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PubMed1985

Synthesis of riboguanosine pentaphosphate ppprGpp (Magic Spot II) via a phosphotriester approach.

The bifunctional phosphorylating reagent O,O-bis[1-benzotriazolyl]phosphoromorpholidate was used to introduce a 5'-O-triphosphate and a 3'-O-diphosphate function in a partially protected riboguanosine. Pilot studies indicated that protection of the 2'-OH of ribonucleosides with the acid-labile tetrahydropyranyl group, instead of the more labile 4-methoxytetrahydropyran-4-yl group, was most satisfactory for the preparation of the Magic Spot II.

Guanine Nucleotides↗
PubMed2004

Identification of NH...N hydrogen bonds by magic angle spinning solid state NMR in a double-stranded RNA associated with myotonic dystrophy.

RNA plays a central role in biological processes and exhibits a variety of secondary and tertiary structural features that are often stabilized via hydrogen bonds. The distance between the donor and acceptor nitrogen nuclei involved in NH...N hydrogen bonds in nucleic acid base pairs is typically in the range of 2.6-2.9 A. Here, we show for the first time that such spatial proximity between 15N nitrogen nuclei can be conveniently monitored via magic angle spinning solid state NMR on a uniformly 15N-labelled RNA. The presence of NH.N hydrogen bonds is reflected as cross-peaks between the donor and acceptor nitrogen nuclei in 2D 15N dipolar chemical shift correlation spectra. The RNA selected for this experimental study was a CUG repeat expansion implicated in the neuromuscular disease myotonic dystrophy. The results presented provide direct evidence that the CUG repeat expansion adopts a double-stranded conformation.

Base Pairing↗
PubMed2000

Quantification of microheterogeneity in glioblastoma multiforme with ex vivo high-resolution magic-angle spinning (HRMAS) proton magnetic resonance spectroscopy.

Microheterogeneity is a routinely observed neuropathologic characteristic in brain tumor pathology. Although microheterogeneity is readily documented by routine histologic techniques, these techniques only measure tumor status at the time of biopsy or surgery and do not indicate likely tumor progression. A biochemical screening technique calibrated against pathologic standards would greatly assist in predicting tumor progression from its biological activity. Here we demonstrate for the first time that proton magnetic resonance spectroscopy (1H MRS) with high-resolution magic-angle spinning (HRMAS), a technique introduced in 1997, can preserve tissue histopathologic features while producing well-resolved spectra of cellular metabolites in the identical intact tissue specimens. Observed biochemical alterations and tumor histopathologic characteristics can thus be correlated for the same surgical specimen, obviating the problems caused by tumor microheterogeneity. We analyzed multiple specimens of a single human glioblastoma multiforme surgically removed from a 44-year-old patient. Each specimen was first measured with HRMAS 1H MRS to determine tumor metabolites, then evaluated by quantitative histopathology. The concentrations of lactate and mobile lipids measured with HRMAS linearly reflected the percentage of tumor necrosis. Moreover, metabolic ratios of phosphorylcholine to choline correlated linearly with the percentage of the highly cellular malignant glioma. The quantification of tumor metabolic changes with HRMAS 1H MRS, in conjunction with subsequent histopathology of the same tumor specimen, has the potential to further our knowledge of the biochemistry of tumor heterogeneity during development, and thus ultimately to improve our accuracy in diagnosing, characterizing, and evaluating tumor progression.

Adult↗
PubMed1997

Mouth and genital ulcers with inflamed cartilage (MAGIC syndrome): a case report and literature review.

A 39-year-old woman had relapsing polychondritis and Behçet's disease, which was described as mouth and genital ulcers with inflamed cartilage syndrome (MAGIC). Serologic human leukocyte antigen analysis showed A24 (9), A31 (19), B56 (22), B62 (15), Cw6, DR4, DR9. Human leukocyte antigen allele analysis revealed DRB1* 0406/0901, DQA1* 0301/0301, DQB1* 0302/0303, DPB1* 0201/0501 through determining the genotype using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Treatment with methotrexate (5 mg/week) and pentoxifylline (300 mg/d) was effective to control oral ulcers, erythema nodosum, and arthritis.

