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Sample records for acid photoluminescence probing

  1. Probing the Influence of Amino Acids on Photoluminescence from Carbon Nanotubes Suspended with DNA.

    PubMed

    Kurnosov, N V; Leontiev, V S; Karachevtsev, V A

    2016-11-01

    The quantitative analysis of amino acid levels in the human organism is required for the early clinical diagnosis of a variety of diseases. In this work the influence of 13 amino acid doping on the photoluminescence (PL) from the semiconducting single-walled carbon nanotubes (SWNTs) suspended with single-stranded DNA (ssDNA) in water has been studied. Amino acid doping leads to the PL enhancement and the strongest increase was found after cysteine doping of the nanotube suspension while addition of other amino acids yielded the significantly smaller effect. The emphasis of cysteine molecules is attributed to presence of the reactive thiol group that turns cysteine into reducing agent that passivates the p-defects on the nanotube sidewall and increases the PL intensity. The reasons of PL enhancement after doping with other amino acids are discussed. The response of nanotube PL to cysteine addition depends on the nanotube aqueous suspension preparation with tip or bath sonication treatment. The enhancement of the emission from different nanotube species after cysteine doping was analyzed too. It was shown that the increase of the carbon nanotube PL at addition of cysteine allows successful monitoring of the cysteine concentration in aqueous solution in the range of 50-1000 μM.

  2. Binding of fullerenes to cadmium sulfide and cadmium selenide surfaces, photoluminescence as a probe of strong, lewis acidity-driven, surface adduct formation

    SciTech Connect

    Zhang, J.Z.; Geselbracht, M.J.; Ellis, A.B.

    1993-08-25

    The C{sub 60} and C{sub 70} fullerenes can be adsorbed from toluene solution onto the surfaces of etched, single-crystal n-CdS and n-CdSe [n-CdS(e)] semiconductors. These fullerene adsorbates act as Lewis acids toward the CdS(e) surface, causing quenching of the solids` band-edge photoluminescence (PL) intensity relative to the intensity in a reference ambient of pure toluene. For C{sub 60} adsorbed onto CdSe, the quenching of PL intensity is well fit by a dead-layer model that permits estimation of the adduct-induced expansion in depletion width as being as large as approximately 300 A. The degree of quenching is somewhat larger for C{sub 70} at a wavelength where the two fullerenes can be directly compared. PL quenching by both fullerenes is concentration dependent and can be fit to the Langmuir adsorption isotherm model to yield large equilibrium binding constants in the range of 10{sup 5} to 10{sup 6} M{sup -1}; the fullerenes can be detected by this PL method at submicromolar concentrations. Use of the polar Cd-rich (0001) and Se-rich (0001O) faces of a n-CdSe sample reveals similar binding constants for C{sub 60} and C{sub 70} on the two faces but larger expansions of the dead-layer thickness from adsorption of either fullerene on the Cd-rich face. 15 refs., 7 figs.

  3. Functionalization of graphene oxide nanostructures improves photoluminescence and facilitates their use as optical probes in preclinical imaging

    NASA Astrophysics Data System (ADS)

    Prabhakar, Neeraj; Näreoja, Tuomas; von Haartman, Eva; Şen Karaman, Didem; Burikov, Sergey A.; Dolenko, Tatiana A.; Deguchi, Takahiro; Mamaeva, Veronika; Hänninen, Pekka E.; Vlasov, Igor I.; Shenderova, Olga A.; Rosenholm, Jessica M.

    2015-06-01

    Recently reported photoluminescent nanographene oxides (nGOs), i.e. nanographene oxidised with a sulfuric/nitric acid mixture (SNOx method), have tuneable photoluminescence and are scalable, simple and fast to produce optical probes. This material belongs to the vast class of photoluminescent carbon nanostructures, including carbon dots, nanodiamonds (NDs), graphene quantum dots (GQDs), all of which demonstrate a variety of properties that are attractive for biomedical imaging such as low toxicity and stable photoluminescence. In this study, the nGOs were organically surface-modified with poly(ethylene glycol)-poly(ethylene imine) (PEG-PEI) copolymers tagged with folic acid as the affinity ligand for cancer cells expressing folate receptors. The functionalization enhanced both the cellular uptake and quantum efficiency of the photoluminescence as compared to non-modified nGOs. The nGOs exhibited an excitation dependent photoluminescence that facilitated their detection with a wide range of microscope configurations. The functionalized nGOs were non-toxic, they were retained in the stained cell population over a period of 8 days and they were distributed equally between daughter cells. We have evaluated their applicability in in vitro and in vivo (chicken embryo CAM) models to visualize and track migratory cancer cells. The good biocompatibility and easy detection of the functionalized nGOs suggest that they could address the limitations faced with quantum dots and organic fluorophores in long-term in vivo biomedical imaging.Recently reported photoluminescent nanographene oxides (nGOs), i.e. nanographene oxidised with a sulfuric/nitric acid mixture (SNOx method), have tuneable photoluminescence and are scalable, simple and fast to produce optical probes. This material belongs to the vast class of photoluminescent carbon nanostructures, including carbon dots, nanodiamonds (NDs), graphene quantum dots (GQDs), all of which demonstrate a variety of properties that are

  4. An integrated photoluminescence sensing platform using a single-multi-mode fiber coupler-based probe.

    PubMed

    Long, Feng; Zhu, Anna; Shi, Hanchang

    2014-03-21

    We demonstrate an integrated fiber optic photoluminescence sensing platform using a novel single-multi-mode fiber coupler (SMFC)-based probe with high collection efficiency for fluorescence signals. The SMFC, prepared using fused biconical taper technology, not only transmits excitation light, but also collects and transmits fluorescence. The entire system does not use complex optical components and rarely requires optical alignment. The simple structure of the SMFC considerably improves the light transmission efficiency, signal-to-noise ratio, and sensitivity of the system. Theoretical and experimental results show that the proposed probe increases the collection efficiency by more than eight-fold compared with a bifurcated fiber probe. The performance of the proposed probe was experimentally evaluated by measuring the fluorescence spectra of well-known targets and a fresh Tall Fescue leaf.

  5. Photoluminescence Probing of Complex H2O Adsorption on InGaN/GaN Nanowires.

    PubMed

    Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Teubert, Jörg; Eickhoff, Martin

    2017-02-08

    We demonstrate that the complex adsorption behavior of H2O on InGaN/GaN nanowire arrays is directly revealed by their ambient-dependent photoluminescence properties. Under low-humidity, ambient-temperature, and low-excitation-light conditions, H2O adsorbates cause a quenching of the photoluminescence. In contrast, for high humidity levels, elevated temperature, and high excitation intensity, H2O adsorbates act as efficient photoluminescence enhancers. We show that this behavior, which can only be detected due to the low operation temperature of the InGaN/GaN nanowires, can be explained on the basis of single H2O adsorbates forming surface recombination centers and multiple H2O adsorbates forming surface passivation layers. Reversible creation of such passivation layers is induced by the photoelectrochemical splitting of adsorbed water molecules and by the interaction of reactive H3O(+) and OH(-) ions with photoactivated InGaN surfaces. Due to electronic coupling of adsorbing molecules with photoactivated surfaces, InGaN/GaN nanowires act as sensitive nanooptical probes for the analysis of photoelectrochemical surface processes.

  6. Functional nucleic acid probes and uses thereof

    DOEpatents

    Nilsen-Hamilton, Marit

    2006-10-03

    The present invention provides functional nucleic acid probes, and methods of using functional nucleic acid probes, for binding a target to carry out a desired function. The probes have at least one functional nucleic acid, at least one regulating nucleic acid, and at least one attenuator. The functional nucleic acid is maintained in an inactive state by the attenuator and activated by the regulating nucleic acid only in the presence of a regulating nucleic acid target. In its activated state the functional nucleic acid can bind to its target to carry out a desired function, such as generating a signal, cleaving a nucleic acid, or catalyzing a reaction.

  7. Probing the photoluminescence properties of gold nanoclusters by fluorescence lifetime correlation spectroscopy

    SciTech Connect

    Yuan, C. T. Lin, T. N.; Shen, J. L.; Lin, C. A.; Chang, W. H.; Cheng, H. W.; Tang, J.

    2013-12-21

    Gold nanoclusters (Au NCs) have attracted much attention for promising applications in biological imaging owing to their tiny sizes and biocompatibility. So far, most efforts have been focused on the strategies for fabricating high-quality Au NCs and then characterized by conventional ensemble measurement. Here, a fusion single-molecule technique combining fluorescence correlation spectroscopy and time-correlated single-photon counting can be successfully applied to probe the photoluminescence (PL) properties for sparse Au NCs. In this case, the triplet-state dynamics and diffusion process can be observed simultaneously and the relevant time constants can be derived. This work provides a complementary insight into the PL mechanism at the molecular levels for Au NCs in solution.

  8. Photoluminescent sensing for acidic amino acids based on the disruption of graphene quantum dots/europium ions aggregates.

    PubMed

    Zhang, Qi; Song, Chan; Zhao, Ting; Fu, Hai-Wei; Wang, Hui-Zhen; Wang, Yong-Jian; Kong, De-Ming

    2015-03-15

    A simple mix-and-detect photoluminescence method was developed for the turn-on detection of acidic amino acids. To achieve this, graphene quantum dots (GQDs), which emit both down-conversion and up-conversion photoluminescence were prepared by solvothermal synthesis. The carboxylic acid-rich surface not only increases the water solubility of the prepared GQDs, but also makes Eu(3+)-triggered GQDs aggregation possible, thus causing the photoluminescence quenching of GQDs. The quenched photoluminescence can be recovered by the competition between acidic amino acids and GQDs for Eu(3+). Under optimized conditions, sensitive and specific acidic amino acids quantitation can be achieved by utilizing the changes in either down-conversion or up-conversion photoluminescence. Up-conversion mode gives a little lower detection limit than the down-conversion one. Nearly overlapped calibration curves were obtained for the two acidic amino acids, glutamic acid (Glu) and aspartic acid (Asp), thus suggesting that the proposed method can be used not only for the quantitation of individual acidic amino acids, but also for the detection of total amount of them.

  9. Monitoring of photoluminescence decay by alkali and alkaline earth metal cations using a photoluminescent bolaamphiphile self-assembly as an optical probe.

    PubMed

    Kim, Sunhyung; Kwak, Jinyoung; Lee, Sang-Yup

    2014-05-01

    Photoluminescence (PL) decay induced by the displacement of an ionic fluorescence component, Tb(3+), with alkali and alkaline earth metal cations was investigated using photoluminescent spherical self-assemblies as optical probes. The photoluminescent spherical self-assembly was prepared by the self-organization of a tyrosine-containing bolaamphiphile molecule with a photosensitizer and Tb(3+) ion. The lanthanide ion, Tb(3+), electrically bound to the carboxyl group of the bolaamphiphile molecule, was displaced by alkali and alkaline earth metal cations that had stronger electrophilicity. The PL of the self-assembly decayed remarkably due to the substitution of lanthanide ions with alkali and alkaline earth metal cations. The PL decay showed a positive correlation with cation concentration and was sensitive to the cation valency. Generally, the PL decay was enhanced by the electrophilicity of the cations. However, Ca(2+) showed greater PL decay than Mg(2+) because Ca(2+) could create various complexes with the carboxyl groups of the bolaamphiphile molecule. Microscopic and spectroscopic investigations were conducted to study the photon energy transfer and displacement of Tb(3+) by the cation exchange. This study demonstrated that the PL decay by the displacement of the ionic fluorescent compound was applied to the detection of various cations in aqueous media and is applicable to the development of future optical sensors.

  10. Nucleic acid probes in diagnostic medicine

    NASA Technical Reports Server (NTRS)

    Oberry, Phillip A.

    1991-01-01

    The need for improved diagnostic procedures is outlined and variations in probe technology are briefly reviewed. A discussion of the application of probe technology to the diagnosis of disease in animals and humans is presented. A comparison of probe versus nonprobe diagnostics and isotopic versus nonisotopic probes is made and the current state of sequence amplification is described. The current market status of nucleic acid probes is reviewed with respect to their diagnostic application in human and veterinary medicine. Representative product examples are described and information on probes being developed that offer promise as future products is discussed.

  11. A dioxaborine cyanine dye as a photoluminescence probe for sensing carbon nanotubes.

    PubMed

    Al Araimi, Mohammed; Lutsyk, Petro; Verbitsky, Anatoly; Piryatinski, Yuri; Shandura, Mykola; Rozhin, Aleksey

    2016-01-01

    The unique properties of carbon nanotubes have made them the material of choice for many current and future industrial applications. As a consequence of the increasing development of nanotechnology, carbon nanotubes show potential threat to health and environment. Therefore, development of efficient method for detection of carbon nanotubes is required. In this work, we have studied the interaction of indopentamethinedioxaborine dye (DOB-719) and single-walled carbon nanotubes (SWNTs) using absorption and photoluminescence (PL) spectroscopy. In the mixture of the dye and the SWNTs we have revealed new optical features in the spectral range of the intrinsic excitation of the dye due to resonance energy transfer from DOB-719 to SWNTs. Specifically, we have observed an emergence of new PL peaks at the excitation wavelength of 735 nm and a redshift of the intrinsic PL peaks of SWNT emission (up to 40 nm) in the near-infrared range. The possible mechanism of the interaction between DOB-719 and SWNTs has been proposed. Thus, it can be concluded that DOB-719 dye has promising applications for designing efficient and tailorable optical probes for the detection of SWNTs.

  12. A dioxaborine cyanine dye as a photoluminescence probe for sensing carbon nanotubes

    PubMed Central

    Lutsyk, Petro; Verbitsky, Anatoly; Piryatinski, Yuri; Shandura, Mykola

    2016-01-01

    The unique properties of carbon nanotubes have made them the material of choice for many current and future industrial applications. As a consequence of the increasing development of nanotechnology, carbon nanotubes show potential threat to health and environment. Therefore, development of efficient method for detection of carbon nanotubes is required. In this work, we have studied the interaction of indopentamethinedioxaborine dye (DOB-719) and single-walled carbon nanotubes (SWNTs) using absorption and photoluminescence (PL) spectroscopy. In the mixture of the dye and the SWNTs we have revealed new optical features in the spectral range of the intrinsic excitation of the dye due to resonance energy transfer from DOB-719 to SWNTs. Specifically, we have observed an emergence of new PL peaks at the excitation wavelength of 735 nm and a redshift of the intrinsic PL peaks of SWNT emission (up to 40 nm) in the near-infrared range. The possible mechanism of the interaction between DOB-719 and SWNTs has been proposed. Thus, it can be concluded that DOB-719 dye has promising applications for designing efficient and tailorable optical probes for the detection of SWNTs. PMID:28144547

  13. Time-integrated photoluminescence and pump-probe reflection spectroscopy of Si doped InN thin films

    SciTech Connect

    Mohanta, Antaryami; Jang, Der-Jun Wang, Ming-Sung; Tu, L. W.

    2014-01-28

    Temperature and excitation power dependent time-integrated photoluminescence of Si doped InN thin films are investigated. Photoluminescence (PL) spectra at low temperatures are described by single emission peak ensued due to “free-to-bound” recombination; whereas PL spectra at higher temperatures above 150 K are characterized by both “band-to-band” and “free-to-bound” transition. Carrier dynamics of Si doped InN thin films is studied using pump-probe reflection spectroscopy at room temperature. The hot electron cooling process is well described by electron-electron scattering. The dependence of the hot electron cooling rate on total electron density shows sublinear to linear behavior with increase of background electron density. The variation of the carrier recombination lifetime with total electron density implicates the dominance of the defect-related nonradiative recombination channel over other recombination processes.

  14. Fluorescent hybridization probes for nucleic acid detection.

    PubMed

    Guo, Jia; Ju, Jingyue; Turro, Nicholas J

    2012-04-01

    Due to their high sensitivity and selectivity, minimum interference with living biological systems, and ease of design and synthesis, fluorescent hybridization probes have been widely used to detect nucleic acids both in vivo and in vitro. Molecular beacons (MBs) and binary probes (BPs) are two very important hybridization probes that are designed based on well-established photophysical principles. These probes have shown particular applicability in a variety of studies, such as mRNA tracking, single nucleotide polymorphism (SNP) detection, polymerase chain reaction (PCR) monitoring, and microorganism identification. Molecular beacons are hairpin oligonucleotide probes that present distinctive fluorescent signatures in the presence and absence of their target. Binary probes consist of two fluorescently labeled oligonucleotide strands that can hybridize to adjacent regions of their target and generate distinctive fluorescence signals. These probes have been extensively studied and modified for different applications by modulating their structures or using various combinations of fluorophores, excimer-forming molecules, and metal complexes. This review describes the applicability and advantages of various hybridization probes that utilize novel and creative design to enhance their target detection sensitivity and specificity.

  15. Structural tuning of photoluminescence in nanoporous anodic alumina by hard anodization in oxalic and malonic acids.

    PubMed

    Santos, Abel; Alba, Maria; Rahman, Mahbubur M; Formentín, Pilar; Ferré-Borrull, Josep; Pallarès, Josep; Marsal, Lluis F

    2012-04-19

    We report on an exhaustive and systematic study about the photoluminescent properties of nanoporous anodic alumina membranes fabricated by the one-step anodization process under hard conditions in oxalic and malonic acids. This optical property is analysed as a function of several parameters (i.e. hard anodization voltage, pore diameter, membrane thickness, annealing temperature and acid electrolyte). This analysis makes it possible to tune the photoluminescent behaviour at will simply by modifying the structural characteristics of these membranes. This structural tuning ability is of special interest in such fields as optoelectronics, in which an accurate design of the basic nanostructures (e.g. microcavities, resonators, filters, supports, etc.) yields the control over their optical properties and, thus, upon the performance of the nanodevices derived from them (biosensors, interferometers, selective filters, etc.).

  16. Structural tuning of photoluminescence in nanoporous anodic alumina by hard anodization in oxalic and malonic acids

    PubMed Central

    2012-01-01

    We report on an exhaustive and systematic study about the photoluminescent properties of nanoporous anodic alumina membranes fabricated by the one-step anodization process under hard conditions in oxalic and malonic acids. This optical property is analysed as a function of several parameters (i.e. hard anodization voltage, pore diameter, membrane thickness, annealing temperature and acid electrolyte). This analysis makes it possible to tune the photoluminescent behaviour at will simply by modifying the structural characteristics of these membranes. This structural tuning ability is of special interest in such fields as optoelectronics, in which an accurate design of the basic nanostructures (e.g. microcavities, resonators, filters, supports, etc.) yields the control over their optical properties and, thus, upon the performance of the nanodevices derived from them (biosensors, interferometers, selective filters, etc.) PMID:22515214

  17. Peptide nucleic acid probes with charged photocleavable mass markers

    PubMed Central

    Ball, Rachel J; Green, Philip S; Gale, Nittaya; Langley, G John

    2010-01-01

    Halogen-labelled peptide organic acid (HPOA) monomers have been synthesised and incorporated into sequence-specific peptide nucleic acid (PNA) probes. Three different types of probe have been prepared; the unmodified PNA probe, the PNA probe with a mass marker, and the PNA probe with photocleavable mass marker. All three types of probe have been used in model studies to develop a mass spectrometry-based hybridisation assay for detection of point mutations in DNA. PMID:21687524

  18. High excitation photoluminescence effects as a probing tool for the growth of Cu(In,Ga)Se2

    NASA Astrophysics Data System (ADS)

    Moret, Matthieu; Briot, Olivier; Gil, Bernard; Lepetit, Thomas; Arzel, Ludovic; Barreau, Nicolas

    2015-03-01

    Copper Indium Gallium deSelenide (Cu(In,Ga)Se2, CIGS) is a promising material for cost-efficient solar cells. Efficiencies above 20% have already been demonstrated in laboratory, and large area CIGS solar panels are already on the market. However, it is still an interesting issue to find efficient characterization techniques that can be used to validate the quality of the different layers at any step of the process, without having to process a complete cell and measure its electrical properties. In this work, we have deposited CIGS onto Mo coated soda lime glass by co-evaporation, using the so-called three step deposition process. Then, photoluminescence (PL) measurements were made on the samples, in the range of 10K to the room temperature, and the excitation intensity was varied in a very large range, in order to reach non-linear regime. We report the first observation of stimulated emission in mechanisms are discussed. The threshold at which sample photoluminescence changes from spontaneous to stimulated is well known to be sensitive to overall sample quality, and we propose to use this measurement as a probing tool for sample quality. This opens an interesting perspective for characterization of CIGS during solar cell processing.

  19. Temperature-dependent photoluminescence of cadmium-free Cu-Zn-In-S quantum dot thin films as temperature probes.

    PubMed

    Wang, Lan; Kang, Xiaojiao; Huang, Lijian; Pan, Daocheng

    2015-12-21

    We reported temperature-dependent photoluminescence (PL) studies on Cu-Zn-In-S quantum dot (QD) thin films. In this paper, cadmium-free and luminescent Cu-Zn-In-S quantum dot thin films were in situ formed by thermal decomposition of molecular-based precursors in the open air, without need of the complicated quantum dot synthesis. Molecular-based precursor solutions were prepared by dissolving Cu2O, ZnO, and In(OH)3 in the ethanol solution of butylamine and carbon disulfide. The effects of sintering temperature, sintering time, and the concentration of capping agents on the photoluminescence properties of Cu-Zn-In-S QD thin films have been systematically investigated. It was found that alkali metal ions play an important role in enhancing the PL quantum yield of quantum dot thin films. The as-prepared QD thin films show composition-tunable emission in the range of 535 nm to 677 nm, and the absolute PL quantum yields can reach as high as 22.1%. All of the as-deposited QD thin films show a single-exponential decay to temperature, indicating that these cadmium-free QD thin films have high potential as temperature probes.

  20. Electric Field Modulation of Semiconductor Quantum Dot Photoluminescence: Insights Into the Design of Robust Voltage-Sensitive Cellular Imaging Probes.

    PubMed

    Rowland, Clare E; Susumu, Kimihiro; Stewart, Michael H; Oh, Eunkeu; Mäkinen, Antti J; O'Shaughnessy, Thomas J; Kushto, Gary; Wolak, Mason A; Erickson, Jeffrey S; Efros, Alexander L; Huston, Alan L; Delehanty, James B

    2015-10-14

    The intrinsic properties of quantum dots (QDs) and the growing ability to interface them controllably with living cells has far-reaching potential applications in probing cellular processes such as membrane action potential. We demonstrate that an electric field typical of those found in neuronal membranes results in suppression of the QD photoluminescence (PL) and, for the first time, that QD PL is able to track the action potential profile of a firing neuron with millisecond time resolution. This effect is shown to be connected with electric-field-driven QD ionization and consequent QD PL quenching, in contradiction with conventional wisdom that suppression of the QD PL is attributable to the quantum confined Stark effect.

