Search

Nitric oxide (NO) plays a key role in regulating plant growth, enhances nutrient uptake, and activates disease and stress tolerance mechanisms in most plants. NO is marked as a potential tool for improving the yield and quality of horticultural crop species. Research on NO in plant species can provide an abundance of valuable information regarding this. Hence, we have prepared a simple chemosensor (NPO) for the detection of endogenous NO in chickpea saplings. NPO selectively interacts with NO as determined through a chemodosimetric method to clearly show both the colorimetric and fluorometric changes. After the interaction with NO, the colorless NPO turns yellow as observed by the naked eye and shows bright cyan-blue fluorescence under a UV lamp. The 1 : 1 stoichiometric ratio between NPO and NO is determined from Job's plot resulting in a stable diazeniumdiolate product. The interaction mechanism is well established by absorption, fluorescence titration, NMR titration, HRMS, and DFT calculations. This method has successfully been employed in the plant's root and stem systems to label NO. Confocal microscopy images might help us to understand the endogenous NO generation and the mechanism that happens inside plant tissues.

In this work, we report a bipolar electrode (BPE) array system with self-driven optical readouts of the faradic current flowing through the BPEs. The BPE array system is based on the spontaneous redox reactions that are respectively occurring at opposite poles of the BPEs with appropriate electrocatalysts on the poles; this system is analogous to one consisting of galvanic electrochemical cells. The galvanic BPE array system operates in a self-powered mode that requires there to be neither a direct electrical connection nor external electrical polarization to each BPE. Importantly, the appropriate electrocatalysts on the poles play a critical role in the galvanic BPE array system to induce the spontaneous redox reactions occurring at the poles of BPEs. Moreover, the galvanic BPE array system provides self-driven optical readouts, including fluorometric and colorimetric ones, to report the faradaic current resulting from the spontaneous redox reactions on the BPE poles. Based on the unique benefits that the galvanic BPE array system has over conventional BPEs, we demonstrated the promising potential of galvanic BPE arrays for the simple yet rapid and quantitative screening of electrocatalysts for the oxygen reduction reaction as well as sensitive sensing of H 2 O 2 in parallel.

Thermal shift assay (TSA) with altered temperature has been the most widely used method for monitoring protein stability for drug research. However, there is a pressing need for isothermal techniques as alternatives. This urgent demand arises from the limitations of TSA, which can sometimes provide misleading ranking of protein stability and fail to accurately reflect protein stability under physiological conditions. Although differential scanning fluorimetry has significantly improved throughput in comparison to differential scanning calorimetry and differential static light scattering throughput, all these methods exhibit moderate sensitivity. In contrast, current isothermal chemical denaturation (ICD) techniques may not offer the same throughput capabilities as TSA, but it provides more precise information about protein stability and interactions. Unfortunately, ICD also suffers from limited sensitivity, typically in micromolar range. We have developed a novel method to overcome these challenges, namely throughput and sensitivity. The novel Förster Resonance Energy Transfer (FRET)-Probe as an external probe is highly applicable to isothermal protein stability monitoring but also to conventional TSA. We have investigated ICD for multiple proteins with focus on KRAS G12C with covalent inhibitors and three chemical denaturants performed at nanomolar protein concentration. Data showed corresponding inhibitor-induced stabilization of KRAS G12C to those reported by nucleotide exchange assay., (© 2023. The Author(s).)

Selenium (Se), as one of the essential and nutrient components of living organisms and plants, plays an important role in life activities, while excessive selenium is hazardous to human health. So, the establishment of an effective method for simple, rapid, and highly sensitive determination of selenium content is crucial in the field of food composition analysis and other areas. In this paper, a novel and simple ratiometric fluorescence method for the determination of Se has been developed using 9-anthracenemethanol (AM) as the ratiometric fluorescence reagent on the basis of the conventional fluorometric assay which utilized 2,3-diaminonapthalene (DAN) as fluorescent ligand. The ratiometric method was compared with the conventional method with respect to precision and accuracy. The inter-day and intra-day precisions (RSDs) of the ratiometric fluorescence method ranged from 2.08 to 2.78% and 1.28 to 1.84%, with mean recoveries of 93.2~98.0% and limit of detection (LOD) and limit of quantification (LOQ) of 0.0016 and 0.0049 μg/mL, respectively. This method was successfully applied to the determination of total selenium in selenium-enriched milk and selenium-supplemented shampoo, with the results in agreement with those obtained by inductively coupled plasma mass spectrometer (ICP-MS). The results demonstrated that the precision and accuracy of the ratiometric fluorescence method were superior to those of the conventional fluorescence method, and the interferences of various environmental factors were effectively eliminated. The precision and accuracy of the conventional method can be significantly improved by simply adding an elaborately selected ratiometric fluorescence reagent, and the new method will have broader practical applications.

