Efficiency of 1H --> 31P NMR cross-polarization in bone apatite and its mineral standards

Human bone mineral was studied using solid-state ³¹P NMR with cross-polarization (CP) from protons. The CP efficiency was determined for trabecular and cortical bone tissue from human adults and compared with synthetic mineral standards. The study shows the similarity between carbonatoapatite of type B and bone mineral as shown by their CP behaviour. The method can be used for the characterization of synthetic apatite-based implant materials.     

1D and 2D solid state NMR investigations of the framework structure of As-synthesized AlPO4-14

The framework structure of As-synthesized A1PO₄-14 has been investigated with a combination of different one-dimensional ²⁷Al and ³¹P solid state NMR techniques and ²⁷Al/³¹P double resonance methods. The results are found to be fully consistent with the assumed structural model. ²⁷Al MAS and DOR experiments at three different magnetic field strengths together with simulations show the presence of two tetrahedral sites, one pentacoordinated and one octahedral aluminum site. The ²⁷Al quadrupolar coupling constants and the ³¹P isotropic chemical shifts of the tetrahedral sites correlate well with tetrahedral shear-strain parameters and mean P-O-A1 bond angles, respectively. These correlations allow one to assign all of the NMR resonances to specific T-sites in the proposed framework structure. The assignments are then further confirmed by the application of three different two-dimensional heteronuclear correlation methods (i.e., ²⁷Al → ³¹P TEDOR, CP, and INEPT) which reveal the connectivities between AlO_x and PO₄ polyhedra. The two-dimensional INEPT experiment is applied here for the first time in the solid state.     

Alzheimer''s disease histologically proven studied by MRI and MRS: Two cases

Two patients affected by severe Alzheimer's disease (AD) were investigated by MRI and image-guided ³¹P MRS. In one case, ¹H MRS was additionally performed. In both cases the diagnosis of AD was confirmed, post mortem, by the pathologist. The spectral parameters of the ³¹P MR spectra were estimated by fitting the ³¹P MR signals in the time domain. Our ³¹P MRS results suggest that it is possible to detect the membrane catabolism, as indexed with the level of PDE resonances visible in in vivo ³¹P MRS, at least in severe AD cases. The ¹H spectrum from AD brain showed a marked decrease of NAA signal respect to choline.     

Studies of silicophosphate derivatives by 31P-->29Si CP MAS NMR

We show that it is possible to efficiently transfer magnetization from ³¹P to ²⁹Si, using variable amplitude CP MAS experiment. This experiment is demonstrated by using Si₅O(PO₄)₆, the synthesis protocol of which is described. From the obtained results, we show that the experiment allows the spectral edition of ²⁹Si spectra from ³¹P→²⁹Si CP, enabling the studies of derivatives involving Si–O–P linkages, such as phosphosilicate glasses, microporous silicoaluminophosphates (SAPO) and bioactive phosphosilicates.     

In vivo 31P MRS of human brain at high/ultrahigh fields: a quantitative comparison of NMR detection sensitivity and spectral resolution between 4 T and 7 T

The primary goal of this study was to establish a rigorous approach for determining and comparing the NMR detection sensitivity of in vivo ³¹P MRS at different field strengths (B₀). This was done by calculating the signal-to-noise ratio (SNR) achieved within a unit sampling time at a given field strength. In vivo ³¹P spectra of human occipital lobe were acquired at 4 and 7 T under similar experimental conditions. They were used to measure the improvement of the human brain ³¹P MRS when the field strength increases from 4 to 7 T. The relaxation times and line widths of the phosphocreatine (PCr) resonance peak and the RF coil quality factors (Q) were also measured at these two field strengths. Their relative contributions to SNR at a given field strength were analyzed and discussed. The results show that in vivo ³¹P sensitivity was significantly improved at 7 T as compared with 4 T. Moreover, the line-width of the PCr resonance peak showed less than a linear increase with increased B₀, which leads to a significant improvement in ³¹P spectral resolution. These findings indicate the advantage of high-field strength to improve in vivo ³¹P MRS quality in both sensitivity and spectral resolution. This advantage should improve the reliability and applicability of in vivo ³¹P MRS in studying high-energy phosphate metabolism, phospholipid metabolism and cerebral biogenetics in the human at both normal and diseased states noninvasively. Finally, the approach used in this study for calculating in vivo ³¹P MRS sensitivity provides a general tool in estimating the relative NMR detection sensitivity for any nuclear spin at a given field strength.     

