Kinetics of Photosynthetic Response to Ultraviolet and Photosynthetically Active Radiation in Synechococcus WH8102 (CYANOBACTERIA)

The picoplanktonic cyanobacteria, Synechococcus spp., (Nägeli) are important contributors to global ocean primary production that can be stressed by solar radiation, both in the photosynthetically active (PAR) and ultraviolet (UV) range. We studied the responses of PSII quantum yield (active fluorescence), carbon fixation (¹⁴C assimilation) and oxygen evolution (membrane inlet mass spectrometry) in Synechococcus WH8102 under moderate UV and PAR. PSII quantum yield decreased during exposure to moderate UV and UV+PAR, with response to the latter being faster (6.4 versus 2.8 min, respectively). Repair processes were also faster when UV+PAR exposure was followed by moderate PAR (1.68 min response time) than when UV was followed by very low PAR (10.5 min response time). For the UV+PAR treatment, the initial decrease in quantum yield was followed by a 50% increase (“rebound”) after 7 min exposure, showing an apparent photoprotection induction. While oxygen uptake increased with PAR, it did not change under UV, suggesting that this oxygen‐dependent mechanism of photoprotection, which may be acting as an electron sink, is not an important strategy against UV. We used propyl gallate, an antioxidant, to test for plastid terminal oxidase (ptox) or ptox‐like enzymes activity, but it caused nonspecific and toxic effects on Synechococcus WH8102.     

FLUORESCENCE RELAXATION KINETICS AND QUANTUM YIELD FROM THE PHYCOBILISOMES OF THE BLUE-GREEN ALGA NOSTOC SP. MEASURED AS A FUNCTION OF SINGLE PICOSECOND PULSE INTENSITY*

Abstract— A detailed experimental study of the effect of intensity of a 6 ps excitation pulse on the decay kinetics and yield from phycobilisomes (PBsomes) is presented. The fluorescence from the c-phycoerythrin (PE) emission from PBsomes was found to decay as a single exponential with a time of 31 ± 4ps for an excitation intensity <10¹⁴ photons/cm² per pulse. The risetime of the c-phycocyanin (PC) and allophycocyanin (APC) emission from PBsomes was found to be 34 ± 13 ps. Therefore, at low excitation intensities, the energy transfer time between the constituent phycobiliproteins, PE and PC, is measured to be 34 ± 13ps from the fluorescence decay time of PE and the fluorescence risetime of the PC and APC emission. The fluorescence yield from the PE emission component in PBsomes was found to be intensity dependent for excitation intensities >10¹⁴ photons/cm². The decrease in yield with increased intensity in this case occurred at a higher intensity than in the isolated phycobiliprotein PE. The fluorescence yield of the PC and APC emission component was also found to decrease markedly with increasing excitation intensity. This is in contrast to the case of the isolated phycobiliprotein APC which showed only a slight quenching of the fluorescence. The higher quenching observed for the APC emission in the PBsome evidences the higher effective absorption of APC via energy transfer from PE to PC and APC.     

Effects of PAR and UV‐B Radiation on Herbal Yield,Bioactive Compounds and Their Antioxidant Capacity of Some Medicinal Plants Under Controlled Environmental Conditions

Photosynthetically active radiation (PAR) and Ultraviolet B (UV‐B) radiation are among the main environmental factors acting on herbal yield and biosynthesis of bioactive compounds in medicinal plants. The objective of this study was to evaluate the influence of biologically effective UV‐B light (280–315 nm) and PAR (400–700 nm) on herbal yield, content and composition, as well as antioxidant capacity of essential oils and polyphenols of lemon catmint (Nepeta cataria L. f. citriodora), lemon balm (Melissa officinalis L.) and sage (Salvia officinalis L.) under controlled greenhouse cultivation. Intensive UV‐B radiation (2.5 kJ m^?2 d^?1) influenced positively the herbal yield. The essential oil content and composition of studied herbs were mainly affected by PAR and UV‐B radiation. In general, additional low‐dose UV‐B radiation (1 kJ m^?2d^?1) was most effective for biosynthesis of polyphenols in herbs. Analysis of major polyphenolic compounds provided differences in sensitivity of main polyphenols to PAR and UV‐B radiation. Essential oils and polyphenol‐rich extracts of radiated herbs showed essential differences in antioxidant capacity by the ABTS system. Information from this study can be useful for herbal biomass and secondary metabolite production with superior quality under controlled environment conditions.     

