Apocarotenoids in the sexual interaction of Phycomyces blakesleeanus

A simple genetic test allowed us to carry out the first systematic study of the apocarotenoids in the Mucorales. We have identified 13 apocarotenoids in the culture media of the fungus Phycomyces blakesleeanus (Mucoromycota, Mucorales). Three of these compounds were novel apocarotenoids: (2S,8R,E)-8,14-epoxycyclofarnesa-4,6,9-triene-2,11-diol (6), (2S,6E,8E)-cyclofarnesa-4,6,8-triene-2,10,11-triol (7), and its 6Z isomer (8). Four of the remaining compounds have been reported previously from this fungus and six from other Mucorales. All of them belong to three families, the 18-carbon trisporoids, the 15-carbon cyclofarnesoids, and the 7-carbon methylhexanoids, derived from the three fragments that result when β-carotene is cleaved at its 11',12' and 12,13 double bonds. The apocarotenoids were more varied and more abundant in mated cultures of strains of opposite sex than in single cultures. The presence of acetate in the medium blocked the production of many apocarotenoids while having little effect on the concentrations of the remaining ones.     

Altered flavin patterns in photobehavioral mutants of Phycomyces blakesleeanus.

Flavins were extracted from sporangiophores of the lower fungus Phycomyces blakesleeanus and identified by HPLC with fluorescence detection. In the wild-type strain NRRL1555 they were found to be present at the following concentrations: riboflavin (5.5 x 10(-6) M), flavin mononucleotide (FMN) (4.0 x 10(-6) M) and flavin adenine dinucleotide (1.4 x 10(-6) M). The HPLC elution profiles of the wild type were compared to a set of behavioral mutants (genotype mad) with specific defects in their light-transduction pathway. The photoreceptor mutants C109 (madB), C111 (madB) and L1 (madC) had normal amounts of flavins. The most prominent changes were found in single mutants with a defective madA gene which contained about 25% of riboflavin and about 10% of FMN and FAD normally found in the wild type. A hypertropic mutant with a defective madH gene contained instead 80% of riboflavin and 120% of FMN and FAD. The double mutant L52 (madA madC) and the triple mutant L72 (madA madB madC) had normal amounts of FAD and FMN. This indicates that the madC mutation, which itself causes loss of light sensitivity and which affects the near-UV/blue-light receptor (Galland and Lipson, 1985, Photochem. Photobiol. 41, 331-335) functions as a restorer of the flavin content in a genetic madA background. The double mutant L51 (madA madB) had about 40% of FMN and FAD, suggesting that the madB mutation functions as a partial restorer of flavin content. The photogravitropic thresholds (450 nm) reported for the wild type and the madA and madH mutants were positively correlated to the endogeneous concentrations of FMN and FAD.(ABSTRACT TRUNCATED AT 250 WORDS)     

Altered pterin patterns in photobehavioral mutants of Phycomyces blakesleeanus.

Pterins were extracted with methanol from sporangiophores of the lower fungus Phycomyces blakesleeanus and separated and identified by high performance liquid chromatography (HPLC) with fluorescence detection. The following pterins were found and identified for the wild-type strain NRRL1555: carboxypterin (6.7 x 10(-6) M), neopterin (4.2 x 10(-7) M), xanthopterin (5.3 x 10(-6) M), biopterin (3.9 x 10(-7) M), pterin (9.1 x 10(-7) M), and 6,7-dimethylpterin (1.2 x 10(-6) M). The HPLC elution profiles of the wild type were compared to a set of phototropism mutants (genotype mad) with specific defects in the light-transduction pathway. The mutant profiles were qualitatively similar to those of the wild type. Quantitative differences were, however, discerned for madA, madC, and madH mutants. The madA mutation was associated with increased amounts of biopterin and 6,7-dimethylpterin and a reduction of neopterin, pterin, xanthopterin, and unidentified pterins eluting at 14-18 min. The stimulatory effect of the madA mutation on biopterin and 6,7-dimethylpterin appears to be compensated by a secondary mutation (pde) which is responsible for the loss of 75% of adenosine 3',5'-cyclic monophosphate (cAMP)-phosphodiesterase activity. In a madA pde double mutant the amounts of biopterin and 6,7-dimethylpterin fell below the wild-type level. These results suggest that an increased level of endogenous cAMP represses the biosynthesis of these pterins. The madC mutation increased the amounts of biopterin and xanthopterin and that of the unidentified pterins which could be derivatized to carboxypterin. Single madB mutations had, compared to the wild type, two times higher amounts of biopterin and two times lower amounts of neopterin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Action Spectra for UVB Impacts on Blepharisma japonicum Motility and Photobehavior

