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PubMed2003

Heteronuclear spin decoupling in solid-state NMR under magic-angle sample spinning.

Achieving high spectral resolution is an important prerequisite for the application of solid-state NMR to biological molecules. Higher spectral resolution allows to resolve a larger number of resonances and leads to higher sensitivity. Among other things, heteronuclear spin decoupling is one of the important factors which determine the resolution of a spectrum. The process of heteronuclear spin decoupling under magic-angle sample spinning is analyzed in detail. Continuous-wave RF irradiation leads only in a zeroth-order approximation to a full decoupling of heteronuclear spin systems in solids under magic-angle spinning (MAS). In a higher-order approximation, a cross-term between the dipolar-coupling tensor and the chemical-shielding tensor is reintroduced, providing a scaled coupling term between the heteronuclear spins. In strongly coupled spin systems this second-order recoupling term is partially averaged out by the proton spin-diffusion process, which leads to exchange-type narrowing of the line by proton spin flips. This process can be described by a spin-diffusion type superoperator, allowing the efficient simulation of strongly coupled spin systems under heteronuclear spin decoupling. Low-power continuous-wave decoupling at fast MAS frequencies offers an alternative to high-power irradiation by reversing the order of the averaging processes. At fast MAS frequencies low-power continuous-wave decoupling leads to significantly narrower lines than high-power continuous-wave decoupling while at the same time reducing the power dissipated in the sample by several orders of magnitude. The best decoupling is achieved by multiple-pulse sequences at high RF fields and under fast MAS. Two such sequences, two-pulse phase-modulated decoupling (TPPM) and X-inverse-X decoupling (XiX), are discussed and their properties analyzed and compared.

Ammonium Chloride↗
PubMed2003

A "magic sandwich" pulse sequence with reduced offset dependence for high-resolution separated local field spectroscopy.

A pulse sequence for high resolution separated local field spectroscopy based on "magic sandwich" elements is demonstrated on a single crystal sample. Simulations and experimental results show that this pulse sequence has a reduced frequency offset dependence compared to PISEMA (polarization inversion spin exchange at the magic angle). As a result, it has a larger effective range of homonuclear decoupling, reduced zero-frequency spectral distortions, and more reliable scale factors for individual resonances. In addition, it is easier to setup on commercial spectrometers.

Computer Simulation↗
PubMed1993

Molecular organization and motions of cholesteryl esters in crystalline and liquid crystalline phases: a 13C and 1H magic angle spinning NMR study.

Cholesteryl esters are a major lipid constituent of plasma lipoproteins and atherosclerotic lesions. Crystalline and liquid crystalline phases of several cholesteryl esters [oleate (C18:1, omega-9), erucate (C22:1, omega-9), hexanoate (C6:0), decanoate (C10:0), undecanoate (C11:0), myristate (C14:0), palmitate (C16:0), and stearate (C18:0)] have been studied by natural abundance 13C NMR with magic angle spinning (MASNMR) at 75 MHz (7.05 T). Spectra obtained with magic angle spinning, high-power proton decoupling, and cross-polarization transfer were highly resolved for crystalline cholesteryl esters. Acyl chain carbons had narrower lines than protonated steroid ring carbons, reflecting differential motions in the crystal (specifically, more rapid motions in the acyl chain than in the steroid ring). Esters which crystallize into the monolayer type II structure, in which all molecules are equivalent, gave rise to a single resonance for each carbon; esters of the monolayer type I and bilayer structures, in which there are two types of nonequivalent molecules in the unit cell, had two resonances (equal intensity and line width) for several carbons, such as the carbonyl and the steroid ring C5 and C6. Spectra for liquid crystalline phases did not show inequivalence of signals for the same carbon and were not enhanced by cross-polarization transfer. These changes are a result of increased molecular motions in the liquid crystals, which average the nonequivalent environments and reduce the dipolar interactions. Cholesteric and smectic liquid crystalline phases were distinguished by the broader C = O, C5, and C6 signals for the cholesteric compared with the smectic phase. In the smectic phase, chemical shifts of corresponding carbons of all cholesteryl esters are similar and are close to those for crystalline esters with a monolayer II structure, which suggests that the smectic phase has structural features resembling the monolayer II crystal structure. 13C MASNMR is thus a powerful approach for examining structure and motions of crystalline and liquid-crystalline cholesteryl esters. 1H MASNMR spectra did not give as detailed information on the molecular level but were unique for each phase and provided a simple and quick method for distinguishing the solid, smectic, cholesteric, and isotropic phases.