Adult↗
PubMedDate not supplied

The gastric bubble: medicine, magic or mania?

This paper is presented to acquaint the GIA with a new medical procedure that is rapidly gaining popularity throughout the United States. It includes a brief discussion of the medical device itself and the technique of implantation as well as indications and contraindications for its use. In addition, an overview of the program developed at Placentia-Linda Community Hospital, Placentia, CA, is offered. Personal reflections are also rendered regarding the unique nursing opportunities afforded by this procedure and its accompanying follow-up program. In conclusion, this paper will substantiate, with personal experience and early supportive research data, the parallels between the medicinal value, the magic, and the mania accompanying the Gastric Bubble.

Endoscopy, Digestive System↗
PubMed2002

Aromatherapy: mythical, magical, or medicinal?

Aromatherapy, a branch of herbology, is one of the fastest growing therapies in the world today. Historically, essential oils are best used in the form of massage or bath oils or inhalations. Frequently, it is reported that aromatherapy leaves one feeling uplifted, stimulated, invigorated, or rejuvenated, depending on the oil used. When inhaled, the various aromas penetrate the bloodstream via the lungs causing physiologic changes. In turn, the limbic system, which controls our emotions and memories, is affected. Some consider aromatherapy as mystical or magical; others, however, are attempting to validate empirically this ancient therapy as medicinal.

Aromatherapy↗
PubMed2004

In vitro 1H-magnetic resonance spectroscopy of Barrett's esophageal mucosa using magic angle spinning techniques.

OBJECTIVES: In vitro proton magnetic resonance spectroscopy (MRS) allows changes in cell membrane lipid structure associated with dysplasia and malignant transformation to be investigated. Magic angle spinning (MAS) MRS allows small esophageal tissue specimens to be studied directly without the need to extract the tissue, but it is not known how intact the tissue architecture remains after MAS. We report the first prospective MAS MRS study of Barrett's esophagus using endoscopic biopsies with direct histological correlation. METHODS: Biopsies were obtained during surveillance esophagoscopy from Barrett's epithelium and adjacent normal squamous epithelium in 16 patients (34 samples). High-resolution MAS MRS was performed at 500 MHz. Following MRS, the histology was evaluated. A further, separate group of 14 biopsies were examined histologically to assess architectural damage caused by tissue preservation alone. RESULTS: For squamous and Barrett's epithelium, respectively, metabolite ratios of choline-containing compounds to creatine plus phosphocreatine (Cho/Cr) were 1.99 and 5.65 (P < 10) and methyl lipid to creatine plus phosphocreatine ratios (lipid-CH3/Cr) were 4.07 and 7.4 (P < 10). There was no significant difference in histological preservation between the squamous and Barrett's mucosa without MRS (z = 0.67, P = 0.61), but significant differences were found post-MAS MRS (z = 4.06, P < 0.0001). CONCLUSIONS: Squamous and Barrett's epithelium can be distinguished metabolically, based on Cho/Cr and lipid-CH3/Cr ratios. Although MAS does affect the histological architecture in Barrett's epithelium, compared with squamous epithelium, direct histological assessment was possible in the majority of samples.

Adult↗
PubMed1980

Magic angle sample spinning in inhomogeneously broadened biological systems.

Recent advances in magic angle sample spinning experiments now permit observation of dilute spin high resolution n.m.r. spectra of arbitrary powder samples. In the 'slow-spinning' régime, for which the spinning rate is less than the size of the interaction that is being averaged, the spectra exhibit rotational side bands whose intensities contain information on chemical shift anisotropies. A technique for extracting shift anisotropies from side band intensities is discussed. Since many biologically interesting systems are solid or semi-solid in nature, this technique should find wide application to biological systems. Two illustrations of the point are given in this paper, namely, n.m.r. studies of membranes and of the phosphate-containing phases of bone.