  1. Chemically modulated graphene quantum dot for tuning the photoluminescence as novel sensory probe

    NASA Astrophysics Data System (ADS)

    Hwang, Eunhee; Hwang, Hee Min; Shin, Yonghun; Yoon, Yeoheung; Lee, Hanleem; Yang, Junghee; Bak, Sora; Lee, Hyoyoung

    2016-12-01

    A band gap tuning of environmental-friendly graphene quantum dot (GQD) becomes a keen interest for novel applications such as photoluminescence (PL) sensor. Here, for tuning the band gap of GQD, a hexafluorohydroxypropanyl benzene (HFHPB) group acted as a receptor of a chemical warfare agent was chemically attached on the GQD via the diazonium coupling reaction of HFHPB diazonium salt, providing new HFHPB-GQD material. With a help of the electron withdrawing HFHPB group, the energy band gap of the HFHPB-GQD was widened and its PL decay life time decreased. As designed, after addition of dimethyl methyl phosphonate (DMMP), the PL intensity of HFHPB-GQD sensor sharply increased up to approximately 200% through a hydrogen bond with DMMP. The fast response and short recovery time was proven by quartz crystal microbalance (QCM) analysis. This HFHPB-GQD sensor shows highly sensitive to DMMP in comparison with GQD sensor without HFHPB and graphene. In addition, the HFHPB-GQD sensor showed high selectivity only to the phosphonate functional group among many other analytes and also stable enough for real device applications. Thus, the tuning of the band gap of the photoluminescent GQDs may open up new promising strategies for the molecular detection of target substrates.

  2. Chemically modulated graphene quantum dot for tuning the photoluminescence as novel sensory probe

    PubMed Central

    Hwang, Eunhee; Hwang, Hee Min; Shin, Yonghun; Yoon, Yeoheung; Lee, Hanleem; Yang, Junghee; Bak, Sora; Lee, Hyoyoung

    2016-01-01

    A band gap tuning of environmental-friendly graphene quantum dot (GQD) becomes a keen interest for novel applications such as photoluminescence (PL) sensor. Here, for tuning the band gap of GQD, a hexafluorohydroxypropanyl benzene (HFHPB) group acted as a receptor of a chemical warfare agent was chemically attached on the GQD via the diazonium coupling reaction of HFHPB diazonium salt, providing new HFHPB-GQD material. With a help of the electron withdrawing HFHPB group, the energy band gap of the HFHPB-GQD was widened and its PL decay life time decreased. As designed, after addition of dimethyl methyl phosphonate (DMMP), the PL intensity of HFHPB-GQD sensor sharply increased up to approximately 200% through a hydrogen bond with DMMP. The fast response and short recovery time was proven by quartz crystal microbalance (QCM) analysis. This HFHPB-GQD sensor shows highly sensitive to DMMP in comparison with GQD sensor without HFHPB and graphene. In addition, the HFHPB-GQD sensor showed high selectivity only to the phosphonate functional group among many other analytes and also stable enough for real device applications. Thus, the tuning of the band gap of the photoluminescent GQDs may open up new promising strategies for the molecular detection of target substrates. PMID:27991584

  3. Continuously tunable nucleic acid hybridization probes.

    PubMed

    Wu, Lucia R; Wang, Juexiao Sherry; Fang, John Z; Evans, Emily R; Pinto, Alessandro; Pekker, Irena; Boykin, Richard; Ngouenet, Celine; Webster, Philippa J; Beechem, Joseph; Zhang, David Yu

    2015-12-01

    In silico-designed nucleic acid probes and primers often do not achieve favorable specificity and sensitivity tradeoffs on the first try, and iterative empirical sequence-based optimization is needed, particularly in multiplexed assays. We present a novel, on-the-fly method of tuning probe affinity and selectivity by adjusting the stoichiometry of auxiliary species, which allows for independent and decoupled adjustment of the hybridization yield for different probes in multiplexed assays. Using this method, we achieved near-continuous tuning of probe effective free energy. To demonstrate our approach, we enforced uniform capture efficiency of 31 DNA molecules (GC content, 0-100%), maximized the signal difference for 11 pairs of single-nucleotide variants and performed tunable hybrid capture of mRNA from total RNA. Using the Nanostring nCounter platform, we applied stoichiometric tuning to simultaneously adjust yields for a 24-plex assay, and we show multiplexed quantitation of RNA sequences and variants from formalin-fixed, paraffin-embedded samples.

  4. Photoluminescence of porous silicon as an indicator of its interaction with nucleic acids

    NASA Astrophysics Data System (ADS)

    Shevchenko, Victoriya B.; Dacenko, Oleksandr; Makara, Volodymyr; Golovynskyi, Sergii L.; Golovynska, Iuliia

    2017-01-01

    Changes in photoluminescence (PL) of porous silicon (PS), induced by treatment of its surface with nucleic acid solutions, were studied. It was found that such a treatment lead to an increase in PS PL intensity and shift of its peak to shorter wavelengths; the changes were shown to be dependent on the nucleic acid concentration in solution. Treatment with the solution of double-stranded DNA resulted in stronger change in PL than that caused by solution of single-stranded molecules of polynucleotide poly(A). Changes in the surface states of PS produced by the PS treatment with DNA solutions were investigated by means of infrared and electron paramagnetic resonance spectroscopy. The observed changes were explained by the PS oxidation. The presence of the nucleic acids in the aqueous solution significantly accelerates the PS oxidation process. A possible mechanism of the polynucleotide effect on the PS PL was discussed.

  5. CdSe/CdS/ZnS double shell nanorods with high photoluminescence efficiency and their exploitation as biolabeling probes.

    PubMed

    Deka, Sasanka; Quarta, Alessandra; Lupo, Maria Grazia; Falqui, Andrea; Boninelli, Simona; Giannini, Cinzia; Morello, Giovanni; De Giorgi, Milena; Lanzani, Guglielmo; Spinella, Corrado; Cingolani, Roberto; Pellegrino, Teresa; Manna, Liberato

    2009-03-04

    We report the synthesis, the structural and optical characterization of CdSe/CdS/ZnS "double shell" nanorods and their exploitation in cell labeling experiments. To synthesize such nanorods, first "dot-in-a-rod" CdSe(dot)/CdS(rod) core/shell nanocrystals were prepared. Then a ZnS shell was grown epitaxially over these CdSe/CdS nanorods, which led to a fluorescence quantum yield of the final core-shell-shell nanorods that could be as high as 75%. The quantum efficiency was correlated with the aspect ratio of the nanorods and with the thickness of the ZnS shell around the starting CdSe/CdS rods, which varied from 1 to 4 monolayers (as supported by a combination of X-ray diffraction, elemental analysis with inductively coupled plasma atomic emission spectroscopy and high resolution transmission electron microscopy analysis). Pump-probe and time-resolved photoluminescence measurements confirmed the reduction of trapping at CdS surface due to the presence of the ZnS shell, which resulted in more efficient photoluminescence. These double shell nanorods have potential applications as fluorescent biological labels, as we found that they are brighter in cell imaging as compared to the starting CdSe/CdS nanorods and to the CdSe/ZnS quantum dots, therefore a lower amount of material is required to label the cells. Concerning their cytotoxicity, according to the MTT assay, the double shell nanorods were less toxic than the starting core/shell nanorods and than the CdSe/ZnS quantum dots, although the latter still exhibited a lower intracellular toxicity than both nanorod samples.

  6. Bent Polytypic ZnSe and CdSe Nanowires Probed by Photoluminescence.

    PubMed

    Kim, Yejin; Im, Hyung Soon; Park, Kidong; Kim, Jundong; Ahn, Jae-Pyoung; Yoo, Seung Jo; Kim, Jin-Gyu; Park, Jeunghee

    2017-03-15

    Nanowires (NWs) have witnessed tremendous development over the past two decades owing to their varying potential applications. Semiconductor NWs often contain stacking faults due to the presence of coexisting phases, which frequently hampers their use. Herein, it is investigated how stacking faults affect the optical properties of bent ZnSe and CdSe NWs, which are synthesized using the vapor transport method. Polytypic zinc blende-wurtzite structures are produced for both these NWs by altering the growth conditions. The NWs are bent by the mechanical buckling of poly(dimethylsilioxane), and micro-photoluminescence (PL) spectra were then collected for individual NWs with various bending strains (0-2%). The PL measurements show peak broadening and red shifts of the near-band-edge emission as the bending strain increases, indicating that the bandgap decreases with increasing the bending strain. Remarkably, the bandgap decrease is more significant for the polytypic NWs than for the single phase NWs. This work provides insights into flexible electronic devices of 1D nanostructures by engineering the polytypic structures.

  7. One-step synthesis of boronic acid functionalized gold nanoclusters for photoluminescence sensing of dopamine

    NASA Astrophysics Data System (ADS)

    Chen, Huide; Liu, Chunxiu; Xia, Yunsheng

    2017-03-01

    This study is the first to report one-step synthesis of boronic acid functionalized gold nanoclusters (AuNCs) using mixed ligands of 4-mercaptophenylboronic acid (MPBA) and glutathione. Furthermore, the emission color of the products can be fancily tuned from green to near-infrared by simply changing the proportion of the two stabilizers. In basic media, dopamine (DA) molecules themselves polymerize each other and form polydopamine with large amounts of cis-diol groups, which then react with boronic acid groups on the AuNC’s surface based on the formation of boronate esters. As a result, the photoluminescence of the AuNCs is well quenched by the electron transfer effect. Accordingly, DA molecules are assayed from 0.5 to 9 μM, and the detection limit is as low as 0.1 μM. The as-prepared AuNCs exhibit high selectivity; the existing biomolecules including various amino acids, ascorbic acid, uric acid, glucose, etc, do not interfere with the assay. The proposed method is successfully applied to the assay of DA in human serum, indicating its practical potential.

  8. Kit for detecting nucleic acid sequences using competitive hybridization probes

    DOEpatents

    Lucas, Joe N.; Straume, Tore; Bogen, Kenneth T.

    2001-01-01

    A kit is provided for detecting a target nucleic acid sequence in a sample, the kit comprising: a first hybridization probe which includes a nucleic acid sequence that is sufficiently complementary to selectively hybridize to a first portion of the target sequence, the first hybridization probe including a first complexing agent for forming a binding pair with a second complexing agent; and a second hybridization probe which includes a nucleic acid sequence that is sufficiently complementary to selectively hybridize to a second portion of the target sequence to which the first hybridization probe does not selectively hybridize, the second hybridization probe including a detectable marker; a third hybridization probe which includes a nucleic acid sequence that is sufficiently complementary to selectively hybridize to a first portion of the target sequence, the third hybridization probe including the same detectable marker as the second hybridization probe; and a fourth hybridization probe which includes a nucleic acid sequence that is sufficiently complementary to selectively hybridize to a second portion of the target sequence to which the third hybridization probe does not selectively hybridize, the fourth hybridization probe including the first complexing agent for forming a binding pair with the second complexing agent; wherein the first and second hybridization probes are capable of simultaneously hybridizing to the target sequence and the third and fourth hybridization probes are capable of simultaneously hybridizing to the target sequence, the detectable marker is not present on the first or fourth hybridization probes and the first, second, third, and fourth hybridization probes each include a competitive nucleic acid sequence which is sufficiently complementary to a third portion of the target sequence that the competitive sequences of the first, second, third, and fourth hybridization probes compete with each other to hybridize to the third portion of the

  9. Photoluminescence probing of interface evolution with annealing in InGa(N)As/GaAs single quantum wells

    SciTech Connect

    Shao, Jun Qi, Zhen; Zhu, Liang; Chen, Xiren; Guo, Shaoling; Zhao, H.; Song, Yuxin; Zha, F.-X.; Wang, S. M.

    2015-10-28

    The effects of thermal annealing on the interfaces of InGa(N)As/GaAs single quantum wells (SQWs) are investigated by excitation-, temperature-, and magnetic field-dependent photoluminescence (PL). The annealing at 750 °C results in more significant blueshift and narrowing to the PL peak than that at 600 °C. Each of the PL spectra can be reproduced with two PL components: (i) the low-energy component (LE) keeps energetically unchanged, while the high-energy component (HE) moves up with excitation and shows at higher energy for the In{sub 0.375}Ga{sub 0.625}As/GaAs but crosses over with the LE at a medium excitation power for the In{sub 0.375}Ga{sub 0.625}N{sub 0.012}As{sub 0.988}/GaAs SQWs. The HE is broader than the corresponding LE, the annealing at 750 °C narrows the LE and HE and shrinks their energetic separation; (ii) the PL components are excitonic, and the InGaNAs shows slightly enhanced excitonic effects relative to the InGaAs SQW; (iii) no typical S-shape evolution of PL energy with temperature is detectable, and similar blueshift and narrowing are identified for the same annealing. The phenomena are mainly from the interfacial processes. Annealing improves the intralayer quality, enhances the interfacial In-Ga interdiffusion, and reduces the interfacial fluctuation. The interfacial interdiffusion does not change obviously by the small N content and hence similar PL-component narrowing and blueshift are observed for the SQWs after a nominally identical annealing. Comparison with previous studies is made and the PL measurements under different conditions are shown to be effective for probing the interfacial evolution in QWs.

  10. Zip nucleic acids are potent hydrolysis probes for quantitative PCR

    PubMed Central

    Paris, Clément; Moreau, Valérie; Deglane, Gaëlle; Voirin, Emilie; Erbacher, Patrick; Lenne-Samuel, Nathalie

    2010-01-01

    Zip nucleic acids (ZNAs) are oligonucleotides conjugated with cationic spermine units that increase affinity for their target. ZNAs were recently shown to enable specific and sensitive reactions when used as primers for polymerase chain reaction (PCR) and reverse-transcription. Here, we report their use as quantitative PCR hydrolysis probes. Ultraviolet duplex melting data demonstrate that attachment of cationic residues to the 3′ end of an oligonucleotide does not alter its ability to discriminate nucleotides nor the destabilization pattern relative to mismatch location in the oligonucleotide sequence. The stability increase provided by the cationic charges allows the use of short dual-labeled probes that significantly improve single-nucleotide polymorphism genotyping. Longer ZNA probes were shown to display reduced background fluorescence, therefore, generating greater sensitivity and signal level as compared to standard probes. ZNA probes thus provide broad flexibility in assay design and also represent an effective alternative to minor groove binder- and locked nucleic-acid-containing probes. PMID:20071749

  11. Tuning two-photon photoluminescence of gold nanoparticle aggregates with DNA and its application as turn-on photoluminescence probe for DNA sequence detection.

    PubMed

    Yuan, Peiyan; Ma, Rizhao; Guan, Zhenping; Gao, Nengyue; Xu, Qing-Hua

    2014-08-13

    Plasmon coupling between noble metal nanoparticles has been known to dramatically enhance linear and nonlinear optical properties of nearby chromophores and metal nanoparticles themselves. The interparticle distance is expected to have significant influence on the coupling strength. Here we have prepared DNA tuned Au nanoparticle assemblies with well controlled separation distances from 2.0 to 12.2 nm to investigate plasmon coupling strength and particle size effects on two-photon photoluminescence (TPPL) enhancement. TPPL intensities of these DNA coupled nanoassemblies were found to increase rapidly as the separation distance decreases. The largest TPPL enhancement factors of 115 and 265 were achieved at the shortest available separation distance of 2.0 nm for 21 and 41 nm Au NPs-dsDNA assemblies, respectively. We have further utilized DNA induced coupling of Au NPs and TPPL enhancement to develop a two-photon sensing scheme for detection of DNA sequences. This TPPL based method displayed high sensitivity with a limit of detection of 2.9 pM and excellent selectivity against ssDNA with mismatched bases. A single mismatch can be easily differentiated at room temperature. Taking the unique advantages of two-photon excitation, this method could be potentially further extended to DNA detection inside cells or even in vivo. These findings can provide important insight for fundamental understanding of plasmon-coupling enhanced TPPL and development of various two-photon excitation based applications.

  12. Defect-Induced Near-Infrared Photoluminescence of Single-Walled Carbon Nanotubes Treated with Polyunsaturated Fatty Acids.

    PubMed

    Chiu, Cheuk Fai; Saidi, Wissam A; Kagan, Valerian E; Star, Alexander

    2017-04-05

    Single-walled carbon nanotubes (SWCNTs) have been incorporated in many emerging applications in the biomedical field including chemical sensing, biological imaging, drug delivery, and photothermal therapy. To overcome inherent hydrophobicity and improve their biocompatibility, pristine SWCNTs are often coated with surfactants, polymers, DNA, proteins, or lipids. In this paper, we report the effect of polyunsaturated fatty acids (PUFAs) on SWCNT photoluminescence. A decrease in the SWCNT bandgap emission (E11) and a new red-shifted emission (E11(-)) were observed in the presence of PUFAs. We attribute the change in SWCNT photoluminescence to the formation of oxygen-containing defects by lipid hydroperoxides through photo-oxidation. The observed changes in near-infrared emission of SWCNTs are important for understanding the interaction between SWCNTs and lipid biocorona. Our results also indicate that photoexcited SWCNTs can catalyze lipid peroxidation similarly to lipoxygenases.

  13. Facile preparation of Gd3+ doped carbon quantum dots: Photoluminescence materials with magnetic resonance response as magnetic resonance/fluorescence bimodal probes

    NASA Astrophysics Data System (ADS)

    Ren, X. Y.; Yuan, X. X.; Wang, Y. P.; Liu, C. L.; Qin, Y.; Guo, L. P.; Liu, L. H.

    2016-07-01

    There are a few bimodal molecular imaging probes constructed by gadolinium (3+) ions in combination with carbon quantum dots (CQDs), and the reported ones show such obvious drawbacks as low luminous efficiency and weak MRI contrast. In the paper, a kind of CQDs photoluminescence materials with magnetic resonance response was prepared by hydrothermal method and employing gadopentetate monomeglumine (GdPM) as a precusor. Here, the GdPM plays a role of not only carbon source, but also gadolinium (3+) sources. When the GdPM aqueous solution with a concentration of 4 mg mL-1 was pyrolyzed under 220 °C and 2.0 MPa for 8 h, an optimal CQDs was obtained which are doped with gadolinium (3+) ions in both chelates and Gd2O3 (named as Gd3+-CQDs). The average diameter of the Gd3+-CQDs is about 1.6 nm, which show a high photoluminescence quantum yield of 7.1%, as well as high longitudinal relaxivity (r1) of 9.87 mM-1 s-1. And owing to the unconspicuous cell toxicity, the Gd3+-CQDs show big possibility for clinical application in magnetic resonance/fluorescence bimodal molecular imaging.

  14. Correlated high-resolution x-ray diffraction photoluminescence and atom probe tomography analysis of continuous and discontinuous InxGa1-xN quantum wells

    DOE PAGES

    Ren, Xiaochen; Riley, James R.; Koleske, Daniel; ...

    2015-07-14

    In this study, atom probe tomography (APT) is used to characterize the influence of hydrogen dosing duringGaN barrier growth on the indium distribution of InxGa1-xN quantum wells, and correlatedmicro-photoluminescence is used to measure changes in the emission spectrum and efficiency. We found that relative to the control growth, hydrogen dosing leads to a 50% increase in emission intensity arising from discontinuous quantum wells that are narrower, of lower indium content, and with more abrupt interfaces. Additionally, simulations of carrier distributions based on APT composition profiles indicate that the greater carrier confinement leads to an increased radiative recombination rate. Furthermore, APTmore » analysis of quantum well profiles enables refinement of x-ray diffractionanalysis for more accurate nondestructive measurements of composition.« less

  15. Designer nucleic acids to probe and program the cell.

    PubMed

    Krishnan, Yamuna; Bathe, Mark

    2012-12-01

    Recent advances in nucleic acid sequencing, structural, and computational technologies have resulted in dramatic progress in our understanding of nucleic acid structure and function in the cell. This knowledge, together with the predictable base-pairing of nucleic acids and powerful synthesis and expression capabilities now offers the unique ability to program nucleic acids to form precise 3D architectures with diverse applications in synthetic and cell biology. The unique modularity of structural motifs that include aptamers, DNAzymes, and ribozymes, together with their well-defined construction rules, enables the synthesis of functional higher-order nucleic acid complexes from these subcomponents. As we illustrate here, these highly programmable, smart complexes are increasingly enabling researchers to probe and program the cell in a sophisticated manner that moves well beyond the use of nucleic acids for conventional genetic manipulation alone.

  16. Non-redox modulated fluorescence strategy for sensitive and selective ascorbic acid detection with highly photoluminescent nitrogen-doped carbon nanoparticles via solid-state synthesis.

    PubMed

    Zhu, Xiaohua; Zhao, Tingbi; Nie, Zhou; Liu, Yang; Yao, Shouzhuo

    2015-08-18

    Highly photoluminescent nitrogen-doped carbon nanoparticles (N-CNPs) were prepared by a simple and green route employing sodium alginate as a carbon source and tryptophan as both a nitrogen source and a functional monomer. The as-synthesized N-CNPs exhibited excellent water solubility and biocompatibility with a fluorescence quantum yield of 47.9%. The fluorescence of the N-CNPs was intensively suppressed by the addition of ascorbic acid (AA). The mechanism of the fluorescence suppression of the N-CNPs was investigated, and the synergistic action of the inner filter effect (IFE) and the static quenching effect (SQE) contributed to the intensive fluorescence suppression, which was different from those reported for the traditional redox-based fluorescent probes. Owing to the spatial effect and hydrogen bond between the AA and the groups on the N-CNP surface, excellent sensitivity and selectivity for AA detecting was obtained in a wide linear relationship from 0.2 μM to 150 μM. The detection limit was as low as 50 nM (signal-to-noise ratio of 3). The proposed sensing systems also represented excellent sensitivity and selectivity for AA analysis in human biological fluids, providing a valuable platform for AA sensing in clinic diagnostic and drug screening.

  17. A carbon dot-based "off-on" fluorescent probe for highly selective and sensitive detection of phytic acid.

    PubMed

    Gao, Zhao; Wang, Libing; Su, Rongxin; Huang, Renliang; Qi, Wei; He, Zhimin

    2015-08-15

    We herein report a facile, one-step pyrolysis synthesis of photoluminescent carbon dots (CDs) using citric acid as the carbon source and lysine as the surface passivation reagent. The as-prepared CDs show narrow size distribution, excellent blue fluorescence and good photo-stability and water dispersivity. The fluorescence of the CDs was found to be effectively quenched by ferric (Fe(III)) ions with high selectivity via a photo-induced electron transfer (PET) process. Upon addition of phytic acid (PA) to the CDs/Fe(III) complex dispersion, the fluorescence of the CDs was significantly recovered, arising from the release of Fe(III) ions from the CDs/Fe(III) complex because PA has a higher affinity for Fe(III) ions compared to CDs. Furthermore, we developed an "off-on" fluorescence assay method for the detection of phytic acid using CDs/Fe(III) as a fluorescent probe. This probe enables the selective detection of PA with a linear range of 0.68-18.69 μM and a limit of detection (signal-to-noise ratio is 3) of 0.36 μM. The assay method demonstrates high selectivity, repeatability, stability and recovery ratio in the detection of the standard and real PA samples. We believe that the facile operation, low-cost, high sensitivity and selectivity render this CD-based "off-on" fluorescent probe an ideal sensing platform for the detection of PA.

