We demonstrate that Blue-diode-based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) of purple sulfur bacteria (Thermochromatium tepidum, Chromatiaceae). Previous studies showed that PAM technology could be used to estimate photosynthesis in purple nonsulfur bacteria and so PAM technology can be used to estimate photosynthesis of both kinds of purple photosynthetic bacteria. The absorptance of Thermochromatium films on glass fiber disks was measured and used to calculate actual ETR. ETR vs Irradiance (P vs E) curves fitted the waiting-in-line model (ETR = (ETRmax × E/Eopt) × exp (1−E/Eopt)). Yield (Y) was only ≈ 0.3–0.4. Thermochromatium saturates at 325 ± 13.8 μmol photons m(−2) s(−1) or ≈15% sunlight and shows photoinhibition at high irradiances. A pond of Thermochromatium would exhibit classic surface inhibition. Photosynthesis is extremely low in the absence of an electron source: ETR increases in the presence of acetate (5 mol m(−3)) provided as an organic carbon source and also increases in the presence of sulfite (3 mol m(−3)) but not sulfide and is only marginally increased by the presence of Fe(2+). Nonphotochemical quenching does occur in Thermochromatium but at very low levels compared to oxygenic photo-organisms or Rhodopseudomonads.

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Functional reassessment of the phosphate-specific chemosensors revealed their potential as arsenate detectors. A series of dipicolylamine (Dpa)-Zn ii chemosensors were screened, among which acridine Dpa-Zn ii chemosensor showed the highest capability in sensing arsenate. the presence of excess Zn ii improved sensitivity and strengthened the binding between acridine Dpa-Zn ii complex to arsenate as well as phosphate. However, due to their response to phosphate, these sensors are not suited for arsenate detection when phosphate is also present. This study demonstrated for the first time that rare-earth elements could effectively mask phosphate, allowing the specific fluorescence detection of arsenate in phosphate-arsenate coexisting systems. in addition, detection of arsenate contamination in the real river water samples and soil samples was performed to prove its practical use. this sensor was further employed for the visualization of arsenate and phosphate uptake in vegetables and flowering plants for the first time, as well as in the evaluation of a potent inhibitor of arsenate/phosphate uptake. Arsenic is a chemical analog of phosphorus that belongs to the same periodic group and shares a number of similarities with phosphorus, including the same number of valence electrons and nearly identical electronegativity (2.18 for As and 2.19 for P) 1. Phosphorus-and arsenic-derived oxoanions, importantly inorganic phosphate (Pi) and arsenate, also exhibit similar properties 2 , such as tetrahedral geometry and close bond lengths (1.69A° and 1.52A° for arsenate (HAsO 4 −) and phosphate (HPO 4 −), respectively) 3 Their acid counterparts also have similar dissociation constants (pK a 2.26, 6.76, and 11.29 for the arsenic acid compared with 2.16, 7.21, and 12.32 for phosphoric acid) 1 , thus possessing the same net charge acr.oss pH values. These salient physiochemical similarities to phosphate make arsenate highly toxic to humans. In addition, arsenate is a confirmed carcinogen and the most significant chemical contaminant in drinking-water worldwide 4. Detection of arsenate has been conventionally conducted by atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICPMS) 5-10. However, the techniques require laborious sample preparation and cannot be employed to visualize biological phenomena in situ. To overcome this problem, several arsenate-specific chemosensors were developed 11-15 , but they were only compatible with organic or aqueous-organic media and can be unstable in water 16. Egdal et al. (2009) reported the divanadyl complex which was able to selectively bind to arsenate over Pi in aqueous solution, but it was optimal at a slightly acidic pH (pH = 3) 17. Therefore, for the purpose of arsenate detection in drinking water and biological systems, a chemosensor that is stable in neutral aqueous solution would be more attractive. Because of the significant roles in biological and environmental systems of the Pi anion, considerable efforts have been devoted to developing methods to d...

Pseudogout is a type of joint inflammations caused by deposition of calcium pyrophosphate (CaPPi) crystals in the affected joint. As Ca 2+ is abundant in the synovial fluid (SF), high levels of soluble PPi in the SF could be one of the key factors that contribute to CaPPi formation in the joint and may serve as a biomarker for pseudogout. Here, we developed and applied an artificial molecular sensor to selective fluorescent detection of soluble PPi in SF of the arthritis patients. The sensor employed xanthene as a fluorophore and the Dpa/Zn(II) as two specific binding sites for PPi. When titrated with serially diluted aqueous PPi solutions, the sensor displayed high sensitivity and exhibited the detection limit of 0.01 µM. The effect of salt concentration was normalized via the concept of Middle Point of Quantification (MPOQ) firstly proposed in this study. The performance of this sensor was also further validated by testing with SF samples extracted from eight clinical patients. The results revealed that six patients had the PPi levels in the range of 60 and 200 µM, indicating moderate likelihood of having pseudogout. Hence, our new method for determining the soluble PPi levels in SF shows promise as a robust, sensitive, and accurate diagnostic tool for the pseudogout.