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  • oxidation  (98)
  • Photosynthesis  (83)
  • Springer  (181)
  • American Association for the Advancement of Science
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  • 1
    Digitale Medien
    Digitale Medien
    The Maillard reaction in vivo (1991)
    Springer
    European journal of nutrition 30 (1991), S. 29-45 
    Details
    ISSN: 1436-6215
    Schlagwort(e): advanced glycosylation endproducts (AGE) ; ag(e)ing ; aminoguanidine ; ascorbate ; autoxidation ; biomarker ; browning reaction ; chemical modification of proteins ; diabetes ; glycation ; glycoxidation ; nonenzymatic glycosylation ; oxidation ; Maillard reaction ; Aminoguanidin ; Ascorbat ; Autooxidation ; Biomarker ; Bräunungsreaktion ; chemische Veränderung vonProteinen ; Diabetes ; Glycosylierung ; Glycoxidation ; nichtenzymatische ; Glycosylierung ; Oxidation ; Maillardreaktion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Maillard- oder Bräunungsreaktion genannten Umsetzungen zwischen reduzierenden Zuckern und Eiweiß führen zur chemischen Zerstörung der Aminosäuren und zum Verlust der Proteinqualität während der Lebensmittelbearbeitung und -lagerung. Der vorliegende Beitrag zeigt Befunde auf, daß die Maillardreaktion auch im Gewebe des Menschen bei der Alterung von Proteinen mit langer biologischer Halbwertszeit auftritt. Die Konzentrationen an den sogenannten Amadori-Produkten, die im Initialstadium der Maillardreaktion aus Glucose und den Proteinen der Augenlinse oder dem Kollagen der Haut entstehen, erwiesen sich als relativ konstant, auch mit zunehmendem Alter. Die Produkte der Glycosylierung und nachfolgenden Oxidation der Proteine, auch Glycoxidationsprodukte genannt, häufen sich dagegen im Alter an, und zwar bei Diabetikern in vermehrtem Maße. Zu diesen Produkten gehören die Aminosäurenderivate N-(carboxymethyl)-lysin (CML), N-(carboxymethyl)-hydroxylysin (CMhL) sowie das fluoreszierende Quervernetzungsprodukt Pentosidin. Während diese Glycoxidationsprodukte in den Körpergeweben nur in Spuren vorkommen, gibt es deutliche Hinweise auf die Anwesenheit weiterer Bräunungsprodukte, deren Charakterisierung jedoch noch aussteht. Es werden Möglichkeiten zur „Entgiftung“ der reaktiven Zwischenprodukte aus der Maillardreaktion sowie zum Abbau extrem gebräunter Proteine diskutiert sowie neuere Möglichkeiten zur therapeutischen Modulierung fortgeschrittener Stadien der Maillardreaktion aufgezeigt.
    Notizen: Summary The Maillard or browning reaction between reducing sugars and protein contributes to the chemical deterioration and loss of nutritional value of proteins during food processing and storage. This article presents and discusses evidence that the Maillard reaction is also involved in the chemical aging of long-lived proteins in human tissues. While the concentration of the Amadori adduct of glucose to lens protein and skin collagen is relatively constant with age, products of sequential glycation and oxidation of protein, termed glycoxidation products, accumulate in these long-lived proteins with advancing age and at an accelerated rate in diabetes. Among these products are the chemically modified amino acids, Nɛ-(carboxymethyl)lysine (CML), Nɛ-(carboxymethyl)hydroxylysine (CMhL), and the fluorescent crosslink, pentosidine. While these glycoxidation products are present at only trace levels in tissue proteins, there is strong evidence for the presence of other browning products which remain to be characterized. Mechanisms for detoxifying reactive intermediates in the Maillard reaction and catabolism of extensively browned proteins are also discussed, along with recent approaches for therapeutic modulation of advanced stages of the Maillard reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01910730
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  • 2
    Digitale Medien
    Digitale Medien
    Leaf dynamics, self-shading and carbon gain in seedlings of a tropical pioneer tree (1995)
    Springer
    Oecologia 101 (1995), S. 289-298 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Leaf longevity ; Canopy structure ; Nitrogen allocation ; Self-shading ; Photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We examined leaf dynamics and leaf age gradients of photosynthetic capacity and nitrogen concentration in seedlings of the tropical pioneer tree, Heliocarpus appendiculatus, grown in a factorial design under controlled conditions with two levels each of nutrients, ambient light (light levels incident above the canopy), and self-shading (the gradient of light levels from upper to lower leaves on the shoot). Correlations among these parameters were examined in order to determine the influence of self-shading, and the regulation of standing leaf numbers, on leaf longevity and its association with leaf photosynthetic capacity. Leaf