Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Magic”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources
PubMed2004

1H high-resolution magic-angle spinning (HR-MAS) NMR analysis of ligand density on resins using a resin internal standard.

We recently attempted to generate an affinity chromatography adsorbent to purify cytochrome P450 4A1 by coupling 11-(1'-imidazolyl)-3,6,9-trioxaundecanoic acid to Toyopearl AF-Amino 650 M resin. Variations in ligand density for several resin batches were quantified by high-resolution magic-angle spinning (HR-MAS) NMR spectroscopy using a novel resin internal standard. The uniquely designed ImQ internal resin standard yields its signature resonance in a transparent region of the analyte spectrum making suppression of the polymer background unnecessary. This method enabled us to target a reasonable ligand density for enzyme purification and provides an advantageous alternative to quantitation against soluble standards or protonated solvent.

Animals↗
PubMed2001

Increased signal intensity on fat-suppressed three-dimensional T1-weighted pulse sequences in patellar tendon: magic angle effect?

OBJECTIVE: To assess the frequency of increased signal intensity in the patellar tendon using three-dimensional T1-weighted MRI pulse sequences. DESIGN AND PATIENTS: Sixty patients were examined with a 1.0 T scanner (15 mT/m gradient strength) using a quadrature coil. Three pulse sequences were applied in the sagittal plane: PD turbo spin echo (PD-TSE), 3D T1-weighted gradient echo with fat suppression (3D-T1-FFE-FS) and 3D T1-weighted echo planar imaging with fat suppression (3D-T1-EPI-FS). The high signal intensity areas were measured in their maximum length. The angle of the patellar tendon relative to the main field position was measured in the same slice. In eight patients with anterior knee pain, and in 11 with no anterior knee pain, a fourth T2-weighted TSE pulse sequence (T2-TSE) was obtained to rule out patellar tendinitis. RESULTS: The correlation of the high signal intensity areas with the relative position of the tendon was found to be significant with the 3D sequences (P = 0.03 for 3D-T1-FFE-FS and P = 0.003 for 3D-T1-EPI-FS). The length of the high signal intensity area in the tendon was 5.4 mm with 3D-T1-FFE-FS, 4.9 mm with 3D-T1-EPI-FS and 3.1 mm with PD-TSE images. No patellar tendinitis was demonstrated on the T2-TSE images. CONCLUSION: The magic angle effect is commonly observed in the 3D based T1-weighted pulse sequences with fat suppression. The presence of the above sign must be recognized by radiologists, so that misdiagnosis of patellar tendinitis is avoided.

Adolescent↗
PubMed2006

Magic angle effect in MR imaging of ankle tendons: influence of foot positioning on prevalence and site in asymptomatic subjects and cadaveric tendons.

The influence of foot positioning on prevalence of the magic angle effect (MAE) in ankle tendons was investigated. In 30 asymptomatic volunteers and five cadaveric feet, MR imaging of the ankle was performed in the supine (neutral position of the foot) and prone (plantar-flexed foot) position. MAE was considered if increased T1-weighted signal at a certain site was seen in one position only. Histological correlation was obtained at 25 sites of the cadaveric posterior tibialis tendons (PTT). MAE occurred in 6/30 vs 1/30 (supine vs prone) anterior tibialis tendons (ATT), 30/30 vs 0/30 extensor hallucis longus and 27/30 vs 0/30 extensor digitorum longus tendons, 29/30 vs 0/30 PTTs, 30/30 vs 0/30 flexor digitorum and flexor hallucis longus tendons, 30/30 vs 1/30 peroneus brevis and 23/30 vs 1/30 peroneus longus tendons. At 12/25 cadaveric PTT sites where MAE was exclusively responsible for the increased signal, histology revealed normal tissue (11/12) or minimal degeneration (1/12). In conclusion, the supine body position with neutral position of the foot, a high prevalence (77-100%) of MAE in ankle tendons except for the ATT (20%) is seen. MAE is almost absent in the prone body position with plantar flexion of the foot.

Adult↗
PubMed2002

Drug-eluting stent: the "magic bullet" for prevention of restenosis?

