Polyphosphate

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Susan Belfry - One of the best experts on this subject based on the ideXlab platform.

  • Polyphosphate and siliceous granules in the macroscopic gametophytes of the red alga porphyra purpurea bangiophyceae rhodophyta
    Botanica Marina, 2004
    Co-Authors: Thierry Chopin, Tania Morais, Ellen Belyea, Susan Belfry
    Abstract:

    Phosphorylated fractions in tissues of starved and fresh plants of Porphyra purpurea, a representative of the Bangiophyceae, were analyzed over a 48 h incubation period in pulse-enriched seawater (15 mM phosphorus and 25 mM nitrogen). Compared to Chondrus crispus, a representative of the structurally and reproductively more complex Florideophyceae, P. purpurea takes up phosphorus much more actively, with a higher turnover rate, in which the orthophosphate fraction is predominant and acid-soluble and acid-insoluble Polyphosphates are less significant as storage pools. Presence of cytoplasmic acid-insoluble Polyphosphate granules was confirmed by transmission electron microscopy and energy dispersive X-ray microanalysis. The granules in P. purpurea were much smaller (20–110 nm in diameter) than those in C. crispus (around 1 mm, but some larger than 2 mm). Larger granules (290–310 nm) were observed in P. purpurea. They were more uniformly electron-opaque, without the reticulated/globular appearance of typical Polyphosphate granules. Energy dispersive X-ray microanalysis demonstrated they were siliceous granules. To our knowledge, this is the first report in algae of such structures whose occurrence and metabolic role remain enigmatic.

  • Polyphosphate and siliceous granules in the gametophytes of the red alga porphyra purpurea bangiophyceae
    Journal of Phycology, 2000
    Co-Authors: Thierry Chopin, Tania Morais, Ellen Belyea, Susan Belfry
    Abstract:

    Variations of the different phosphorylated fractions in tissues of starved and fresh plants of Porphyra purpurea, a representative of the Bangiophyceae, over a 72 hour incubation period in pulse-enriched seawater (15 μM phosphorus and 25 μM nitrogen) were analyzed and compared to those in Chondrus crispus, a representative of the Florideophyceae, considered the more advanced of the two classes of the Rhodophyta. Differences point towards P. purpurea being a much more metabolically active phosphorus “pump” than C. crispus, with a higher phosphorus turnover rate, in which the orthophosphate fraction is predominant and acid-soluble and acid-insoluble Polyphosphates are not as significant storage pools. Confirmation of the presence of acid-insoluble Polyphosphates, detected by chemical analyses, in the form of cytoplasmic granules was obtained by transmission electron microscopy and energy dispersive X-ray microanalysis. The granules in P. purpurea were, however, much smaller (20 to 110 nm in diameter) than those in C. crispus (around 1 μm, but some larger than 2 μm in diameter). Larger granules (290 to 310 nm in diameter) were also observed. Their surface was more uniformly electron-opaque without the reticulated or globular appearance of typical Polyphosphate granules. Energy dispersive X-ray microanalysis demonstrated that they were siliceous granules. To our knowledge, this is the first report in algae of such structures whose occurrence and metabolic role remain enigmatic.

Thierry Chopin - One of the best experts on this subject based on the ideXlab platform.

  • Polyphosphate and siliceous granules in the macroscopic gametophytes of the red alga porphyra purpurea bangiophyceae rhodophyta
    Botanica Marina, 2004
    Co-Authors: Thierry Chopin, Tania Morais, Ellen Belyea, Susan Belfry
    Abstract:

