Succession and physiological health of freshwater microalgal fouling in a Tasmanian hydropower canal

Freshwater microalgal biofouling in hydropower canals in Tarraleah, Tasmania, is dominated by a single diatom species, Gomphonema tarraleahae. The microfouling community is under investigation with the aim of reducing its impact on electricity generation. Species succession was investigated using removable glass slides. Fouled slides were examined microscopically and for chlorophyll a biomass. Chl a biomass increased steeply after 8 weeks (0.09–0.87 mg m^?2), but increased much earlier on slides surrounded by a biofouled inoculum. Succession began with low profile diatoms such as Tabellaria flocculosa, progressing to stalked diatoms such as Gomphonema spp. and Cymbella aspera. Few chlorophytes and no filamentous algae were present. Pulse amplitude modulated fluorometry was used to measure the physiological health of fouling on the canal wall. Maximum quantum yield (F _v/F _m) measurements were consistently <0.18, indicating that the fouling mat consisted of dead or dying algae. The succession and physiological health of cells in the fouling community has broad implications for mitigation techniques used.     

时间分辨荧光分析法在DNA探针检测中的初步应用

应用时间分辨荧光技术进行核酸杂交分析,选用自制整合剂异硫氰酸苯基-EDTA将铕离子标记连接于链霉亲和素分子中,通过光化学反应制备生物素标记pUC118DNA探针,与固定在聚苯乙烯微滴板中的靶DNA杂交后,以铕离子Eu(3+)标记的链霉亲和素为检测物,检测靶DNA的含量,可检测到30pg的靶DNA．     

A CHLOROPHYLL FLUORESCENCE INDEX TO ESTIMATE SHORT‐TERM RATES OF PHOTOSYNTHESIS BY INTERTIDAL MICROPHYTOBENTHOS1

An index based on chl a fluorescence quenching analysis was tested as a predictor of photosynthetic rates of undisturbed intertidal microphytobenthic assemblages. The fluorescence index, P_fluo, was derived from the combination of different chl a fluorescence parameters chosen to represent the two main sources of short‐term variability in the community‐level microphytobenthic photosynthesis: 1) the quantum yield of photosynthesis of the microalgae present in the photic zone of the sediment, φP, and 2) the community‐level efficiency of photosynthetic light absorption, ?, determined by the microalgal concentration in the photic zone. Variations in φP were traced by the fluorescence index ΔF/F_m′ (the effective quantum yield of charge separation at PSII), whereas changes in ? were followed by the fluorescence parameter F_o (dark or minimum fluorescence level). Gross photosynthetic rate, P, and fluorescence parameters were measured nondestructively and simultaneously under in situ conditions, on the same samples, using oxygen microelectrodes and pulse amplitude modulation fluorometry, respectively. Despite the large and uncorrelated hourly variability in irradiance, photosynthetic rate, and fluorescence parameters included in P_fluo, highly significant correlations between P_fluo and P were found for all the sampling periods, encompassing hourly, biweekly, and seasonal time scales. The variability in P explained by P_fluo ranged from 84.3% to 91.4% when sampling periods were considered separately and reached 81.1% when all data were pooled. The results of the study show that despite its simplicity, the index P_fluo can be used to trace short‐term variations in the photosynthetic rate of undisturbed microphytobenthic assemblages undergoing rhythmic vertical migration.     

Phosphorylation mediated structural and functional changes in pentameric ligand-gated ion channels: Implications for drug discovery

Pentameric ligand-gated ion channels (pLGICs) mediate numerous physiological processes, including fast neurotransmission in the brain. They are targeted by a large number of clinically-important drugs and disruptions to their function are associated with many neurological disorders. The phosphorylation of pLGICs can result in a wide range of functional consequences. Indeed, many neurological disorders result from pLGIC phosphorylation. For example, chronic pain is caused by the protein kinase A-mediated phosphorylation of α3 glycine receptors and nicotine addiction is mediated by the phosphorylation of α4- or α7-containing nicotinic receptors. A recent study demonstrated that phosphorylation can induce a global conformational change in a pLGIC that propagates to the neurotransmitter-binding site. Here we present evidence that phosphorylation-induced global conformational changes may be a universal phenomenon in pLGICs. This raises the possibility of designing drugs to specifically treat disease-modified pLGICs. This review summarizes some of the opportunities available in this area.     

Effect of molecular confinement on internal enzyme dynamics: frequency domain fluorometry and molecular dynamics simulation studies

The tryptophanyl emission decay of the mesophilic beta-galactosidase from Aspergillus oryzae free in buffer and entrapped in agarose gel is investigated as a function of temperature and compared to that of the hyperthermophilic enzyme from Sulfolobus solfataricus. Both enzymes are tetrameric proteins with a large number of tryptophanyl residues, so the fluorescence emission can provide information on the conformational dynamics of the overall protein structure rather than that of the local environment. The tryptophanyl emission decays are best fitted by bimodal Lorentzian distributions. The long-lived component is ascribed to close, deeply buried tryptophanyl residues with reduced mobility; the short-lived one arises from tryptophanyl residues located in more flexible external regions of each subunit, some of which are involved in forming the catalytic site. The center of both lifetime distribution components at each temperature increases when going from the free in solution mesophilic enzyme to the gel-entrapped and hyperthermophilic enzyme, thus indicating that confinement of the mesophilic enzyme in the agarose gel limits the freedom of the polypeptide chain. A more complex dependence is observed for the distribution widths. Computer modeling techniques are used to recognize that the catalytic sites are similar for the mesophilic and hyperthermophilic beta-galactosidases. The effect due to gel entrapment is considered in dynamic simulations by imposing harmonic restraints to solvent-exposed atoms of the protein with the exclusion of those around the active site. The temperature dependence of the tryptophanyl fluorescence emission decay and the dynamic simulation confirm that more rigid structures, as in the case of the immobilized and/or hyperthermophilic enzyme, require higher temperatures to achieve the requisite conformational dynamics for an effective catalytic action and strongly suggest a link between conformational rigidity and enhanced thermal stability.     