longevity and the number of leaves on the main shoot were both reduced in high light, while in the low light environment, they were reduced in the steeper self-shading gradient. In high nutrients, leaf longevity was reduced whereas leaf number increased. Leaf initiation rates were higher in the high nutrient treatment but were not influenced by either light treatment. Maximum-light saturated photosynthetic rate, on an area basis, was greater in the high light and nutrient treatments, while the decline in photosynthetic capacity in realtion to leaf position on the shoot was more rapid in high light and in low nutrients. Leaf longevity was negatively correlated among treatments with initial photosynthetic capacity. The leaf position at which photosynthetic capacity was predicted to reach zero was positively correlated with the number of leaves on the shoot, supporting the hypothesis that leaf numbers are regulated by patterns of self-shading. The negative association of longevity and initial photosynthetic capacity apparently arises from different associations among gradients of photosynthetic capacity, leaf numbers and leaf initiation rates in relation to light and nutrient availability. The simultaneous consideration of age and position of leaves illuminates the role of self-shading as an important factor influencing leaf senescence and canopy structure and dynamics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00328814
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  • 3
    Digitale Medien
    Digitale Medien
    Physiological and morphological variation in Metrosideros polymorpha, a dominant Hawaiian tree species, along an altitudinal gradient: the role of phenotypic plasticity (1998)
    Springer
    Oecologia 113 (1998), S. 188-196 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Key wordsMetrosideros polymorpha ; Phenotypic plasticity ; Photosynthesis ; Carbon isotope ratios ; Photosynthetic nitrogen use efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Metrosideros polymorpha, a dominant tree species in Hawaiian ecosystems, occupies a wide range of habitats. Complementary field and common-garden studies of M. polymorpha populations were conducted across an altitudinal gradient at two different substrate ages to ascertain if the large phenotypic variation of this species is determined by genetic differences or by phenotypic modifications resulting from environmental conditions. Several characteristics, including ecophysiological behavior and anatomical features, were largely induced by the environment. However, other characteristics, particularly leaf morphology, appeared to be mainly determined by genetic background. Common garden plants exhibited higher average rates of net assimilation (5.8 μmol CO2 m−2 s−1) and higher average stomatal conductance (0.18 mol H2O m−2 s−1) than their field counterparts (3.0 μmol CO2 m−2 s−1, and 0.13 mol H2O m−2 s−1 respectively). Foliar δ13C of most common-garden plants was similar among sites of origin with an average value of −26.9‰. In contrast, mean values of foliar δ13C in field plants increased substantially from −29.5‰ at low elevation to −24.8‰ at high elevation. Leaf mass per unit area increased significantly as a function of elevation in both field and common garden plants; however, the range of values was much narrower in common garden plants (211–308 g m−2 for common garden versus 107–407 g m−2 for field plants). Nitrogen content measured on a leaf area basis in common garden plants ranged from 1.4 g m−2 to 2.4 g m−2 and from 0.8 g m−2 to 2.5 g m−2 in field plants. Photosynthetic nitrogen use efficiency (PNUE) decreased 50% with increasing elevation in field plants and only 20% in plants from young substrates in the common garden. This was a result of higher rates of net CO2 assimilation in the common garden plants. Leaf tissue and cell layer thickness, and degree of leaf pubescence increased significantly with elevation in field plants, whereas in common garden plants, variation with elevation of origin was much narrower, or was entirely absent. Morphological characteristics such as leaf size, petiole length, and internode length decreased with increasing elevation in the field and were retained when grown in the common garden, suggesting a potential genetic basis for these traits. The combination of environmentally induced variability in physiological and anatomical characteristics and genetically determined variation in morphological traits allows Hawaiian M. polymorpha to attain and dominate an extremely wide ecological distribution not observed in other tree species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004420050367
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  • 4
    Digitale Medien
    Digitale Medien
    Different photosynthesis-nitrogen relations in deciduous hardwood and evergreen coniferous tree species (1995)
