996 相似文献
11.
《Magnetic resonance in chemistry : MRC》2018,56(4):276-284
Multinuclear solid‐state NMR and powder X‐ray diffraction data collected for phosphonate materials Zr(O3PC6H4PO3) · 3.6H2O and Sn(O3PC6H4PO3)0.85(O3POH)0.30 · 3.09H2O have resulted in the layered structure, where the phosphonic acids cross‐link the layers. The main structural motif (the 111 connectivity in the PO3 group) has been established by determination of chemical shift anisotropy parameters for phosphorus nuclei in the phosphonate groups. An analysis of the variable‐temperature 31P T1 measurements and the shapes of the phosphorus resonances in the 31P static NMR spectra have resulted in the dipolar mechanism of the phosphorus spin‐lattice relaxation, where the rotating phenylene rings reorient dipolar vectors P…H as a driving force of the relaxation process. It has been found that water protons do not affect the 31P T1 times. The activation energy of the phenylene rotation in both compounds has been determined as low as 12.5 kJ/mol. The interpretation of the phosphorus relaxation data has been independently confirmed by the measurements of 1H T1 times for protons of the phenylene rings. 相似文献
12.
I. P. Kovalev Yu. A. Strelenko A. V. Ignatenko M. G. Vinogradov G. I. Nikishin 《Russian Chemical Bulletin》1989,38(5):937-940
1. | According to1H and31P NMR spectra, the cationic complexes [Rh(PMe3)4]X (X=Cl, BPh4) exist in solution (H2O, MeOH, MeCN) as fluxional five-coordinate species [Rh(PMe3)4. (solvent)]X. |
2. | The synthesized complexes [Rh(PMe3)4O2]Cl and [Rh(PMe3)4O2]BPh4 have trigonal bipyramidal structure in solution according to31P and1H NMR spectroscopy. |
13.
Vladimir I. Bakhmutov Aida Contreras-Ramirez Hannah Drake Hong-Cai Zhou 《Magnetic resonance in chemistry : MRC》2023,61(1):16-21
The phosphorus chemical shift anisotropies, 31PΔcs, and asymmetry parameters η were measured by the 31P{1H} NMR experiments in static and low-frequency spinning samples of the zirconium phosphates and phosphonates and also in the mixed Zr (IV)/Sn (IV) phosphate/phosphonate material. The data obtained have shown a 111 connectivity in the HPO4 and PO3 groups, which does not change at modification and intercalation of the materials. The 31PΔcs values of the phosphonate groups (43–49 ppm) significantly surpass the values characterizing the HPO4 groups (23–37 ppm). The 31P Δcs values obtained for the metal (IV) phosphates were discussed in terms of P-O distances. The 31P chemical shift anisotropy parameters can help at elucidation of local structures in phosphate and phosphonate materials. 相似文献
14.
By introducing the flexible 1,1'-(1,4-butanediyl)bis(imidazole) (bbi) ligand into the polyoxovanadate system, five novel polyoxoanion-templated architectures based on [As(8)V(14)O(42)](4-) and [V(16)O(38)Cl](6-) building blocks were obtained: [M(bbi)(2)](2)[As(8)V(14)O(42)(H(2)O)] [M = Co (1), Ni (2), and Zn (3)], [Cu(bbi)](4)[As(8)V(14)O(42)(H(2)O)] (4), and [Cu(bbi)](6)[V(16)O(38)Cl] (5). Compounds 1-3 are isostructural, and they exhibit a binodal (4,6)-connected 2D structure with Schl?fli symbol (3(4) x 4(2))(3(4) x 4(4) x 5(4) x 6(3))(2), in which the polyoxoanion induces a closed four-membered circuit of M(4)(bbi)(4). Compound 4 exhibits an interesting 3D framework constructed from tetradentate [As(8)V(14)O(42)](4-) cluster anions and cationic ladderlike double chains. There exists a bigger M(8)(bbi)(6)O(2) circuit in 4. The 3D extended structure of 5 is composed of heptadentate [V(16)O(38)Cl](6-) anions and flexural cationic chains; the latter consists of six Cu(bbi) segments arranged alternately. It presents the largest 24-membered circuit of M(24)(bbi)(24) so far observed made of bbi molecules and transition-metal cations. Investigation of their structural relations shows the important template role of the polyoxoanions and the synergetic interactions among the polyoxoanions, transition-metal ions, and flexible ligand in the assembly process. The magnetic properties of compounds 1-3 were also studied. 相似文献
15.