A METHODOLOGICAL COMPARISON OF PHOTOSYNTHETIC OXYGEN EVOLUTION AND ESTIMATED ELECTRON TRANSPORT RATE IN TROPICAL ULVA (CHLOROPHYCEAE) SPECIES UNDER DIFFERENT LIGHT AND INORGANIC CARBON CONDITIONS1

Gross oxygen evolution was compared with the electron transport rate (ETR), estimated from chl a fluorescence parameters on the common tropical green macro alga Ulva fasciata Delile with confirmatory carbon saturation curves from U. reticulata Forskål. Theoretically, the relationship between estimated ETR and gross oxygen evolution should be 4:1, that is, four electrons are transported through PSII for each molecule of oxygen evolved. However, deviations of the 4:1 relationship have previously been reported. Measurements were conducted with two commercially available and portable pulse amplitude modulated (PAM) chl fluorometers. We sought experimental approaches that minimize discrepancies between the two different measuring techniques of photosynthetic rates, both for in situ and laboratory conditions. Using fresh algal tissue for each of the different irradiances gave the best fit of gross oxygen evolution and ETR even at irradiances above light saturation, where large discrepancies between oxygen evolution and ETR are common. With increasing dissolved inorganic carbon (DIC) concentrations, there was a curvilinear response of gross oxygen evolution in relation to ETR. We therefore suggest to establish DIC saturation curves in the laboratory, oxygen evolution is probably the most relevant choice. Photorespiration could not readily explain a curvilinear response of O₂ evolution and proportionally higher ETR at high irradiances. ETRs measured with the rapid light curve function of the PAM were compared with steady‐state rates of gross and net oxygen evolution, and the ETR was found to decrease at higher irradiances whereas oxygen evolution was constant.     

双链探针同步荧光技术快速筛查C282Y点突变

以荧光染料Fam和Joe分别标记野生型和突变型双链探针作为均相检测探针,以构建的DNA模板作为研究模型,采用固定波长差同步荧光分析法对PCR反应产物进行终点检测。通过对HFE基因C282Y点突变的检测,并以限制性内切核酸酶Rsa I证实,该方法是一种廉价、快速、可靠的筛查遗传性血色病基因C282Y突变的方法,该法可扩展到各种基因的突变检测。     

Chronological change and the potential of recovery on the photosynthetic efficiency of Pyropia yezoensis f. narawaensis (Bangiales) during the sporelings frozen storage treatment in the Japanese Nori cultivation

The chronological change of photosynthetic efficiency in a frozen storage treatment of the Japanese Nori cultivation industry was examined in the cultivated red alga, Pyropia yezoensis f. narawaensis (Saga‐#5 Strain, Bangiales) by using pulse‐amplitude fluorometry. During the desiccation process that was conducted after the nursery cultivation season in November, the maximum quantum yield (F _v/F _m) of the gametophytic sporelings growing on the Nori‐net decreased monotonically with decreasing absolute water content (AWC), and was around 0.1 at 20% AWC. During frozen storage of the Nori‐net, the F _v/F _m of the frozen gametophyte was low but stable, and ranged between 0.10 ± 0.02 SD and 0.14 ± 0.05 SD. The magnitude of F _v/F _m for the gametophyte of the freezing treatment, after 10 min and 3 h of immersion in seawater, recovered quickly. After 10 min and 3 h of immersion, these values were 0.29 ± 0.12 SD and 0.47 ± 0.05 SD during the 14 days of freezing treatment, and 0.15 ± 0.02 SD and 0.29 ± 0.04 SD after 71 days of freezing treatment, and suggest that the ability to recover gradually decreased as the storage duration increased. The response of F _v/F _m from general cultivation (i.e., directly cultivated from the nursery cultivation season) and those after 47 days of freezing were almost identical, suggesting that the current Nori ‐net frozen storage period (6 or 7 weeks) was not detrimental to the gametophyte.     

Photosynthetic rapid light curves (RLC) of Thalassia testudinum exhibit diurnal variation

The use of pulse-amplitude-modulated fluorometry (PAM) and rapid light curves (RLC) were evaluated for monitoring the physiological condition of the seagrass, Thalassia testudinum, at the landscape scale in Florida Bay, USA. PAM fluorometry provides rapid, non-invasive, and quantitative physiological information on the state of photosynthesis. Yet, previous studies of effective and maximum quantum yields have shown that problems arise when expanding measurements from the organismal scale to the landscape scale, mainly due to temporal and irradiance-induced changes in photophysiology. Here, the magnitude of diurnal and spatial variation of photosynthetic characteristics among 10 sample basins and between two sample years was investigated using RLCs. Because RLCs measure effective quantum yields over a range of changing actinic irradiances, we hypothesized that the response parameters might be less sensitive to diurnal light history effects. Our results indicate that the RLC parameters, alpha and ETR_max, significantly changed diurnally, as was previously found for both maximum and effective quantum yields, but the diurnal patterns were variable among the 10 basins. Both among-basin and between-year comparisons were confounded by diurnal variation and statistical analyses comparing morning, mid-day, and afternoon time periods were unable to definitively discern which time of day was best suited for assessing the relative photophysiological status of T. testudinum. However, pooling RLC data at the basin scale revealed among-basin differences and landscape scale trends that were consistent with basin-level morphometric variation in this seagrass. Thus, PAM fluorometry may be useful as a landscape scale monitoring tool within certain constraints. When using this approach over large spatial and temporal scales, diurnal variability must be considered.