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At least 613 records · Page 34Linked to original sources
PubMed2003

Carbon-thirteen cross-polarization magic angle spinning nuclear magnetic resonance and Fourier transform infrared studies of thermally modified wood exposed to brown and soft rot fungi.

Thermally modified wood has many technically interesting properties, such as increased dimensional stability, low equilibrium moisture content, and enhanced biological and weather resistance. This paper describes solid-state nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopic studies on the decay of heat-treated and untreated pine (Pinus sylvestris) by brown (Poria placenta) and soft rot fungi. Both techniques combined with multivariate data analysis proved to be powerful tools for the study of wood degradation by fungi. When untreated pine was exposed to brown or soft rot fungi, a drastic decay of the cell wall polysaccharides was observed. Brown rot fungus degraded mainly hemicelluloses while soft rot fungus attacked cellulose more extensively. The aromatic region of 13C cross-polarization magic angle spinning (CPMAS) NMR spectra revealed that the structure of lignin was also altered. New carboxylic structures were formed as a consequence of the decay. The increased biological resistance of pine wood heat-treated at >220 degrees C was observed in the 13C CPMAS NMR and IR spectra.

Basidiomycota↗
PubMedDate not supplied

Of magic wands and kaleidoscopes: fixing problems in the individual market.

Policy analysts sometimes imagine that problems in the individual market can be fixed by waving a magic wand that makes the individual market function more like the group market. However, prior studies reveal that purchasing cooperatives fail to achieve substantial economies of scale; market reforms that reduce the impact of medical underwriting are difficult to implement in the individual market; and it may not be as easy as imagined to induce people to purchase over the Internet or from new or smaller companies that are at higher risk for exiting the market. The best solution is to limit the use of subsidies to certain purchasing options, such as with purchasing cooperatives that abide by rating, issuance, and renewability rules. What is not acceptable is to hand people subsidies and send them to the unstructured and relatively unregulated individual market, nor will it work to give people unhindered choice between two basically different market segments.

Economic Competition↗
PubMed2004

Evaluation of cartilage composition and degradation by high-resolution magic-angle spinning nuclear magnetic resonance.

Rheumatic diseases are accompanied by a progressive destruction of the cartilage layers of the joints. Although the number of patients suffering from rheumatic diseases is steadily increasing, degradation mechanisms of cartilage are not yet understood, and methods for early diagnosis are not available. Although some information on pathogenesis could be obtained from the nuclear magnetic resonance (NMR) spectra of degradation products in the supernatants of cartilage specimens incubated with degradation-causing agents, the most direct information on degradation processes would come from the native cartilage as such. To obtain highly resolved NMR spectra of cartilage, application of the recently developed high-resolution magic-angle spinning (HR-MAS) NMR technique is advisable to obtain small line-widths of individual cartilage resonances. This technique is nowadays commercially available for most NMR spectrometers and has the considerable advantage that the same pulse sequences as in high-resolution NMR can be applied. Except for a MAS spinning equipment, no solid-state NMR hardware is required. Therefore, this method can be easily implemented. Here, we describe the most important requirements that are necessary to record HR-MAS NMR spectra. The capabilities of the HR-MAS technique are discussed for the 1H and 13C NMR spectra of cartilage.

Animals↗
PubMedDate not supplied

Proton magic angle spinning NMR reveals new features in photodynamically treated bacteria.

The bacterium Propionibacterium acnes is light-sensitive due to porphyrin-induced photosensitization. The light sensitivity increases with incubation of 5-aminolevulinic acid, ALA. For the first time, 1H magic angle spinning NMR spectroscopy is used to describe the photoinduced changes in the bacterium after ALA incubation. Successful photosensitization was performed with light-emitting diodes in the blue and red regions (430 and 654 nm, respectively). The irradiation setup, suitable for irradiation of bacterium suspensions in petri dishes is described. For NMR studies blue light diodes with about 90 micromol/m2s were chosen. After blue light irradiation, the endogenous glycine betaine, proline, glutamate and choline levels in P. acnes decreased with increasing irradiation time. For sublethal light doses (50% survival fraction), the endogenous glycine betaine level decreased 80% on average. The corresponding percentages for proline, choline and glutamate were about 40, 25 and 10, respectively. It is hypothesized that the irradiation, inducing porphyrin photosensitization amplified by ALA incubation, leads to elimination of the osmolyte glycine betaine and possibly also proline by so-called regulatory volume decrease (RVD) mechanisms. These mechanisms are known to be active in several prokaryotic and eukaryotic cells when exposed to hypotonic stress. They are also known to be present in several eukaryotic cells during photodynamic therapy (PDT) exposure leading to hypotonoc stress. The findings contribute to the knowledge of the inactivation mechanisms of P. acnes in photosensitization, and could therefore be of interest in the efforts to use PDT as treatment of the acne disease.

