Photosynthesis of Submerged and Surface Leaves of the Dwarf Water Lily(Nymphoides aquatica)Using PAM Fluorometry

Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)metabolism.Blue-diode based PAM technology was used to measure the Photosynthetic Oxygen Evolution Rate(POER:1O_(2)≡4e^(-)).Optimum Irradiance(E_(opt)),maximum POER(POER_(max))and quantum efficiency(α_(0))all vary on a diurnal cycle.The shape of the POER vs.E curves is different in seedling,submerged and surface leaves.Both E_(opt) and POER_(max) are very low in seedling leaves(E_(opt)≈104μmol photon m^(-2) s^(-1),PPFD;POER_(max)≈4.95µmol O_(2) g^(-1) Chl a s^(-1)),intermediate in mature submerged leaves(E_(opt)≈419µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈38.1µmol O_(2) g^(-1) Chl a s^(-1))and very high in surface leaves(E_(opt)≈923µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈76.1µmol O_(2) g^(-1) Chl a s^(-1)).Leaf titratable acid(C4 acid pool)is too small(≈20 to 50 mol H+m^(-3))to support substantial SAM metabolism.Gross daily photosynthesis of surface leaves is≈3.71 g C m^(-2) d^(-1) in full sun and as much as 1.4 gC m^(-2) d^(-1) in shaded submerged leaves.There is midday inhibition of photosynthesis.

Alternative Methods for Analysis of Cyanobacterial Populations in Drinking Water Supplies: Fluorometric and Toxicological Applications Using Phycocyanin

The management of cyanobacteria and potential exposure to associated biotoxins requires the allocation of scarce resources across a range of freshwater resources within various jurisdictions. Cost effective and reliable methods for sample processing and analysis form the foundation of the protocol yielding reliable data from which to derive important decisions. In this study the utilization of new methods to collect, process and analyze samples enhanced our ability to evaluate cyanobacterial populations. Extraction of phycocyanin using the single freeze thaw method provided more accurate and precise measurements (CV 4.7% and 6.4%), offering a simple and cost-effective means to overcome the influence of morphological variability. In-vacuo concentration of samples prior to ELISA analysis provided a detection limit of 0.001 μg·L?1 MC. Fractionation of samples (?1) = ?0.279 + (1.368 ? Log PC (μg·L?1) while in an Aphanizomemon spp. dominant system Log MC (ng·L?1) = 0.385 + (0.449 ? Log PC (μg·L?1). These methods and sampling protocol could be used in other aquatic systems across a broader regional landscape to estimate the levels of microcystins.

Effects of elevated temperatures on growth and photosynthetic performance of polar Chlorella

Global warming has been the subject of concern in today’s world with elevating temperature causing the melting of polar ice and increasing sea level.The aim of this study was to investigate the physiological and photosynthetic performance of two polar Chlorella,namely Chlorella UMACC 250 and Chlorella UMACC 234 to elevating temperatures as might be experienced under future warming scenarios.The cultures were exposed to three different temperatures of 4℃,8℃and 12℃.The growth and photosynthetic activity were determined every 2 d for a period of 10 d.At the end of the experiment,the cultures were harvested and analysed for biochemical composition.Both Chlorella strains were able to tolerate higher temperatures than their ambient temperature.The final pigments content showed an increasing trend with increased temperatures for both strains.The photosynthetic activities were measured using pulse-amplitude modulation(PAM)fluorometer.The photosynthetic parameters including maximum quantum efficiency(Fv/Fm),maximum relative electron transport rate(r ETRmax),light harvesting efficiency(a)and photoadaptive index(Ek)were derived from the rapid light curves(RLCs).Both Chlorella strains showed a slight decline in growth and photosynthetic activities at the initial part of the experiment.However,they showed the ability to recuperate with Chlorella UMACC 250 recovers better compared to Chlorella UMACC 234.Both Chlorella strains showed similar trend in their carbohydrate content at 12℃,while the protein content of Chlorella UMACC 234 decreased when exposed to increasing temperatures.The results indicated that polar Chlorella are able to survive at increased temperatures throughout the experiment.

