title: Interactions of calcium and other metal ions with caldolysin, the thermostable proteinase from Thermus aquaticus strain T351.

authors: Khoo, T.C.

subjects: biology

abstract: Caldolysin, the extracellular proteinase from the extreme thermophile Thermus aquaticus strain T351, is stabilized by Ca2+. A variety of metal ions were able to substitute for Ca2+. Most were unable to confer as much stability as Ca2+, with the exception of the lanthanide ions, which increased the half-life at 95 degrees C from 1 h to more than 4 h. Results from a variety of separation methods indicated that caldolysin binds 6 Ca2+ ions/molecule of enzyme. The presence of non-linear Ca2+ titration plots, and the removal of 4 Ca2+ ions/molecule by treatment with a cationic ion-exchange gel suggested that caldolysin possesses at least two different types of Ca2+-binding sites, with different affinities. Average binding constants of the two types of binding sites were 2.8 X 10(4)M-1 (for the low-affinity sites) and 7.5 X 10(5) M-1 (for the high-affinity sites). The total Ca2+-binding free energy for caldolysin was shown to be greater than for either thermolysin or Bacillus subtilis neutral proteinase. It appears that the higher thermostability of caldolysin is due to the presence of 6 Ca2+ ions rather than 4 Ca2+ ions/molecule.

text: Interactions of calcium and other metal ions with caldolysin, the thermostable proteinase from Thermus aquaticus strain T351. Caldolysin, the extracellular proteinase from the extreme thermophile Thermus aquaticus strain T351, is stabilized by Ca2+. A variety of metal ions were able to substitute for Ca2+. Most were unable to confer as much stability as Ca2+, with the exception of the lanthanide ions, which increased the half-life at 95 degrees C from 1 h to more than 4 h. Results from a variety of separation methods indicated that caldolysin binds 6 Ca2+ ions/molecule of enzyme. The presence of non-linear Ca2+ titration plots, and the removal of 4 Ca2+ ions/molecule by treatment with a cationic ion-exchange gel suggested that caldolysin possesses at least two different types of Ca2+-binding sites, with different affinities. Average binding constants of the two types of binding sites were 2.8 X 10(4)M-1 (for the low-affinity sites) and 7.5 X 10(5) M-1 (for the high-affinity sites). The total Ca2+-binding free energy for caldolysin was shown to be greater than for either thermolysin or Bacillus subtilis neutral proteinase. It appears that the higher thermostability of caldolysin is due to the presence of 6 Ca2+ ions rather than 4 Ca2+ ions/molecule.

year: 1984

title: The fate and effects of JP-5 fuel in Antarctic soil: A controlled experiment at Scott Base, Antarctica

authors: Holmes, David J.

abstract: Hydrocarbon contamination of Antarctic soils is evident in limited areas where accidental fuel spills have occurred, usually near scientific bases or field camps. To understand the short-term fate and effects of fuel spills on Antarctic soils a contained experiment was established at Scott Base, Antarctica. 
Soil cores (105 x 10.5 cm diameter and 30 cm high) were filled with a sieved fraction(< 6.7 mm) of soil (Typic Anhyorthel), buried to the ground surface, and left to equilibrate over winter. Fuel (60 mL of JP-5, an equivalent depth of 7 mm) was applied in droplets, evenly to each of 63 cores. The remaining 42 cores were kept as controls. Ten cores (five control and five JP-5 treated) were weighed daily to monitor changes in moisture and snowfall, and to quantify the volatile loss of JP-5 fuel. In-situ temperatures (2, 5 and 20 cm depth) of both control and JP-5 treated cores were measured in triplicate at hourly intervals. Cores were destructively sampled in triplicate 0.1, 1, 3, 7, 14, 21, 28, 35, 42, 358, 365, 372, 379, and 397 days after fuel application and samples were returned, frozen, to New Zealand for total petroleum hydrocarbon (TPH) and microbial analyses. 
During destructive core sampling fuel penetration was observed to have reached a mean maximum depth of 15 cm ten days after JP-5 application, and 17 cm after one year. A large proportion (between 35% and 60%) of the fuel applied was lost to volatilisation within six weeks following the spill. The volatile loss of JP-5 fuel, as determined by weighing cores after correcting for moisture addition and evaporation of snowfall was about 9% after 18 hours, 26% after one week, and 35% after six weeks. The TPH content of the soil decreased in the 0-2.5 cm depth range from 46 000 mg kg- 1, two hours after fuel application, to 9 000 mg kg-1 after six weeks. In the depth range from 2.5 cm to the mean maximum depth of fuel penetration the TPH content of the soil decreased from 45 000 mg kg-1 two hours after fuel application to 10 000 mg kg-1 after six weeks. The corresponding volatile loss of JP-5 fuel, as determined from TPH concentrations within the total depth of fuel contaminated soil was about 50% after one week, and 60% after six weeks. Differences in the exact total fuel loss as recorded by weighing cores and TPH were attributed to various errors within each technique. The application of fuel had no measurable effect on soil temperature at 2 cm, 5 cm, and 20 cm depth, even though the surfaces of JP-5 treated cores were visibly darker than the control cores. The colour difference however had decreased markedly after three weeks. 
No differences were observed in the mean numbers of culturable heterotrophic bacteria and hydrocarbon-degrading microbes between JP-5 treated and control cores six weeks after the spill. It is, therefore, inferred that the initial application of fuel was non-toxic to culturable heterotrophic bacteria and hydrocarbondegrading microbes. 
Soil surface albedo measurements were also made over three previously contaminated sites in the Ross Sea region, and were found to be lower where the surface remained darkened by hydrocarbons, compared to nearby controls.