    Springer
    Oecologia 104 (1995), S. 24-30 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Leaf life-span ; Evergreen ; Deciduous ; Photosynthesis ; Nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The relationship between photosynthetic capacity (A max) and leaf nitrogen concentration (N) among all C3 species can be described roughly with one general equation, yet within that overall pattern species groups or individual species may have markedly different A max-N relationships. To determine whether one or several predictive, fundamental A max-N relationships exist for temperate trees we measured A max, specific leaf area (SLA) and N in 22 broad-leaved deciduous and 9 needle-leaved evergreen tree species in Wisconsin, United States. For broad-leaved deciduous trees, mass-based A max was highly correlated with leaf N (r 2=0.75, P〈0.001). For evergreen conifers, mass-based A max was also correlated with leaf N (r 2=0.59, P〈0.001) and the slope of the regression (rate of increase of A max per unit increase in N) was lower (P〈0.001) by two-thirds than in the broad-leaved species (1.9 vs. 6.4 μmol CO2 g−1 N s−1), consistent with predictions based on tropical rain forest trees of short vs. long leaf life-span. On an area basis, there was a strong A max-N correlation among deciduous species (r 2=0.78, P〈0.001) and no correlation (r 2=0.03, P〉0.25) in the evergreen conifers. Compared to deciduous trees at a common leaf N (mass or area basis), evergreen trees had lower A max and SLA. For all data pooled, both leaf N and A max on a mass basis were correlated (r 2=0.6) with SLA; in contrast, area-based leaf N scaled tightly with SLA (r 2=0.81), but area-based A max did not (r 2=0.06) because of low A max per unit N in the evergreen conifers. Multiple regression analysis of all data pooled showed that both N (mass or area basis) and SLA were significantly (P〈0.001) related to A max on mass (r 2=0.80) and area (r 2=0.55) bases, respectively. These results provide further evidence that A max-N relationships are fundamentally different for ecologically distinct species groups with differing suites of foliage characteristics: species with long leaf life-spans and low SLA, whether broad-leaved or needle-leaved, tend to have lower A max per unit leaf N and a lower slope and higher intercept of the A max-N relation than do species with shorter leaf life-span and higher SLA. A single global A max-N equation overestimates and underestimates A max for temperate trees at the upper and lower end of their leaf N range, respectively. Users of A max-N relationships in modeling photosynthesis in different ecosystems should appreciate the strengths and limitations of regression equations based on different species groupings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00365558
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  • 5
    Digitale Medien
    Digitale Medien
    Decreased ribulose-1,5-bisphosphate carboxylase-oxygenase in transgenic tobacco transformed with “antisense” rbcS (1993)
    Springer
    Planta 190 (1993), S. 332-345 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Light climate ; Nicotiana (photosynthesis) ; Photosynthesis ; Ribulose 1,5-bisphosphate carboxylase-oxygenase ; Transgenic plant (tobacco, antisense DNA)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Tobacco (Nicotiana tabacum L.) plants transformed with ‘antisense’ rbcS to decrease the expression of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) have been used to investigate the contribution of Rubisco to the control of photosynthesis in plants growing at different irradiances. Tobacco plants were grown in controlled-climate chambers under ambient CO2 at 20°C at 100, 300 and 750 μmol·m−2·s−1 irradiance, and at 28°C at 100, 300 and 1000 μmol·m−2·s−1 irradiance. (i) Measurement of photosynthesis under ambient conditions showed that the flux control coefficient of Rubisco (C infRubisco supA ) was very low (0.01–0.03) at low growth irradiance, and still fairly low (0.24–0.27) at higher irradiance. (ii) Short-term changes in the irradiance used to measure photosynthesis showed that C infRubisco supA increases as incident irradiance rises, (iii) When low-light (100 μmol·m−2·s−1)-grown plants are exposed to high (750–1000 μmol·m−2·s−1) irradiance, Rubisco is almost totally limiting for photosynthesis in wild types. However, when high-light-grown leaves (750–1000 μmol·m−2·s−1) are suddenly exposed to high and saturating irradiance (1500–2000 μmol·m−2·s−1), C infRubisco supA remained relatively low (0.23–0.33), showing that in saturating light Rubisco only exerts partial control over the light-saturated rate of photosynthesis in “sun” leaves; apparently additional factors are co-limiting photosynthetic performance, (iv) Growth of plants at high irradiance led to a small