Academic literature on the topic 'Electronic books. Fluorescent probes. DNA probes'

In this study, a convenient assay method has been developed based on labeled functional nucleic acids (H-DNA) and a competitive fluorescent lateral flow immunoassay (CF-LFI) for ampicillin (AMP) detection. Herein, we designed the tunable AMP probes for AMP detection based on the AMP aptamer, and the secondary DNA fragment. The probes can generate tunable signals on the test line (T line) and control line (C line) according to the concentration of AMP. The accuracy of detection was improved by optimizing the tunable AMP probes. Under the optimal conditions, the linear concentration of AMP detection is ranged from 10 to 200 ng/L with a limit of quantitation (LOQ) value of 2.71 ng/L, and the recovery is higher than 80.5 %. Moreover, the developed method shows the potential application for AMP detection in the hospital wastewater.

The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a zoonotic pathogen, has led to the outbreak of coronavirus disease 2019 (COVID-19) pandemic and brought serious threats to public health worldwide. The gold standard method for SARS-CoV-2 detection requires both reverse transcription (RT) of the virus RNA to cDNA and then polymerase chain reaction (PCR) for the cDNA amplification, which involves multiple enzymes, multiple reactions and a complicated assay optimization process. Here, we developed a duplex-specific nuclease (DSN)-based signal amplification method for SARS-CoV-2 detection directly from the virus RNA utilizing two specific DNA probes. These specific DNA probes can hybridize to the target RNA at different locations in the nucleocapsid protein gene (N gene) of SARS-CoV-2 to form a DNA/RNA heteroduplex. DSN cleaves the DNA probe to release fluorescence, while leaving the RNA strand intact to be bound to another available probe molecule for further cleavage and fluorescent signal amplification. The optimized DSN amount, incubation temperature and incubation time were investigated in this work. Proof-of-principle SARS-CoV-2 detection was demonstrated with a detection sensitivity of 500 pM virus RNA. This simple, rapid, and direct RNA detection method is expected to provide a complementary method for the detection of viruses mutated at the PCR primer-binding regions for a more precise detection.

The mercury ion (Hg2+) is one of the heavy metal ions, and its presence in trace amounts can cause physiological damage to an organism. Traditional methods of Hg2+ detection have been useful but have also had numerous limitations and challenges, and as a result, it is important to design new and sophisticated methods that can aid in the detection of Hg2+. In this paper, two fluorescent dyes, carboxyfluorescein (FAM) and SYBR Green I, were used to label and intercalate DNA probes immobilized on the surface of graphene oxide (GO) for sensors to detect Hg2+. FAM and SYBR Green I dye share close excitation and emission wavelength spectra, which can promote and amplify the detection of signals, and also increase the limit of detection (LOD). The results showed that the limit of detection in this method was 0.53 nM. Moreover, when the sensors with double amino groups on the surface of GO were carried out to detect Hg2+, a limit of detection was improved to 0.43 nM. The sensors were then applied in the real sample. The results show that this method has a promising potential in Hg2+ detection.

Since the introduction of super-resolution microscopy, there has been growing interest in quantifying the nanoscale spatial distributions of fluorescent probes to better understand cellular processes and their interactions. One way to check if distributions are correlated or not is to perform colocalization analysis of multi-color acquisitions. Among all the possible methods available to study and quantify the colocalization between multicolor images, there is image cross-correlation spectroscopy (ICCS). The main advantage of ICCS, in comparison with other co-localization techniques, is that it does not require pre-segmentation of the sample into single objects. Here we show that the combination of structured illumination microscopy (SIM) with ICCS (SIM-ICCS) is a simple approach to quantify colocalization and measure nanoscale distances from multi-color SIM images. We validate the SIM-ICCS analysis on SIM images of optical nanorulers, DNA-origami-based model samples containing fluorophores of different colors at a distance of 80 nm. The SIM-ICCS analysis is compared with an object-based analysis performed on the same samples. Finally, we show that SIM-ICCS can be used to quantify the nanoscale spatial distribution of functional nuclear sites in fixed cells.