The iron ion in industrial circulating cooling water is an important indicator for early warning of equipment corrosion and control level. It is interesting to construct an upconversion luminescence iron ion nanoprobe with a common inorganic phosphate water treatment agent. Herein, inorganic phosphate sodium hexametaphosphate (SHMP) was used to regulate the morphology and functionalization of NaYF 4 :Yb 3+ , Er 3+ upconversion luminescent nanoprobe (UCNPs) and applied to fluorometric detection of trace Fe(III) in water based on the fluorescence quenching which is caused by the selective coordination between hexametaphosphate on the surface of UCNPs and Fe(III). The structure, morphology, and luminous intensity of UCNPs were regulated by disodium hydrogen phosphate (ADSP), sodium tripolyphosphate (STPP) and sodium hexametaphosphate(SHMP). The UCNPs functionalized with SHMP has high sensitivity and selectivity for Fe(III) detection. The linear range and detection limit are 1.0-50 μM and 0.2 μM, respectively. The method has satisfactory results for the detection of trace Fe(III) in industrial circulating cooling water., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Manganese oxide nanoparticles (MnO Nps), sonochemical synthesized and characterized in our laboratory, are proposed as fluorescent sensor for selenium (Se) determination. The new methodology has been developed based on the enhancing effect of the Se(IV) on fluorescent emission of MnO Nps. Experimental variables that influence on fluorimetric sensitivity were optimized. The calibration graph using zero th order regression was linear from 0.189 ng L -1 to 8.00 × 10 3  µg L -1 , with correlation coefficient better than 0.99. Under the optimal conditions, the limits of detection and quantification were of 0.062 ng L -1 and 0.189 ng L -1 , respectively. The trueness of the methodology was assessed through standard addition method obtaining recovery near to 100%. This method showed good tolerance to foreign ions, particularly to Se(VI), and was applied to determination of Se(IV) trace in food and drink samples with satisfactory results. With the intention of preserving the environment from harmful effects, a degradation study of the used nanomaterials has been included for their subsequent disposal., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Src-homology-2-domain-containing protein tyrosine phosphatase-2 (SHP2) is a signaling enzyme whose activity is governed by an equilibrium between autoinhibited and activated states. Regulation of SHP2 activity is critical for cellular homeostasis, and mutations that alter its autoregulatory equilibrium cause cancers and developmental disorders. Several methods for assessing the strength of autoinhibitory interactions in SHP2 mutants have been previously reported, but each has limitations. We show that differential scanning fluorimetry provides a rapid, quantitative measure of SHP2 autoinhibition that is independent of the intrinsic activity of the SHP2 mutant being analyzed, does not involve protein labeling, and does not require specialized instrumentation., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Anthony C. Bishop reports financial support was provided by National Institutes of Health., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Liver cancer is one of the most common cancers in the world, and it seriously threatens human life and health. Alpha-fetoprotein (AFP), as a carcinogenic glycoprotein, is an important serum marker for detecting liver cancer. Therefore, the accurate and sensitive determination of AFP is crucial for the early diagnosis and treatment of liver cancer. To this end, a label-free fluorescence aptasensor for detecting AFP based on the use of a novel organic Compound D with an aggregation-induced emission activity and aptamer-modified magnetic microparticles was constructed., Results: Compound D could combine with the complementary short chain of the aptamer (CSC-Apt) of AFP to form the D/CSC-Apt complex and realize the fluorescence enhancement of Compound D. Then, magnetic particles modified by the Apt of AFP (Apt-Fe 3 O 4 ) were prepared. When AFP (or nontarget substance) and D/CSC-Apt were successively added to the Apt-Fe 3 O 4 solution, Apt-Fe 3 O 4 selectively bound to AFP or the D/CSC-Apt complex. Magnetic separation technology showed the changes in the fluorescence intensity of the supernatant. The research results revealed a good linear relationship between the changes in the fluorescence intensity of the supernatant and concentration of AFP within the concentration range of 10-10000 pg mL -1 . The proposed aptasensor could achieve high-sensitivity and high-specificity detection of AFP, and its limit of detection was 3 pg mL -1 (S/N = 3)., Significance and Novelty: The sensor combines the advantages of high selectivity of Apt, high sensitivity of fluorescence analysis, AIE effect and good water solubility of Compound D, and rapid separation using magnetic separation technology. And it can be directly used for the detection of AFP in actual serum samples with high accuracy, whereas most of the methods reported in the literature can only detect AFP in spiked serum samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

