| 1. |
- Ekelund, N. G. A.
(author)
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Interactions between photosynthesis and 'light-enhanced dark respiration' (LEDR) in the flagellate Euglena gracilis after irradiation with ultraviolet radiation
- 2000
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In: Journal of Photochemistry and Photobiology. B. - 1011-1344 .- 1873-2682. ; 55:1, s. 63-69
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Journal article (peer-reviewed)abstract
- The effects of ultraviolet radiation (UV-A, 315-400 nm plus UV-B, 280-315 nm) on photosynthesis and 'light-enhanced dark respiration' (LEDR) in Euglena gracilis have been investigated by using light pulses (80 s) with increasing photon fluence rates of 59, 163, 600, 1180, 2080 and 3340 mu mol m(-2) s(-1) and dark periods between the light pulses. LEDR is estimated as the maximum rate of oxygen consumption after a period of Light minus the rate of oxygen consumption 30 s after the maximum rate. Without any exposure to UV radiation, the photosynthetic rate and LEDR increase with increasing photon fluence rate. After 20 and 40 min exposures to UV radiation, the photosynthetic rate and LEDR as functions of photon fluence rate are reduced. After a 20 min UV treatment respiration is greater than photosynthesis after the first light pulse of 59 mu mol m(-2) s(-1) radiation, and especially at higher photon fluence rates photosynthesis is lower than the control values. The inhibitory effects of UV radiation on photosynthetic rate and LEDR are greater after a 40 min UV exposure than after a 20 min exposure. Only at 600 mu mol m(-2) s(-1) is the rate of oxygen evolution greater than that of oxygen consumption after a 40 min UV treatment. Both photosynthetic rate and LEDR are inhibited by the photosynthetic inhibitor DCMU (10(-5) M) in a similar way, which indicates close regulatory interactions between photosynthesis and LEDR. Potassium cyanide (KCN) inhibits dark respiration more than it inhibits LEDR. Dark respiration is not affected to the same degree by UV radiation as are photosynthesis and LEDR.
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| 2. |
- Nielsen, Tom, 1956-, et al.
(author)
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Impact of natural and artificial ultraviolet-B radiation on motility and growth rate of marine dinoflagellates
- 1995
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In: Journal of Photochemistry and Photobiology. B. - 1011-1344 .- 1873-2682. ; 27, s. 73-79
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Journal article (peer-reviewed)abstract
- The growth rates and motility of dinoflagellates were studied in the field in the presence or absence of UVB radiation, as well as in the laboratory under artificial radiation conditions. Photosynthetically active radiation (PAR, 400–700 nm) and UVB radiation showed large variations due to cloud cover and seasonal changes in natural daylight. In Swedish coastal water, UVB radiation was attenuated to about 10% of surface irradiance at a depth of 120 cm. There was no significant difference in the motility of two strains of Prorocentrum minimum (Atlantic, LAC4LI; Kattegat, LAC6KA83) kept in the water at different depths (35 and 120 cm) for 4 h, with or without natural solar UV radiation, except for a day with high UVB irradiance (1.2 W m−2), which decreased the motility at a depth of 35 cm for the two species). Simulated in situ experiments with 2 h natural daylight, with and without natural UV radiation (UVB, 1.6 W m−2), had a dramatic effect on the motility of Gyrodinium aureolum. Artificial UVB radiation from UV lamps (4 h, 2.72 kJ m−2 day−1, biologically effective UVB radiation, UVBBE) in the laboratory decreased the motility of Heterocapsa triquetra (LAC20) by 56% and the two strains of P. minimum (Atlantic, LAC4LI; Kattegat, LAC6KA83) by 43% and 36% respectively; the growth was inhibited for all species, as well as for Amphidinium carterae (LAC1KA83), when organisms were exposed to more than 0.7 kJ m−2 day−1 of UVBBE radiation.
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| 3. |
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| 4. |
- Carr, Herman, et al.
