Volume 37, Issue 9

Nonlinear Polarisationoscillations To describe a metastable electric dipole state in a biological system, Fröhlich suggested a nonlinear model potential. In this paper we investigate a system of two nonlinear dipoles, which are coupled by a dipole-dipole interaction. We apply an external field and add linear damping terms. The external drive leads to a phase-locking of the dipoles. Mathematically, the system corresponds to an externally driven anharmonic oscillator with damping. We investigate the system of coupled oscillators and look for the stable and metastable solutions as a function of the internal and external parameters.

New results on the phytochemistry of Nephroma, a genus of the lichen family Peltigeraceae are presented. Further eight species occuring in South America have been studied. Including earlier results, nine groupings of secondary metabolites within the genus are defined: The phytochemistry of pattern I is represented by N. analogicum containing ergochromes (ergochrome AB and AA), hitherto found only in members of the Parmeliaceae; pattern II: tenuiorin, methylgyrophorate, gyrophoric acid, 4-O-methyl gyrophoric acid, methylevernate, lecanoric acid, zeorin and usnic acid (represented by N. gyelnikii and N. pseudoparile); pattern III: Zeorin, 15α-acetoxy-22- hydroxyhopane and 15α-22-dihydroxyhopane (represented by N. parile and N. expallidum); pat­tern IV: stictic, constictic, hypostictic, hyposalazinic and usnic acid, zeorin and one unknown depsidone [PQ 4] (represented by N. antarcticum and N. lobuligerum); pattern V: no lichen metabolites (represented by N. resupinatum and N. plumbeum); pattern VI: perlatolic, stenosporic and glomelliferic acid, zeorin and five further metabolites being most likely O-methyl-derivatives of stenosporic and perlatolic acid (represented by N. cellulosum and N. lepidophyllum); pattern VII: usnic acid and phenarctin, including three further unknown depsides (represented by N. microphyllum and N. kuehnemanii); pattern VIII: usnic acid, phenarctin, nephroarctin and zeorin (represented by N. arcticum); pattern IX: usnic acid and 6oc-7β-22-trihydroxyhopane (represented by N. chubutense). A considerable variation in accessory compounds exists in pattern II, IV and VI which does not correlate with the variation in morphological characters. N. patagonicum Kremp. is placed to synonymy with N. analogicum Nyl.

Laser microprobe mass analysis was explored as a method for the detection at the cellular level of the phytoalexin glyceollin in soybean cotyledons infected with an incompatible race of Phy- tophthora megasperma f. sp. glycinea. For LAMMA ® analysis 10 μm freeze microtome sections which were freeze-dried on copper grids were used. The LAMMA spectrum of glyceollin (isomer I) shows a characteristic peak at m/e = 321 which can be attributed to M-OH + . This peak was also present in the spectra of infected regions from a cotyledon but was completely absent in the spec­tra of uninfected tissue. One hundred and Fifty LAMMA spectra were taken along a line per­pendicular to the border line of infection. A steep rise in glyceollin content toward the infected area was observed. This is the First time that such highly localized glyceollin accumulation has been shown at the cellular level. The results show that LAMMA analysis is suitable for the de­tection of organic molecules in biological tissues with high lateral resolution.

Hydroperoxide lyase E" 2 solubilized with Tween 20 from tea chloroplasts was shown to catalyze cleavage reaction of 13-L-hydroperoxy-cis-9,trans-11-octadecadienoic acid (13-ʟ-hydroper- oxylinoleic acid) to hexanal, a C 6 -compound and 11-formyl-cis-9-undecenoic acid, a C 12 -compound by identification of cleavage products using authentic specimens synthesized through an unequivocal route. An oxygen-isotope effect was first observed in the cleavage reaction of 18 O- labeled 13-ʟ-hydroperoxylinoleic acid by solubilized E 2 ″ . The 18 O-atom of hydroperoxide was not detected in carbonyl group of hexanal formed from 18 O-labeled 13-ʟ-hydroperoxylinoleic acid.

car-Mutants of Pseudomonas rhodos were isolated and classified into four types according to their blockage in the biosynthetic pathway. A biosynthetic scheme could be established. Three new structures could be identified (4,4'-diapocarotene-4,4'-dial, 4,4'-diapocarotene-4-al-4'-oic acid, glucosyl-4,4'-diapocarotene-4-oate).

