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  • Articles  (103)
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  • DSC  (59)
  • photosynthesis
  • Springer  (103)
  • National Academy of Sciences
  • 2020-2024
  • 1995-1999  (103)
  • 1997  (103)
  • 1
    Electronic Resource
    Electronic Resource
    Blends of poly(∈-caprolactone) with cellulose alkyl esters: effect of the alkyl side-chain length and degree of substitu tion on miscibility (1997)
    Springer
    Cellulose 4 (1997), S. 131-145 
    Details
    ISSN: 1572-882X
    Keywords: cellulose alkyl esters ; poly(∈-caprolactone) ; blends ; miscibility ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cellulose alkyl esters, CELL- OCOCnH2n+1(n = 1 ∼ 6), were synthesized by a homogeneous reaction of cotton cellulose with different acyl chlorides in N,N-dimethylacetamide--lithium chloride solution. The miscibility of the esterified celluloses with poly(∈-caprolactone) (PCL) was investigated, mainly through thermal analysis by differential scanning calorimetry (DSC). A polymer pair, cellulose butyrate (CB)/PCL, showed the highest miscibility of all the binary blends examined here; this is usual when relatively high-substituted esters (DS ≥ 2.0) are used as the respective component. The butyl ester derivatives with DS ≤ 1.5 showed poor miscibility with PCL
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018475520600
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  • 2
    Electronic Resource
    Electronic Resource
    The impact of elevated CO2 on growth and photosynthesis in Agrostis canina L. ssp. monteluccii adapted to contrasting atmospheric CO2 concentrations (1997)
    Springer
    Oecologia 110 (1997), S. 169-178 
    Details
    ISSN: 1432-1939
    Keywords: Key words Agrostis canina ; CO2 vents ; photosynthesis ; lignification ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The aim of this study was to characterise growth and photosynthetic capacity in plants adapted to long-term contrasting atmospheric CO2 concentrations (C a). Seeds of Agrostis canina L. ssp. monteluccii were collected from a natural CO2 transect in central-western Italy and plants grown in controlled environment chambers at both ambient and elevated CO2 (350 and 700 μmol mol−1) in nutrient-rich soil. Seasonal mean C a at the source of the plant material ranged from 610 to 451 μmol CO2 mol−1, derived from C4 leaf stable carbon isotope discrimination (δ13C). Under chamber conditions, CO2 enrichment stimulated the growth of all populations. However, plants originating from elevated C a exhibited higher initial relative growth rates (RGRs) irrespective of chamber CO2 concentrations and a positive relationship was found between RGR and C a at the seed source. Seed weight was positively correlated with C a, but differences in seed weight were found to explain no more than 34% of the variation in RGRs at elevated CO2. Longer-term experiments (over 98 days) on two populations originating from the extremes of the transect (451 and 610 μmol CO2 mol−1) indicated that differences in growth between populations were maintained when plants were grown at both 350 and 700 μmol CO2 mol−1. Analysis of leaf material revealed an increase in the cell wall fraction (CWF) in plants grown at elevated CO2, with plants originating from high C a exhibiting constitutively lower levels but a variable response in terms of the degree of lignification. In vivo gas exchange measurements revealed no significant differences in light and CO2 saturated rates of photosynthesis and carboxylation efficiency between populations or with CO2 treatment. Moreover, SDS-PAGE/ LISA quantification of leaf ribulose bisphosphate carboxylase/oxygenase (Rubisco) showed no difference in Rubisco content between populations or CO2 treatments. These findings suggest that long-term adaptation to growth at elevated CO2 may be associated with a potential for increased growth, but this does not appear to be linked with differences in the intrinsic capacity for photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050146
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  • 3
    Electronic Resource
    Electronic Resource
    The mixing behavior of pseudobinary phosphatidylcholine-phosphatidylglycerol mixtures as a function of pH and chain length (1997)
    Springer
    European biophysics journal 26 (1997), S. 447-459 
    Details
    ISSN: 1432-1017
    Keywords: Key words Phosphatidylcholine ; Phosphatidylglycerol ; DSC ; Phase diagrams ; Miscibility ; Nonideality parameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The miscibility of phosphatidylcholine (PC) and phosphatidylglycerol (PG) with different chain lengths (n = 14, 16) was examined by differential scanning calorimetry (DSC) at pH 2 and pH 7. The determination of the coexistence curves of the phase diagrams was performed using a new procedure, namely the direct simulation of the heat capacity curves as described recently (Johann et al. 1996, Garidel et al. 1997). From the simulations of the heat capacity curves first estimates for the nonideality parameters for nonideal mixing as a function of composition were obtained and phase diagrams were constructed using temperatures for the onset and offset of melting which were corrected for the broadening effect caused by a decrease in cooperativity of the transition. In most cases, the composition dependence of the nonideality parameters indicated nonsymmetric mixing behavior. The phase diagrams were further refined by simulations of the coexisting curves using a four-parameter model to account for nonideal and nonsymmetric mixing in the gel as well as in the liquid-crystalline phase. The mixing behavior of the systems was analyzed as a function of pH and chain length difference to elucidate the effect of these two parameters on the shape of the phase diagrams. At pH 7 the phase boundaries are much closer together and a narrower coexistence range is obtained compared to the corresponding phase diagrams at pH 2. For DPPC/DMPG at pH 2, the shape of the phase diagram and the strongly positive nonideality parameter ρ 1 for the liquid-crystalline phase indicates an upper azeotropic point. This indicates an unusual behavior of the system, namely more pronounced clustering of like molecules in the liquid-crystalline phase compared to the gel phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050099
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  • 4
    Electronic Resource
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    Etudes comparatives et identification des polyethylenes par analyses thermique differentielle et de diffraction des rayons X (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 233-245 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; polyethylenes ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In thermal analysis polyethylenes can be characterized by their melting temperature. With the polyethylene mixtures studied, we obtained the best results during solidification. Crystallization temperature decreased in the order: high density PE, low density PE linear, radical low density PE. Calorimetric measurement of crystallization enthalpies allowed the determination of the composition of each of the polyethylenes, in regenerated and recycled mixtures in relation with the frame of the plastic waste valorisation process. The rate of crystallization obtained from X-ray diffraction spectra of these polymers is function of their volumic mass. A good agreement has been observed between these two techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979267
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  • 5
    Electronic Resource
    Electronic Resource
    The use of DSC to characterize structural relaxation in thermosetting polymers (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 79-85 
    Details
    ISSN: 1572-8943
    Keywords: cross-linking degree ; DSC ; enthalpy relaxation ; epoxy resins ; physical aging ; reactive diluent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural relaxation in different epoxy-anhydride and epoxy-diamine resins has been investigated by differential scanning calorimetry using annealing and cooling rate experiments. The annealing experiments lead to the determination of enthalpy loss,δH, at an equivalent annealing temperatureT a=T g-20, and for periods of annealing time, ta, between 1 h and 4 months. The variation ofδH with logta, defines a relaxation rate per decade,rrpd, which is very sensitive to changes of the epoxy network. The cooling rate experiments allow the determination of the apparent activation energy,δh *. The effect of the degree of crosslinking, the addition of a reactive diluent, which acts as flexibilizer, and the length of cross-link onrrpd and δh* was studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987423
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  • 6
    Electronic Resource
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    Thermal analysis of polymer networks consisting of different homopolymers (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 149-154 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; heterogeneity in polymer network ; poly(methacrylic acid)-net-poly(oxytetramethylene) ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract TG and DSC were carried out on PMAA-net-POTM in order to elucidate the relation between the heterogeneity and the thermal changes; moreover, TG and DSC were carried out on PPOTMDM and PMAA to compare the results. The onset temperature in the last stage in the TG curve of PMAA-net-POTM increases as the concentrations of DMF and POTMDM in the polymerization decrease. This is explained in terms of plasticizers effects. A single peak due to fusion of POTM chains appears in the DSC curves of most copolymers. However, it is not seen in the DSC curves of copolymers with high heterogeneity. This is explained in terms of the freezing of POTM chains by frozen heterogeneous moieties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987433
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  • 7
    Electronic Resource
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    Study of curing behaviour and thermal properties of elastomer-modified bismaleimide resin (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 177-182 
    Details
    ISSN: 1572-8943
    Keywords: bismaleimide resin ; CTBN ; curing behaviour ; DSC ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bismaleimide resin (Compimide 353) was modified with the liquid elastomer carboxyl-terminated acrylonitrile butadiene (CTBN). The prereaction synthesis and curing of the CTBN-bismaleimide resin is discussed. The structure of the modified resin was identified by IR and NMR spectroscopy. The basic curing mechanism is also discussed. DSC and TG were used to study the curing behaviour and kinetic parameters, viz. the order of reaction, energy of activation and preexponential factor. Adhesive properties such as lap shear strength and peel strength at room temperature and elevated temperature were evaluated and are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987437
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  • 8
    Electronic Resource
    Electronic Resource
    Multiple melting peak analysis with gel-spun ultra-high molar mass polyethylene (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 343-349 
    Details
    ISSN: 1572-8943
    Keywords: double melting peak ; DSC ; fiber ; polyethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The multiple melting peaks observed on differential scanning calorimetry (DSC) of ultrahigh molar-mass polyethylene fibers (UHMMPE) are analyzed as a function of sample mass. Using modern DSC capable of recognizing single fibers of microgram size, it is shown that the multiple peaks are in part or completely due to sample packing. Loosely packed fibers fill the entire volume of the pan with rather large thermal resistance to heat flow. On melting, the fibers contract and flow to collect ultimately at the bottom of the pan. This process seems to be able to cause an artifact of multistage melting dependent on the properties of the fibers. A method is proposed to greatly reduce, or even eliminate, errors of this type. The crucial elements of the analysis of melting behavior and melting temperature are decreasing the sample size and packing the individual fibers in a proper geometry, or to introduce inert media to enhance heat transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987456
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal properties of a polyimide fiber (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 399-405 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; polyimide fiber ; TMA ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A commercially available polyimide fiber was investigated as a possible precursor for the formation of carbon fibers. The thermal response of the fiber was thoroughly investigated using DSC, TMA and TG. These responses were dependent on the atmosphere and tension during scanning. The fiber was stabilized at high temperatures both in inert and oxidative environments and the effect of these stabilization treatments on the structure and properties of the fiber was carefully followed. During heating, the fiber showed shrinkage tendency at small tensions, but at higher tensions the fibers could be stretched. Among the two environments investigated, air was more effective than nitrogen in getting a more stable fiber.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987463
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  • 10
    Electronic Resource
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    Compatibility of tire elastomers using derivative heat flow traces in the glass transition region (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 407-415 
    Details
    ISSN: 1572-8943
    Keywords: compatibility ; covulcanization ; derivative heat flow (δW/δT) ; DSC ; microheterogeneous
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Derivative heat flow curves give much more information about the phase heterogeneity of binary blends composed of NR, SBR and BR elastomers thanT g. In blend compositions, the areas under the derivative heat flow curves appear to be an additive function of the concentration of elastomers in the case of incompatible blends (NR/BR, NR/SBR). They are less than additive for either a partially compatible blend (uncured SBR/BR) or a compatible blend (covulcanized SBR/BR). In the case of 60/40 SBR/BR blends, a DSC (T 0.5) reveals a singleT g, in conformity with the earlier investigators, whereas the derivative heat flow curve shows two peaks (T p) indicating incomplete homogenization of the phases. This is a new observation not mentioned in the published literature. Thus, derivative heat flow traces are likely to provide a unique tool to determine compatibility of elastomers. The study also reveals the importance of sample contact with the DSC pan in quantitative determinations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987464
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  • 11
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    Analysis of physical and chemical networks by slow DSC and turbidimetry (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 449-454 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; network ; polyethylene ; turbidimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Semicrystalline polymers are made of a crystalline phase and of an amorphous phase. Recently, NMR, Raman and FTIR experiments have identified a third phase comprised of defects such as tie-molecules, in the organization of chains. Our investigation of physical gels has led us to believe that by following the heat flow in a very slow temperature ramp (0.05 K min−1), phasechanges, unnoticed in the usual fast ramp, could be detected. These are associated to a physical network strained in the temperature ramp. In order to obtain more information on the network phase, the polymer has been crosslinked The characteristics obtained by slow calorimetry and turbidimetry of the original and modified materials are compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987469
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  • 12
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    Cure characterization of rubber modified epoxy novolacs (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 483-490 
    Details
    ISSN: 1572-8943
    Keywords: carboxyterminated polybutadiene ; DSC ; DMA ; SEM ; toughened epoxy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new type of toughened epoxy polymer based on epoxy cresol novolac resin (ECN) and carboxy terminated polybutadiene (CTPB) liquid functional rubber has been studied. ECN has been synthesized in the laboratory and CTPB used was also of indigenised origin. Rubber modified epoxies were characterized with the help of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987475
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  • 13
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    Study of phenolic resin/EVA blends by thermal analysis (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 477-481 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; EVA blends ; phenolic resin ; TG-DTG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The properties of polymeric blends originate from the synergistic association of their components. In this investigation, phenolic resins obtained by the reaction of cashew-nut shell liquid (CNSL) and aldehyde are used in several applications. Mixtures of CNSL with industrial reject ethylene-co-vinyl acetate (EVA reject) were prepared with an EVA reject content up to 70%. The thermal compatibility and stability were evaluated by means of thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). For blends containing a high percentage of EVA reject, the TG curves clearly show two decomposition stages, one at 350
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987474
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  • 14
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    Detection of multiple nanophases by DSC (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 513-520 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; glass transition ; heat capacity ; melting transition ; nanophases ; polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Polymer molecules have contour lengths which may exceed the dimension of microphases. Especially in semicrystalline samples a single molecule may traverse several phase areas, giving rise to structures in the nanometer region. While microphases have properties that are dominated by surface effects, nanometer-size domains are dominated by interaction between opposing surfaces. Calorimetry can identify such size effects by shifts in the phase-transition temperatures and shapes, as well as changes in heat capacity. Specially restrictive phase structures exist in drawn fibers and in mesophase structures of polymers with alternating rigid and flexible segments. On several samples shifts in glass and melting temperatures will be documented. The proof of rigid amorphous sections at crystal interfaces will be given by comparison with structure analyses by X-ray diffraction and detection of motion by solid state NMR. Finally, it will be pointed out that nanophases need special attention if they are to be studied by thermal analysis since traditional ‘phase’ properties may not exist.
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    URL: http://dx.doi.org/10.1007/BF01987478
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  • 15
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    Separation of components of different molecular mobility by calorimetry, dynamic mechanical and dielectric spectroscopy (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 499-511 
    Details
    ISSN: 1572-8943
    Keywords: dielectric spectroscopy (DETA) ; DSC ; dynamic mechanical (DMA) spectroscopy ; glass transition ; PET ; polymers ; relaxation ; rigid amorphous ; temperature modulated DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The relaxation strength at the glass transition for semi-crystalline polymers observed by different experimental methods shows significant deviations from a simple two-phase model. Introduction of a rigid amorphous fraction, which is non-crystalline but does not participate in the glass transition, allows a description of the relaxation behavior of such systems. The question arises when does this amorphous material vitrify. Our measurements on PET identify no separate glass transition and no devitrification over a broad temperature range. Measurements on a low molecular weight compound which partly crystallizes supports the idea that vitrification of the rigid amorphous material occurs during formation of crystallites. The reason for vitrification is the immobilization of co-operative motions due to the fixation of parts of the molecules in the crystallites. Local movements (Β-relaxation) are only slightly influenced by the crystallites and occur in the whole non-crystalline fraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987477
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  • 16
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    Determination of kerogen type by using DSC and TG analysis (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 745-753 
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    ISSN: 1572-8943
    Keywords: DSC ; kerogen ; oxidation ; pyrolysis ; type determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using DSC analysis. Recently performed thermogravimetric studies (TG and DTG) with the same samples of KC indicated that the activation energy of the pyrolysis of specific KCs increases with increasing paraffinic structure in the KC. An opposite effect, i.e. a decrease of the activation energy with an increase of paraffinic structure was determined in the case of KC oxidation. In this study, using the standard ASTM E-698 method based on the determined temperature at which the maximum heat effect could be observed (exo in the case of oxidation and endo in the case of pyrolysis), an activation energy for the pyrolysis, as well as for the oxidation process was determined and also successfully correlated with the content of paraffinic structure of KC. Thus, the higher content of paraffinic structure in KCs indicates that higher values of the activation energy could be determined either in the case of pyrolysis or oxidation followed by DSC analysis.