The need for repeat interventions after initially successful PTCA due to restenosis has been called the "Archilles heel" of a percutaneous revascularization procedure. The incidence of restenosis varies between 20-50 % depending on the stent material, the presence of risk factors, and the location of vascular disease. Some risk factors such as diabetes have been clearly identified, others are currently debated. After years of failures trying to reduces restenosis rates, locally administered antiproliferative means have been shown to successfully inhibit excessive cell growth in response to PTCA. Local radiotherapy of in-stent restenosis results in a reduction of recurrent stenosis versus a conventional PTCA procedure. However, long-term evaluation indicated that restenosis may only be delayed with radiation therapy. Moreover, the restenosis rates were reduced, but the restenotic process was not eliminated. Coronary stents eluting the anti-proliferative agent rapamycin have demonstrated for the first time, that restenosis rates of zero percent are achievable after percutaneous revascularization procedures. Thus, it is intriguing to believe that the elimination of restenosis may have become reality. The purpose of this review is to discuss, whether a stent eluting drugs should be considered as the "magic bullet" for prevention of restenosis after PTCA.

Angioplasty, Balloon, Coronary↗
PubMed2004

High-resolution magic angle spinning 1H NMR spectroscopy of metabolic changes in rabbit lens after treatment with dexamethasone combined with UVB exposure.

BACKGROUND: Long-term steroid treatment and UVB exposure are well-known cataractogenic factors. The purpose of this study was to investigate metabolic changes in the rabbit lens after long-term dexamethasone treatment in combination with UVB exposure, using high-resolution magic angle spinning proton nuclear magnetic resonance (HR-MAS (1)H NMR) spectroscopy to analyse intact lens tissues. METHODS: Rabbits received topical doses of 0.1% dexamethasone or 0.9% saline (50 microl) four times daily for 36 days. On day 37, the eyes were exposed to UVB radiation (2.05 J/cm(2)). Twenty-four hours later the animals were killed, and HR-MAS (1)H NMR spectra of lens tissues were obtained. RESULTS: More than 15 major metabolites were assigned in NMR spectra of rabbit lenses. The combined treatment with dexamethasone and UVB induced large reductions in the concentration of reduced glutathione, inositols, taurine and lactate compared with normal lenses. Concurrently, the levels of glucose, sorbitol and sorbitol-3-phosphate were increased. After exposure to UVB radiation only, the most significant finding was a decrease in the concentration of lactate. No lens opacities were detected. CONCLUSIONS: HR-MAS (1)H NMR spectroscopy was found to be an efficient tool for analysis of intact lens tissues. High-resolution NMR spectra of intact lens tissue enabled metabolic changes to be quantified. Long-term treatment with dexamethasone combined with UVB exposure induced substantial metabolic changes, dominated by osmolytic regulation processes and loss of glutathione.

Administration, Topical↗
PubMed2004

Cervical cancer tissue characterized by high-resolution magic angle spinning MR spectroscopy.

OBJECTIVE: In recent years, high-resolution magic angle spinning (HR MAS) has provided the opportunity to explore detailed biochemical composition of intact tissue. Previous studies of intact cervical biopsies with high-resolution magnetic resonance spectroscopy (MRS) have correlated well with histopathology. Lactate level in cervical cancer tissue has been found to correlate to metastatic spread. The purpose of this study was to explore the potential of the HR MAS technique as a tool for chemical characterization of cervical cancer tissue. MATERIALS AND METHODS: Tissue samples from the cervix were collected after hysterectomy from patients with cervical cancer (n=8) and patients with nonmalignant disease (n=8). The tissue specimens were analyzed using HR MAS MR spectroscopy combined with principal component analysis (PCA). RESULTS: The resulting spectra showed resolution comparable with high-resolution MR spectra of extracts. Multivariate analysis confirmed that MAS spectra classified according to patient diagnosis. CONCLUSION: Malignant tissue of the cervix differed from nonmalignant tissue with regard to higher levels of cholines and amino acid residues and lower levels of glucose.

Adenocarcinoma↗
PubMed2005

High-resolution magic-angle spinning 13C NMR spectroscopy of cerebral tissue.