  18. Composition-dependent trap distributions in CdSe and InP quantum dots probed using photoluminescence blinking dynamics.

    PubMed

    Chung, Heejae; Cho, Kyung-Sang; Koh, Weon-Kyu; Kim, Dongho; Kim, Jiwon

    2016-07-21

    Although Group II-VI quantum dots (QDs) have attracted much attention due to their wide range of applications in QD-based devices, the presence of toxic ions in II-VI QDs raises environmental concerns. To fulfill the demands of nontoxic QDs, synthetic routes for III-V QDs have been developed. However, only a few comparative analyses on optical properties of III-V QDs have been performed. In this study, the composition-related energetic trap distributions have been explored by using three different types of core/multishell QDs: CdSe-CdS (CdSe/CdS/ZnS), InP-ZnSe (InP/ZnSe/ZnS), and InP-GaP (InP/GaP/ZnS). It was shown that CdSe-CdS QDs have much larger trap densities than InP-shell QDs at higher energy states (at least 1Eg (band gap energy) above the lowest conduction band edge) based on probability density plots and Auger ionization efficiencies which are determined by analyses of photoluminescence blinking dynamics. This result suggests that the composition of encapsulated QDs is closely associated with the charge trapping processes, and also provides an insight into the development of more environmentally friendly QD-based devices.

  19. Composition-dependent trap distributions in CdSe and InP quantum dots probed using photoluminescence blinking dynamics

    NASA Astrophysics Data System (ADS)

    Chung, Heejae; Cho, Kyung-Sang; Koh, Weon-Kyu; Kim, Dongho; Kim, Jiwon

    2016-07-01

    Although Group II-VI quantum dots (QDs) have attracted much attention due to their wide range of applications in QD-based devices, the presence of toxic ions in II-VI QDs raises environmental concerns. To fulfill the demands of nontoxic QDs, synthetic routes for III-V QDs have been developed. However, only a few comparative analyses on optical properties of III-V QDs have been performed. In this study, the composition-related energetic trap distributions have been explored by using three different types of core/multishell QDs: CdSe-CdS (CdSe/CdS/ZnS), InP-ZnSe (InP/ZnSe/ZnS), and InP-GaP (InP/GaP/ZnS). It was shown that CdSe-CdS QDs have much larger trap densities than InP-shell QDs at higher energy states (at least 1Eg (band gap energy) above the lowest conduction band edge) based on probability density plots and Auger ionization efficiencies which are determined by analyses of photoluminescence blinking dynamics. This result suggests that the composition of encapsulated QDs is closely associated with the charge trapping processes, and also provides an insight into the development of more environmentally friendly QD-based devices.Although Group II-VI quantum dots (QDs) have attracted much attention due to their wide range of applications in QD-based devices, the presence of toxic ions in II-VI QDs raises environmental concerns. To fulfill the demands of nontoxic QDs, synthetic routes for III-V QDs have been developed. However, only a few comparative analyses on optical properties of III-V QDs have been performed. In this study, the composition-related energetic trap distributions have been explored by using three different types of core/multishell QDs: CdSe-CdS (CdSe/CdS/ZnS), InP-ZnSe (InP/ZnSe/ZnS), and InP-GaP (InP/GaP/ZnS). It was shown that CdSe-CdS QDs have much larger trap densities than InP-shell QDs at higher energy states (at least 1Eg (band gap energy) above the lowest conduction band edge) based on probability density plots and Auger ionization

  20. Ascertaining free histidine from mixtures with histidine-containing proteins using time-resolved photoluminescence spectroscopy.

    PubMed

    Huang, Kewei; Jiang, Chengmin; Martí, Angel A

    2014-11-13

    The use of photoluminescent probes for differentiating free amino acids from biomolecules containing the same amino acids is challenging. Photoluminescent probes generally present similar emission spectra when in the presence of either free-amino acids or protein containing those same amino acids. Probes based on cyclometalated iridium(III) complexes Ir(L)2(sol)2 (where L is 2-phenylpyridine, 2-(2,4-difluorophenyl)pyridine, or benzo[h]quinolone, and sol is a solvent molecule) present long-lived emission when bound to histidine. This emission is tuned by the microenvironment around the complex and therefore its lifetime is different for free histidine (487 ns) than from histidine-containing proteins such as bovine serum albumin (average lifetime > 700 ns). As a proof-of-concept we demonstrate that free histidine can be discerned from a mixture with histidine-containing proteins by using time-resolved photoluminescence decays. In the presence of multiple sources of histidine, iridium(III) probes display a multiexponential decay, which can be fitted by nonlinear least-squares methods to separate the different components. Because the pre-exponential factor of the 487 ns lifetime is proportional to the concentration of free histidine, we can use it to assess the amount of free histidine in solution even in the presence of proteins such as bovine serum albumin. We also show that iridium(III) probes displaying different photoluminescence maxima can be produced by modifying the ancillary ligands of the metal complex.

  1. Evolution of the electron localization in a nonconventional alloy system GaAs1-xNx probed by high-magnetic-field photoluminescence

    NASA Astrophysics Data System (ADS)

    Wang, Y. J.; Wei, X.; Zhang, Y.; Mascarenhas, A.; Xin, H. P.; Hong, Y. G.; Tu, C. W.

    2003-06-01

    We demonstrate that a high magnetic field can be used effectively not only to probe the nature of the photoluminescence (PL) in a semiconductor, but also to reveal emission peaks that are unobservable at zero field since the magnetic field can alter energy relaxation processes and the statistical distribution of the photocarriers. Our systematic magneto-PL study of GaAs1-xNx (0.1%⩽x<2.5%) in fields up to 30 T indicates that the character of the low-temperature PL in this system changes drastically with varying nitrogen composition x and exhibits transitions with applying strong magnetic fields. For x<0.7%, the PL spectrum shows many discrete features whose energies remain nearly stationary up to the highest applied field. However, the magnetic confinement gives rise to a feature emerging on the higher energy side of the zero-field spectrum. This feature does show a diamagnetic shift, but it is much slower that that of the GaAs band-edge transition. For x>1%, the PL spectrum evolves into a broad band, and its diamagnetic shift resembles the band-edge transition in a conventional semiconductor, and the rate of shift is comparable to that of GaAs. From the diamagnetic shift of the band, the reduced effective masses for different composition of nitrogen have been derived for this system using the standard theory for the magneto-exciton in a three dimensional semiconductor.

  2. Syntheses, structures, photoluminescence and photocatalysis of 2D layered lanthanide-carboxylates with 2, 2‧-dithiodibenzoic acid

    NASA Astrophysics Data System (ADS)

    Ding, Ling; Zhong, Jie-Cen; Qiu, Xing-Tai; Sun, Yan-Qiong; Chen, Yi-Ping

    2017-02-01

    Two series of lanthanide-carboxylates, [Ln(2,2‧-dtba)(2,2‧-Hdtba)(EtOH)]n (I:Ln=Eu(1a), Dy(1b)) and [Ln(2,2‧-dtba)(2,2‧-Hdtba)(4,4‧-bpy)0.5]n (II:Ln=Eu(2a), Dy(2b), Tb(2c) 2,2‧-H2dtba=2,2‧-dithiodibenzoic acid, 4,4‧-bpy=4,4‧-bipyridine) have been synthesized under hydrothermal conditions. Interestingly, the H2dtba organic ligand was generated by in situ S-S reaction of 2-mercaptobenzoic acid. Compounds I and II possess different 2D layered structures based on similar 1D [Ln(2,2‧-dtba)]+ chains. Photoluminescence studies reveal that compounds I and II exhibit strong lanthanide characteristic emission bands. Remarkably, Compounds 1b and 2a both exhibit good photocatalytic activity for degradation of Rhodamine-B (Rh-B) under the simulated sunlight irradiation.

  3. Temperature dependence of the energy bandgap of two-dimensional hexagonal boron nitride probed by excitonic photoluminescence

    SciTech Connect

    Du, X. Z.; Lin, J. Y.; Jiang, H. X.; Frye, C. D.; Edgar, J. H.

    2014-02-07

    Hexagonal boron nitride (hBN) is an emerging material for the exploration of new physics in two-dimensional (2D) systems that are complementary to graphene. Nanotubes with a diameter (∼60 nm) that is much larger than the exciton binding energy in hBN have been synthesized and utilized to probe the fundamental optical transitions and the temperature dependence of the energy bandgap of the corresponding 2D hBN sheets. An excitonic transition at 5.901 eV and its longitudinal optical phonon replica at 5.735 eV were observed. The excitonic emission line is blue shifted by about 130 meV with respect to that in hBN bulk crystals due to the effects of reduced dimensionality. The temperature evolution of the excitonic emission line measured from 300 to 800 K revealed that the temperature coefficient of the energy bandgap of hBN nanotubes with large diameters (or equivalently hBN sheets) is about 0.43 meV/{sup 0}K, which is a factor of about 5 times smaller than the theoretically predicted value for the transitions between the π and π* bands in hBN bulk crystals and 6 times smaller than the measured value in AlN epilayers with a comparable energy bandgap. The observed weaker temperature dependence of the bandgap than those in 3D hBN and AlN is a consequence of the effects of reduced dimensionality in layer-structured hBN.

  4. Temperature dependence of the energy bandgap of two-dimensional hexagonal boron nitride probed by excitonic photoluminescence

    NASA Astrophysics Data System (ADS)

    Du, X. Z.; Frye, C. D.; Edgar, J. H.; Lin, J. Y.; Jiang, H. X.

    2014-02-01

    Hexagonal boron nitride (hBN) is an emerging material for the exploration of new physics in two-dimensional (2D) systems that are complementary to graphene. Nanotubes with a diameter (˜60 nm) that is much larger than the exciton binding energy in hBN have been synthesized and utilized to probe the fundamental optical transitions and the temperature dependence of the energy bandgap of the corresponding 2D hBN sheets. An excitonic transition at 5.901 eV and its longitudinal optical phonon replica at 5.735 eV were observed. The excitonic emission line is blue shifted by about 130 meV with respect to that in hBN bulk crystals due to the effects of reduced dimensionality. The temperature evolution of the excitonic emission line measured from 300 to 800 K revealed that the temperature coefficient of the energy bandgap of hBN nanotubes with large diameters (or equivalently hBN sheets) is about 0.43 meV/0K, which is a factor of about 5 times smaller than the theoretically predicted value for the transitions between the π and π* bands in hBN bulk crystals and 6 times smaller than the measured value in AlN epilayers with a comparable energy bandgap. The observed weaker temperature dependence of the bandgap than those in 3D hBN and AlN is a consequence of the effects of reduced dimensionality in layer-structured hBN.

  5. Computer selection of oligonucleotide probes from amino acid sequences for use in gene library screening.

    PubMed

    Yang, J H; Ye, J H; Wallace, D C

    1984-01-11

    We present a computer program, FINPROBE, which utilizes known amino acid sequence data to deduce minimum redundancy oligonucleotide probes for use in screening cDNA or genomic libraries or in primer extension. The user enters the amino acid sequence of interest, the desired probe length, the number of probes sought, and the constraints on oligonucleotide synthesis. The computer generates a table of possible probes listed in increasing order of redundancy and provides the location of each probe in the protein and mRNA coding sequence. Activation of a next function provides the amino acid and mRNA sequences of each probe of interest as well as the complementary sequence and the minimum dissociation temperature of the probe. A final routine prints out the amino acid sequence of the protein in parallel with the mRNA sequence listing all possible codons for each amino acid.

  6. Synthesis and characterization of polymorphs of photoluminescent Eu(III)-(2,5-furandicarboxylic acid, oxalic acid) MOFs

    NASA Astrophysics Data System (ADS)

    Shi, Fa-Nian; Ananias, Duarte; Yang, Ting-Hai; Rocha, João

    2013-08-01

    A novel metal organic framework (MOF) formulated as [Eu(H2O)2(fdc)(ox)0.5·(H2O)]n (1, fdc2-=2,5-furandicarboxylate, ox2-=oxalate), was hydrothermally synthesized via in situ ox2- generation from the partial decomposition of the fdc2- ligand. This material crystallizes in the monoclinic space group C2/c, unit cell parameters of 1: a=16.7570(10), b=10.5708(7), c=13.5348(14) Å, β=116.917(2)° (Z=8), and exhibits a three-dimensional (3D)-porous framework, with guest water molecules residing in the channel linking all other ligands (H2O, ox2-and fdc2-) via hydrogen bonding interactions. Compound 2 is a polymorph of 1 crystallizing in monoclinic P21/c space group. The photoluminescence properties of 1 and 2 were studied at room temperature. The spectra show the typical Eu3+ red emission and the differences observed reflects the slightly different structures of these polymorphs.

  7. Anodic luminescence, structural, photoluminescent, and photocatalytic properties of anodic oxide films grown on niobium in phosphoric acid

    NASA Astrophysics Data System (ADS)

    Stojadinović, Stevan; Tadić, Nenad; Radić, Nenad; Stefanov, Plamen; Grbić, Boško; Vasilić, Rastko

    2015-11-01

    This article reports on properties of oxide films obtained by anodization of niobium in phosphoric acid before and after the dielectric breakdown. Weak anodic luminescence of barrier oxide films formed during the anodization of niobium is correlated to the existence of morphological defects in the oxide layer. Small sized sparks generated by dielectric breakdown of formed oxide film cause rapid increase of luminescence intensity. The luminescence spectrum of obtained films on niobium under spark discharging is composed of continuum radiation and spectral lines caused by electronic spark discharging transitions in oxygen and hydrogen atoms. Oxide films formed before the breakdown are amorphous, while after the breakdown oxide films are partly crystalline and mainly composed of Nb2O5 hexagonal phase. The photocatalytic activity of obtained oxide films after the breakdown was investigated by monitoring the degradation of methyl orange. Increase of the photocatalytic activity with time is related to an increase of oxygen vacancy defects in oxide films formed during the process. Also, higher concentration of oxygen vacancy defects in oxide films results in higher photoluminescence intensity.

  8. Rapid analysis of barley straw before and after dilute sulfuric acid pretreatment by photoluminescence.

    PubMed

    Kim, Sung Bong; Cui, Chunzhi; Lee, Ja Hyun; Lee, Sang Jun; Ahn, Dong June; Park, Chulhwan; Kim, Jun Seok; Kim, Seung Wook

    2013-10-01

    The fluorescence intensities (FIs) of raw and pretreated barley straws were measured by fluorescence microscopy, and the difference in the fluorescence intensity of barley straw before and after dilute acid pretreatment was analyzed by investigation of the major compounds of barley straw. The difference in fluorescence intensity was due to the difference in xylan content. Barley straw was pretreated using dilute sulfuric acid at various conditions and the correlation between the fluorescence intensity and glucose yield of barley straw was investigated. The coefficient of determination (R(2)) of the correlation was found to be 72.28%. Also the calibration of fluorescence intensity with the xylan content was performed. In addition, the absorption and emission spectra of the raw and the pretreated barley straw were examined to verify the proposed method. The absorption and emission wave lengths were 550 nm and 665 nm, respectively.

  9. Effect of doping of calcium fluoride nanoparticles on the photoluminescence properties of europium complexes with benzoic acid derivatives as secondary ligands and 2-aminopyridine as primary ligand

    NASA Astrophysics Data System (ADS)

    Sharma, Garima; Narula, Anudeep Kumar

    2015-08-01

    The present article reports the synthesis of three Eu(III) complexes [Eu(BA)3(2-ap)] (1), [Eu(HBA)3(2-ap)] (2) and [Eu(ABA)3(2-ap)] (3) (BA = benzoic acid, HBA = 2-hydroxy benzoic acid, ABA = 2-amino benzoic acid and 2-ap = 2-aminopyridine) carried out in ethanol solution. The complexes were further doped with CaF2 nanoparticles and a change in the photoluminescence properties was observed. The compositions and structural investigation of the complexes were determined by elemental analysis and Fourier transform infrared spectroscopy (FTIR) which suggest the coordination of ligands with the central Eu(III) ion. The optical properties of the complexes were studied by Ultraviolet Visible absorption spectroscopy (UV-Vis) and photoluminescence studies (PL). The relative PL intensity was enhanced in the Eu(III) complexes doped with CaF2 nanoparticles as compared to the pure Eu(III) complexes, however the increase in intensity varied in the order of ligands ABA > HBA > BA. The photoluminescence lifetime decay curves also revealed the longer lifetime (τ) and higher quantum efficiency (η) for europium complexes with ABA ligands suggesting the efficient energy transfer and better sensitizing ability of the ligand to europium ion. The morphology of the synthesized compounds were studied by Scanning Electron Microscopy (SEM) revealing spherical morphology with agglomeration of the nanoparticles.

  10. Method for producing labeled single-stranded nucleic acid probes

    DOEpatents

    Dunn, John J.; Quesada, Mark A.; Randesi, Matthew

    1999-10-19

    Disclosed is a method for the introduction of unidirectional deletions in a cloned DNA segment. More specifically, the method comprises providing a recombinant DNA construct comprising a DNA segment of interest inserted in a cloning vector, the cloning vector having an f1 endonuclease recognition sequence adjacent to the insertion site of the DNA segment of interest. The recombinant DNA construct is then contacted with the protein pII encoded by gene II of phage f1 thereby generating a single-stranded nick. The nicked DNA is then contacted with E. coli Exonuclease III thereby expanding the single-stranded nick into a single-stranded gap. The single-stranded gapped DNA is then contacted with a single-strand-specific endonuclease thereby producing a linearized DNA molecule containing a double-stranded deletion corresponding in size to the single-stranded gap. The DNA treated in this manner is then incubated with DNA ligase under conditions appropriate for ligation. Also disclosed is a method for producing single-stranded DNA probes. In this embodiment, single-stranded gapped DNA, produced as described above, is contacted with a DNA polymerase in the presence of labeled nucleotides to fill in the gap. This DNA is then linearized by digestion with a restriction enzyme which cuts outside the DNA segment of interest. The product of this digestion is then denatured to produce a labeled single-stranded nucleic acid probe.

  11. Visible photoluminescence from nearly monodispersed Au 12 clusters protected by meso-2,3-dimercaptosuccinic acid

    NASA Astrophysics Data System (ADS)

    Negishi, Yuichi; Tsukuda, Tatsuya

    2004-01-01

    Nearly monodispersed Au 12 clusters protected by monolayers of meso-2,3-dimercaptosuccinic acid (DMSA) exhibited luminescence at 630 nm with a quantum yield of 1 × 10 -6 upon the photoexcitation at 395 nm to the lowest electronic excited state. The visible PL is assigned to phosphorescence originating from a triplet-like excited state based on the large Stokes shift (1.2 eV). The PL quantum yield was enhanced up to ≈0.9%, greater by eight orders of magnitude than that of bulk gold, by thickening the protecting layer and freezing a solvent at 77 K. The emission peak energy is discussed within the context of core-size dependent electronic structures by comparison with those of thiolate-protected gold clusters reported in the literature.

  12. Probing the Specificity Determinants of Amino Acid Recognition by Arginase

    SciTech Connect

    Shishova, E.; Di Costanzo, L; Emig, F; Ash, D; Christianson, D

    2009-01-01

    Arginase is a binuclear manganese metalloenzyme that serves as a therapeutic target for the treatment of asthma, erectile dysfunction, and atherosclerosis. In order to better understand the molecular basis of inhibitor affinity, we have employed site-directed mutagenesis, enzyme kinetics, and X-ray crystallography to probe the molecular recognition of the amino acid moiety (i.e., the ?-amino and ?-carboxylate groups) of substrate l-arginine and inhibitors in the active site of arginase I. Specifically, we focus on (1) a water-mediated hydrogen bond between the substrate ?-carboxylate and T135, (2) a direct hydrogen bond between the substrate ?-carboxylate and N130, and (3) a direct charged hydrogen bond between the substrate ?-amino group and D183. Amino acid substitutions for T135, N130, and D183 generally compromise substrate affinity as reflected by increased KM values but have less pronounced effects on catalytic function as reflected by minimal variations of kcat. As with substrate KM values, inhibitor Kd values increase for binding to enzyme mutants and suggest that the relative contribution of intermolecular interactions to amino acid affinity in the arginase active site is water-mediated hydrogen bond < direct hydrogen bond < direct charged hydrogen bond. Structural comparisons of arginase with the related binuclear manganese metalloenzymes agmatinase and proclavaminic acid amidinohydrolase suggest that the evolution of substrate recognition in the arginase fold occurs by mutation of residues contained in specificity loops flanking the mouth of the active site (especially loops 4 and 5), thereby allowing diverse guanidinium substrates to be accommodated for catalysis.

  13. Method for analyzing nucleic acids by means of a substrate having a microchannel structure containing immobilized nucleic acid probes

    DOEpatents

    Ramsey, J. Michael; Foote, Robert S.

    2002-01-01

    A method and apparatus for analyzing nucleic acids includes immobilizing nucleic probes at specific sites within a microchannel structure and moving target nucleic acids into proximity to the probes in order to allow hybridization and fluorescence detection of specific target sequences.

  14. Method for analyzing nucleic acids by means of a substrate having a microchannel structure containing immobilized nucleic acid probes

    DOEpatents

    Ramsey, J. Michael; Foote, Robert S.

    2003-12-09

    A method and apparatus for analyzing nucleic acids includes immobilizing nucleic probes at specific sites within a microchannel structure and moving target nucleic acids into proximity to the probes in order to allow hybridization and fluorescence detection of specific target sequences.

  15. Photoluminescence: A probe for short, medium and long-range self-organization order in ZrTiO{sub 4} oxide

    SciTech Connect

    Lucena, Poty R. de . E-mail: poty@liec.ufscar.br; Roberto Leite, Edson; Pontes, Fenelon M.; Longo, Elson; Pizani, Paulo S.; Arana Varela, Jose

    2006-12-15

    Photoluminescent disordered ZrTiO{sub 4} powders were obtained by the polymeric precursor soft-chemical method. This oxide system (ordered and disordered) was characterized by photoluminescence, Raman spectroscopy, X-ray diffraction, differential scanning calorimetry and UV-vis absorption experiments. The UV absorption tail formation in the disordered oxides was related to the diminution of optical band gap. In the disordered phase, this oxide displayed broad band photoluminescence caused by change in coordination number of titanium and zirconium with oxygen atoms. The gap decreased from 3.09eV in crystalline oxide to 2.16 eV in disordered oxide. The crystalline oxide presented an orthorhombic {alpha}-PbO{sub 2}-type structure in which Zr{sup 4+} and Ti{sup 4+} were randomly distributed in octahedral coordination polyhedra with oxygen atoms. The amorphous-crystalline transition occurred at almost 700 deg. C, at which point the photoluminescence vanished. The Raman peak at close to 80-200cm{sup -1} indicated the presence of locally ordered Ti-O{sub n} and Zr-O{sub n} polyhedra in disordered photoluminescent oxides.