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    URL: http://dx.doi.org/10.1007/BF01996758
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  • 17
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    Detection of recombined butter by DSC (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 795-799 
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    ISSN: 1572-8943
    Keywords: butter ; butter oil ; DSC ; recombined butter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC can be used to quickly determine if a product labeled as butter is actually a recombined butter made without milk. Recombined butter is manufactured from anhydrous milk fat, skim milk powder, water, salt, and lecithin. Melting profiles of tempered samples of natural butter and recombined butter were alike, but DSC curves from 5 to 25°C of untempered refrigerated samples revealed that the enthalpy of the melting transition around 17–20°C was much higher for natural butter than for recombined butter. The procedure for differentiating the two products can be completed in less than 20 min.
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    URL: http://dx.doi.org/10.1007/BF01996762
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  • 18
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    Influence of drying to the structure of lactitol monohydrate (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 809-816 
    Details
    ISSN: 1572-8943
    Keywords: dehydration ; drying method ; DSC ; lactitol ; lactitol monohydrate ; TG ; X-ray powder diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The purpose of this study is to find out the effect of the crystal water content on the crystal structure of lactitol monohydrate. Crystal water was removed by drying over silicagel at 40°C and by using phosphorus pentoxide as drying agent at 20°C. The amouts of water removals were identified by thermogravimetry, the melting points and the heat of fusions were calculated from the results of differential scanning calorimetry measurements and the structure of samples were identified by X-ray powder diffraction method. Over 23 w/w% of total water content could removed by gently drying until significant structural changes could be detected. The melting point of anhydrous lactitol obtained by drying lactitol monohydrate was 120°C and the melting enthalpy was 102 J g−1 when measured with heating rate 10°C min−1 by DSC.
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    URL: http://dx.doi.org/10.1007/BF01996764
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  • 19
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    Influence of enzymatic hydrolysis on functionality of plant proteins (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 831-837 
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    ISSN: 1572-8943
    Keywords: DSC ; enzymatic hydrolysis ; functional properties ; hemisphaericin ; mexicain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC was used to study the extent of denaturation of hemisphaericin and mexicain hydrolysates from corn gluten, soybean and sunflower meals. It was observed that the defatted meals studied exhibited only one broad peak transition. The data obtained demonstrated that the partial protein denaturation found with hemisphaericin or mexicain is correlated to modifications of functional properties. The two enzymes display different modes of action, according to the protein source.
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    URL: http://dx.doi.org/10.1007/BF01996767
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  • 20
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    Study of the polymorphic behaviour of some local anesthetic drugs (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 913-927 
    Details
    ISSN: 1572-8943
    Keywords: anesthetic drugs ; bupivacaine hydrochloride ; dibucaine hydrochloride ; DSC ; polymorphism ; prilocaine hydrochloride ; procaine hydrochloride ; solvent mediated transitions ; temperature resolved X-ray diffraction ; tetracaine base ; tetracaine hydrochloride ; thermodynamic relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The local anesthetic drug tetracaine hydrochloride is described in the Europ. Pharmacopea with a melting point of 148°C or with a range of 134 to 147°C due to the melting points of two other forms. The polymorphic behaviour of tetracaine hydrochloride has been studied by using thermal treatments, storage at 92% r.h., crystallizations and equilibrations with saturated solutions. Samples were characterized by X-ray diffraction, IR, thermal analysis and elemental analysis. Since some findings were difficult to interpret, temperature resolved X-ray diffraction was used additionally for the understanding of the thermal behaviour of tetracaine hydrochloride. In this study the polymorphic behaviour of some other local anesthetic drugs is compared. Ten different forms of tetracaine hydrochloride: six anhydrous crystalline forms, an amorphous form, a hemihydrate, a monohydrate and a tetrahydrate were identified. The relationships between all forms are given. The heating curve of the commercial form 1 is very dependent on the heating rate. This anhydrous form 1 is the thermodynamic stable modification at ambient temperature. The form 2 is reversibly enantiotrope to form 1. The four other modifications called 3, 4, 5 and 6 are monotropes of form 1. Only forms 1 and 5 are stable at ambient temperature. Form 1 is hygroscopic only at high humidity level of 92% r.h., form 5 is hygroscopic at 61% r.h. Both transform into the monohy-drate. No polymorphic forms of tetracaine base, dibucaine hydrochloride, procaine hydrochloride or prilocaine hydrochloride were found. The commercial form of bupivacaine hydrochloride is a monohydrate. Thermal treatment at 200°C gives one anhydrous form. As demonstrated by temperature resolved X-ray diffraction two other forms are detected by heating and cooling processes between 100 and 170°C. Equilibrations and crystallization experiments show that solvates are easily obtained in different solvents. Temperature resolved X-ray diffraction is a very efficient tool as a support to DSC for the identification of the transition processes and interpretation of thermal events and thermodynamic relationships. Equilibration experiments are very adequate to find out the thermodynamically stable form at ambient temperature (solvent mediated transitions).
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    URL: http://dx.doi.org/10.1007/BF01996777
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  • 21
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    Thermal analysis of powdered alumina materials (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 961-970 
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    ISSN: 1572-8943
    Keywords: distribution constant ; DSC ; powder compact ; Rosin-Rammler particle size distribution ; thermal resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract How a DSC result is influenced by the particle size distribution of a powder sample is shown, and a simple and optimal method to be included in a routine DSC analysis (e.g., purity determination) to improve the reliability of the analysis is proposed. In case ofα-Al2O3 powder, most reliable heat capacity data can be obtained by preparing a powder with a self-similar particle size distribution with a distribution constant of 0.7, and by compressing it under a pressure of 1.5 MPa for a duration of 5 min or longer.
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    Temperature distribution in polymer samples during DSC-scans (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 999-1005 
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    ISSN: 1572-8943
    Keywords: DSC ; finite element method ; temperature gradients ; polymer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential Scanning Calorimetry is frequently used for measurements of thermal properties on all kinds of substances. The temperature lag in the samples depend on the thermal properties and the thermal contact between sample and sample holder. In the paper, we discuss the temperature distribution in samples of comparatively low thermal conductivity, such as polymers. The purpose of this study is to pinpoint the substantial temperature differences that may occur in such bad conducting samples under different conditions. The calculations of the temperature gradients have been carried out by using a finite element software package.
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    A combined differential scanning calorimeter-optical video microscope for crystallization studies (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 991-998 
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    ISSN: 1572-8943
    Keywords: cryo-microscopy ; crystallization ; DSC ; ICE ; microscopy
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A simultaneous differential scanning calorimeter (DSC)-optical video microscope instrument has been developed. The instrument development included slight modifications to the sample head of a Perkin-Elmer DSC-7, along with the use of a CCD camera and magnifying lenses. The instrument permitted simultaneous following of optical and thermal events during isothermal and non-isothermal DSC experiments. The DSC curves were almost identical to those given by a standard DSC-7. The operational temperature range of the instrument is between −160 to 600°C. The capabilities of the DSC-video microscope are illustrated by examples of ice crystallization data in aqueous solutions of glycerol and dimethyl sulphoxide.
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    The high-low quartz inversion (1997)
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    Journal of thermal analysis and calorimetry 48 (1997), S. 19-38 
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    ISSN: 1572-8943
    Keywords: chalcedony ; crystalline disorder ; DSC ; DTA ; high-low quartz inversion ; silcretes
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The paper reviews studies on possible applications of the high-low quartz inversion in petrology. Since the first suggestions of Fenner and Tuttle, nearly fifty papers have dealt with the subject, including ten by the present authors. The detailed discussion of the preparative and instrumental factors which may influence the quartz inversion behaviour reveals that the DTA (DSC) runs have to be made under highly standardized conditions to permit measurement of the ‘material inherent factors’ (mainly crystal physical factors) which cause variations in shape and temperatures. The most striking variations in shape and temperatures of the inversion effect (e.g. including temperatures more than 70°C lower than the ‘textbook value’ of 573°C for the quartz inversion) are observed for microcrystalline quartz crystals. The literature and the authors' own investigation demonstrate that the most interesting field of application of the method is that of authigenic quartz formation in sediments and soils. The characterization of metamorphic quartz is more complicated. Four fields of study are chosen to demonstrate the possible application of the quartz inversion characterization for petrogenetic interpretations: (1) the differentiation between authigenic and inherited quartz crystals in sediments, (2) the characterization of the contact-metamorphic aureoles around granites, (3) special regional-metamorphic terrains and (4) (from a few so far unpublished studies) the differentiation between sedimentary and soil silcretes.
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    Determination of freezable water content of beef semimembranous muscle DSC study (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 259-266 
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    Keywords: DSC ; freezable water ; muscle water
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The freezable water contents of samples obtained from previously chilled semimembranous muscle of middle-aged beef carcasses after a 24 h cooling period a room at in 5±1
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    Use of DSC and TG for identification and quantification of the dosage form (1997)
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    Journal of thermal analysis and calorimetry 48 (1997), S. 473-483 
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    ISSN: 1572-8943
    Keywords: dosage form ; drug products ; DSC ; identification ; quantitation ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal analysis techniques, DSC and TG can advantageously be used in quality control of drug products. The methods are commonly used in preformulation for the study of polymorphism and for the study of the interactions drug substance-excipients, since these physical interactions can be the basis of the dosage form performance. For routine control of the drug products, DSC and TG methods which are quick, which require only few mg of the samples and which are automated, are very attractive for routine analysis of drug products. A single scan can give several qualitative and quantitative informations. DSC offer analytical possibilities only if the drug substance and the excipients do not have physical interactions or limited interactions (e.g. eutectic behaviour). About twenty marketed products have been analyzed by DSC and TG. In most of them identification of drug substance is easy. Several excipients could be identified in a tablet. Quantitations are demonstrated for some drug substances and excipients. DSC purity calculations have been applied to acetyl salicylic acid, paracetamol, cimetidine, pindolol, ibuprofen.
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    Membrane-bound Na+,K+-ATPase as the cardiac glycoside receptor (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 437-445 
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    ISSN: 1572-8943
    Keywords: cardiac glycoside binding ; DSC ; membrane protein ; membrane receptor binding ; Na+ ; K+-ATPase ; thermal unfolding ; titration calorimetry
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    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC studies are carried out to characterize Na+,K+-ATPase isolated from pig kidney in its natural membrane environment as well as in its purified state upon detergent treatment. The transition temperatures of the investigated thermal protein unfolding process, observed between 43 and 64.5° C, depend on the local membrane environment as well as onpH. In addition, the transition temperature is significantly increased upon binding of different cations and ligands which are known to interact with the enzyme. Evidence for a lipid phase transition around 23 °C in the original biological membrane is reported. The application of a calorimeter equipped with removable cells appears to be more suitable for the investigation of this type of membrane sample than an instrument with fixed capillary cells. Filling the sample capillary cell with an usual syringe, consisting of a long and thin needle, can influence the experimental results. Na+, K+ -ATPase acts as the receptor for cardiac glycoside binding. The thermodynamic parameters of this binding process are determined by titration calorimetry. The binding of ouabain, as a typical example, is unusually slow and is enthalpy driven. The enthalpy change upon binding enthalpy is −75 kJ mol−1 at 25 °C. The surprisingly low stoichiometric coefficient, resulting from an evaluation based on a simple one step binding model, is interpreted in terms of a dimeric receptor unit.
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    Preparation and analysis of aluminate sodalite ceramics from solution spray-dried precursors (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 647-656 
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    ISSN: 1572-8943
    Keywords: aluminate sodalite ceramics ; ceramics ; dielectric properties ; DSC ; ferroelectric transitions
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Aluminate sodalite ceramics, (Sr8Al12O24)(CrO4)2) — SACR, have been prepared from solution spray-dried precursors. The spray drying of a mixed aqueous nitrate solution gave an anhydrous powder which was thermally decomposed in air at 1350 °C to give a crystalline SACR powder with a median volume diameter of 4–6 μm. The SACR powder was dry pressed and sintered to 〉90% density. The yellow SACR powder showed two phase transitions between 10 and 45 °C with a 25 ° intermediate phase region indicative of a low defect concentration in the crystalline structure. A colour change observed in the sintered ceramic (changing to a mixed green/yellow) and a narrowing of the phase transition region (15–40 °C) are discussed. Dielectric measurements were consistent with the presence of two extrinsic ferroelectric transitions at 17 and 35 °C.
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    Racemic compound formation-conglomerate formation (1997)
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    Journal of thermal analysis and calorimetry 48 (1997), S. 691-696 
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    ISSN: 1572-8943
    Keywords: conglomerate ; DSC ; melting phase diagram ; recemic compound
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The phenomena of conglomerate formation-racemic compound formation were investigated in a series of five (N-alkyl)-2′,6′-pipecoloxylidides. The optically active enantiomers were prepared by optical resolution of the racemates using 2R,3R-tartaric acid and 0,0′-dibenzoyl-2R,3R-tartaric acid as resolving agent. By DSC measurement of the racemates and the enantiomer the binary phase diagrams were determined. Among the four racemic molecular compounds the N-methyl derivative is the more stable. By increasing the length of the alkyl chain the stability of the racemic compound decreased, and in case of the longest -butyl-chain conglomerate formation was observed.
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    Decay of (Fe1−xNix)0.96S DSC investigation (1997)
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    Journal of thermal analysis and calorimetry 48 (1997), S. 727-734 
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    Keywords: DSC ; monosulfide solid solution ; system Fe-Ni-S
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The decay of a monosulphide solid solution (mss) with the composition (Fe1−1Nix)0.96S was investigated by means of differential scanning calorimetry in the temperature range, from 20 to 305
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    DSC of etched aluminum foils for use in electrolytic capacitors (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1305-1314 
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    ISSN: 1572-8943
    Keywords: DSC ; electrolytic capacitors ; etched Al foils ; thermal resistance ; transient state
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A DSC method for evaluating the surface area of etched Al foils for use in high performance electrolytic capacitors is presented. A linear relationship between the etching degree (effective surface area) and the thermal resistance of the sample is obtained by means of DSC, based on the transient phenomenon. This method using the transient state in DSC measurement is not only novel, but also rapid and simple in evaluating the surface area of an etched aluminum foil. The method is effective even when the Al foil has a naturally oxidized surface.