Monitoring the metabolism of (13)C-labelled substrates by biological tissues allows both the rate of metabolism and the relative importance of metabolic pathways to be determined. In this study high-resolution magic-angle spinning (HRMAS) (13)C NMR spectroscopy is assessed as a technique for determining the labelling of metabolites in brain slices. Freshly prepared rat brain slices were superfused in isotonic salt solution containing [1-(13)C] glucose. HRMAS (1)H and (13)C NMR spectra were acquired of the slices ( approximately 10 mg) at 3 degrees C. Using (1)H NMR spectroscopy it was demonstrated that the concentration of key metabolites indicative of metabolic degradation, including N-acetyl aspartate and lactate, did not change significantly across the approximately 11 h time period required for (13)C NMR spectra. The approach produced high-resolution spectra of intact tissue with the labelling patterns of tissues being indicative of both labelling via pyruvate dehydrogenase found in both neuronal and glial cells, and pyruvate carboxylase, found only within glial cells. This approach is a versatile tool for monitoring the compartmentation of metabolites directly, and will also allow the investigation of aqueous and lipid metabolites simultaneously.

Algorithms↗
PubMed2004

Probing membrane protein orientation and structure using fast magic-angle-spinning solid-state NMR.

One and two-dimensional solid-state NMR experiments are discussed that permit probing local structure and overall molecular conformation of membrane-embedded polypeptides under Magic Angle Spinning. The functional dependence of a series of anisotropic recoupling schemes is analyzed using theoretical and numerical methods. These studies lead to the construction of a set of polarization dephasing or transfer units that probe local backbone conformation and overall molecular orientation within the same NMR experiment. Experimental results are shown for a randomly oriented peptide and for two model membrane-peptides reconstituted into lipid bilayers and oriented on polymer films according to a method proposed by Bechinger et al.

Anisotropy↗
PubMed2005

Residual backbone and side-chain 13C and 15N resonance assignments of the intrinsic transmembrane light-harvesting 2 protein complex by solid-state Magic Angle Spinning NMR spectroscopy.

This study reports the sequence specific chemical shifts assignments for 76 residues of the 94 residues containing monomeric unit of the photosynthetic light-harvesting 2 transmembrane protein complex from Rhodopseudomonas acidophila strain 10050, using Magic Angle Spinning (MAS) NMR in combination with extensive and selective biosynthetic isotope labeling methods. The sequence specific chemical shifts assignment is an essential step for structure determination by MAS NMR. Assignments have been performed on the basis of 2-dimensional proton-driven spin diffusion (13)C-(13)C correlation experiments with mixing times of 20 and 500 ms and band selective (13)C-(15)N correlation spectroscopy on a series of site-specific biosynthetically labeled samples. The decreased line width and the reduced number of correlation signals of the selectively labeled samples with respect to the uniformly labeled samples enable to resolve the narrowly distributed correlation signals of the backbone carbons and nitrogens involved in the long alpha-helical transmembrane segments. Inter-space correlations between nearby residues and between residues and the labeled BChl a cofactors, provided by the (13)C-(13)C correlation experiments using a 500 ms spin diffusion period, are used to arrive at sequence specific chemical shift assignments for many residues in the protein complex. In this way it is demonstrated that MAS NMR methods combined with site-specific biosynthetic isotope labeling can be used for sequence specific assignment of the NMR response of transmembrane proteins.

Amino Acid Sequence↗
PubMed2005

Characterisation of hydrogen bonding networks in RNAs via magic angle spinning solid state NMR spectroscopy.

It is demonstrated that the spatial proximity of (1)H nuclei in hydrogen bonded base-pairs in RNAs can be conveniently mapped via magic angle spinning solid state NMR experiments involving proton spin diffusion driven chemical shift correlation of low gamma nuclei such as the imino and amino nitrogens of nucleic acid bases. As different canonical and non-canonical base-pairing schemes encountered in nucleic acids are characterised by topologically different networks of proton dipolar couplings, different base-pairing schemes lead to characteristic cross-peak intensity patterns in such correlation spectra. The method was employed in a study of a 100 kDa RNA composed of 97 CUG repeats, or (CUG)(97) that has been implicated in the neuromuscular disease myotonic dystrophy. (15)N-(15)N chemical shift correlation studies confirm the presence of Watson-Crick GC base pairs in (CUG)(97).