    Phosphorylated fractions in tissues of starved and fresh plants of Porphyra purpurea, a representative of the Bangiophyceae, were analyzed over a 48 h incubation period in pulse-enriched seawater (15 mM phosphorus and 25 mM nitrogen). Compared to Chondrus crispus, a representative of the structurally and reproductively more complex Florideophyceae, P. purpurea takes up phosphorus much more actively, with a higher turnover rate, in which the orthophosphate fraction is predominant and acid-soluble and acid-insoluble Polyphosphates are less significant as storage pools. Presence of cytoplasmic acid-insoluble Polyphosphate granules was confirmed by transmission electron microscopy and energy dispersive X-ray microanalysis. The granules in P. purpurea were much smaller (20–110 nm in diameter) than those in C. crispus (around 1 mm, but some larger than 2 mm). Larger granules (290–310 nm) were observed in P. purpurea. They were more uniformly electron-opaque, without the reticulated/globular appearance of typical Polyphosphate granules. Energy dispersive X-ray microanalysis demonstrated they were siliceous granules. To our knowledge, this is the first report in algae of such structures whose occurrence and metabolic role remain enigmatic.

  • Polyphosphate and siliceous granules in the gametophytes of the red alga porphyra purpurea bangiophyceae
    Journal of Phycology, 2000
    Co-Authors: Thierry Chopin, Tania Morais, Ellen Belyea, Susan Belfry
    Abstract:

    Variations of the different phosphorylated fractions in tissues of starved and fresh plants of Porphyra purpurea, a representative of the Bangiophyceae, over a 72 hour incubation period in pulse-enriched seawater (15 μM phosphorus and 25 μM nitrogen) were analyzed and compared to those in Chondrus crispus, a representative of the Florideophyceae, considered the more advanced of the two classes of the Rhodophyta. Differences point towards P. purpurea being a much more metabolically active phosphorus “pump” than C. crispus, with a higher phosphorus turnover rate, in which the orthophosphate fraction is predominant and acid-soluble and acid-insoluble Polyphosphates are not as significant storage pools. Confirmation of the presence of acid-insoluble Polyphosphates, detected by chemical analyses, in the form of cytoplasmic granules was obtained by transmission electron microscopy and energy dispersive X-ray microanalysis. The granules in P. purpurea were, however, much smaller (20 to 110 nm in diameter) than those in C. crispus (around 1 μm, but some larger than 2 μm in diameter). Larger granules (290 to 310 nm in diameter) were also observed. Their surface was more uniformly electron-opaque without the reticulated or globular appearance of typical Polyphosphate granules. Energy dispersive X-ray microanalysis demonstrated that they were siliceous granules. To our knowledge, this is the first report in algae of such structures whose occurrence and metabolic role remain enigmatic.

Tania Morais - One of the best experts on this subject based on the ideXlab platform.

  • Polyphosphate and siliceous granules in the macroscopic gametophytes of the red alga porphyra purpurea bangiophyceae rhodophyta
    Botanica Marina, 2004
    Co-Authors: Thierry Chopin, Tania Morais, Ellen Belyea, Susan Belfry
    Abstract:

    Phosphorylated fractions in tissues of starved and fresh plants of Porphyra purpurea, a representative of the Bangiophyceae, were analyzed over a 48 h incubation period in pulse-enriched seawater (15 mM phosphorus and 25 mM nitrogen). Compared to Chondrus crispus, a representative of the structurally and reproductively more complex Florideophyceae, P. purpurea takes up phosphorus much more actively, with a higher turnover rate, in which the orthophosphate fraction is predominant and acid-soluble and acid-insoluble Polyphosphates are less significant as storage pools. Presence of cytoplasmic acid-insoluble Polyphosphate granules was confirmed by transmission electron microscopy and energy dispersive X-ray microanalysis. The granules in P. purpurea were much smaller (20–110 nm in diameter) than those in C. crispus (around 1 mm, but some larger than 2 mm). Larger granules (290–310 nm) were observed in P. purpurea. They were more uniformly electron-opaque, without the reticulated/globular appearance of typical Polyphosphate granules. Energy dispersive X-ray microanalysis demonstrated they were siliceous granules. To our knowledge, this is the first report in algae of such structures whose occurrence and metabolic role remain enigmatic.