Microalgae Cultivation Using Offshore Membrane Enclosures for Growing Algae (OMEGA)

OMEGA is a system for cultivating microalgae using wastewater contained in floating photobioreactors (PBRs) deployed in marine environments and thereby eliminating competition with agriculture for water, fertilizer, and land. The offshore placement in protected bays near coastal cities co-locates OMEGA with wastewater outfalls and sources of CO2-rich flue gas on shore. To evaluate the feasibility of OMEGA, microalgae were grown on secondary-treated wastewater supplemented with simulated flue gas (8.5% CO2 V/V) in a 110-liter prototype system tested using a seawater tank. The flow-through system consisted of tubular PBRs made of transparent linear low-density polyethylene, a gas exchange and harvesting column (GEHC), two pumps, and an instrumentation and control (I&C) system. The PBRs contained regularly spaced swirl vanes to create helical flow and mixing for the circulating culture. About 5% of the culture volume was continuously diverted through the GEHC to manage dissolved oxygen concentrations, provide supplemental CO2, harvest microalgae from a settling chamber, and add fresh wastewater to replenish nutrients. The I&C system controlled CO2 injection and recorded dissolved oxygen levels, totalized CO2 flow, temperature, circulation rates, photosynthetic active radiation (PAR), and the photosynthetic efficiency as determined by fast repetition rate fluorometry. In two experimental trials, totaling 23 days in April and May 2012, microalgae productivity averaged 14.1 ± 1.3 grams of dry biomass per square meter of PBR surface area per day (n = 16), supplemental CO2 was converted to biomass with >50% efficiency, and >90% of the ammonia-nitrogen was recovered from secondary effluent. If OMEGA can be optimized for energy efficiency and scaled up economically, it has the potential to contribute significantly to biofuels production and wastewater treatment.

Simultaneous Determination of Magnolol and Honokiol rby Synchronous Fluorescence Spectroscopy

A simple sensitive and quick assay for simultaneously determining magnolol （MOL） and honokiol （HOL） has been described based on their natural fluorescence. This method is based on the fact that synchronous fluorometry could resolve the overlapping of fluorescence spectra, which was aroused by their similar molecular structures. In this work, the synchronous spectrum, maintaining a constant difference of Aλ =10 nm between the emission and excitation wavelengths, has been selected for the determination of HOL and MOL. Under the optimum conditions, the fluorescence intensity is proportional to the concentration of MOL and HOL in solution over the range 0.075-0.7 μg/mL and 0.05-0.9 μg/mL with the detection limit of 0.029 μg/mL and 0.019 μg/mL, respectively. The method was applied to the simultaneous determination of MOL and HOL in pharmaceutical dosage with satisfactory results.

A novel constitutive promoter and its downstream 5′ UTR derived from cotton(Gossypium spp.) drive high-level gene expression in stem and leaf tissues

The development of genetically modified crops requires new promoters and regulatory regions to achieve high gene ex- pression and/or tissue-specific expression patterns in plants. To obtain promoter sequences of plants with new properties, we analyzed the expression traits of the cotton （Gossypium hirsutum） translation elongation factor 1A gene family. The results showed that the GhEF1A8 gene is highly expressed in different organs of cotton plants, and showed much higher transcript levels in stems and leaves. Its promoter （GhEFIA1.7） and the 5＂ untranslated region （5＂ UTR）, comprising a regulatory region named PGhEFIA8, were isolated from cotton and studied in stably transformed tobacco plants. The regulatory region sequences were fused to the 13-glucuronidase （GUS） reporter gene to characterize its expression pattern in tobacco. Histochemical and fiuorometric GUS activity assays demonstrated that PGhEF1A8 could direct GUS gene expression in all tissues and organs in transgenic tobacco, including leaves, stems, flowers, and roots. The level of GUS activity in the leaves and stems was significantly higher than in cauliflower mosaic virus （CaMV） 35S promoter：：GUS plants, but as same as CaMV 35S promoter：：GUS plants in flower and root tissues. GUS expression levels decreased 2-10-fold when the 5＂ UTR was absent from PGhEF1A8. Deletion analysis of the PGhEFIA8 sequence showed that the region -647 to -323 might possess negative elements that repress transgene expression in tobacco plants. The results suggested that the GhEFIA8 regulation region may represent a practical choice to direct high-level constitutive expression of transgenes and could be a valuable new tool in plant genetic engineering.

Front-Face Fluorescence Using UV-LED Coupled to USB Spectrometer to Discriminate between Virgin Olive Oil from Two Cultivars

A simple setup using a 365 nm LED coupled to a USB spectrometer through an optical fibre, in a front-face fluorescence configuration, was used to investigate the ability of fluorescence spectroscopy technique to discriminate between varieties of olive oil. To achieve this task, Virgin Olive Oils (VOO) from two major Tunisian olive cultivars known as Chetoui and Chemlali were used. Spectral analysis showed a clear separation between these two VOO varieties. A one-way ANOVA attests that this discrimination is significant. The Principal Components Analyses (PCA) showed that the normalized fluorescence intensities are the good parameters for this discrimination. This observation strengthens the potential of our spectral parameters to perform reliable analysis.