Effects of Suplementary Ultraviolet‐B Irradiance on Maize Yield and Qualities: A Field Experiment¶

Stratospheric ozone depletion has caused an increase in the amount of ultraviolet‐B (UV‐B) radiation reaching the earth's surface. Numerous investigations have demonstrated that the effect of UV‐B enhancements on plants includes reduction in grain yield, alteration in species competition, susceptibility to disease and changes in plant structure and pigmentation. Many experiments examining UV‐B radiation effects on plants have been conducted in growth chambers or greenhouses. It has been questioned whether the effect of UV‐B radiation on plants can be extrapolated to field responses from indoor studies because of the unnaturally high ratios of UV‐B/ ultraviolet‐A radiation (320–400 nm) and UV‐B/photosynthetically active radiation (PAR) in many indoor studies. Field studies on UV‐B radiation effect on plants have been recommended to use the UV and PAR irradiance provided by natural light. This study reports the growth and yield responses of a maize crop exposed to enhanced UV‐B radiation and the UV‐B effects on aize seed qualities under field conditions. Enhanced UV‐B radiation caused a significant reduction in the dry matter accumulation and the maize yield in turn was affected. With increased UV‐B radiation the flavonoid accumulation in maize leaves increased and the contents of chlorophyll a, b and (a+b) of maize leaves were reduced. The levels of protein, sugar and starch of maize seed decreased with enhanced UV‐B radiation, whereas the level of lysine increased with enhanced UV‐B radiation.     

Variability of Solar Radiation and CDOM in Surface Coastal Waters of the Northwestern Mediterranean Sea

Atmospheric and in‐water solar radiation, including UVR‐B, UVR‐A and PAR, as well as chromophoric dissolved organic matter absorption [a_CDOM(λ)] in surface waters were monthly measured from November 2007 to December 2008 at a coastal station in the Northwestern Mediterranean Sea (Bay of Marseilles, France). Our results showed that the UVR‐B/UVR–A ratio followed the same trend in the atmosphere and at 2 m depth in the water (P < 0.0001) with an increase (eight‐fold higher) during summer. The low diffuse attenuation coefficients for downward irradiance [K_d(λ)] of UVR‐B, UVR‐A and PAR indicated that the waters were highly transparent throughout the year. The relationships between a_CDOM(λ) and K_d(λ) in this oligotrophic system suggested that CDOM contributed to UVR attenuation in the UVA domain, but also played a significant role in PAR attenuation. Mean UV doses received in the mixed layer depth were higher by a factor 1.4–33 relative to doses received at fixed depths (5 and 10 m) in summer (stratified period), while the inverse pattern was found in winter (mixing period). This shows the importance of taking into account the vertical mixing in the evaluation of UVR effects on marine organisms.     

Incident Ultraviolet Irradiances Influence Physiology,Development and Settlement of Larva in the Coral Pocillopora damicornis

Ultraviolet radiation (UVR, 280–400 nm) is one of the potential factors involved in the induction of coral bleaching, loss of the endosymbiotic dinoflagellate Symbiodinium or their photosynthetic pigments. However, little has been documented on its effects on the behavior and recruitment of coral larvae, which sustains coral reef ecosystems. Here, we analyzed physiological changes in larvae of the scleractinian coral Pocillopora damicornis and examined the photophysiological performance of the symbiont algae, following exposure to incident levels of UVR and subsequently observed the development of coral larvae. The endosymbiotic algae exhibited a high sensitivity to UV‐B (295–320 nm) during a 6 h exposure, showing lowered photosynthetic performance per larva and per algal cell, whereas the presence of UV‐A (320–395 nm) significantly stimulated photosynthesis. UVR decreased chlorophyll a concentration only at higher surface temperature or at the higher doses or intensities of UVR. Correlations between UV‐absorbing compound (UVAC) contents or UVR sensitivity and temperature were identified, implying that UVACs might act as a screen or antioxidants in Pocillopora damicornis larvae. Larvae reared under UVR exposures showed lower levels of survivorship, metamorphosis and settlement, with inhibition by UV‐A being much greater than that caused by UV‐B.     