text: The fate and effects of JP-5 fuel in Antarctic soil: A controlled experiment at Scott Base, Antarctica Hydrocarbon contamination of Antarctic soils is evident in limited areas where accidental fuel spills have occurred, usually near scientific bases or field camps. To understand the short-term fate and effects of fuel spills on Antarctic soils a contained experiment was established at Scott Base, Antarctica. 
Soil cores (105 x 10.5 cm diameter and 30 cm high) were filled with a sieved fraction(< 6.7 mm) of soil (Typic Anhyorthel), buried to the ground surface, and left to equilibrate over winter. Fuel (60 mL of JP-5, an equivalent depth of 7 mm) was applied in droplets, evenly to each of 63 cores. The remaining 42 cores were kept as controls. Ten cores (five control and five JP-5 treated) were weighed daily to monitor changes in moisture and snowfall, and to quantify the volatile loss of JP-5 fuel. In-situ temperatures (2, 5 and 20 cm depth) of both control and JP-5 treated cores were measured in triplicate at hourly intervals. Cores were destructively sampled in triplicate 0.1, 1, 3, 7, 14, 21, 28, 35, 42, 358, 365, 372, 379, and 397 days after fuel application and samples were returned, frozen, to New Zealand for total petroleum hydrocarbon (TPH) and microbial analyses. 
During destructive core sampling fuel penetration was observed to have reached a mean maximum depth of 15 cm ten days after JP-5 application, and 17 cm after one year. A large proportion (between 35% and 60%) of the fuel applied was lost to volatilisation within six weeks following the spill. The volatile loss of JP-5 fuel, as determined by weighing cores after correcting for moisture addition and evaporation of snowfall was about 9% after 18 hours, 26% after one week, and 35% after six weeks. The TPH content of the soil decreased in the 0-2.5 cm depth range from 46 000 mg kg- 1, two hours after fuel application, to 9 000 mg kg-1 after six weeks. In the depth range from 2.5 cm to the mean maximum depth of fuel penetration the TPH content of the soil decreased from 45 000 mg kg-1 two hours after fuel application to 10 000 mg kg-1 after six weeks. The corresponding volatile loss of JP-5 fuel, as determined from TPH concentrations within the total depth of fuel contaminated soil was about 50% after one week, and 60% after six weeks. Differences in the exact total fuel loss as recorded by weighing cores and TPH were attributed to various errors within each technique. The application of fuel had no measurable effect on soil temperature at 2 cm, 5 cm, and 20 cm depth, even though the surfaces of JP-5 treated cores were visibly darker than the control cores. The colour difference however had decreased markedly after three weeks. 
No differences were observed in the mean numbers of culturable heterotrophic bacteria and hydrocarbon-degrading microbes between JP-5 treated and control cores six weeks after the spill. It is, therefore, inferred that the initial application of fuel was non-toxic to culturable heterotrophic bacteria and hydrocarbondegrading microbes. 
Soil surface albedo measurements were also made over three previously contaminated sites in the Ross Sea region, and were found to be lower where the surface remained darkened by hydrocarbons, compared to nearby controls.

year: 2002

title: The rhetorical organisation of Maori discourse: An illustration

authors: Crombie, Winifred

subjects: Māori medium education

abstract: Almost 20% all Māori students in New Zealand schools are involved in some form of Māori-medium education. These students need to develop competence in using the language for a wide range of purposes. They need, therefore, to understand a range of written discourse conventions. In seeking to assist them in this task, elders and scholars are turning to the works of major Māori figures of the past, works composed when the language was used widely in a range of discourse contexts. However, scholars need ways of analysing these texts and of communicating their findings to others. The primary aim of this paper is to demonstrate one such approach. A single letter of condolence written in Māori is analysed here in terms of rhetorical discourse structure. On the basis of the analysis, a number of hypotheses concerning epistolary discourse in Māori are put forward. The primary hypothesis is that letters of condolence written in Māori by highly competent users of the language are likely to be characterized by an overall Problem-Solution rhetorical prototype involving spiral multilayering.

text: The rhetorical organisation of Maori discourse: An illustration Almost 20% all Māori students in New Zealand schools are involved in some form of Māori-medium education. These students need to develop competence in using the language for a wide range of purposes. They need, therefore, to understand a range of written discourse conventions. In seeking to assist them in this task, elders and scholars are turning to the works of major Māori figures of the past, works composed when the language was used widely in a range of discourse contexts. However, scholars need ways of analysing these texts and of communicating their findings to others. The primary aim of this paper is to demonstrate one such approach. A single letter of condolence written in Māori is analysed here in terms of rhetorical discourse structure. On the basis of the analysis, a number of hypotheses concerning epistolary discourse in Māori are put forward. The primary hypothesis is that letters of condolence written in Māori by highly competent users of the language are likely to be characterized by an overall Problem-Solution rhetorical prototype involving spiral multilayering.

year: 2001-02