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The influence of temperatur and pressure on the fluorescence quantum yield of N-methylacridone (9,10-dihydro-9-oxo-10-methyl-acridine) in toluene in the range of 283-313 K and 1 bar to 2.5 kbar, respectively, has been investigated. Treatment of the data in terms of the Eyring transition-state theory leads to a consistent interpretation of the observed effect. The unusually large increase of the quantum yield with increasing pressure is attributed to a positive volume of activation, ⊿V≠, for the thermally activated S1-T2 intersystem crossing which is known to be the only deactivation process (of the Si-state) competing with fluorescence. Comparison of the values for ⊿H≠, the activation enthalpy of this process, determined at various pressures, indicates a decrease in ⊿H≠ at elevated pressures. Since ⊿H≠ can be associated with the S1-T2 energy gap involved in intersystem crossing, this result further confirms the conclusion that the change in Franck-Condon factors alone cannot account for the decrease in the intersystem crossing rate with increasing pressure.
Alkylating NAD-Analogs, Glyceraldehyde-3 Phosphate Dehydrogenase, Half-of-the-Sites Reactivity co-(3-Bromoacetylpyridinio)alkyldiphosphoadenosines with alkyl chain lengths of 2 -6 me thylene groups inactivate glyceraldehyde-3 phosphate dehydrogenase from rabbit muscle. Half-of-the-Sites reactivity is observed in each case: The analogs are covalently bound to highly reactive cysteine residues in two of the four subunits. The remaining two subunits still bind N AD and the reactive SH-groups, although modified by SH-reagents of low molecular weight are not labeled by any of the brominated coenzyme models. This behaviour may be explained by the assumption, that the modification of 2 subunits induces structural changes in the neighboured unoccupied subunits which prevent any attack on reactive cysteine residues caused by fixation and orientation of the bromoketo-coenzyme analog when bound to the active center. Structural similarities of the covalently bound coenzyme analogs in the active center and the native ternary GAPDH-NAD-substrate complex suggest that half-of-the-sites reactivity is a natural characteristic of the enzymes catalytic mechanism.
Membrane-Phloretin Interaction, Infrared Raman, ESR Spectroscopy The transport inhibitor phloretin was bound to human red cell membrane and the concomitant structural changes were observed by spectroscopic methods. By the spin labeling method a decrease in fluidity of the membrane was found at 1 and 10 |iM concentrations of the reagent. This result was obtained with the 2-(3-Carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl, and the 2-(14-Carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxyl lipid spin labels. Infrared spectroscopy of modified membranes revealed an intensity increase of the POO~ band at about 1250 cm-1. Moreover, a shift of the peak at 1050 cm -1 to 1100 cm-1 was observed in the presence of phloretin. Raman spectroscopy of the membranes did not contradict the results found with infrared and ESR spectroscopy: In the phloretin modified membrane we observed a lack of the band at 1085 cm-1, which leads to suggest that the POO" and/or C-C regions are less fluid. Changes of the extracted red cell membrane lipids were less characteristic, and the results differed from those found in red cell membrane.
1-anilino-naphthalene-8-sulfonate (ANS) fluorescence measurements have revealed that red blood cell membrane of the Rhnull type undergoes a transition at about 16 degrees C. In contrast, viscosity measurements of the extracted membrane lipids showed the usually observed transition at about 18 degrees C. Lower values of titratable sulfhydryl (SH) groups were observed in Rhnull membrane using 5,5'-dithiobis-(2-nitro-benzoic-acid) (Nbs2). In contrast, disulfide bonds in Rhnull membrane were estimated to be about 3 times the value of the controls. Spin labeling experiments using 2-(3-carboxypropyl)-4, 4 dimethyl-2-tridecyl 3-oxazolidinyloxyl were carried out with phospholipase A2 modified membranes. The mobile part of the spectra was significantly increased on the Rhnull membrane. In the presence of D-glucose, infrared spectrometry showed a larger reduction of the intensity of the POO-band in Rhnull membrane. In contrast to controls, binding of the reagent diethylpyrocarbonate resulted in no significant changes of the Rhnull membrane as determined by electron spin resonance (ESR) measurements. D-glucose transport activity was found to be at the upper level of a group of Rh positive and Rh negative persons. It is suggested that the intensity of the polar protein-lipid interaction is reduced in Rhnull membrane.