Effects of Salinity and Ultraviolet Radiation on the Bioaccumulation of Mycosporine‐like Amino Acids in Artemia from Lake Urmia (Iran)

We investigated the effects of salinity and artificial UV radiation on the accumulation of mycosporine‐like amino acids (MAAs) in sexual and parthenogenetic Artemia from Lake Urmia. The nauplii hatched from the cysts were cultured until adulthood under two salinities (150 and 250 g L^?1) and two light treatments (PAR and PAR+UVR) in the laboratory. Finally, the Artemia were analyzed for their concentration of MAAs. In most of the cases, the higher salinity level applied was found to increase the MAA concentrations in both Artemia populations significantly. The acquisition efficiency of MAAs in both Artemia populations increased under exposure to UVR‐supplemented photosynthetically active radiation (PAR) compared to those raised under PAR, except for Porphyra‐334. It was observed that combination of UV radiation and elevated salinity significantly increased the bioaccumulation of MAAs. Thus, the presence of these compounds in these populations of Artemia may increase their adaptability for living in high‐UV and high‐salinity conditions prevailing in Lake Urmia. Higher concentrations of MAAs in the parthenogenetic population of Artemia could be probably attributed to its mono sex nature and higher adaptation capacities to extreme environmental conditions.     

Estimating the Diurnal Cycle and Daily Insolation of Ultraviolet and Photosynthetically Active Radiation at the Sea Surface

Accurate determination of the diurnal variability and daily insolation of surface (0⁺) and subsurface (0^?) irradiance are essential to estimate several physical, chemical and biological processes occurring at the surface layer of marine environments. Natural downwelling PAR and spectral UVR were examined on eight occasions at 0⁺ and 0^? to refine empirical models, particularly in the UVR spectrum. The diurnal variability in UVR and PAR were wavelength dependent and were modeled by a sinusoidal equation. The best fit for PAR at 0⁺ and 0^? was the sinusoid power of n = 2 and n = 2.5, respectively. In the UVR spectrum, sinusoids increased as wavelengths decreased ranging from n = 2–5. Higher n values in the UV‐B spectrum suggest sharper increase/decrease near sunrise and sunset hours, ultimately reducing the final value of daily insolation at specified wavelengths. Calculated daily insolation of UV‐B/(UV‐A + PAR) ratio suggests that photoinhibition from exposure to UV‐B occurs within a shorter biologically effective day length than PAR, and is high during summer and low during winter. These results suggest that biogeochemical calculations based on diurnal models of irradiance measurements would benefit from accurate solar noon references and wavelength specificity, particularly in the UVR spectrum.     

Effects of Ultraviolet Radiation (UVA+UVB) and Copper on the Morphology,Ultrastructural Organization and Physiological Responses of the Red Alga Pterocladiella capillacea

The effect of ultraviolet (UV) radiation and copper (Cu) on apical segments of Pterocladiella capillacea was examined under two different conditions of radiation, PAR (control) and PAR+UVA+UVB (PAR+UVAB), and three copper concentrations, ranging from 0 (control) to 0.62, 1.25 and 2.50 μm . Algae were exposed in vitro to photosynthetically active radiation (PAR) at 70 μmol photons m^?2 s^?1, PAR + UVB at 0.35 W m^?2 and PAR +UVA at 0.70 W m^?2 during a 12‐h photocycle for 3 h each day for 7 days. The effects of radiation and copper on growth rates, content of photosynthetic pigments and photosynthetic performance were analyzed. In addition, samples were processed for light and transmission electron microscopy. The content of photosynthetic pigments decreased after exposure to radiation and Cu. Compared with PAR radiation and copper treatments modified the kinetics patterns of the photosynthesis/irradiance curve. The treatments also caused changes in the ultrastructure of cortical and subcortical cells, including increased cell wall thickness and accumulation of plastoglobuli, as well as changes in the organization of chloroplasts. The results indicate that the synergistic interaction between UV radiation and Cu in P. capillacea, led to the failure of protective mechanisms and causing more drastic changes and cellular imbalances.     