Base Pairing↗
PubMed2006

Solid state NMR at high magic angle spinning frequencies: dipolar chemical shift correlation with adiabatic inversion pulse based RF pulse schemes.

The efficacy of hetero- and homonuclear dipolar recoupling employing tanh/tan adiabatic inversion pulse based RF pulse schemes has been examined at high magic angle spinning (MAS) frequencies via numerical simulations and experimental measurements. An approach for minimising the recoupling RF power level is presented, taking into consideration the spinning speed, the range of resonance offsets and H(1) inhomogeneities and the available RF field strength. This involves the tailoring of the frequency and amplitude modulation profiles of the inversion pulses. The applicability of tanh/tan pulse based dipolar recoupling schemes to spinning speed regimes where the performance with conventional rectangular pulses may not be satisfactory is demonstrated.

Carbon Isotopes↗
PubMed2006

Magic-angle spinning solid-state NMR of a 144 kDa membrane protein complex: E. coli cytochrome bo3 oxidase.

Recent progress in magic-angle spinning (MAS) solid-state NMR (SSNMR) has enabled multidimensional studies of large, macroscopically unoriented membrane proteins with associated lipids, without the requirement of solubility that limits other structural techniques. Here we present initial sample preparation and SSNMR studies of a 144 kDa integral membrane protein, E. coli cytochrome bo(3) oxidase. The optimized protocol for expression and purification yields approximately 5 mg of the enzymatically active, uniformly (13)C,(15)N-enriched membrane protein complex from each liter of growth medium. The preparation retains endogenous lipids and yields spectra of high sensitivity and resolution, consistent with a folded, homogenous protein. Line widths of isolated signals are less than 0.5 ppm, with a large number of individual resonances resolved in the 2D and 3D spectra. The (13)C chemical shifts, assigned by amino acid type, are consistent with the secondary structure previously observed by diffraction methods. Although the structure is predominantly helical, the percentage of non-helical signals varies among residue types; these percentages agree well between the NMR and diffraction data. Samples show minimal evidence of degradation after several weeks of NMR data acquisition. Use of a triple resonance scroll resonator probe further improves sample stability and enables higher power decoupling, higher duty cycles and more advanced 3D experiments to be performed. These initial results in cytochrome bo(3) oxidase demonstrate that multidimensional MAS SSNMR techniques have sufficient sensitivity and resolution to interrogate selected parts of a very large uniformly (13)C,(15)N-labeled membrane protein.

Amino Acid Sequence↗
PubMed2006

Spectral editing: selection of methyl groups in multidimensional solid-state magic-angle spinning NMR.

A simple spectroscopic filtering technique is presented that may aid the assignment of (13)C and (15)N resonances of methyl-containing amino-acids in solid-state magic-angle spinning (MAS) NMR. A filtering block that selects methyl resonances is introduced in two-dimensional (2D) (13)C-homonuclear and (15)N-(13)C heteronuclear correlation experiments. The 2D (13)C-(13)C correlation spectra are recorded with the methyl filter implemented prior to a (13)C-(13)C mixing step. It is shown that these methyl-filtered (13)C-homonuclear correlation spectra are instrumental in the assignment of C(delta) resonances of leucines by suppression of C(gamma)-C(delta) cross peaks. Further, a methyl filter is implemented prior to a (15)N-(13)C transferred-echo double resonance (TEDOR) exchange scheme to obtain 2D (15)N-(13)C heteronuclear correlation spectra. These experiments provide correlations between methyl groups and backbone amides. Some of the observed sequential (15)N-(13)C correlations form the basis for initial sequence-specific assignments of backbone signals of the outer-membrane protein G.

Amides↗
PubMed2006

Signal assignment and secondary structure analysis of a uniformly [13C, 15N]-labeled membrane protein, H +-ATP synthase subunit c, by magic-angle spinning solid-state NMR.