(author)
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Parallel changes in non-photochemical quenching properties, photosynthesis and D1 levels at sudden, prolonged irradiance exposures in Ulva fasciata Delile
- 2007
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In: Journal of Photochemistry and Photobiology. B. - : Elsevier. - 1011-1344 .- 1873-2682. ; 87, s. 18-26
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Journal article (peer-reviewed)abstract
- The photosynthetic response to a sudden and prolonged high irradiance exposure and following recovery at low irradiance were studiedwith the aim of investigating the ability to withstand and adapt to high irradiance without prior high light adaptation. When thalli ofUlva fasciata, accustomed to a low irradiance (80 lmol photons m2 s1), were exposed to a high irradiance (1500 lmol photonsm2 s1), the D1 protein was rapidly degraded, reaching a steady-state level after 110 min. This was followed by a fast recovery whenthalli were transferred to dim light. The overall ability of non-photochemical quenching of chlorophyll fluorescence decreased and levelledoff at a sudden and prolonged exposure to high irradiance and followed the same trend as the D1 level with a fast recovery in dimlight. Ulva had intrinsic means to acclimate rapidly to high irradiance, when non-photochemical quenching did not operate properly, bymaintaining a smaller fraction of high light tolerant PSII assemblages and by maintaining a high non-photochemical quenching capacityof chlorophyll fluorescence in relation to the variable fluorescence. The overall absorption of light (400–700 nm) remained high duringthe period of high irradiance exposure. When Ulva were deprived of nutrients in the form of PES media the ability of non-photochemicalquenching decreased at photoinhibitory conditions. The possible causes for the responses at prolonged irradiance and the mechanismsfor the decrease of non-photochemical quenching are discussed, with implications for field measurements. 2006 Elsevier B.V. All rights reserved.
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| 5. |
- Cheregi, Otilia, et al.
(author)
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Inactivation of the Deg protease family in the cyanobacterium Synechocystis sp. PCC 6803 has impact on the outer cell layers
- 2015
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In: Journal of Photochemistry and Photobiology. B. - : Elsevier. - 1011-1344 .- 1873-2682. ; , s. 383-394
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Journal article (peer-reviewed)abstract
- The serine type Deg/HtrA proteases are distributed in a wide range of organisms from Escherichia coli to humans. The cyanobacterium Synechocystis sp. PCC 6803 possesses three Deg protease orthologues: HtrA, HhoA and HhoB. Previously we compared Synechocystis 6803 wild type cells exposed to mild or severe stress conditions with a mutant lacking all three Deg proteases and demonstrated that stress had strong impact on the proteomes and metabolomes [1]. To identify the biochemical processes, which this protease family is involved in, here we compared Synechocystis sp. PCC 6803 wild type cells with a mutant lacking all three Deg proteases grown under normal growth conditions (30 °C and 40 μmol photons m−2 s−1). Deletion of the Deg proteases lead to the down-regulation of proteins related to the biosynthesis of outer cell layers (e.g. the GDP mannose 4,6-dehydratase) and affected protein secretion. During the late growth phase of the culture Deg proteases were found to be secreted to the extracellular medium of the Synechocystis sp. PCC 6803 wild type strain. While cyanobacterial Deg proteases seem to act mainly in the periplasmic space, deletion of the three proteases influences the proteome and metabolome of the whole cell. Impairments in the outer cell layers of the triple mutant might explain the higher sensitivity toward light and oxidative stress, which was observed earlier by Barker and coworkers [2].
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| 6. |
- Fernandes, Sara R.G., et al.
(author)
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Photoactive immunoconjugates for targeted photodynamic therapy of cancer
- 2023
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In: Journal of Photochemistry and Photobiology. B. - : Elsevier. - 1011-1344 .- 1873-2682. ; 243
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Journal article (peer-reviewed)abstract
- Photodynamic therapy (PDT) has been used as an alternative or as a complement of conventional approaches for cancer treatment. In PDT, the reactive oxygen species (ROS) produced from the interaction between the photosensitizer (PS), visible light and molecular oxygen, kill malignant cells by triggering a cascade of cytotoxic reactions. In this process, the PS plays an extremely important role in the effectiveness of the therapy. In the present work, a new photoimmunoconjugate (PIC), based on cetuximab and the known third generation PS-glycophthalocyanine ZnPcGal4, was synthesized via reductive amination. The rationale behind this was the simultaneous cancer-associated specific targeting of PIC and photosensitization of targeted receptor positive cells. Varied reaction parameters and photodynamic conditions, such as PS concentrations and both type and intensities of light, were optimized. ZnPcGal4 showed significant photoactivity against EGFR expressing A431, EGFR-transfected HCT116 and HT29 cells when irradiated with white light of stronger intensity (38 mW/cm2). Similarly, the synthesized PICs-T1 and T2 also demonstrated photoactivity with high intensity white light. The best optimized PIC: sample 28 showed no precipitation and aggregation when inspected visually and analyzed through SE-HPLC. Fluorescence excitation of sample 28 and 125I-sample 28 radioconjugate (125I-PIC, 125I-radiolabeling yield ≥95%, determined with ITLC) at 660 nm showed presence of appended ZnPcGal4. In addition, simultaneous fluorescence and radioactivity detection of the 125I-PIC in serum and PBS (pH 7.4) for the longest incubated time point of 72 h, respectively, and superimposed signals thereof demonstrated ≥99% of loading and/or labeling yield, assuring overall stability of the PIC and corresponding PIC-radioconjugate w.r.t. both the appended ZnPcGal4 and bound-125I. Moreover, real-time binding analyses on EGFR-transfected HCT116 cells showed specific binding of 125I-PIC, suggesting no alternation in the binding kinetics of the mAb after appending it with ZnPcGal4. These results suggest dual potential applications of synthesized PICs both for PDT and radio-immunotherapy of cancer.