Abstract— The ciliate Blepharisma japonicum was exposed to artificial polychromatic and monochromatic UV radiation to evaluate the relative roles of UVB (280–315 nm UV radiation) and UVA (315–400 nm UV radiation) in altering its motility and photobehavior and to determine absolute weighting coefficients for these effects in the UVB range. Under polychromatic UV irradiation B. japonicum cells showed a severe reduction of cell speed and of the capability to respond to light stimuli. At low doses, however, UV caused a significant increase in the average velocity of a cell population. The UVB exclusion experiments indicated that UVA does not significantly alter motility and photoresponsiveness. The increase and the subsequent decrease in cell velocity was observed also under monochromatic irradiation at 281, 290 and 300 nm, whereas at 310 nm cells swim faster up to the highest photon flux density used. The cell capability of reacting to photic stimuli, conversely, steadily declined with increasing photon flux density at all the tested UVB wavelengths. The action spectra for the alteration of cell velocity and the impairment of photoresponsiveness show that the lower the irradiation wavelength, the more remarkable are the UVB effects and suggest different targets for the increase and the decrease in cell velocity.     

Separate Sensory Pathways for Photomorphogenesis in Phycomyces

The zygomycete Phycomyces blakesleeanus develops two types of sporangiophores of very different size: macrophores and microphores. Blue light inhibits the development of microphores and stimulates the development of macrophores. These responses are called photomicrophorogenesis and photomacrophorogenesis, respectively; phototropism designates the growth of the macrophores toward blue light and photocarotenogenesis, the increased accumulation of β-carotene under blue light. We have isolated three pim mutants that develop microphores under continuous illumination at fluence rates that inhibit them in the wild type. The thresholds for photomicrophorogenesis in the mutants were higher than in the wild type, but the thresholds for photomacrophorogenesis and phototropism did not change. At least one of the pim mutants had a much higher threshold for photocarotenogenesis than the wild type. A madJ mutant strain, already known for its very defective phototropism, was defective for photomicrophorogenesis, but normal for photomacrophorogenesis and photocarotenogenesis. The requirement for the pim and madJ gene functions separates the two photomorphogenetic responses. The results indicate that the four responses to blue light are based on a combinatorial use of sensory transducers.     

蒙脱石对卷烟烟雾中自由基清除作用的研究

利用ＥＳＲ法测定了卷烟烟雾焦油中自由基的含量。同时测定了蒙脱石制成的复合滤嘴的卷烟烟雾焦油中的自由基，其含量下降（３２±３）％。     

Action spectra for photogravitropism of Phycomyces wild type and three behavioral mutants (L150, L152, and L154)

We have measured fluence rate-response curves and action spectra for photogravitropism in Phycomyces wild type and in three recently isolated mutants with elevated phototropic thresholds. The action spectra were determined from least-squares fits of a sigmoidal function to the fluence rate-response data for each wavelength. The action spectrum for wild type has maxima near 383, 413, 452, and 490 nm and minima near 397, 425, and 469 nm. This photogravitropism action spectrum is very similar to the Phycomyces phototropic balance action spectrum between 413 but has significantly higher effectiveness below 400 nm and above 490 nm. These differences may be caused by dichroic effects of the oriented receptor pigment and/or by multiple receptor pigments. The action spectra of the three mutants differ significantly from one another and from that of wild type. Relative to the wild type spectrum, all three mutants exhibit a suppression in effectiveness near 425 nm, which is near the transmission peak of the broadband blue filter used to isolate the mutants.     

Investigating the Red Shift between in vitro and in vivo Urocanic Acid Photoisomerization Action Spectra

Abstract— Trans-urocanic acid (UCA) is found in the upper layer of the skin and UV irradiation induces its photoisomerization to cis -UCA. Cis -UCA mimics some of the immunosuppressive properties of UV exposure. The wavelength dependence for in vitro photoisomerization of trans-UCA (15 μM) over the spectral range 250 nm-340 nm (10 nm intervals) was determined. The action spectrum revealed that maximal cis-UCA production occurred at 280 nm, which is red-shifted by 10-12 nm from its absorption peak at 268 nm and differs markedly from the reported action spectra for cis-UCA production in mouse skin in vivo , which peaks at 300-310 nm. The reasons for the red shift between the in vitro and in vivo action spectra are not clear. There is limited evidence suggesting that the UV absorption maximum of trans- UCA red shifts from 268 nm in vitro to 310 nm on interaction with stratum corneum proteins in vivo. This phenomenon was investigated by applying trans-UCA (2.5 mg/cm²) in an oil emulsion to isolated human stratum corneum. After incubation at 37°C for 1 h, the absorption spectra of stratum corneum with UCA and with oil only were compared using a Xe arc source and a spectrora-diometer. A moderate red shift in trans-UCA absorption from ∼268 nm to 280 nm was observed. In summary, we suggest that the 10-12 nm red shift between the UCA absorption spectrum peak and the action spectrum peak in vitro may be accounted for by the wavelength dependence of quantum yields reported over the 254-313 nm range. The red shift between the in vitro and in vivo photoisomerization action spectra may result from the 10 to 12 nm red shift in the absorption of UCA in association with stratum corneum proteins, combined with increasing quantum yields over the 254-313 nm range.     