通道S1–S4显著的动态变化而非静止状态是香草素类配体激活TRPV1的关键因素

瞬时受体电位香草素1(TRPV1)通道参与了哺乳动物体内许多重要的生理和病理过程,对其门控机制的全面了解有助于为相关疾病的治疗干预提供可能.近年来冷冻电子显微镜(cryo-EM)技术在结构生物学中取得了惊人的成果,所有TRPV亚型(TRPV1±6)的高分辨率结构也得到了解析:它们都具有高度保守的6个跨膜(TM)结构域(S1±S6),与电压门控离子通道(VGICs)相似.并且,在结合了香草素激动剂(辣椒素或树脂毒素)的TRPV1通道开放结构中,TM螺旋S1±S4形成一束,保持静止状态,这也证明了TRP和VGICs通道功能和门控机制的差异.然而,本研究认为S1±S4的动态变化而非静止是辣椒素激活TRPV1的必要条件.通过荧光非天然氨基酸结合和电压钳荧光测量分析,本研究直接观察到辣椒素结合后S1±S4域的运动.电压钳荧光测量法(VCF)所识别位点的化学修饰、单通道记录、细胞凋亡分析和对一种新激动剂PSFL828作用的探索,共同证实了这种协调的S1±S4运动在辣椒素介导的TRPV1激活中的重要作用.这项研究提出了一个新的见解:与冷冻电镜结构研究的结论不同,香草素激动剂在TRPV1激活过程中也需要S1±S4运动.本文重新定义香草素类激动剂的门控过程并发现了新的非香草素类激动剂,为开发TRPV1调节剂提供了新策略.

Emerging approaches to probing ion channel structure and function

Ion channels,as membrane proteins,are the sensors of the cell.They act as the first line of communication with the world beyond the plasma membrane and transduce changes in the external and internal environments into unique electrical signals to shape the responses of excitable cells.Because of their importance in cellular communication,ion channels have been intensively studied at the structural and functional levels.Here,we summarize the diverse approaches,including molecular and cellular,chemical,optical,biophysical,and computational,used to probe the structural and functional rearrangements that occur during channel activation（or sensitization）,inactivation（or desensitization）,and various forms of modulation.The emerging insights into the structure and function of ion channels by multidisciplinary approaches allow the development of new pharmacotherapies as well as new tools useful in controlling cellular activity.

Suppressing the Undulation of Solvent Scattering Light by Constant Magnetic Field

Synchronous fluorometry can cause a band-narrowing effect to improving the fluorometric selectivity (Fig. 1). However, since the △λ value selected is usually small (generally about 0—5 nm) in synchronous scanning, the interference of solvents scattering light (mainly Rayleigh scattering light) is so serious that the sensitivity and the detection limit are harmed greatly.

Investigation on labelling stomach cancer and K562 cell with fluorescence markers

It is very important to quantitate the cytotoxicity of natural killer cell （NK cell） in the fields of cell immune assessment and life science studies. The currently used methods are based on labelling target with radioactivity materials such as 51CrO42-, [3H] thymidine

Accurate and sensitive probing of onset of micellization based on absolute aggregation-caused quenching effect

Probing the onset of micellization,or determining the critical micelle concentration(CMC),is of crucial importance while remains to be challenged by growing demand for extraordinary sensitivity and accuracy.Although fluorometry has attracted wide attention owing to its superiority in simplicity and sensitivity over other methods,the presence and fluctuation of background fluorescence of conventional fluorescent probes undermine the accuracy of CMC determination.Herein,a series of novel fluorescent probes without background fluorescence at a concentration below CMC owing to absolute aggregation-caused quenching(aACQ)are utilized for sensitive and accurate measurement of CMC.The aACQ probes aggregate spontaneously and instantly in an aqueous environment owing to molecular π-π stacking with fluorescence quenching absolutely.Therefore,the absence of background fluorescence at a concentration below CMC clears relevant interference associated with conventional fluorophores.In this study,the new method is applied for versatile surfactants with CMCs ranging from nanomolar to millimolar concentrations,especially copolymers with ultralow CMC.The higher sensitivity and accuracy are highlighted by comparison with conventional probes.