Aufnahme von Spurenelementen Durch Ionenaustausch in Pflanzenzellen

Zusammenfassung Die starke Anreicherung von radioaktivem Zink durch lebende und tote Chlorella-Algen bei der Aufnahme aus Lösung wird durch Ionenaustausch gedeutet. Es handelt sich um einen passiven Prozeß, der keine Energie aus dem Stoffwechsel beansprucht. Bei den toten Algen ist die Einstellung von Gleichgewichten praktisch erreichbar; die Kapazität beträgt etwa 0,1 mval/g Frischgewicht. Durch Konkurrenz einer Anzahl zweiwertiger Ionen mit dem Radiozink wurde eine Affinitätsreihe für die toten Algen ermittelt. Diese Reihenfolge wurde für lebende Algen im wesentlichen bestätigt. (Nur wirkt Kupfer auf die lebenden Algen als Gift, und diese spezifische Wirkung wurde auch durch die Unterdrückung der aktiven Aufnahme von Radiorubidium gemessen.) Die Affinitätsreihe stimmt teilweise mit jener am Ionenaustauscher Amberlite IRC-50 überein, der durch Carboxyl-gruppen wirkt. Doch wird eine beschränkte Menge an Zink durch die Algen abnorm fest gebunden, und besondere Versuchsreihen führen zu der Annahme mindestens zweier Arten austauschender Zentren.

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The strong concentration of radiozine by living and dead algae (chlorella) from solutions is interpreted as being due to ion exchange. The process is passive and requires no metabolic energy. With dead algae, equilibria may be reached, and the capacity is of the order of 0.1 mval per gram fresh weight. An affinity series for dead algae has been established by competition of divalent ions with radiozinc. The series is essentially the same for living algae, except that copper acts as a poison; the toxicity of the copper has been demonstrated through the inhibition of radiorubidium uptake. The series of the affinities agrees partly with that of the ion exchanger amberlite IRC-50 that acts through carboxylic groups. However, a limited amount of zinc is bound abnormally strongly by the algae, and special experiments suggest the existence of at least two kinds of exchanging centres.

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Frau Prof. Dr.E. Cremer mit besten Wünschen gewidmet.     

Preparation and analysis of14C-lignin grass lignocellulose and DHP

(¹⁴C-lignin) grass lignocellulose was prepared from wheat seedlings injected with (¹⁴C-uniform) phenylalanine. Seedlings were injected 2 wk after germination and grown for 3–4 wk in a diurnal light cycle before harvesting. The plant material was ground in liquid N₂, extracted with hot water, benzene-ethanol, and ethanol, and treated with protease. Treatment of the lignocellulose with acid, alkali, and cellulase solubilized¹⁴C, which was analyzed by HPLC and TLC. Reverse-phase HPLC demonstrated that¹⁴C-ferulic and coumaric acid were bound primarily to carbohydrate and lignin, respectively. Gel permeation chromatography by HPLC of¹⁴C solubilized by treatment with 1M NaOH confirmed that the majority of the¹⁴C was incorporated into high molecular weight material. No¹⁴C was detected in either hexoses or pentoses obtained from the lignocellulose and only a minor amount was present as¹⁴C-phenylalanine. These studies show that (¹⁴C-lignin) grass lignocelluloses must be carefully characterized before being used as defined substrates for biodegradation studies. Coniferyl alcohol was synthesized by a route derived from those of Nakamura et al. (1974) and Nakamura and Higuchi (1976). DHP was then prepared by a modification of the method of Brunow and Wallin (1981) in which solutions of coniferyl alcohol and hydrogen peroxide were added alternately by a computer controlled HPLC system so that the coniferyl alcohol concentration was maintained below 1 mM throughout the synthesis. The DHP obtained was characterized by HPLC gel permeation chromatography and by NMR. The results of these analyses will be discussed.     

The new international reference system for pure α- and pure β-emitting radionuclides and some electron capture decaying radionuclides by liquid scintillation counting

Journal of Radioanalytical and Nuclear Chemistry - The Bureau International des Poids et Mesures (BIPM) is developing, with the support of national metrology institutes, an extension to the...     

Reactivity of Waterlogged Archeological Elm Wood with Organosilicon Compounds Applied as Wood Consolidants: 2D 1H–13C Solution-State NMR Studies

Some organosilicon compounds, including alkoxysilanes and siloxanes, proved effective in stabilizing the dimensions of waterlogged archaeological wood during drying, which is essential in the conservation process of ancient artifacts. However, it was difficult to determine a strong correlation between the wood stabilizing effect and the properties of organosilicon compounds, such as molecular weight and size, weight percent gain, and the presence of other potentially reactive groups. Therefore, to better understand the mechanism behind the stabilization effectiveness, the reactivity of organosilicons with wood polymers was studied using a 2D ¹H–¹³C solution-state NMR technique. The results showed an extensive modification of lignin through its demethoxylation and decarbonylation and also the absence of the native cellulose anomeric peak in siloxane-treated wood. The most substantial reactivity between wood polymers and organosilicon was observed with the (3-mercaptopropyl)trimethoxysilane treatment, showing complete removal of lignin side chains, the lowest syringyl/guaiacyl ratio, depolymerization of cellulose and xylan, and reactivity with the C6 primary hydroxyls in cellulose. This may explain the outstanding stabilizing effectiveness of this silane and supports the conclusion that extensive chemical interactions are essential in this process. It also indicates the vital role of a mercapto group in wood stabilization by organosilicons. This 2D NMR technique sheds new light on the chemical mechanisms involved in organosilicon consolidation of wood and reveals what chemical characteristics are essential in developing future conservation treatments.     

Standardization of an 55Fe solution using the TDCR method in POLATOM as part of the CCRI (II)-K2.Fe-55.2019 key comparison

Journal of Radioanalytical and Nuclear Chemistry - Measurements were made using the TDCR method. POLATOM prepared and distributed for the key comparison participants the 55Fe solution and 55Fe...     

Bilateral comparison of 14C activity measurements at the NCBJ RC POLATOM and the ENEA-INMRI

Journal of Radioanalytical and Nuclear Chemistry - A bilateral comparison of 14C activity measurements between ENEA-INMRI (Italy) and NCBJ RC POLATOM (Poland) was organized in the year 2015 and...