The increasing use of pesticides in the agriculture fields strengthen the crop production to meet the needs of increasing population. The residues in water and food materials cause several health hazards. Herein, nitrogen-doped carbon quantum dot (N-CQDs) is designed for determination of methiocarb pesticide in vegetables by fluorescent paper sensor and compared the results with fluorimetry. The fluorescent paper-based detection is performed by recording the change in fluorescence of N-CQDs with introduction of methiocarb using smartphone and ImageJ software. Good linear range was acquired for analysis of methiocarb from 10 to 1000 μgL -1 with a low detection limit (LOD) of 3.5 μgL -1 in fluorimetry; and 700-10,000 μgL -1 with a LOD of 500 μgL -1 in fluorescent paper sensor. A better recovery from 92.0 to 95.4% illustrating the selectivity of both methods for analysis of methiocarb in vegetables. Thus, the advantage of using N-CQDs as a fluorescent sensor for analysis of methiocarb in vegetables is instrument free, portable and user-friendly., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Type 2 diabetes can be cured by using tradjenta (also known as Linagliptin), a new therapeutic drug that is an inhibitor of the dipeptidyl peptidase-4 enzyme. Tradjenta is administered orally alone or in combination with metiguanide or empagliflozin. An easy and specific fluorimetric analysis of Tradjenta was developed and demonstrated in the present investigation. The Hantzsch reaction method, which generates a fluorescent dihydropyridine derivative, is the basis of this assay. In a Toerell-Stenhagen buffered solution, the unsubstituted amine group of Tradjenta interacted with 2,4-Pentadione/Oxomethane. Spectrofluorimetry was utilized for this investigation at an excitation/emission wavelength of 421/480 nm. When comparing the Tradjenta concentration to the tracked fluorimetric signal, the method revealed linearity over the concentration range of 0.05 to 1.2 µg/mL. By strictly altering system parameters and analyzing the validation factors following International Council for Harmonisation (ICH) requirements, the outcomes were achieved. Finally, the proposed approach was successfully applied to assay the drug not only in its raw form and prescribed formulations but also to evaluate the tablet's uniformity of content., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The acquisition of reliable and accurate data to assess environmental changes over large spatial scales is one of the main limitations to determine the impact of eutrophication, and the effectiveness of management strategies in coastal systems. Here, we used a continuous in situ Chl-a fluorometry sensor and L8/OLI satellite data to develop an algorithm and map Chl-a spatial distribution to assess the impact of freshwater diversions and associated high nutrient loading rates in the Barataria Basin (BB) complex, a coastal system in the northern Gulf of Mexico. We collected water quality samples at 24 sampling stations and high-frequency continuous fluorometry in situ [Chl-a] data along a ~87 km transect from 2019–2020. Field [Chl-a] values were highly correlated (r = 0.86; p < 0.0001) with continuous in situ [Chl-a] fluorometry values. These continuous in situ [Chl-a] values were significantly related to a surface reflectance ratio ([B1 + B4]/B3) estimated using L8/OLI data (exponential model; R2 = 0.46; RMSE = 4.8, p < 0.0001). The statistical model replicated [Chl-a] spatial patterns across the BB complex. This work shows the utility of high-frequency continuous Chl-a fluorometry sampling coupled with L8/OLI image analysis to increase the frequency and number of field data sets to assess water quality conditions at large spatial scales in highly dynamic deltaic regions.

