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Fluorescence spectroscopy is an important investigational tool in many areas of analytical science, due to its extremely high sensitivity and selectivity.With many uses across a broad range of chemical, biochemical and medical research, it has become an essential investigational technique allowing detailed, real-time observation of the structure.

In vivo chlorophyll fluorescence associated to Photosystem II is being used to evaluate photosynthetic activity of microalgae grown in different types of photobioreactors; however, controversy on methodology is usual. Several recommendations on the use of chlorophyll fluorescence to estimate electron transport rate and productivity of microalgae grown in thin-layer cascade cultivators and methacrylate cylindrical vessels are included. Different methodologies related to the measure of photosynthetic activity in microalgae are discussed: (1) measurement of light absorption, (2) determination of electron transport rates versus irradiance and (3) use of simplified devices based on pulse amplitude modulated (PAM) fluorescence as Junior PAM or Pocket PAM with optical fiber and optical head as measuring units, respectively. Data comparisons of in vivo chlorophyll fluorescence by using these devices and other PAM fluorometers as Water-PAM in the microalga Chlorella sp. (Chlorophyta) are presented. Estimations of carbon production and productivity by transforming electron transport rate to gross photosynthetic rate (as oxygen evolution) using reported oxygen produced per photons absorbed values and carbon photosynthetic yield based on reported oxygen/carbon ratio are also shown. The limitation of ETR as estimator of photosynthetic and biomass productivity is discussed. Low cost:quality PAMs can promote monitoring of chlorophyll fluorescence in algal biotechnology to estimate the photosynthetic activity and biomass productivity.

El objetivo de este trabajo fue determinar el grado de contaminación de sedimentos del cauce aislado del río Lerma que atraviesa la zona metropolitana interestatal La Piedad y Pénjamo, para sustentar la toma de decisiones que haya que emprender con respecto a este cuerpo de agua que interactúa con un ambiente urbano. Se evaluaron parámetros fisicoquímicos, microbiológicos, metales pesados y partículas microscópicas de muestras de sedimentos recolectados en siete sitios del área de estudio. En promedio, los sedimentos tuvieron textura franco arenosa, con pH (7.6) neutro y conductividad eléctrica de 868 µS/cm; mostraron ser medianamente ricos en materia orgánica (2.7 %), con ligera carga de coliformes fecales (753 NMP/100 g), y presentaron un factor de enriquecimiento moderado para Zn, Cr y Cu. Se observaron partículas de plancton, pero también partículas con metales pesados. Considerando que los sitios urbanos (5 y 6) mostraron más indicadores fuera de los criterios establecidos es probable que los sedimentos están recibiendo contaminantes derivados de las actividades antrópicas propias del lugar y no los generados río arriba. En general, la contaminación de los sedimentos fue moderada; no obstante, es imperante limitar que la materia orgánica, microorganismos patógenos y metales tóxicos como el Cr se sigan acumulando en el sedimento y evitar que lleguen a un punto crítico. Por lo anterior y con la aplicación de algunas estrategias será posible recuperar y conservar esta área del río como un cuerpo de agua aislado e independiente del cauce original.

The detection and measurement of the dynamic interactions of proteins within the living cell are critical to our understanding of cell physiology and pathophysiology.With FRET microscopy and spectroscopy techniques, basic and clinical scientists can make such measurements at very high spatial and temporal resolution.

CdSe and CdSe/ZnS (core/shell) quantum dots with oleic acid as stabilizing agent in organic medium were prepared and their optical properties were examined. For CdSe synthesis, the influence of O2 in the growth kinetics of quantum dots was determined. In the first 90 s, the nanocrystals growth was 1.6 higher in presence of O2 than when reaction was carried out in N2 atmosphere. However, the growth rate with O2 is not favorable because the nanocrystal optical properties were affected: wider absorption band and lower fluorescence that those obtained in inert atmosphere. Properties of CdSe nanocrystals synthesized in inert atmosphere were intensified with 10% of monolayer. For a core with 2.5 nm diameter, the fluorescence quantum yield (ΦFl) in the green region increased from 5.5% to 42.3%. In this work, a low Zn2+ (diethylzinc) precursor concentration was used to produce a. The synthesis process of CdSe / ZnS nanocrystals developed with low concentration of Zn2+ and an excess of S2- can be used to obtain materials with excellent photoluminescent properties for applications such as biomarkers, sensors, catalysis, and solar cells.

Deoxynivalenol (DON) is a mycotoxin commonly found in cereals and animal feeds, which also is a carcinogen easily soluble in water. So it has drawn considerable interest in food safety. In this study, a specific aptamer named DON-A16 was developed from an immobilized ssDNA library by affinity chromatography column-based the SELEX. The complementary chain competition method for DON detection was established, and its limit of detection (LOD) was 488 ng/mL. Graphene oxide-based fluorescence quenching was developed using DON-A16 with fluorescein (FAM) label; its LOD was 200 ng/mL, and the detection time was 3 h. The recovery rate of fluorescence quenching was also detected in different samples (oat, wheat flour, corn), which showed the commercial DON ELISA kit led to an increase in repeatability, satisfactory recovery and consistency. The three-dimensional structure and the main binding site of of DON-A16 was ultimately obtained by molecular docking simulation.