高场磁共振成像1H/31P双调谐射频线圈研究进展

在众多可产生磁共振现象的原子核中,¹H核凭借其在生物体中含量高、磁共振信号强的优势,成为磁共振成像的主要研究对象．但其它杂核在生命科学相关研究中同样具有不可替代的独特性,如³¹P核广泛参与了生物体内的能量代谢过程,是非质子成像研究领域的重要内容．MRI向更高场强的发展使得杂核成像逐渐普及,其核心部件是高质量的¹H/³¹P双调谐射频线圈．本文总结了与¹H/³¹P双调谐射频线圈相关的研究与应用,展示了9.4 T下小鼠脑的质子磁共振成像及磁共振磷谱,并讨论了高场¹H/³¹P双调谐射频线圈的潜在应用价值．     

S-烷基-O-(邻烷氧基羰基苯基)-硫(赶)代磷酰胺的NMR研究

本工作记录了六种通式为H₂N RS P=O-O-COOR'(R=Me,Et,i-Pr,n-Pr;R'=Me,Et,i-Pr)的有机磷农药的¹H、¹³C、³¹P NMR谱及¹³C,¹H异核化学位移相关谱。确定了各¹H、¹³C、³¹P的化学位移值和¹H-¹H、³¹P-¹H、³¹P-¹³C的偶合常数。讨论了核磁参数与分子结构和运动以及³¹P化学位移与生物活性之间的关系。     

Spin-lattice relaxation times and nuclear overhauser enhancement effect for P metabolites in model solutions at two frequencies: Implications for in vivo spectroscopy

The relaxation time T₁ values and nuclear Overhauser enhancement factor for ³¹P signal were determined in model solutions of metabolites ATP, PCr and Pi, and AMP at two frequencies and in H₂O and ²H₂O solutions. The data were analyzed to resolve the contribution of different relaxation mechanisms. A knowledge of NOE is important in the light of recent applications of double resonance methods to enhance the sensitivity of in vivo ³¹P spectroscopy. The results show that chemical shift anisotropy is the dominant mechanism for ³¹P in ATP at the high field, whereas the dipolar interaction mechanism is the main feature for the ³¹P relaxation of PCr and Pi. The dipolar mechanism responsible for NOE originates from interactions of solvent water with ³¹P moiety. Implications for in vivo spectroscopy are indicated.     

Si CP/MAS NMR of phosphorus-bearing organosilicon compounds

While liquid-state ²⁹Si NMR of phosphorus-bearing organosilicon compounds with more than one phosphorus per molecule can take advantage of the presence of J-coupling ⁿJ(³¹P²⁹Si) for purposes of structural assignment from J-coupling patterns, conventional ²⁹Si CP/MAS spectra of such molecular solids do not reveal structural details in a straightforward manner. For such compounds it is necessary to obtain ²⁹Si CP/MAS spectra under conditions of simultaneous ¹H- and ³¹P-high power decoupling in order to derive reliable ²⁹Si chemical shift information. ²⁹Si CP/MAS NMR spectra, obtained with and without ³¹P high power decoupling during the acquisition time, of several organosilicon compounds containing Si_xP_y (x = 1 −10, y = 1 −10) moieties are reported.     

人淋巴瘤白血病细胞系Molt-4的31P核磁共振研究

用³¹P核磁共振(NMR)观察了人淋巴瘤白血病细胞系Molt-4的³¹P谱.NMR测试温度为37℃、20℃和4℃时,随着测试时间增长,细胞³¹P谱中ATP峰降低,无机磷峰升高,细胞³¹P谱的变化随测试温度降低依次减缓.实验温度为4℃,从收集细胞至开始NMR累加在30min内,NMR累加在60min内,获得活细胞的稳定的³¹P谱.根据细胞内无机磷的化学位移数值,对细胞内pH值进行了测定.     

Concentration and temperature dependence of diluent dynamics studied by line shape experiments on a phosphate ester in polycarbonate

³¹P Hahn spin echo line shape and proton line shape experiments are reported on bisphenol A polycarbonate (BPAPC)-tris(2-ethylhexyl)phosphate (TOP) systems to study the concentration and temperature dependence of the local dynamics. In an earlier ³¹P line shape study a lattice model was presented as a framework to interpret the plasticization and antiplasticization behavior of the diluent based on a fractional population given by the type of nearest neighbor contacts in the mixed polymer-diluent glass. In this study, ³¹P spin echo line shapes of BPAPC, with 5%, 10% and 15% TOP, which monitor the diluent dynamics, at different temperatures and echo delay times are simulated in terms of fast- and slow-moving components, and the resulting fractional populations are compared with that predicted by the lattice model. Comparisons with the lattice model calculations are also made in the simulation of the ¹H line shapes on BPAPC with 5% and 10% TOP, which probes both the polymer and diluent dynamics, and on BPAPC with 5% and 10% perdeuterated trioctylphosphate (DTOP), which detects only the polymer motion. Fairly good line shape simulations and agreement between the lattice model and the fitting results at low diluent concentrations are obtained in all cases. Restricted cone motion best describes the slow-moving component in the ³¹P line shape fittings. For the fast component, rotational Brownian diffusion with a distribution of correlation times corresponding to a stretched exponential function is used. An activation energy E_a of 56 kJ/mol and an exponent of 0.7 for the fractional exponential correlation function are obtained and used to calculate the mechanical loss peak which was compared with the experimental loss data. The plateau character of the fractional population as a function of temperature can also be interpreted and understood in terms of the lattice model.     

