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  • 1
    Electronic Resource
    Electronic Resource
    High light enhances the expression of low-CO2-inducible transcripts involved in the CO2-concentrating mechanism in Synechocystis sp. PCC6803 (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The relative abundances of key gene transcripts encoding proteins involved in inducible inorganic carbon (Ci) transport in the cyanobacterium Synechocystis PCC6803 were quantified by real-time reverse-transcriptase-polymerase chain reaction under conditions of varying Ci and light levels. Significant increases in CO2-concentrating mechanism (CCM)-related transcript abundance were observed only in cells aerated with CO2-free air for 30 min in the light, but not in the dark, relative to illuminated cells grown at high CO2 levels (high-Ci cells). Cells were incubated under precisely defined conditions in a cuvette attached to a mass spectrometer to allow for the measurement of photosynthetic gas exchange rates, [Ci] and [O2], in combination with quantitative analysis of transcripts. Under conditions of increasing irradiance and low [Ci], or under conditions of decreasing [Ci] at constant irradiance, the abundances of cmpA (encoding part of the BCT1 HCO3– transporter), ndhF3 (encoding subunit of high-affinity CO2 uptake system) and sbtA (encoding Na+-dependent HCO3– transporter) transcripts tended to increase, relative to illuminated cells grown at high-CO2. The cmpA transcript appeared to be less responsive to decreasing [Ci] than either ndhF3 or sbtA. The induction of cmpA and ndhF3 transcripts was completely inhibited by 10 µm 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) compared to untreated control cells. This inhibitor had no effect on sbtA expression. In the presence of 2,6-dichlorobenzoquinone (DCBQ), the expression of the cmpA transcript tracked the apparent rate of O2 evolution from photosystem II closely as the irradiance was increased, reaching maximum levels of expression approximately 16-fold higher than control cells. Under the same conditions, the ndhF3 transcript increased by two- to three-fold, whereas the sbtA transcript did not respond to this treatment. The regulation of CCM induction in this strain is discussed in relation to current hypotheses on the sensing of Ci limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01175.x
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  • 2
    Electronic Resource
    Electronic Resource
    Carbonic anhydrase and C4 photosynthesis: a transgenic analysis (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Carbonic anhydrase (CA, EC 4.2.1.1) catalyses the first reaction in the C4 photosynthetic pathway, the conversion of atmospheric CO2 to bicarbonate in the mesophyll cytosol. To examine the importance of the enzyme to the functioning of the C4 photosynthetic pathway, Flaveria bidentis (L.) Kuntze, a C4 dicot, was genetically transformed with an antisense construct in which the cDNA encoding a putative cytosolic CA (CA3) was placed under the control of a constitutive promoter. Some of the primary transformants had impaired CO2 assimilation rates and required high CO2 for growth. The T1 progeny of four primary transformants were used to examine the quantitative relationship between leaf CA activity and CO2 assimilation rate. CA activity was determined in leaf extracts with a mass spectrometric technique that measured the rate of 18O exchange from doubly labelled 13C18O2. Steady-state CO2 assimilation rates were unaffected by a decrease in CA activity until CA activity was less than 20% of wild type when they decreased steeply. Transformants with less than 10% of wild-type CA activity had very low CO2 assimilation rates and grew poorly at ambient CO2 partial pressure. Reduction in CA activity also increased the CO2 partial pressure required to saturate CO2 assimilation rates. The present data show that CA activity is essential for the functioning of the C4 photosynthetic pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2003.01157.x
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  • 3
    Electronic Resource
    Electronic Resource
    Tissue factor and tissue factor pathway inhibitor (2004)
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 59 (2004), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The classical ‘cascade/waterfall’ hypothesis formulated to explain in vitro coagulation organised the amplification processes into the intrinsic and extrinsic pathways. Recent molecular biology and clinical data indicate that tissue factor/factor-VII interaction is the primary cellular initiator of coagulation in vivo. The process of blood coagulation is divided into an initiation phase followed by a propagation phase. The discovery of tissue factor pathway inhibitor further supports the revised theory of coagulation. Tissue factor is also a signalling receptor. Recent evidence has shown that blood-borne tissue factor has an important procoagulant function in sepsis, atherosclerosis and cancer, and other functions beyond haemostasis such as immune function and metastases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2044.2004.03679.x
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  • 4
    Electronic Resource
    Electronic Resource
    Novel gene products associated with NdhD3/D4-containing NDH-1 complexes are involved in photosynthetic CO2 hydration in the cyanobacterium, Synechococcus sp. PCC7942 (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 43 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Cyanobacteria possess light-dependent CO2 uptake activity that results in the net hydration of CO2 to HCO3– and may involve a protein-mediated carbonic anhydrase (CA)-like activity. This process is vital for the survival of cyanobacteria and may be a contributing factor in the ecological success of this group of organisms. Here, via isolation of mutants of Synechococcus sp. PCC7942 that cannot grow under low-CO2 conditions, we have identified two novel genes, chpX and chpY, that are involved in light-dependent CO2 hydration and CO2 uptake reactions; co-inactivation of both these genes abolished both activities. The function and mechanism of the CO2 uptake systems supported by each chp gene product differs, with each associated with functionally distinct NAD(P)H dehydrogenase (NDH-1) complexes. The ChpX system has a low affinity for CO2 and is de-pendent on photosystem I cyclic electron transport, whereas the inducible ChpY system has a high affinity for CO2 and is dependent on linear electron transport. We believe that ChpX and ChpY are involved in a unique, net hydration of CO2 to HCO3–, that is coupled electron flow within the NDH-1 complex on the thylakoid membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02753.x
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  • 5
    Electronic Resource
    Electronic Resource
    Does cavitation occur around powered toothbrushes? (2004)