  16. Method for replicating an array of nucleic acid probes

    DOEpatents

    Cantor, C.R.; Przetakiewicz, M.; Smith, C.L.; Sano, T.

    1998-08-18

    The invention relates to the replication of probe arrays and methods for replicating arrays of probes which are useful for the large scale manufacture of diagnostic aids used to screen biological samples for specific target sequences. Arrays created using PCR technology may comprise probes with 5{prime}- and/or 3{prime}-overhangs. 16 figs.

  17. Method for replicating an array of nucleic acid probes

    DOEpatents

    Cantor, Charles R.; Przetakiewicz, Marek; Smith, Cassandra L.; Sano, Takeshi

    1998-01-01

    The invention relates to the replication of probe arrays and methods for replicating arrays of probes which are useful for the large scale manufacture of diagnostic aids used to screen biological samples for specific target sequences. Arrays created using PCR technology may comprise probes with 5'- and/or 3'-overhangs.

  18. Sensitive determination of nucleic acids using organic nanoparticle fluorescence probes

    NASA Astrophysics Data System (ADS)

    Zhou, Yunyou; Bian, Guirong; Wang, Leyu; Dong, Ling; Wang, Lun; Kan, Jian

    2005-06-01

    This paper describes the preparation of organic nanoparticles by reprecipitation method under sonication and vigorous stirring. Transmission electron microscopy (TEM) was used to characterize the size and size distribution of the luminescent nanoparticles. Their average diameter was about 25 nm with a size variation of ±18%. The fluorescence decay lifetime of the nanoparticles also was determined on a self-equipped fluorospectrometer with laser light source. The lifetime (˜0.09 μs) of nanoparticles is about three times long as that of the monomer. The nanoparticles were in abundant of hydrophilic groups, which increased their miscibility in aqueous solution. These organic nanoparticles have high photochemical stability, excellent resistance to chemical degradation and photodegradation, and a good fluorescence quantum yield (25%). The fluorescence can be efficiently quenched by nucleic acids. Based on the fluorescence quenching of nanoparticles, a fluorescence quenching method was developed for determination of microamounts of nucleic acids by using the nanoparticles as a new fluorescent probe. Under optimal conditions, maximum fluorescence quenching is produced, with maximum excitation and emission wavelengths of 345 and 402 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range 0.4-19.0 μg ml -1 for calf thymus DNA (ct-DNA) and 0.3-19.0 μg ml -1 for fish sperm DNA (fs-DNA). The corresponding detection limits are 0.25 μg ml -1 for ct-DNA and 0.17 μg ml -1 for fs-DNA. The relative standard deviation of six replicate measurements is 1.3-2.1%. The method is simple, rapid and sensitive with wide linear range. The recovery and relative standard deviation are very satisfactory.

  19. Organic acids and protein compounds causing the photoluminescence properties of natural rubber membranes and the quenching phenomena from Au nanoparticle incorporation.

    PubMed

    Cabrera, Flávio C; Agostini, Deuber L S; Dos Santos, Renivaldo J; Guimarães, Francisco E G; Guerrero, Ariel R; Aroca, Ricardo F; Job, Aldo E

    2014-12-01

    Natural rubber membranes were fabricated using latex from Hevea brasiliensis trees (clone RRIM 600) by casting, and controlling the time and temperature of thermal treatment. Three temperatures were used: 65, 80 and 120 °C and the corresponding annealing times of 6, 8, 10 and 12 h. The centrifugation of the latex produces the constituent phases: solid rubber (F1), serum or protein components (F2) and bottom fraction (F3). The photoluminescence properties could be correlated with organic acid components of latex. Natural rubber membranes were used as the active substrate (reducing agent) for the incorporation of colloidal Au nanoparticles synthesized by in situ reduction at different times. The intensity of photoluminescence bands assigned to the natural rubber decreases with the increase in amount of nanoparticles present on the membrane surface. It can be assumed that Au nanoparticles may be formed by reduction of the Au cation reacting with functional groups that are directly related to photoluminescence properties. However, the quenching of fluorescence may be attributed to the formation of a large amount of metal nanostructures on the natural rubber surface.

  20. Impurity-trapped excitons and electron traps in CaF2:Yb2+ and SrF2:Yb2+ probed by transient photoluminescence enhancement

    NASA Astrophysics Data System (ADS)

    Senanayake, P. S.; Wells, J. P. R.; Reid, M. F.; Berden, G.; Meijerink, A.; Reeves, R. J.

    2013-01-01

    CaF$_2$:Yb$^{2+}$ and SrF$_2$:Yb$^{2+}$ crystals have been investigated by a two-color UV + IR transient photoluminescence enhancement technique. The enhancement gives information about both changes in internal energy levels of the excitons and liberation of electrons from traps in the crystals.

  1. A Nucleic Acid Probe and Method for the Detection of Shigella and Enteroinvasive E. coli Bacteria.

    DTIC Science & Technology

    This invention relates to nucleic acid probes and a method for the rapid detection of Shigella and enteroinvasive Escherichia coli, the causative agents of bacterial dysentery, by use of a nucleic acid hybridization probe, equivalent to a plasmid DNA region encoding one of 4 specific invasion-associated, peptides of all strains of Shigella and enterinvasive E . coli , in a nucleic acid hybridization reaction with a clinical specimen containing dysentery bacteria.

  2. Revealing Nucleic Acid Mutations Using Förster Resonance Energy Transfer-Based Probes

    PubMed Central

    Junager, Nina P. L.; Kongsted, Jacob; Astakhova, Kira

    2016-01-01

    Nucleic acid mutations are of tremendous importance in modern clinical work, biotechnology and in fundamental studies of nucleic acids. Therefore, rapid, cost-effective and reliable detection of mutations is an object of extensive research. Today, Förster resonance energy transfer (FRET) probes are among the most often used tools for the detection of nucleic acids and in particular, for the detection of mutations. However, multiple parameters must be taken into account in order to create efficient FRET probes that are sensitive to nucleic acid mutations. In this review; we focus on the design principles for such probes and available computational methods that allow for their rational design. Applications of advanced, rationally designed FRET probes range from new insights into cellular heterogeneity to gaining new knowledge of nucleic acid structures directly in living cells. PMID:27472344

  3. Metal–organic hybrid materials built with tetrachlorophthalate acid and different N-donor coligands: Structure diversity and photoluminescence

    SciTech Connect

    Xiao, Zhenyu; Yang, Xiao; Zhao, Siwei; Wang, Debao Yang, Yu; Wang, Lei

    2016-02-15

    Eight new metal–organic hybrid materials, namely {Cd(Tcph)(4,4′-bipy)_1_/_2} (1), {[Cd_2(Tcph)_2(1,4-bimb)_1_/_2(H_2O)_4]·H_2O} (2), {Cd_2(Tcph)_2(1,4-bmimb)_1_/_2(H_2O)_4} (3), {Cd(Tcph)(1,2-bmimb)} (4), {Cu(Tcph)(1,4-bimb)(H_2O)} (5), {[Co(Tcph)(1,4-bimb)_1_/_2(H_2O)_3]·(H_2O)} (6), {Zn(Tcph)(1,2-bimb)} (7), {Cu_2(Tcph)_2(1,2-bimb)(H_2O)_4} (8), where Tcph=tetrachlorophthalate acid, 4,4′-bipy=4,4′-bipyridine, 1,4-bimb=1,4-bis(imidazol-1-ylmethyl)benzene, 1,4-bmimb=1,4-bis(2-methylimidazol-1-ylmethyl)benzene, 1,2-bimb=1,2-bis(imidazol-1-ylmethyl)-benzene, 1,2-bmimb=1,2-bis(2-methylimidazol-1-ylmethyl)benzene, have been synthesized and characterized. Their structures are determined by single crystal X-ray diffraction and further characterized by infrared spectra (IR) and thermogravimetric (TG) analyses. Complex 1, 4 and 7 display 2D layer structures. 1 possesses two-dimensional sheet containing an unusual [Cd(Tcph)] chains linked by 4,4′-bipy co-ligand, while 4 and 7 hold the similar 4-connected 4{sup 4}-sql nets. Complex 2 and 3 feature a similar three dimensional (3D) internal compensation structure with a topology of {4"2·6"3·8}{sub 2}{6"3}. 5 is a novel 2-fold self-penetrating 3D network with 4-coordinated 6{sup 5}·8–CdSO{sub 4} subnets. The ladder-like chains of 6 are further connected through O–H···O interactions to yield a 3D supramolecular structure. 8 is a discrete tetranuclear complex. The thermal stabilities of 1–8 and the luminescent properties of 1–4 and 7 in the solid state are also discussed. - Graphical abstract: Structure diversity and photoluminescence of eight new metal–organic hybrid materials constructed by Tetrachlorophthalate acid and different N-donor coligands are discussed in the context. - Highlights: • Eight new coordination polymers were synthesized based on mix-ligand strategy. • Complex 2 and 3 feature a similar 3D structure with {4"2·6"3·8}{sub 2}{6"3} topology. • Seven coordination modes of

  4. Detection and isolation of nucleic acid sequences using competitive hybridization probes

    DOEpatents

    Lucas, J.N.; Straume, T.; Bogen, K.T.

    1997-04-01

    A method for detecting a target nucleic acid sequence in a sample is provided using hybridization probes which competitively hybridize to a target nucleic acid. According to the method, a target nucleic acid sequence is hybridized to first and second hybridization probes which are complementary to overlapping portions of the target nucleic acid sequence, the first hybridization probe including a first complexing agent capable of forming a binding pair with a second complexing agent and the second hybridization probe including a detectable marker. The first complexing agent attached to the first hybridization probe is contacted with a second complexing agent, the second complexing agent being attached to a solid support such that when the first and second complexing agents are attached, target nucleic acid sequences hybridized to the first hybridization probe become immobilized on to the solid support. The immobilized target nucleic acids are then separated and detected by detecting the detectable marker attached to the second hybridization probe. A kit for performing the method is also provided. 7 figs.

  5. Detection and isolation of nucleic acid sequences using competitive hybridization probes

    DOEpatents

    Lucas, Joe N.; Straume, Tore; Bogen, Kenneth T.

    1997-01-01

    A method for detecting a target nucleic acid sequence in a sample is provided using hybridization probes which competitively hybridize to a target nucleic acid. According to the method, a target nucleic acid sequence is hybridized to first and second hybridization probes which are complementary to overlapping portions of the target nucleic acid sequence, the first hybridization probe including a first complexing agent capable of forming a binding pair with a second complexing agent and the second hybridization probe including a detectable marker. The first complexing agent attached to the first hybridization probe is contacted with a second complexing agent, the second complexing agent being attached to a solid support such that when the first and second complexing agents are attached, target nucleic acid sequences hybridized to the first hybridization probe become immobilized on to the solid support. The immobilized target nucleic acids are then separated and detected by detecting the detectable marker attached to the second hybridization probe. A kit for performing the method is also provided.

  6. Large scale synthesis of graphene quantum dots (GQDs) from waste biomass and their use as an efficient and selective photoluminescence on-off-on probe for Ag(+) ions.

    PubMed

    Suryawanshi, Anil; Biswal, Mandakini; Mhamane, Dattakumar; Gokhale, Rohan; Patil, Shankar; Guin, Debanjan; Ogale, Satishchandra

    2014-10-21

    Graphene quantum dots (GQDs) are synthesized from bio-waste and are further modified to produce amine-terminated GQDs (Am-GQDs) which have higher dispersibility and photoluminescence intensity than those of GQDs. A strong fluorescence quenching of Am-GQDs (switch-off) is observed for a number of metal ions, but only for the Ag(+) ions is the original fluorescence regenerated (switch-on) upon addition of L-cysteine.

  7. Fluorescence probe for the convenient and sensitive detection of ascorbic acid

    PubMed Central

    Matsuoka, Yuta; Yamato, Mayumi; Yamada, Ken-ichi

    2016-01-01

    Ascorbic acid is an important antioxidant that plays an essential role in the biosynthesis of numerous bioactive substances. The detection of ascorbic acid has traditionally been achieved using high-performance liquid chromatography and absorption spectrophotometry assays. However, the development of fluorescence probes for this purpose is highly desired because they provide a much more convenient and highly sensitive technique for the detection of this material. OFF-ON-type fluorescent probes have been developed for the detection of non-fluorescent compounds. Photo-induced electron transfer and fluorescence resonance energy transfer are the two main fluorescence quenching mechanisms for the detection of ascorbic acid, and several fluorescence probes have been reported based on redox-responsive metals and quantum dots. Profluorescent nitroxide compounds have also been developed as non-metal organic fluorescence probes for ascorbic acid. These nitroxide systems have a stable unpaired electron and can therefore react with ascorbic acid and a strong fluorescence quencher. Furthermore, recent synthetic advances have allowed for the synthesis of α-substituted nitroxides with varying levels of reactivity towards ascorbic acid. In this review, we have discussed the design strategies used for the preparation of fluorescent probes for ascorbic acid, with particular emphasis on profluorescent nitroxides, which are unique radical-based redox-active fluorescent probes. PMID:26798193

  8. Interactive fluorophore and quencher pairs for labeling fluorescent nucleic acid hybridization probes.

    PubMed

    Marras, Salvatore A E

    2008-03-01

    The use of fluorescent nucleic acid hybridization probes that generate a fluorescence signal only when they bind to their target enables real-time monitoring of nucleic acid amplification assays. Real-time nucleic acid amplification assays markedly improves the ability to obtain qualitative and quantitative results. Furthermore, these assays can be carried out in sealed tubes, eliminating carryover contamination. Fluorescent nucleic acid hybridization probes are available in a wide range of different fluorophore and quencher pairs. Multiple hybridization probes, each designed for the detection of a different nucleic acid sequence and each labeled with a differently colored fluorophore, can be added to the same nucleic acid amplification reaction, enabling the development of high-throughput multiplex assays. In order to develop robust, highly sensitive and specific real-time nucleic acid amplification assays it is important to carefully select the fluorophore and quencher labels of hybridization probes. Selection criteria are based on the type of hybridization probe used in the assay, the number of targets to be detected, and the type of apparatus available to perform the assay. This article provides an overview of different aspects of choosing appropriate labels for the different types of fluorescent hybridization probes used with different types of spectrofluorometric thermal cyclers currently available.

  9. Copper(II)-lanthanide(III) coordination polymers constructed from pyridine-2,5-dicarboxylic acid: Preparation, crystal structure and photoluminescence

    SciTech Connect

    Xia Zhengqiang; Wei Qing; Chen Sanping; Feng Xinming; Xie Gang; Qiao Chengfang; Zhang Guochun; Gao Shengli

    2013-01-15

    A series of 3d-4f heterometallic coordination polymers, formulated as {l_brace} [Cu{sub 3}Ln{sub 2}(pydc){sub 6}(H{sub 2}O){sub 12}]{center_dot}4H{sub 2}O{r_brace} {sub n} [Ln=Tb (1), Eu (2), Dy (3), Ho (4), Lu (5)], {l_brace} [CuNd{sub 2}(pydc){sub 4}(H{sub 2}O){sub 3}]{center_dot}H{sub 2}O{r_brace} {sub n} (6) and {l_brace} [Cu{sub 3}Pr{sub 2}(pydc){sub 6}(H{sub 2}O){sub 13}]{center_dot}4H{sub 2}O{r_brace} {sub n} (7) (where H{sub 2}pydc=pyridine-2,5-dicarboxylic acid), have been hydrothermally prepared by reactions of H{sub 2}pydc ligand with lanthanide ions in the presence of Cu(II) ion. X-ray crystal structure analysis reveals that these compounds exhibit rich structural chemistry. 1-5 are isomorphous and present a two-dimensional network constructed from Ln{sub 2}Cu{sub 2}L{sub 2}(H{sub 2}O){sub 2} SBU rings and CuL{sub 2}(H{sub 2}O) building blocks. In 6, two-dimensional ladder-like layers based on Nd(III) belts and CuL{sub 2}O{sub 2} units are assembled by H{sub 2}pydc ligands into a three-dimensional open framework. Polymer 7 displays a two-dimensional wave-like layer structure containing two distinct ring units, in which a new coordination mode of the pydc{sup 2-} ligand is observed. The results indicate that the coordination flexibility of the pydc{sup 2-} ligand and lanthanide contraction effect play cooperative roles in the formation of coordination polymers with different polymeric architectures. Compounds 1-2 exhibit intense green and red luminescence emission characteristics of Tb(III) and Eu(III), respectively. Furthermore, elemental analyses (EA), infrared spectra (IR) and thermogravimetric analyses (TGA) of these compounds were also studied. - Graphical abstract: Seven 3d-4f heterometallic coordination polymers were synthesized by reactions of H{sub 2}pydc with lanthanide metal ions in the presence of Cu{sup 2+}, the effects of Cu{sup 2+} on the structures and photoluminescent properties of Ln-pydc{sup 2-} systems were investigated. Highlights

  10. Probe kit for identifying a base in a nucleic acid

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    2001-01-01

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  11. Detection and isolation of nucleic acid sequences using a bifunctional hybridization probe

    DOEpatents

    Lucas, Joe N.; Straume, Tore; Bogen, Kenneth T.

    2000-01-01

    A method for detecting and isolating a target sequence in a sample of nucleic acids is provided using a bifunctional hybridization probe capable of hybridizing to the target sequence that includes a detectable marker and a first complexing agent capable of forming a binding pair with a second complexing agent. A kit is also provided for detecting a target sequence in a sample of nucleic acids using a bifunctional hybridization probe according to this method.

  12. Fluorescent macrocyclic probes with pendant functional groups as markers of acidic organelles within live cells.

    PubMed

    Wadhavane, Prashant D; Izquierdo, M Ángeles; Lutters, Dennis; Burguete, M Isabel; Marín, María J; Russell, David A; Galindo, Francisco; Luis, Santiago V

    2014-02-07

    A new family of acidity sensitive fluorescent macrocycles has been synthesized and fully characterized. Their photophysical properties including emission quantum yield and fluorescence lifetime have been determined. The acid-base properties of the new molecules can be tuned by the incorporation of pendant functional groups. The nature of such functional groups (carboxylic acid or ester) influences dramatically the pKa of the probes, two compounds of which exhibit low values. Preliminary intracellular studies using confocal microscopy together with emission spectra of the probes from the cellular environment have shown that the synthesized fluorescent macrocycles mark the acidic organelles of RAW 264.7 macrophage cells.

  13. Synthesis, crystal structure, photoluminescence property and photoelectronic behavior of two uranyl-organic frameworks constructed from 1, 2, 4, 5-benzenetetracarboxylic acid as ligand.

    PubMed

    Hou, Ya-Nan; Xing, Yong-Heng; Bai, Feng-Ying; Guan, Qing-Lin; Wang, Xuan; Zhang, Rui; Shi, Zhan

    2014-04-05

    By using 1, 2, 4, 5-benzenetetracarboxylic acid as organic ligands, two uranyl coordination complexes, (UO2)2(bta)(DMA)2 (1) and [(UO2)2(bta)(μ3-OH2)]·2[HN(CH3)2]·H2O (2) (H4bta=1, 2, 4, 5-benzenetetracarboxylic acid, DMA=N,N-Dimethylacetamide) were synthesized. The X-ray single crystal analysis revealed that complex 1 exhibits a 3-demensional framework, while complex 2 exhibits a 2-demensional framework. In order to furthermore characterize the two complexes and extend their functional properties, spectroscopies of IR, UV-vis, photoluminescence and surface photovoltage were also studied primarily. In addition, thermogravimetric analyses and photocatalytic studies for complexes 1 and 2 were discussed in detail.

  14. Application of locked nucleic acid-based probes in fluorescence in situ hybridization.

    PubMed

    Fontenete, Sílvia; Carvalho, Daniel; Guimarães, Nuno; Madureira, Pedro; Figueiredo, Céu; Wengel, Jesper; Azevedo, Nuno Filipe

    2016-07-01

    Fluorescence in situ hybridization (FISH) employing nucleic acid mimics as probes is becoming an emerging molecular tool in the microbiology area for the detection and visualization of microorganisms. However, the impact that locked nucleic acid (LNA) and 2'-O-methyl (2'-OMe) RNA modifications have on the probe that is targeting microorganisms is unknown. In this study, the melting and hybridization efficiency properties of 18 different probes in regards to their use in FISH for the detection of the 16S rRNA of Helicobacter pylori were compared. For the same sequence and target, probe length and the type of nucleic acid mimics used as mixmers in LNA-based probes strongly influence the efficiency of detection. LNA probes with 10 to 15 mers showed the highest efficiency. Additionally, the combination of 2'-OMe RNA with LNA allowed an increase on the fluorescence intensities of the probes. Overall, these results have significant implications for the design and applications of LNA probes for the detection of microorganisms.

  15. Methods of staining target chromosomal DNA employing high complexity nucleic acid probes

    DOEpatents

    Gray, Joe W.; Pinkel, Daniel; Kallioniemi, Ol'li-Pekka; Kallioniemi, Anne; Sakamoto, Masaru

    2006-10-03

    Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyses. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML), retinoblastoma, ovarian and uterine cancers, and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

  16. Correlated high-resolution x-ray diffraction, photoluminescence, and atom probe tomography analysis of continuous and discontinuous In{sub x}Ga{sub 1−x}N quantum wells

    SciTech Connect

    Ren, Xiaochen; Riley, James R.; Lauhon, Lincoln J.; Koleske, Daniel D.

    2015-07-13

    Atom probe tomography (APT) is used to characterize the influence of hydrogen dosing during GaN barrier growth on the indium distribution of In{sub x}Ga{sub 1−x}N quantum wells, and correlated micro-photoluminescence is used to measure changes in the emission spectrum and efficiency. Relative to the control growth, hydrogen dosing leads to a 50% increase in emission intensity arising from discontinuous quantum wells that are narrower, of lower indium content, and with more abrupt interfaces. Simulations of carrier distributions based on APT composition profiles indicate that the greater carrier confinement leads to an increased radiative recombination rate. Furthermore, APT analysis of quantum well profiles enables refinement of x-ray diffraction analysis for more accurate nondestructive measurements of composition.