Pepi F Ricci A Rosi M Di Stefano M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(10):2787-2797
Systematic experimental and theoretical studies on anionic phosphate species in the gas phase are almost nonexistent, even though they could provide a benchmark for enhanced comprehension of their liquid-phase chemical behavior. Gaseous MH(2)P(2)O(7) (-) ions (M=Li, Na, K, Rb, Cs), obtained from electrospray ionization of solutions containing H(4)P(2)O(7) and MOH or M salts as a source of M(+) ions were structurally assayed by collisionally activated dissociation (CAD) mass spectrometry and theoretical calculations at the B3LYP/6-31+G* level of theory. The joint application of mass spectrometric techniques and theoretical methods allowed the MH(2)P(2)O(7) (-) ions to be identified as having a structure in which the linear diphosphate anion is coordinated to the M(+) ion (I) and provides information on gas-phase isomerization processes in the [PO(3)...MH(2)PO(4)](-) clusters II and the [P(2)O(6)...M...H(2)O](-) clusters IV. Studies of gas-phase reactivity by Fourier transform ion cyclotron resonance (FTICR) and triple quadrupole (TQ) mass spectrometry revealed that the MH(2)P(2)O(7) (-) ions react with selected nucleophiles by clustering, proton transfer and addition-elimination mechanisms. The influence of the coordination of alkali metal ions on the chemical behavior of pyrophosphate is discussed. 相似文献
16.
Martínez-Viviente E Pregosin PS Vial L Herse C Lacour J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(12):2912-2918
1H, (19)F and (31)P pulsed field gradient spin-echo (PGSE) diffusion studies on chiral organic salts that contain hexacoordinate phosphate anions, namely tris(tetrachlorobenzenediolato)phosphate(V) (TRISPHAT) and bis(tetrachlorobenzenediolato)mono([1,1']binaphthalenyl-2,2'diolato)-phosphate(V) (BINPHAT), are reported. The first example of the dependence of a diffusion value on diastereomeric structure is presented. Marked solvent and concentration effects on the diffusion constants (D) of these salts are noted and the question of ion pairing is discussed. 相似文献
17.
Summary Pyindine-4-aldoxime reacts with the aquopentacyanoferrate(II) ion by forming a complex compound of 1:1 molar ratio. ThepK
a
value of the oxime group in the complex, the influence ofpH changes on its formation as well as IR data indicate the coordination of pyridine-4-aldoxime through the pyridine nitrogen.
Das Pentacyanopyridin-4-aldoximferrat(II)-Ion. Bestimmung der Koordinationsstelle
Zusammenfassung Pyridin-4-aldoxim reagiert mit dem Aquopentacyanoferrat(II)-Ion und bildet einen Komplex mit dem Molarverhältnis 1:1. DerpK a Wert der Oxim-Gruppe im Komplex, der Einfluß despH auf seine Bildung, wie auch die IR Daten weisen auf die Koordination des Pyridin-4-aldoxim über den Pyridin-Stickstoff hin.相似文献
18.
Talebpour Z Ghassempour A Zendehzaban M Bijanzadeh HR Mirjalili MH 《Analytica chimica acta》2006,576(2):290-296
Trichlorfon is an organophosphorus insecticide, which is extensively being used for protection of fruit crops. Trichlorfon is a thermal labile compound, which cannot be easily determined by gas chromatography (GC) and has no suitable group for sensitive detection by high performance liquid chromatography (HPLC). In this study, a 31P nuclear magnetic resonance (31P NMR) has been described for monitoring of trichlorfon without any separation step. The quantitative works of 31P NMR spectroscopy has been performed in the presence of an internal standard (hexamethylphosphoramide). Limit of detection (LOD) for this method has been found to be 55 mg L−1, without any sample preparation, and the linear working range was 150-5500 mg L−1. Relative standard deviation (R.S.D.%) of the method for three replicates within and between days was obtained ≤9%. The average recovery efficiency was approximately 99-112%. This method was applied for monitoring trichlorfon in a commercial insecticide sample and tomato sample. 相似文献
19.
Tanaka Y Kasai Y Mochizuki S Wakisaka A Morita EH Kojima C Toyozawa A Kondo Y Taki M Takagi Y Inoue A Yamasaki K Taira K 《Journal of the American Chemical Society》2004,126(3):744-752
We have studied the interaction between metal ions and the metal ion-binding motif in hammerhead ribozymes, as well as the functions of the metal ion at the motif, with heteronuclear NMR spectroscopy. In this study, we employed model RNA systems which mimic the metal ion-binding motif and the altered motif. In Co(NH3)6(III) titrations, we observed large 1H and 31P chemical shift perturbations for the motif and found that outer-sphere complexation of Co(NH3)6(III) is possible for this motif. From the reinvestigation of our previous 15N chemical shift data for Cd(II) binding, in comparison with those of organometallic compounds, we conclude that Cd(II) can form an inner-sphere complex with the nucleobase in the motif. Therefore, the A9/G10.1 site was found to accept both inner-sphere and outer-sphere complexations. The Mg(II) titration for a slightly different motif from the A9/G10.1 site (G10.1-C11.1 to A10.1-U11.1) revealed that its affinity to Mg(II) was drastically reduced, although the ribozyme with this altered motif is known to retain enzymatic activities. This observation suggests that the metal ion at these motifs is not a catalytic center of hammerhead ribozymes. 相似文献