Abstract Background A recent genome-wide association study (GWAS) including 253 Chinese individuals from Singapore with B-cell Non-Hodgkin Lymphoma (B-NHL), a new susceptibility locus, rs6773853 was identified between BCL6 (B-cell lymphoma protein 6) and LPP (lipoma preferred partner) on chromosome 3q27. This was significantly associated with an increased risk of B-NHL; Odds ratio (OR) per-copy of the risk allele = 1.44 and diffuse large B-cell lymphoma (DLBCL) OR = 1.47. The aims of this study were to determine the prognostic significance of rs6773853 in a case-only analysis of B-NHL patients and to determine if there were any differences in patients and tumor characteristics in B-NHL patients with rs6773853 locus present and absent. Methods Genome-wide genotyping to identify germline mutations from DNA of patients' blood samples have been described. Patient, tumour and treatment data were obtained from clinical and pathology databases as well as electronic and hardcopy of medical records. Fluorescent in-situ hybridization testing for BCL6 translocations using breakapart probes were performed on tumor samples whenever possible. Patients were compared in a two-way (homozygous wild-type [WT] versus presence of 1 or more copies of the risk allele of rs6773853) and three-way (homozygous WT versus heterozygous carrier versus homozygous variant of rs6773853) manner. Prognostic factors were analyzed first by univariate analysis. A multivariate Cox regression model was then fitted including all factors showing statistical significance on univariate analysis to identify the best predictors of overall survival. Results Clinical and pathologic data were available for 245 B-NHL patients in whom GWAS was performed. The minor allele of rs6773853 locus was identified in 127 patients: 100 were homozygous and 27 were heterozygous carriers. The WT genotype was present in 118 patients. There were no statistically significant differences in the clinical and tumor characteristics or treatment received in both 2-way (Table 1) and 3-way analyses. On univariate analysis, age >60 years, ECOG 2–4, B symptoms, advanced stage, aggressive B-NHL, 2 or more extra-nodal sites, elevated LDH, high-risk IPI and a personal history of another cancer were associated with a poorer OS. On multivariate analysis the presence of rs6773853 locus was independently associated with a poorer OS. (Table 2) The frequencies of BCL6 translocations were 17.9% (7/39) and 20.8% (10/48) in the B-NHL with rs6773853 locus absent and present respectively. Conclusions The rs6773853 susceptibility locus to B-NHL is independently prognostic of a poorer OS. This may be related to its close proximity to BCL6, the transcriptional repressor that tightly regulates the germinal centre reaction, although exploratory analysis showed that rs6773853 did not confer a greater risk of BCL6 translocations. Further functional studies and fine mapping will investigate the role of BCL in the tumorigenesis of these B-NHL patients with rs6773853. Disclosures: No relevant conflicts of interest to declare.

Photochemistry is a mature science. A characteristic hallmark of a consolidated scientific discipline is that it increasingly broadens its scope of interests from an initial central core toward the periphery where it interacts with other areas. Most of the current scientific research is characterized by an enriching multidisciplinarity, focusing on topics that combine backgrounds from different fields. In this way, the largest advances are taking place at the interphase between areas where different fields meet.This multidisciplinarity is, I believe, also a characteristic feature of the current situation for photochemistry. Thus, photochemistry was initially focused on the understanding and rationalization at a molecular level of the events occurring after light absorption by simple organic compounds. Molecular organic photochemistry constituted the core of this discipline, and it largely benefited from advances in the understanding of the electronic states provided by quantum mechanics. Later, photochemistry started to grow toward areas such as photobiology, photoinduced electron transfer, supramolecular photochemistry, and photochemistry in heterogeneous media, always expanding its sphere of interest.This context of increasing diversity in topics and specialization is reflected in this issue of Pure and Applied Chemistry. The contributors correspond to some of the plenary plus two invited lectures of the XXth IUPAC Symposium that was held 17ñ22 July in Granada, Spain. The program included plenary and invited lectures and oral contributions grouped in 13 sections covering femtochemistry, photochemistry of biomacromolecules, single-molecule photochemistry, and computational methods in photochemistry to nanotechnology, among others. These workshop titles give an idea of the breadth of themes that were included in this symposium. While it is obvious that the list of contributions correspond to different subdisciplines in photochemistry, all of them have a common scientific framework to rationalize the facts.The purpose of the symposium was to present an overview of the current status of some research fronts in photochemistry. This issue begins with the 2004 Porter Medal Lecture awarded jointly by the Asian, European, and Interamerican Photochemical Societies that was given to Prof. Graham Fleming (University of California, Berkeley) for his continued advances in photosynthesis. Prof. Flemingís studies have constituted a significant contribution to the understanding of the interplay between the structure of photosynthetic centers of green plants and the mechanism of energy migration toward the photosynthetic centers. These events take place in a very short time scale and are governed by the spatial arrangement of the constituents.Continuing with photobiology, the second article by Prof. Jean Cadet (Grenoble University) describes the type of photochemical damage and photoproducts arising from DNA UV irradiation. Knowledge of these processes is important for a better understanding of skin cancer and the possibilities for DNA repair. Closely related with DNA damage occurring upon irradiation, the article by Prof. Tetsuro Majima (Osaka University) provides an account of his excellent work on photosensitized oneelectron oxidation of DNA.The concept of "conical intersection", developed initially by Robb and Bernardi to rationalize the relaxation of excited states, led to the foundation of computational photochemistry, which has proved to be of general application to photochemical reactions. In this issue, Prof. Massimo Olivucci (University of Siena) shows that quantum chemical calculations can also be applied to photochemical reactions occurring in photobiology and, in particular, to the problem of vision. These calculations are characterized by the large number of atoms that are included and the fact that they have to estimate at a high calculation level and with high accuracy the energy of states differring in a few kcal mol-1.The next article corresponds to one of the two invited lectures included in this issue. The one given by Dr. Virginie Lhiaubet-Vallet (Technical University of Valencia) in the workshop Photophysical and Photochemical Approaches in the Control of Toxic and Therapeutic Activity of Drugs describes the enantioselective quenching of chiral drug excited states by biomolecules. Moving from photobiology to free radical polymerization with application in microlithography, the article by Prof. Tito Scaiano (University of Ottawa) reports among other probes an extremely elegant approach to detect the intermediacy of radicals in photochemical reactions based on a silent fluorescent molecular probe containing a free nitroxyl radical.Solar energy storage is a recurrent topic and a long-desired application of photochemistry. In her comprehensive contribution, Prof. Ana Moore (Arizona State University) summarizes the continued seminal contribution of her group to the achievement of an efficient solar energy storage system based on the photochemical generation of long-lived charge-separated states. Another possibility of solar energy storage consists of water splitting. In his article, Prof. Haruo Inoue (Tokyo Metropolitan University) deals with artificial photosynthetic methods based on the use of ruthenium porphyrins as photosensitizers for the two-electron oxidation of water with formation of dioxygen.Also in applied photochemistry, Prof. Luisa De Cola (University of Amsterdam) reports on intramolecular energy transfer in dinuclear metal complexes having a meta-phenylene linker. The systems described by Prof. De Cola have potential application in the field of light-emitting diodes, since most of the complexes described exhibit electroluminescence. The second invited lecture is by Dr. Alberto Credi (University of Bologna), one of Europeís most promising young photochemists. In his interesting article, the operation upon light excitation of a rotaxane molecular machine is described. A macro-ring acting as electron donor moiety in a charge-transfer complex is threaded in a dumbbell-shaped component having two viologen units with different redox potential. Light absorption produces the cyclic movement of the macro-ring from one viologen station to the other.The last two contributions fall within the more classic organic photochemistry realm. Prof. Axel Griesbeck (University of Cologne) describes the multigram synthesis of antimalarial peroxides using singlet-oxygen photosensitizers adsorbed or bonded to polymer matrices. The last contribution comes from Prof. Heinz Roth (University of Rutgers), who has worked during his entire career in the fields of organic photochemistry and radical ion chemistry. Prof. Roth has summarized his vast knowledge in radical ion chemistry, reviewing the mechanism of triplet formation arising from radical ion pair recombination. This mechanism for triplet formation is currently gaining a renewed interest owing to the potential applicability to the development of phosphors.I hope that the present selection will be appealing and attractive for a broad audience of readers interested in photochemistry and will give readers an idea of the state of the art of some current topics in this area.Hermenegildo GarcíaConference Editor