  17. Correlated high-resolution x-ray diffraction photoluminescence and atom probe tomography analysis of continuous and discontinuous InxGa1-xN quantum wells

    SciTech Connect

    Ren, Xiaochen; Riley, James R.; Koleske, Daniel; Lauhon, Lincoln J.

    2015-07-14

    In this study, atom probe tomography (APT) is used to characterize the influence of hydrogen dosing duringGaN barrier growth on the indium distribution of InxGa1-xN quantum wells, and correlatedmicro-photoluminescence is used to measure changes in the emission spectrum and efficiency. We found that relative to the control growth, hydrogen dosing leads to a 50% increase in emission intensity arising from discontinuous quantum wells that are narrower, of lower indium content, and with more abrupt interfaces. Additionally, simulations of carrier distributions based on APT composition profiles indicate that the greater carrier confinement leads to an increased radiative recombination rate. Furthermore, APT analysis of quantum well profiles enables refinement of x-ray diffractionanalysis for more accurate nondestructive measurements of composition.

  18. Time-resolved detection probe for homogeneous nucleic acid analyses in one-step format.

    PubMed

    Laitala, Ville; Ylikoski, Alice; Raussi, Hanna-Mari; Ollikka, Pia; Hemmilä, Ilkka

    2007-02-01

    We report here an extension of homogeneous assays based on fluorescence intensity and lifetime measuring on DNA hybridization. A novel decay probe that allows simple one-step nucleic acid detection with subnanomolar sensitivity, and is suitable for closed-tube applications, is introduced. The decay probe uses fluorescence resonance energy transfer (FRET) between a europium chelate donor and an organic fluorophore acceptor. The substantial change in the acceptor emission decay time on hybridization with the target sequence allows the direct separation of the hybridized and unhybridized probe populations in a time-resolved measurement. No additional sample manipulation or self-hybridization of the probes is required. The wavelength and decay time of a decay probe can be adjusted according to the selection of probe length and acceptor fluorophore, thereby making the probes applicable to multiplexed assays. Here we demonstrate the decay probe principle and decay probe-based, one-step, dual DNA assay using celiac disease-related target oligonucleotides (single-nucleotide polymorphisms [SNPs]) as model analytes. Decay probes showed specific response for their complementary DNA target and allowed good signal deconvolution based on simultaneous optical and temporal filtering. This technique potentially could be used to further increase the number of simultaneously detected DNA targets in a simple one-step homogeneous assay.

  19. Terbium fluorescence as a sensitive, inexpensive probe for UV-induced damage in nucleic acids.

    PubMed

    El-Yazbi, Amira F; Loppnow, Glen R

    2013-07-05

    Much effort has been focused on developing methods for detecting damaged nucleic acids. However, almost all of the proposed methods consist of multi-step procedures, are limited, require expensive instruments, or suffer from a high level of interferences. In this paper, we present a novel simple, inexpensive, mix-and-read assay that is generally applicable to nucleic acid damage and uses the enhanced luminescence due to energy transfer from nucleic acids to terbium(III) (Tb(3+)). Single-stranded oligonucleotides greatly enhance the Tb(3+) emission, but duplex DNA does not. With the use of a DNA hairpin probe complementary to the oligonucleotide of interest, the Tb(3+)/hairpin probe is applied to detect ultraviolet (UV)-induced DNA damage. The hairpin probe hybridizes only with the undamaged DNA. However, the damaged DNA remains single-stranded and enhances the intrinsic fluorescence of Tb(3+), producing a detectable signal directly proportional to the amount of DNA damage. This allows the Tb(3+)/hairpin probe to be used for sensitive quantification of UV-induced DNA damage. The Tb(3+)/hairpin probe showed superior selectivity to DNA damage compared to conventional molecular beacons probes (MBs) and its sensitivity is more than 2.5 times higher than MBs with a limit of detection of 4.36±1.2 nM. In addition, this probe is easier to synthesize and more than eight times cheaper than MBs, which makes its use recommended for high-throughput, quantitative analysis of DNA damage.

  20. Determination of Captopril Based on the Photoluminescence Quenching of the pH Sensitive Mercaptopropanoic Acid Capped CdTe Quantum Dots

    NASA Astrophysics Data System (ADS)

    Khan, S.; Lima, A. A.; Aucelio, R. Q.

    2017-01-01

    The determination of captopril was performed by measuring the photoluminescence quenching of pH sensitive mercaptopropanoic acid capped CdTe quantum dots. Under optimum conditions, the calibration model (log F0/F as a function of the concentration of captopril) was linear up to 8 × 10-6 mol/L (1.7 μg/mL) and the limit of detection (xb - 3sb) was 2.7 × 10-7 mol/L (18 ng/mL). A possible mechanism for quenching is proposed. The method was applied in the determination of captopril in two commercial pharmaceutical formulations, indicating that it can be used for simple and fast quantitative control of commercial medicines or pharmaceutical preparations.

  1. A novel acidic pH fluorescent probe based on a benzothiazole derivative.

    PubMed

    Ma, Qiujuan; Li, Xian; Feng, Suxiang; Liang, Beibei; Zhou, Tiqiang; Xu, Min; Ma, Zhuoyi

    2017-04-15

    A novel acidic pH fluorescent probe 1 based on a benzothiazole derivative has been designed, synthesized and developed. The linear response range covers the acidic pH range from 3.44 to 6.46, which is valuable for pH researches in acidic environment. The evaluated pKa value of the probe 1 is 4.23. The fluorescence enhancement of the studied probe 1 with an increase in hydrogen ions concentration is based on the hindering of enhanced photo-induced electron transfer (PET) process. Moreover, the pH sensor possesses a highly selective response to H(+) in the presence of metal ions, anions and other bioactive small molecules which would be interfere with its fluorescent pH response. Furthermore, the probe 1 responds to acidic pH with short response time that was less than 1min. The probe 1 has been successfully applied to confocal fluorescence imaging in live HeLa cells and can selectively stain lysosomes. All of such good properties prove it can be used to monitoring pH fluctuations in acidic environment with high sensitivity, pH dependence and short response time.

  2. A novel acidic pH fluorescent probe based on a benzothiazole derivative

    NASA Astrophysics Data System (ADS)

    Ma, Qiujuan; Li, Xian; Feng, Suxiang; Liang, Beibei; Zhou, Tiqiang; Xu, Min; Ma, Zhuoyi

    2017-04-01

    A novel acidic pH fluorescent probe 1 based on a benzothiazole derivative has been designed, synthesized and developed. The linear response range covers the acidic pH range from 3.44 to 6.46, which is valuable for pH researches in acidic environment. The evaluated pKa value of the probe 1 is 4.23. The fluorescence enhancement of the studied probe 1 with an increase in hydrogen ions concentration is based on the hindering of enhanced photo-induced electron transfer (PET) process. Moreover, the pH sensor possesses a highly selective response to H+ in the presence of metal ions, anions and other bioactive small molecules which would be interfere with its fluorescent pH response. Furthermore, the probe 1 responds to acidic pH with short response time that was less than 1 min. The probe 1 has been successfully applied to confocal fluorescence imaging in live HeLa cells and can selectively stain lysosomes. All of such good properties prove it can be used to monitoring pH fluctuations in acidic environment with high sensitivity, pH dependence and short response time.

  3. Photoinduced spectral changes of photoluminescent gold nanoclusters.

    PubMed

    Matulionytė, Marija; Marcinonytė, Raminta; Rotomskis, Ričardas

    2015-05-01

    Ultrasmall photoluminescent gold nanoclusters (Au NCs), composed of several atoms with sizes up to a few nanometers, have recently stimulated extensive interest. Unique molecule-like behaviors, low toxicity, and facile synthesis make photoluminescent Au NCs a very promising alternative to organic fluorophores and semiconductor quantum dots (QDs) in broad ranges of biomedical applications. However, using gold nanoparticles (Au NPs) for bioimaging might cause their degradation under continuous excitation with UV light, which might result in toxicity. We report spectral changes of photoluminescent 2-(N-morpholino) ethanesulfonic acid (MES)-coated (Au-MES) NCs under irradiation with UV/blue light. Photoluminescent water soluble Au- MES NCs with a photoluminescence (PL) band maximum at 476 nm (λex = 420 nm) were synthesized. Under irradiation with 402 nm wavelength light the size of photoluminescent Au-MES NCs decreased (λem = 430 nm). Irradiating the sample solution with 330 nm wavelength light, nonluminescent Au NPs were disrupted, and photoluminescent Au NCs (λem = 476 nm) were formed. Irradiation with 330 nm wavelength light did not directly affect photoluminescent Au-MES NCs, however, increase in PL intensity indicated the formation of photoluminescent Au NCs from the disrupted nonluminescent Au NPs. This study gives a good insight into the photostability of MES-coated Au NPs under continuous excitation with UV/blue light.

  4. Photoinduced spectral changes of photoluminescent gold nanoclusters

    NASA Astrophysics Data System (ADS)

    Matulionytė, Marija; Marcinonytė, Raminta; Rotomskis, Ričardas

    2015-05-01

    Ultrasmall photoluminescent gold nanoclusters (Au NCs), composed of several atoms with sizes up to a few nanometers, have recently stimulated extensive interest. Unique molecule-like behaviors, low toxicity, and facile synthesis make photoluminescent Au NCs a very promising alternative to organic fluorophores and semiconductor quantum dots (QDs) in broad ranges of biomedical applications. However, using gold nanoparticles (Au NPs) for bioimaging might cause their degradation under continuous excitation with UV light, which might result in toxicity. We report spectral changes of photoluminescent 2-(N-morpholino) ethanesulfonic acid (MES)-coated (Au-MES) NCs under irradiation with UV/blue light. Photoluminescent water soluble Au-MES NCs with a photoluminescence (PL) band maximum at 476 nm (λex=420 nm) were synthesized. Under irradiation with 402 nm wavelength light the size of photoluminescent Au-MES NCs decreased (λem=430 nm). Irradiating the sample solution with 330 nm wavelength light, nonluminescent Au NPs were disrupted, and photoluminescent Au NCs (λem=476 nm) were formed. Irradiation with 330 nm wavelength light did not directly affect photoluminescent Au-MES NCs, however, increase in PL intensity indicated the formation of photoluminescent Au NCs from the disrupted nonluminescent Au NPs. This study gives a good insight into the photostability of MES-coated Au NPs under continuous excitation with UV/blue light.

  5. Structural variations and photoluminescent properties of a series of metal-organic frameworks constructed from 5-(4-carboxybenzoylamino)-isophthalic acid

    SciTech Connect

    Zhao, Wen; Zhang, Li-Juan; Zhao, Xiao-Li

    2013-06-01

    Five new metal-organic frameworks (MOFs) with 5-(4-carboxybenzoylamino)-isophthalic acid (H₃L), namely, [Cd₉L₆(DMA)₆]·4DMA (1), [Cd₃L₂(H₂O)₉]·4H₂O (2), [LaL(H₂O)₄]·2H₂O (3), [CeL(H₂O)₄]·H₂O (4) and [Tb(HL)(H₂L)(H₂O)₃]·5H₂O (5) (DMA=N,N-dimethylacetamide), have been synthesized. Complex 1 shows a three-dimensional architecture generated from linkage of Cd–O chains via L³⁻ ligands. Minor variations in synthetic conditions of 1 afforded 2, which features an interesting 2D→3D catenation architecture containing helical chains. Complexes 3 and 4 are isostructural and each feature a two-dimensional architecture constructed from the linkage of L³⁻ with Ln³⁺. Complex 5 displays a chain-like structure, of which the most interesting feature is the existence of free carboxylic acid (–COOH) group which may confer unique functionality. Moreover, the investigations of the thermal stability, powder X-ray diffractions and solid-state photoluminescent properties for these crystalline materials have been carried out. - Graphical Abstract: Solvothermal reactions of tricarboxylate ligand H₃L with Cd²⁺/Ln³⁺ has yielded a series of new MOFs containing interesting structural motifs. Highlights: • A tricarboxylate ligand whose coordinating functionalities are not symmetry equivalent is employed to construct MOFs. • Complex 2 features an interesting 2D→3D catenation architecture containing helical chains. • Complex 3 feature chain-like structure containing free – COOH group, which may confer unique functionality. • Photoluminescent properties and thermal behaviors for 1–5 have been reported.

  6. Development of Peptide Nucleic Acid Probes for Detection of the HER2 Oncogene

    PubMed Central

    Song, Young K.; Evangelista, Jennifer; Aschenbach, Konrad; Johansson, Peter; Wen, Xinyu; Chen, Qingrong; Lee, Albert; Hempel, Heidi; Gheeya, Jinesh S.; Getty, Stephanie; Gomez, Romel; Khan, Javed

    2013-01-01

    Peptide nucleic acids (PNAs) have gained much interest as molecular recognition tools in biology, medicine and chemistry. This is due to high hybridization efficiency to complimentary oligonucleotides and stability of the duplexes with RNA or DNA. We have synthesized 15/16-mer PNA probes to detect the HER2 mRNA. The performance of these probes to detect the HER2 target was evaluated by fluorescence imaging and fluorescence bead assays. The PNA probes have sufficiently discriminated between the wild type HER2 target and the mutant target with single base mismatches. Furthermore, the probes exhibited excellent linear concentration dependence between 0.4 to 400 fmol for the target gene. The results demonstrate potential application of PNAs as diagnostic probes with high specificity for quantitative measurements of amplifications or over-expressions of oncogenes. PMID:23593123

  7. Probing linker design in citric acid-ciprofloxacin conjugates.

    PubMed

    Milner, Stephen J; Snelling, Anna M; Kerr, Kevin G; Abd-El-Aziz, Ahmad; Thomas, Gavin H; Hubbard, Roderick E; Routledge, Anne; Duhme-Klair, Anne-Kathrin

    2014-08-15

    A series of structurally related citric acid-ciprofloxacin conjugates was synthesised to investigate the influence of the linker between citric acid and ciprofloxacin on antibacterial activities. Minimum inhibitory concentrations (MICs) were determined against a panel of reference strains and clinical isolates of bacteria associated with infection in humans and correlated with the DNA gyrase inhibitory activity. The observed trend was rationalised by computational modelling.

  8. Permeabilization of mycolic-acid-containing actinomycetes for in situ hybridization with fluorescently labelled oligonucleotide probes.

    PubMed

    Macnaughton, S J; O'Donnell, A G; Embley, T M

    1994-10-01

    The application of whole-cell hybridization using labelled oligonucleotide probes in microbial systematics and ecology is limited by difficulties in permeabilizing many Gram-positive organisms. In this investigation paraformaldehyde treatment, acid methanolysis and acid hydrolysis were evaluated as a means of permeabilizing mycolic-acid-containing actinomycetes prior to hybridization with a fluorescently labelled oligonucleotide probe designed to bind to a conserved sequence of bacterial 16S rRNA. Methods were evaluated on stationary-phase cultures of Gordona bronchialis, Mycobacterium fortuitum, Nocardia asteroides, N. brasiliensis, Rhodococcus equi, R. erythropolis, R. fascians, R. rhodochrous and Tsukamurella paurometabola, none of which could be probed following 4% (w/v) paraformaldehyde fixation. For comparison and to test the general applicability of mild acid pretreatments, Bacillus subtilis, Lactobacillus plantarum, Escherichia coli and Pseudomonas putida were also studied. The data showed that most of the mycolic-acid-containing organisms were successfully permeabilized by mild acid hydrolysis in 1 M HCl at 37 degrees C. Cells were treated for different lengths of time. In general, the mycolic-acid-containing organisms required between 30 and 50 min hydrolysis, whereas B. subtilis, E. coli and P. putida were rendered permeable in only 10 min. Interestingly, L. plantarum could not be permeabilized using acid hydrolysis even after 60 min exposure to 1 M HCl.

  9. The effect of citric acid on morphology and photoluminescence properties of white light emitting ZnO-SiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Sivakami, R.; Thiyagarajan, P.

    2016-07-01

    The white light emitting ZnO-SiO2 nanocomposites were synthesized by sol-gel combustion method using zinc nitrate, citric acid and tetraethoxysilane. To analyze the effect of fuel content on the photoluminescence properties of ZnO-SiO2 nanocomposites, the citric acid content was varied as 1, 5, and 10 moles with respect to one mole of zinc. The SEM images of the nanocomposites revealed the spherical, flower and platelet like morphology with variation in citric acid content and annealing temperatures. The ZnO-SiO2 nanocomposites prepared with various Zn:CA ratio excited at UV (280 nm), near UV (365 nm), violet (405 nm) and blue (465 nm) wavelength showed blue and greenish-yellow emission. Among all ratios, the ZnO-SiO2 nanocomposites with Zn:CA - 1:1 ratio showed the intense broad band emission compared to Zn:CA - 1:5 and 1:10 values. This particular composition of sample excited under violet (405 nm) LED source shows white light, as confirmed by the CIE chromaticity coordinates (x = 0.342, y = 0.318).

  10. Acidity characterization of heterogeneous catalysts by solid-state NMR spectroscopy using probe molecules.

    PubMed

    Zheng, Anmin; Liu, Shang-Bin; Deng, Feng

    2013-01-01

    Characterization of the surface acidic properties of solid acid catalysts is a key issue in heterogeneous catalysis. Important acid features of solid acids, such as their type (Brønsted vs. Lewis acid), distribution and accessibility (internal vs. external sites), concentration (amount), and strength of acid sites are crucial factors dictating their reactivity and selectivity. This short review provides information on different solid-state NMR techniques used for acidity characterization of solid acid catalysts. In particular, different approaches using probe molecules containing a specific nucleus of interest, such as pyridine-d5, 2-(13)C-acetone, trimethylphosphine, and trimethylphosphine oxide, are compared. Incorporation of valuable information (such as the adsorption structure, deprotonation energy, and NMR parameters) from density functional theory (DFT) calculations can yield explicit correlations between the chemical shift of adsorbed probe molecules and the intrinsic acid strength of solid acids. Methods that combine experimental NMR data with DFT calculations can therefore provide both qualitative and quantitative information on acid sites.

  11. Aptamer and 5-fluorouracil dual-loading Ag2S quantum dots used as a sensitive label-free probe for near-infrared photoluminescence turn-on detection of CA125 antigen.

    PubMed

    Jin, Hui; Gui, Rijun; Gong, Jun; Huang, Wenxue

    2017-06-15

    In this article, Ag2S quantum dots (QDs) were prepared by a facile aqueous synthesis method, using thiourea as a new sulfur precursor. Based on electrostatic interactions, 5-fluorouracil (5-Fu) was combined with the aptamer of CA125 antigen to fabricate aptamer/5-Fu complex. The surface of as-prepared Ag2S QDs was modified with polyethylenimine, followed by combination with the aptamer/5-Fu complex to form Ag2S QDs/aptamer/5-Fu hybrids. During the combination of Ag2S QDs with aptamer/5-Fu complex, near-infrared (NIR) photoluminescence (PL) of QDs (peaked at 850nm) was markedly reduced under excitation at 625nm, attributed to photo-induced electron transfer from QDs to 5-Fu. However, the addition of CA125 induced obvious NIR PL recovery, which was ascribed to the strong binding affinity of CA125 with its aptamer, and the separation of aptamer/5-Fu complex from the surface of QDs. Hence, the Ag2S QDs/aptamer/5-Fu hybrids were developed as a novel NIR PL turn-on probe of CA125. In the concentration range of [CA125] from 0.1 to 10(6)ngmL(-1), there were a good linear relationship between NIR PL intensities of Ag2S QDs and Log[CA125], and a low limit of detection of 0.07ngmL(-1). Experimental results revealed the highly selective and sensitive NIR PL responses of this probe to CA125, over other potential interferences. In real human body fluids, this probe also exhibited superior analytical performance, together with high detection recoveries.

  12. Tethered phytic acid as a probe for measuring phytase activity.

    PubMed

    Berry, Duane F; Berry, David A

    2005-06-15

    A novel approach for measuring phytase activity is presented. We have developed a new chromophoric substrate analog of phytic acid, 5-O-[6-(benzoylamino)hexyl]-d-myo-inositol-1,2,3,4,6-pentakisphosphate that permits direct measurement of the phosphate ester bond-cleavage reaction using HPLC. This compound, along with its dephosphorylated T-phosphatidylinositol intermediates, are quantified using reversed phase chromatography with UV detection.

  13. Probing lipid peroxidation by using linoleic acid and benzophenone.

    PubMed

    Andreu, Inmaculada; Neshchadin, Dmytro; Rico, Enrique; Griesser, Markus; Samadi, Abdelouahid; Morera, Isabel M; Gescheidt, Georg; Miranda, Miguel A

    2011-08-29

    A thorough mechanistic study has been performed on the reaction between benzophenone (BZP) and a series of 1,4-dienes, including 1,4-cyclohexadiene (CHD), 1,4-dihydro-2-methylbenzoic acid (MBA), 1,4-dihydro-1,2-dimethylbenzoic acid (DMBA) and linoleic acid (LA). A combination of steady-state photolysis, laser flash photolysis (LFP), and photochemically induced dynamic nuclear polarization (photo-CIDNP) have been used. Irradiation of BZP and CHD led to a cross-coupled sensitizer-diene product, together with 6, 7, and 8. With MBA and DMBA as hydrogen donors, photoproducts arising from cross-coupling of sensitizer and diene radicals were found; compound 7 was also obtained, but 6 and o-toluic acid were only isolated in the irradiation of BZP with MBA. Triplet lifetimes were determined in the absence and in the presence of several diene concentrations. All three model compounds showed similar reactivity (k(q) ≈10(8)  M(-1)  s(-1)) towards triplet excited BZP. Partly reversible hydrogen abstraction of the allylic hydrogen atoms of CHD, MBA, and DMBA was also detected by photo-CIDNP on different timescales. Polarizations of the diamagnetic products were in full agreement with the results derived from LFP. Finally, LA also underwent partly reversible hydrogen abstraction during photoreaction with BZP. Subsequent hydrogen transfer between primary radicals led to conjugated derivatives of LA. The unpaired electron spin population in linoleyl radical (LA(.)) was predominantly found on H(1-5) protons. To date, LA-related radicals were only reported upon hydrogen transfer from highly substituted model compounds by steady-state EPR spectroscopy. Herein, we have experimentally established the formation of LA(.) and shown that it converts into two dominating conjugated isomers on the millisecond timescale. Such processes are at the basis of alterations of membrane structures caused by oxidative stress.

  14. Probing fatty acid metabolism in bacteria, cyanobacteria, green microalgae and diatoms with natural and unnatural fatty acids.