  • Polyphosphate and siliceous granules in the gametophytes of the red alga porphyra purpurea bangiophyceae
    Journal of Phycology, 2000
    Co-Authors: Thierry Chopin, Tania Morais, Ellen Belyea, Susan Belfry
    Abstract:

    Variations of the different phosphorylated fractions in tissues of starved and fresh plants of Porphyra purpurea, a representative of the Bangiophyceae, over a 72 hour incubation period in pulse-enriched seawater (15 μM phosphorus and 25 μM nitrogen) were analyzed and compared to those in Chondrus crispus, a representative of the Florideophyceae, considered the more advanced of the two classes of the Rhodophyta. Differences point towards P. purpurea being a much more metabolically active phosphorus “pump” than C. crispus, with a higher phosphorus turnover rate, in which the orthophosphate fraction is predominant and acid-soluble and acid-insoluble Polyphosphates are not as significant storage pools. Confirmation of the presence of acid-insoluble Polyphosphates, detected by chemical analyses, in the form of cytoplasmic granules was obtained by transmission electron microscopy and energy dispersive X-ray microanalysis. The granules in P. purpurea were, however, much smaller (20 to 110 nm in diameter) than those in C. crispus (around 1 μm, but some larger than 2 μm in diameter). Larger granules (290 to 310 nm in diameter) were also observed. Their surface was more uniformly electron-opaque without the reticulated or globular appearance of typical Polyphosphate granules. Energy dispersive X-ray microanalysis demonstrated that they were siliceous granules. To our knowledge, this is the first report in algae of such structures whose occurrence and metabolic role remain enigmatic.

Ellen Belyea - One of the best experts on this subject based on the ideXlab platform.

  • Polyphosphate and siliceous granules in the macroscopic gametophytes of the red alga porphyra purpurea bangiophyceae rhodophyta
    Botanica Marina, 2004
    Co-Authors: Thierry Chopin, Tania Morais, Ellen Belyea, Susan Belfry
    Abstract:

    Phosphorylated fractions in tissues of starved and fresh plants of Porphyra purpurea, a representative of the Bangiophyceae, were analyzed over a 48 h incubation period in pulse-enriched seawater (15 mM phosphorus and 25 mM nitrogen). Compared to Chondrus crispus, a representative of the structurally and reproductively more complex Florideophyceae, P. purpurea takes up phosphorus much more actively, with a higher turnover rate, in which the orthophosphate fraction is predominant and acid-soluble and acid-insoluble Polyphosphates are less significant as storage pools. Presence of cytoplasmic acid-insoluble Polyphosphate granules was confirmed by transmission electron microscopy and energy dispersive X-ray microanalysis. The granules in P. purpurea were much smaller (20–110 nm in diameter) than those in C. crispus (around 1 mm, but some larger than 2 mm). Larger granules (290–310 nm) were observed in P. purpurea. They were more uniformly electron-opaque, without the reticulated/globular appearance of typical Polyphosphate granules. Energy dispersive X-ray microanalysis demonstrated they were siliceous granules. To our knowledge, this is the first report in algae of such structures whose occurrence and metabolic role remain enigmatic.

  • Polyphosphate and siliceous granules in the gametophytes of the red alga porphyra purpurea bangiophyceae
    Journal of Phycology, 2000
    Co-Authors: Thierry Chopin, Tania Morais, Ellen Belyea, Susan Belfry
    Abstract:

    Variations of the different phosphorylated fractions in tissues of starved and fresh plants of Porphyra purpurea, a representative of the Bangiophyceae, over a 72 hour incubation period in pulse-enriched seawater (15 μM phosphorus and 25 μM nitrogen) were analyzed and compared to those in Chondrus crispus, a representative of the Florideophyceae, considered the more advanced of the two classes of the Rhodophyta. Differences point towards P. purpurea being a much more metabolically active phosphorus “pump” than C. crispus, with a higher phosphorus turnover rate, in which the orthophosphate fraction is predominant and acid-soluble and acid-insoluble Polyphosphates are not as significant storage pools. Confirmation of the presence of acid-insoluble Polyphosphates, detected by chemical analyses, in the form of cytoplasmic granules was obtained by transmission electron microscopy and energy dispersive X-ray microanalysis. The granules in P. purpurea were, however, much smaller (20 to 110 nm in diameter) than those in C. crispus (around 1 μm, but some larger than 2 μm in diameter). Larger granules (290 to 310 nm in diameter) were also observed. Their surface was more uniformly electron-opaque without the reticulated or globular appearance of typical Polyphosphate granules. Energy dispersive X-ray microanalysis demonstrated that they were siliceous granules. To our knowledge, this is the first report in algae of such structures whose occurrence and metabolic role remain enigmatic.