金属核的磁共振研究*Ⅱ含磷配体铂(Ⅱ)络合物的195Pt和31P-NMR谱

本文测定了12个含苯基环戊基磷、亚磷酸、卤素等配体的铂(Ⅱ)络合物的¹⁹⁵Pt、³¹P-NMR谱,考察了溶剂、浓度、温度对¹⁹⁵Pt谱的影响,研究了¹⁹⁵Pt、³¹P化学位移、偶合常数与络合物几何构型的关系及对卤素的依赖关系。讨论1,2-丙二胺溶液中络合物³¹P谱的变化,以及各种含亚磷酸配体的铂络合物¹⁹⁵Pt和³¹P谱的变化。     

The surface structure of catalysts activated with hydrogen donors as elucidated by multinuclear solid-state NMR

¹H, ²⁷Al and ³¹P MAS, and ¹³C and ²⁹Si CP/MAS NMR spectroscopies, were used to characterize catalysts of Pd supported on various solids including SiO₂, AlPO₄ and Mg₃(PO₄)₂ that were activated with the chiral hydrogen-donor limonene. The above-mentioned techniques were used to check for the formation of an organopalladium complex between Pd²⁺ atoms and the olefin bonds in the limonene molecule on the catalyst surface. The results are compared with those obtained for catalysts activated in a hydrogen stream.     

双环磷酸酯类化合物NMR结构效应研究

用现有理论说明不了双环磷酸酯类化合物³¹P NMR化学位移的变化。本文在我们提出的核外电子云球对称效应原理基础上,用量子化学和分子力学计算的参数,表达了这类化合物³¹P化学位移变化的规律,同时还研究了它们的¹³C NMR化学位移和偶合常数的取代基效应。     

31P double-quantum solid-state NMR study of phosphoroorganic compounds with (O)P-O-P-(O), (S)P-O-P(S) and (S)P-S-P(O) unit

In this work we have tested applicability of the commonly used double quantum recoupling sequence POST-C7 to study of ³¹P–³¹P geometrical constraints for phosphoroorganic model compounds with different chemical shift anisotropy (CSA) and distinct molecular dynamics in the crystal lattice. Our results clearly show that even with large CSA, POST-C7 gives good efficiency of ³¹P double-quantum excitations. Moreover, large amplitude molecular motion only slightly disturb ³¹P build-up curve. χ² error analysis is used for verification of values and orientations of chemical shift tensors (CST) parameters employed for simulation of POST-C7 buildup curves.     

P and N solid-state nuclear magnetic resonance spectroscopic study of some monophospha-λ-azenes

³¹P Cross-polarization magic-angle spinning nuclear magnetic resonance (CP-MAS NMR) spectra of eight monophospha-λ⁵-azenes were measured at room temperature. Three of these compounds, with 2-OH substituents, are in principle capable of taking part in the equilibrium process. However, only the open form, tautomer A, is found in the present study. ¹⁵N CP-MAS NMR spectra support the results. The most shielded component of the ³¹P chemical shift tensor lies in the direction of the P=N bond.     

NMR探针分子表征分子筛酸性的理论研究

用量子化学计算的方法,采用三甲基氧膦（TMPO）、吡啶和三甲基膦（TMP）3种探针分子,研究了工业上常用的3种分子筛H-Y、H-ZSM5、H-MOR的Bronsted酸强度,讨论了这3种探针分子化学位移与Bronsted相对酸强度的相关性,揭示了各种探针分子在表征Bronsted酸性上的适用性.     

Residual 31P, 35,37Cl dipolar coupling in 31P MAS spectra of chlorocyclophosphazenes

In ³¹P MAS NMR spectra of chlorocyclophosphazenes, characteristic splittings have been observed for PCl or PCl₂ groups. At different applied magnetic fields, the fine structure and total width of the patterns change in a characteristic way, demonstrating that the splittings are due to indirect spin–spin and residual dipolar interactions with the chlorine nuclei directly bonded to phosphorus. For trans-nongeminal N₃P₃Cl₃(NMe₂)₃ and N₃P₃Cl₆ as examples, the spectra have been analyzed to obtain information on chlorine nuclear quadrupole coupling constants and ^35,37Cl, ³¹P indirect spin–spin coupling constants. Neglect of these interactions may result in misinterpretations of the multiplicity in ³¹P MAS spectra of chlorophosphazenes.     

Li1+2xTi2-xMgxP3O12固溶体系统结构31P NMR研究

本文应用固体高分辨³¹P NMR技术,以P原子作为结构探针,对以LiTi2P₃O₁₂为基质的Mg掺杂固溶体系统快离子导体的结构进行了研究。并利用P原子第二配位层阳离子场强与其化学位移的关系,确定了不同化学位移³¹P NMR谱线与固溶体结构中P原子局部结构单元Q°之间的关系,解释了Mg的掺入所引起的晶体结构的变化。     

Double-quantum NMR spectroscopy based on finite pulse RFDR

We demonstrate that the finite pulse RFDR sequence (J. Chem. Phys. 114 (2001) 8473) can be used effectively for ³¹P double-quantum NMR spectroscopy at a spinning frequency of 10 kHz. The ³¹P NMR data measured for hydroxyapatite and octacalcium phosphate show that sizable double-quantum excitation efficiency can be obtained with the ratio of the recoupling field to spinning frequency set equal to 1.67.