    PubMed

    Beld, Joris; Abbriano, Raffaela; Finzel, Kara; Hildebrand, Mark; Burkart, Michael D

    2016-04-01

    In both eukaryotes and prokaryotes, fatty acid synthases are responsible for the biosynthesis of fatty acids in an iterative process, extending the fatty acid by two carbon units every cycle. Thus, odd numbered fatty acids are rarely found in nature. We tested whether representatives of diverse microbial phyla have the ability to incorporate odd-chain fatty acids as substrates for their fatty acid synthases and their downstream enzymes. We fed various odd and short chain fatty acids to the bacterium Escherichia coli, cyanobacterium Synechocystis sp. PCC 6803, green microalga Chlamydomonas reinhardtii and diatom Thalassiosira pseudonana. Major differences were observed, specifically in the ability among species to incorporate and elongate short chain fatty acids. We demonstrate that E. coli, C. reinhardtii, and T. pseudonana can produce longer fatty acid products from short chain precursors (C3 and C5), while Synechocystis sp. PCC 6803 lacks this ability. However, Synechocystis can incorporate and elongate longer chain fatty acids due to acyl-acyl carrier protein synthetase (AasS) activity, and knockout of this protein eliminates the ability to incorporate these fatty acids. In addition, expression of a characterized AasS from Vibrio harveyii confers a similar capability to E. coli. The ability to desaturate exogenously added fatty acids was only observed in Synechocystis and C. reinhardtii. We further probed fatty acid metabolism of these organisms by feeding desaturase inhibitors to test the specificity of long-chain fatty acid desaturases. In particular, supplementation with thia fatty acids can alter fatty acid profiles based on the location of the sulfur in the chain. We show that coupling sensitive gas chromatography mass spectrometry to supplementation of unnatural fatty acids can reveal major differences between fatty acid metabolism in various organisms. Often unnatural fatty acids have antibacterial or even therapeutic properties. Feeding of short

  15. Intra-albumin migration of bound fatty acid probed by spin label ESR

    SciTech Connect

    Gurachevsky, Andrey . E-mail: a.gurachevsky@medinnovation.de; Shimanovitch, Ekaterina; Gurachevskaya, Tatjana; Muravsky, Vladimir

    2007-09-07

    Conventional ESR spectra of 16-doxyl-stearic acid bound to bovine and human serum albumin were recorded at different temperatures in order to investigate the status of spin-labeled fatty acid in the interior of the protein globule. A computer spectrum simulation of measured spectra, performed by non-linear least-squares fits, clearly showed two components corresponding to strongly and weakly immobilized fatty acid molecules. The two-component model was verified on spectra measured at different pH. Thermodynamic parameters of the spin probe exchange between two spin probe states were analyzed. It was concluded that at physiological conditions, fatty acid molecules permanently migrate in the globule interior between the specific binding sites and a space among albumin domains.

  16. Structural variations and photoluminescent properties of a series of metal-organic frameworks constructed from 5-(4-carboxybenzoylamino)-isophthalic acid

    NASA Astrophysics Data System (ADS)

    Zhao, Wen; Zhang, Li-Juan; Zhao, Xiao-Li

    2013-06-01

    Five new metal-organic frameworks (MOFs) with 5-(4-carboxybenzoylamino)-isophthalic acid (H3L), namely, [Cd9L6(DMA)6]·4DMA (1), [Cd3L2(H2O)9]·4H2O (2), [LaL(H2O)4]·2H2O (3), [CeL(H2O)4]·H2O (4) and [Tb(HL)(H2L)(H2O)3]·5H2O (5) (DMA=N,N-dimethylacetamide), have been synthesized. Complex 1 shows a three-dimensional architecture generated from linkage of Cd-O chains via L3- ligands. Minor variations in synthetic conditions of 1 afforded 2, which features an interesting 2D→3D catenation architecture containing helical chains. Complexes 3 and 4 are isostructural and each feature a two-dimensional architecture constructed from the linkage of L3- with Ln3+. Complex 5 displays a chain-like structure, of which the most interesting feature is the existence of free carboxylic acid (-COOH) group which may confer unique functionality. Moreover, the investigations of the thermal stability, powder X-ray diffractions and solid-state photoluminescent properties for these crystalline materials have been carried out.

  17. Bioavailability of xenobiotics in unsaturated soils – implications for nucleic acid based stable isotope probing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of stable isotopes to label phylogenetically informative biomolecules (phospholipid fatty acids, DNA, or RNA), typically referred to as stable isotope probing (SIP) has the potential of providing definitive evidence that a detected population is active in a specific process, if that process ...

  18. Trimethylamine as a probe molecule to differentiate acid sites in Y-FAU zeolite: FTIR study.

    PubMed

    Sarria, Francisca Romero; Blasin-Aubé, Vanessa; Saussey, Jacques; Marie, Olivier; Daturi, Marco

    2006-07-06

    In heterogeneous catalysis acidity has a very important influence on activity and selectivity: correct determination of acidic properties is a base to improve industrial processes. The aim of this work was to study trimethylamine (TMA) as a probe molecule able to distinguish between the different Brønsted acid sites in zeolitic frameworks. Our work mainly focused on faujasite-type zeolites because the HY zeolite is one of the most used acidic catalysts in industrial processes. In this paper, typical IR bands assigned to TMA-protonated species (formed in supercages) are detected in the HY zeolite. TMA interacting by hydrogen bonding with the acid sites located in the sodalite units is also observed. The wavenumbers of some typical IR bands assigned to TMA-protonated species appear to depend on the acidic strength, and a complementary study with ZSM-5 and X-FAU samples confirms this proposition.

  19. Measuring nanometer distances in nucleic acids using a sequence-independent nitroxide probe

    PubMed Central

    Qin, Peter Z; Haworth, Ian S; Cai, Qi; Kusnetzow, Ana K; Grant, Gian Paola G; Price, Eric A; Sowa, Glenna Z; Popova, Anna; Herreros, Bruno; He, Honghang

    2008-01-01

    This protocol describes the procedures for measuring nanometer distances in nucleic acids using a nitroxide probe that can be attached to any nucleotide within a given sequence. Two nitroxides are attached to phosphorothioates that are chemically substituted at specific sites of DNA or RNA. Inter-nitroxide distances are measured using a four-pulse double electron–electron resonance technique, and the measured distances are correlated to the parent structures using a Web-accessible computer program. Four to five days are needed for sample labeling, purification and distance measurement. The procedures described herein provide a method for probing global structures and studying conformational changes of nucleic acids and protein/nucleic acid complexes. PMID:17947978

  20. Modeling aqueous ozone/UV process using oxalic acid as probe chemical.

    PubMed

    Garoma, Temesgen; Gurol, Mirat D

    2005-10-15

    A kinetic model that describes the removal of organic pollutants by an ozone/UV process is described. Oxalic acid, which reacts with a very low rate constant with ozone and relatively high rate constant with hydroxyl radical (OH*), was used as the probe chemical to model the process. The model was verified by experimental data on concentrations of oxalic acid and hydrogen peroxide (H202) under various experimental conditions, i.e., ozone gas dosage, UV light intensity, and varying oxalic acid concentrations.

  1. Submonolayer Uniformity of Type II InAs/GaInSb W-shaped Quantum Wells Probed by Full-Wafer Photoluminescence Mapping in the Mid-infrared Spectral Range.

    PubMed

    Dyksik, Mateusz; Motyka, Marcin; Sęk, Grzegorz; Misiewicz, Jan; Dallner, Matthias; Weih, Robert; Kamp, Martin; Höfling, Sven

    2015-12-01

    The spatial uniformity of GaSb- and InAs substrate-based structures containing type II quantum wells was probed by means of large-scale photoluminescence (PL) mapping realized utilizing a Fourier transform infrared spectrometer. The active region was designed and grown in a form of a W-shaped structure with InAs and GaInSb layers for confinement of electrons and holes, respectively. The PL spectra were recorded over the entire 2-in. wafers, and the parameters extracted from each spectrum, such as PL peak energy position, its linewidth and integrated intensity, were collected in a form of two-dimensional spatial maps. Throughout the analysis of these maps, the wafers' homogeneity and precision of the growth procedure were investigated. A very small variation of PL peak energy over the wafer indicates InAs quantum well width fluctuation of only a fraction of a monolayer and hence extraordinary thickness accuracy, a conclusion further supported by high uniformity of both the emission intensity and PL linewidth.

  2. Roles of the methyl and methylene groups of mercapto acids in the photoluminescence efficiency and carrier trapping dynamics of CdTe QDs.

    PubMed

    Chandra Sekhar, M; De, Apurba; Hossain, Sk Saddam; Samanta, Anunay

    2017-01-04

    Surface protection using an appropriate ligand is essential for controlling the size, stability and luminescence properties of the quantum dots (QDs). Though 3-mercaptopropanoic acid (3-MPA) is regarded as the most suitable protecting ligand among the mercapto acids for water soluble CdTe QDs, one receives a different picture from recent studies, which report a much higher luminescence efficiency of 3-mercaptobutyric acid (3-MBA) capped QDs compared with those capped by 3-MPA and attribute the observation to the influence of the side methyl group of mercapto acids. Herein we report the luminescence properties and carrier trapping dynamics of four different, but structurally related mercapto acid capped CdTe QDs prepared using a different method. The results show that these QDs are much more fluorescent than those prepared directly in an aqueous environment and surprisingly, no enhanced luminescence for the QDs capped by mercapto acids containing a side methyl group is observed. Ultrafast pump-probe measurements confirm these results in addition to providing insight into the carrier trapping dynamics of these systems. It is shown that our findings, which appear to be in conflict with the recent literature, can be rationalized and the exact role of the side methyl group of the mercapto acids can be understood by careful analysis of the results taking into consideration the difference in the methods of preparation of the QDs in the two cases.

  3. Development of specific fluorescent oligonucleotide probes for in situ identification of wine lactic acid bacteria.

    PubMed

    Blasco, Lucía; Ferrer, Sergi; Pardo, Isabel

    2003-08-08

    A rapid method for the identification of lactic acid bacteria (LAB) from wine has been developed. This method is based on fluorescence in situ hybridisation (FISH), using fluorescent oligonucleotide probes, homologous to 16S rDNA of those species of LAB commonly found in wines. The protocol for the specific detection of these bacteria was established through the hybridisation of 36 reference strains. The specificity of the probes was evaluated by using pure cultures. Probes were used to identify species in different wines, making it evident that direct identification and quantification from natural samples without culturing is also possible. The results show that FISH is a promising technique for the rapid identification of LAB, allowing positive identification in a few hours (4-16 h).

  4. Electron spin echo modulation studies of doxylstearic acid spin probes in frozen vesicles: Interaction of the spin probe with D sub 2 O and effects of cholesterol addition

    SciTech Connect

    Hiff, T.; Kevan, L. )

    1989-02-23

    Electron spin echo studies have been carried out for a series of x-doxylstearic acid (x = 5, 7, 10, 12 and 16) spin probes in frozen deuteriated aqueous solutions of phospholipid vesicles and cationic dioctadecyldimethylammonium chloride (DODAC) vesicles. Modulation effects due to interactions of the nitroxide group of the spin probes with D{sub 2}O give information about the conformations of the probes and the degree of hydration of the surfactant headgroups as well as about the degree of packing of the alkyl chain. We show that DODAC headgroups are more hydrated than choline headgroups and that the doxylstearic acid probes show a larger tendency for bending in DODAC vesicles than in phospholipid vesicles. Upon addition of cholesterol into phospholipid vesicles, the headgroups are separated and their degree of hydration increases.

  5. Structure and photoluminescence tuning features of Mn(2+)- and Ln(3+)-activated Zn-based heterometal-organic frameworks (MOFs) with a single 5-methylisophthalic acid ligand.

    PubMed

    Bo, Qi-Bing; Wang, Hong-Yan; Wang, Da-Qi; Zhang, Zhen-Wei; Miao, Jin-Ling; Sun, Guo-Xin

    2011-10-17

    In attempts to investigate whether the photoluminescence properties of the Zn-based heterometal-organic frameworks (MOFs) could be tuned by doping different Ln(3+) (Ln = Sm, Eu, Tb) and Mn(2+) ions, seven novel 3D homo- and hetero-MOFs with a rich variety of network topologies, namely, [Zn(mip)](n) (Zn-Zn), [Zn(2)Mn(OH)(2)(mip)(2)](n) (Zn-Mn), [Mn(2)Mn(OH)(2)(mip)(2)](n) (Mn-Mn), [ZnSm(OH)(mip)(2)](n) (Zn-Sm), [ZnEu(OH)(mip)(2)](n) (Zn-Eu1), [Zn(5)Eu(OH)(H(2)O)(3)(mip)(6)·(H(2)O)](n) (Zn-Eu2), and [Zn(5)Tb(OH)(H(2)O)(3)(mip)(6)](n) (Zn-Tb), (mip = 5-methylisophthalate dianion), have been synthesized hydrothermally based on a single 5-methylisophthalic acid ligand. All compounds are fully structurally characterized by elemental analysis, FT-IR spectroscopy, TG-DTA analysis, single-crystal X-ray diffraction, and X-ray powder diffraction (XRPD) techniques. The various connectivity modes of the mip linkers generate four types of different structures. Type I (Zn-Zn) is a 3D homo-MOF with helical channels composed of Zn(2)(COO)(4) SBUs (second building units). Type II (Zn-Mn and Mn-Mn) displays a nest-like 3D homo- or hetero-MOF featuring window-shaped helical channels composed of Zn(4)Mn(2)(OH)(4)(COO)(8) or Mn(4)Mn(2)(OH)(4)(COO)(8) SBUs. Type III (Zn-Sm and Zn-Eu1) presents a complicated corbeil-like 3D hetero-MOF with irregular helical channels composed of (SmZnO)(2)(COO)(8) or (EuZnO)(2)(COO)(8) heterometallic SBUs. Type IV (Zn-Eu2 and Zn-Tb) contains a heterometallic SBU Zn(5)Eu(OH)(COO)(12) or Zn(5)Tb(OH)(COO)(12), which results in a 3D hetero-MOF featuring irregular channels impregnated by parts of the free and coordinated water molecules. Photoluminescence properties indicate that all of the compounds exhibit photoluminescence in the solid state at room temperature. Compared with a broad emission band at ca. 475 nm (λ(ex) = 380 nm) for Zn-Zn, compound Zn-Mn exhibits a remarkably intense emission band centered at 737 nm (λ(ex) = 320 nm) due to the

  6. Photoluminescence studies on the complexation of Eu(III) and Tb(III) with acetohydroxamic acid (AHA) in nitrate medium

    NASA Astrophysics Data System (ADS)

    Pathak, P. N.; Mohapatra, M.; Godbole, S. V.

    2013-11-01

    UREX process has been proposed for selective extraction of U(VI) and Tc(VII) from nitric acid medium (∼1 M HNO3) using tri-n-butyl phosphate (TBP) as extractant and retaining Pu, Np and fission products in the aqueous phase. The feasibility of the use of luminescence spectroscopy as a technique to understand the complexation of trivalent f-elements cations viz. Eu(III) and Tb(III) with acetohydroxamic acid (AHA) in nitric acid medium has been examined. The luminescence lifetimes for the 1 × 10-3 M Eu(III) and AHA complex system decreased with increased AHA concentration from 116 ± 0.2 μs (no AHA) to 1.6 ± 0.1 μs (0.1 M AHA) which was attributed to dynamic quenching. The corrected fluorescence intensities were used to calculate the stability constant (log K) for the formation of 1:1 Eu3+-AHA complex as 1.42 ± 0.64 under the conditions of this study. By contrast, the Tb(III)-AHA system at pH 3 (HNO3) did not show any significant variation in the life times of the excited state (364 ± 9 μs) suggesting the absence of dynamic quenching. The spectral changes in Tb(III)-AHA system showed the formation of 1:1 complex (log K: 1.72 ± 0.21). These studies suggest that the extent of AHA complexation with the rare earth elements will be insignificant as compared to tetravalent metal ions Pu(IV) and Np(IV) under UREX process conditions.

  7. Docosahexaenoic acid conjugated near infrared flourescence probe for in vivo early tumor diagnosis

    NASA Astrophysics Data System (ADS)

    Li, Siwen; Cao, Jie; Qin, Jingyi; Zhang, Xin; Achilefu, Samuel; Qian, Zhiyu; Gu, Yueqing

    2013-02-01

    Docosahexaenoic acid(DHA) is an omega-3 C22 natural fatty acid with six cis double bonds and as a constituent of membranes used as a precursor for metabolic and biochemical path ways. In this manuscript,we describe the synthesis of near-infrared(NIR) flourescence ICG-Der-01 labeled DHA for in vitro and vivo tumor targeting.The structure of the probe was intensively characterized by UV and MS. The in vitro and vivo tumor targeting abilities of the DHA-based NIR probes were investigeted in MCF-7 cells and MCF-7 xenograft mice model differently by confocal microscopy and CCD camera. The cell cytotoxicity were tested in tumor cells MCF-7 .The results shows that the DHA-based NIR probes have high affinity with the tumor both in vitro and vivo.In addition ,we also found that the DHA-based NIR probes have the apparent cytotoxicity on MCF-7 cells .which demonstrated that DHA was conjugated with other antitumor drug could increase the abilities of antirumor efficacy .So DHA-ICG-Der-01 is a promising optical agent for diagnosis of tumors especially in their early stage.

  8. Influence of acidic pH on the formulation of TiO2 nanocrystalline powders with enhanced photoluminescence property.

    PubMed

    Tsega, Moges; Dejene, F B

    2017-02-01

    Titanium dioxide (TiO2) nanoparticles were prepared by the sol-gel method at different pH values (3.2-6.8) with a hydrochloric acid (HCl) solution. Raw samples were calcined at 500 °C for 2 h. The effects of pH on the structural, morphological and optical properties of TiO2 nanoparticles were investigated. At pH 4.4-6.8, only the anatase phase of TiO2 was observed. Under strong acidic condition at pH 3.2 rutile, brookite and anatase co-exist, but rutile is the predominant phase. The strain value increased and the crystallite size decreased as the HCl content increased. The increased crystallite sizes in the range 21-24 nm and enhanced blue emission intensity around 432 nm was obtained for the sample at pH 5.0. Experimental results showed that TiO2 nanoparticles synthesized at pH 5.0 exhibited the best luminescence property with pure anatase phase.

  9. Silver ions-mediated conformational switch: facile design of structure-controllable nucleic acid probes.

    PubMed

    Wang, Yongxiang; Li, Jishan; Wang, Hao; Jin, Jianyu; Liu, Jinhua; Wang, Kemin; Tan, Weihong; Yang, Ronghua

    2010-08-01

    Conformationally constraint nucleic acid probes were usually designed by forming an intramolecular duplex based on Watson-Crick hydrogen bonds. The disadvantages of these approaches are the inflexibility and instability in complex environment of the Watson-Crick-based duplex. We report that this hydrogen bonding pattern can be replaced by metal-ligation between specific metal ions and the natural bases. To demonstrate the feasibility of this principle, two linear oligonucleotides and silver ions were examined as models for DNA hybridization assay and adenosine triphosphate detection. The both nucleic acids contain target binding sequences in the middle and cytosine (C)-rich sequences at the lateral portions. The strong interaction between Ag(+) ions and cytosines forms stable C-Ag(+)-C structures, which promises the oligonucleotides to form conformationally constraint formations. In the presence of its target, interaction between the loop sequences and the target unfolds the C-Ag(+)-C structures, and the corresponding probes unfolding can be detected by a change in their fluorescence emission. We discuss the thermodynamic and kinetic opportunities that are provided by using Ag(+) ion complexes instead of traditional Watson-Crick-based duplex. In particular, the intrinsic feature of the metal-ligation motif facilitates the design of functional nucleic acids probes by independently varying the concentration of Ag(+) ions in the medium.

  10. Cd(II)-coordination polymers based on tetracarboxylic acid and diverse bis(imidazole) ligands: Synthesis, structural diversity and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Arıcı, Mürsel; Yeşilel, Okan Zafer; Taş, Murat

    2017-01-01

    Three new Cd(II)-coordination polymers, namely, {[Cd2(μ6-ao2btc)(μ-1,5-bipe)2]·2H2O}n (1), {[Cd2(μ6-ao2btc)(μ-1,4-bix)2]n·2DMF} (2) and {[Cd2(μ8-abtc)(μ-1,4-betix)]·DMF·H2O}n (3) (ao2btc=di-oxygenated form of 3,3‧,5,5‧-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-1yl)pentane, 1,4-bix=1,4-bis(imidazol-1ylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-1ylmethyl)benzene) were synthesized with 3,3‧,5,5‧-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1-3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the rare sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd2(CO2)4-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed.

  11. Synthesis and photoluminescence properties of silver(I) complexes based on N-benzoyl-L-glutamic acid and N-donor ligands with different flexibility

    NASA Astrophysics Data System (ADS)

    Yan, Ming-Jie; Feng, Qi; Song, Hui-Hua

    2016-05-01

    By changing the N-donor ancillary ligand, three novel silver (I) complexes {[Ag(HbzgluO) (4,4‧-bipy)]·H2O}n (1), {[Ag2(HbzgluO)2 (bpe)2]·2H2O}n (2) and {[Ag(HbzgluO)(bpp)]·2H2O}n (3) (H2bzgluO = N-benzoyl-L-glutamic acid, 4,4‧-bipy = 4,4ˊ-bipyridine, bpe = 1,2-di(4-pyridyl)ethane, bpp = 1,3-di(4-pyridyl)propane) were synthesized. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). In this study, the N-donor ligands are changed from rigidity (4,4‧-bipy), quasi-flexibility (bpe) to flexibility (bpp), the structures of complexes also change. Complex 1 features a 1D chain structure which is further linked together to construct a 2D supramolecular structure through hydrogen bonds. Complex 2 is a 1D double-chains configuration which eventually forms a 3D supramolecular network via hydrogen bonding interactions. Whereas, complex 3 exhibits a 2D pleated grid structure which is linked by hydrogen bonding interactions into a 3D supramolecular network. The present observations demonstrate that the modulation of coordination polymers with different structures can accomplish by changing the spacer length of N-donor ligands. In addition, the solid-state circular dichroism (CD) spectra indicated that compound 2 exhibited negative cotton effect which originated from the chiral ligands H2bzgluO and the solid-state fluorescence spectra of the three complexes demonstrated the auxiliary ligands have influence on the photoluminescence properties of the complexes.

  12. Repeat sequence chromosome specific nucleic acid probes and methods of preparing and using

    DOEpatents

    Weier, Heinz-Ulrich G.; Gray, Joe W.

    1995-01-01

    A primer directed DNA amplification method to isolate efficiently chromosome-specific repeated DNA wherein degenerate oligonucleotide primers are used is disclosed. The probes produced are a heterogeneous mixture that can be used with blocking DNA as a chromosome-specific staining reagent, and/or the elements of the mixture can be screened for high specificity, size and/or high degree of repetition among other parameters. The degenerate primers are sets of primers that vary in sequence but are substantially complementary to highly repeated nucleic acid sequences, preferably clustered within the template DNA, for example, pericentromeric alpha satellite repeat sequences. The template DNA is preferably chromosome-specific. Exemplary primers ard probes are disclosed. The probes of this invention can be used to determine the number of chromosomes of a specific type in metaphase spreads, in germ line and/or somatic cell interphase nuclei, micronuclei and/or in tissue sections. Also provided is a method to select arbitrarily repeat sequence probes that can be screened for chromosome-specificity.