The Different Resistance of Two Astragalus Plants to UV‐B Stress is Tightly Associated with the Organ‐specific Isoflavone Metabolism

In this work, the changes in isoflavone levels and the expression of genes involved in their biosynthesis were studied in two Astragalus by UPLC ‐MS and real‐time PCR after 10 days of UV ‐B treatment (λ _max = 313 nm, 804 J m⁻²). Isoflavones were significantly induced by UV ‐B irradiation. The influence might be activated by the regulation of these target genes. Our results indicate that (1) the resistance of Astragalus membranaceus might not be as good as Astragalus mongholicus in the enhanced UV ‐B radiation environment; (2) the enhanced accumulation of calycosin and calycosin‐7‐glucoside with UV ‐B treatment in roots of A. mongholicus might be derived from formononetin which is synthesized in the leaves; (3) the glycosylation process could be stimulated and activated by the enhanced UV ‐B radiation in both A. mongholicus and A. membranaceus . In other words, glycosylation of isoflavones might play a crucial role for two Astragalus plants in response to UV ‐B stress. Overall, this study offered a feasible elicitation strategy to understand the accumulation pattern of isoflavone in A. mongholicus and A. membranaceus , and also provided a reference for the changes in isoflavone levels of Astragalus in UV ‐B enhanced environment in the future.     

FLUORESCENCE RELAXATION KINETICS AND QUANTUM YIELD FROM THE ISOLATED PHYCOBILIPROTEINS OF THE BLUE-GREEN ALGA NOSTOC SP. MEASURED AS A FUNCTION OF SINGLE PICOSECOND PULSE INTENSITY, I

Abstract— Phycobilisomes from the blue-green alga Nostoc sp. are known to contain the phycobiliproteins: c-phycoerythrin (c-PE), c-phycocyanin (c-PC) and four forms of allophycocyanin (APC I, II, III, and B). We have made a detailed study of the effects of the intensity of a single 6 ps excitation pulse on the decay kinetics and the yield of fluorescence in the individual isolated phycobiliproteins at pH 7 and 23°C. The risetime of the fluorescence of c-PE, c-PC and APC was > 12 ps. We found that the decay of the fluorescence was exponential at intensities of 10¹⁴ photons/cm² in all the phycobiliproteins; the lifetimes being 1552 ± 31ps for c-PE, 2111 ± 83ps for c-PC, 1932 ± 165ps for APC I, 1870 ± 90ps for APC II, 1816 ± 88ps for APC III, (1869 ± 62ps for the averaged APC's I, II, and III), and 2667 ± 233 ps for APC B. We also found that the fluorescence decay became non-exponential in c-PE at excitation intensities < 10¹⁴ photons/cm², but was exponential for all the other phycobiliproteins even at a pulse intensity of 10¹⁵ photons/cm². The relaxation times of c-PE and c-PC decreased with excitation intensity above 10¹⁴ photons/cm². For c-PE and c-PC the relative fluorescence vs excitation intensity was readily described by a relationship derived for a model in which exciton–exciton annihilation occurs. In APC the fluorescence yield and relaxation time were only slightly dependent on the excitation intensity. The results are interpreted to indicate the occurrence of singlet–singlet annihilation intramolecularly among the several phycobilin chromophores within the individual phycobiliprotein molecules in solution. The s to f transfer time is less than 12ps in c-PC.     