Amino Acids↗
PubMed2005

Diffusion of cholesterol and its precursors in lipid membranes studied by 1H pulsed field gradient magic angle spinning NMR.

Cholesterol content is critical for membrane functional properties. We studied the influence of cholesterol and its precursors desmosterol and lanosterol on lateral diffusion of phospholipids and sterols by1H pulsed field gradients (PFG) magic angle spinning (MAS) NMR spectroscopy. The high resolution of resonances afforded by MAS NMR permitted simultaneous diffusion measurements on 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and sterols. The cholesterol diffusion mirrored the DPPC behavior, but rates were slightly higher at all cholesterol concentrations. DPPC and cholesterol diffusion rates decreased and became cholesterol concentration dependent with the onset of liquid-ordered phase formation. The activation energies of diffusion in the coexistence region of liquid-ordered/liquid-disordered phases are higher by about a factor of 2 compared to pure DPPC and to the pure liquid-ordered state formed at higher cholesterol concentrations. We assume that the higher activation energies are a reflection of lipid diffusion across domain boundaries. In lanosterol- and desmosterol-containing membranes, the DPPC and sterol diffusion coefficients are somewhat higher. Whereas the desmosterol rates are only slightly higher than those of DPPC, the lanosterol diffusion rates significantly exceed DPPC rates, indicating a weaker interaction between DPPC and lanosterol.

1,2-Dipalmitoylphosphatidylcholine↗
PubMedDate not supplied

Pressure-induced isomerization of retinal on bacteriorhodopsin as disclosed by fast magic angle spinning NMR.

Bacteriorhodopsin (bR) is a retinal protein in purple membrane of Halobacterium salinarum, which functions as a light-driven proton pump. We have detected pressure-induced isomerization of retinal in bR by analyzing 15N cross polarization-magic angle spinning (CP-MAS) NMR spectra of [zeta-15N]Lys-labeled bR. In the 15N-NMR spectra, both all-trans and 13-cis retinal configurations have been observed in the Lys N(zeta) in protonated Schiff base at 148.0 and 155.0 ppm, respectively, at the MAS frequency of 4 kHz in the dark. When the MAS frequency was increased up to 12 kHz corresponding to the sample pressure of 63 bar, the 15N-NMR signals of [zeta-15N]Lys in Schiff base of retinal were broadened. On the other hand, other [zeta-15N]Lys did not show broadening. Subsequently, the increased signal intensity of [zeta-15N]Lys in Schiff base of 13-cis retinal at 155.0 ppm was observed when the MAS frequency was decreased from 12 to 4 kHz. These results showed that the equilibrium constant of [all-trans-bR]/[13-cis-bR] in retinal decreased by the pressure of 63 bar. It was also revealed that the structural changes induced by the pressure occurred in the vicinity of retinal. Therefore, microscopically, hydrogen-bond network around retinal would be disrupted or distorted by a constantly applied pressure. It is, therefore, clearly demonstrated that increased pressure induced by fast MAS frequencies generated isomerization of retinal from all-trans to 13-cis state in the membrane protein bR.

Bacteriorhodopsins↗
PubMedDate not supplied

Chemical and carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance characterization of logyard fines from British Columbia.

Phasing out beehive burners and rising costs for landfilling have increased the need to widen options for utilization of the smaller size fractions of woody wastes generated during log handling and sawmilling in British Columbia. We characterized several size classes of logyard fines up to 16 mm sampled from coastal and interior operations. Total C, total N, ash, and condensed tannin concentrations were consistent with properties derived largely from wood, with varying proportions of bark and mixing with mineral soil. Especially for < 3-mm fractions, the latter resulted in high ash contents that would make them unsuitable for fuel. Solid-state 13C cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra were consistent with the chemical data, with high O-alkyl intensity and similarity to naturally occurring woody forest floor; no samples were high in aromatic or phenolic C. Aqueous extracts of two < 16-mm fines, which accounted for only a small proportion of the total C, were enriched in alkyl C and had low or undetectable tannins. Application to forest sites might cause short-term immobilization of N, but also might include possible longer-term benefits from reduction of N loss after harvesting and restoration of soil organic matter in degraded sites.

British Columbia↗
PubMed2004

MaGIC: a program to generate targeted marker sets for genome-wide association studies.