Current concern for soil quality has stimulated research on soil organic matter (OM). Humic substances (HS) of different origin were compared applying ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), “steady-state” fluorescence spectroscopy, and 13C nuclear magnetic resonance (13C NMR). Sodium humates samples were isolated from soil (Gleyic Luvisol), compost, and South-Moravian lignite from the mine Mír in Mikulčice. Sodium humates (SH) were extracted by a conventional procedure recommended by the International Humic Substances Society (IHSS). Results showed that the presence of O-containing functional groups (carbonyl in aldehydes and ketones, carboxyl in carboxylic acids, ester and ether groups) are in the order of compost > soil > lignohumate > lignite. Further, results of FTIR, fluorescence spectroscopy, and 13C NMR suggested that samples of sodium humates isolated from soil, compost, and lignite were a more polycondensed, oxidized, unsaturated, humified, and aromatic structure. On the other hand, commercial lignohumate (LH) had very simple structural components and wide molecular heterogeneity. Furthermore, a small molecular size and weight, low degree of aromatic polycondensation, low level of conjugated chromophores and fluorophores, and low humification degree were characteristic for commercial LH. It should be noted that the sample of commercial LH was characterized by 13C NMR analysis with a slightly higher value of aromaticity α in comparison with the sample of compost. The application of non-destructive analytical methods such as UV-VIS, FTIR, 13C NMR, and fluorescence spectroscopy help us to provide main characteristics of selected humic substances.

Aim: This study aimed to establish an enhanced fluorometric assay for directly monitoring atracurium in exhaled breath condensate (EBC). The principal of the technique is the rigidity induced medium in the presence of the sodium dodecyl sulfate (SDS) surfactant which eliminates quenching results from collisional and vibrational conversions. This process causes an improvement in the emission intensity of atracurium. Methods: Fluorescence recordings were made on a spectrofluorometer at 15 ˚C at 310 nm. The crucial factors for reaching to maximum response were investigated and optimized. Results: The technique was validated and the calibration curve was linear in the range of 0.01-2.0 μg·mL-1 of atracurium with a limit of detection of 0.007 μg·mL-1. Finally, the proposed technique was used for the atracurium analysis in EBC of patients receiving the drug. Conclusion: The validated technique was found to be accurate and reliable for the quantification of atracurium from the repeatability and reproducibility points of view.

The phytoene desaturase (PDS) gene of Nicotiana benthamiana was silenced in plants infected with potato virus X (PVX) vectors carrying PDS inserts, and a green fluorescent protein (GFP) transgene was silenced in plants infected with PVX-GFP. This virus-induced gene silencing (VIGS) is post-transcriptional and cytoplasmic because it is targeted against exons rather than introns of PDS RNA and against viral RNAs. Although PDS and GFP RNAs are most likely targeted through the same mechanism, the VIGS phenotypes differed in two respects. PDS mRNA was targeted by VIGS in all green tissue of the PVX-PDS-infected plant, whereas PVX-PDS was not affected. In contrast, VIGS of the GFP was targeted against PVX-GFP. Initially, VIGS of the GFP was initiated in all green tissues, as occurred with PDS VIGS. However, after 30 days of infection, the GFP VIGS was no longer initiated in newly emerging leaves, although it was maintained in tissue in which it had already been initiated. Based on these analyses, we propose a model for VIGS in which the initiation of VIGS is dependent on the virus and maintenance of it is virus independent

Gene silencing is an important but little understood regulatory mechanism in plants. Here we report that a viral sequence, initially identified as a mediator of synergistic viral disease, acts to suppress the establishment of both transgene-induced and virus-induced posttranscriptional gene silencing. The viral suppressor of silencing comprises the 5′-proximal region of the tobacco etch potyviral genomic RNA encoding P1, helper component-proteinase (HC-Pro) and a small part of P3, and is termed the P1/HC-Pro sequence. A reversal of silencing assay was used to assess the effect of the P1/HC-Pro sequence on transgenic tobacco plants (line T4) that are posttranscriptionally silenced for the uidA reporter gene. Silencing was lifted in offspring of T4 crosses with four independent transgenic lines expressing P1/HC-Pro, but not in offspring of control crosses. Viral vectors were used to assess the effect of P1/HC-Pro expression on virus-induced gene silencing (VIGS). The ability of a potato virus X vector expressing green fluorescent protein to induce silencing of a green fluorescent protein transgene was eliminated or greatly reduced when P1/HC-Pro was expressed from the same vector or from coinfecting potato virus X vectors. Expression of the HC-Pro coding sequence alone was sufficient to suppress virus-induced gene silencing, and the HC-Pro protein product was required for the suppression. This discovery points to the role of gene silencing as a natural antiviral defense system in plants and offers different approaches to elucidate the molecular basis of gene silencing.