decrease in the percentage of total protein found in the insoluble (thylakoid fraction), and a decrease of chlorophyll, relative to protein or structural leaf dry weight. As a consequence of this change, high-irradiance-grown leaves illuminated at growth irradiance avoided an inbalance between the “light” reactions and Rubisco; this was shown by the low value of C infRubisco supA (see above) and by measurements showing that non-photochemical quenching was low, photochemical quenching high, and NADP-malate dehydrogenase activation was low at the growth irradiance. In contrast, when a leaf adapted to low irradiance was illuminated at a higher irradiance, Rubisco exerted more control, non-photochemical quenching was higher, photochemical quenching was lower, and NADP-malate dehydrogenase activation was higher than in a leaf which had grown at that irradiance. We conclude that changes in leaf composition allow the leaf to avoid a one-sided limitation by Rubisco and, hence, overexcitation and overreduction of the thylakoids in high-irradiance growth conditions, (v) ‘Antisense’ plants with less Rubisco contained a higher content of insoluble (thylakoid) protein and chlorophyll, compared to total protein or structural leaf dry weight. They also showed a higher rate of photosynthesis than the wild type, when measured at an irradiance below that at which the plant had grown. We propose that N-allocation in low light is not optimal in tobacco and that genetic manipulation to decrease Rubisco may, in some circumstances, increase photosynthetic performance in low light.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00196962
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  • 6
    Digitale Medien
    Digitale Medien
    Photosynthesis in an Australian rainforest tree, Argyrodendron peralatum, during the rapid development and relief of water deficits in the dry season (1987)
    Springer
    Oecologia 74 (1987), S. 441-449 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Rainforest ; Photosynthesis ; Transpiration ; Stomatal conductance ; Argyrodendron peralatum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Rates of apparent photosynthesis were measured in situ at five positions between the upper crown and a lower branch of a 34 m tall Argyrodendron peralatum (F.M. Bailey) H.L. Edlin ex I.H. Boas tree, and on an understorey sapling of the same species growing in a northern Australian rainforest. At the end of the dry season, rapid reductions in photosynthetic rates occurred in the upper crown within three days after a rain event, but changes in the lower crown and the sapling were less marked. Complete recovery of photosynthesis followed a second rain event. At high photon flux densities, stomatal conductance to water vapour decreased in a curvilinear fashion as the vapour pressure difference between leaf and air increased. Apparent photosynthesis was linearly related to stomatal conductance on the first clear day after each rain event, but there was no relationship between these parameters at the end of a brief natural drying cycle. Under conditions of adequate water supply, stomatal conductances of both upper crown and understorey leaves increased linearly with increasing photon flux density up to about 300 μmol m-2 s-1. During water deficits, stomatal conductances in leaves from the understorey increased much more rapidly at very low photon flux densities than did conductances in leaves from the upper canopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00378943
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  • 7
    Digitale Medien
    Digitale Medien
    Proton translocation during denitrification in Rhodopseudomonas sphaeroides f. denitrificans (1985)
    Springer
    Archives of microbiology 140 (1985), S. 358-364 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Denitrification ; Proton translocation ; Photosynthesis ; Rhodopseudomonas sphaeroides f. denitrificans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Proton translocation during the reduction of NO 3 - , NO 2 - , N2O and O2, with endogenous substrates, in washed cells of Rhodopseudomonas sphaeroides f. denitrificans was investigated by an oxidant pulse method. On adding NO 2 - to washed cells, anaerobically in the dark, an alkalinization occurred in the reaction mixture followed by acidification. When NO 3 - , N2O or O2 was added to cells in the dark or with these compounds and NO 2 - in light an acidification only was observed. Proton translocation was inhibited by carbonyl cyanide-m-chlorophenyl hydrazone. Valinomycin treated cells produced acid in response to the addition of either NO 3 - , NO 2 - , N2O or O2. The proton extrusion stoichiometry ( $$\vec H^ + /2e^ - $$ ratios) in illuminated cells were as follows: NO 3 - →0.5N2, 4.82; NO 2 - →0.5N2, 5.43; N2O→N2, 6.20; and O2→H2O, 6.43. In the