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  • 1
    Electronic Resource
    Electronic Resource
    Following the decomposition of ryegrass labelled with 13C and 15N in soil by solid-state nuclear magnetic resonance spectroscopy (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 48 (1997), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Investigating the biogeochemistry of plant material decomposition in soil has been restricted by difficulties extracting and identifying organic compounds. In this study the decomposition of 13C- and 15N-labelled Lolium perenne leaves mixed with mineral soil has been investigated over 224 days of incubation under laboratory conditions. Decomposition was followed using short-term rates of CO2 evolution, the amounts of 13C and 15N remaining were determined by mass spectrometry, and 13C and 15N solid-state nuclear magnetic resonance (NMR) spectroscopy was used to characterize chemically the plant material as it decomposed. After 224 days 48% of the added 13C had been lost with a rapid period of C02 evolution over the first 56 days. The fraction of cross-polarization magic angle spinning (CP MAS) 13C NMR spectra represented by O-alkyl-C signal probably in carbohydrates (chemical shift, 60–90 p.p.m.) declined from 60 to 20% of the spectrum (chemical shift, 0–200 p.p.m.) over 224 days. The rate of decline of the total 13C exceeded that of the 60–90 p.p.m. signal during the first 56 days and was similar thereafter. The fraction of the CP MAS 13C NMR spectra represented by the alkyl- and methyl-C (chemical shift, 10–45 p.p.m.) signal increased from 5 to 14% over the first 14 days and was 19% after 224 days. CP MAS 13C NMR of 13C- and 15N-L. perenne contained in 100-μm aperture mesh bags incubated in the soil for 56 days indicated that the remaining material was mainly carbohydrate but there was an increase in the alkyl- and methyl-C associated with the bag's contents. After 224 days incubation of the labelled 13C- and 15N-L. perenne mixed with the soil, 40% of the added N had been lost. Throughout the incubation there was only one signal centred around 100 p.p.m. detectable in the CP MAS 15N NMR spectra. This signal corresponded to amide 15N in peptides and may have been of plant or microbial origin or both. Although there had been substantial interaction between the added 15N and the soil microorganisms, the associated redistribution of 15N from plant to microbial tissues occurred within the amide region. The feasibility of following some of the component processes of plant material decomposition in soil using NMR has been demonstrated in this study and evidence that microbial synthesis contributes to the increase in alkyl- and methyl-C content of soil during decomposition has been represented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1997.tb00562.x
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  • 2
    Electronic Resource
    Electronic Resource
    Organic matter accumulation following fires in a moorland soil chronosequence (1998)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 4 (1998), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Severe fires in 1957 and 1976 removed the vegetation and soil organic matter from the litter layers and organic horizons of soils at two adjacent moorland sites leaving exposed the uppermost mineral horizon of the soil. In the period since, plant recolonization and soil organic matter reaccumulation have occurred to give a chronosequence. Assuming no major changes in the carbon and nitrogen content of the unburned soil since 1957, the rates of accumulation of soil C and N were estimated to be 0.035 kg C m–2 y–1 and 0.001 kg N m–2 y–1 over the first 19 years, and 0.50 kg C m–2 y–1 and 0.023 kg N m–2 y–1 over the period from 19 to 38 years after burning. Solid-state 13C NMR (cross-polarization, magic angle spinning 13C nuclear magnetic resonance spectroscopy) showed that the ratio of alkyl- and methyl-C-to-O-alkyl-C increased with stage of decomposition and in the unburned soil with decreasing particle-size. For the organic matter that had reaccumulated in the 1957-burned soil, the alkyl-C-to-O-alkyl-C ratio of the 〉 2000 μm and 2000–250 μm particle-size fractions were greater than those of the corresponding size fractions from the unburned soil, indicating that the reaccumulated soil organic matter was subject to decomposition but limited fragmentation or comminution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.1998.00153.x
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  • 3
    Electronic Resource
    Electronic Resource
    Organic solute accumulation in osmotically-stressed Enteromorpha intestinalis (1987)
    Springer
    Marine biology 95 (1987), S. 583-592 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of organic solutes in the osmotic adjustment processes of the marine macroalga Enteromorpha intestinalis (L.) Link was investigated in 1986, using fresh samples collected from mid-shore rock pools at Tayport, Fife, Scotland. Natural-abundance 13C nuclear magnetic-resonance spectroscopy revealed β-dimethylsulphoniopropionate (DMSP) to be the only major low molecular weight organic osmolyte present. However, on transfer to a hypersaline medium (300% sea water; 100%=35 S‰), tissue sucrose and proline levels increased markedly, while DMSP remained constant. Recovery of optimal photosynthetic activity and increases in inorganic ion levels occurred over a similar time scale to the changes in sucrose and proline (within 48 h), indicating that these two organic solutes are involved in hyperosmotic adjustment in E. intestinalis while DMSP is not. Freshly-collected plants transferred to 300% sea water medium in the dark showed no significant increases in organic osmolytes. In contrast, starch-enrichment (16 d continuous illumination) led to enhanced synthesis of sucrose and proline in the light and in darkness, but tissue DMSP levels showed no variation throughout. These observations suggest that DMSP is not involved in short-term osmoacclimation in E. intestinalis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393102