Signal assignment and secondary structural analysis of uniformly [13C, 15N] labeled H+-ATP synthase subunit c from E. coli (79 residues) in the solid state were carried out by two- and three-dimensional solid-state NMR under magic-angle spinning. The protein took on a unique structure even in the solid state from the 13C linewidths of about 1.7 ppm. On the basis of several inter- and intra-residue 13C-13C and 13C-15N chemical shift correlations, 78% of Calpha, 72% of Cbeta, 62% of C' and 61% of NH signals were assigned, which provided the secondary structure information for 84% of the 79 residues. Here, inter-residue correlations involving Gly, Ala, Pro and side-chains and a higher resolution in the 3D spectrum were significantly useful for the sequence specific assignment. On top of this, the 13C-13C correlation spectra of subunit c was analyzed by reproducing experimental cross peaks quantitatively with chemical shift prediction and signal-intensity calculation based on the structure. It revealed that the subunit c in the solid state could be specified by alpha-helices with a loop structure in the middle (at sequence 41-45) as in the case of the solution structure in spite of additional extended conformations at 76-79 at the C-terminus.

Amino Acid Sequence↗
PubMed1985

Mouth and genital ulcers with inflamed cartilage: MAGIC syndrome. Five patients with features of relapsing polychondritis and Behçet's disease.

Five patients with features of coexistent relapsing polychondritis and Behçet's disease are described. Review of the literature supports the overlap of the clinical manifestations of these two conditions. A common immunologic abnormality is likely, and elastin is cited as a possible target antigen. The "mouth and genital ulcers with inflamed cartilage (MAGIC) syndrome" is the proposed name for this entity.

Adult↗
PubMed1995

Protein-chromophore interactions in alpha-crustacyanin, the major blue carotenoprotein from the carapace of the lobster, Homarus gammarus. A study by 13C magic angle spinning NMR.

MAS (magic angle spinning) 13C NMR has been used to study protein-chromophore interactions in alpha-crustacyanin, the blue astaxanthin-binding carotenoprotein of the lobster, Homarus gammarus, reconstituted with astaxanthins labelled with 13C at the 14,14' or 15,15' positions. Two signals are seen for alpha-crustacyanin containing [14,14'-13C2]astaxanthin, shifted 6.9 and 4.0 ppm downfield from the 134.1 ppm signal of uncomplexed astaxanthin in the solid state. With alpha-crustacyanin containing [15,15'-13C2]astaxanthin, one essentially unshifted broad signal is seen. Hence binding to the protein causes a decrease in electronic charge density, providing the first experimental evidence that a charge redistribution mechanism contributes to the bathochromic shift of the astaxanthin in alpha-crustacyanin, in agreement with inferences based on resonance Raman data [Salares, et al. (1979) Biochim. Biophys. Acta 576, 176-191]. The splitting of the 14 and 14' signals provides evidence for asymmetric binding of each astaxanthin molecule by the protein.

Animals↗
PubMed1995

Changes in elastin in human atherosclerotic aorta: carbon-13 magic angle sample-spinning NMR studies.

The dipolar-decoupled, natural abundance Fourier transform and cross polarization [13C] NMR spectra of human elastin isolated from atherosclerotic aorta and aortas free of atherosclerotic lesions, bovine insoluble elastin and bovine kappa-elastin were obtained at 75 MHz, with 5-7 kHz magic angle sample spinning. Spin-lattice rotating frame relaxation parameters were measured for protons (T1pH) and for carbons (T1pC) at room temperature. Proton relaxation times were shorter for bovine kappa-elastin (T1pH = 1.7 ms) than for bovine elastin (T1pH) = 3.5 ms). Calculation of T1pH showed no differences between human normal and atherosclerotic elastins. T1pC were shorter for bovine kappa-elastin than for bovine elastin. While alpha-carbons of human atherosclerotic elastin had shorter T1pC than normal elastin alpha carbons, carbons from hydrophobic amino acid side chains had longer T1pC for atherosclerotic then for normal elastin. Biochemical studies of aortic wall and purified elastin showed significantly increased content of lipids (atherosclerotic 67.7 mmol/g elastin, control 54.7 mmol/g elastin) and calcium (atherosclerotic 38.3 mmol/g elastin, control 19.6 mmol/g elastin). Changes in relaxation parameter values may be caused by the structural and biochemical changes in human elastin. Increased mobility of polypeptide chains as based on the model kappa-elastin studies is caused by the action of elastase. Restriction of mobility is expected to be caused by the accumulation of lipids and calcium.

Analysis of Variance↗