High-throughput genotyping technologies such as DNA pooling and DNA microarrays mean that whole-genome screens are now practical for complex disease gene discovery using association studies. Because it is currently impractical to use all available markers, a subset is typically selected on the basis of required saturation density. Restricting markers to those within annotated genomic features of interest (e.g., genes or exons) or within feature-rich regions, reduces workload and cost while retaining much information. We have designed a program (MaGIC) that exploits genome assembly data to create lists of markers correlated with other genomic features. Marker lists are generated at a user-defined spacing and can target features with a user-defined density. Maps are in base pairs or linkage disequilibrium units (LDUs) as derived from the International HapMap data, which is useful for association studies and fine-mapping. Markers may be selected on the basis of heterozygosity and source database, and single nucleotide polymorphism (SNP) markers may additionally be selected on the basis of validation status. The import function means the method can be used for any genomic features such as housekeeping genes, long interspersed elements (LINES), or Alu repeats in humans, and is also functional for other species with equivalent data. The program and source code is freely available at http://cogent.iop.kcl.ac.uk/MaGIC.cogx.

Algorithms↗
PubMed2001

High resolution magic angle spinning NMR in combinatorial chemistry.

Solid phase organic chemistry coupled with combinatorial methods promises to increase dramatically the diversity and number of small molecules available for medical and biological applications. However, optimizing the reaction conditions can be a time consuming step, especially since analytical tools to monitor reaction progress and detect impurities for solid phase chemistry are less developed than for solution chemistry. The use of high resolution magic angle spinning (HRMAS) NMR is described here as such an analytical tool. Whereas initial applications of molecular identification using deuterated organic solvents to swell the resins presented a significant gain in time over the cleave-and-analysis methods, the introduction of a differential diffusion filter has made immediate recording of spectra possible without any sample treatment. The applications of HRMAS NMR to different solid supports that are used in combinatorial chemistry will be described in terms of rapidity, robustness and sensitivity.

Chemistry, Organic↗
PubMed2003

High resolution magic angle spinning NMR for analyzing small molecules attached to solid support.

Solid phase synthesis has become a routine technique in combinatorial chemistry. The need in analytical methods to characterize nondestructively resin bound molecules has been fulfilled by the introduction of High Resolution Magic Angle Spinning (HR MAS) NMR of solvent swollen beads. HR MAS NMR can give solution like proton NMR spectra and one- and two-dimensional NMR techniques are amenable, allowing detailed structure analysis. Recent developments are the application of a diffusion filter to suppress solvent signals and dipolar recoupling techniques to gain spatial information. HR MAS NMR has been applied to monitor reactions and elucidate reaction products.

Chemistry, Pharmaceutical↗
PubMed2001

Colloidal calcium phosphates in casein micelles studied by slow-speed-spinning 31P magic angle spinning solid-state nuclear magnetic resonance.

The composition of bovine casein micelles was analyzed by 31P magic angle spinning solid-state nuclear magnetic resonance spectroscopy. By looking at isotropic and anisotropic 31P chemical shift parameters, resonance line shapes, the combination of single-pulse and 1H to 31P cross-polarization spectra, and comparison with spectra for various model compounds combined with multiple-component simulation and iterative fitting procedures, we were able to identify and quantify a variety of inorganic and organic phosphates in the micelles. These include phosphates from mobile and immobile inorganic hydroxyapatite-type phosphates as well as phosphates from kappa-casein and the Ca2+-binding phosphoserines from alphas1-, alphas2-, and beta-casein. This information is discussed in relation to previous knowledge and various models for the colloid formation.

Animals↗
PubMed2003

[Discrimination of psychoactive fungi (commonly called "magic mushrooms") based on the DNA sequence of the internal transcribed spacer region].

'Magic mushrooms' (MMs) are psychoactive fungi containing the hallucinogenic compounds, psilocin (1) and psilocybin (2). Since June 6, 2002, these fungi have been regulated by the Narcotics and Psychotropics Control Law in Japan. Because there are many kinds of MMs and they are sold even as dry powders in local markets, it is very difficult to identify the original species of the MMs by morphological observation. Therefore, we investigated the internal transcribed spacer (ITS) region in the ribosomal RNA gene of MMs obtained in Japanese markets to classify them by a genetic approach. Based on the size and nucleotide sequence of the ITS region amplified by PCR, tested MMs were classified into 6 groups. Furthermore, a comparison of the DNA sequences of the MMs with those of authentic samples or with those found in the databases (GenBank, EMBL and DDBJ) made it possible to identify the species of tested MMs. Analysis by LC revealed that psilocin (1) was contained at the highest level in Panaeolus cyanescens among the MMs, but was absent in the Amanita species.

Agaricales↗
PubMed1984

Hospital space planning: what happened to all the magic numbers?

"Magic numbers" and user "wish lists" have traditionally been used to determine space needs in health care institutions. Today, however, combining functional and space planning to yield a space program that integrates with the facility's long-range strategic plan can be accomplished through a user needs approach. These three approaches are discussed in light of their positive and negative aspects and their contributions to the planning process. In particular, a methodology for examining a department's potential "space generators" is provided. Along with this methodology is the reasoning behind beginning the detailed analysis early in the planning process.