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    A study of the mechanism of adsorption of ethyl cellulose on silver powder (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1357-1364 
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    Keywords: chemisorption ; desorption ; DSC ; dynamic FT-IR silver powder ; XPS
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The mechanism of adsorption and desorption of ethyl cellulose (EC) on and from silver powder was studied. After analysis with DSC, XPS and dynamic FT-IR, which could be heated by a program-controlled heater, applied to observe the states of pure EC and of EC adsorbed on silver powder, and also the thermal decomposition of EC from silver powder, the chemisorption bonding bridge between the oxygen atoms of EC and the silver atoms investigated. The differences in thermal decomposition between pure EC and EC adsorbed in silver powder were also studied. It was concluded that the chemisorption bonding between the oxygen atoms of EC and the silver atoms mainly involved the lone-pair electrons of the oxygen atoms on the EC chain and the outer empty 5 sp3 hybrid orbital of the silver. Because of the formation of this bridge, the bonds between neighboring carbon and oxygen atoms are weakened. As a result of this effect, the C-O bonds in the EC chain are broken more easily than the C-H bonds, which leads to the observation of -C-H- fragments in the upper space when EC adsorbed on silver is heated. When the same experiments were carried out on pure EC, almost all kinds of broken fragments of the EC molecule, including -C-H-, -C=O- and -C-O- appeared simultaneously.
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    Reaction pathway and kinetics of the thermal decomposition of synthetic brochantite (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1467-1475 
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    ISSN: 1572-8943
    Keywords: CRTA ; DSC ; kinetics ; synthetic brochantite ; TG-DTA ; thermal decomposition
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction pathway of the thermal decomposition of synthetic brochantite, Cu4(OH)6SO4, to copper(II) oxide was investigated through the detailed kinetic characterization of the thermal dehydration and desulferation processes. The dehydration process was characterized by dividing into two overlapped kinetic processes with a possible formation of an intermediate compound, Cu4O(OH)4SO4. The dehydrated sample, Cu4O3SO4, was found first to be amorphous by means of XRD, followed by the crystallization to a mixture of CuO and CuO-CuSO4 at around 776 K. The specific surface area and the crystallization behaviour of the amorphous dehydrated compound depend largely on the dehydration conditions. The thermal desulferation process is influenced by the gross diffusion of the gaseous product SO3, which is governed by the advancement of the overall reaction interface from the top surface of the sample particle assemblage to the bottom.
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    Experimental investigation into the heat capacity measurement using an modulated DSC (1997)
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    Journal of thermal analysis and calorimetry 50 (1997), S. 365-373 
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    ISSN: 1572-8943
    Keywords: DSC ; heat capacity ; indium ; linearity ; modulated DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Experiments using a commercial modulated DSC (MDSC) for the measurement of specific heat capacity of a sample have been carried out. It is found that because the amplitude of heat flow of MDSC is a complicated non-linear function of various experimental conditions such as the modulation frequency and the heat capacities of a sample and pan, the methodology of heat capacity determination using an MDSC in a single run has not been justified. The experimental results, on the other hand, agree with the theoretical equation of one of the authors. It is therefore concluded that the capabilities of MDSC should be further examined.
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    Thermal decomposition of the magnesium, zinc, lead and niobium chelates derived from 8-quinolinol (1997)
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 625-632 
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    ISSN: 1572-8943
    Keywords: DSC ; NMR ; 8-quinolinol compounds ; TG-DTG ; stability ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Solid M-Ox compounds, whereM represents Mg(II), Zn(II), Pb(II) and NbO(III), and Ox is 8-quinolinol, have been prepared. Thermogravimetry, derivative thermogravimetry (TG, DTG), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and infrared absorption spectra (IR) have been used to characterize and to study the thermal stability and thermal decomposition of these compounds.
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    Metrologically based procedures for the temperature, heat and heat flow rate calibration of DSC (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1125-1134 
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    Keywords: calibration material ; calibration procedure ; DSC ; heat calibration ; heat flow rate calibration ; standards ; temperature calibration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Metrologically based measuring procedures and evaluation methods are recommended as guidance for practical temperature, heat and heat flow rate calibration of DSC instruments which are largely independent of instrumental, test and sample parameters. The relevant terms are defined, the measuring procedures and evaluation methods described, calibration materials and their characteristic data stated and guidance for the sample handling provided. Reference is made to three extended papers on calibration. The recommendations were developed by the working group ‘Calibration of Scanning Calorimeters’ of the German Society of Thermal Analysis (GEFTA).
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    The thermal decomposition of NaHCO3 (1997)
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    Journal of thermal analysis and calorimetry 50 (1997), S. 773-783 
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    Keywords: DSC ; FT-IR ; kinetics and mechanism ; SEM ; sodium hydrogencarbonate ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract New EGA findings revealed that the small endothermal event preceding that of the main decomposition of commercial NaHCO3 involves the simultaneous evolution of water and CO2. At very high sensitivity, EGA experiments evidenced that the above (limited) evolution of gases also took place from the recrystallized material for which thermal methods gave no indication of endotherms. Careful reexamination of previous DSC results indicated that for one kind of recrystallized material a very small endotherm had been neglected. Renewed experiments revealed that this endotherm can be enhanced if the samples are prepared by crushing and sieving in a wet atmosphere. Parallel FT-IR experiments on commercial and recrystallized materials demonstrated the presence of carbonate in samples that had previously been taken just beyond the first small endotherm; this confirmed the EGA results. SEM experiments showed that surface texture changes take place when samples are heated to temperatures just above that of the preliminary endotherm. On the basis of these new findings, the interpretation previously given to the small endotherm is revised and detailed knowledge is gained on the mechanism of decomposition of NaHCO3.
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    A study of the thermal analysis of the solid solution (AgxK1−xNO3 (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 287-295 
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    ISSN: 1572-8943
    Keywords: (AgxK1−x)NO3 ; DSC ; IR ; solid solution
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of partial replacement of K+ by Ag+ in the mixed system of KNO3 and AgNO3 during a set of DSC heating cycles was studied by means of a modern computerized DSC system. Thermal analysis was performed in the vicinity of the phase transition II → I for pure KNO3. The results revealed a large change in enthalpy and the phase transition temperature close to the morphotropic boundary x=0.5–0.6. At this boundary, the transformation enthalpy reached the maximum value of ∼101 J g−1. On the basis of the data obtained from this accurate thermal analysis work, a model is suggested for the energy barrier of rotation of the nitrate ion in the mixed nitrate system.
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    A calorimetric study of egg white proteins (1997)
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    Journal of thermal analysis and calorimetry 48 (1997), S. 683-690 
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    ISSN: 1572-8943
    Keywords: calorimetry ; DSC ; egg white ; egg white fractions ; fractionation ; thermoph-pr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Egg white is of great interest for many culinary and industrial applications. Egg white is used for coating, gluing, thickening and so on in pasta, desserts, etc. There is thus a great interest from the industrial point of view to better know this raw material, used in very large amounts in the dessert production for example, and to obtain egg white fractions with different functional properties. Various egg white fractions prepared by selected procedures were analyzed by differential scanning calorimetry (DSC). The products resulting from a given fractionation procedure can thus be described by the thermal denaturation parameters (temperatures and enthalpies) of the egg white proteins. This work demonstrates the interest of the DSC technique and proves that the fractionation procedures selected here give the expected protein fractions.
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    DSC study of transformation kinetics of liquid-crystallines based on 1,4-phenylene 4-n-methoxybenzoate-4-allyloxybenzoate (1997)
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    Journal of thermal analysis and calorimetry 48 (1997), S. 903-907 
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    Keywords: DSC ; liquid-crystalline ; PMMS-PMOBAOB ; PMOBAOB ; transformation kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transformation kinetics of liquid-crystalline 1,4-phenylene 4-n-methoxybenzoate-4-allyl-oxybenzoate (PMOBAOB) and a liquid-crystalline poly(mesogen/methyl) siloxane (PMMS) was studied by means of a non-isothermal method using differential scanning calorimetry. This determination led to an apparent activation energy of transformation of 639.0 and 306.5 kJ mol−1, respectively. The values of the Avrami exponentn were 1.8 and 1.1. The results show that the process of transformation of PMOBAOB involves a constant number of nuclei growing in two dimensions at a constant rate, while the process of transformation of PMMS-PMOBAOB involves a constant number of nuclei growing in one dimension at a constant rate.
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    Modelling solute segregation to partial dislocations for DSC evaluations (1997)
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    Journal of thermal analysis and calorimetry 48 (1997), S. 1229-1248 
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    ISSN: 1572-8943
    Keywords: α-Cu-Al alloys ; dislocations ; DSC ; energetics ; recrystallization ; rolled ; segregation ; short-range-order
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A general model is discussed for assessing the energy release due to the pinning of solute atoms to partial dislocations. The present approach discloses the influence of dislocation character distributions on the magnitude of this energy. In order to test its validity in αCu-Al alloys, differential scanning calorimetry (DSC) evaluations associated with the different peaks involved during linear heating were performed employing both cold worked and quenched materials. Dislocation densities were calculated from recrystallization traces. On the basis of this model it was concluded that the observed energy difference between the deformed and the quenched materials during the exothermic peak designated as Stage 2 corresponds to the pinning process. It was also concluded that nearly equal number of edge and screw dislocations are present in the dislocation configuration of deformed alloys. Nevertheless, it is proposed that dislocation-induced order might also occur as a consequence of enhanced solute concentration around the partials.
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    Detection of compatibility of some rubber blends by DSC (1997)
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    Journal of thermal analysis and calorimetry 48 (1997), S. 1299-1310 
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    ISSN: 1572-8943
    Keywords: compatibility ; DSC ; master curves ; mechanical measurements ; rubber blends
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The compatibility of some technically important polymer blends, namely BR/NR, NR/NBR and CR/NBR, has been investigated using the DSC method. In addition, dynamic mechanical measurements have been carried out for the NR/NBR blends over the frequency range of 10−4 Hz –200 Hz and temperatures ranging from −70 to +70°C. The results obtained show that the three rubber blends are not compatible over the entire composition range as proven by the DSC and mechanical measurements. By analyzing the heat capacity increases at the glass transitions of the separate phases in the NR/BR blend, it was possible to suggest the presence of a limited compatibility at the boundaries of the two phases. By comparing this work with prior measurements, it was possible to conclude that the calorimetric method is a more efficient tool for the study of compatibility of polymer blends when compared to ultrasonic and viscosity methods. Furthermore, it was found that polymers that show compatibility when measured with an ultrasonic method could behave compatible, semicompatible or incompatible when analyzed by DSC. On the other hand, blends that show incompatibility by the ultrasonic method are always incompatible by the DSC method.
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    DSC and X-ray studies on side-chain crystallization of comb-like polymers (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 115-121 
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    ISSN: 1572-8943
    Keywords: comb-like polymer ; DSC ; fluorocarbon chain ; side-chain crystallization ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal properties of acrylate and methacrylate monomers containing long-fluorocarbon chains (H(CF2)nCH2OCOCH=CH2, (FnA) and H(CF2)nCH2OCOC(CH3)=CH2, (FnMA), wheren=6, 8, 10) and their comb-like polymers have been investigated by differential scanning calorimeter (DSC) and X-ray diffraction. The comb-like polymers (PF10A and PF10MA) with sufficiently long-fluorocarbon chains showed a simple melting and crystallizing behavior. For the fusion of PF10A in 1st heating, enthalpy change δH f was 18 kJ mol−1 and entropy change δS f was 45 J K−1 mol−1, while for PF10MA the values δH f and δSf were 5.3 kJ mol−1 and 14 J K−1 mol−1, respectively. Melted PF8A crystallized slowly, whereas PF8MA with same fluorocarbon chain and also both of PF6A and PF6MA with shorter fluorocarbon chains can hardly crystallize by the aggregation of side-chains. Effects of the length of side-chain and the flexibility of main chain on the side-chain crystallization of comb-like polymers are clear. Crystallization process of the methacrylate monomers was sensitively affected by the scanning rate of DSC measurement and the length of fluorocarbon chains.
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    Temperature calibration of heat flux DSC's on cooling (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 193-199 
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    ISSN: 1572-8943
    Keywords: DSC ; liquid crystals ; temperature calibration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The temperature calibration of a TA Instruments 3200-2920 DSC has been performed on cooling using the isotropic → nematic, isotropic → cholesteric and other liquid crystal → liquid crystal transitions of thermally stable, high purity liquid crystals. The thermal stability of these liquid crystals has been verified by measuring the temperature of the mentioned transitions during cyclic heating and cooling experiments. Correspondence has been established between the real and indicated temperature during cooling for all combinations of heating and cooling rates of practical interest: correction values were determined to the indicated temperature in order to obtain the real temperature on cooling. These correction values were calculated as the average from the temperatures of four or five different liquid crystal transitions for each heating-cooling rate combination. The accuracy of the temperature calibration on cooling is ca. 0.2
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    Thermal transitions and polymer/polymer miscibility (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 227-234 
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    ISSN: 1572-8943
    Keywords: DSC ; EVA ; interaction parameter ; polymer blends ; PVC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to provide additional information on the miscibility of the PVC/EVA system, calorimetric parameters such as ΔC pi,T gi and ΔT gi were obtained with a different approach. A qualitative and quantitative measure of the blend composition at the interface was obtained. This indicated that the domains are rich in each component and the presence of the second component in the phase has little effect on the main chain relaxation. The PVC fraction in the EVA-rich phase is always larger than the EVA fraction in the PVC-rich phase. Positive and small values of the Flory-Huggins interaction parameter were obtained from calorimetric data.
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    Thermal transitions and polymer/polymer miscibility (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 235-245 
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    ISSN: 1572-8943
    Keywords: DSC ; EVA ; interaction parameter ; polymer blends ; PVC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Poly(vinyl chloride) was blended with ethylene-vinyl acetate copolymer containing 70 wt% of vinyl acetate. The system shows a single glass transition temperature for all compositions, indicating their miscibility. TheT g vs. composition curves display an inflection, which changes with the chemical environment of the initial solution. The best fit to the shape of the curve was well reproduced by the Kovacs-Braun equation. The δT g values reveal local heterogeneity, which means no total miscibility at a molecular level. Negative values of the Flory-Huggins interaction parameter were obtained from the calorimetric data.
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    Characterization of isomeric elastomers using thermal analysis (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 293-301 
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    ISSN: 1572-8943
    Keywords: characterization ; cis- ; trans isomers ; crystallinity ; DEA ; degradation ; DMA ; DSC ; DTG ; enthalpy ; glass transition temperature ; isomers ; vinyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Many of the isomers of polybutadiene and polyisoprene elastomers can be characterized by thermal analysis.T g is sensitive to side chain units (1,2 or 3,4 structure) for both polymers. Crystallinity measurements can characterizecis andtrans isomers. DMA and DEA master curves provide an idea of the heterogeneity of the chain units from the width of the loss factor curves in theT g region. Thermal and thermooxidative degradation, as followed by DSC and DTG, can differentiate specific natural and synthetic isomers of polyisoprenes in raw and vulcanized states.
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    Study of gelation using differential scanning calorimetry (DSC) (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 303-310 
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    ISSN: 1572-8943
    Keywords: curing ; DSC ; epoxy ; gel time ; gelation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method for determining the degree of conversion of gelation (αgel) and gel time (t gel) at gel point using a single technology, DSC, is discussed in this work. Four kinds of thermoset resins are evaluated. It is found that the mutation points of reduced reaction rate (V r ) vs. reaction conversion (α) curves, corresponding with the changes of reaction mechanism, represents the gelation of the reaction. The α at the mutation point is defined as αgel. From isothermal DSC curves, the point at αgel is defined ast gel. Traditional techniques (ASTM D3532 and DSC method) are also used to determine αgel andt gel in order to demonstrate this new method. We have found that the results obtained from this new method are very consistent with the results obtained from traditional methods.