Stress Tolerance of the Endemic Antarctic Brown Alga Desmarestia anceps to UV Radiation and Temperature is Mediated by High Concentrations of Phlorotannins

The endemic Antarctic brown macroalga Desmarestia anceps is strongly shade‐adapted, but shows also a high capacity to cope with different environmental stressors, e.g. UV radiation and temperature. Therefore, this species colonizes wide depth gradients, which are characterized by changing environmental conditions. In this study, we examine whether the different physiological abilities allowing D. anceps to grow across a wide depth range is determined by high levels of phlorotannins. Photosynthesis, measured by PAM‐fluorometry, the contents of soluble phlorotannins, antioxidant capacities of field grown were analyzed in response to different conditions of radiation (PAR and PAR + UV) and temperature (2, 7 and 12°C). The results show that maximal quantum of fluorescence (F_v/F_m) decreased with increasing doses of UV radiation, but remained unaffected by temperature. High levels of soluble phlorotannins were detected and confirmed by microscopic observation revealing the abundance of large physodes. Exposure to UV radiation and elevated temperature showed that phlorotannins were not inducible by UV but increased at 12°C. ROS scavenging capacity was positively correlated with the contents of phlorotannins. In general, highest contents of phlorotannins were correlated with the lowest inhibition of F_v/F_m in all experimental treatments, highlighting the UV‐protective role of these compounds in D. anceps.     

Solar UV Irradiances Modulate Effects of Ocean Acidification on the Coccolithophorid Emiliania huxleyi

Emiliania huxleyi, the most abundant coccolithophorid in the oceans, is naturally exposed to solar UV radiation (UVR, 280–400 nm) in addition to photosynthetically active radiation (PAR). We investigated the physiological responses of E. huxleyi to the present day and elevated CO₂ (390 vs 1000 μatm; with pH_NBS 8.20 vs 7.86) under indoor constant PAR and fluctuating solar radiation with or without UVR. Enrichment of CO₂ stimulated the production rate of particulate organic carbon (POC) under constant PAR, but led to unchanged POC production under incident fluctuating solar radiation. The production rates of particulate inorganic carbon (PIC) as well as PIC/POC ratios were reduced under the elevated CO₂, ocean acidification (OA) condition, regardless of PAR levels, and the presence of UVR. However, moderate levels of UVR increased PIC production rates and PIC/POC ratios. OA treatment interacted with UVR to influence the alga's physiological performance, leading to reduced specific growth rate in the presence of UVA (315–400 nm) and decreased quantum yield, along with enhanced nonphotochemical quenching, with addition of UVB (280–315 nm). The results clearly indicate that UV radiation needs to be invoked as a key stressor when considering the impacts of ocean acidification on E. huxleyi.     

Latitudinal Gradient of UV Attenuation Along the Highly Transparent Red Sea Basin

The tropical and subtropical oceans experience intense incident ultraviolet radiation (280–400 nm) while their water columns are thought to be highly transparent. This combination represents a high potential for harmful effects on organisms, yet only few reports on the UV penetration properties of oligotrophic tropical waters exist. Here, we present the pattern of UV attenuation over a wide latitudinal range of the oligotrophic Red Sea. We recorded spectroradiometer profiles of PAR and UV, together with chlorophyll‐a (Chl‐a) and light absorption by chromophoric dissolved organic matter (CDOM) to determine the contribution of phytoplankton and CDOM toward UV attenuation. Transparency to UV exhibited a distinct latitudinal gradient, with the lowest and highest diffuse attenuation coefficients at 313 nm (K_d (313)) of 0.130 m^?1 and 0.357 m^?1 observed at the northern coast off Duba, and in the south close to the Farasan islands, respectively. Phytoplankton and CDOM both modulated UV attenuation, but CDOM was found to be the key driver despite the lack of riverine inputs. We confirm that ultraviolet radiation can reach deeper into the Red Sea than previously described, which means its potential to act as a stressor and selective driver for Red Sea organisms may have been underestimated to date.     