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  • 4
    Electronic Resource
    Electronic Resource
    Fates of 13C from enriched glucose and glycine in an organic soil determined by solid-state NMR (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 389-395 
    Details
    ISSN: 1432-0789
    Keywords: Key words Carbon transformations ; Mineralization ; Respiration ; Peat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The transformations of the indigenous 13C and the 13C from either uniformly enriched 13C-D-glucose or 13C-glycine added to an organic soil were followed during a 28-day incubation using cross polarization (CP) magic angle spinning (MAS) 13C nuclear magnetic resonance (NMR) spectroscopy and dipolar dephased (DDP) MAS 13C NMR. The C mineralization was determined from 13C remaining by mass spectrometry and from CO2 evolution by gas chromatography. DDP MAS 13C NMR of the unamended soil indicated a transient increase in molecularly mobile 13C in the alkyl- and methyl-C over 5 days, which may be due to redistribution of 13C in the microbial biomass in response to perturbation. The added glucose-13C remaining declined to 43% after 7 days and 34% after 28 days. After 28 days the amount of added glucose-13C remaining was 6 times greater than the biomass C at the outset, while the microbial activity (CO2 production) was 38% greater, indicating that a significant proportion of added glucose-13C was not in microorganisms. Added glycine-13C declined faster, such that 29% and 8% remained after 7 and 28 days, respectively. After 28 days’ incubation with 13C-glucose, the O-alkyl-C, the acetal- and ketal-C, and the methyl- and alkyl-C resonances in CP MAS 13C NMR spectra were all enhanced compared with the unamended soil. The calculated T1ρH values of the O-alkyl-C and the acetal- and ketal-C resonances were less than those of crystalline glucose, indicating that there was no substantial reservoir of unreacted glucose. After 7 days’ incubation with 13C-glycine, none of the signals in the CP MAS 13C NMR spectra were enhanced when compared with the unamended soil, indicating that the added 13C remaining was distributed in undetectable quantities in a range of functionalities. The calculated T1ρH values indicated that glycine 13C was in O-alkyl-C, acetal- and ketal-C and carbonyl-C. T1ρH values may be more sensitive to changes in the distribution of 13C when 13C content is low. The DDP MAS 13C NMR spectra of both the 13C-glucose- and the 13C-glycine-amended soil showed that the molecularly mobile alkyl- and methyl-C increased compared with the unamended soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050330
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  • 5
    Electronic Resource
    Electronic Resource
    Osmotic adjustment in Spirulina platensis (1985)
    Springer
    Planta 163 (1985), S. 424-429 
    Details
    ISSN: 1432-2048
    Keywords: Cyanobacteria ; Glucosyl-glycerol ; Osmotic adjustment ; Spirulina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The filamentous cyanobacterium Spirulina platensis has been examined for salt tolerance and osmotic adjustment. Salinities up to 150% seawater had little effect on growth yield or photosynthetic O2 evolution; higher salinities were markedly inhibitory. Osmotic adjustment was achieved by the intracellular accumulation of the low-molecular-weight carbohydrate glucosyl-glycerol in response to increased external salinity: in fullstrength (100%) seawater glucosyl-glycerol accounted for approximately 5.0% of the dry weight of the cyanobacterium. Trehalose was also present, particularly in cells at low salt concentration, and in 50% seawater medium accounted for up to 1.0% of the dry weight of the cyanobacterium. For cells grown in 100% seawater the ratio of trehalose to glucosyl-glycerol varied with temperature: at 37°C trehalose comprised 31% (w/w) of the low-molecular-weight carbohydrates while at 20°C only 9% of the total was trehalose. When subjected to hypo-osmotic shock the intracellular concentration of glucosyl-glycerol decreased and this was mirrored by an increase in glycogen. An understanding of the osmotic adjustment of S. platensis has implications both for the mass culturing of this and other strains of Spirulina and possibly also for the quality of the harvested product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395153
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  • 6
    Electronic Resource
    Electronic Resource
    Osmotic adjustment in cyanobacteria from hypersaline environments (1984)
    Springer
    Archives of microbiology 138 (1984), S. 333-337 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Osmotic adjustment ; Osmoregulation ; Quaternary ammonium compounds ; Glycine betaine ; Halotolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intracellular concentrations of the monovalent inorganic cations K+ and Na+, low molecular weight carbohydrates and quaternary ammonium compounds have been determined for 4 strains of cyanobacteria (Aphanothece halophytica, Coccochloris elabens, Dactylococcopsis salina and Synechocystis DUN52) originally isolated from hypersaline habitats (i.e. habitats with a salinity greater than that of seawater) over a range of external salt concentration (from 50% to 400% seawater). Intracellular cation levels (Na+ and K+) were determined to be within the range 80–320 mmol · dm-3 (cell volume), showing only minor changes in response to salinity. Intracellular carbohydrates were found to comprise a negligible component of the intracellular osmotic potential [at 2–19 mmol · dm-3 (cell volume)], throughout the salinity range. Quaternary ammonium compounds, however, were recorded in osmotically significant quantities [up to 1,640 mmol · dm-3 (cell volume)] in these strains, showing major variation in response to salinity. Thus Synechocystis DUN 52 showed an increase in quaternary ammonium compounds in the oder of 1,200 mmol · dm-3 between 50% and 400% seawater medium, accounting for a significant proportion of the change in external osmotic potential. Examination of intact cells and cell extracts using 13C and 1H nuclear magnetic resonance (NMR) spectroscopy confirmed the presence of the quaternary ammonium compound glycine betaine as the major osmoticum in the 4 strains; no other compounds were detected during NMR assays. These results suggest a common mechanism of osmotic adjustment, involving quaternary ammonium compounds, in cyanobacteria from hypersaline environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410900