Health Services Needs and Demand↗
PubMed1999

Archimedean Synthesis and Magic Numbers: "Sizing" Giant Molybdenum-Oxide-Based Molecular Spheres of the Keplerate Type.

Pythagorean harmony can be found in the spherical polyoxometalate clusters described here (see illustration for an example of a structure), since there are interesting relationships between the so-called magic numbers (12, 32, 42, 72, 132) relevant for spherical viruses and the number of the building blocks in the cluster. The size of these Keplerate clusters can be tailored by varying the type of connections between the pentagons by means of different spacers.

Journal Article↗
PubMed2000

The magic bullet?

The promise of gene therapy has yet to be realised and a recent death has cast a long shadow over clinical trials. Will gene therapy develop into the magic bullet of the 21st Century or is it a technology too complicated to succeed?

Clinical Trials as Topic↗
PubMed2001

Improving the numerical stability of the MAGIC model.

MAGIC is one of the most widely used models for forecasting long-term acidification. The model's code, however, has been experiencing numerical instability, though this might not be widely known to the public users. The major instability comes from the analytical solution to two cubic equations for calculating SO4(2-) concentration and the exchangeable fraction of Al on the soils. The mathematical algorithm for calculating the concentration of SO4(2-) from a quadratic equation is also found unstable. This paper is aimed at improving the instability above through proved numerical algorithms.

Adsorption↗
PubMed2002

Melanoma tumors acquire a new phospholipid metabolism phenotype under cystemustine as revealed by high-resolution magic angle spinning proton nuclear magnetic resonance spectroscopy of intact tumor samples.

N'-[2-chloroethyl]-N[2-(methylsulfonyl) ethyl]-N'-nitrosourea (cystemustine),a chloroethylnitrosourea antineoplastic drug, provokes cellular proliferation inhibition and redifferentiation, but there was no cell death in B16 melanoma tumors. Because the phospholipid (Plp) metabolism is tightly involved in tumor growth regulation and tumor cell survival, we tested the hypothesis that melanoma tumors undergo adaptive Plp metabolism changes to survive treatment. Measurements of Plp derivatives were performed using a novel proton nuclear magnetic resonance Spectroscopy application using magic angle spinning on intact tumor tissue samples. Phosphatidylcholine levels were obtained from one-dimensional spectra, and relative levels of choline- and ethanolamine-containing compounds were derived from two-dimensional spectra (total correlation spectroscopy sequence). Two major findings emerged from this study: (a) during tumor growth inhibition, there was a transient accumulation of choline, glycerophosphocholine, and glycerophosphoethanolamine and a sustained increase in phosphocholine and phosphoethanolamine, whereas phosphatidylcholine levels remained unchanged; and (b) during tumor growth recovery, only phosphocholine and phosphoethanolamine remained elevated. Therefore, cystemustine-treated B16 melanoma tumors acquire a new Plp metabolism phenotype, a mechanism that could participate in tumor cell redifferentiation and/or survival.

Animals↗
PubMedDate not supplied

Characterization of high-tannin fractions from humus by carbon-13 cross-polarization and magic-angle spinning nuclear magnetic resonance.

Condensed tannins can be found in various parts of many plants. Unlike lignin there has been little study of their fate as they enter the soil organic matter pool and their influence on nutrient cycling, especially through their protein-binding properties. We extracted and characterized tannin-rich fractions from humus collected in 1998 from a black spruce [Picea mariana (Mill.) Britton et al.] forest in Canada where a previous study (1995) showed high levels (3.8% by weight) of condensed tannins. A reference tannin purified from black spruce needles was characterized by solution 13C nuclear magnetic resonance (NMR) as a pure procyanidin with mainly cis stereochemistry and an average chain length of four to five units. The colorimetric proanthocyanidin (PA) assay, standardized against the black spruce tannin, showed that both extracted humus fractions had higher tannin contents than the original humus (2.84% and 11.17% vs. 0.08%), and accounted for 32% of humus tannin content. Consistent with the results from the chemical assay, the aqueous fraction showed higher tannin signals in the 13C cross-polarization and magic-angle spinning (CPMAS) NMR spectrum than the emulsified one. As both tannin-rich humus fractions were depleted in N and high in structures derived from lignin and cutin, they did not have properties consistent with recaldtrant tannin-protein complexes proposed as a mechanism for N sequestration in humus. Further studies are needed to establish if tannin-protein structures in humus can be detected or isolated, or if tannins contribute to forest management problems observed in these ecosystems by binding to and slowing down the activity of soil enzymes.

Astringents↗