The representatives of the major algal divisions including Chlorophyta, Rhodophyta and Heterokontophyta usually show specific patterns of accumulated photoassimilatory products. Among these compounds, the accumulated low-molecular weight carbohydrates such as mono­saccharides, disaccharides, alditols (i.e. polyhydroxy alcohols) and heterosides are of particular interest. Comparative analyses based on photosynthetic 14 C-labelling provided sufficient evidence that occurrence and distribution of such compounds are in general indicative for particular algal taxa and in some cases useful biochemical parameters for a classiciation of lower taxa even at the ordinal or the generic levels.

Cell suspension cultures of soybean (Glycine max L.) were incubated with [ 14 C]-2,4- dichlorophenoxyacetic acid (62 h, 27 °C). The cells were converted to protoplasts by use of the cell-wall degrading enzymes, Driselase and pectinase. This procedure resulted in the release of the cellular amino acid conjugates as well as part of the free 2,4-dichlorophenoxyacetic acid and of the β-ᴅ- glucoside conjugates. A vacuole fraction was obtained by mild osmotic shock in 10% yield, and was characterized by its polypeptide composition. The purified vacuoles were enriched in β-ᴅ-glucoside conjugates, free 2,4-dichlorophenoxyacetic acid being only a minor vacuolar constituent, and amino acid conjugates not being detectable.

Galloyl-CoA, a potential intermediate in the biosynthesis of gallotannins, has been prepared via N-succinimidyl 4-O-β-ᴅ-glucosidogallate and 4-O-β-ᴅ-glucosidogalloyl-CoA. Besides a major absorption band at 261 nm, the UV-spectra of the purified thioester and its corresponding 4-O-glucoside contain a longer wavelenght absorption band due to the thioester linkage at 305 nm (galloyl-CoA) or at 290 nm (shoulder, glucosidogalloyl-CoA). The molar extinction coefficients ε of the two thioesters were determined via the iron-complex of 4-O-β-ᴅ-glucosidogalloyl hydroxamic acid; ε 261 -values of 19.5 × 10 6 [cm 2 mol -1 ] and 21.5 × 10 6 [cm 2 mol -1 ] were calculated for galloyl-CoA and its glucoside, respectively. Difference spectra, i.e. absorbance before esterolysis and after, revealed maximal absorption of the thioester bond at 310 nm (⊿ε = 7.4 × 10 6 [cm 2 mol -1 ]) for galloyl-CoA and at 282 nm (⊿ε = 7.2 × 10 6 [cm 2 mol -6 ]) for glu- cosidogalloyl-CoA. The two thioesters were further characterized by determining their half-lifes during hydroxylaminolysis and alkaline hydrolysis.

Dinitrogen fixation by crude extracts from Rhodopseudomonas palustris and Rhodomicrobium vannielii and by purified nitrogenase preparations from Azotobacter vinelandii and Clostridium pasteurianum is inhibited by nitrite, whereas in the same preparations nitrate is without effect. In Clostridium nitrite seems to interact with dinitrogenase reductase component of the bacterial nitrogenase complex.

The herbicide nitrofen was shown to act as an energy transfer inhibitor. The results proved nitrofen to act by inhibiting nucleotide exchange on the chloroplast coupling factor. A strong correlation was found between the inhibition of phosphorylation, ATPase activity, and nucleotide exchange. These results are discussed in terms of a regulatory effect of tightly bound ADP on the enzymatic activity of the chloroplast coupling factor.

Extracts from oat husks inhibit germination of a variety of seeds including Avena sativa L., Sorghum spec., Phalleris spec., Raphanus spec., Amaranthus caudatus, Lepidium sativum L. A quantitative assay for this inhibition was developed on the basis of percentage of root growth of Avena in the presence of extracted material compared with root growth of water controls. Fractionation of the extracts revealed that about half of the total inhibitory activity was found in the fraction of free organic acids. The inhibition was not due to known inhibitors. Abscisic acid. was not found in this extract. Phenole carbonic acids were determined in the extract. Their con­centration was too low to significantly contribute to the observed inhibitory activity.