Masoud Kasrai - One of the best experts on this subject based on the ideXlab platform.

  • The role of the cation in antiwear films formed from ZDDP on 52100 steel
    Tribology Letters, 2006
    Co-Authors: Gavin Pereira, Masoud Kasrai, Andreas Lachenwitzer, David Munoz-paniagua, Peter R. Norton, Mike Abrecht, P.u.p.a. Gilbert
    Abstract:

    Phosphorus L-edge and oxygen K-edge X-ray PhotoEmission Electron Microscopy (XPEEM) have been used to characterize the chemical nature of the cation present in tribochemical films via comparison with model Fe^2+ and Zn^2+ compounds. The results are contrasted to the P L-edge, P K-edge and S K-edge XANES data. The findings suggest that antiwear pads containing long chain zinc Polyphosphate glass are formed at the points of asperity contact, and a thin, short chain zinc Polyphosphate film is formed where no asperity contact is made. SEM/EDX measurements helped to elucidate the distribution of the elements, and strong spatial correlations were observed between P, O, Zn and S in the pads, indicating that they are composed mostly of zinc Polyphosphates, especially near the surface. The zinc Polyphosphate antiwear pads are characterized by a much lower modulus than that observed on the thin film regions, the latter being characteristic of the substrate steel.

  • chemomechanical properties of antiwear films using x ray absorption microscopy and nanoindentation techniques
    Tribology Letters, 2004
    Co-Authors: Mark A Nicholls, P R Norton, Gelsomina De Stasio, Masoud Kasrai, B. H. Frazer, Michael G Bancroft, Lisa M Wiese
    Abstract:

    The first chemomechanical comparison between an antiwear film formed from a solution containing zinc dialkyl-dithiophophates (ZDDPs) to a solution containing ZDDP plus a detergent (ZDDPdet) has been performed. X-ray absorption near-edge structure (XANES) analysis has shown a difference in the type of Polyphosphate between each film. The ZDDPdet film has been found to contain short-chain Polyphosphates throughout. X-ray photoelectron emission microscopy (X-PEEM) has provided detailed spatially resolved microchemistry of the films. The large pads in the ZDDP antiwear film have long-chain Polyphosphates at the surface and shorter-chain Polyphosphates are found in the lower lying regions. The spatially resolved chemistry of the ZDDPdet film was found to be short-chain calcium phosphate throughout. Fiducial marks allowed for the re-location of the same areas with an imaging nanoindenter. This allowed the nanoscale mechanical properties, of selected antiwear pads, to be measured on the same length scale. The indentation modulus of the ZDDP antiwear pads were found to be heterogeneous, ~120 GPa at the center and ~90 GPa at the edges. The ZDDPdet antiwear pads were found to be more uniform and have a similar indentation modulus of ~90 GPa. A theory explaining this measured difference, which is based on the probing depths of all techniques used, sheds new insight into the structure and mechanical response of ZDDP antiwear films.

  • chemistry of antiwear films from ashless thiophosphate oil additives
    Tribology Letters, 2004
    Co-Authors: M N Najman, Masoud Kasrai, G M Bancroft
    Abstract:

    X-ray absorption near-edge structure (XANES) spectroscopy has been combined with atomic force microscopy (AFM) to investigate the interaction of ashless thiophosphate oil additives on steel. Both mono- and dithiophosphates were studied and compared with one another in terms of chemistry and tribological performance. XANES revealed that, thermally, all three thiophosphate additives behaved similarly with steel to form a thermal film at temperatures of 150 °C. The thermal films all consisted of a layered structure comprised of Fe(II) Polyphosphate and FeSO4 in the bulk and iron Polyphosphate of various chain length towards the surface. Tribochemical films generated at 5min, 1 h, and 6 h of wear testing revealed that for all three additives, the phosphorus chemistry of an antiwear (AW) film remained chemically consistent throughout all rubbing times. This suggests that the phosphorus chemistry of the AW film is determined in the initial stages of tribofilm formation. The iron Polyphosphate chain length remained uniform throughout the AW film with short chain iron Polyphosphates found both at the surface and in the bulk of the films. Mild AW conditions produced several different forms of sulfur at the various stages during wear testing. S K-edge XANES spectra for the 5-min tribofilms (both total electron yield and fluorescence yield) showed oxidized and reduced forms of sulfur throughout the films for all three additives. Over extended periods of rubbing (6 h), the more thermodynamically stable product, FeSO4, was produced and became the major constituent of the tribofilms formed. Iron sulfate was present throughout the films with only traces of reduced sulfur present.

  • Antiwear film formation of neutral and basic ZDDP: influence of the reaction temperature and of the concentration
    Tribology Letters, 2000
    Co-Authors: K. Varlot, Masoud Kasrai, G M Bancroft, J.m. Martin, B. Vacher, E.s. Yamaguchi, P. Ray Ryason
    Abstract:

    Both synchrotron radiation-based techniques (XANES) and transmission electron microscopy (EDX, EELS) are used to draw a comparison of antiwear and thermal films generated from neutral and basic ZDDP salts. Antiwear films were created in a pin-on-flat wear machine and the wear debris was collected. The analysis of the tribofilms did not show any substantial difference between neutral and basic ZDDPs. The wear scar diameter and the P and S chemical environment in the tribofilm were very similar. The chemical analysis of the wear debris revealed differences in the chemical composition. Wear debris from basic ZDDP seems to be mostly composed either of unreacted ZDDP or of a linkage isomer of ZDDP (LI-ZDDP), and zinc Polyphosphate; whereas the wear debris as far as neutral ZDDP is concerned seems to be exclusively composed of zinc Polyphosphate (and sulphur species). More iron was also detected in the wear debris with basic ZDDP – possibly an indication of the iron content of the tribofilm. Differences in chemical structure could also be detected in the thermal films. While neutral ZDDP reacted with the surface to form Polyphosphates at 150°C, the same reaction products were obtained with basic ZDDP at 175°C. The concentration of ZDDP in oil is thought to be the main parameter to explain the differences in the thermal film formation.

  • application of soft x ray absorption spectroscopy in chemical characterization of antiwear films generated by zddp part i the effects of physical parameters
    Wear, 1997
    Co-Authors: Masoud Kasrai, Marina Suominen L Fuller, Michael G Bancroft, K Fyfe
    Abstract:

    X-ray absorption near edge structure (XANES) spectroscopy has been used to study the chemical nature of the antiwear films generated on steel surfaces using zinc dialkyldithiophosphates (ZDDPs). The spectra were recorded using total electron yield (TEY) and fluorescence yield (FY) to investigate the chemical nature of P, S, Ca, O and Fe on the surface and in the bulk, respectively. In the first part of this study, the effects of physical parameters on the composition and mechanism of antiwear film formation is discussed. It has been found that lower concentration of ZDDP, higher temperature and higher load all increase the rate of ZDDP decomposition; and longer rubbing time, higher concentration of ZDDP, moderate temperature, higher load and smooth surfaces help to form long chain Polyphosphates. The sulphur in the film in most of the cases is in the reduced form. The presence of sulphate in very short rubbing times or high temperatures has also been detected. When the spectra from the TEY mode and FY mode were compared, a layered structure was found in most of the films. In these films, there is a longer chain Polyphosphate on the topmost surface and a shorter chain Polyphosphate in the bulk. At short rubbing times and low temperature, unchanged ZDDP is also present in the film. Depth profiling using X-ray photoelectron spectroscopy showed that the antiwear film formed in 30 min is thinner compared with a 12 hour film. Based on the above information, a new mechanism for antiwear film formation is proposed.