Accurate methods to track changes in lake productivity through time and space are critical to fisheries management. Chlorophyll a is the most widely studied proxy for ecosystem primary production and has been the topic of many studies. The main sources of chlorophyll a measurements are ship-based measures or multi-spectral satellite data. Autonomous underwater vehicles can survey large spatial extents approaching the scale of satellite data, but with the accuracy of ship-based water sampling methods. We use several statistical measures to compare measures of chlorophyll a collected in Lake Michigan with spatiotemporally matched satellite-derived measures of chlorophyll a from the MODIS Aqua multi-spectral sensor using NASA's OC3 and the Great Lakes Fit algorithms. Our findings show a near one to one relationship between AUV data and both satellite-derived data sets when the AUV data are coarsened to the resolution of the satellite data. A comparison of satellite-based chlorophyll a to AUV-derived chlorophyll summarized in discrete water depth bins suggested that, based on decreasing coefficients of determination, satellite estimates of chlorophyll accounted for the most variability in chlorophyll a concentrations in the upper 10 m of the water column, even though satellite sensors may detect past this depth. [ABSTRACT FROM AUTHOR]

Background and aims: A large volume of vinasse is generated annually in Argentinean ethanol producing provinces. It has been proposed that vinasses could be used for sugarcane or soybean fertigation. However, basic research to know the effect of vinasse on soil, morphology and crop physiology is scarce in the Argentine northwest. M&M: We provide data on the effect of diluted vinasse (1:1, 1:5 and 1:10 v/v) on photosynthetic CO2 assimilation in soybean plants grown under semicontrolled conditions (greenhouse). Results: Maximum photosynthetic assimilation rate (Amax) was strongly affected by all vinasse dilutions. In the lowest dilution (1:1) the Amax decreased 35% while in highest dilution (1:10) a 15.9% decrease was observed. Changes in Amax were correlated with decreases in stomatal conductance, leaf nitrogen content (Nf) and total chlorophyll. Data of chlorophyll fluorescence show a decrease in Fv/Fm at 1:1 dilution, which indicate a photosystem II (PSII) stress. Conclusions: We can conclude that the application of diluted vinasse affects gas exchange parameters and if it is used it should be done with dilutions 1:10 or higher. Long-term studies are essential to know the effect of vinasse on physicochemical and biological characteristics of soils as well as the probable accumulation of heavy metals in fertirrigated plants. [ABSTRACT FROM AUTHOR]

BACKGROUND: Stress and shear force applied on blood components during processing and storage may induce cellular damage leading to release of cell-free DNA (cfDNA). In this study, we have compared ultraviolet (UV) spectrophotometry with UV-induced fluorescence for the quantification of cfDNA in red cell supernatant. MATERIALS AND METHODS: cfDNA was extracted from 200 μL sample of supernatants from 99 packed red blood cells using QIAamp DNA Blood Mini Kit (Qiagen, Germany). Quantification of cfDNA was done using two different methods: one based on spectrophotometry (NanoDrop 2000c, ThermoFisher Scientific, USA) and another based on fluorometry (Qubit 2.0, Life Technologies, ThermoFisher Scientific, USA). Interassay variability of both the methods was estimated using serial dilutions of standard with known DNA concentration. RESULTS: DNA quantification by both the methods was close to actual amount of known standard in dilutions with higher concentration of DNA (21.68 to 2.71 ng/μl). While at higher dilutions, quantification by NanoDrop was neither precise nor accurate. Median cfDNA concentration in the study units was found to be 1.60 ng/μl (25th–75th percentile range: 1.10–2.10) by UV spectrophotometry (NanoDrop) compared to 0.080 ng/μl (25th–75th percentile range: 0.050–0.130) by fluorometry (Qubit). CONCLUSION: Due to high interassay variability between the two methods and the better precision and accuracy of Qubit, it is recommended that fluorometry-based method be used for the quantification of cfDNA in blood components. [ABSTRACT FROM AUTHOR]