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    Thermal behavior of poly(α-n-alkyl β-L-aspartate)s (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 693-702 
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    ISSN: 1572-8943
    Keywords: DSC ; helical conformation ; poly(α-n-alkyl-L-aspartate)s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of poly(α-n-alkyl β-L-aspartate)s (n being the number of carbon atoms in the linear alkyl side chain, withn=1, 2, 4, 6, 8, 12, 18 and 22), was studied by differential scanning calorimetry and thermogravimetric analysis. The effect of the length of the alkyl group on thermal properties such as stability, melting and crystallization of side chains, was investigated. For the polymers with n≥12, two endothermic peaks at T1 and T2 were detected separating three distinct phases A, B and C. The peak at T1 corresponds to the melting of the crystallized paraffinic side chains (transition A-B), and the peak: at T2 may be attributed to a transition (B-C), implying a liquid crystal phase.
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    A comparative test of differential scanning calorimeters (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1105-1114 
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    ISSN: 1572-8943
    Keywords: DSC ; resolution ; sensitivity ; test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Dutch Society for Thermal Analysis has developed tests to measure the resolution and the sensitivity of Differential Scanning Calorimeters. For this test the substance 4,4′-azoxyanisole is used. This substance shows two transitions: a solid to liquid crystal transition at about 117°C (ΔH≈120 J g−1) and a liquid crystal to isotropic liquid transition at about 134°C (ΔH≈2 J g−1). The resolution test is performed using an amount of 5 mg substance and a high heating rate of 20°C min−1. The resolution is evaluated by measuring how well the two peaks are separated. An amount of 0.25 mg substance and a low heating rate of 0.1 °C min−1 is used for the sensitivity test. The sensitivity is evaluated as the ratio of the peak height of the LC-transition and the top-top noise level. Members of the TAWN were asked to participate in the test. Each participant was provided with an amount of sample and a test procedure. 47 Contributions were received and these results are presented.
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    The heat capacities of selected inorganic alkali metal compounds (1997)
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1321-1326 
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    ISSN: 1572-8943
    Keywords: alkali metal compounds ; DSC ; heat capacity ; high temperature ; thermodynamic data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The heat capacities of selected inorganic binary and ternary alkali metal compounds are determined using differential scanning calorimetry (DSC). As part of an ongoing research program at Battelle Memorial Institute since 1983, the heat capacities of cesium and rubidium chalcogenides, aluminates, silicates and uranates in the temperature range 310 to 800 K have been added to the series of compounds. The measured data is to be combined with the standard enthalpies of formation and low temperature heat capacities to obtain reliable thermodynamic data on the alkali metal compounds to high temperatures.
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    Determination of differences in free and bound water contents of beef muscle by DSC under various freezing conditions (1997)
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 617-624 
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    ISSN: 1572-8943
    Keywords: bound water ; DSC ; free water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The differences in bound water content of beef semimembranous muscle samples obtained from previously chilled (24 h at +4°C) middle-aged beef carcasses were determined by the use of DSC. Initially, samples obtained from fresh, unprocessed meat were frozen at −40, −50 or −65°C to determine their melting peaks for freezable water (free water) content with the use of DSC. The samples were then subjected to an environment with an ambient temperature of −30, −35, −40 or −45°C, with no air circulation, or with an air circulation speed of 2 m s−1, until a thermal core temperature of −18°C was attained; this was followed by thawing the samples until a thermal core temperature of 0°C was reached. This process was followed by subjecting the samples to the ambient temperatures mentioned above, to accomplish complete freezing and thawing of the samples, with DSC, and thereby determination of the freezable water contents, which were then used to determine the peaks of melting. The calculated peak areas were divided by the latent heat of melting for pure water, to determine the freezable water contents of the samples. The percentage freezable water content of each sample was determined by dividing its freezable water content by its total water content; and the bound water content of each sample was determined by subtracting the percentage free water content from the total. In view of the fact that the free water content of a sample is completely in the frozen phase at temperatures of −40°C and below, the calculations of free and bound water contents of the samples were based on the averages of values obtained at three different temperatures.
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    Thermal analysis of the system KCL-LiCI by differential scanning calorimetry (1997)
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 347-354 
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    ISSN: 1572-8943
    Keywords: DSC ; eutectic composition ; LiCl-KCl system ; phase diagram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal analysis of the binary system KCl-LiCl in the composition range 0.368–0.812 mol fraction of LiCl was studied by differential scanning calorimetry (DSC). On the basis of the DSC curves, the experimental data for the phase-diagram, the latent heat of fusion, and the average specific heat in the liquid and solid states are presented as a function of the composition of the mixture. The experimental results compared with literature data. The following empirical correlation between the heat of fusion (ΔH) and of compositions of the mixture in mol fraction of LiCl (x) was obtained: ·GH=26.95−50.20x+43.06x2 with a minimum value of 11.8 kJ(g mol)−1 at the eutectic point of 0.587 mol fraction of LiCl at 354.4°C. These results are required as basic data to develop thermal energy storage materials, based on the phase change of a molten mixture of KCl-LiCI.
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    Electron Paramagnetic Resonance and Differential Scanning Calorimetry Studies of Thorium and Tin Phosphate Xerogels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 315-319 
    Details
    ISSN: 1573-4846
    Keywords: thorium ; tin ; phosphate xerogels ; EPR ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different transparent phosphate xerogels were synthesized usingconcentrated solutions of metal chlorides and phosphoric acid with aproper mole ratio of both components. By this method we prepared bulksamples of thorium and tin(IV) phosphate xerogels by drying at room temperature or at 350 K. Some properties of these amorphous materialswere studied by means of differential scanning calorimetry (DSC) andelectron paramagnetic resonance (EPR) techniques. Depending on moleratio $$\frac{{{\text{metal}}}}{{{\text{phosphate}}}}$$ , these xerogels show, near 180 K, inflection points which we interpret as T g . Samples dried at 425 K lose their transparency and have no T g . Thus, it seems that the “glassy” state is due to water molecules remaining in the material. The same properties wereconfirmed by EPR studies of the xerogels doped with Cr3+ andFe3+ ions as probes. These results show the existence of twodifferent phases in the xerogels: a liquid-like one, in the range from190 K to 350 K and a solid-like one, in the range from 4 K to 190 K.
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    Electron paramagnetic resonance and differential scanning calorimetry studies of thorium and tin phosphate xerogels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 315-319 
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    ISSN: 1573-4846
    Keywords: thorium ; tin ; phosphate xerogels ; EPR ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different transparent phosphate xerogels were synthesized using concentrated solutions of metal chlorides and phosphoric acid with a proper mole ratio of both components. By this method we prepared bulk samples of thorium and tin(IV) phosphate xerogels by drying at room temperature or at 350 K. Some properties of these amorphous materials were studied by means of differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) techniques. Depending on mole ratio metal/phosphate, these xerogels show, near 180 K, inflection points which we interpret asT g . Samples dried at 425 K lose their transparency and have noT g . Thus, it seems that the “glassy” state is due to water molecules remaining in the material. The same properties were confirmed by EPR studies of the xerogels doped with Cr3+ and Fe3+ ions as probes. These results show the existence of two different phases in the xerogels: a liquid-like one, in the range from 190 K to 350 K and a solid-like one, in the range from 4 K to 190 K.
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    Site-directed mutagenesis of the basic residues 321K to321 G in the CP 47 protein of photosystem II alters the chloride requirement for growth and oxygen-evolving activity in Synechocystis 6803 (1997)
    Springer
    Plant molecular biology 34 (1997), S. 455-463 
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    ISSN: 1573-5028
    Keywords: photosystem II ; photosynthesis ; chlorophyll-binding protein ; Synechocystis ; oxygen evolution ; oligonucleotide-mediated mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract CP 47, a component of photosystem II (PSII) in higher plants, algae and cyanobacteria, is encoded by the psbB gene. Site-specific mutagenesis has been used to alter a portion of the psbB gene encoding the large extrinsic loop E of CP 47 in the cyanobacterium Synechocystis 6803. Alteration of a lysine residue occurring at position 321 to glycine produced a strain with altered PSII activity. This strain grew at wild-type rates in complete BG-11 media (480 µM chloride). However, oxygen evolution rates for this mutant in complete media were only 60% of the observed wild-type rates. Quantum yield measurements at low light intensities indicated that the mutant had 66% of the fully functional PSII centers contained in the control strain. The mutant proved to be extremely sensitive to photoinactivation at high light intensities, exhibiting a 3-fold increase in the rate of photoinactivation. When this mutant was grown in media depleted of chloride (30 µM chloride), it lost the ability to grow photoautotrophically while the control strain exhibited a normal rate of growth. The effect of chloride depletion on the growth rate of the mutant was reversed by the addition of 480 µM bromide to the chloride-depleted BG-11 media. In the presence of glucose, the mutant and control strains grew at comparable rates in either chloride-containing or chloride-depleted media. Oxygen evolution rates for the mutant were further depressed (28% of control rates) under chloride-limiting conditions. Addition of bromide restored these rates to those observed under chloride-sufficient conditions. Measurements of the variable fluorescence yield indicated that the mutant assembled fewer functional centers in the absence of chloride. These results indicate that the mutation K321G in CP 47 affects PSII stability and/or assembly under conditions where chloride is limiting.
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    Yield, water use efficiency and nitrogen uptake in potato: influence of drought stress (1997)
    Springer
    Potato research 40 (1997), S. 19-34 
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    ISSN: 1871-4528
    Keywords: water stress ; photosynthesis ; stress index ; dry matter partitioning ; tuber quality ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A lysimeter experiment was performed to study the optimal allocation of limited water supply in potatoes. Irrigation regimes equal to 40, 60 and 80% of maximum evapotranspiration (ET) were evenly applied over the crop cycle. Other treatments involved withholding 80 mm of irrigation, based on ET, beginning at each of three designated growth stages (tuber initiation, early and late tuber growth). An irrigated control treatment, restoring the entire ET, was included for comparison. Continuous drought stress reduced photosynthesis as irrigation volumes were reduced. Plant biomass and tuber yield decreased almost proportionally to water consumption, so that WUE was roughly constant. N uptake was highest in the control and in 80% ET treatment. Withholding water during tuberisation severely hindered plant physiological processes and penalized tuber yield. Reductions in photosynthesis, total biomass and yield were the greatest when drought was imposed during tuber initiation. The earliest stress resulted in the lowest WUE and N uptake. A new crop water stress index (SI) was proposed, which combines atmospheric demand for water and canopy temperature.
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    Influence of tidal location on morphology, photosynthesis and pigments of the agarophyte, Gelidiella acerosa, from Northern Philippines (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 525-532 
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    ISSN: 1573-5176
    Keywords: Gelidiella ; agarophyte ; photosynthesis ; P-I curve ; morphology ; tide ; pigment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The red seaweed agarophyte, Gelidiella acerosa (Forsskål) (Feldmann& Hamel) was collected from tidepools, high intertidal rocks. and shallow subtidal are as along a reef flat in Ilocos Norte, northern Philippines. The three populations were compared during the summer (dry) and rainy (wet) seasons to determine changes in morphology and photoacclimation capacity as possible use in mariculture. During summer months (February toApril) after exposure to environmental extremes (i.e. the highest percent of minus tides during daylight, high light regimes, desiccation, and solar bleaching), the populations differed in their morphologies and responses to increasing irradiance levels (P–I curve). Tidepool plants were the tallest, bushiest, and with increased diameter of cortical cells; while,high intertidal plants were the shortest, with sparse branching pattern and decreased diameter of cortical cells. Although their saturation irradiances indicated shade tolerance (Ik = 52 − 112 µmol photon m -2 s-1). their differential light saturation curves (P-I curves) suggested a capacity to acclimate to ambient light regimes. For example, plants from the high intertidal zone showed higher photosynthetic rates and saturation irradiances, slightly lower initial slopes of the P-I curves and levels of light harvesting accessory pigments, rphycoerhythrin (R-PE) and rphycocyanin (R-PC), after being exposed to higher light regimes. In contrast, plants from tidepools and shallow subtidal areas had lower photosynthetic rates and saturation irradiances, slightly steeper initial slopes of the P-I curves and levels of R-PE and R-PC, having been exposed to lower light regimes. During the rainy months (June to November) no significant responses in these parameters were recorded. Comparison of the P-I responses of vegetative and tetrasporic plants showed these to vary with season. The data suggest that when plants became reproductive their physiological fitness either was unchanged or slightly enhanced. These results indicate that all three populations of G. acerosa could be used as seed stock for mariculture.
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    Improvement of photosynthesis in dense microalgal suspension by reduction of light harvesting pigments (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 503-510 
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    ISSN: 1573-5176
    Keywords: Chlorella pyrenoidosa ; dense algalsuspension ; light-harvesting pigment ; photosynthesis ; Synechocystis PCC 6714
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of light-harvesting pigments (LHP) inmicroalgal cells on photosynthetic activity in adense cell suspension were examined. The results suggest that a lower LHP content should result in higher photosynthetic productivity under high light intensity. The idea was first proposed by Lien and San Pietro in 1975 that photosynthesis could be improved by reducing the LHP content in microalgal cells, but this has not been demonstrated in detail. Experiments to evaluate the idea were conducted with Synechocystis PCC6714 and Chlorellapyrenoidosa. In the experiments with PCC 6714, photosynthesis of a phycocyanin-deficient mutant was compared with that of the wild type. In the experiments with C. pyrenoidosa, the LHP content was controlled by the light intensity in the algalculture. The maximum photosynthetic activity was 20–30% higher in the dense suspension of cells having a lower LHP content with both organisms. These results indicate that the idea of reducing the LHP contentcould be applicable to a wide variety of photosynthetic organisms.
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    The interactive effects of UV-B radiation and a herbicide on uptake and allocation of carbon in two strains of the green algaScenedesmus (1997)
    Springer
    Aquatic ecology 31 (1997), S. 261-272 
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    ISSN: 1573-5125
    Keywords: sherbicide tolerance ; photosynthesis ; phytoplankton ; simetryn ; triazine ; herbicides ; ultraviolet radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the effects of UV B radiation on14C-uptake rates and carbon assimilation into the major end-products of photosynthesis of the green algaScenedesmus in the presence and absence of the triazine herbicide simetryn. Experiments were conducted using both a herbicide-susceptible and herbicide-tolerant strains ofScenedesmus. Three different UV-B dose rates were used as well as a light control. The lowest dose rate was almost the same level as in subsurface of ponds and lakes, while the other two were slightly lower and higher than natural sunlight on the surface of ponds and lakes, respectively. Total uptake rates of14C were not reduced by the UV B irradiation alone even at the highest dose rate. However, in the presence of the herbicide, uptake rates were clearly reduced by the highest dose rate of UV-B concomitant with increasing herbicide concentrations in the herbicide-susceptible strain. On the other hand, the proportion of lipid fraction was slightly reduced by all the UV-B treatments in the herbicide-susceptible strain even in the absence of the herbicide. In the herbicide-tolerant strain, uptake rates were not affected by UV-B radiation or by the herbicide. These facts indicated that UV-B effects could be smaller than predicted. It may be important to examine combined effects of UV-B and other anthropogenic and/or natural stresses for assessing actual UV-B effects in the field.