Cholesterol Esters↗
PubMed1994

Resolution of individual lipids in mixed phospholipid membranes and specific lipid-cytochrome c interactions by magic-angle spinning solid-state phosphorus-31 NMR.

A model of the inner mitochondrial membrane was constructed with dioleoyphosphatidylcholine (PC), dioleoylphosphatidylethanolamine (PE), and cardiolipin (CL) at a PC:PE:CL molar ratio of 2:2:1, and the interaction of the peripheral membrane protein cytochrome c with this mixed membrane has been investigated by static and magic-angle spinning (MAS) solid-state 31P NMR. The static 31P NMR spectrum of the three-component membrane is a typical broad powder pattern for phospholipids in a bilayer structure, and is a result of three overlapping spectra of each individual phospholipid component in the mixed membrane, with an average effective chemical shift anisotropy of approximately 41 ppm. Using magic-angle spinning NMR methods, three resolved resonances are observed in the narrowed MAS 31P NMR spectrum, each of which has been assigned to each lipid component in the mixed membrane. This allows the investigation of individual phospholipid-protein interactions in multicomponent lipid bilayers. The interaction of cytochrome c with each lipid in a model mitochondrial membrane could now be evaluated. Phosphorus-31 spin-lattice (T1) relaxation times for each lipid phosphate were measured as a function of temperature, in the absence and presence of bound cytochrome c. T1 was not affected for any lipid upon binding of cytochrome c over the temperature range analyzed. However, averaging of the phosphorus-31 chemical shift anisotropy for the cardiolipin component in mixed PC/PE/CL bilayers at lower temperatures ceases to be axially symmetric on binding of cytochrome c, while for PC and PE components the axial symmetry is retained over the temperature interval studied here.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Homonuclear correlation experiments of half-integer quadrupolar nuclei using multiple-quantum techniques spinning at a P(4) magic angle.

A new approach for obtaining structural information in half-integer quadrupolar nuclei is proposed and demonstrated. In this method, the two-dimensional multiple-quantum experiment is performed, spinning at one of the angles at which the fourth order Legendre polynomial vanishes (P4 magic angle). In such an experiment, the dipolar interaction is retained, whereas the second-order quadrupolar broadening is refocused by the MQ-1Q correlation scheme. By adding an exchange period to this pulse scheme, we performed efficient homonuclear correlation experiments in a regular magic angle spinning probe with minor modifications. The experiment is demonstrated on a model compound, and the results are briefly discussed.

Journal Article↗
PubMed1992

[Visagnost--a strip test for in vitro allergy diagnosis in comparison with Magic Lite and Cap-FEIA: I. Total IgE determination].

The diagnosis of allergic airway diseases, especially allergic rhinitis, is based on medical history, clinical examination and further tests. Since the detection of IgE, total IgE in serum has become a major tool in the diagnosis of immediate allergy. Although in-vivo-tests like skin prick test are performed in almost every allergologist's practice, the capability of determining IgE was restricted to special laboratories. As shown for semiquantitative glucose dipsticks, a rapid and easy method has advantages for both patient and doctor. A recently developed dipstick test (Visagnost, in U.S. Quidel allergy screen) for allergy screening now enables every practitioner to determine total IgE levels within less than one hour. For the evaluation of the diagnostic value of this dipstick test, we compared the total IgE levels in the sera of 56 patients with two modern methods (Magic Lite, Ciba-Corning, and Cap-FEIA, Pharmacia). Visagnost is an enzyme-immuno-assay with the solid phase on the dipstick. It can be performed in serum, plasma or whole blood, in this study the test was performed in serum. Magic lite is a combined solid-liquid-phase immuno-assay with a final chemiluminescent reaction, the incubation time is about two hours. Cap-FEIA is a solid phase sandwich ELISA with a fluorescent reaction and an incubation time of at least four hours. Patient's sera were shock-frozen in liquid nitrogen and stored at -80 degrees C until examination. Visagnost gave results in four ranges of minor 20 U/ml, 21-50 U/ml, 51-100 U/ml and more than 100 U/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme-Linked Immunosorbent Assay↗
PubMed2005

Mid-infrared characterization of the NH4 +(H2O)n clusters in the neighborhood of the n=20 "magic" number.