  13. Repeat sequence chromosome specific nucleic acid probes and methods of preparing and using

    DOEpatents

    Weier, H.U.G.; Gray, J.W.

    1995-06-27

    A primer directed DNA amplification method to isolate efficiently chromosome-specific repeated DNA wherein degenerate oligonucleotide primers are used is disclosed. The probes produced are a heterogeneous mixture that can be used with blocking DNA as a chromosome-specific staining reagent, and/or the elements of the mixture can be screened for high specificity, size and/or high degree of repetition among other parameters. The degenerate primers are sets of primers that vary in sequence but are substantially complementary to highly repeated nucleic acid sequences, preferably clustered within the template DNA, for example, pericentromeric alpha satellite repeat sequences. The template DNA is preferably chromosome-specific. Exemplary primers and probes are disclosed. The probes of this invention can be used to determine the number of chromosomes of a specific type in metaphase spreads, in germ line and/or somatic cell interphase nuclei, micronuclei and/or in tissue sections. Also provided is a method to select arbitrarily repeat sequence probes that can be screened for chromosome-specificity. 18 figs.

  14. Efficacy of Nucleic Acid Probes for Detection of Poliovirus in Water Disinfected by Chlorine, Chlorine Dioxide, Ozone, and UV Radiation

    PubMed Central

    Moore, Norman J.; Margolin, Aaron B.

    1994-01-01

    MilliQ water was inoculated with poliovirus type 1 strain LSc-1 and was treated with disinfectants, including chlorine, chlorine dioxide, ozone, and UV light. No relationship between probes and plaque assays were seen, demonstrating that viral nucleic acids were not destroyed. These findings suggest that nucleic acid probes cannot distinguish between infectious and noninfectious viruses and cannot be used in the evaluation of treated waters. PMID:16349448

  15. Intrinsically Labeled Fluorescent Oligonucleotide Probes on Quantum Dots for Transduction of Nucleic Acid Hybridization.

    PubMed

    Shahmuradyan, Anna; Krull, Ulrich J

    2016-03-15

    Quantum dots (QDs) have been widely used in chemical and biosensing due to their unique photoelectrical properties and are well suited as donors in fluorescence resonance energy transfer (FRET). Selective hybridization interactions of oligonucleotides on QDs have been determined by FRET. Typically, the QD-FRET constructs have made use of labeled targets or have implemented labeled sandwich format assays to introduce dyes in proximity to the QDs for the FRET process. The intention of this new work is to explore a method to incorporate the acceptor dye into the probe molecule. Thiazole orange (TO) derivatives are fluorescent intercalating dyes that have been used for detection of double-stranded nucleic acids. One such dye system has been reported in which single-stranded oligonucleotide probes were doubly labeled with adjacent thiazole orange derivatives. In the absence of the fully complementary (FC) oligonucleotide target, the dyes form an H-aggregate, which results in quenching of fluorescence emission due to excitonic interactions between the dyes. The hybridization of the FC target to the probe provides for dissociation of the aggregate as the dyes intercalate into the double stranded duplex, resulting in increased fluorescence. This work reports investigation of the dependence of the ratiometric signal on the type of linkage used to conjugate the dyes to the probe, the location of the dye along the length of the probe, and the distance between adjacent dye molecules. The limit of detection for 34mer and 90mer targets was found to be identical and was 10 nM (2 pmol), similar to analogous QD-FRET using labeled oligonucleotide target. The detection system could discriminate a one base pair mismatch (1BPM) target and was functional without substantial compromise of the signal in 75% serum. The 1BPM was found to reduce background signal, indicating that the structure of the mismatch affected the environment of the intercalating dyes.

  16. Structural, electronic and photoluminescence properties of Eu3+-doped CaYAlO4 obtained by using citric acid complexes as precursors

    NASA Astrophysics Data System (ADS)

    Perrella, R. V.; Júnior, C. S. Nascimento; Góes, M. S.; Pecoraro, E.; Schiavon, M. A.; Paiva-Santos, C. O.; Lima, H.; Couto dos Santos, M. A.; Ribeiro, S. J. L.; Ferrari, J. L.

    2016-07-01

    The search for new materials that meet the current technological demands for photonic applications, make the Rare Earth ions embedded in inorganic oxides as excellent candidates for several technological devices. This work presents the synthesis of Eu3+-doped CaYAlO4 using citric acid as ligand to form a complex precursor. The methodology used has big draw due to its easy handling and low cost of the materials. The thermal analysis of viscous solutions was evaluated and the obtained compounds show the formation of a polycrystalline tetragonal phase. Rietveld refinement was used to understand the structural and the cell parameters of the crystalline phase as a function of temperature of heat-treatment. Crystallite size and microstrain were determined and were shown to have a direct relationship with the temperature of the heat-treatment. The band-gap of the CaYAlO4 doped with 1 and 10 mol% of Eu3+ showed values close to 4.30 eV, resulting in their transparency in the visible region between 330 and 750 nm. Besides the intense photoluminescence from Eu3+, a study was conducted to evaluate the possible position of the Eu3+ in the CaYAlO4 as host lattice. Lifetime of the emission decay from Eu3+ excited state 5D0 show that CaYAlO4 is a good host to rare earth ions, once it can avoid clustering of these ions in concentration as high as 10 mol%. The predictions of the sublevels of the 7F1 crystal field level are discussed through the method of equivalent nearest neighbours (MENN). The intensity parameters (Ωλ, λ = 2 and 4) are reproduced with physically reasonable values of average polarizabilities. The set of charge factors used in both calculations are in good agreement with the charge of the europium ion described by the Batista-Longo improved model (BLIM). The quantum efficiencies of the materials were calculated based on Judd-Ofelt theory. Based on the results obtained in this work, the materials have potential use in photonic devices such as lasers and solid

  17. Photoluminescence lineshape of ZnO

    NASA Astrophysics Data System (ADS)

    Ullrich, Bruno; Singh, Akhilesh K.; Bhowmick, Mithun; Barik, Puspendu; Ariza-Flores, David; Xi, Haowen; Tomm, Jens W.

    2014-12-01

    The merger of the absorption coefficient dispersion, retrieved from transmission by the modified Urbach rule introduced by Ullrich and Bouchenaki [Jpn. J. Appl. Phys. 30, L1285, 1991], with the extended Roosbroeck-Shockley relation reveals that the optical absorption in ZnO distinctively determines the photoluminescence lineshape. Additionally, the ab initio principles employed enable the accurate determination of the carrier lifetime without further specific probing techniques.

  18. Probing the interactions between boronic acids and cis-diol-containing biomolecules by affinity capillary electrophoresis.

    PubMed

    Lü, Chenchen; Li, Hengye; Wang, Heye; Liu, Zhen

    2013-02-19

    The affinity of boronic acids to cis-diol-containing biomolecules has found wide applications in many fields, such as sensing, separation, drug delivery, and functional materials. A sound understanding of the binding interactions will greatly facilitate exquisite applications of this chemistry. Although a few analytical tools have been available for the characterization of the interactions, these techniques are associated with some apparent drawbacks, so they are only applicable to a limited range of boronic acids and cis-diol-containing biomolecules. Therefore, a widely applicable method is still greatly needed. In this work, an affinity capillary electrophoresis (ACE) method was established and validated to probe the interactions between boronic acids and cis-diol-containing biomolecules. The method was proven to be applicable to almost all types of cis-diol-containing biomolecules and boronic acids. Based on this method, a quantitative, comparative study on the interactions between 14 boronic acids that have important potentials for application with 5 typical monosaccharides of biological importance was carried out. The findings provided new insights into boronate affinity interactions, particularly the relationship between the binding strength with the molecular structures of the binding species. Besides, effects of pH and temperature on the binding strength were also investigated. This method exhibited several significant advantages, including (1) possibility of simultaneous study of multiple interactions, (2) low requirement on the purity of the binding species, (3) wide applicability, and (4) high accuracy and precision.

  19. Folic acid-conjugated europium complexes as luminescent probes for selective targeting of cancer cells.

    PubMed

    Quici, Silvio; Casoni, Alessandro; Foschi, Francesca; Armelao, Lidia; Bottaro, Gregorio; Seraglia, Roberta; Bolzati, Cristina; Salvarese, Nicola; Carpanese, Debora; Rosato, Antonio

    2015-02-26

    We report the synthesis of three optical probes (Eu(3+)⊂1, Eu(3+)⊂2, and Eu(3+)⊂3) having a luminescent Eu complex (signaling unit) bonded in different positions to folic acid (FA), the folate receptor (FR) targeting unit. The structures of the two regioisomers Eu(3+)⊂1 and Eu(3+)⊂2 were assigned by mass spectrometric experiments. The optical properties and stability of these probes were assessed in phosphate-buffered saline, cell culture medium, rat serum, and cellular lysate, and results indicated that they are chemically and photophysically stable. Cytotoxicity was studied with ovarian cancer cells having high (SKOV-3), intermediate (OVCAR-3), low (IGROV-1), or null (A2780) expression of FRs. The internalized probe, evaluated in SKOV-3, IGROV-1, and A2780 cells, was in the order Eu(3+)⊂2 > Eu(3+)⊂1 > Eu(3+)⊂3. No internalization was observed for A2780 cells. Such results, together with those obtained in competition experiments of FA versus Eu(3+)⊂2 and FA or Eu(3+)⊂2 versus (3)H-FA, indicate that internalization is receptor-mediated and that Eu(3+)⊂2 shows high selectivity and specificity for FR.

  20. Human leukocyte antigen haplotype phasing by allele-specific enrichment with peptide nucleic acid probes

    PubMed Central

    Murphy, Nicholas M; Pouton, Colin W; Irving, Helen R

    2014-01-01

    Targeted capture of large fragments of genomic DNA that enrich for human leukocyte antigen (HLA) system haplotypes has utility in haematopoietic stem cell transplantation. Current methods of HLA matching are based on inference or familial studies of inheritance; and each approach has its own inherent limitations. We have designed and tested a probe–target-extraction method for capturing specific HLA haplotypes by hybridization of peptide nucleic acid (PNA) probes to alleles of the HLA-DRB1 gene. Short target fragments contained in plasmids were initially used to optimize the method followed by testing samples of genomic DNA from human subjects with preselected HLA haplotypes and obtained approximately 10% enrichment for the specific haplotype. When performed with high-molecular-weight genomic DNA, 99.0% versus 84.0% alignment match was obtained for the specific haplotype probed. The allele-specific target enrichment that we obtained can facilitate the elucidation of haplotypes between the 65 kb separating the HLA-DRB1 and the HLA-DQA1 genes, potentially spanning a total distance of at least 130 kb. Allele-specific target enrichment with PNA probes is a straightforward technique that has the capability to improve the resolution of DNA and whole genome sequencing technologies by allowing haplotyping of enriched DNA and crucially, retaining the DNA methylation profile. PMID:24936514

  1. Identification of random nucleic acid sequence aberrations using dual capture probes which hybridize to different chromosome regions

    DOEpatents

    Lucas, J.N.; Straume, T.; Bogen, K.T.

    1998-03-24

    A method is provided for detecting nucleic acid sequence aberrations using two immobilization steps. According to the method, a nucleic acid sequence aberration is detected by detecting nucleic acid sequences having both a first nucleic acid sequence type (e.g., from a first chromosome) and a second nucleic acid sequence type (e.g., from a second chromosome), the presence of the first and the second nucleic acid sequence type on the same nucleic acid sequence indicating the presence of a nucleic acid sequence aberration. In the method, immobilization of a first hybridization probe is used to isolate a first set of nucleic acids in the sample which contain the first nucleic acid sequence type. Immobilization of a second hybridization probe is then used to isolate a second set of nucleic acids from within the first set of nucleic acids which contain the second nucleic acid sequence type. The second set of nucleic acids are then detected, their presence indicating the presence of a nucleic acid sequence aberration. 14 figs.

  2. Identification of random nucleic acid sequence aberrations using dual capture probes which hybridize to different chromosome regions

    DOEpatents

    Lucas, Joe N.; Straume, Tore; Bogen, Kenneth T.

    1998-01-01

    A method is provided for detecting nucleic acid sequence aberrations using two immobilization steps. According to the method, a nucleic acid sequence aberration is detected by detecting nucleic acid sequences having both a first nucleic acid sequence type (e.g., from a first chromosome) and a second nucleic acid sequence type (e.g., from a second chromosome), the presence of the first and the second nucleic acid sequence type on the same nucleic acid sequence indicating the presence of a nucleic acid sequence aberration. In the method, immobilization of a first hybridization probe is used to isolate a first set of nucleic acids in the sample which contain the first nucleic acid sequence type. Immobilization of a second hybridization probe is then used to isolate a second set of nucleic acids from within the first set of nucleic acids which contain the second nucleic acid sequence type. The second set of nucleic acids are then detected, their presence indicating the presence of a nucleic acid sequence aberration.

  3. Fluorescence energy transfer as a probe for nucleic acid structures and sequences.

    PubMed Central

    Mergny, J L; Boutorine, A S; Garestier, T; Belloc, F; Rougée, M; Bulychev, N V; Koshkin, A A; Bourson, J; Lebedev, A V; Valeur, B

    1994-01-01

    The primary or secondary structure of single-stranded nucleic acids has been investigated with fluorescent oligonucleotides, i.e., oligonucleotides covalently linked to a fluorescent dye. Five different chromophores were used: 2-methoxy-6-chloro-9-amino-acridine, coumarin 500, fluorescein, rhodamine and ethidium. The chemical synthesis of derivatized oligonucleotides is described. Hybridization of two fluorescent oligonucleotides to adjacent nucleic acid sequences led to fluorescence excitation energy transfer between the donor and the acceptor dyes. This phenomenon was used to probe primary and secondary structures of DNA fragments and the orientation of oligodeoxynucleotides synthesized with the alpha-anomers of nucleoside units. Fluorescence energy transfer can be used to reveal the formation of hairpin structures and the translocation of genes between two chromosomes. PMID:8152922

  4. Translational and rotational diffusion of flexible PEG and rigid dendrimer probes in sodium caseinate dispersions and acid gels.

    PubMed

    Salami, Souad; Rondeau-Mouro, Corinne; Barhoum, Myriam; van Duynhoven, John; Mariette, François

    2014-09-01

    The dynamics of rigid dendrimer and flexible PEG probes in sodium caseinate dispersions and acid gels, including both translational diffusion and rotational diffusion, were studied by NMR. Above the onset of the close-packing limit (C ∼ 10 g/100 g H2 O), translational diffusion of the probe depended on its flexibility and on the fluctuations of the matrix chains. The PEG probe diffused more rapidly than the spherical dendrimer probe of corresponding hydrodynamic radius. The greater conformational flexibility of PEG facilitated its motion through the crowded casein matrix. Rotational diffusion was, however, substantially less hindered than the translational diffusion and depended on the local protein-probe friction which became high when the casein concentration increased. The coagulation of the matrix led to the formation of large voids, which resulted in an increase in the translational diffusion of the probes, whereas the rotational diffusion of the probes was retarded in the gel, which could be attributed to the immobilized environment surrounding the probe. Quantitative information from PFG-NMR and SEM micrographs have been combined for characterizing microstructural details in SC acid gels.

  5. Boronic Acid: A Bio-Inspired Strategy To Increase the Sensitivity and Selectivity of Fluorescent NADH Probe.

    PubMed

    Wang, Lu; Zhang, Jingye; Kim, Beomsue; Peng, Juanjuan; Berry, Stuart N; Ni, Yong; Su, Dongdong; Lee, Jungyeol; Yuan, Lin; Chang, Young-Tae

    2016-08-24

    Fluorescent probes have emerged as an essential tool in the molecular recognition events in biological systems; however, due to the complex structures of certain biomolecules, it remains a challenge to design small-molecule fluorescent probes with high sensitivity and selectivity. Inspired by the enzyme-catalyzed reaction between biomolecule and probe, we present a novel combination-reaction two-step sensing strategy to improve sensitivity and selectivity. Based on this strategy, we successfully prepared a turn-on fluorescent reduced nicotinamide adenine dinucleotide (NADH) probe, in which boronic acid was introduced to bind with NADH and subsequently accelerate the sensing process. This probe shows remarkably improved sensitivity (detection limit: 0.084 μM) and selectivity to NADH in the absence of any enzymes. In order to improve the practicality, the boronic acid was further modified to change the measurement conditions from alkalescent (pH 9.5) to physiological environment (pH 7.4). Utilizing these probes, we not only accurately quantified the NADH weight in a health care product but also evaluated intracellular NADH levels in live cell imaging. Thus, these bio-inspired fluorescent probes offer excellent tools for elucidating the roles of NADH in biological systems as well as a practical strategy to develop future sensitive and selective probes for complicated biomolecules.

  6. Selective local lysis and sampling of live cells for nucleic acid analysis using a microfluidic probe

    PubMed Central

    Kashyap, Aditya; Autebert, Julien; Delamarche, Emmanuel; Kaigala, Govind V.

    2016-01-01

    Heterogeneity is inherent to biology, thus it is imperative to realize methods capable of obtaining spatially-resolved genomic and transcriptomic profiles of heterogeneous biological samples. Here, we present a new method for local lysis of live adherent cells for nucleic acid analyses. This method addresses bottlenecks in current approaches, such as dilution of analytes, one-sample-one-test, and incompatibility to adherent cells. We make use of a scanning probe technology - a microfluidic probe - and implement hierarchical hydrodynamic flow confinement (hHFC) to localize multiple biochemicals on a biological substrate in a non-contact, non-destructive manner. hHFC enables rapid recovery of nucleic acids by coupling cell lysis and lysate collection. We locally lysed ~300 cells with chemical systems adapted for DNA or RNA and obtained lysates of ~70 cells/μL for DNA analysis and ~15 cells/μL for mRNA analysis. The lysates were introduced into PCR-based workflows for genomic and transcriptomic analysis. This strategy further enabled selective local lysis of subpopulations in a co-culture of MCF7 and MDA-MB-231 cells, validated by characteristic E-cadherin gene expression in individually extracted cell types. The developed strategy can be applied to study cell-cell, cell-matrix interactions locally, with implications in understanding growth, progression and drug response of a tumor. PMID:27411740

  7. Exploring 12'-apo-beta-carotenoic-12'-acid as an ultrafast polarity probe for ionic liquids.

    PubMed

    Lohse, Peter W; Bürsing, Reinhard; Lenzer, Thomas; Oum, Kawon

    2008-03-13

    The ultrafast excited-state dynamics of the carbonyl-containing carotenoid 12'-apo-beta-carotenoic-12'-acid (12'CA) have been used for probing the microscopic environment in various ionic liquids (ILs). The following IL cations were investigated: 1,3-di-n-alkyl-imidazolium featuring different n-alkyl chain lengths and also additional methylation at the C2 position, triethylsulfonium, as well as two tetraalkylammonium ions. These were combined with different anions: [BF4]-, [PF6]-, ethyl sulfate ([EtOSO3]-), and bis(trifluoromethylsulfonyl)amide ([Tf2N]-). The probe molecule was excited via the S0 --> S2 transition at 425 or 430 nm, and the characteristic stimulated emission decay of the low-lying excited electronic S1/ICT (intramolecular charge transfer) state of 12'CA was monitored in the near IR (850 or 860 nm). Its lifetime tau1 is sensitive to the micropolarity-induced stabilization of S1/ICT relative to S0. The lifetime tau1 of the S1/ICT state varies only moderately in all ionic liquids studied here ( approximately 40-110 ps), which lies in the range between ethanol (109 ps) and methanol (49 ps). While organic solvents show an excellent correlation of tau1 with the solvent polarity function Deltaf = (epsilon - 1)/(epsilon + 2) - (n2 - 1)/(n2 + 2), where epsilon and n are the static dielectric constant and the refractive index of the solvent, respectively, this is not the case for ILs. This is due to dominant local electrostatic probe-cation interactions which cannot be easily quantified by macroscopic quantities. Methylation at the C2 position of 1,3-di-n-alkyl-imidazolium reduces the accessibility of the cation and therefore the electrostatic stabilization of the probe, resulting in an increase of tau1. A similar increase is observed upon extension of one of the n-alkyl chains from ethyl to n-decyl. Tetraalkylammonium ILs show an increased tau1 probably due to their more delocalized positive charge which cannot interact so favorably with the probe, in

  8. Glycine-coated photoluminescent silver nanoclusters

    NASA Astrophysics Data System (ADS)

    Kravets, Vira V.; Culhane, Kyle; Dmitruk, Igor M.; Pinchuk, Anatoliy O.

    2012-03-01

    We present experimental results on the multicolor (blue and green) photoluminescence from glycine-coated silver nanoclusters and small nanoparticles which can be used as novel probes for bio-imaging. Glycine-coated silver nanoclusters and nanoparticles were synthesized using thermal reduction of silver nitrate in a glycine matrix, according to a modified procedure described in literature. The size characterization with mass spectrometry, scanning electron microscopy and dynamic light scattering showed that the diameters of luminescent silver nanoclusters and small nanoparticles vary from 0.5 nm to 17 nm. Extinction spectroscopy revealed that the absorption band of the luminescent nanoclusters and nanoparticles was blue-shifted as compared to the nonluminescent larger silver nanoparticles. This effect indicated the well-known size dependence of the surface plasmon resonance in silver. The most pronounced photoluminescence peak was observed around 410 nm (characteristic SPR wavelength for silver) which strongly suggests the enhancement of the photoluminescence from silver nanoparticles by the SPR. The relative quantum yield of the photoluminescence of silver nanoclusters and nanoparticles was evaluated to be 0.09. In terms of their small size, brightness and photostability, noble metal nanoclusters and nanoparticles hold the most promise as candidates for biological cell imaging, competing with commonly used semiconductor quantum dots, fluorescent proteins and organic dyes. When applied to the problem of intracellular imaging, metal nanoclusters and small nanoparticles offer advantages over their much larger sized semiconductor counterparts in terms of ease of biological delivery. In addition, noble metal nanoparticles and nanoclusters are photostable. The high quantum yield (QY) of the photoluminescence emission signal enables the isolation of their photoluminescence from the cellular autofluorescence in cell imaging, improving the image contrast.

