Copper effect on the protein composition of photosystem II

The definitive version is available at: http://www.blackwell-synergy.com/doi/full/10.1111/j.1399-3054.2000.1100419.xWe provide data from in vitro experiments on the polypeptide composition, photosynthetic electron transport and oxygen evolution activity of intact photosystem II (PSII) preparations under Cu(II) toxicity conditions. Low Cu(II) concentrations (Cu(II) per PSII reaction centre unit≤230) that caused around 50% inhibition of variable chlorophyll a fluorescence and oxygen evolution activity did not affect the polypeptide composition of PSII. However, the extrinsic proteins of 33, 24 and 17 kDa of the oxygen-evolving complex of PSII were removed when samples were treated with 300 μM CuCl2 (Cu(II) per PSII reaction centre unit=1 400). The LHCII antenna complex and D1 protein of the reaction centre of PSII were not affected even at these Cu(II) concentrations. The results indicated that the initial inhibition of the PSII electron transport and oxygen-evolving activity induced by the presence of toxic Cu(II) concentrations occurred before the damage of the oxygen-evolving complex. Indeed, more than 50% inhibition could be achieved in conditions where its protein composition and integrity was apparently preserved.This work was supported by the Dirección General de Investigación Científica y Técnica (Grant PB98-1632).Peer reviewe

Electrochemical synthesis of ammonia from wet nitrogen via a dual-chamber reactor using La0.6Sr0.4Co0.2Fe0.8O3−δ-Ce0.8Gd0.18Ca0.02O2−δ composite cathode

A La0.6Sr0.4Co0.2Fe0.8O3−δ-Ce0.8Gd0.18Ca0.02O2−δ composite cathode was used to investigate the electrochemical synthesis of ammonia from wet nitrogen. Wet nitrogen was flown through a dual chamber reactor under atmospheric pressure leading to the successful synthesis of ammonia. Ammonia was synthesised at a rate of 1.5 × 10−10 mol s−1 cm−2 at 400 °C when applying a dc voltage of 1.4 V, which is the highest reported to date. This rate is twice that of the observed ammonia formation rate (7 × 10−11 mol s−1 cm−2) when Co-free cathode, La0.6Sr0.4FeO3−δ-Ce0.8Gd0.18Ca0.02O2−δ was used as the cathode catalyst. A higher catalytic activity for ammonia synthesis may be obtained when using a catalyst with high oxygen vacancies, with the introduction of oxygen vacancies at the cathode being a good strategy to improve the catalytic activity of ammonia synthesis

Session 17 Ecophysiology

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Postharvest application of various chemical factors and their effects on quality characteristics and microbial load of raw beans (Phaseolus vulgaris L.)

The application of gibberellic acid (GA3), ascorbic acid (ASA) and olive mill wastewater (OMW) as spray was used as possible techniques for storage life prolongation and quality maintenance of bean (Phaseolus vulgaris L.) fruits at 20 and 5 °C. Control and OMW-treated beans displayed greater rates of O2 depletion and CO2 production. GA3-sprayed beans respired slower and revealed the lowest weight losses. Changes in glucose and fructose contents were less inhibited, while higher decrease under OMW treatment was recorded at both temperatures; total protein content profile did not change upon treatments. GA3 and ASA seem to be particularly effective in inhibiting enzymatic browning of beans. GA3 and ASA reduced the metabolic activity of moulds, while inducing the growth of yeasts as compared to the control. OMW-treated beans showed enhanced development of moulds and yeasts. The beneficial effect of GA3on bean shelf-life prolongation was shown; while the protective effect of ASA was only partial

COMPOSITIONAL CHANGES OF MAJOR CHEMICAL COMPOUNDS IN GREEK CAROB PODS DURING DEVELOPMENT

WOS: 000314400800003Because of the strong association with health benefits of some chemical compounds contained in carob fruit the composition of chemical substances of two common type carob pods (Ceratonia siliqua L.) and their changes during fruit developing in two periods of harvesting were reported. Samples were originated from a site near Rethymno, Crete Island, at an altitude of 100 m above the sea level. The moisture content determined through sample's drying in 70 degrees C under vacuum, sugars by HPLC (high pressure liquid chromatography), total polyphenols by ultraviolet/visible (UV/Vis) and fatty acids by gas chromatography (GC) in the fleshy and wild types were determined at three stages of development. Principal sugars found were glucose, fructose and sucrose. The predominant fatty acid was linoleic acid (n-6) followed by oleic, palmitic and then linolenic (n-3) fatty acids. The total unsaturated fatty acids content was two times higher than the content of total saturated fatty acids in fully-developed carob pod. The ratio n-6/n-3 was under 5, showing a good equilibrium between the two essential fatty acids. The fully developed fruits of both varieties revealed lower contents of polyphenols, proteins and sugars compared with their previous growth stages. The fleshy carob pods exceed the wild variety in concentration of proteins, sugars and fatty acids, while the wild variety exceeds the fleshy in polyphenols concentration

PHOTOSYNTHETIC CHARACTERISTICS OF CAROB TREE (CERATONIA SILIQUA L.) AND CHEMICAL COMPOSITION OF ITS FRUIT ON DIURNAL AND SEASONAL BASIS

WOS: 000311185700030The photosynthetic capacity of carob tree (Ceratonia siliqua L.) and the quality indices of the fruits growing under natural conditions, at Athens and Rethymno in Greece, were measured on diurnal and seasonal basis. The highest photosynthesis is observed during May compared to June and October, which is correlated well with the high developmental rates, the optimal temperatures and water availability. C. siliqua growing at Athens site attained higher photosynthesis parameters than trees growing in Rethymno. The decline of CO2 assimilation rate during the hot and dry season was rather a non-stomatal effect, since it is not accompanied by low stomatal conductance. Photoinhibition damage during June with concomitant reduction in electron transport rate in Photosystem 2 and Photosystem I may occur. Despite the low soil water and the extremely high air temperatures during the June, carob showed an important capacity to control water loss (A/gs). The total sugar content significantly increases with seasonal changes and reaches its highest value in October when pods are fully ripe, while polyphenols and proteins gradually decrease. The climatic conditions prevailing in the Mediterranean basin do not threaten the survival of C. siliqua.GSRTGreek Ministry of Development-GSRT; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)This work was done with the support from the GSRT and TUBITAK in the frame of Bilateral S&T Cooperation between Greece and Turkey