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  • 7
    Electronic Resource
    Electronic Resource
    Solid state spatially resolved 1H and 19F nuclear magnetic resonance spectroscopy of dental materials by stray-field imaging (1999)
    Springer
    Journal of materials science 10 (1999), S. 369-373 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract As part of a program to evaluate the use of stray-field magnetic resonance microimaging (STRAFI) in dental materials research spatially resolved nuclear magnetic resonance (NMR) for solid dental cements has been investigated. By applying a quadrature echo pulse sequence to a specimen positioned in the stray-field of a NMR spectrometer superconducting magnet the magnetic resonance within a thin slice was obtained. The specimen was stepped through the field in 500 μm increments to record 1 and 19F profiles and T2 values at each point. The specimens were fully cured cylinders made from four types of restorative material (glass ionomer, resin modified glass ionomer, compomer, composite). The values for F19T2 varied with material type and reflected the nature of the matrix structure. For all materials containing 19F in the glass two values were calculated for 19F T2, one short and one long. These were relatively invariant. Solid state magic angle spinning (MAS)-NMR showed that they came from the glass. This suggests that a proportion of the element is relatively mobile (in a glass phase) and the remainder is more tightly bound (in a compound dispersed in the glass). This demonstration, that NMR microimaging of both 1H and 19F in solid dental cements is possible, opens up exciting new possibilities for investigating the distribution of these elements (in particular fluorine) in solid dental materials. ©©1999©Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026429908756
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  • 8
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance chemical shift-selective microimaging of samples of degraded rubber hosepipe and of high-impact polystyrene (1992)
    Springer
    Journal of materials science 11 (1992), S. 222-225 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00741427
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  • 9
    Electronic Resource
    Electronic Resource
    Non-invasive observation of the development of fungal infection in fruit (1992)
    Springer
    Protoplasma 166 (1992), S. 107-109 
    Details
    ISSN: 1615-6102
    Keywords: NMR imaging ; Gradient echo ; Raspberry ; Botrytis cinerea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The progression of infection caused by a fungal pathogen,Botrytis cinerea Pers.: Fr., in a fruit of red raspberry (Rubus idaeus L.) was followed by nuclear magnetic resonance (NMR) microscopic imaging over a 4 day period. It was found that a standard gradient echo sequence discriminated clearly between infected and healthy tissue as mycelium spread across the fruit from a single woundinoculated drupelet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320149
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  • 10
    Electronic Resource
    Electronic Resource
    An NMR microscopic study of grape (Vitis vinifera L.) (1997)
    Springer
    Protoplasma 198 (1997), S. 27-35 
    Details
    ISSN: 1615-6102
    Keywords: Botrytis cinerea ; Vitis vinifera ; Embryonic axis ; Endosperm ; Fungal damage ; Nuclear magnetic resonance imaging ; Seed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mature healthy grape berries and berries wound-inoculated with the fungusBotrytis cinerea were examined by1H NMR microimaging using 2D and 3D spin echo and gradient echo procedures. These NMR images were compared with representations obtained by conventional histology, where possible using the same specimens. 3D imaging datasets from excised seeds were reconstructed by surface rendering and maximum intensity projection to allow interpretation of their internal structure. T2-weighted spin echo images revealed the major features of the pericarp, septum and loculi of whole berries. T1-weighted images were less discriminatory of parenchyma tissues in the fruit but revealed the endosperm in seeds as a chemically shifted feature. A non-invasive study by T1-weighted spin echo NMR imaging of infection byB. cinerea over a 6-day period showed that the disease spread throughout the exocarp but failed to spread in the mesocarp, a result confirmed by histological examination of the same specimen. Surface rendering of 3D datasets of excised seeds revealed the two ruminations of the endosperm and the distal location of the chalaza. The position of the embryonic axis was revealed in T2-weighted maximum intensity projections. This noninvasive study revealed the need to apply a range of imaging techniques and parameters to visualise the structural features of the different parts of the grape berry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282128
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