Abstract Infectious bursal disease virus is a causative agent of one of the most important disease which causes frequent tragic disaster in the poultry industry all over the world. Therefore, in the present study a new fluorescence resonance energy transfer-based technique was developed to detect VP2 gene of infectious bursal disease virus using two oligonucleotide probes labeled with quantum dots and rhodamine- immobilized gold nanoparticles (AuNPs-Rh). Quantum dots labeled with an amino-modified first oligonucleotide, and AuNPs-Rh labeled with thiol-modified second oligonucleotides were added to the DNA targets upon which hybridization occurred. In the presence of target the AuNPs-Rh will be located in the vicinity of the quantum dots and leads to the fluorescence resonance energy transfer to be occurred and subsequently the fluorescence intensity of quantum dots was stimulated. The immobilization of rhodamine to the surface of AuNPs increased the fluorescence intensity of rhodamine. The maximum fluorescence resonance energy transfer efficiency for the developed sensor is monitored at a quantum dots-P A /AuNPs-Rh-P T molar ratio of 1:10. Moreover, the feasibility of the developed nanobiosensor was demonstrated by the detection of a synthetic 49-mer nucleotide derived from infectious bursal disease virus and the limit of detection was estimated as 3 × 10−8 M. The developed DNA detection scheme is a simple, rapid and efficient technique which does not need excessive washing and separation steps. Graphical Abstract Unlabelled Image Highlights • A new FRET-based nanosensor is developed for detecting VP2 gene of IBDV. • The accuracy of the newly developed sensor was higher enough to be used for detecting IBDV in the field samples. • AuNPs-coated with rhodamine (AuNPs-Rh) showed higher fluorescence intensity in related to that of un-coated AuNPs. • AuNPs-Rh increased the fluorescence intensity of QDs when located in the proximity of the QDs. [ABSTRACT FROM AUTHOR]

Highlights • Degradation of 3,3′-diaminobenzidine under 500 kHz after 120 min ultrasound exposure. • 3,3′-diaminobenzidine converted to bibenzotriazole due to the presence of NO 2 −. • Bibenzotriazole fluorescence was monitored at 478 nm. Abstract By using 500 kHz high frequency ultrasound (US), 3,3′-diaminobenzidine (DAB) was treated at pH 2 under air atmosphere. The US effect of DAB absorption at 280 nm was composed at 43 and 141 kHz for the detection of fluorescence. When 100 W of US power was used, the DAB absorption band decreased with exposure time. It was noted that, a new absorption broad band at 350 nm–500 nm appeared only under 141 and 500 kHz. Also, fluorescence spectra of the treated DAB were measured when excited at 370 nm. Increasing US exposure time resulted to a broad emission band at 478 nm, indicating that 1H,1′H-5,5′-Bibenzotriazole (BBT) was produced by US exposure at 500 kHz. This product was confirmed by NMR spectroscopy to be a triazine ring formed from NH 2 proton in DAB, due to the formation of nitrite ions in the US aqueous medium at 500 kHz. Hence, DAB was degraded while BBT was formed. [ABSTRACT FROM AUTHOR]

The expression cloning some 25 years ago of the first member of SLC34 solute carrier family, the renal sodium-coupled inorganic phosphate cotransporter (NaPi-IIa) from rat and human tissue, heralded a new era of research into renal phosphate handling by focussing on the carrier proteins that mediate phosphate transport. The cloning of NaPi-IIa was followed by that of the intestinal NaPi-IIb and renal NaPi-IIc isoforms. These three proteins constitute the main secondary-active Na+-driven pathways for apical entry of inorganic phosphate (Pi) across renal and intestinal epithelial, as well as other epithelial-like organs. The key role these proteins play in mammalian Pi homeostasis was revealed in the intervening decades by numerous in vitro and animal studies, including the development of knockout animals for each gene and the detection of naturally occurring mutations that can lead to Pi-handling dysfunction in humans. In addition to characterising their physiological regulation, research has also focused on understanding the underlying transport mechanism and identifying structure-function relationships. Over the past two decades, this research effort has used real-time electrophysiological and fluorometric assays together with novel computational biology strategies to develop a detailed, but still incomplete, understanding of the transport mechanism of SLC34 proteins at the molecular level. This review will focus on how our present understanding of their molecular mechanism has evolved in this period by highlighting the key experimental findings. [ABSTRACT FROM AUTHOR]

Abstract Nanomaterials have been the subject of intense and extensive research in developing various optical sensing tools due to their light dependent remarkable structural and functional attributes. In this review, we conducted a comprehensive and critical assessment of the optical sensing methods (e.g., colorimetry and fluorometry) using various types of nanomaterials (e.g., metal organic frameworks, metal nanoparticles, carbon nanomaterials, quantum dots, chiral molecules, and polymers). Special emphasis was placed on explaining key factors that govern their sensing capabilities, sensing mechanisms, and practical applications toward optical sensing of diverse metal species. Some recent case studies elaborating on the detection of toxic and heavy metal species are described in depth. The discussion is also extended to assess the reliability of nanomaterial-based optical sensing approaches with respect to their performance along with the major challenges and constraints in this research field. Highlights • The practicality of optical sensing toward metal ions is greatly recognized. • Factors governing the optical sensing are assessed against diverse optically active NMs. • The sensing mechanisms for optically active NMs are justifiably described. • Performance of each optical sensing platform is assessed for optimum detection of metals. [ABSTRACT FROM AUTHOR]