镁离子作用下乙醇溶液的红外光谱研究

采用红外光谱法对MgCl2乙醇溶液进行了研究.乙醇分子的谱带变化表明,Mg<'2+>与乙醇分子中C-O发生强烈作用,同时,随着MgCl2的加入,原有氢键结构遭到破坏,形成新的结构,计算得到其溶剂化数为3.87～1.83.针对溶液中各聚体氢键峰面积的变化进行了定量分析,确定了在0.3406～1.6083mol/kg浓度范围内二聚体含量与MgCl2浓度呈线性关系,其线性方程为△A=0.24202+16.65859 C;,相关系数R=0.9922,二聚体和多聚体呈可逆平衡关系,进一步揭示了溶液溶剂化的微观过程.     

In Situ Action Spectra Suggest that DNA Damage is Involved in Ultraviolet Radiation-induced Immunosuppression in Humans

Abstract— The mixed epidermal cell lymphocyte reaction (MECLR) is a commonly used method to study the immunomodulatory effects of UV radiation. The in vitro action spectrum for the MECLR showed that the UV-induced suppression of the MECLR responses is associated with UV-induced DNA damage. To investigate whether in vivo DNA damage also leads to the abrogation of the MECLR, in situ action spectra were made for the MECLR and the induction of thymine dimers (T<>T). Human skin, obtained from plastic surgery, was exposed to monochromatic light of 254, 297, 302 and 312 nm. After irradiation, epidermal cells were isolated and used as stimulator cells in the MECLR or processed for flow cytometric detection of T<>T. On the basis of dose-response curves for each wavelength, the action spectra for suppression of the MECLR and the induction of T<>T were calculated. These spectra showed close similarities, suggesting that, also in situ, UV-induced DNA damage is involved in the UV-induced suppression of the MECLR. Both action spectra showed a small decline from 254 nm to 302 nm, followed by a steep decline to 312 nm. These data show that, in situ, UVC can efficiently induce DNA damage and modulate cutaneous immune responses.     

Blue-Light Receptor Requirement for Gravitropism,Autochemotropism and Ethylene Response in Phycomyces*

Light, gravity and ethylene represent for plants and fungi important environmental cues for spatial orientation and growth regulation. Coordination of the frequently conflicting stimuli requires signal-integration sites, which, however, remain largely unidentified. The genetic and physiological basis for signal integration was investigated with a set of phototropism mutants (genotype mad) of the UV- and blue-light-sensitive fungus Phycomyces blakes-leeanus, which responds also to gravity, ethylene and nearby obstacles (autochemotropism or avoidance response). Both, class 1 and class 2 mutants display a reduced sensitivity to visible light. Class 1 mutants with defects in genes mad A, B, C, Z have preserved their sensitivity to gravity and ethylene, whereas class 2 mutants with defects in genes mad D, E, F, G, J have lost it. We found that the phototropic sensitivity of class 1 mutants is affected roughly to the same extent in far UV and blue light. In contrast, the sensitivity loss of class 2 mutants is restricted mainly to the near-UV and the blue-light region, whereas the sensitivity to far UV is only mildly affected. This behavior of the class 2 mutants indicates that different photoreceptors mediate phototropism in far-UV and in near-UVhlue light. The photogravitropic action spectra for two class 2 mutants with defects in genes mad F and mad J display distortions between 342 and 530 nm and a bathochromic shift relative to the action spectrum of the wild type. These features indicate that the mad F and mad J mutants are affected at the level of the blue-light photoreceptor system. As an implication we infer that an intact near-UVhlue-light photoreceptor system is required even in darkness for negative gravitropism, the ethylene response and autochemotropism. In Phycomyces, signal integration occurs, at least in part, at the level of the near-U Vhlue-light photoreceptor system.     