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    Seasonal and spatial patterns in phytoplankton photosynthetic parameters in a tidal freshwater river (1997)
    Springer
    Hydrobiologia 364 (1997), S. 199-208 
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    ISSN: 1573-5117
    Keywords: Phytoplankton ; photosynthesis ; light ; temperature ; tidal freshwater ; irradiance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic response to irradiance wasquantified for phytoplankton from the tidalfreshwater Potomac River biweekly to monthly over aperiod of six years. Samples were collected from twoshallow embayments and portions of the deeper rivermainstem. Photosynthetic rate was measured in thelaboratory at in situ temperature over a range ofirradiance levels and photosynthetic parameters werecalculated using nonlinear regression.PB max,the maximum photosynthetic ratestandardized to chlorophyll a, increased withtemperature up to 25 °C with a Q10 of 2.02. Above 25 °C, PB max was essentiallyconstant with temperature. Lesser correlationbetween PB max and ambient irradiance couldbe explained by the correlation of irradiance withtemperature. α, the slope of the P–I curve atlow light, was correlated with both ambientirradiance and temperature. Highest α valueswere found in late summer when high temperature andintermediate ambient irradiance were observed. Spring and early summer were characterized by lowα. Despite low light penetration, Ik andα values were indicative of sun limitationpossibly due to intermittent high light levelsexperienced during mixing. Ik showed a clearseasonal trend directly related to days from summersolstice. Spatial patterns were minimal except thatIk was consistently lower in one shallowembayment than in the other two areas. Seasonalpatterns in photosynthetic parameters correspondedroughly to changes from a spring diatom populationto summer cyanobacterial assemblage.
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    Gas exchange responses of a mangrove species, Avicennia marina, to waterlogged and drained conditions (1997)
    Springer
    Hydrobiologia 352 (1997), S. 39-47 
    Details
    ISSN: 1573-5117
    Keywords: Avicennia marina ; gas exchange ; mangroves ; photosynthesis ; waterlogging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was undertaken in summer on fully expanded leaves of Avicennia marina trees in the Beachwood Mangroves Nature Reserve, Durban,South Africa. Data sets were obtained over 5–7 days of relatively dry conditions and over two periods of 5 days during which the swamp was continuously inundated with dilute seawater (〈 150 mol m−3NaCl). Gas exchange responses were strongly influenced by photosynthetic photon flux density (PPFD), leaf temperature and leaf to air vapour pressure deficit (Δw). Carbon dioxide exchange was saturated at a PPFD of about 800 µmol m−2 s−1. Maximal CO2 exchange rates ranged from 8.5 to 9.9 µmol m−2 s−1 with no differences between drained and waterlogged conditions. Under drained conditions, leaf conductance,transpiration and internal CO2 concentrations were generally lower, and water use efficiencies higher, than during waterlogging. Continuous waterlogging for 5 days had no adverse effect on CO2 exchange. Xylem water potentials ranged from −1.32to −3.53 MPa during drained and from −1.02 to −2.65 Mpa during waterlogged conditions. These results are discussed in relation to anatomical and metabolic adaptations of A. marina to waterlogging stress.
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    Lumenal proteins involved in respiratory electron transport in the cyanobacterium Synechocystis sp. PCC6803 (1997)
    Springer
    Plant molecular biology 35 (1997), S. 407-416 
    Details
    ISSN: 1573-5028
    Keywords: cyanobacteria ; cytochrome oxidase ; electron transport ; photosynthesis ; respiration ; thylakoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyanobacterial thylakoids catalyze both photosynthetic and respiratory activities. In a photosystem I-less Synechocystis sp. PCC 6803 strain, electrons generated by photosystem II appear to be utilized by cytochrome oxidase. To identify the lumenal electron carriers (plastocyanin and/or cytochromes c 553, c 550, and possibly c M) that are involved in transfer of photosystem II-generated electrons to the terminal oxidase, deletion constructs for genes coding for these components were introduced into a photosystem I-less Synechocystis sp. PCC 6803 strain, and electron flow out of photosystem II was monitored in resulting strains through chlorophyll fluorescence yields. Loss of cytochrome c 553 or plastocyanin, but not of cytochrome c 550, decreased the rate of electron flow out of photosystem II. Surprisingly, cytochrome c M could not be deleted in a photosystem I-less background strain, and also a double-deletion mutant lacking both plastocyanin and cytochromec 553 could not be obtained. Cytochrome c M has some homology with the cytochrome c-binding regions of the cytochromecaa3 -type cytochrome oxidase from Bacillus spp. and Thermus thermophilus. We suggest that cytochrome c M is a component of cytochrome oxidase in cyanobacteria that serves as redox intermediate between soluble electron carriers and the cytochromeaa3 complex, and that either plastocyanin or cytochrome c 553 can shuttle electrons from the cytochrome b6f complex to cytochrome c M.
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    Can stomatal closure caused by xylem ABA explain the inhibition of leaf photosynthesis under soil drying? (1997)
    Springer
    Photosynthesis research 51 (1997), S. 149-159 
    Details
    ISSN: 1573-5079
    Keywords: abscisic acid ; t Acacia confusa ; t Leucaenaleucocephala ; photosynthesis ; soil drying ; stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of leaf water deficit and increase in endogenous ABA on photosynthesis of two tropical trees, t Acacia confusa and t Leucaena leucocephala, were investigated with two soil-drying methods, i.e. half or whole root system was subjected to soil drying. Half-root drying was achieved by allowing upper layer of soil column to dry and lower layer of soil column to remain watered. Half-root drying had little effect on leaf water potential, but when compared to the well-watered control, both methods of soil drying substantially increased the ABA concentration in xylem and reduced leaf conductance in both species. There was a significant relationship between leaf conductance and xylem ABA concentrations in both species, which was comparable to the same relationship that was generated by feeding ABA to excised twigs. The rate of photosynthesis was inhibited substantially in both soil-drying treatments and in both species, but photochchemical efficiency, measured as a ratio of variable fluorescence to a peak fluorescence emission of a dark-adapted leaf (Fv/Fm), was not reduced except in the whole root-dried t L. leucocephala plants where leaf water potential was reduced to –2.5 MPa. In all the cases where photosynthesis was inhibited, there was a concomitant reduction in both leaf conductance and calculated internal CO2 concentration. After two days of rewatering, leaf water potential and xylem ABA concentration rapidly returned to pre-treatment levels, but leaf conductance and photosynthesis of both whole-root and half root dried t L. leucocephala remained inhibited substantially. Rewatering led to a full recovery of both stomatal conductance and photosynthesis in soil-dried t A. confusa, although its photosynthesis of whole-root dried plants did not recover fully but such difference was not significant statistically. These results suggest that drought-induced decline of photosynthesis was mainly a result of the stomatal factor caused by the increase of ABA concentration in the xylem sap. Non-stomatal factors, e.g. reduced photochemical activity and/or carbon metabolic activity, were species-specific and were brought about only at very low water potential.
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    Regulation of photosynthesis in developing leaves of soybean chlorophyll-deficient mutants (1997)
    Springer
    Photosynthesis research 51 (1997), S. 185-192 
    Details
    ISSN: 1573-5079
    Keywords: CAB ; cytochrome f ; photosynthesis ; Rubisco ; Rubisco activase ; senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this report we examine the factors that regulate photosynthesis during leaf ontogeny in y3y3 and Y11y11, two chlorophyll-deficient mutants of soybean. Photosynthetic rates were similar during wild type and Y11y11 leaf development, but the senescence decline in photosynthesis was accelerated in y3y3. Photosynthetic rates fell more rapidly than chlorophyll concentrations during senescence in wild type leaves, indicating that light harvesting is not strongly limiting for photosynthesis during this phase of leaf development. Chlorophyll concentrations in Y11y11, though significantly lower than normal, were able to support normal photosynthetic rates throughout leaf ontogeny. Chlorophyll a/b ratios were constant during leaf development in the wild type, but in the mutants they progressively increased (y3y3) or decreased (Y11y11). In all three sets of plants, photosynthetic rates were directly proportional to Rubisco contents and activities, suggesting that Rubisco plays a dominant role in regulating photosynthesis throughout leaf ontogeny in these plants. The expression of some photosynthetic proteins, such as Rubisco activase, was coordinately regulated with that of Rubisco in all three genotypes, i.e. an early increase, coincident with leaf expansion, followed by a senescence decline in the fully-expanded leaf. On the other hand, the light harvesting chlorophyll a/b-binding proteins of PS II (the CAB proteins), while they showed a profile similar to that of Rubisco in the wild type and y3y3, progressively increased in amount during Y11y11 leaf development. We conclude that Y11y11 may be defective in the accumulation of a component required for LHC II assembly or function, while y3y3 has more global effects and may be a regulatory factor that controls the duration of senescence.
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    Recombinant Factor VIII SQ- Inactivation Kinetics in Aqueous Solution and the Influence of Disaccharides and Sugar Alcohols (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 1679-1684 
    Details
    ISSN: 1573-904X
    Keywords: solution ; protein stability ; factor VIII ; formulation ; kinetics ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To investigate the influence of various nonreducing disaccharides and sugar alcohols on the inactivation kinetics of recombinant factor VIII SQ (r-VIII SQ) in aqueous solution not containing albumin as a stabiliser. Methods. The stability of r-VIII SQ was followed using measurement of activity (VIII: C) and HPLC gel filtration at different temperatures. The thermal stability was investigated using differential scanning calorimetry (DSC). Results. The decline in VIII:C followed pseudo-first order kinetics. However, the Arrhenius plot was not linear for formulations without carbohydrate, demonstrating a distinct, reproducible curvature. The reaction rate at 5°C was faster than expected from the Arrhenius kinetics. The energy of activation (Ea) for formulations without added carbohydrates, derived from the linear part of the Arrhenius plot, varied between 77 and 86 kJ/mole in the temperature range 20−37°C. The addition of 600 mg/ml sucrose increased the Ea to 104 kJ/mole. DSC measurements showed thatTm′ was 64.2 ± 0.2°C for r-VIII SQ without stabiliser. This value increased linearly with increasing concentrations of carbohydrate. This stabilising effect is most probably explained by the theory of preferential hydration. Conclusions. The inactivation kinetics of r-VIII SQ in aqueous solution without addition of carbohydrates followed pseudo-first order kinetics but the Arrhenius plot was nonlinear. Sucrose and sorbitol both had highly stabilising effects on r-VIII SQ at concentrations above 300 mg/ml. The preparation containing 600 mg/ml sucrose was stable for at least 12 months at 5°C and 6 months at 25°C.
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    A Kinetic Study on Crystallization of an Amorphous Lubricant (1997)
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    Pharmaceutical research 14 (1997), S. 899-904 
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    ISSN: 1573-904X
    Keywords: amorphous material ; crystallization ; solid state reaction kinetics ; XRPD ; DSC ; microcalorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of the work was to study the crystallization kinetics of amorphous sterotex K at different temperatures and with different methods, and to compare the obtained kinetic and thermodynamic results. Methods. Isothermal microcalorimetry was the principal technique to determine the crystallization behavior of sterotex K. X-ray powder diffraction and differential scanning calorimetry were employed to interpret the microcalorimetric heat flow curves and compare the kinetics and the calculated value for the transition enthalpy. Results. The best way to analyze the x-ray diffractograms was the statistic Wakelin's correlation method. The method gave consistent quantitative results with microcalorimetry and both methods showed crystallization to consist of two partially parallel part-processes, which attached probably to the different growing rates of the forms consisting of different lattice planes having the same spacing. The quantitative analysis of differential scanning calorimetry scans was troublesome to perform but the obtained average value of −51 J/g for the enthalpy of the crystallization was in good agreement with the values obtained with the other methods, the average being −52 J/g. Calculating heat flow versus released energy plots from the microcalorimetric data the crystallization mechanism was observed to change as a function of temperature. Conclusions. A sensitive isothermal microcalorimeter can give precise and fast knowledge about possible solid state transition mechanism, but the source of the heat flow signal must be verified with other analytical methods to avoid incorrect conclusions. Due to the sensitivity and the real-time data the microcalorimetry can show up the mechanism of the transition for varying as a function of temperature and reveal the uselessness of the conventional Arrhenius relationship for extrapolations.
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    URL: http://dx.doi.org/10.1023/A:1012151900923
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    Biomass accumulation and allocation in soybean associated with genotypic differences in tolerance of nitrogen fixation to water deficits (1997)
    Springer
    Plant and soil 196 (1997), S. 101-113 
    Details
    ISSN: 1573-5036
    Keywords: drought ; Glycine max ; photosynthesis ; water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrogen fixation in soybean (Glycine max [L.] Merr.) is more sensitive to water deficits than many physiological processes and may therefore limit yield under nonirrigated conditions. Tolerance of nitrogen fixation to water deficits has been observed in the cultivar Jackson, however, the physiological basis for this is unclear. It was hypothesized that genotypes that could continue biomass production on limited soil water would prolong nitrogen fixation by continued photosynthate allocation to nodules. An initial greenhouse experiment compared biomass and N accumulation in six genotypes over an 8 d water deficit. Low stress intensity minimized genotypic expression of water-deficit tolerance; nevertheless, Jackson was clearly one of the most tolerant genotypes. In a second experiment, Jackson was compared to SCE82-303 at more severe stress levels. Biomass and N accumulation continued during water deficits for Jackson but ceased in SCE82-303. Individual nodule mass tended to increase during water deficits in Jackson and tended to decrease in SCE82-303, indicating greater allocation of photosynthate to Jackson's nodules in response to water deficits. Biomass accumulation of Jackson was contrasted with the USDA plant introduction (PI) 416937, which also has demonstrated tolerance to water deficits. For water-deficit treatments, total biomass accumulation was negligible for PI416937, but biomass accumulation continued at approximately 64% of the control treatment for Jackson. Transpirational losses for Jackson and PI416937 were approximately the same for the water-deficit treatment, indicating that Jackson had higher water use efficiency (WUE). Isotopic discrimination of 13C relative to12 C also indicated that Jackson had superior WUE during water deficits. Carbon-14 allocation in Jackson was compared to KS4895, a cultivar that was identified as sensitive to water deficits in an initial experiment. The comparison of water-deficit treatments of Jackson with KS4895 indicated that Jackson exported significantly greater amounts of14 C from labeled leaves and allocated approximately four times greater amounts of 14C per g of nodule. Results indicated that Jackson's sustained biomass production during water deficits resulted in the continued allocation of photosynthate to nodules and prolonged nitrogenase activity.
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    Does boron play only a structural role in the growing tissues of higher plants? (1997)
    Springer
    Plant and soil 196 (1997), S. 211-215 
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    ISSN: 1573-5036
    Keywords: boron ; deficiency ; function ; membrane ; mobility ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In species in which boron (B) mobility is limited, B deficiency only occurs in growing plant organs. As a consequence of the highly localized patterns of plant growth and the general immobility of B it has been extremely difficult to determine the primary function of B in plants. In species in which B is phloem mobile, the removal of B from the growth medium results in the depletion of B present in mature leaves. Thus, it is possible to develop mature leaves with increasingly severe levels of B depletion, thereby overcoming the complications of experiments based on growing tissues. Utilizing this approach we demonstrate here that B depletion of mature plum (Prunus salicina) leaves did not result in any discernible change in leaf appearance, membrane integrity or photosynthetic capacity even though B concentrations were reduced to 6-8 µg/g dwt, which is less than 30% of the reported tissue B requirement. Boron depletion, however, results in a severe disruption of plant growth and metabolism in young growing tissues. This experimental evidence and theoretical considerations suggest that the primary and possibly sole function of B, is as a structural component of growing tissues.
