MODIFIED ACTION SPECTRA OF PHOTOGEOTROPIC EQUILIBRIUM IN Phycomyces blakesleeanus MUTANTS WITH DEFECTS IN GENES madA, madB, madC, and madH

Abstract— Action spectra of photogeotropic equilibrium were measured for behavioral mutants of Phycomyces blakesleeanus with defects in the genes madB, madC and madH as well as for a double mutant defective in the genes madA and madC. The action spectra of strains C109 (madB), LI (madC) and L52 (madA madC) all lack the broad near-ultraviolet peak which extends from 347 to 386 nm in the wild type; the peaks at 414 and 491 nm are also missing in these mutants. The double mutant L52 (madA madC) shows a novel broad peak at 477 nm; the relative quantum effectiveness of L52 at 477 nm is 10 times higher than in LI (madC119). These properties of the double mutant L52 (madA madC) suggest steric interaction of the madA and the madC gene products in the photoreceptor complex. For the hypertropic mutant L84 (madH) the action spectrum and absolute sensitivity are similar to those for wild type. These results confirm and extend previous findings that multiple photoreceptors are mediating phototropism in P. blakesleeanus.     

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.     

Biphasic fluence-response curves and derived action spectra for light-induced absorbance changes in Phycomyces mycelium

The photoresponses of Phycomyces, including phototropism and photocontrol of sporangiophore development, are mediated primarily by blue and UV light. Recent results on these two responses indicated a subsidiary role for green light. We have measured in vivo light-induced absorbance changes (LIAC) in mycelial samples of a caroteneless (carB) strain to compare the effectiveness of UV, blue, and green light. In the dual-wavelength kinetic mode of the spectrophotometer, measuring wavelengths of 445 and 470 nm were chosen, because green light produces substantial absorbance changes between these two wavelengths. Fluence-response curves were measured for 13 wavelengths between 365 and 530 nm, and for variable exposure times between 0.5 and 320 s. With one exception (365 nm), the curves were biphasic. The low fluence component was generally sigmoidal with an abrupt rise. The high fluence component failed to reach saturation for the fluences tested (less than 70 μmol m⁻² s⁻¹). Using the inferred threshold fluences of these two components as criterion effects, we obtained two action spectra. For the low fluence component, the action spectrum showed major peaks at 394, 450, and 530 nm and a minor peak at 416 nm. The high fluence component action spectrum showed very little sensitivity in the blue region. The major sensitivity was in the near UV, and a relatively small peak appeared in the green part of the spectrum at 507 nm. The biphasic character of the fluence-response curves suggests that two photosystems are responsible for the absorbance changes. The low fluence photosystem is sensitive mainly to blue and UV light and may thus represent a physiological blue-light photoreceptor. The high fluence photosystem is clearly not of this type. It (and perhaps the low fluence system as well) may mediate some of the subsidiary physiological effects of green light.     

Oxygen-independent inactivation of Haemophilus influenzae transforming DNA by monochromatic radiation: action spectrum, effect of histitine and repair.

Abstract— The action spectrum for the oxygen-independent inactivation of native transforming DNA from Haemophilus influenzae with near-UV radiation revealed a shoulder beginning at 334 and extending to 460 nm. The presence of 0.2 M histidine during irradiation produced a small increase in inactivation at 254, 290 and 313 nm, a large increase at 334 nm and a decrease in inactivation at 365, 405 and 460 nm. Photoreactivation did not reverse the DNA damage produced at pH 7.0 at 334, 365, 405 and 460 nm, but did reactivate the DNA after irradiation at 254, 290 and 313 nm. The inactivation of DNA irradiated at 254, 290 and 313 nm was considerably greater when the transforming ability was assayed in an excision-defective mutant compared with the wild type, although DNA irradiated at 334, 365, 405 and 460 nm showed smaller differences. These results suggest that the oxygen-independent inactivation of H. influenzae DNA at pH 7 by irradiation at 334, 365, 405 and 460 nm is caused by lesions other than pyrimidine dimers.     