Photoinhibition of Cyanobacteria and its Application in Cultural Heritage Conservation

Light has bilateral effects on phototrophic organisms. As cyanobacteria in Roman hypogea are long acclimatized to dim environment, moderate intensity of illumination can be used to alleviate biodeterioration problems on the stone substrata. Moderate intensity of light inactivates cyanobacteria by causing photoinhibition, photobleaching and photodamage to the cells. The effectiveness of light depends not only on its intensity but also on the composition and pigmentation of the component cyanobacteria in the biofilms. Red light is the most effective for the species rich in phycocyanin and allophycocyanin, such as Leptolyngbya sp. and Scytonema julianum, whereas green light is effective to inhibit the species rich in phycoerythrin, like Oculatella subterranea. White light is effective to control the grayish and the black cyanobacteria, such as Symphyonemopsis sp. and Eucapsis sp. abundant in all of these pigments. Blue light is the least effective. 150 μmol photons m^?2 s^?1 of blue light cannot cause biofilm damage while the same intensity of red, green or white irradiation for 14 days can severely damage the cyanobacterial cells in the biofilms due to ROS formation. Electron spin resonance spectroscopy detected the formation of radicals in different cyanobacterial cellular extracts exposed to 80 μmol photons m^?2 s^?1 of light.     

Subliminal light control of dark adaptation kinetics in Phycomyces phototropism

The dark adaptation kinetics of Phycomyces phototropism depend critically on the experimental protocol. When sporangiophores that had been light-adapted to a fluence rate of 1 W m-2 at 447 nm were exposed to dim unilateral light, the adaptation kinetics showed exponential decay (6 min time constant). However, when light-adapted sporangiophores were kept for variable intervals in darkness (i.e. in presence of traditional red safelight) and then exposed to dim unilateral test light, the decay kinetics of adaptation were biexponential with a rapid decay during the first minute (1 min time constant), followed by a slow recovery (11 min time constant). Thus, the dim subliminal light given after the sporangiophores had been adapted to 1 W m-2, was actually perceived, and exerted control over the dark-adaptation process. The observed acceleration of dark-adaptation kinetics constitutes a novel light effect of the sporangiophore. At wavelength 383 nm this effect was not observed. Because a beta-carotene lacking mutant, L91 (genotype carB), was unmodified in dark-adaptation kinetics measured in the presence or absence of subliminal light, it appears that beta-carotene is not involved in the photocontrol of adaptation.     

Effects of Pressure and Pulsed Mechanical Action on the IR and ESR Spectra of Ultrafine Polytetrafluoroethylene

The sensitivity of thermogasdynamically dispersed polytetrafluoroethylene to mechanical action was studied by IR and ESR spectroscopy. It is shown that exposure of sample to a pressure of 10 000 kg/cm² and mechanical impact does not lead to transition from a helical to a planar zigzag conformation but increases the amorphous properties and the number of defects of the sample structure. It is assumed that the defects are due to the appearance of terminal =CF₃ groups and =CF₃ groups in the side chain or deformation of chain regions with conjugated bonds.     

The Photochemical Isomerization Kinetics of Urocanic Acid and Their Effects upon the in vitro and in vivo Photoisomerization Action Spectra

Abstract— The kinetic rate equation for the photoreversible photoisomerization between trans -urocanic acid (UA) and cis-UA following absorption of UV radiation has been solved and used to show that the maximum of the trans -UA photoisomerization action spectrum depends upon both the initial trans -UA concentration irradiated in an experiment and upon the irradiation dose used to determine the amount of cis -UA generated. This kinetic model can be used to explain current discrepancies between in vitro and in vivo photoisomerization action spectra reported in the literature.     

DFT Simulation of Electron Spectra for Auger Electron and Photoelectron Spectra of Lithium Compounds

(Li, O, F)-Auger electron, and X-ray photoelectron spectra (AES, VXPS) of solid lithium compounds (Li metal, LiCl, LiF, Li₂O) are simulated by deMon density functional theory (DFT) calculations using the model molecules of the unit cell. Calculated valence XPS, core-electron binding energies (CEBE)s, and Li-, O-, and F-KVV AES for the substances correspond considerably well to experimental results. For the calculation of VXPS, the observed spectra of Li₂O pellet with chemisorbed CO₂ almost show agreement with simulation curve of the valence XPS according to the model for the 1/1 ratio of Li₂O/Li₂CO₃. In the case of AES calculation, we analyze the experimental AES with our modified Auger electron kinetic energy calculation method which corresponds to the two final-state holes at the ground state and at the transition-state in DFT calculation by removing 1 and 2 electrons, respectively. Experimental KVV AES of the Li atom, and (O, F) KVV AES of (Li₂O and LiF) in the substances almost agree well to the AES calculated with maximum kinetic energies at the ground state, and at the transition-state, respectively.     

Techniques for Infrared Spectra of Corrosive Solids

Abstract

Two new pressing techniques are described for obtaining excellent infrared spectra of highly corrosive and moisture sensitive solids. The elimination of the Christiansen effect in the spectrum of the salt N₂F₃ ⁺AsF₆ ^? is demonstrated.