Different Photosynthetic Responses of Pyropia yezoensis to Ultraviolet Radiation Under Changing Temperature and Photosynthetic Active Radiation Regimes

Macroalgae play a crucial role in coastal marine ecosystems, but they are also subject to multiple challenges due to tidal and seasonal alterations. In this work, we investigated the photosynthetic response of Pyropia yezoensis to ultraviolet radiation (PAR: 400–700 nm; PAB: 280–700 nm) under changing temperatures (5, 10 and 15°C) and light intensities (200, 500 and 800 μmol photons m^?2 s^?1). Under low light intensity (200 μmol photons m^?2 s^?1), P. yezoensis showed the lowest sensitivity to ultraviolet radiation, regardless of temperature. However, higher temperatures inhibited the repair rates (r) and damage rates (k) of photosystem II (PSII) in P. yezoensis. However, under higher light intensities (500 and 800 μmol photons m^?2 s^?1), P. yezoensis showed higher sensitivity to UV radiation. Both r and the ratio of repair rate to damage rate (r:k) were significantly inhibited in P. yezoensis by PAB, regardless of temperature. In addition, higher temperatures significantly decreased the relative UV‐inhibition rates, while an increased carbon fixation rate was found. Our study suggested that higher light intensities enhanced the sensitivity to UV radiation, while higher temperatures could relieve the stress caused by high light intensity and UV radiation.     

SPECTRAL PROPERTIES OF PHYCOBILISOMES AND PHYCOBILIPROTEINS FROM THE BLUE-GREEN ALGA-NOSTOC SP.*

Abstract— An improved method for phycobilisome isolation from a blue-green alga Nostoc sp. was developed using 1% Triton X-100. The phycobilisome preparations showed little fragmentation and had structures similar in size to those observed in thin sections of the organism. Phycobiliproteins isolated from phycobilisomes and examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis, had subunits with the following molecular weights: phycoerythrin (PE), 20,000 and 16,900; phycocyanin (PC), 14,700 and 16,300; and allophycocyanin (APC), 14,000. Isoelectric focusing of each phycobiliprotein resulted in major bands isoelectric at the following pH values: PE, 4.43, 4.45; PC 4.32; APC, 4.38. Absorption spectra at -196°c showed maxima at 551 and 566 nm for PE; 598 and 631 nm for PC; and 590, 600, 629 and 650 nm for APC. Concentrated vs dilute difference spectra of phycobiliproteins showed increased absorption at 574 nm (PE), 630 nm (PC) and 651 nm (APC) suggesting that spectral changes resulted from aggregation. Fluorescence analysis of each phycobiliprotein and of intact phycobilisome preparations showed that energy absorbed by phycoerythrin is transferred to allophycocyanin, possibly by a resonance transfer mechanism. These observations support a model where allophycocyanin forms the base of the phycobilisome which is attached to the photosynthetic membrane. The next layer is assumed to be phycocyanin, which in turn is followed by a phycoerythrin layer that is the outermost layer (on the stroma side) of the phycobilisome.     

Cellular Changes Associated with the Acclimation of the Intertidal Sea Anemone Actinia tenebrosa to Ultraviolet Radiation

To assess the relative importance of long‐ and short‐term cellular defense mechanisms in seasonally UV‐R‐acclimated Actinia tenebrosa (Anthozoa, Actiniidae), individuals were exposed to summer doses of PAR, UV‐A, UV‐B and enhanced UV‐B (20%) for a period of 4 days. Mycosporine‐like amino acids (MAAs) and cyclobutane pyrimidine dimer (CPD) concentrations were quantified, while oxidative damage to lipids and proteins, and the activities or levels of the antioxidant enzymes SOD, CAT, GR, GPOX and total glutathione were determined. Our results show that summer UV‐R‐acclimated individuals had a higher UV‐R tolerance, with no significant increases in CPDs levels, than winter‐acclimated sea anemones possibly due to higher MAA concentrations. Summer‐acclimated individuals showed increased lipid and protein oxidation and GPOX activity only when they were exposed to UV‐B at 20% above ambient UV‐R levels. In contrast, winter‐acclimated sea anemones showed elevated levels of oxidative damage, GPOX and SOD activities after exposure to UV‐A or UV‐B at ambient and elevated levels. Thus, this study indicates that long‐term UV‐R acclimation mechanisms such as the accumulation of MAAs could be more important than short‐term increases in antioxidant defenses with respect to reducing indirect UV‐R damage in intertidal sea anemones.     