    Oxford, UK : Munksgaard International Publishers
    Journal of clinical periodontology 31 (2004), S. 0 
    Details
    ISSN: 1600-051X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Aims/objectives: The aim of this investigation was to determine if cavitational activity occurred around powered toothbrushes using a chemical dosimeter system based on terephthalic acid (TA).Material and Methods: Five powered toothbrushes were used in this investigation: Braun Plaque Remover D8, Braun Oral-B 3D, Philips Jordan Sensiflex HX2520, Sonicare PS-1 and Sonicare Elite HX 7351/02. Each brush head was inserted into a conical flask containing 50 cm3 of aqueous TA solution. Brushes were operated for 10 and 20 min and a cuvette of the solution was placed in a fluorescence spectrometer (Perkin Elmer 3000). The fluorescence emitted at wavelength 425 nm, which is proportional to •OH radical concentration, was monitored.Results: Any cavitational activity that may have been produced by the powered toothbrushes was below the limit of detection of the system (〈10−8 M) for the timescales investigated.Conclusions: This work has demonstrated that cavitational activity does not occur around powered toothbrushes. Operating the toothbrushes for periods up to 20 min resulted in no cavitational activity being detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0303-6979.2004.00530.x
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  • 6
    Electronic Resource
    Electronic Resource
    Modelling the effect of water on the surface structure and stability of forsterite (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 332-341 
    Details
    ISSN: 1432-2021
    Keywords: Key words Forsterite ; Atomistic simulation ; Adsorption of water ; Surface reactivity ; Morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  We describe the application of atomistic simulation techniques to investigate the effect of associative and dissociative adsorption of water on the structures and stabilities of the low-index surfaces of forsterite. All surfaces are amenable to associative adsorption of water, while dissociative adsorption is energetically favourable on all but the non-dipolar {1 0 0} surface. Often, otherwise unstable (dipolar) surfaces are stabilised to a large extent by hydration, e.g. the dipolar {0 1 0} surface. However, on thermodynamic grounds we do not expect associatively adsorbed water to dissociate on all surfaces, as the energies released for dissociative adsorption of water on the non-dipolar {0 1 0} and {1 0 0} surfaces are less than those released for associative adsorption. As such, there is no energetic incentive for the associatively adsorbed water molecules to dissociate. The stabilities of the two terminations of the {0 1 0} surface, the main cleavage plane of forsterite, are reversed when hydroxylated, indicating that some dissolution of the magnesium ions may occur upon hydration, which is shown to be an exothermic process for both surface terminations. The equilibrium morphology was calculated as a way of assessing the change in surface energies. The experimental morphology of forsterite is adequately reproduced, suggesting that the relative stabilities of the surfaces, both unhydrated and hydroxylated, are calculated correctly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050262
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  • 7
    Electronic Resource
    Electronic Resource
    Theoretical investigation of metastable Al2SiO5 polymorphs (2001)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 548-557 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Using theoretical simulations based on density functional theory within the generalized gradient approximation, a series of metastable phase transitions occurring in low-pressure Al2SiO5 polymorphs (andalusite and sillimanite) are predicted; similar results were obtained using semiclassical interatomic potentials within the ionic shell model. Soft lattice modes as well as related structural changes are analysed. For sillimanite, an isosymmetric phase transition at ca 35 GPa is predicted; an incommensurately modulated form of sillimanite can also be obtained at low temperatures and high pressures. The high-pressure isosymmetric phase contains five-coordinate Si and Al atoms. The origin of the fivefold coordination is discussed in detail. Andalusite was found to transform directly into an amorphous phase at ca 50 GPa. This study provides an insight into the nature of metastable modifications of crystal structures and the ways in which they are formed. Present results indicate the existence of a critical bonding distance, above which interatomic interactions cannot be considered as bonding. The critical distance for the Si—O bond is 2.25 Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767301007644
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  • 8
    Electronic Resource
    Electronic Resource
    Constraints on the composition of the Earth's core from ab initio calculations (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 405 (2000), S. 172-175 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Knowledge of the composition of the Earth's core is important for understanding its melting point and therefore the temperature at the inner-core boundary and the temperature profile of the core and mantle. In addition, the partitioning of light elements between solid and liquid, as the outer ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35012056
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  • 9
    Electronic Resource
    Electronic Resource
    The elastic constants of MgSiO 3 perovskite at pressures and temperatures of the Earth's mantle (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 411 (2001), S. 934-937 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The temperature anomalies in the Earth's mantle associated with thermal convection can be inferred from seismic tomography, provided that the elastic properties of mantle minerals are known as a function of temperature at mantle pressures. At present, however, such information is difficult to ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35082048
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  • 10
    Electronic Resource
    Electronic Resource
    Possible thermal and chemical stabilization of body-centred-cubic iron in the Earth's core (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 424 (2003), S. 536-539 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The nature of the stable phase of iron in the Earth's solid inner core is still highly controversial. Laboratory experiments suggest the possibility of an uncharacterized phase transformation in iron at core conditions and seismological observations have indicated the possible presence of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01829
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