Vibrational predissociation spectra are reported for size-selected NH4+ (H2O)n clusters (n=5-22) in the 2500-3900 cm(-1) region. We concentrate on the sharp free OH stretching bands to deduce the local H-bonding configurations of water molecules on the cluster surface. As in the spectra of the protonated water clusters, the free OH bands in NH4+ (H2O)n evolve from a quartet at small sizes (n<7), to a doublet around n=9, and then to a single peak at the n=20 magic number cluster, before the doublet re-emerges at larger sizes. This spectral simplification at the magic number cluster mirrors that found earlier in the H+(H2O)n clusters. We characterize the likely structures at play for the n=19 and 20 clusters with electronic structure calculations. The most stable form of the n=20 cluster is predicted to have a surface-solvated NH4+ ion that lies considerably lower in energy than isomers with the NH4+ in the interior.

Journal Article↗
PubMed2006

Magic numbers, excitation levels, and other properties of small neutral 4He clusters (N < or = 50).

The ground-state energies and the radial and pair distribution functions of neutral 4He clusters are systematically calculated by the diffusion Monte Carlo method in steps of one 4He atom from 3 to 50 atoms. In addition the chemical potential and the low-lying excitation levels of each cluster are determined with high precision. These calculations reveal that the "magic numbers" observed in experimental 4He cluster size distributions, measured for free jet gas expansions by nondestructive matter-wave diffraction, are not caused by enhanced stabilities. Instead they are explained in terms of an enhanced growth due to sharp peaks in the equilibrium concentrations in the early part of the expansion. These peaks appear at cluster sizes which can just accommodate one more additional stable excitation. The good agreement with experiment provides not only experimental confirmation of the energy level and the chemical potential calculations, but also evidence for a new mechanism which can lead to magic numbers in cluster size distributions. By accounting for the falloff of the radial density distributions at the surface and a size-dependent surface tension, the energy levels are demonstrated to be consistent with a modified Rayleigh model of surface excitations. The compressibility coefficient of these small clusters is found to be one order of magnitude smaller than the bulk compressibility.

Journal Article↗
PubMed2006

Investigation of multiaxis molecular motion by off-magic angle spinning deuteron NMR.

The relatively new deuteron NMR method of off-axis-magic angle spinning (OMAS) has been extended and used to investigate multiaxis rotational jump motion. Floquet theory is developed for simulating deuteron OMAS spectra with multisite jumps at different rates about noncoincident axes, and efficient procedures are presented for computing the sideband line shapes. It is demonstrated experimentally that reproducible adjustment of the angle between the rotor axis and the static magnetic field is feasible with precision approaching +/- 0.01 degrees. This leads to the reintroduction of a scaled, first-order quadrupole coupling that defines a new kinetic window and makes deuteron OMAS much more sensitive than ordinary magic angle spinning to motion on the kilohertz time scale. Temperature-dependent deuteron OMAS line shapes of octanoic acid/urea-d4 inclusion compound have been recorded and fitted, using least-squares procedures, to provide rates of rotation about both CN and CO bonds. The Arrhenius activation parameters for rotation about CN bonds, Ea = 60.4+/-2.4 kJ/mol and ln(A) = 24.9+/-0.3, agree well with previous values determined by selective inversion experiments. However, OMAS yields Ea = 26.3+/-0.4 kJ/mole and ln(A) = 24.9+/-0.3 for whole-body rotation about the CO bond axis in contrast to previous analysis of static quadrupole echo (QE) line shapes which gave Ea = 22.3+/-0.3 kJ/mole and ln(A) = 24.8+/-0.6 for the same sample. The underlying homogeneous linewidths of OMAS spectra are much smaller than those of QE spectra, and this provides higher precision and less systematic error in the determination of rates.

Journal Article↗
PubMed2006

Towards uniform enhancement in solid-state cross polarization magic [corrected] angle spinning NMR: a scheme incorporating cross polarization with rotational resonance.