dark the comparable values were 3.99, 4.10, 4.17 and 3.95. Thus, illuminated cells produced higher $$\vec H^ + /2e^ - $$ values than those in the dark, indicating a close link between photosynthesis and denitrification in the generation of proton gradients across the bacterial cell membranes. When reduced benzyl viologen was the electron donor in the presence of 1 mM N-ethylmaleimide and 0.5 mM 2-n-heptyl-4-hydroxyquinoline-N-oxide in the dark, the addition of either NO 3 - , NO 2 - or N2O to washed cells resulted in a rapid alkalinization of the reaction mixture. The stoichiometries for proton consumption, $$\vec H^ + /2e^ - $$ ratios without a permeant ion were NO 3 - →NO 2 - ,-1.95; NO 2 - →0.5 N2O,-3.03 and N2O→N2,-2.02. The data indicate that these reductions occur on the periplasmic side of the cytoplasmic membrane.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00446978
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  • 8
    Digitale Medien
    Digitale Medien
    Active transport of proline into washed cells of Rhodopseudomonas sphaeroides f. sp. denitrificans grown with nitrate (1986)
    Springer
    Archives of microbiology 144 (1986), S. 237-241 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Denitrification ; Proline transport ; Photosynthesis ; Chemical potential of proline ; proton motive force ; Rhodopseudomonas sphaeroides f. sp. denitrificans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Washed cells of Rhodopseudomonas sphaeroides f. sp. denitrificans, prepared from cultures grown anaerobically in light with NO 3 - as the terminal acceptor, readily incorporated [14C]-proline both in light and in the dark. The proline uptake was coupled to the reduction of either NO 3 - , NO 2 - , N2O or O2. Light stimulated the accumulation of proline in these cells. The addition of NO 3 - to washed cells in light decreased the K m for proline from 40 μM to 5.7 μM. Proline transport was inhibited by antimycin A, 2-n-heptyl-4-hydroxyquinoline-N-oxide both in light and in the dark with nitrate indicating that electron transfer from both denitrification and photosynthesis are involved in this uptake. Inhibition by carbonyl cyanide-m-chlorophenyl hydrazone and 2.4-dinitrophenol indicate that proline transport is energy dependent. The H+/proline stoichiometry increased from 1 to 2.5 when the external pH was increased from 6.0 to 8.0. Under these conditions Δμpro increased but Δp decreased markedly above pH 7.0.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00410954
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  • 9
    Digitale Medien
    Digitale Medien
    Salt relations of Dunaliella. Transitional changes in glycerol content and oxygen exchange reactions on water stress (1981)
    Springer
    Archives of microbiology 129 (1981), S. 154-159 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Compatible solute ; Dunaliella ; Glycerol ; Osmoregulation ; Osmotic shock ; Photosynthesis ; Respiration ; Salt stress ; Salt tolerance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Changes in glycerol content are reported for Dunaliella tertiolecta over an 8 h period after a salt stress or dilution stress. Under the experimental conditions, the new glycerol level was reached in about 30 min in light or dark but there was evidence of oscillations after that, particularly on dilution stress. Glycerol disappearance on dilution stress is caused predominantly by dissimilation. A salt stress immediately inhibited photosynthetic oxygen evolution and caused net oxygen uptake for a period of about 36 h after the stress. Oxygen evolution was reestablished after that and the process of recovery to the point of resumption of net evolution was not affected by conditions designed to inhibit protein synthesis. Dilution stress of comparable magnitude diminished but did not eliminate photosynthetic oxygen evolution and recovery to a pre-stress level took about 18 h. Effects of HCO 3 - concentration suggested that photorespiration was not the sole determinant of oxygen uptake induced by salt stress but it was not possible to apportion with confidence the contribution of mitochondrial and other types of respiration. There was no evidence that modification by stress of energy-induced proton fluxes across the plasma membrane constituted an osmoregulatory signal in either species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00455353
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  • 10
    Digitale Medien
    Digitale Medien
    Determination of kerogen type by using DSC and TG analysis (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 745-753 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; kerogen ; oxidation ; pyrolysis ; type determination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01996758
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