Animals↗
PubMed2004

Recent developments in solid-state magic-angle spinning, nuclear magnetic resonance of fully and significantly isotopically labelled peptides and proteins.

In recent years, a large number of solid-state nuclear magnetic resonance (NMR) techniques have been developed and applied to the study of fully or significantly isotopically labelled ((13)C, (15)N or (13)C/(15)N) biomolecules. In the past few years, the first structures of (13)C/(15)N-labelled peptides, Gly-Ile and Met-Leu-Phe, and a protein, Src-homology 3 domain, were solved using magic-angle spinning NMR, without recourse to any structural information obtained from other methods. This progress has been made possible by the development of NMR experiments to assign solid-state spectra and experiments to extract distance and orientational information. Another key aspect to the success of solid-state NMR is the advances made in sample preparation. These improvements will be reviewed in this contribution. Future prospects for the application of solid-state NMR to interesting biological questions will also briefly be discussed.

Capsid Proteins↗
PubMed2006

Stochastic molecular motions in the nematic, smectic-A, and solid phases of p,p'-di-n-heptyl-azoxybenzene as seen by quasielastic neutron scattering and 13C cross-polarization magic-angle-spinning NMR.

Molecular rotational dynamics in p,p'-di-n-heptyl-azoxybenzene was studied by means of quasielastic neutron scattering (QENS) and 13C cross-polarization magic-angle-spinning (CPMAS) NMR. Fast reorientation of the hydrogen nuclei was observed by QENS in the two liquid crystalline (LC) phases nematic and smectic A, as well as in the crystalline phase. The latter could not be restricted to the -CH3 rotations alone, and a clear indication was found of some other reorientation motions persisting in the crystal. Two Lorentz-type components convoluted with the resolution function gave an excellent fit to the QENS spectra in both LC phases. The narrow (slow) component was attributed to the reorientation of the whole molecule around the long axis. The corresponding characteristic time of approximately 130 ps agreed well with the values obtained in recent dielectric relaxation and 2H NMR studies. The full width at half maximum of the broader (fast) component shows a quadratic Q dependence (Q is the momentum transfer). Hence the corresponding motions could be described by a stretched exponential correlation function and were interpreted as various "crankshaft-type" motions within the alkyl tails. The 13C CPMAS experiments fully corroborated the QENS results, sometimes considered ambiguous in complex systems.

Journal Article↗
PubMed2000

Measurement of the dipole and electric quadrupole strength distributions up to 10 MeV in the doubly magic nuclei 40Ca and 48Ca

The doubly magic nuclei 40Ca and 48Ca have been studied in high resolution photon scattering experiments. We have derived absolute dipole and quadrupole excitation strengths up to 10 MeV. Evidence was found for a two-phonon quadrupole-octupole state in 48Ca. At higher energies in contrast to 40Ca, a concentration of dipole strength is observed in 48Ca which is discussed in terms of a pygmy resonance originating from the large neutron excess.

Journal Article↗
PubMed2001

Magic nucleus 132Sn and its one-neutron-hole neighbor 131Sn.

Prompt and delayed gamma-ray cascades in doubly magic 132Sn and its neighbor 131Sn have been studied at Gammasphere using a 248Cm fission source. Isotopic assignments of unknown gamma rays were based on coincidences with known transitions in A = 112-116 Pd fission partners. The yrast level spectra of both tin nuclei are interpreted using empirical nucleon-nucleon interactions from the 132Sn and 208Pb regions. Results include identification of the (nuf(7/2)h(-1)(11/2))9(+) aligned state in 132Sn and of extensive (nuf(7/2)h(-2)(11/2)), (nuf(7/2)d(-1)(3/2)h(-1)(11/2)) and (nuh(-1)(11/2)x3(-)) multiplets in 131Sn. The previously reported beta(-) decay of an unusual 131In high-spin isomer to levels in 131Sn is also elucidated.