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    Effect of genome and ploidy on photosynthesis of wheat (1997)
    Springer
    Euphytica 94 (1997), S. 303-309 
    Details
    ISSN: 1573-5060
    Keywords: photosynthesis ; hexaploid wheat ; A genome ; D genome ; polyploidy ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We assessed (1) the effects of addition and doses of the D genome from different sources and (2) the addition of either the A genome or the D genome on the photosynthesis of synthesized hexaploid wheats. On average, the increased doses of the D genome reduced photosynthesis, but the depression was dependent on the source of the D genome. Two accessions of Aegilops squarrosa had depressed photosynthetic rates, but not another accession of Ae. squarrosa. The D genome of cv. Thatcher did not contribute to depress photosynthetic rate. Triticum monococcum had considerably higher photosynthetic rates than Ae. squarrosa. However, addition of the A genome from T. monococcum did not increase the photosynthetic rates of hexaploids. Chlorophyll a : b ratio, functional photosystem II and the core complex of photosystem II did not account for the variation in photosynthetic rate among the genotypes studied. In our experiment, photosynthesis of polyploids was not dependent on photosynthesis rates of the donor genomes.
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    Oceanic picophytoplankton having a high abundance of chlorophyll b in the major light harvesting chlorophyll protein complex (1997)
    Springer
    Photosynthesis research 53 (1997), S. 121-127 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll a/b light-harvesting complex ; major LHCP ; oceanic picophytoplankton ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chl a-containing, very small unicellular, eukaryotic phytoplankton (picophytoplankton) often become the dominant organisms near the bottom of the euphotic zone in the ocean, where light is limited, not only in intensity (about 0.5% of the surface irradiance), but also in quality (dominant in blue to green wavelengths). We have isolated picophytoplankton from subsurface waters (from 75 to 150 m in depth) of the Kuroshio area near Japan. EM observations showed that a single chloroplast occupies a large part of the cytoplasm. Some of the isolates have a flagellum. The major photosynthetic pigments found in these isolates were chlorophyll a and b. The light-harvesting chlorophyll a/b complex (LHCP) was isolated from three clones of picophytoplankton, one flagellated form (NIBB8001) and two coccoid forms (94B8100A and 94B5100C) . More than 50% of the total chlorophylls were recovered in the major LHCP fraction. A common feature of the major LHCPs isolated from the three picophytoplankton clones was a high abundance of chlorophyll b: the ratios of chlorophyll a to b were about 0.8, 0.7 and 0.6 for the clones NIBB8001, 94B8100A and 94B5100C, respectively. These values were very low compared with those in chlorophyll a/b-binding LHCIIs in higher plants and in the major chlorophyll a/b-binding LHCPs in microalgae (higher than 1.0). The major LHCP apoproteins of NIBB8001 and 94B5100C contained one major polypeptide; the apparent molecular masses analyzed with SDS-PAGE were about 22 kDa and 27 kDa, respectively. The major LHCP apoprotein of 94B8100A had two major polypeptides having apparent molecular masses of about 23 and 25 kDa. None of the thylakoid proteins cross-reacted with an antibody raised against the LHC IIα apoprotein of spinach. It is suggested that the high abundance of chlorophyll b in picophytoplankton, together with a large chloroplast in a small cell, enable them to utilize the reduced light in their habitat.
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    Chromophore assignment in phycoerythrocyanin from Mastigocladus laminosus (1997)
    Springer
    Photosynthesis research 54 (1997), S. 25-34 
    Details
    ISSN: 1573-5079
    Keywords: cyanobacteria ; energy transfer ; Fischerella PCC 7603 ; photosynthesis ; phycobiliprotein ; phycoerythrocyanin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The component spectra (maxima of absorption, circular and linear dichroism) of individual chromophores have been assigned for phycoerythrocyanin (PEC) trimer, monomer(s), and its subunits (α-PEC and β-PEC) by titration with p-chloromercury-benzene-sulfonate (PCMS), linear dichroism and photochemical transformations, as well as by deconvolution using a ‘bilin’ line-shape spectrum based on the α-84 phycoviolobilin-chromophore in the α-subunit. The level ordering PVB-α-84 → PCB-β-155 → PCB-β-84 is the same irrespective of aggregation. Two different monomers (αβ) were observed. In 4 M urea, the spectra are appropriately weighted sums of the subunit spectra, whereas in the monomer obtained in 1 M KSCN, both β-chromophores are red-shifted by 4–5 nm. Formation of trimer (αβ)_3gives considerable spectral changes: (1) the absorption is narrowed, which has been rationalized by excitonic coupling between neighbouring monomers, (2) the short wavelength part in the CD spectrum is missing and (3) a fourth band (+) at 528 in the LD spectrum appears. A deconvolution of the trimeric aggregation state using only the ‘bilin’ line-shape model is not possible.
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    Characterisation of cytochrome c6from Chlorella fusca (1997)
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    Photosynthesis research 54 (1997), S. 107-114 
    Details
    ISSN: 1573-5079
    Keywords: CD ; Chlorella ; cytochrome c6 ; EPR ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A c-type monohaem, cytochrome c6was isolated from a soluble extract of the green alga Chlorella fusca. The isolated protein shows an apparent molecular mass of 10 kDa by SDS-PAGE, but behaves as a dimer of 20.3 kDa in gel-filtration; the isoelectric point is 3.6. The N-terminal sequence shows high identity with other green algae cytochromes c6. The mid-point redox potential is about +350 mV between pH 5 and 9. The ferric and ferrous forms, and their pH equilibria, have been studied using visible, CD and EPR spectroscopies. The visible spectrum of the reduced cytochrome c6is typical of a c-type haem protein, with maxima at 274 nm, 318 nm (δ-peak), 416 nm (γ-peak), 522 nm (β-peak), 552–553 nm (α-peak). A 690 nm band, characteristic of a haem Met-His axial coordination of the haem group, is present in the oxidized form. At high pH values (≥ 8), cytochrome c6undergoes an alkaline transition, with a pKa of 8.7. Between pH 3 and 9 the EPR spectrum is dominated by two rhombic species, with g-values at 3.32, 2.05, 1.05 and 2.96, 2.30, 1.43, which interconvert with a pKaof 4. CD spectrum of Chlorella fusca cytochrome c6shows that the proteins must be mainly built up by α-helices. Even though there are similarities between Chlorella fusca cytochrome c6and that isolated from Monoraphidium braunii, no cross-reactivity with the antibodies raised against the Chlorella fusca cytochrome has been detected for the protein from Monoraphidium braunii.
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    The effects of elevated light on Photosystem II function: A thermoluminescence study (1997)
    Springer
    Photosynthesis research 54 (1997), S. 169-183 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence quenching ; photoinhibition ; photoprotection ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used the technique of thermoluminescence (TL) to investigate high-light-induced chlorophyll fluorescence quenching phenomena in barley leaves, and have shown it to be a powerful tool in such investigations. TL measurements were taken from wild-type and chlorina f2 barley leaves which had been dark-adapted or exposed to 20 min illumination of varying irradiance or given varying periods of recovery following strong irradiance. We have found strong evidence that there is a sustained trans-thylakoid ΔpH in leaves following illumination, and that this ΔpH gives rise to quenching of chlorophyll fluorescence which has previously been identified as a slowly-relaxing component of antenna-related protective energy dissipation; we have identified a state of the PS II reaction centre resulting from high light treatments which is apparently able to perform normal charge separation and electron transport but which is ‘non-photochemically’ quenched, in that the application of a light pulse of high irradiance cannot cause the formation of a high fluorescent state; and we have provided evidence that a transient state of the PS II reaction centre is formed during recovery from such high light treatments, in which electron transport from QAto QBis apparently impaired.
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    The modification of phytosterol profiles and in vitro photosynthetic electron transport of Galium aparine L. (cleavers) treated with the fungicide, epoxiconazole (1997)
    Springer
    Plant growth regulation 22 (1997), S. 93-100 
    Details
    ISSN: 1573-5087
    Keywords: epoxiconazole ; Galium aparine L. ; photosynthesis ; phytosterols ; thylakoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Foliar application of the triazole fungicide, epoxiconazole, retarded the growth of Galium aparine L. (cleavers). GC-MS and GC analysis clearly indicated that phytosterol biosynthesis in stem and leaflet tissue was significantly affected by this treatment. For example, in leaflet tissues, 125 g ai ha-1 (field rate) caused reductions in campesterol and sitosterol of 81percnt; and 75percnt; respectively. C14-methyl phytosterols such as 14agr;-methylergost-8-enol, obtusifoliol and dihydroobtusifoliol were detected in treated tissues indicating that epoxiconazole inhibits the cytochrome P-450 dependent obtusifoliol 14agr;-demethylase. In addition, ratios of campesterol to sitosterol were reduced. Stigmasterol was not detected in control or treated tissues. Preliminary determination of photosynthetic characteristics of isolated thylakoids from treated plants indicated that electron transport and oxygen evolution were impaired by epoxiconazole and these effects were dose-related. Ten days after treatment, oxygen evolution from thylakoids (determined as electron flow from water to ferricyanide) isolated from control plants was 24.2 micro;mol mg-1 chl h-1, whilst treatment with 125 g and 250 g ai ha-1 reduced this rate to 15.2 micro;mol and 8.2 micro;mol mg-1 chl h-1 an inhibition of 37 and 67percnt; respectively. These results suggest that epoxiconazole influences thylakoid integrity and function in addition to phytosterol biosynthesis in G. aparine.
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    The dependance of root growth potential on light level, photosynthetic rate, and root starch content in jack pine seedlings (1997)
    Springer
    New forests 13 (1997), S. 105-119 
    Details
    ISSN: 1573-5095
    Keywords: field performance potential ; photosynthesis ; Pinus banksiana ; root initiation ; root starch ; seedling testing ; total nonstructural carbohydrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Number of new roots (root growth potential or RGP), new root length, photosynthesis, total nonstructural carbohydrate content of needles and roots, terminal bud condition, and shoot elongation were measured on jack pine container seedlings for 4 weeks at weekly intervals under greenhouse conditions of 100%, 20%, and 10% sunlight to simulate competition-induced, lower light levels in the field. Both lower light levels significantly reduced photosynthetic rate, RGP, new root length, total nonstructural carbohydrate (especially starch) content of needles and roots, speed of terminal bud flush, and shoot growth. Both light level and photosynthetic rate were positively correlated with RGP and new root length, indicating that jack pine seedlings may use current photosynthate as an energy source to support new root growth. RGP and new root length were also both negatively correlated with root starch content suggesting that jack pine seedlings may also use stored carbohydrates as a potential carbon source for root initiation and initial root growth.
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    The mechanism of the degradation of psaB gene product, one of the photosynthetic reaction center subunits of Photosystem I, upon photoinhibition (1997)
    Springer
    Photosynthesis research 53 (1997), S. 55-63 
    Details
    ISSN: 1573-5079
    Keywords: hydroxyl radical ; light stress ; photosynthesis ; serine protease ; protein turnover ; reactive oxygen species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The psaB gene product (PsaB protein), one of the reaction center subunits of Photosystem I (PS I), was specifically degraded by light illumination of spinach thylakoid membranes. The degradation of the protein yielded N-terminal fragments of molecular mass 51 kDa and 45 kDa. The formation of the 51 kDa fragment was i) partially suppressed by the addition of phenylmethylsulfonyl fluoride or 3,4-dichloroisocoumarin, which are inhibitors of serine proteases, and ii) enhanced in the presence of hydrogen peroxide during photoinhibitory treatment, but iii) not detected following hydrogen peroxide treatment in the dark. These results suggest that the hydroxyl radical produced at the reduced iron-sulfur centers in PS I triggers the conformational change of the PS I complex, which allows access of a serine-type protease to PsaB. This results in the formation of the 51 kDa N-terminal fragment, presumably by cleavage on the loop exposed to the stromal side, between putative helices 8 and 9. On the other hand, the formation of the 45 kDa fragment, which was enhanced in the presence of methyl viologen but did not accompany the photoinhibition of PS I, was not affected by the addition of hydrogen peroxide or protease inhibitors. Another fragment of 18 kDa was identified as a C-terminal counterpart of the 45 kDa fragment. N-terminal sequence analysis of the 18 kDa fragment revealed that the cleavage occurred between Ala500 and Val501 on the loop exposed to the lumenal side, between putative helices 7 and 8 of the PsaB protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005852330671
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    Characteristics of photosynthetic carbon metabolism of spikelets in rice (1997)
    Springer
    Photosynthesis research 52 (1997), S. 75-82 
    Details
    ISSN: 1573-5079
    Keywords: lemma ; light-enhanced dark CO2 fixation ; palea ; panicle ; photosynthesis ; pyruvate ; Pi dikinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In lemmas and paleae of rice, the amount of pyruvate, Pi dikinase (PPDK) protein increased dramatically 6 d after anthesis and this change was consistent with that in the activity of PPDK. Since lemmas and paleae at this stage also showed high activities of the other marker enzymes of C4 pathway including phosphot enolpyruvate carboxylase (Imaizumi et al. (1990) Plant Cell Physiol 31: 835–843), photosynthetic carbon metabolism with lemmas at this stage were characterized. In a 14C pulse-12C chase study by photosynthetic CO2 fixation, about 35% and 25% of 14C fixed in lemmas were incorporated initially into 3-phosphoglycerate (3-PGA) and C4 acids, respectively. This suggests that lemmas participate mainly in C3-type photosynthetic metabolism, but that lemmas may also participate in the metabolism of C4 acids to some extent. To clarify this possibility, large amounts of 14C-labeled C4 acids were synthesized in vivo by a light-enhanced dark CO2 fixation (LED) method and the fate of 14C in C4 acids in the light was investigated. The percentage distribution of 14C in C-4 position of malate was about 90% and 83% after 10 s of photosynthetic 14CO2 fixation and 110 s of LED, respectively. Some of the 14C incorporated into C4 acids was transferred into 3-PGA and sugar phosphates. The possibility of direct fixation of CO2 by phosphot enolpyruvate carboxylase and metabolic pathway of CO2 released by decarboxylation of malate produced were discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005887931498
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    Growth at high CO2 affects the chloroplast number but not the photosynthetic efficiency of photoautotrophicMarchantia polymorpha culture cells (1997)
    Springer
    Plant cell, tissue and organ culture 48 (1997), S. 103-110 
    Details
    ISSN: 1573-5044
    Keywords: bryophytes ; cell culture ; chlorophyll content ; LHC II ; photosynthesis ; Rubisco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoautotrophic suspension cells of Marchantia polymorpha were grown at gas phase CO2 concentrations of 0.4% and 2.0%. At the higher CO2 concentration the chloroplast shape appeared to be modified and the cells had about 70% more chloroplasts per cell. Differences in chlorophyll content per cell were much less pronounced, indicating a reduction in chlorophyll content per chloroplast. Also the cell size was affected by the CO2 concentration, and our data suggest that it was about 37% lower in high CO2 grown cells than in low CO2 grown cells. The capacity and the efficiency of photosynthetic oxygen evolution on a chlorophyll basis and the photosystem II chlorophyll fluorescence parameters were almost identical in both cell types. Immunodection showed that also the ratio of light harvesting complex II antenna proteins and ribulose 1,5 bisphosphate carboxylase/oxygenase were unaltered. These data indicate that the chloroplast density within photoautotrophic culture cells may be regulated independently of their photosynthetic efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005893311140
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    Miscibility and gas permeability of poly(ethylene-co-5,4 mol^ 3,5,5-trimethylhexyl methacrylate)- polydimethyl-siloxane blends (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 86-90 
    Details
    ISSN: 1435-1536
    Keywords: Key words Poly(ethylene-co-5.4 mol% 3 ; 5 ; 5-trimethylhexyl methacrythlate) ; poly(dimethyl-siloxane) ; miscibility ; permeability ; dynamic elastic measurement ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Blends of poly(ethylene- co-5.4 mol% 3,5,5-trimethylhexyl methacrylate) (PE-TMHM) with poly(dimethylsiloxane) (PDMS) were prepared in the PDMS content range from 0 to 20%. The miscibility was studied for PE-TMHM–PDMS blends by DSC, dynamic mechanical and microscopic spectroscopy, and the gas permeability was measured for O2, N2 and CO2 as function of PDMS content. PE-TMHM and PDMS were partially miscible with each other below 20 wt% of PDMS content. The permeability coefficients (P) for O2, N2 and CO2 were increased by the blending of PDMS to PE-TMHM. The change of P for O2 with PDMS content well reflected the partially miscible phase separation behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050056
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    Cure kinetics of an epoxy system containing tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) and a multifunctional Novolac glycidyl ether cured with 4,4′-diaminodiphenylsulfone (DDS) (1997)
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 409-423 
    Details
    ISSN: 1572-8943
    Keywords: cure kinetics ; DSC ; etherification ; TGDDM epoxy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential scanning calorimetry (DSC) was applied to study the cure kinetics of an epoxy system containing both tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) and a multifunctional Novolac glycidyl ether resin, cured with 4,4′-diaminodiphenylsulfone (DDS). The experimental data were analyzed in terms of a mechanistic model proposed by Cole, which includes the etherification reaction. The kinetics can be completely described in terms of three rate constants, which obey the Arrhenius relationship. This model gives a good description of the cure kinetics up to the onset of vitrification. The effect of diffusion control was incorporated to describe the cure in the later stages. By combining the model and a diffusion factor, it was possible to predict the cure kinetics over the whole range of conversion, including an analysis of the evolution of different chemical species during the curing process. Good agreement with the experimental DSC data was achieved with this mechanistic model over the whole range of cure when the etherification reaction was assumed to be of first order with respect to the concentrations of epoxide groups, hydroxy groups, and the tertiary amine groups formed in the epoxide amine reaction.