Extracts from oat husks which inhibit germination of a variety of seeds were fractionated. After mild alkaline hydrolysis, two active fractions A 1 and A 2 were obtained. From A 1 which contains mainly aliphatic di- and tricarboxylic acids, the inhibitor was isolated by chromatographic procedures and identified as 1,3,4-pentanetricarboxylic acid (11 b) by mass spectrometry. The structure was confirmed by total synthesis of the compound in the form of a mixture of diastereomers 11 a/11 b. From A 2 , two aromatic compounds were isolated by chromatography and identified by gas chromatography and mass spectrometry as 3,4-dimethoxyacetophenone (12) and dimethoxybutylbenzene. Compounds with similar structures were compared with the natural germination inhibitors with regard to their bioactivity.

Erythroleucemic cells of rats were induced by DMSO for the terminal erythroid differentia­tion. The base composition and the 5MC content of the DNA were analyzed by HPLC and a significant difference between non-induced and induced cells was not found. The analysis of labelled DNA by the restriction enzymes Hha I, Hpa II, and Msp I did not result in a different pattern before and after the induction. These results suggest that the 5 MC content of the DNA does not change during the induced terminal erythroid differentiation.

We report on the enzymatic degradation of 14 C-labelled 5',5"-linked dinucleoside triphosphates Gp 3 A, 2-O-mGp 3 A, 2'dGp 3 A, 2',3"ddGp 3 A and m 7 Gp 3 A in rat liver nuclei. The 2'-desoxy- and 2',3'-didesoxy compounds are poorer substrates than the other cap-structured dinucleotides in­vestigated.

The binding of Hg 2+ and 3,6-bis-(acetatomercurimethyl)-dioxane (BAMD) to sonicated calf thymus DNA was studied by small-angle X-ray scattering and viscosity measurements. The scat­tering experiments with DNA complexed by different amounts of mercurials (for Hg 2+ r b = 0-0.79, for BAMD r b = 0-0.86 mol of mercurial bound per mol of base pairs) established that the rod-like character of the DNA molecules is maintained up to high binding ratios. They revealed further a steady decrease of the cross-section radius of gyration R c for the DNA · Hg 2+ complex and a similar decrease of R c for the DNA · BAMD complex up to r b = 0.35. This behav­iour is certainly caused by the incorporation of both mercurials near the axis of the DNA helix. Binding of BAMD at r b > 0.35 led to an increase of R c which behaviour obviously reflects the lo­cation of mercury atoms at large distances from the axis, possibly on the surface of the helix. The increase of the mass per unit length M c upon binding of the mercurials was found to be much higher than expected. This finding established that the length of the DNA helix decreases by 0.10±0.01 nm per bound mercurial at low binding ratios (i.e. up to r b = 1/3 for BAMD, up to possibly r b = 0.5 for Hg 2+ ). A similar conclusion was also drawn from the observed decrease of intrinsic viscosity [rj] with increasing r b . The analysis of M c at high binding ratios suggests that every BAMD molecule bound beyond r b =1/3 decreases the length of the DNA by 0.21 ±0.05 nm whereas Hg 2+ when bound beyond r b = 0.5 causes no change of the length.

Centrifugal elutriation was applied to separate into the cell compartments asynchronous Ehrlich ascites cells grown under different culture conditions. The cytokinetic properties of the recultivated fractions were studied by flow cytometry. The present experiments prove that G 1- cohorts grown 12 h under exclusion of oxygen accumulate in the late G 1-compartment. The cyto­kinetic properties of these cells are not changed. In contrast the cytokinetic properties of anaerobically treated S-phase cells are changed; most of S-cells leave the cell cycle after they have attained the DNA content of G 2-cells and continue to synthesize DNA without preceeding division. Cells with a DNA content up to the fourfold of normal values are found.

In larval and pupal stages of several insect species the changes in total body metabolism appear to be inversely proportional to the course of ecdysteroid titres. The largest peaks of ecdysteroid occur exactly at the time of the lowest metabolic rates. These relationships are consequences of the developmental programming; ecdysteroid has no direct antimetabolic action. The problem of ecdysteroid-metabolic interactions has been discussed in relation to possible homeostatic function of ecdysteroids in insect development.

Periplasmic aminopeptidase II of yeast was isolated from protoplast supernatants by ammonium sulfate precipita­tion, DEAE-Sephacel chromatography and affinity chromatography on immobilized bestatin. This isolation method is more rapid than conventional procedures and, in addition, avoids contact of the enzyme with yeast protein-ases. Thus the preparation obtained is likely to represent the native periplasmic from of aminopeptidase II.