INDUCTION OF SLOWLY DEVELOPING ALKALI-LABILE SITES IN HUMAN P3 CELL DNA BY UVA AND BLUE- AND GREEN-LIGHT PHOTONS: ACTION SPECTRUM

Action spectra (365–520nm) for the formation of DNA single-strand breaks (SSB) and slowly developing alkali-labile sites (SDALS) in human teratocarcinoma P3 cells in culture were determined. Induction of SDALS results from the absorption of blue- and green-light photons. The spectrum has a broad peak that is maximal between 400 nm to 500 nm and declines sharply above and below these wavelength regions. Negligible yields of SDALS were produced by photons at wavelengths of 365 nm or shorter and at 520 nm or longer, whereas for SSB, the action increases with shorter wavelength throughout the whole spectral range studied. The configuration of the SDALS action spectrum suggests that the primary chromophore, and therefore possibly the photosensitizer, is a mixture of porphyrin and flavin residues.     

Thermoluminescence of irradiated poly(methyl methacrylate)

Thermoluminescence of poly(methyl methacrylate) (PMMA) irradiated with x rays, has been studied in the temperature range 100 to 460°K. Two glow peaks with maxima at 136 and 368°K have been observed. These are analyzed by three methods and the results are compared. Both curves obey second order kinetics and correspond to activation energies of 0.17 and 0.88 eV, respectively. It is possible to identify the centers responsible for the two peaks by correlation with electron spin resonance and optical data obtained for the same samples irradiated under the same conditions. Spectral studies of the emission show that the low temperature peak has its maximum at 365 nm while the high temperature peak has its maximum at 480 nm.     

Photoreactivation of killing in Streptomyces: action spectra and kinetic studies

Abstract— An action spectrum was obtained for photoreactivation of killing (PR) of Streptomyces griseus conidia. This spectrum shows a major peak around 436 nm, originally observed by A. Kelner, and a secondary peak at 313 nm not previously reported. The rate of PR shows a strong dependence upon temperature and dose rate of the PR light at 436 nm, but this decreases to only a slight dependence upon these parameters at 313 nm. These findings suggested that PR at 436 nm in this organism is of the usual photoenzymatic type, but that PR at 313 nm might be of a different kind. A mutant (PHR-1) of S. griseus was found that shows only a narrow range of PR (roughly 310–400 nm) with a single peak at 313 nm. The PR efficiency was lower than for wild type and the PR sector not greater than one-half that of wild type. This PR shows no temperature dependence. Essentially similar behavior was observed with wild-type Streptomyces coelicolor. These findings show that at least some of the PR at 313 nm is a separable phenomenon. It is therefore unlikely to involve a mechanism identical to that at 436 nm. The nature of PR at 313 nm in Streptomyces is not known. If it is enzymatic, it is remarkable in having little or no dependence upon temperature and dose rate. Absence of photoprotection and liquid-holding recovery indicate that it is not indirect PR. Some of it (that part exhibited by S. griseus PHR-1 and S. coelicolor) might result from a direct photochemical action on DNA.     

ON THE EMERSON ENHANCEMENT EFFECT IN THE FERRICYANIDE HILL REACTION IN CHLOROPLAST FRAGMENTS*

Abstract— The Emerson effect is demonstrated in the ferricyanide Hill reaction when the rates of steady-state oxygen evolution are measured in spinach chlorplast fragments exposed to red (650 nm) and far-red (700 nm) light of high but not saturating intensity. However, at very low light intensity, the Emerson effect could not be observed. These experiments suggest that ferricyanide can be reduced at two sites. At low light intensity, the rate at one site predominates and at this site one photochemical system is active. At high light intensity, however, the action at a site that is dependent on the cooperation of two photochemical systems predominates. The action spectra of the ferricyanide Hill reaction measured in the presence of an excess of 650 nm or in the excess of 700 nm light show two peaks: one at 650 nm due to chlorophyll b and the other around 675 nm due to chlorophyll a. The ratio of chlorophyll a to chlorophyll b peaks is about 1.4 when 650 nm background light is used; the same ratio is about 0.7 with 700 nm background light. The two pigment systems seem to contain both chlorophyll a and chlorophyll b but in different proportions.     