Journal Article↗
PubMed2001

Superdeformation in the doubly magic nucleus (40)(20)Ca(20).

A rotational band with seven gamma-ray transitions between states with spin 2 Planck's constant and 16 Planck's constant has been observed in the doubly magic, self-conjugate nucleus (40)(20)Ca(20). The measured transition quadrupole moment of 1.80(+0.39)(-0.29)eb indicates a superdeformed shape with a deformation beta(2) = 0.59(+0.11)(-0.07). The features of this band are explained by cranked relativistic mean field calculations to arise from an 8-particle 8-hole excitation.

Journal Article↗
PubMed2002

Magic numbers in metallo-inorganic clusters: chromium encapsulated in silicon cages.

A systematic theoretical study of the equilibrium geometries and total energies of Cr encapsulated in Si clusters reveals that Cr@Si(12) is more stable than its neighbors. The origin of this enhanced stability is consistent with the 18-electron sum rule commonly used in the synthesis of stable chemical complexes, and may provide a criterion for a systematic search of magic numbers in metalloinorganic clusters. The 6 mu(B) magnetic moment of the caged Cr atom, the largest among the 3d transition metal atoms, is completely quenched. This effect of caging on the properties of transition metal atoms may lead to the synthesis of novel cluster based materials.

Journal Article↗
PubMed2003

Cluster growing process and a sequence of magic numbers.

We present a new theoretical framework for modeling the cluster growing process. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system, and absorbing its energy at each step, we find cluster growing paths up to the cluster sizes of more than 100 atoms. We demonstrate that in this way all known global minimum structures of the Lennard-Jones (LJ) clusters can be found. Our method provides an efficient tool for the calculation and analysis of atomic cluster structure. With its use we justify the magic number sequence for the clusters of noble gas atoms and compare it with experimental observations.

Journal Article↗
PubMed2004

Structure determination of surface magic clusters.

The structure of a type of surface magic cluster is determined by a combination of scanning tunneling microscopy, density-functional calculations, and dynamical low energy electron diffraction. The diffraction method is applicable because these clusters created through hierarchical self-organization of Ga deposited onto a Si(111)-7x7 surface have identical size and structure and form an ordered array with exact translational symmetry. The unprecedented detailed structure information provided by the diffraction measurement is consistent with direct microscopic imaging and theoretical calculations.

Journal Article↗
PubMed2004

Magic polyicosahedral core-shell clusters.

A new family of magic cluster structures is found by genetic global optimization, whose results are confirmed by density functional calculations. These clusters are Ag-Ni and Ag-Cu nanoparticles with an inner Ni or Cu core and an Ag external shell, as experimentally observed for Ag-Ni, and present a polyicosahedral character. The interplay of the core-shell chemical ordering with the polyicosahedral structural arrangement gives high-symmetry clusters of remarkable structural, thermodynamic, and electronic stability, which can have high melting points (they melt higher than pure clusters of the same size), large energy gaps, and (in the case of Ag-Ni) nonzero magnetic moments.

Journal Article↗
PubMed2004

Borderline magic clustering: the fabrication of tetravalent Pb cluster arrays on Si(111)-(7x7) surfaces.

Well-ordered arrays of identical Pb clusters have been fabricated on a Si(111)-(7x7) substrate by the temperature-mediated surface clustering method. Interestingly, these clusters can easily transform into other forms when the growth temperature deviates slightly from the optimal values. In accord with experiments, first-principle total-energy calculations reveal several cluster structures centered on a mixed cluster model involving surface Pb and Si exchange. This borderline Pb/Si(111) system provides a unique, controlled way to study surface magic cluster formation and breakup dynamics.

Journal Article↗