EVIDENCE FOR THE EXISTENCE OF MEMBRANE-ASSOCIATED PHYTOCHROME IN THE CELL

Abstract Comparative fluorescence and photochemical studies of phytochrome in etiolated seedlings of maize and in soluble and membrane-containing fractions isolated from them were camed out. The membrane fractions prepared in the absence of Mg²⁺ from etiolated coleoptiles contained 13% of total photoreversible phytochrome, which was readily solubilized by mild detergents. Its molecular size was indistinguishable from soluble phytochrome and equal to nondegraded maize phytochrome. Low-temperature fluorescence studies with intact tissue found that the position of the emission maximum at 85 K (λ_max) and the extent of the phototransformation of the red-absorbing form (Pr) into the first stable photoproduct, lumi-R, at 85 K (γ₁), varied in different parts of etiolated seedlings: λ_max and γ₁ reached their maximum values in the tips of coleoptiles and roots, 686 nm and 0.30–0.40, whereas the lowest values, 682 nm and ca 0.05, were observed in the root base. These parameters correlated well with those obtained for the pigment in the soluble and membrane-containing fractions: 684 and 680 nm, and 0.33 and 0.06, respectively. The extent of the Pr phototransformation into the far red-absorbing form (Pfr) (γ₂) did not differ much: values of 0.80–0.85 and 0.70–0.75 correlated with the high and low values of γ₁. These variations of the parameters were interpreted in agreement with our previous observations in terms of two phytochrome A species whose relative concentrations vary depending on the experimental conditions—the longer wavelength bulk light-labile species with high γ₁ (Pr″), and the shorter wavelength minor light-stable species with low γ₁ (Pr″). Close similarity between Pr’and the soluble phytochrome and between Pr″ and the membrane-bound phytochrome points to the possible origin of the native Pr’and PrPrime; species, thus providing evidence for the existence of membrane-bound pigment in the cell.     

Xyloketal G,a Novel Metabolite from the Mangrove Fungus <Emphasis Type="Italic">Xylaria sp.</Emphasis> 2508

A novel metabolite 1, named xyloketal G, was isolated from cultures of marine derived mangrove fungus Xylaria sp. 2508. Its structure was elucidated by analysis of spectroscopic data.__________Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 22–23, January–February, 2005.     

Absolutberechnung der Normalfrequenzen des Hydrogendifluoridions

Zusammenfassung Mit Hilfe eines einfachen quantenmechanischen Näherungsansatzes wird versucht, Bindungsabstände und Normalfrequenzen des Hydrogendifluoridions sowie des entsprechenden deuterierten Ions zu berechnen. Hierbei wird die Elektronenwechselwirkung der beiden Fluoridionen untereinander durch einen der Statistik entlehnten Ausdruck berücksichtigt. Die Methode liefert für die Abstände gute, für die Normalfrequenzen durchaus befriedigende Ergebnisse.

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On the basis of a quantum mechanical treatment the bond distances and the normal frequences of the hydrogen difluoride ion and its deuterated analogue are calculated. The electronic interaction of the two fluoride ions is approximated by a statistical calculation. The results are in fairly good agreement with the experimental values.

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Résumé Sur la base d'un traitement quantique simple, le calcul des distances de liaison et des fréquences normales est tenté pour l'ion de bifluorure d'hydrogène et son analogue deutéré. L'intéraction électronique des deux ions fluorures est approximée au moyen d'un calcul statistique. Les résultats sont en très bon accord avec les valeurs expérimentales.

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Der Deutschen Forschungsgemeinschaft danken wir für die Gewährung eines Stipendiums an Karl Hensen.     

Analyse von Kernresonanzspektren in Einkristallen niedriger Symmetrie. I

Zusammenfassung Es wird ein Verfahren beschrieben, das die Tensoren der Kernquadrupolkopplung und der paramagnetischen Hyperfeinstruktur in Einkristallen beliebiger Symmetrie aus Kernresonanz-messungen in mittleren Magnetfeldern zu bestimmen gestattet. Mögliche Anwendungen des Verfahrens in der paramagnetischen Elektronenresonanz werden diskutiert.

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A method is given, to determine the tensors of nuclear quadrupole coupling and paramagnetic hyperfine structure in single crystals of any symmetry from nuclear magnetic resonance measurements in intermediate fields. Possible applications in electron paramagnetic resonance are discussed.

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Résumé On décrit une méthode pour calculer les tenseurs de couplage quadripolaire nucléaire et de la structure hyperfme paramagnétique dans les monocristaux de toute symétrie, étant mesurées les résonances nucléaires dans les champs moyens. On discute l'application éventuelle de cette méthode a la résonance paramagnétique électronique.

     

High pressure μSR studies

The high pressureSR spectrometer [1] formerly located at CERN has been transferred to theE1-beamline at PSI and put back into operation with only minor modifications. The essential features of the high pressure apparatus are described below. The instrument covers a pressure range up to 0.7 GPa which can be extended to 1.4 GPa depending on the design of the high pressure cell. First measurements at PSI were successfully carried out with a single crystalline sample of Gd metal. New developments in high pressure cell design are presented. They are expected to further improve the signal/background ratio and to extend the pressure range to 1 GPa. One type of cell will allow temperatures above 380 K.This work was supported by the German Federal Minister for Research and Technology (Bundesminister für Forschung und Technologie [BMFT]) under Contract Nr. 03KA2-TUM-4 and 03SE3STU.     

The spin turning in ferromagnetic Gd studied by positive muons

We have studied the muon precession frequency in a ferromagnetic single crystal of Gd metal. The overall features of our findings are compatible with earlier results on polycrystalline material. In the temperature region between 245 and 220 K where the Gd magnetization starts to turn away from the c-axis, we observe an increase in the muon depolarization rate, and a complex precession signal which can be separated into two frequency components meaning that spin turning does not occur simultaneously in different parts of the sample (domains). From these more detailed data follows that previously obtained values forB _fc andB _dip can not both be correct. Two explanations for our new result are possible: EitherB _fc undergoes a change around 230 K which is directly coupled to the spin turning angle, or the value of the dipolar field contribution used in the earlier evaluation is too low. This imposes some uncertainty as to the value of the angle at the onset of spin turning derived fromSR frequencies.     

Chemical composition and reaction analysis of single aerosol particles

In situ measurements of gas-liquid surface reactions of single aerosol microdroplets are presented. By means of optical levitation in combination with elastic (Mie) and inelastic (Raman) light scattering it is possible to get information on the chemistry of e.g. acid/base reactions as well as the physical behavior of single microparticles.