The synthesis and luminescent properties of bonded Eu(III) polymer phosphors for white light-emitting diode

A coordination and copolymerization strategy was adopted to synthesize bonded Eu(III) polymer phosphor poly(MMA-co-Eu(BTZ)₂(Phen)(UA)) (PM-Eu for short) with methyl methacrylate (MMA) as polymer matrix and Eu-complex monomer Eu (BTZ)₂(Phen)(UA) using azodiisobutyronitrile as initiator. The copolymer PM-Eu exhibits thermal stability up to 266°C. It also exhibits wide and strong excitation bands from 230 to 380 nm monitored at 612 nm, matching well with the 365 nm of ultraviolet (UV) chip. PM-Eu displays Eu(III) characteristic peaks at 579, 591, 612, 650, and 700 nm under the excitation of 365 nm of UV light. Meanwhile, it has a fluorescence lifetime of 0.582 ms, and it has a higher quantum yield of 0.672. All the results prove that the polymer PM-Eu can be applied as a red component for fabrication of near UV-based white light-emitting diode (LED).     

ACTION SPECTRUM FOR PHOTOREACTIVATION OF ULTRAVIOLET-INDUCED MORPHOLOGICAL ABNORMALITY IN SEA URCHIN EGGS

Abstract An action spectrum was obtained for photoreactivation (PR) of morphological abnormality arising from ultraviolet (UV)-irradiation of sea urchin sperm. The wavelength dependence of PR was measured by the restoration of the formation of normal pluteus larvae after the exposure of fertilized eggs to various fluences of monochromatic PR light (313 to 500 nm). The PR action spectrum showed a maximum around 365 nm and a secondary peak somewhere above 400 nm. High PR activity beyond 400 nm wavelengths may reflect an advantageous or adaptational ability to cope with harmful effects of solar UV radiation.     

NONRECIPROCAL SYNERGISTIC LETHAL INTERACTION BETWEEN 365-nm and 405-nm RADIATION IN WILD TYPE and uvrA STRAINS OF ESCHERICHIA COLI*

Abstract— Lethality by 405-nm radiation in three repair-proficient and two uvrA strains of Escherichia coli that belong to two isogenic series was greatly enhanced by prior exposures to 365-nm radiation at fluences greater than 1 times 10₆Jm_-2. Fluences at 365 nm that yielded a surviving fraction of 0.10 (>1 times 10₆ Jm_-2) in the 5 strains tested resulted in the following 405-nm fluence enhancement factors (FEF, ratio of the 405-nm F₃₇ in the absence of a prior 365-nm irradiation to that in the presence): strain K.12 AB1157 (wild type), 8.7; strain B/r (wild type), 52; strain WP2 (wild type), 25; strain WP2s (uvrA), 13; strain K.12 AB1886 (uvrA), 15. The maximal 405-nm FEF value obtained after a prior 365-nm irradiation at greater fluences was 83 in the wild-type strain B/r. Enhancement of anoxic 405-nm radiation after a prior aerobic 365-nm exposure was not detectable, suggesting that prior aerobic irradiation at 365-nm increased the effects of damage produced at 405 nm by means of an oxygen-dependent process. Single-strand breaks (or alkali-labile bonds) were produced by 405-nm radiation at 3.0 times 10_-5 breaks per 2.5 times 10₉ daltons per Jm_-2 in the polA strain P3478; pyrimidine dimers were not detected by biological assay (photoreactivation) at 405 nm. Although the introduction of different DNA lesions produced by 365- and 405-nm radiations cannot be ruled out, we propose that the strong synergistic effect of 365-nm irradiation on 405-nm lethality is the consequence of pronounced inhibition by 365-nm radiation of components of the DNA-repair systems that can mend or bypass damage produced by 405-nm radiation.     

AN ACTION SPECTRUM OF PHOTOREACTIVATING ENZYME FROM SEA URCHIN EGGS

An action spectrum for photoreactivating enzyme activity from unfertilized eggs of the sea urchin Hemicentrotus pulcherrimus was determined. The range of the spectrum is 313 to 500 nm, with a maximum at 365 nm. Comparison of this spectrum with that for photorecovery of developmental damage in the sea urchin embryo indicates the general similarity of the two processes.     

ACTION SPECTRA FOR PHOTOTROPIC BALANCE IN Phycomyces blakesleeanus: DEPENDENCE ON REFERENCE WAVELENGTH and INTENSITY RANGE