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    URL: http://dx.doi.org/10.1007/BF01980501
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    Thermal and spectroscopic characterization of several derivatives containing a new organic ring system (1997)
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 665-683 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; DSC ; hydantion ; new ring ; tropane ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Several derivatives containing a new organic ring system, the tropane-6-spiro-5′-hydantoin structure (namely 8-alkyl-8-azabicyclo [3.2.1.] octane-6-spiro-5′-imidazoline-2′,4′-diones) have been characterized by thermal (DSC and simultaneous DTA-TG-DTG) and spectroscopic techniques (IR,1 H-NMR,13 C-NMR). X-ray powder diffraction and elemental analysis were applied for structural and molecular characterization. All the compounds melt in the range 160–250°C and undergo decomposition with progressive mass loss after the solid-liquid thermal transition with molecular degradation. It was found that tropane-6-spiro-5′-hydantoin derivatives with the hydantoin ring in β position are thermally less stable than those containing this ring in α position.
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    URL: http://dx.doi.org/10.1007/BF01979038
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    Developmental changes in carboxylase activities in in vitro cultured coconut zygotic embryos: comparison with corresponding activities in seedlings (1997)
    Springer
    Plant cell, tissue and organ culture 49 (1997), S. 227-231 
    Details
    ISSN: 1573-5044
    Keywords: carbon metabolism ; CO2 fixation ; embryo culture ; PEPC ; photosynthesis ; RubisCO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphoenolpyruvate Carboxylase (PEPC; EC: 4.1.1.31) and Ribulose 1,5-bisphosphate Carboxylase/Oxygenase (RubisCO; EC: 4.1.1.39) enzyme specific activities were measured during the in vitro development of coconut (Cocos nucifera L.) zygotic mature embryos into plantlets and compared with those of palms produced by conventional seed germination. At the time of initiation of germination, high PEPC and low RubisCO activities were measured in both cultured and conventionally germinated embryos, thus indicating an anaplerotic CO2 fixation. During both in vitro and in planta development, RubisCO progressively took over and became the main route for inorganic carbon fixation. The in vitro-grown coconut plantlets showed a faster decrease in their PEPC:RubisCO ratio than the seedlings, suggesting that an earlier transition from a heterotrophic to an autotrophic mode of carbon fixation takes place in the in vitro-derived material. Just before acclimatization, the RubisCO activity in in vitro-derived plantlets (2.83 µmol CO2h−1mg−1 TSP) was lower than that in seedlings (6.98 µmol CO2h−1mg−1 TSP) of the same age. Nevertheless, after acclimatization, RubisCO activities were comparable in both in vitro and in planta germinated material
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    URL: http://dx.doi.org/10.1023/A:1005856212846
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    The effect of different closure types, light, and sucrose concentrations on carbon isotope composition and growth ofGardenia jasminoides plantlets during micropropagation and subsequent acclimationex vitro (1997)
    Springer
    Plant cell, tissue and organ culture 47 (1997), S. 217-230 
    Details
    ISSN: 1573-5044
    Keywords: photoautotrophy ; photosynthesis ; shoot multiplication ; root induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth ofGardenia jasminoides Ellis plantlets and the development of photoautotrophy during two successive culture stages (shoot multiplication and root induction)in vitro was analyzed. We examined the effects of changes in growth conditions (type of tube closure, light, and sugar levels) on the development of photoautotrophy and growth during micropropagation and sought to establish whether they affected later acclimation to conditionsex vitro. During the two stagesin vitro, plantlets were grown in tubes under two different PPFD (50 and 110 µmol m−2 s−1), in media with three different sucrose concentrations (0, 1.5, and 3.0%, w/v) and with two different CO2 levels inside the tubes (controlled by either tightly closed caps or loosely sealed caps, and with an external CO2 concentration of 750 µmol mol−1). The development of photoautotrophy was assessed by determining the difference between the stable carbon isotope composition (δ13C) of sugar cane sucrose used as a heterotrophic carbon source and that of leaflets grownin vitro. Plantlets from the root-induction stage showed a more highly developed photoautotrophy than those from the shoot- multiplication stage. At both stages, utilization of closed caps was the treatment which most stimulated development of photoautotrophy in plantlets. Also, lowering PPFD or sucrose concentration induced a greater degree of photoautotrophic development, the strongest effect being observed in plantlets cultured inside loosely sealed tubes. During acclimationex vitro, plantlets taken from loosely sealed tubesin vitro performed better than those cultured inside tightly sealed tubes. The former, as well as recording a larger increase in fresh weight during this stage, also showed more negative δ13C in the newly developed leaves, which would seem to indicate a better water status during acclimation. Present results validate the usefulness of δ13C analysis of leaflets as a simple technique in assessing the development of photoautotrophy during culturein vitro. In addition, δ13C analysis can be extended to evaluate growth conditions during acclimation toex vitro conditions.
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    URL: http://dx.doi.org/10.1007/BF02318976
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    Activation and deactivation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in three marine microalgae (1997)
    Springer
    Photosynthesis research 51 (1997), S. 93-106 
    Details
    ISSN: 1573-5079
    Keywords: activation ; deactivation ; induction ; irradiance ; kinetics ; photosynthesis ; phytoplankton ; Rubisco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was examined in three marine microalgae: the chlorophyte t Dunaliella tertiolecta and the chromophytes t Pavlova lutheri and t Thalassiosira pseudonana. The three species differed in the sensitivity of Rubisco activity in crude extracts to magnesium ion concentration, the presence of protease inhibitors, the duration of the incubation on activity, and the potential for full activation of Rubisco with 20 mM magnesium chloride and 20 mM bicarbonate t in vitro. t D. tertiolecta had responses that were similar to those described in vascular plants: regulation of initial activity on a gradient of irradiances; maximum initial activities that were 80– 90% of light-saturated photosynthesis; total activities that exceeded light-saturated photosynthesis by 30–100%; and deactivation of Rubisco in darkness. Both initial and total activity declined in darkness and increased on a return to growth irradiance. First-order time constants were about 9 min for deactivation and 3 min for reactivation of initial activity. The decline in total activity after a transition into darkness could not be reversed t in vitro but could be reversed by exposing t D. tertiolecta to light, a characteristic of regulation by CA1P. The responses of t T. pseudonana were qualitatively similar, except that recovery of initial activity was low and could only account for 30–40% of light-saturated photosynthesis. Rubisco from t T. pseudonana exposed to low irradiance could be activated t in vitro but at growth irradiance and higher, total activity was lower than initial activity. The time constants for deactivation and reactivation of initial activity after reciprocal switches between growth irradiance and darkness were 12–18 min and 3 min in t T. pseudonana. t P. lutheri showed no regulation of Rubisco activity in response to changes in irradiance or light-dark transitions. This may have been an artifact of the conditions chosen to measure activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005755621305
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    Can photosynthesis respond to short-term fluctuations in atmospheric carbon dioxide? (1997)
    Springer
    Photosynthesis research 51 (1997), S. 179-184 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; FACE ; global change ; photosynthesis ; Photosystem II ; quantum yield ; quenching analysis ; rising CO2 concentration ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rapid and irregular variations of atmospheric CO2 concentrations (ca) occur in nature but are often very much more pronounced and frequent when artificially enriching CO2 concentrations in simulating the future atmosphere. Therefore, there is the danger that plant responses at elevated CO2 in fumigation experiments might reflect the increased frequency and amplitude of fluctuation in concentration as well as the increase in average concentration. Tests were conducted to determine whether the photosynthetic process could sense such fluctuations in ca. Instantaneous chlorophyll fluorescence (Ft) was monitored for wheat leaves (Triticum aestivum cv. Hereward) exposed to ca oscillating symmetrically by 225 μmol mol-1 about a ca set point concentration of 575 or 650 μmol mol-1. No Ft response was detected to half-cycle step changes in ca lasting less than two seconds, but at half-cycles of two seconds or longer, the response of Ft was pronounced. In order to determine the in vivo linear electron transport rate (J) the O2 concentration was maintained at 21 mmol mol-1 to eliminate photorespiration. J which is directly proportional to the rate of CO2 uptake under these conditions, was not significantly changed at half-cycles of 30 s or less but was decreased by half-cycles of 60 s or longer. It was inferred that if duration of an oscillation is less than 1 minute and is symmetrical with respect to mean CO2 concentration, then there is no effect on current carbon uptake, but oscillations of 1 minute or more decrease photosynthetic CO2 uptake in wheat.
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    URL: http://dx.doi.org/10.1023/A:1005804203928
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    Increases in the fluorescence Fo level and reversible inhibition of Photosystem II reaction center by high-temperature treatments in higher plants (1997)
    Springer
    Photosynthesis research 52 (1997), S. 57-64 
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    ISSN: 1573-5079
    Keywords: Fm ; high-temperature stress ; pheophytin a ; photosynthesis ; Qa ; spinach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of high temperatures on the fluorescence Fm (maximum fluorescence) and Fo (dark level fluorescence) levels were studied and compared with those of the photochemical reactions of PS II. These comparisons were performed during and after the high temperature treatments. The following results were obtained; (1) increases in the Fo level at high temperatures were partly reversible, (2) the Fm level in the presence of dithionite in spinach chloroplasts decreased at high temperatures and also showed a partial reversibility, (3) photoreductions of pheophytin a and Qa were reversibly inhibited at high temperatures parallel to the decrease in the difference between the Fm and Fo levels, and (4) the decrease in the fluorescence Fm level seemed to be related to denaturation of chlorophyll-proteins. All the data suggested that, as well as the separation of light-harvesting chlorophyll a/t b protein complexes of PS II from the PS II core complexes, partly reversible inactivation of the PS II reaction center at high temperatures is the cause of the increase in the Fo level.
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    URL: http://dx.doi.org/10.1023/A:1005884717655
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    A method for measuring whole plant photosynthesis in Arabidopsis thaliana (1997)
    Springer
    Photosynthesis research 52 (1997), S. 263-269 
    Details
    ISSN: 1573-5079
    Keywords: Arabidopsis ; chlorophyll fluorescence ; gas exchange ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurement of photosynthesis of intact leaves of Arabidopsis thaliana has been prohibitive due to the small leaf size and prostrate growth habit. Because of the widespread use of Arabidopsis for plant science research it is important to have a procedure for accurate, nondestructive measurement of its photosynthesis. We developed and tested a method for analysis of photosynthesis in whole plants of Arabidopsis. Net carbon assimilation and stomatal conductance were measured with an open gas exchange system and photosynthetic oxygen evolution was determined from chlorophyll fluorescence parameters. Individual plants were grown in 50 cubic centimeter tubes that were attached with an air tight seal to an enclosed gas exchange chamber for measurement of carbon dioxide and water exchange by the whole plant. Chlorophyll fluorescence from intact leaves was simultaneously measured with a pulse modulated fluorometer. Photosynthetic CO2 assimilation and stomatal conductance rates were calculated with established gas exchange procedures and O2 evolution was determined from chlorophyll fluorescence measurement of Photosystem II yield. Carbon assimilation and oxygen evolution in response to light intensity and ambient CO2 concentration was measured and is presented here to demonstrate the potential use of this method for investigation of photosynthesis of Arabidopsis plants in controlled environment conditions.
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    URL: http://dx.doi.org/10.1023/A:1005834327441
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    Multiple strategies for a high light existence in a tropical marine macroalga (1997)
    Springer
    Photosynthesis research 53 (1997), S. 149-159 
    Details
    ISSN: 1573-5079
    Keywords: Chlorodesmis fastigiata ; D1 protein ; fluorescence ; macroalgae ; photoinhibition ; photosynthesis ; Photosystem II heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acclimation to high light conditions on the top of coral reefs was examined in the coenocytic, filamentous green macroalga Chlorodesmis fastigiata (C. Ag.) Ducker. Despite having a pool of violaxanthin, high light does not induce formation of zeaxanthin in this macroalga. Exposure to 11 and 33% of surface irradiance resulted in parallel, reversible declines in Fv/Fmand in the number of functional PSII centers. The quantum requirement for PSII inactivation was calculated to be approx. 2×107photons. Recovery of PSII activity after low photon exposures did not depend on protein synthesis, unlike at higher photon exposures, where recovery was inhibited by 50% in the presence of lincomycin. Accumulation of inactive, quenching PSII centers is proposed as a mechanism of energy dissipation; only some of these centers require protein synthesis for reactivation. In natural-sized populations, midday photoinhibition was greater in filament tips than in bases, but the number of inactive PSII centers within entire filaments did not significantly change over the course of the day. It is proposed that the higher chlorophyll concentration in the tips provides protective shading to chloroplasts in lower regions, and that cytoplasmic streaming of chloroplasts within this siphonous alga limits the cumulative exposure to high light, thereby providing another level of protection from high light stress.
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    Mutation in a novel gene required for photomixotrophic growth leads to enhanced photoautotrophic growth of Synechocystis sp. PCC 6803 (1997)
    Springer
    Photosynthesis research 53 (1997), S. 243-252 
    Details
    ISSN: 1573-5079
    Keywords: cyanobacteria ; evolution ; glucose-sensitivity ; photoacclimation ; photosynthesis ; polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the glucose-tolerant strain of Synechocystis sp. PCC 6803, we found two types of cells with distinct growth properties. Under photoautotrophic conditions at any light intensity, one type gave larger colonies (designated WL) than the other (designated WS). Notably, the WL cells produced much larger colonies than the WS cells at higher light intensity. In contrast, growth of the WL cells was severely suppressed under mixotrophic conditions with glucose and light, while the WS cells grew normally. A gene which could complement the WL phenotype was obtained from a wild-type genomic library. The gene, designated pmgA, coded for a 23 kDa polypeptide of 204 amino acid residues with no apparent homology to known genes. In the WL genome, the base substitution of T for C at position 193 of pmgA caused replacement of Leu with Phe at position 65 of the product. The phenotype of pmgA disruption mutants was similar to that of the WL cells, indicating that the WS cells expressed a functional pmgA product. By direct sequencing of polymerase chain reaction-amplified pmgA from genomic DNA, it was revealed as an example of microevolution that WL had expelled WS from the photoautotrophic culture of wild-type in our laboratory for a year or so. Mixed culture in liquid also demonstrated that the WL cells increased gradually under photoautotrophic conditions, while they decreased rapidly under photomixotrophic conditions. These results suggest that pmgA product is essential for photomixotrophic growth, whereas it represses photoautotrophic growth. To our knowledge, the WL cells and pmgA-disrupted mutants are the first in cyanobacteria, which shows much improved photosynthetic growth than wild-type especially at high light intensity.