A recently proposed experimental scheme for achieving uniform cross polarization enhancement of low-gamma nuclear species in solids under magic angle spinning, termed quantitative cross polarization (QUCP) [Hou et al., Chem. Phys. Lett. 421, 356 (2006)], is described, supported with comprehensive theoretical analysis, numerical simulation, and experimental investigation with both uniformly labeled and naturally abundant solids. This method combines cross polarization with dipolar-assisted rotational resonance (DARR) [Takegoshi et al., Chem. Phys. Lett. 344, 631 (2001)] broadband homonuclear recoupling technique to achieve quantitative CP spectra under fast magic angle spinning. In addition to the correct and systematical interpretation on the phenomenon we reported in the previous Letter, a number of general guidelines for performing QUCP experiments are presented in this work. It is firmly established that while the enhancement factor in QUCP depends on the CP contact time, uniform enhancement can nevertheless be realized for all types of carbon group. For natural abundance samples, the polarization transfer rate is generally slower than that in labeled samples, but quasi-equilibrium among dilute spins in the mixing period can always be reached and uniform enhancement can be achieved albeit the DARR irradiation time needed can be much longer. For labeled samples, the time gain of QUCP experiment is almost the same as that of conventional CP. For natural abundance samples, it is generally much better than single-pulse experiment. Various representative systems, including uniformly (13)C-labeled DL-alanine and (13)C, (15)N labeled L-tyrosine, as well as naturally abundant alanine, tyrosine, and monoethyl fumarate, are used to verify the validity of our theoretical analysis and numerical simulation and to demonstrate the utility and advantages of the present approach.

Journal Article↗
PubMed2006

Origins of linewidth in 1H magic-angle spinning NMR.

A detailed study of the factors determining the linewidth (and hence resolution) in 1H solid-state magic-angle spinning NMR is described. Although it has been known from the early days of magic-angle spinning (MAS) that resolution of spectra from abundant nuclear spins, such as 1H, increases approximately linearly with increasing sample rotation rate, the difficulty of describing the dynamics of extended networks of coupled spins has made it difficult to predict a priori the resolution expected for a given sample. Using recently developed, highly efficient methods of numerical simulation, together with experimental measurements on a variety of test systems, we propose a comprehensive picture of 1H resolution under MAS. The "homogeneous" component of the linewidth is shown to depend primarily on the ratio between an effective local coupling strength and the spin rate, modified by geometrical factors which loosely correspond to the "dimensionality" of the coupling network. The remaining "inhomogeneous" component of the natural linewidth is confirmed to have the same properties as in dilute-spin NMR. Variations in the NMR frequency due to chemical shift effects are shown to have minimal impact on 1H resolution. The implications of these results for solid-state NMR experiments involving 1H and other abundant-spin nuclei are discussed.

Journal Article↗
PubMed1979

Acute toxicity of methyl fluorosulfonate (Magic Methyl).

Methyl fluorosulfonate (Magic Methyl), an active methylating agent used by research chemists, was studied for acute oral toxicity, acute inhalation toxicity, ocular irritation, and dermal irritation. This compound is very hazardous and may have been responsible for at least one human death. The results of these studies confirmed that Magic Methyl is markedly toxic by all routes studied and particularly by the inhalation route since the LC50 value for rats was found to be between 5 and 6 ppm.

Administration, Oral↗
PubMed1995

The impact of Magic Johnson's HIV serostatus disclosure on unmarried college students' HIV knowledge, attitudes, risk perception, and sexual behavior.

Unmarried heterosexual college students' HIV knowledge, attitudes, risk perception, and sexual behavior were assessed before and after "Magic" Johnson revealed his HIV-positive serostatus. Students examined after the disclosure showed a small, though statistically significant, increase in scores on HIV knowledge. Analyses did not reveal any other differences between the pre- and postdisclosure samples. Several differences between men's and women's scores were found, however. In addition, participants in both groups demonstrated generally positive attitudes toward HIV and people with HIV disease; rated their risk of future HIV infection as none to minimal; and reported frequently engaging in vaginal, oral, and anal intercourse without the use of condoms. These results suggest that Magic's disclosure did not significantly affect these students' attitudes, risk perception, or sexual behavior and that such students continue to engage in behaviors that may put them at risk for HIV infection.

Adolescent↗
PubMed2002

Ambidexterity and magical ideation.