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| 7. |
- Figueroa, Felix, et al.
(author)
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Photobiological characteristics and photosynthetic UV responses in two Ulva species (Chlorophyta) from southern Spain.
- 2003
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In: Journal of Photochemistry and Photobiology. B. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 72:1-3, s. 35-44
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Journal article (peer-reviewed)abstract
- The effect of different wavebands of artificial UV (UVB and UVA) and photosynthetically active radiation (PAR) was assessed in two species of the genus Ova, U. olivascens and U rotundata, from southern Spain in order to test for possible differences in acclimation of photosynthesis. Both species share similar morphology but are subject to different light environments: U. rotundata is an estuarine alga, inhabiting subtidal locations, while U. olivascens is an intertidal, sun-adapted organism. Algae were exposed to three different UV conditions, PAR + UVA + UVB, PAR + UVA and PAR for 7 d. Short-term exposure (6 h) was also carried out, using two PAR levels, 150 and 700 mumol m(-2) s(-1). Pigment contents and photosynthesis vs. irradiance curves from oxygen evolution were used to contrast sun- and shade adaptation between these species. O-2-based net photosynthesis (P-max) and PAM-chlorophyll fluorescence (optimal quantum yield, F-v/F-m) were used as parameters to evaluate photoinhibition of photosynthesis in the experiments. The results underline different photobiological characteristics among species: the subtidal U rotundata had higher contents of pigments (Chl a, Chl b and carotenoids) than the sun-adapted U olivascens, which resulted in higher thallus absorptance and P-I parameters characterized by higher photosynthetic efficiency at limiting irradiances (alpha) and lower saturating points for photosynthesis (E-k). After 7 d exposure, photoinhibition of F-v/F-m was close to 40-45% in both species. Differences between UV treatments were seen in U. rotundata after 5 0 and after 7 d in U olivascens, in which PAR + UVA impaired strongly photosynthesis (80%). Such patterns were correlated with a progressive decrease in pigment contents, specially chlorophylls. In short-term (6 h) exposures, combinations of UVA + UVB and high PAR level resulted in high rates of photoinhibition of chlorophyll fluorescence (68-92%) in U rotundata, whereas in U. olivascens photoinhibition ranged between 42% and 53%. Photoinhibition under low PAR combined to UV radiation was lower than observed under high PAR. Net O-2-P-max revealed similar response among the species, with maximal photoinhibition rates close to 60% in algae incubated under high PAR + UVA + UVB. In the case of UV exposure in combination with low PAR, the highest photoinhibition rates were measured in U. rotundata.
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| 8. |
- Gasanov, Ralphreed, et al.
(author)
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Comparative study of the water oxidizing reactions and the millisecond delayed chlorophyll fluorescence in photosystem II at different pH
- 2007
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In: Journal of Photochemistry and Photobiology. B. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 86:2, s. 160-164
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Journal article (peer-reviewed)abstract
- Water splitting activity, the multiline EPR signal associated with S2-state of the CaMn4-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5–8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O2 evolution and the multiline EPR signal were inhibited at acidic (pK 5.3) and alkaline (pK 8.1) pH values, and were maximal at pH 6.0–7.0. Our results indicate that the loss of O2 evolution and the S2-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0–8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed.
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| 9. |
- Humble, Mats B.
(author)
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Vitamin D, light and mental health
- 2010
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In: Journal of Photochemistry and Photobiology. B. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 101:2, s. 142-149
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Journal article (peer-reviewed)abstract
- Vitamin D receptors and vitamin D metabolizing enzymes are present in the central nervous system. Calcitriol (the active vitamin D hormone) affects numerous neurotransmitters and neurotrophic factors, relevant for mental disorders. In the case of depressive disorders, considerable evidence supports a role of suboptimal vitamin D levels. However, the data are not conclusive and further studies are necessary. Especially, the relative importance o/f the pineal-melatonin system versus the vitamin D-endocrine system for the pathogenesis of seasonal affective disorders is presently unresolved. Two diagnoses, schizophrenia and autism, have been hypothetically linked to developmental (prenatal) vitamin D deficiency, however, also in adult patients, low levels have been reported, supporting the notion that vitamin D deficiency may not only be a predisposing developmental factor but also relate to the adult patients' psychiatric state. Two cases are described, whose psychiatric improvement coincided with effective treatment of vitamin D deficiency.
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| 10. |
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