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    URL: http://dx.doi.org/10.1023/A:1005879905365
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    Foliar CO2photoassimilation and chloroplast linear electron transport rates in nitrogen-sufficient and nitrogen-limited soybean plants (1997)
    Springer
    Photosynthesis research 54 (1997), S. 209-217 
    Details
    ISSN: 1573-5079
    Keywords: ferredoxin, NADP photoreduction ; nitrogen limitation ; non cyclic electron transport ; photosynthesis ; Photosystem 1 and 2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaflets of soybean plants which are moderately inorganic nitrogen (N)-limited exhibit either no difference in the rate of net photosynthesis or as much as a 15–23% lower net photosynthesis rate per unit area than leaflets of N-sufficient plants [Robinson JM (1996) Photosynth Res 50: 133–148; Robinson JM (1997a) Int J Plant Sci 158: 32–43]. However, mature leaflets of N-limited soybean plants have a higher CO2photoassimilation rate per unit chlorophyll than leaflets of N-sufficient soybean plants at both moderate light intensity (≈500 µmol m-2s-1) and saturating light intensity (≈1200 µmol m-2s-1) [Robinson JM (1996) Photosynth Res 50: 133–148]. This study was undertaken to determine whether chloroplast thylakoids isolated from the leaflets of nitrogen-limited soybean plants displayed similar or higher linear electron transport rates (H2O → ferredoxin → NADP) per unit chlorophyll than thylakoids isolated from leaflets of N-sufficient plants. Chlorophyll concentration in reaction mixtures containing chloroplast thylakoids prepared from leaflets of N-limited plants was manipulated so that it was similar to the chlorophyll concentration in reaction mixtures of thylakoids prepared from leaflets of N-sufficient plants. Measurements of ferredoxin dependent, NADP dependent, O2photo-evolution in thylakoid isolates were carried out in saturating light (≈1500 µmol m-2s-1) and with $$NH_4^ + $$ (an uncoupler) in the chloroplast reaction mixtures. Chloroplast thylakoids isolated from N-limited soybean plant leaflets routinely had a 1.5 to 1.7 times higher rate of uncoupled, whole chain electron transport per unit chlorophyll in saturating light than did chloroplast thylakoids isolated from leaflets of N-sufficient plants. The results suggest that the photosystems and photosynthetic electron transport chain components are more active per unit Chl in leaflet chloroplast thylakoids of N-limited soybean plants than in thylakoids of N-sufficient plants.
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    URL: http://dx.doi.org/10.1023/A:1005995718710
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    Analysis of the chloroplast protein complexes by blue-native polyacrylamide gel electrophoresis (BN-PAGE) (1997)
    Springer
    Photosynthesis research 53 (1997), S. 35-44 
    Details
    ISSN: 1573-5079
    Keywords: b 6 f complex ; chloroplast ATP synthase ; light-harvesting complexes ; photosynthesis ; photosystems ; ribulose-bisphosphate carboxylase/oxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Blue-native polyacrylamide gel electrophoresis (BN-PAGE) is a powerful procedure for the separation and characterization of the protein complexes from mitochondria. Membrane proteins are solubilized in the presence of aminocaproic acid and n-dodecylmaltoside and Coomassie-dyes are utilized before electrophoresis to introduce a charge shift on proteins. Here, we report a modification of the procedure for the analysis of chloroplast protein complexes. The two photosystems, the light-harvesting complexes, the ATP synthase, the cytochrome b 6 f complex and the ribulose-bisphosphate carboxylase/oxygenase are well resolved. Analysis of the protein complexes on a second gel dimension under denaturing conditions allows separation of more than 50 different proteins which are part of chloroplast multi-subunit enzymes. The resolution capacity of the blue-native gels is very high if compared to 'native green gel systems' published previously. N-terminal amino acid sequences of single subunits can be directly determined by cyclic Edman degradation as demonstrated for eight proteins. Analysis of chloroplast protein complexes by blue-native gel electrophoresis will allow the generation of 'protein maps' from different species, tissues and developmental stages or from mutant organelles. Further applications of blue-native gel electrophoresis are discussed.
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    URL: http://dx.doi.org/10.1023/A:1005882406718
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    Determination of the quenching efficiency of the oxidized primary donor of Photosystem I, P700+: Implications for the trapping mechanism (1997)
    Springer
    Photosynthesis research 54 (1997), S. 237-240 
    Details
    ISSN: 1573-5079
    Keywords: fluorescence induction ; fluorescence yield ; photosynthesis ; P700 ; internal conversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005981016835
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    Responses of Rubisco activation and deactivation rates to variations in growth-light conditions (1997)
    Springer
    Photosynthesis research 52 (1997), S. 117-125 
    Details
    ISSN: 1573-5079
    Keywords: gas exchange ; light acclimation ; photosynthesis ; sunflecks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Basil (Ocimum basilicum) and impatiens (Impatiens wallerana) were grown in sun, shade, or fluctuating light (15 min sun, 15 min shade) to examine the effects of growth-light conditions on the rates of light-induced Rubisco activation and deactivation. Rubisco activation and deactivation rates were determined from gas-exchange measurements of photosynthesis following a step increase in PFD. Rubisco deactivation rates were also determined from biochemical analyses of leaf extracts. There were no significant differences in Rubisco activation rate among the growth conditions or between the two species. However, there were significant differences in Rubisco deactivation rate among the growth conditions in basil and between the two species. In basil, Rubisco deactivated more slowly following a decrease in PFD in sun- and fluctuating-light grown plants than in shade grown plants. Slower rates of Rubisco deactivation during periods at low PFD resulted in higher activation states at the onset of increased PFD. Thus, the contribution of Rubisco activation to the induction process was less for basil plants grown under sun and fluctuating light than for those grown under shade. Impatiens deactivated Rubisco more rapidly than in basil, but there was no substantial effect of the three growth-light conditions on Rubisco deactivation rates in impatiens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005847500471
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  • 95
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    Recovery of net CO2 assimilation after heat stress is correlated with recovery of oxygen-evolving-complex proteins in Zea mays L. (1997)
    Springer
    Photosynthetica 34 (1997), S. 13-20 
    Details
    ISSN: 1573-9058
    Keywords: D1 protein ; internal CO2 concentration ; maize ; oxygen evolution ; phosphoenolpyruvate carboxylase ; photosynthesis ; photosystem 2 ; ribulose-1,5-bisphophate carboxylase/oxygenase ; stomatal conductance ; thermotolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosystem 2 (PS2) in general, and the oxygen-evolving complex (OEC) in particular, is one of the most thermolabile components of photosynthesis. We examined the effects of heat stress on net photosynthetic rate (PN) and content of several stromal and thylakoid-membrane proteins (including OEC proteins) in maize (Zea mays L.) in order to determine if decreases in PN during, and especially after, heat stress were correlated with decreases in the content of OEC proteins. The PN decreased with heat stress in maize, and post-heat stress recovery of PN required 4 d following the second of two heat-shocks. The decrease in PN was not the result of stomatal closure. Cellular levels of the 33, 23, and 16 kDa OEC proteins decreased with heat stress, and the decreases were greatest and most closely correlated with decreases in PN for OEC16. Following the second heat stress, full recovery of OEC levels (especially OEC16 and 33) coincided with full recovery of PN, more so than with other photosynthetic proteins examined. For example, decreases in levels of the 32-kDa QB-binding protein of the PS2 reaction center (D1), ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit, and phosphoenolpyruvate carboxylase were generally smaller than for the OEC proteins and full recovery of these proteins occurred at least 2 d prior to full recovery of photosynthesis. These results are consistent with previous fluorescence and in vitro studies by others in suggesting that heat-relaed effects on PS2 and the OEC are an important limitation to Pn during heat stress. Additionally, these results suggest that heat-related decreases in the content of OEC proteins may limit post-heat stress recovery of carbon fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006899314677
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  • 96
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    Effect of cytokinins on the photosynthetic apparatus in water-stressed and rehydrated bean plants (1997)
    Springer
    Photosynthetica 34 (1997), S. 563-567 
    Details
    ISSN: 1573-9058
    Keywords: oxygen flash yields ; photochemical activity ; photosynthesis ; photosystem 2 ; thermoluminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of the cytokinins 6-benzylaminopurine (BAP) and N-2-chloro-4-pyridyl-N′-phenylurea (4-PU-30) on the photochemical activity, oxygen flash yields, and thermoluminescence in bean plants under a water stress were studied. The cytokinins increased the photochemical (Hill reaction) activity and thermoluminescence "B"-band in control as well as in stressed and rehydrated plants, while the oxygen flash yields were affected only in the stressed and rehydrated plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006821730974
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  • 97
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    Effect of fruiting and drought or flooding on carbon balance of apple trees (1997)
    Springer
    Photosynthetica 33 (1997), S. 269-275 
    Details
    ISSN: 1573-9058
    Keywords: Malus domestica ; open-top cuvettes ; photosynthesis ; respiration ; water stress ; water use efficiency ; xylem water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The response of fruiting or deblossomed trees to water stress such as drought or flooding was investigated in six semi open-top cuvettes each containing one apple (Malus domestica Borkh. cv. Golden Delicious) tree. Xylem water potentials of leaves dropped from -1.2 to -4.1 MPa within 7 d of drought, the effect being enhanced by fruiting. Apple trees without fruits showed smaller reductions in net photosynthetic rate (P N ) and dark respiration rate (R D ) after 2 d of drought and hence more positive carbon balances relative to fruiting trees. Flooding for 4 d had a more pronounced effect on P N than on transpiration, resulting in a reduced water use efficiency (WUE). This reduction in WUE was greater in the non-fruiting trees. Flooding reduced P N of the whole apple canopies irrespective of fruiting; aple trees without fruits increased R D resulting in a less positive carbon balance relative to fruiting trees. Fruiting increased the sensitivity to drought of apple trees (R D and P N ), but decreased their sensitivity to flooding (R D and WUE), suggesting different adaptation mechanisms for the two forms of water stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022172515878
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  • 98
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    Picosecond fluorescence decay studies on water-stressed pea leaves: energy transfer and quenching processes in photosystem 2 (1997)
    Springer
    Photosynthetica 34 (1997), S. 97-106 
    Details
    ISSN: 1573-9058
    Keywords: chlorophyll ; DCMU ; exciton-radical pair equilibrium model ; NH2OH ; photosynthesis ; Pisum ; quinones ; relative air humidity ; wilting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Detached leaves of pea (Pisum sativum) were submitted to water stress at different relative air humidities. The photosynthetic activity of photosystem 2 (PS2) was monitored by time-resolved picosecond chlorophyll (Chl) fluorescence spectroscopy. In the first days the well-known fast Chl fluorescence decay was observed which indicated high PS2 activity. After a few days the average fluorescence decay time τm reached a maximum, depending on the wilting conditions, but always at a relative loss of leaf mass of 80%. After this maximum, τm decreased within a few hours, the fluorescence decay became similar to that one of an intact leaf, but an additional fluorescence decay component with a lifetime of 3.6 ns appeared. At first the primary quinone QA was reduced due to inhibition of the electron transfer to the secondary quinone QB. Simultaneously, water deficiency caused an electron lack at the oxidizing site of PS2. This disabled the primary electron donor of PS2, tyrosine Z, from reducing the oxidized reaction centre of PS2 (P680+). Thus a recombination of P680+-pheophytin-QA- took place, and the energy was lost as heat. With further water stress, QA was decoupled from PS2. The new fluorescence decay component could therefore be assigned to energetically decoupled antenna complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006867902382
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  • 99
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    Short-term effects of aluminium at alkaline pH on the structure and function of the photosynthetic apparatus (1997)
    Springer
    Photosynthetica 34 (1997), S. 169-177 
    Details
    ISSN: 1573-9058
    Keywords: chlorophyll fluorescence ; chloroplast ultrastructure ; photosynthesis ; photosystem 2 ; Thinopyrum bessarabicum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 24 h exposure of the salt-tolerant grass Thinopyrum bessarabicum (Savul. and Rayss) A. Love seedlings to 1 mM aluminium (Al) in nutrient solution at pH of 9.0 resulted in a significant reduction of the biomass. In control samples the mesophyll chloroplasts exhibited the usual lens shape with most grana arranged in straight or slightly curving lines, and only 6.5 % of the grana were out of order. In Al-treated plants the mesophyll chloroplasts displayed a slightly distorted shape and distended size with most grana arranged in bow-like lines, while in the central region of the organelle as many as 26.7 % of the grana were independent and out of order in relation to the long axis. The morphological changes in the chloroplast shape and grana arrangement were probably due to swelling and distension of the chloroplasts in consequence to the altered membrane permeability. The initial in vivo chlorophyll (Chl) fluorescence FO, as well as the intermediate FI and peak fluorescence FP were increased under the Al stress: this indicated a destruction of photosystem (PS) 2 reaction centres and increased reduction of QA. The (FI-FO)/(FP-FO) ratio exhibited a significant increase indicating higher proportion of PS2 centres unable to reduce QB. Changes in the chloroplast ultrastructure seemed to be the reason of photosynthetic electron transport inhibition. Yet all these changes in the photosynthetic performance and chloroplast ultrastructure were considered as indirect effects of Al treatment since Al concentration in the leaves was undetectable. Disturbances in the chloroplast ultrastructure could be caused by a reduced uptake and/or transport of other nutrients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006880205108
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  • 100
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    Planting density effects on assimilation and partitioning of photosynthates during grain filling in the late-sown wheat (1997)
    Springer
    Photosynthetica 33 (1997), S. 199-204 
    Details
    ISSN: 1573-9058
    Keywords: photosynthates ; 14CO2 ; ear ; leaf insertion ; photosynthesis ; Triticum aestivum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf blades of the late-sown winter wheat produced the major portion, i.e., more than 60 %, of the total 14C-photosynthates at grain filling, but ear (rachis and glumes) only about 15 %, sheaths about 11 %, and stem internodes about 11 %. The change of plant density in this experiment had little influence on the 14CO2-photoassimilation of the ear (rachis and glumes), flag leaf lamina, sheaths and stem internodes, but markedly affected photosynthesis of the second, the third and lower leaves. The photosynthetic rate [expressed as specific radioactivity, s-1 kg-1(d.m.)] and the amount of 14CO2 photosynthates decreased significantly in the second, the third and other lower leaves at a high plant density. Upon grain-filling of the late-sown wheat, the grain was the major importer of photosynthates. Yet partitioning to the stem internodes depended on the plant density. Stem was the importer of photosynthates at a low plant density, but the exporter at a high plant density. In plants at a low plant density a fairly large proportion of photosynthates was distributed into the roots. The middle and lower above-ground parts of the late-sown wheat at a high plant density decreased or lost their function early. As a result, the plant senesced earlier. However, the grain setting, filling and yielding were restricted. An appropriately low plant density was suitable for prolonging the function of the middle and lower organs, delaying the senescence of plant, increasing the source supply for grain filling, and improving the grain yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022156112243
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