Thesis (Ph. D.)--University of Nevada, Reno, 2005.
"May, 2005." Includes bibliographical references. Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2005]. 1 microfilm reel ; 35 mm.

In the jargon of cytometry, cellular characteristics, such as size, nucleic acid content, and membrane potential, are usually referred to as parameters, a term that is also used for the physical characteristics, such as absorption, light scattering, and fluorescence intensity, that are measured by cytometric instrumentation. Fluorescence, as a physical parameter, plays a key role in the detection of probes on beads for multiplexed analysis. Cellular parameters can be classed as intrinsic or extrinsic. Intrinsic cellular parameters are those that can be measured without the use of a reagent; measurement of extrinsic parameters requires the use of reagents, which are almost always referred to as probes, thereby occasioning confusion among molecular biologists new to cytometry. Cellular parameters are also characterized as structural or functional; DNA and RNA content and the presence and copy number of an antigen or nucleic acid sequence are structural parameters, whereas internal pH, membrane potential, and enzyme activity are functional parameters. The distinction between structural and functional parameters blurs at the edge, but the concept has been generally useful. Fluorescent probes allow measurement of the widest variety of extrinsic cellular parameters. For an atom or molecule to fluoresce, it must first absorb a photon, raising an electron to a higher energy level that is known as an excited state. Excitation by absorption requires only about a femtosecond. Fluorescence occurs when the electron loses all or some of the absorbed energy by emission of a photon. The fluorescence lifetime, that is, the period between excitation and emission, is typically on the order of a few nanoseconds for fluorescent organic materials but is notably longer (hundreds of microseconds) for some materials (e.g., lanthanide chelates). In almost all cases, some of the excitation energy is lost nonradiatively by transitions between different vibrational energy levels of the electronic excited state; this loss requires that the emitted energy be less than the energy absorbed, meaning that the fluorescence emission will be at a longer wavelength than the excitation. The difference between the principal excitation and emission maxima in the fluorescence spectrum is known as the Stokes shift, honoring George Stokes, who first described fluorescence in the mid-1800s. Typical Stokes shifts are no more than a few tens of nanometers.