Beryllium fluoride exchange rate accelerated by Mg²⁺ as discovered by ¹⁹F NMR.

Beryllium fluoride is widely used as a phosphoryl analogue in macromolecular studies, which are not only fluoride-sensitive but also magnesium-dependent. The beryllium fluorides are a mixture of different species including BeF3(-) and BeF4(2-) exchanging under thermodynamic equilibrium in neutral aqueous solutions. In the cases of mimicking phosphate group transfer, both beryllium fluoride and the magnesium ion are generally needed.

NASR: an effective approach for simultaneous noise and artifact suppression in NMR spectroscopy.

As a powerful tool for biological analysis, especially protein structure and dynamic studies, nuclear magnetic resonance (NMR) spectroscopy suffers from intrinsic low signal to nose ratio (SNR) and long acquisition time required for multidimensional (nD) experiments. Nonuniform sampling (NUS) can effectively speed up the experiment but often introduces artifacts into the spectrum. In addition to the development of highly sensitive hardware and NMR pulse sequences, data postprocessing is a relative simple and cost-effective method to improve the SNR and suppress the artifacts.

(1)H- (31)P soft-HSQC pulse sequence specifically for detecting phosphomono- and diesters in biological samples.

Purpose: Phosphomono- and diesters (PME and PDE) are important metabolites that are potential biomarkers for a number of cancers. We designed a new NMR pulse sequence, i.e.

Backbone assignment and secondary structure of Rnd1, an unusual Rho family small GTPase.

Rho GTPases have attracted considerable interest as signaling molecules due to their variety of functional roles in cells. Rnd1 is a relatively recently discovered Rho GTPase with no enzymatic activity against its bound GTP nucleotide, setting it apart from other family members. Research has revealed a critical role for Rnd1 not only in neurite outgrowth, dendrite development, axon guidance, but also in gastric cancer and in endothelial cells during inflammation.

Fast detection of choline-containing metabolites in liver using 2D ¹H-¹⁴N three-bond correlation (HN3BC) spectroscopy.

Detection and quantification of total choline-containing metabolites (CCMs) in tissues by magnetic resonance spectroscopy (MRS) has received considerable attention as a biomarker of cancer. Tissue CCMs are mainly choline (Cho), phosphocholine (PCho), and glycerophosphocholine (GPCho). Because the methyl (1)H resonances of tissue CCMs exhibit small chemical shift differences and overlap significantly in 1D (1)H MRS, quantification of individual components is precluded.

Improve the selectively refocused INEPT pulse sequence for detecting phosphomonoesters and phosphodiesters.

In application of the (31)P selectively refocused insensitive nuclei enhanced polarization transfer (srINEPT) technique to the detection of phosphomono- and diesters in tissues, homonuclear couplings between the CH(2)O protons and the NCH(2) protons seriously attenuate the sensitivity. These couplings can be conventionally removed by two soft 180° pulses in the (1)H evolution period which selectively invert the NCH(2) magnetizations. However, the srINEPT pulse sequence can be simplified by replacing the pulse train "soft 180°-hard 180°-soft 180°" with a single soft 180° pulse that selectively inverts the CH(2)O magnetizations.

A selective NMR method for detecting choline containing compounds in liver tissue: the 1H-14N HSQC experiment.

The feasibility of a (1)H-(14)N HSQC experiment on tissues is demonstrated with a mouse liver based on the J couplings between the protons and the quadrupolar nucleus (14)N in choline. Free choline, phosphocholine, and glycerolphosphocholine (1)H-(14)N HSQC signals were selectively observed with all unwanted signals cleanly suppressed. The CH2O signals were well resolved in the two-dimensional spectrum, which can be used for quantitative analyses.

1H-14N HSQC detection of choline-containing compounds in solutions.

Choline nitrogen ((14)N) has a long relaxation time (seconds) which is due to the highly symmetric chemical environments. (14)N in choline also has coupling constants with protons (0.6 Hz to methyl protons, 2.

Gridding and fast Fourier transformation on non-uniformly sparse sampled multidimensional NMR data.

For multidimensional NMR method, indirect dimensional non-uniform sparse sampling can dramatically shorten acquisition time of the experiments. However, the non-uniformly sampled NMR data cannot be processed directly using fast Fourier transform (FFT). We show that the non-uniformly sampled NMR data can be reconstructed to Cartesian grid with the gridding method that has been wide applied in MRI, and sequentially be processed using FFT.

Optimized quantitative DEPT and quantitative POMMIE experiments for 13C NMR.

In quantitative analysis, inverse gated (1)H decoupled (13)C NMR provides higher resolution than (1)H NMR. However, due to the lower sensitivity and longer relaxation time, (13)C NMR experiment takes much longer time to obtain a spectrum with adequate signal-to-noise ratio. The sensitivity can be enhanced with DEPT and INEPT approaches by transferring polarization from (1)H (I) to (13)C (S), but since the enhancements depend on coupling constants ( (1) J SI) and spin systems (SI, SI 2, SI 3), the enhancements for different spin systems are not uniform and quantitative analyses are seriously affected.