In a sample of 250 healthy undergraduate students, scores on a scale of magical ideation rose to a peak at the point of ambilaterality on a scale of hand preference, and fell away with increasing right- or left-handedness. This effect mirrors that reported by Crow, Crow, Done, and Leask (1998) who found a dip in academic abilities at the point of ambilaterality, or what they call ''the point of hemispheric indecision''. We relate these findings to genetic theories of laterality in which one allele (RS+) codes for left-cerebral dominance while the other (RS-) leaves laterality to chance. RS-- homozygotes may be susceptible to a lack of dominance, resulting in a disposition to magical ideation and an increased risk of schizophrenia, but also enhanced creativity and lateral thinking.

Journal Article↗
PubMed2003

A quantitative study of magnetization transfer in MAGIC gels.

Magnetization transfer (MT) has been measured quantitatively as a function of radiation dose in MAGIC polymer gels. The MT rates between the free and immobile macromolecular proton pools (kmr and kfm), and the ratio of the sizes of these coupled proton pools (Pm/Pf), were measured by analysing the response to an inversion recovery sequence. While pm/pf increases linearly with dose, the fast MT rate kmf also increases with dose, unlike previous measurements in BANG gels. This dependence of kmf on dose suggests there are additional factors that modify spin exchange in MAGIC gels as irradiation occurs.

Ascorbic Acid↗
PubMed2004

Two-dimensional and quasi-three-dimensional dosimetry of hadron and photon beams with the Magic Cube and the Pixel Ionization Chamber.

Two detectors for fast two-dimensional (2D) and quasi-three-dimensional (quasi-3D) verification of the dose delivered by radiotherapy beams have been developed at University and Istituto Nazionale di Fisica Nucleare (INFN) of Torino. The Magic Cube is a stack of strip-segmented ionization chambers interleaved with water-equivalent slabs. The parallel plate ionization chambers have a sensitive area of 24 x 24 cm2, and consist of 0.375 cm wide and 24 cm long strips. There are a total of 64 strips per chamber. The Magic Cube has been tested with the clinical proton beam at Loma Linda University Medical Centre (LLUMC), and was shown to be capable of fast and precise quasi-3D dose verification. The Pixel Ionization Chamber (PXC) is a detector with pixel anode segmentation. It is a 32 x 32 matrix of 1024 cylindrical ionization cells arranged in a square 24 x 24 cm2 area. Each cell has 0.4 cm diameter and 0.55 cm height, at a pitch of 0.75 cm separates the centre of adjacent cells. The sensitive volume of each single ionization cell is 0.07 cm3. The detectors are read out using custom designed front-end microelectronics and a personal computer-based data acquisition system. The PXC has been used to verify dynamic intensity-modulated radiotherapy for head-and-neck and breast cancers.

Calibration↗
PubMed2025

Decipher RNA isoform combinations from minigene splicing assays and massive parallel sequencing with MAGIC.

SUMMARY: Functional testing of RNA using minigene splicing assays is increasingly being realized to demonstrate the effects of variants on splicing. In complex cases, variant pathogenicity is assessed by Sanger sequencing, which can be time consuming and may be replaced by short read sequencing. Moreover, strategies based on long read sequencing of the amplified minigene construct are promising and allow the isoforms to be fully characterized. We introduce MAGIC, a user-friendly tool that first generates the artificial construction genome files required to then perform alignment, assembly and annotation of the isoforms obtained by either short or long read minigene splicing assay sequencing. AVAILABILITY AND IMPLEMENTATION: MAGIC is available at https://github.com/LBGC-CFB/MAGIC. Zenodo DOI: 10.5281/zenodo.17052752.

High-Throughput Nucleotide Sequencing↗
PubMed2005

MAGIC Tool: integrated microarray data analysis.

SUMMARY: Several programs are now available for analyzing the large datasets arising from cDNA microarray experiments. Most programs are expensive commercial packages or require expensive third party software. Some are freely available to academic researchers, but are limited to one operating system. MicroArray Genome Imaging and Clustering Tool (MAGIC Tool) is an open source program that works on all major platforms, and takes users 'from tiff to gif'. Several unique features of MAGIC Tool are particularly useful for research and teaching. AVAILABILITY: http://www.bio.davidson.edu/MAGIC

Algorithms↗