Oil dispersion by the application of chemical dispersants is an important tool in oil spill response, but it is difficult to quantify in the field in a timely fashion that is useful for coordinators and decision-makers. One option is the use of rugged portable field fluorometers that can deliver essentially instantaneous results if access is attainable. The United States Coast Guard has suggested, in their Special Monitoring of Applied Response Technologies (SMART) protocols, that successful oil dispersion can be identified by a five-fold increase in oil fluorescence. Here we test three commercial fluorometers with different excitation/emission windows (SeaOWL, Cyclops 7F O, and Cyclops 7F-G) that might prove useful for such applications. Results show that they have significantly different dynamic ranges for detecting oil and that using them (or similar instruments) in combination is probably the best option for successfully assessing the effectiveness of oil dispersion operations. Nevertheless, the rapid dilution of dispersed oil means that measurements must be made within an hour or two of dispersion, suggesting that one feasible scenario would be monitoring ship-applied dispersants by vessels following close behind the dispersant application vessel. Alternatively, autonomous submersibles might be pre-deployed to monitor aerial dispersant application, although the logistical challenges in a real spill would be substantial. • Oil chemical dispersion is difficult to quantify in the field in a timely fashion. • Using portable field fluorometers is useful for monitoring oil chemical dispersion. • Three commercial fluorometers with different excitation/emission windows were tested. • Deployable fluorometers have significantly different dynamic ranges for detecting oil. • Using fluorometers in combination may be best for assessing dispersion's efficacy. [ABSTRACT FROM AUTHOR]

Background: The rapid increase of HIV-1 strains resistant to current antiretroviral drugs is a challenge for successful AIDS therapy. This necessitates the development of novel drugs, and to this end, availability of screening systems for in vitro drug discovery is a priority. Herein, we report the modification of a previously developed system for increased sensitivity, ease of use, and cost-efficiency, based on the application of the EGFP marker. Methods: A PCR-amplified gfp gene (gfp) was cloned into pmzNL4-3, the plasmid already designed to produce single-cycle replicable virions, in frame with the reverse-transcriptase gene to construct the pmzNL4-3/GFP plasmid. GFP-mzNL4-3 pseudo-typed virions, as the first progeny viruses, were recovered from the culture supernatant of HEK293T cells co-transfected with pmzNL4-3/GFP and the helper plasmids pSPAX2 and pMD2G, which respectively encode HIV-1 Gag-Pol and vesicular stomatitis virus glycoprotein. Single-cycle replication and virion production were assessed by syncytia formation, p24 antigen assays, and electron and fluorescence microscopy. Results: The incorporation of EGFP into the viral particles allowed their quantification by fluorometry, flow-cytometry, and fluorescence microscopy; however, this modification did not affect the single-round infectivity or production rate of the GFP fluorescence-emitting virions. Conclusions: Our results certify the development of a rapid, inexpensive, and safe GFP-reporting single-cycle replicable system for anti-HIV drug discovery. Further experiments are needed to measure the validity and robustness of the assay.

We present here a comparative study on the decay of chlorophyll (Chl) a fluorescence yield in thylakoid membranes and photosystem II (PSII)-enriched samples, measured with multifrequency cross-correlation phase fluorometry. These measurements confirm the general conclusions of Van Mieghem et al. (Biochim. Biophys. Acta 1100, 198-206, 1992), obtained with a flash method, on the effects of reduction of the primary quinone acceptor (QA) on Chl a fluorescence yield of PSII. Different states of the reaction centers of PSII were produced by: (1) pretreatment with sodium dithionite and methyl viologen followed by laser illumination: the doubly reduced QA (QAH2) centers; (2) with laser illumination or pretreatment with diuron: QA- centers; and (3) the addition of micromolar concentration of dichlorobenzoquinone (DCBQ): oxidized QA centers. The data were analyzed with Lorentzian distribution as well as with multiexponential fluorescence decay functions. The analysis with Lorentzian distribution function showed that upon formation of QA-, the major lifetime distribution peak shifted to longer lifetimes: from 0.25 ns to 1.66 ns (pea thylakoid membranes) and from 0.24 ns to 1.31 ns (core PSII). However, when QAH2 was formed, the lifetime distribution peaks shifted back to shorter lifetimes (0.57-0.77 ns) both in thylakoids and PSII membranes. Multiexponential analysis showed three lifetime components: fast (40-400 ps), middle (300-1500 ps) and slow (5-25 ns). When QA- was formed in PSII centers, the amplitude of the fast component decreased, but both the amplitude and the lifetime of the middle component increased severalfold.(ABSTRACT TRUNCATED AT 250 WORDS)