Fast nuclear magnetic resonance correlation spectroscopy without diagonal peaks: the "2-1" correlation spectroscopy.

A fast NMR experiment is proposed for measuring correlation spectroscopy (COSY) spectra with diagonal peaks completely removed or largely suppressed. This new pulse sequence is based on double quantum spectroscopy but with delayed detection, so that the double quantum coherence is effectively transferred to single quantum coherence. Therefore, the pulse sequence can be named "2-1" COSY.

Multiple quantum correlated spectroscopy revamped by asymmetric z-gradient echo detection signal intensity as a function of the read pulse flip angle as verified by heteronuclear 1H/31P experiments.

Heteronuclear multiple quantum (n=+/-0 and n=+/-2) correlated spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED) experiments were performed on the spins 31P and 1H in a H3PO4 solution in order to determine the optimum flip angle for the read pulse. It has been shown that for the negative quantum signals, the maximum signals appear at beta=0, and for the positive quantum signals, the maximum signals appear at beta=pi. The CRAZED signals were compared to the single quantum signals in two-pulse two-gradient experiments.

NMR study of the folding-unfolding mechanism for the thrombin-binding DNA aptamer d(GGTTGGTGTGGTTGG).

Hydrogen exchange rates of the imino protons of the thrombin-binding 15 mer DNA aptamer d(G(1)G(2)T(3)T(4)G(5)G(6)T(7)G(8)T(9)G(10)G(11)T(12)T(13)G(14)G(15)) in the presence of Sr(2+) were measured. In the temperature range 15-35 degrees C, the exchange rates of the eight iminos in the quadruplex core were not uniform, with the G(2), G(11) and G(15) iminos exchanging faster, the G(1), G(5), G(10) and G(14) iminos exchanging slower, and the G(6) imino exchanging at a medium rate. In the quadruplex G(1), G(5), G(10) and G(14) adopted syn glycosidic conformation, while G(2), G(6), G(11) and G(15) adopted anti-conformation.

Line shape analyses for water 17O NMR quintet observed in a bacteriophage Pf1 solution at different temperatures.

Partially resolved 17O NMR quintet was observed in a filamentous bacteriophage Pf1 solution at 70 degrees C with a quadrupole splitting approximately 100 Hz. As the temperature decreased, the resolution was reduced but the line shapes were still indicative of residual quadrupole splitting. Line shape analyses were performed using the quadrupolar relaxation theory for spin 5/2.

[The synthesis, 1H NMR and IR study of [(n-Bu)4N]2[Mo2O5(OC10H6O)2] and [(n-Bu)4N]2[Mo4O10 (OC10H6O)2(OCH3)2]].

The title organo-molybdate derivatives are synthesized and their IR, 1H NMR spectra have been determined and the relations between the structures and the 1H NMR and IR parameters have been studied. The results indicate that the red shift of the IR frequency of Mo-O-Mo in [(n-Bu)4N]2[Mo2O5(OC10H6O)2] (complex I) takes place to compare with that in [(n-Bu)4N]2[Mo4O10 (OC10H6O)2(OCH3)2] (complex II) and lower filed shift of 1H NMR of the aromatic H atoms in complex II occurs as contrasted to that in the complex I. It is found also the organo-molybdate derivatives are very sensitive to the acidity of the chemical system.

NMR study on the low-affinity interaction of human serum albumin with diclofenac sodium.

The low-affinity interaction between human serum albumin (HSA) and Diclofenac sodium (DCF) was studied using NMR techniques. Both 13C-NMR chemical shift and linewidth show that the dichlorophenyl ring in DCF molecule plays a primary role in its interaction with HSA. Langmuir adsorption isotherm was applied to evaluate the association constant K and the number of binding sites n of the drug/HSA complex through (1)H-NMR spin-lattice relaxation measurement.

Conformational Flexibility of Deoxyoligonucleotide d(GGTATACC)(2) in Water.

AT-rich deoxyoligonucleotide provides a binding site possibly at the minor groove for some anti-tumor drugs by hydrophobic or Van der Waals interactions. In this paper, it is demonstrated by study of d (GGTATACC)(2) that the DNA-drug interaction may be dependent on the structural flexibility at the minor groove. The solution structure of d (GGTATACC)(2) in water is described by distance-restrained molecular dynamics calculation and it is suggested that d (GGTATACC)(2) in solution maintains the double helix of B-type with trans conformations of base to sugar and C2'-endo conformation for the deoxyribose ring.

Study of hydrolytic kinetics of the hexachlorostannate anion by two-dimensional Sn exchange spectroscopy.

Two-dimensional Sn exchange spectroscopy was applied to study the hydrolytic kinetics of the hexachloro-stannate anion, SnCl . Two Sn exchange spectra for SnCl · 5H O solutions with various HCl concentrations are presented. Magnetization exchanges, which are related to the hydrolysis processes, occur in the SnCl hydrolysis series.