Differential Photosynthetic Response of a Green Tide Alga Ulva linza to Ultraviolet Radiation,Under Short‐ and Long‐term Ocean Acidification Regimes

Both ocean acidification (OA) and solar ultraviolet (UV) radiation can bring about changes in macroalgal physiological performance. However, macroalgal responses to UV radiation when acclimatized to OA under different time scales are rare. Here, we investigate the response of Ulva linza, a green tide alga, to UV radiation in the form of photosynthetically active radiation (PAR) or PAB (PAR+UVA+UVB) radiation. Radiation exposures were assessed following long‐term (from spore to adult stage, 1 month) and short‐term (adult stage, 1 week) OA treatments. Results showed that increased CO₂ decreased the damage rate (k) and repair rate (r) of thalli grown under short‐term OA conditions with PAB treatment, the ratio of r:k was not altered. Following long‐term OA conditions, r was not affected, although k was increased in thalli following PAB treatment, resulting in a reduced ratio of r:k. The relative level of UV inhibition increased and UV‐absorbing compounds decreased when algae were cultured under long‐term OA conditions. The recovery rate of thalli was enhanced when grown under long‐term OA after UV radiation treatment. These results show that blooming algae may be more sensitive to UV radiation in marine environments, but it can develop effective mechanisms to offset the negative effects, reflecting acclimation to long‐term OA conditions.     

An aminoquinoline based fluorescent probe for sequential detection of Znic (II) and inorganic phosphate and application in living cell imaging

A novel fluorescent probe 5‐(diethylamino)‐2‐(((2‐(hydroxymethyl)quinolin‐8‐yl)imino)methyl)phenol ( QS) was synthesized by condensation reaction of 8‐aminoquinoline derivative and 4‐(diethylamino)salicylaldehyde. It was found that the probe QS was capable of high selectivity and sensitivity about specific color and fluorescence changes towards Zn²⁺ ion in EtOH‐H₂O (v/v = 4/1, 0.01 M, Tris–HCl buffer, pH = 7.30) solution. The interaction of QS with Zn²⁺ ion illustrated a “turn‐on” fluorescence response at 550 nm (λ_ex: 458 nm), moreover, after the subsequent addition of inorganic phosphate (Pi) into the solution above, a “turn‐off” fluorescence response was observed. The sensing ability of the probe QS towards Zn²⁺ was confirmed by fluorescence titration, UV–Vis titration and HRMS analysis. Besides, the intracellular sensing behavior of QS with Zn²⁺ and Pi were captured in living PC12 cells. The limit of detection (LOD) for Zn²⁺ and Pi sensing was found to be 0.03 μM and 0.08 μM, respectively.     

The Effects of Ambient Solar UV Radiation on Alkaloid Production by Erythroxylum novogranatense var. novogranatense†

Truxillines are alkaloids produced by Erythroxylum species and are thought to be derived from the UV‐driven dimerization of cinnamoylcocaines. This study was conducted to determine the effects of ambient UV radiation on the production of truxillines in Erythroxylum novogranatense var. novogranatense. Field plants were grown under shelters covered with plastic filters that were transparent to UV radiation, filtered UV‐B, or both filtered UV‐B and UV‐A radiation. The treatments had no significant effect on plant biomass or specific leaf weight. Absorption values in the UV‐C and UV‐A region of acidified‐methanol leaf extracts were higher for plants exposed to UV radiation compared to the no UV radiation treatment. There was a trend in decreasing levels of trans‐cinnamoylcocaine and a statistically significant decrease in levels of cis‐cinnamoylcocaine in the leaves of plants exposed to UV radiation compared to the no UV radiation treatment. Truxilline levels increased in leaves from plants exposed to UV radiation compared to the no UV radiation treatment. Most significantly, the ratio of truxillines to total cinnamoylcocaines in the leaves was affected by UV, increasing with increased UV exposure. The results support the hypothesis that UV radiation is involved in the formation of truxillines from cinnamoylcocaines.