We present here a comparative study on the decay of chlorophyll (Chl) a fluorescence yield in thylakoid membranes and photosystem II (PSII)-enriched samples, measured with multifrequency cross-correlation phase fluorometry. These measurements confirm the general conclusions of Van Mieghem et al. (Biochim. Biophys. Acta 1100, 198-206, 1992), obtained with a flash method, on the effects of reduction of the primary quinone acceptor (QA) on Chl a fluorescence yield of PSII. Different states of the reaction centers of PSII were produced by: (1) pretreatment with sodium dithionite and methyl viologen followed by laser illumination: the doubly reduced QA (QAH2) centers; (2) with laser illumination or pretreatment with diuron: QA- centers; and (3) the addition of micromolar concentration of dichlorobenzoquinone (DCBQ): oxidized QA centers. The data were analyzed with Lorentzian distribution as well as with multiexponential fluorescence decay functions. The analysis with Lorentzian distribution function showed that upon formation of QA-, the major lifetime distribution peak shifted to longer lifetimes: from 0.25 ns to 1.66 ns (pea thylakoid membranes) and from 0.24 ns to 1.31 ns (core PSII). However, when QAH2 was formed, the lifetime distribution peaks shifted back to shorter lifetimes (0.57-0.77 ns) both in thylakoids and PSII membranes. Multiexponential analysis showed three lifetime components: fast (40-400 ps), middle (300-1500 ps) and slow (5-25 ns). When QA- was formed in PSII centers, the amplitude of the fast component decreased, but both the amplitude and the lifetime of the middle component increased severalfold.(ABSTRACT TRUNCATED AT 250 WORDS)

Zostera marina is the dominant seagrass species in the Northern Hemisphere where it grows in sheltered bays and estuaries. As a consequence of its distribution its conservation is commonly threatened by poor coastal water quality. The high minimum light requirements of seagrasses results in water quality degradation (high turbidity and eutrophication) being a significant risk. Bioindicators of light stress can be used to interpret seagrass responses to light limitation and therefore act as sentinels for conservation management. However, there exists limited experimental inter-comparison of the effectiveness of multiple individual bioindicator responses. Meta-analysis suggests that rhizome sugars, shoot C:N, shoot growth, and number of leaves per shoot provide the most consistent response variables to increasing light limitation in seagrass, but this premise remains largely untested at the plant level as a direct comparison of multiple bioindicators. The present study aimed to test the morphological, physiological, and photo-physiological bioindicator responses of Z. marina to light stress applied within controlled laboratory conditions. These bioindicators were used to assign minimum light thresholds. Growth rate and photophysiological parameters (alpha, Ek, and ETRmax) were rapidly (1st week) and drastically affected by low light shade treatments (20.12 μmol photons m−2s−1 and lower). After 3 weeks at low light, significant reductions in maximum leaf length and leaf width were observed. Principal Component Analysis identified leaf length, shoot growth, shoot surface area, ETRmax, Ek, and alpha as having the strongest responses to reduced light. Shoot growth, ETRmax, Ek, and alpha were found to provide the best early warning of light limitation after 5–8 days. These results provide evidence for bioindicators of light stress in Z. marina and highlights the importance of understanding these responses for the successful management and conservation of this species.

In this paper we describe a novel approach to study the triplet-state lifetimes by a conventional multifrequency cross-correlation phase and modulation apparatus. The analysis of phase and modulation data of eosin-labeled band 3 erythrocyte ghosts revealed the existence of two phosphorescence lifetime values of 2700 and 750 microseconds, with a fractional contribution of 78 and 22%, respectively, which are in good agreement with those reported in the literature. Differential polarization phase analysis, which facilitates the study of the rotational properties of band 3, provided data in good agreement with those reported in the literature. The method proposed in this paper to study the radiative emission from the triplet state may represent a convenient alternative to the pulse laser flash technique.