A thylakoid membrane preparation isolated from the blue-green alga Anacystis nidulans was freed from carboxysomes, soluble enzymes and the pigment P750 by floating in a discontinuous sucrose density gradient. In a buffer containing sucrose and the zwitterionic detergent Miranol S2M-SF the thylakoids were loaded on a linear 10-18% sucrose density gradient which also contained Miranol. The sedimentation yielded three bands, the lower two of which were green and the upper one was orange. The light green band in the middle of the gradient was the only one to show any photosystem II activity. This was measured as light-induced electron transport from diphenylcarbazide (DPC) to dichlorophenol-indophenol (DCPIP). The activity was sensitive to dichlorophenyl-dimethylurea (DCMU).
The red absorption maximum of the particles in this middle band - henceforth called photosystem II particles - was found at 672 nm and the maximum of their low temperature fluorescence emission spectrum at 685 nm upon excitation with blue light. Cytochrome b559 was the only cytochrome found in these particles; it was present at an average ratio of one molecule cytochrome per 40 -50 molecules chlorophyll a. C550 photoreduction with accompanying photooxidation of cytochrome b559 was also observed in the photosystem II particles. Good photosystem II preparations did not contain any detectable amounts of P 700.
By means of sodium dodecylsulfate polyacrylamide gel electrophoresis the polypeptide composition of the photosystem II particles was studied. Dissolution of the chlorophyll protein complexes was done under strongly denaturing conditions; consequently, no green bands were observed on the gels. The polypeptide pattern of the photosystem II particles showed two strong predominant bands of protein components with apparent molecular weights (app. mol. wts.) of about 50 000 and 48 000. These two bands are unique for photosystem II. Two other weaker bands were also found characteristic for photosystem II, the band of a polypeptide with an app. mol. wt. of 38 000 and that of a polypeptide with an app. mol. wt. of 31 000. Sometimes in addition the weak band of a polypeptide with the app. mol. wt. 27 000 was observed on the gel. The polypeptide 38 000 aggregated upon boiling of the sample in the presence of the denaturing agents prior to the electrophoresis, yielding an aggregate with an app. mol. wt. of 50 000. Additional polypeptides which were often found in the photosystem II particle preparation could be identified as subunits of the coupling factor of photophosphorylation CF1. None of the polypeptides described as characteristic for photosystem II are due to proteolytic activity.
As the observed photosystem II activity was found to be DCMU-sensitive it appears that the DCMU-binding protein is among the here described photosystem II polypeptides. Moreover, the authors have reason to believe that one of the major protein components found characteristic for photosystem II is cytochrome b559.
Synechococcus (Anacystis nidulans, strain L 1402-1) were grown at + 37 °C in an atmosphere of 0.04 vol.% CO2 using different light conditions. Changing the culture conditions caused alterations in pigment ratios and ultrastructure of Synechococcus. In comparison to the low white and red light grown cells under strong white light the number of thylakoids decreased and an accumulation of storage carbohydrates could be observed. The number of the polyhedral bodies also varied with culture conditions. The results are discussed with reference to the pigment composition and the function of the polyhedral bodies.
14C-and 15N-Assimilation, 15N-Labelled Amino Acids, M arine D iatom s The marine diatoms Bellerochea yucatanensis and Skeletonema costatum were grown at +20 °C in 0.03 vol.% CO2 with nitrate or ammonia. The 15N -am m onia and 15N -nitrate assim ila tion and 15N -incorporation into various amino acids were studied of both diatom s during exponential growth phase in dependence of different nitrogen conditions. In all experiments the 15N -am m onia uptake was lower than the 15N -nitrate assim ilation rate up to 20-40 min photo synthesis. N itrate lim itation -cells grown in nitrate followed by growth in nitrogen-free m edium for 24 h — caused a strong 15N-label into aspartate after adding 15NH 4C1 (1 m M). In cells grown in nitrate highest enrichment of 15N was found in glutamine. Results were discussed with reference to the operating of the GS/GOGAT system and glutam ic acid dehydrogenase pathway. Photosynthetic 14CO2 fixation experiments showed a very high labelling of aspartate which was interpreted with a phosphoenolpyruvate carboxylation catalysed by phosphoenolpyruvate carb-oxykinase.