Abstract— Action spectra for phototropic balance of Phycomyces blakesleeanus sporangiophores were measured for various reference wavelengths and intensity ranges. Balance action spectra were made at fluence rates of 10^-4 W m^-2 with reference wavelengths of 450 nm, 394 nm, 507 nm, and broadband blue light. For broad-blue light and 450 nm light as references, typical flavin-like action spectra were found with a ma jor peak at 455 nm, a secondary peak at 477 nm, and a minor peak at 383 nm; these peaks are wider for broad blue than for 450 nm light. With the 394 nm reference, there is a major peak at 455 nm, a secondary peak at 477 nm and a minor peak at 394 nm. An action spectrum with 507 nm reference has a major peak at 455 nm and a minor peak at 383 nm, but no peak at 477 nm. A balance action spectrum was made with 450 nm reference light near threshold intensity (2 times 10^-8 W m^-2); there, the 386 nm peak is greatly reduced, while the 455 nm peak is enhanced. The intensity dependence of the 386 nm peak was studied in detail for reference light of 450 nm. We found that the relative quantum efficiency of the 386 nm light increases with the logarithm of the 450 nm fluence rate; in the high intensity range (0.3 W m^-2) the relative quantum efficiency of the 386 nm light is 1.3 and approaches zero at 10^-9 W m^-2. These findings indicate that P. blakesleeanus phototropism is mediated by multiple interacting pigments or by a photochromic photoreceptor.     

ACTION SPECTRA FOR INHIBITION OF HYPOCOTYL GROWTH OF WILD-TYPE PLANTS AND OF THE hy2 LONG-HYPOCOTYL MUTANT OF Arabidopsis thaliana L.

Abstract— An analysis was made by action spectroscopy, using the Okazaki Large Spectrograph, of the inhibition of hypocotyl elongation of wild-type plants and the hy2 mutant of Arabidopsis thaliana. Two day old etiolated seedlings were irradiated for 8 h with monochromatic light and left in the dark for 16 h before measurement of hypocotyl length. Spectrophotometric measurement showed that levels of phytochrome in the etiolated tissue of the hy2 mutant were less than 9% of those in the wild type. The action spectra of the wild type looked like those of high irradiance response and showed peaks at 375, 450, 625 and 725 nm, whereas the action spectra of hy2 showed only the peaks at 375 and 450 nm. Monochromatic light of wavelengths longer than 500 nm had no significant inhibitory effects on hy2 plants. Blue and UV-A light were about five times more effective in the wild type than in hy2 plants. Severe inhibitory effects were observed with UV-B light. It is concluded that inhibition of the growth of the hypocotyl involves combined actions of phytochrome and a putative blue/UV-A photoreceptor(s).     

LETHAL ACTION OF ULTRAVIOLET AND VISIBLE (BLUE-VIOLET) RADIATIONS AT DEFINED WAVELENGTHS ON HUMAN LYMPHOBLASTOID CELLS: ACTION SPECTRA AND INTERACTION SITES

Abstract— The repair proficient human lymphoblastoid line (TK6) has been employed to construcr an action spectrum for the lethal action of ultraviolet (UV) radiation in the range254–434 nm and to examine possible interactions between longer (334, 365 and 405 nm) and shorter wavelength (254 and 313 nm) radiations. The action spectrum follows a DNA absorption spectrum fairly closely out to 360 nm. As in previously determined lethal action spectra for procaryotic and eucaryotic cell populations, there is a broad shoulder in the334–405 nm region which could reflect the existence of either (a) a non-DNA chromophore or (b) a unique photochemical reaction in the DNA over this region. Pre-treatment with radiation at 334 or 365 nm causes either a slight sensitivity to (low fluences) or protection from (higher fluences) subsequent exposure to radiation at a shorter wavelength (254 or 313 nm). Pre-irradiation at a visible wavelength (405 nm) at all fluence levels employed sensitizes the populations to treatment with 254 or 313 nm radiations. These interactions will influence the lethal outcome of cellular exposure to broad-band radiation sources.     

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.     

Action spectrum for the suppression of arylalkylamine N-acetyltransferase activity in the two-spotted spider mite Tetranychus urticae

An action spectrum was obtained for the suppression of arylalkylamine N -acetyltransferase (NAT) activity in the two-spotted spider mite Tetranychus urticae by irradiating the mite with monochromatic lights of various wavelengths using the Okazaki Large Spectrograph at the National Institute for Basic Biology, Okazaki, Japan. Fluence–response curves were obtained for wavelengths between 300 and 650 nm by irradiating the mite for 4 h day⁻¹. The samples were frozen after the third exposure. A negative correlation between the logarithmic fluence rate and NAT activity was detected in the range of 0.01–1 μmol m⁻² s⁻¹ for wavelengths between 300 and 500 nm and in the range of 0.1–10 μmol m⁻² s⁻¹ for wavelengths between 550 and 650 nm. The constructed action spectrum indicated that the photoreceptors mediating the circadian and/or photoperiodic systems might be UV-A- and blue-type photoreceptors with absorption peaks at 350 and 450 nm.     