The cyanobacterium Synechococcus (Anacystis nidulans strain L 1402-1) was grown at +35 °C in air and in air enriched with 2.2 vol.% CO2. The effect of different oxygen concentrations (0, 2, 20, 50, 75 and 99.97 or 97.8 vol.%) was studied in low (0.03 vol.%) and high (2.2 vol.%) CO2 concentrations at + 35 °C. After exposure to a nitrogen atmosphere and low CO2 content I4C-bicarbonate was mainly incorporated into aspartate and glycine/serine. During oxygenic photosynthetic CO2 fixation label in aspartate decreased and a high degree of radioactivity could be found in 3-phosphoglyceric acid and sugar monophosphates. The Calvin cycle was the main fixing pathway in 2.2 vol.% CO2 during anoxygenic and oxygenic conditions independent on the O2 concentrations during the experiments. No oxygen enhancement of photosynthetic CO2 fixation could be found. Possible mechanism involved in CO2 fixation pathways and glycolate metabolism underlying the effect of oxygen was discussed.
The growth of Synechococcus at different intensities of white and red light caused changes in the pigment composition. The ratio of chlorophyll a to phycocyanin varied from 1:8,2 in LWLI-grown cells to 1:1,4 in cells grown at HWLI and to 1:15,7 in cultures exposed to HRLI. Acyl lipids were quantitatively determ ined and fatty acids of the individual lipid classes analysed by GLC. Phycocyanin-free photosynthetic lam ellae were obtained by fractional centrifugation. No variation was found in the acyl lipid composition of the m em brane preparations. These all contained MGDG, DGDG, SQDG and PG as components. In all the lipids investigated, palmitic, hexadecenoic and octadecenoic acids m ade up to more than 90% of total fatty acids. The pattern of these major components w ithin the lipids from the different cultures depended on the light used. No large differences were detected between zones obtained from LWLI and HRLI isolated membranes, whereas density gradient centrifugation of those from HWLI-grown cells resulted in a completely different pattern of bands. The variations in lipid and fatty acid composition are discussed with respect to changes observed in lipid composition of whole cells and the results reported on tem perature dependent shifts in lipid fluidity in cyanobacteria.
The stereochemistry of the bisaboloids in chamomile-with the exception of bisabolol-oxide C-has been elucidated. The in-vitro-examination of the mutual convertibilities of some bisaboloids gave evidence for the stereochemical accordance of the common chiral centres of all the bisaboloids. The absolute configurations of the remaining third asymmetric carbon atoms in bisabololoxide A and B have been determined by NMR spectrometric studies in comparison with their unnatural semisynthetic epimers. All the stereogenic centres of the bisabololoxides A and B, of (-)-α-bisabolol and of bisabolonoxide A turn out to be S-configurated.
The diphenyls MPh2 (M = Be, Mg, Zn, Cd, Hg) have been reacted with pyrazine (Pz) in tetrahydrofuran. Only the magnesium derivative undergoes electron transfer to yield the 1:1 radical complex [Pz(MgPh)]·. However, in the presence of sodium or potassium persistent 1:2 complexes [Pz(MPh)2]+. are formed with M = Be, Mg, Zn. Use of the higher homologues CdPh2 and HgPh2 leads to reduction to the metals. The 1:2 complexes have been characterized by ESR spectroscopy; metal coupling constants of 9Be, 25Mg and 67Zn could be determined in natural isotopic abundance.
The alkyls MR3 (M = B, AI, Ga, In) react with pyrazine (Pz) and sodium in THF to yield persistent radical complexes Pz(MR2)2 · +MR4- (1). Use of TIR3 leads to rapid deposition of thallium metal. The formation of these ionic complexes 1 is the result of MR3 dissociation into +MR2 and -MR4 ions. All radicals have been identified and characterized by ESR; the data reveal the influence of back bonding in the boron derivative.
The compounds ;p-Me2P(X)-C6H4-P(X)Me2, X = O, S, Se, NPh undergo one-electron reduction at a mercury cathode or on reaction with solvated electrons in a K/18-crown-6/THF mixture. The radical anions formed are persistent and have been characterized by ESR. They may be described as complexes of the spin-bearing moiety p-Me2P-C6H4-PMe2 · with the coordinated groups X.
7-Dehydrocholesterol and ergosterol are oxidised by iodine and FeCl3 under "physiologically similar" conditions to highly reactive alkylating species. These can be trapped by nucleophiles, such as 1-methylimidazole.
The oxidation of the sterols to those alkylating species is discussed as a model-reaction for the first step in chemical carcinogenesis by endogene substrates.
The crystal structure of the high temperature phase of anilinium bromide, C6H5NH3⊕Br⊖ , was studied by X-ray and neutron diffraction at T = 343 K. The refinement supports disordered positions of the -NH3⊕ group. A split-atom model is proposed which includes disorder of the benzene ring. The thermal parameters, hydrogen bond distances, and other experimental data (NMR, NQR, inelastic neutron scattering) are in accordance with this model.
The crystal structure of the low temperature phase of anilinium bromide, C6H5NH3⊕Br⊖, was studied by neutron diffraction at T = 100 K. The refinement supports an ordered structure. The structures of the low and high temperature phases are compared and the mechanism of the phase transformation is discussed.
The application of laser induced fluorescence (LIF) in the uv to monitor tropospheric OH concentrations is limited for several reasons. In general the sensitivity of this method increases with the laser intensity. But at the low OH concentrations present in the atmosphere the beginning nonlinearity of the absorption (saturation effect) severely restricts the use of higher laser intensities. The high sensitivity of the LIF technique can be further compromised by the presence of an OH interference signal. This signal is generated by the monitoring laser light itself from laser photolysis of ambient ozone and the succeeding reaction of the photolysis product O (1D) with water to produce hydroxyl radicals. The results of the calculations are presented in a diagram from which the range of laser parameters can be deduced, which can be applied with confidence to monitor OH by the LIF method. The maximum number of signal counts for these working conditions is in the range of 10-3 per laser pulse.
The IR-spectra of BaCO3 (80% 13CO32-, 90% 13CO32-) shows small bands in the ν2-region, which are assigned to short waves of 12CO32--chains with three, five or six carbonate ions.
For a certain class of ocean models describing the exchange of inorganic carbon between the atmosphere and the surface layer of the ocean as well as between the surface layer and the deep sea the dynamical airborne fraction is evaluated analytically under the assumption that the growth rate of the atmospheric source term (fossil fuel plus net biogenic carbon input into the atmosphere) is slowly variable with time. Each of these models exhibits a certain uptake capacity of the deep ocean which is quantified. Considerations are made as to whether the terrestrial biota are to be regarded as a source or a sink for additional atmospheric CO2 depending on the modelling of the deep ocean. It is shown that a global one-dimensional box-diffusion ocean model with a depth dependent eddy diffusivity K(z) - K(0) exp[-z/z*], with an adjustable parameter set {K(0), z*}, provides a fairly well fit to the prebomb 14C ocean distribution and to an appreciable net biogenic carbon transfer into the atmosphere. The range of future atmospheric CO2 partial pressures is estimated for a given fossil input.
A large number of staphylinid beetles are closely associated with ants and termites (for review see Wilson 1971, Kistner 1979). Those species living with ants are commonly called myremcophiles. At least a few (Atemeles, Lomechusa) have "broken" the communication code of their host species and are thereby able to become completely integrated in the social system of the ants (Hölldolber 1967, 1970, 1971). In an attempt to understand the evolutionary pathways of this highly specialized social parasitic behavior, we studied closely related staphylinid species that do not live within the ant society but instead occupy the foraging trails and garbage dumps of an ant nest. ...