Equal-quantum action spectra indicate fluence-rate-selective action of multiple photoreceptors for photomovement of the thermophilic cyanobacterium Synechococcus elongatus

Unicellular thermophilic cyanobacterium Synechococcus elongatus displayed phototaxis on agar plate at 55 degrees C. Equal-quantum action spectra for phototactic migration were determined at various fluence rates using the Okazaki Large Spectrograph as the light source. The shapes of the action spectra drastically changed depending on the fluence rate of the unilateral monochromatic irradiation: at a low fluence rate (3 mumol/m2/s), only lights in the red region had significant effect; at a medium fluence rate (10 mumol/m2/s), four major action peaks were observed at 530 nm (green), 570 nm (yellow), 640 nm (red) and 680 nm (red). At high fluence rates (30-90 mumol/m2/s), the former two peaks remained, while red peaks at 640 nm and 680 nm disappeared and, interestingly, an action peak around 700-740 nm (far-red) newly appeared. These results indicate that two or more distinct photoreceptors are involved in the phototaxis and that suitable photoreceptors are selectively active in response to the stimulus of light fluence rates. Far-red or red background lights irradiated vertically from above drastically inhibited phototaxis toward red light or far-red light, respectively. These results indicate involvement of some phytochrome(s).     

SENSITIVITY OF STRAINS OF ESCHERICHIA COLI DIFFERING IN REPAIR CAPABILITY TO FAR UV,NEAR UV AND VISIBLE RADIATIONS*

Abstract— In stationary phase, strains of Escherichia coli deficient in excision (B/r Her) or recombination repair (K.12 AB2463) were more sensitive than a repair proficient strain (B/r) to monochromatic near-ultraviolet (365 nm) and visible (460 nm) radiations. The relative increase in sensitivity of mutants deficient in excision or recombination repair, in comparision to the wildtype, was less at 365 nm than at 254 nm. However, a strain deficient in both excision and recombination repair (K12 AB2480) showed a large, almost equal, increase in sensitivity over mutants deficient in either excision or recombination repair at 365 nm and 254 nm. All strains tested were highly resistant to 650 nm radiation. Action spectra for lethality of strains B/r and B/r Her in stationary phase reveal small peaks or shoulders in the 330–340, 400–410 and 490–510 nm wavelength ranges. The presence of 5μg/ml acriflavine (an inhibitor of repair) in the plating medium greatly increased the sensitivity of strain B/r to radiation at 254, 365 and 460 nm, while strains E. coli B/r Her and K12 AB2463 were sensitized by small amounts. At each of the wavelengths tested, acriflavine in the plating medium had at most a small effect on E. coli K.12 AB2480. Acriflavine failed to sensitize any strain tested at 650 nm. Evidence supports the interpretation that lesions induced in DNA by 365 nm and 460 nm radiations play the major role in the inactivation of E. coli by these wavelengths. Single-strand breaks (or alkali-labile bonds), but not pyrimidine dimers are candidates for the lethal DNA lesions in uvrA and repair proficient strains. At high fluences lethality may be enhanced by damage to the excision and recombination repair systems.     

ACTION SPECTRA FOR ACCUMULATION OF INORGANIC CARBON IN THE CYANOBACTERIUM, Anabaena variabilis

Abstract— Action spectra for accumulation of inorganic carbon were obtained for Anabaena variabilis , strainM–2, in the presence and absence of photosynthetic CO₂ fixation. The action spectrum for inorganic carbon accumulation in the presence of CO₂ fixation showed a peak around 684 nm, corresponding to chlorophyll a absorption in PS 1, while that for CO₂ fixation showed a peak around 630 nm, corresponding to phycocyanin absorption in PS 2. The action spectra obtained in the presence of iodoacetamide or diuron, which inhibit CO₂ fixation, showed two peaks, one at about 684 nm and the other at 630 nm, with the 630 nm peak height 80 to 90% of the 684 nm peak. These results indicate that inorganic carbon transport in A. variabilis can be driven with near equal efficiency by energy derived from absorption in photosystem 1 alone and with energy transferred to PS 1 after absorption by PS 2.