  9. Complexation of malic acid with cadmium(II) probed by electrospray ionization mass spectrometry.

    PubMed

    Jaklová Dytrtová, Jana; Jakl, Michal; Schröder, Detlef

    2012-02-15

    Electrospray ionization was used as a technique for the characterization of the interactions between cadmium(II) ions and malic acid (1) in aqueous solution. Particular attention was paid to the nature of the species formed, which generally correspond to complexes of CdX(+) cations with neutral malic acid, where X either is the counterion of the metal salt used as a precursor (i.e. X=Cl, I) or corresponds to singly deprotonated malic acid. In pure water solutions, also highly coordinated complexes [Cd(1-H)(1)(2)](+) and [CdCl(1)(2)](+) were detected, whereas the most abundant complexes detected in a sample of soil solution were: [Cd(1-H)(1)](+) and [CdCl(1)](+). With respect to possible application in environmental analysis, the effects of (i) metal salts present in solution, (ii) modest mineralization, and (iii) the matrices of real soil solutions were probed. While the presence of other metals leads to additional complexes, the characteristic species containing both cadmium(II) and malic acid can still be detected with good sensitivity.

  10. Phylogenetic group- and species-specific oligonucleotide probes for single-cell detection of lactic acid bacteria in oral biofilms

    PubMed Central

    2011-01-01

    Background The purpose of this study was to design and evaluate fluorescent in situ hybridization (FISH) probes for the single-cell detection and enumeration of lactic acid bacteria, in particular organisms belonging to the major phylogenetic groups and species of oral lactobacilli and to Abiotrophia/Granulicatella. Results As lactobacilli are known for notorious resistance to probe penetration, probe-specific assay protocols were experimentally developed to provide maximum cell wall permeability, probe accessibility, hybridization stringency, and fluorescence intensity. The new assays were then applied in a pilot study to three biofilm samples harvested from variably demineralized bovine enamel discs that had been carried in situ for 10 days by different volunteers. Best probe penetration and fluorescent labeling of reference strains were obtained after combined lysozyme and achromopeptidase treatment followed by exposure to lipase. Hybridization stringency had to be established strictly for each probe. Thereafter all probes showed the expected specificity with reference strains and labeled the anticipated morphotypes in dental plaques. Applied to in situ grown biofilms the set of probes detected only Lactobacillus fermentum and bacteria of the Lactobacillus casei group. The most cariogenic biofilm contained two orders of magnitude higher L. fermentum cell numbers than the other biofilms. Abiotrophia/Granulicatella and streptococci from the mitis group were found in all samples at high levels, whereas Streptococcus mutans was detected in only one sample in very low numbers. Conclusions Application of these new group- and species-specific FISH probes to oral biofilm-forming lactic acid bacteria will allow a clearer understanding of the supragingival biome, its spatial architecture and of structure-function relationships implicated during plaque homeostasis and caries development. The probes should prove of value far beyond the field of oral microbiology, as many of

  11. Identification of Dekkera bruxellensis (Brettanomyces) from Wine by Fluorescence In Situ Hybridization Using Peptide Nucleic Acid Probes

    PubMed Central

    Stender, Henrik; Kurtzman, Cletus; Hyldig-Nielsen, Jens J.; Sørensen, Ditte; Broomer, Adam; Oliveira, Kenneth; Perry-O'Keefe, Heather; Sage, Andrew; Young, Barbara; Coull, James

    2001-01-01

    A new fluorescence in situ hybridization method using peptide nucleic acid (PNA) probes for identification of Brettanomyces is described. The test is based on fluorescein-labeled PNA probes targeting a species-specific sequence of the rRNA of Dekkera bruxellensis. The PNA probes were applied to smears of colonies, and results were interpreted by fluorescence microscopy. The results obtained from testing 127 different yeast strains, including 78 Brettanomyces isolates from wine, show that the spoilage organism Brettanomyces belongs to the species D. bruxellensis and that the new method is able to identify Brettanomyces (D. bruxellensis) with 100% sensitivity and 100% specificity. PMID:11157265

  12. Photoluminescent conductor polymer holograms

    NASA Astrophysics Data System (ADS)

    Ruiz-Limón, B.; Olivares-Pérez, A.; Ponce-Lee, E. L.; Hernández-Garay, M. P.; Páez-Trujillo, G.; Fuentes-Tapia, I.

    2007-02-01

    An organic conductor polymer was doped with benzalkonium chloride to get a photoluminescent effect at 560 nm and it was used as holographic material. We used a digital image to generate a hologram in a computer and it was transferred by microlithography techniques to our polymer to get a phase hologram. The transference is successful by rubbing, the heat increment produce temperature gradients and the information in the mask is transferred to the material by the refraction index changes, thus the film is recorded. We recorded some gratings to observe the behavior of photoluminescent light with different frequencies when it is radiated with a green laser beam at 532 nm.

  13. Exploring the Hybridization Thermodynamics of Spherical Nucleic Acids to Tailor Probes for Diagnostic and Therapeutic Applications

    NASA Astrophysics Data System (ADS)

    Randeria, Pratik Shailesh

    Spherical nucleic acids (SNAs), three-dimensional nanoparticle conjugates composed of densely packed and highly oriented oligonucleotides around organic or inorganic nanoparticles, are an emergent class of nanostructures that show promise as single-entity agents for intracellular messenger RNA (mRNA) detection and gene regulation. SNAs exhibit superior biocompatibility and biological properties compared to linear oligonucleotides, enabling them to overcome many of the limitations of linear oligonucleotides for use in biomedical applications. However, the origins of these biologically attractive properties are not well understood. In this dissertation, the chemistry underlying one such property is studied in detail, and the findings are applied towards the rational design of more effective SNAs for diagnostic and therapeutic applications. Chapter 1 introduces the synthesis of SNAs, the unique properties that make them superior to linear nucleic acids for biomedicine, and previously studied applications of these structures. Chapter 2 focuses on quantitatively studying the impact of the chemical structure of the SNA on its ability to hybridize multiple complementary nucleic acids. This chapter lays the groundwork for understanding the factors that govern SNA hybridization thermodynamics and how to tailor SNAs to increase their binding affinity to target mRNA strands. Chapters 3 and 4 capitalize on this knowledge to engineer probes for intracellular mRNA detection and gene regulation applications. Chapter 3 reports the development of an SNA-based probe that can simultaneously report the expression level of two different mRNA transcripts in live cells and differentiate diseased cells from non-diseased cells. Chapter 4 investigates the use of topically-applied SNAs to down-regulate a critical mediator of impaired wound healing in diabetic mice to accelerate wound closure. This study represents the first topical therapeutic application of SNA nanotechnology to treat open

  14. Proteomic Stable Isotope Probing Reveals Taxonomically Distinct Patterns in Amino Acid Assimilation by Coastal Marine Bacterioplankton

    PubMed Central

    Bryson, Samuel; Li, Zhou; Pett-Ridge, Jennifer; Hettich, Robert L.; Mayali, Xavier; Pan, Chongle

    2016-01-01

    ABSTRACT Heterotrophic marine bacterioplankton are a critical component of the carbon cycle, processing nearly a quarter of annual primary production, yet defining how substrate utilization preferences and resource partitioning structure microbial communities remains a challenge. In this study, proteomic stable isotope probing (proteomic SIP) was used to characterize population-specific assimilation of dissolved free amino acids (DFAAs), a major source of dissolved organic carbon for bacterial secondary production in aquatic environments. Microcosms of seawater collected from Newport, Oregon, and Monterey Bay, California, were incubated with 1 µM 13C-labeled amino acids for 15 and 32 h. The taxonomic compositions of microcosm metaproteomes were highly similar to those of the sampled natural communities, with Rhodobacteriales, SAR11, and Flavobacteriales representing the dominant taxa. Analysis of 13C incorporation into protein biomass allowed for quantification of the isotopic enrichment of identified proteins and subsequent determination of differential amino acid assimilation patterns between specific bacterioplankton populations. Proteins associated with Rhodobacterales tended to have a significantly high frequency of 13C-enriched peptides, opposite the trend for Flavobacteriales and SAR11 proteins. Rhodobacterales proteins associated with amino acid transport and metabolism had an increased frequency of 13C-enriched spectra at time point 2. Alteromonadales proteins also had a significantly high frequency of 13C-enriched peptides, particularly within ribosomal proteins, demonstrating their rapid growth during incubations. Overall, proteomic SIP facilitated quantitative comparisons of DFAA assimilation by specific taxa, both between sympatric populations and between protein functional groups within discrete populations, allowing an unprecedented examination of population level metabolic responses to resource acquisition in complex microbial communities

  15. Proteomic Stable Isotope Probing Reveals Taxonomically Distinct Patterns in Amino Acid Assimilation by Coastal Marine Bacterioplankton.

    PubMed

    Bryson, Samuel; Li, Zhou; Pett-Ridge, Jennifer; Hettich, Robert L; Mayali, Xavier; Pan, Chongle; Mueller, Ryan S

    2016-01-01

    Heterotrophic marine bacterioplankton are a critical component of the carbon cycle, processing nearly a quarter of annual primary production, yet defining how substrate utilization preferences and resource partitioning structure microbial communities remains a challenge. In this study, proteomic stable isotope probing (proteomic SIP) was used to characterize population-specific assimilation of dissolved free amino acids (DFAAs), a major source of dissolved organic carbon for bacterial secondary production in aquatic environments. Microcosms of seawater collected from Newport, Oregon, and Monterey Bay, California, were incubated with 1 µM (13)C-labeled amino acids for 15 and 32 h. The taxonomic compositions of microcosm metaproteomes were highly similar to those of the sampled natural communities, with Rhodobacteriales, SAR11, and Flavobacteriales representing the dominant taxa. Analysis of (13)C incorporation into protein biomass allowed for quantification of the isotopic enrichment of identified proteins and subsequent determination of differential amino acid assimilation patterns between specific bacterioplankton populations. Proteins associated with Rhodobacterales tended to have a significantly high frequency of (13)C-enriched peptides, opposite the trend for Flavobacteriales and SAR11 proteins. Rhodobacterales proteins associated with amino acid transport and metabolism had an increased frequency of (13)C-enriched spectra at time point 2. Alteromonadales proteins also had a significantly high frequency of (13)C-enriched peptides, particularly within ribosomal proteins, demonstrating their rapid growth during incubations. Overall, proteomic SIP facilitated quantitative comparisons of DFAA assimilation by specific taxa, both between sympatric populations and between protein functional groups within discrete populations, allowing an unprecedented examination of population level metabolic responses to resource acquisition in complex microbial communities

  16. Probing titanate nanowire surface acidity through methylene blue adsorption in colloidal suspension and on thin films.

    PubMed

    Horváth, Endre; Szilágyi, István; Forró, László; Magrez, Arnaud

    2014-02-15

    The interaction of the cationic dye methylene blue (MB) with titanate nanowires (TiONWs) was investigated in different pH environments using visible spectroscopy and electrophoresis on thin films as well as in aqueous suspension. The surface charge of the TiONWs depends on the pH and ionic strength leading to positive charge under acidic and negative under alkaline conditions. The TiONWs have the same adsorption capacity on films and in suspensions at neutral pH while under alkaline conditions they are able to adsorb significantly more MB in suspension due to their higher surface area. Detailed adsorption studies in water revealed that dye cations form monomers, dimers and larger aggregates of H-type (face-to-face) on the TiONW films. The results indicate that below pH = 4.0 the TiONWs' external surface consists of Brøntsted acid sites capable of protonating MB. It was suggested that reversible indicator role of MB molecule dimers probes the TiONW surface acidity (Brøntsted sites).

  17. Location and binding mechanism of an ESIPT probe 3-hydroxy-2-naphthoic acid in unsaturated fatty acid bound serum albumins.

    PubMed

    Ghorai, Shyamal Kr; Tripathy, Debi Ranjan; Dasgupta, Swagata; Ghosh, Sanjib

    2014-02-05

    The binding site and the binding mechanism of 3-hydroxy-2-naphthoic acid (3HNA) in oleic acid (OA) bound serum albumins (bovine serum albumin (BSA) and human serum albumin (HSA)) have been determined using steady state and time resolved emission of tryptophan residues (Trp) in proteins and the ESIPT emission of 3HNA. Time resolved anisotropy of the probe 3HNA and low temperature phosphorescence of Trp residues of BSA in OA bound BSA at 77K reveals a drastic change of the binding site of 3HNA in the ternary system compared to that in the free protein. 3HNA binds near Trp213 in the ternary system whereas 3HNA binds near Trp134 in the free protein. The structure of OA bound BSA generated using docking methodology exhibits U-bend configuration of all bound OA. The docked pose of 3HNA in the free protein and in OA bound albumins (ternary systems) and the concomitant perturbation of the structure of proteins around the binding region of 3HNA corroborate the enhanced ESIPT emission of 3HNA and the energy transfer efficiency from the donor Trp213 of BSA to 3HNA acceptor in 3HNA-OA-BSA system.

  18. Neutrophil chemotaxis and arachidonic acid metabolism are not linked: evidence from metal ion probe studies

    SciTech Connect

    Turner, S.R.; Turner, R.A.; Smith, D.M.; Johnson, J.A.

    1986-03-05

    Heavy metal ions can inhibit arachidonic acid (AA) metabolism protect against ionophore cytotoxicity (ibid) and inhibit neutrophil chemotaxis. In this study they used Au/sup 3 +/, Zn/sup 2 +/, Cr/sup 3 +/, Mn/sup 2 +/ and Cu/sup 2 +/ as probes of the interrelationships among AA metabolism, ionophore-mediated cytotoxicity, and chemotaxis. Phospholipid deacylation was measured in ionophore-treated cells prelabeled with /sup 3/H-AA. Eicosanoid release from ionophore-treated cells was monitored by radioimmunoassay. Cytoprotection was quantitated as ability to exclude trypan blue. Chemotaxis toward f-met-leu-phe was measured by leading front analysis. The results imply that metal ions attenuate ionophore cytotoxicity by blocking phospholipid deacylation and eicosanoid release. In contrast to previous reports, no correlation between AA metabolism and chemotaxis was demonstrated, suggesting that these 2 processes are not linked.

  19. An Activity-Based Probe for N-Acylethanolamine Acid Amidase

    PubMed Central

    Armirotti, Andrea; Summa, Maria; Bertozzi, Fabio; Garau, Gianpiero; Bandiera, Tiziano; Piomelli, Daniele

    2015-01-01

    N-Acylethanolamine acid amidase (NAAA) is a lysosomal cysteine hydrolase involved in the degradation of saturated and monounsaturated fatty acid ethanolamides (FAEs), a family of endogenous lipid signaling molecules that includes oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). Among the reported NAAA inhibitors, α–amino–β–lactone (3–aminooxetan–2–one) derivatives have been shown to prevent FAE hydrolysis in innate-immune and neural cells and to reduce reactions to inflammatory stimuli. Recently, we disclosed two potent and selective NAAA inhibitors, the compounds ARN077 (5-phenylpentyl N-[(2S,3R)-2-methyl-4-oxo-oxetan-3-yl]carbamate) and ARN726 (4-cyclohexylbutyl-N-[(S)-2-oxoazetidin-3-yl]carbamate). The former is active in vivo by topical administration in rodent models of hyperalgesia and allodynia, while the latter exerts systemic anti-inflammatory effects in mouse models of lung inflammation. In the present study, we designed and validated a derivative of ARN726 as the first activity-based protein profiling (ABPP) probe for the in vivo detection of NAAA. The newly synthesized molecule 1 is an effective in vitro and in vivo click-chemistry activity based probe (ABP), which is able to capture the catalytically active form of NAAA in Human Embryonic Kidney 293 (HEK293) cells overexpressing human NAAA as well as in rat lung tissue. Competitive ABPP with 1 confirmed that ARN726 and ARN077 inhibit NAAA in vitro and in vivo. Compound 1 is a useful new tool to identify activated NAAA both in vitro and in vivo, and to investigate the physiological and pathological roles of this enzyme. PMID:26102511

  20. Amperometric microsensor for direct probing of ascorbic acid in human gastric juice.

    PubMed

    Hutton, Emily A; Pauliukaitė, Rasa; Hocevar, Samo B; Ogorevc, Božidar; Smyth, Malcolm R

    2010-09-30

    This article reports on a novel microsensor for amperometric measurement of ascorbic acid (AA) under acidic conditions (pH 2) based on a carbon fiber microelectrode (CFME) modified with nickel oxide and ruthenium hexacyanoferrate (NiO-RuHCF). This sensing layer was deposited electrochemically in a two-step procedure involving an initial galvanostatic NiO deposition followed by a potentiodynamic RuHCF deposition from solutions containing the precursor salts. Several important parameters were examined to characterize and optimize the NiO-RuHCF sensing layer with respect to its current response to AA by using cyclic voltammetry, and scanning electron microscopy-energy dispersive X-ray spectroscopy methods. With the NiO-RuHCF coated CFME, the AA oxidation potential under acidic conditions was shifted to a less positive value for about 0.2 V (E(p) of ca. 0.23 V vs. Ag/AgCl) as compared to a bare CFME, which greatly improves the electrochemical selectivity. Using the hydrodynamic amperometry mode, the current vs. AA concentration in 0.01 M HCl, at a selected operating potential of 0.30 V, was found to be linear over a wide range of 10-1610 μM (n=22, r=0.999) with a calculated limit of detection of 1.0 μM. The measurement repeatability was satisfactory with a relative standard deviation (r.s.d.) ranging from 4% to 5% (n=6), depending on the AA concentration, and with a sensor-to-sensor reproducibility (r.s.d.) of 6.9% at 100 μM AA. The long-term reproducibility, using the same microsensor for 112 consecutive measurements of 20 μM AA over 11 h of periodic probing sets over 4 days, was 16.1% r.s.d., thus showing very good stability at low AA levels and suitability for use over a prolonged period of time. Moreover, using the proposed microsensor, additionally coated with a protective cellulose acetate membrane, the calibration plot obtained in the extremely complex matrix of real undiluted gastric juice was linear from 10 to 520 μM (n=14, r=0.998). These results

  1. New fluorescent octadecapentaenoic acids as probes of lipid membranes and protein-lipid interactions.

    PubMed Central

    Mateo, C R; Souto, A A; Amat-Guerri, F; Acuña, A U

    1996-01-01

    The chemical and spectroscopic properties of the new fluorescent acids all(E)-8, 10, 12, 14, 16-octadecapentaenoic acid (t-COPA) and its (8Z)-isomer (c-COPA) have been characterized in solvents of different polarity, synthetic lipid bilayers, and lipid/protein systems. These compounds are reasonably photostable in solution, present an intense UV absorption band (epsilon(350 nm) approximately 10(5) M(-1) cm(-1)) strongly overlapped by tryptophan fluorescence and their emission, centered at 470 nm, is strongly polarized (r(O) = 0.385 +/- 0.005) and decays with a major component (85%) of lifetime 23 ns and a faster minor one of lifetime 2 ns (D,L-alpha-dimyristoylphosphatidylcholine (DMPC), 15 degrees C). Both COPA isomers incorporate readily into vesicles and membranes (K(p) approximately 10(6)) and align parallel to the lipids. t-COPA distributes homogeneously between gel and fluid lipid domains and the changes in polarization accurately reflect the lipid T(m) values. From the decay of the fluorescence anisotropy in spherical bilayers of DMPC and POPC it is shown that t-COPA also correctly reflects the lipid order parameters, determined by 2H NMR techniques. Resonance energy transfer from tryptophan to the bound pentaenoic acid in serum albumin in solution, and from the tryptophan residues of gramicidin in lipid bilayers also containing the pentaenoic acid, show that this probe is a useful acceptor of protein tryptophan excitation, with R(O) values of 30-34 A. Images FIGURE 10 PMID:8889194

  2. A triterpene oleanolic acid conjugate with 3-hydroxyflavone derivative as a new membrane probe with two-color ratiometric response.

    PubMed

    Turkmen, Zeynep; Klymchenko, Andrey S; Oncul, Sule; Duportail, Guy; Topcu, Gulacti; Demchenko, Alexander P

    2005-07-29

    We report on the synthesis by coupling of a triterpenoid oleanolic acid with 4'-diethylamino-3-hydroxyflavone (FE) to produce an environment-sensitive biomembrane probe with two-band ratiometric response in fluorescence emission. The synthesized compound (probe FOT) was tested in a series of model solvents and demonstrated the response to solvent polarity and intermolecular hydrogen bonding very similar to that of parent probe FE. Meantime when incorporated into lipid bilayer membranes, it showed new features differing in response between lipids of different surface charges as well as between glycerophospholipids and sphingomyelin. We observed that in the conditions of coexistence of rafts and non-raft structures the probe is excluded from the rafts.

  3. Determination of bismuth in pharmaceutical products using phosphoric acid as molecular probe by resonance light scattering.

    PubMed

    Yun, Yanru; Cui, Fengling; Geng, Shaoguang; Jin, Jianhua

    2012-01-01

    A novel method for the sensitive determination of bismuth(III) in pharmaceutical products using phosphoric acid as a molecular probe by resonance light scattering (RLS) is discussed. In 0.5 mol/L phosphoric acid (H3 PO4) medium, bismuth(III) reacted with PO4 (3-) to form an ion association compound, which resulted in the significant enhancement of RLS intensity and the appearance of the corresponding RLS spectral characteristics. The maximum scattering peak of the system existed at 364 nm. Under optimal conditions, there was linear relationship between the relative intensity of RLS and concentration of bismuth(III) in the range of 0.06-10.0 µg/mL for the system. A low detection limit for bismuth(III) of 3.22 ng/mL was achieved. The relative standard deviations (RSD) for the determination of 0.40 and 0.80 µg/mL bismuth(III) were 2.1% and 1.1%, respectively, for five determinations. Based on this fact, a simple, rapid, and sensitive method was developed for the determination of bismuth(III) at nanogram level by RLS technique with a common spectrofluorimeter. This analytical system was successfully applied to determine the trace amounts of bismuth(III) in pharmaceutical products, which was in good agreement with the results obtained by atomic absorption spectrometry (AAS).

  4. Preparation and application of L-cysteine-modified CdSe/CdS core/shell nanocrystals as a novel fluorescence probe for detection of nucleic acid

    NASA Astrophysics Data System (ADS)

    Huang, Fenghua; Chen, Guonan

    2008-07-01

    The water-soluble L-cysteine-modified CdSe/CdS core/shell nanocrystals (expressed as CdSe/CdS/Cys nanocrystals) have been synthesized in aqueous by using L-cysteine as stabilizer. The size, shape, component and spectral property of CdSe/CdS/Cys nanocrystals were characterized by high-resolution transmission electron microscope (HRTEM), energy dispersive X-ray fluorescence (EDX), infrared spectrum (IR) and photoluminescence (PL). The results showed that the spherical CdSe/CdS/Cys nanocrystals with an average diameter of 2.3 nm have favorable fluorescent property, theirs photostability and fluorescence intensity are enhanced greatly after overcoating with CdS. The cysteine modified on the surface of core/shell CdSe/CdS nanocrystals renders the nanocrystals water-soluble and biocompatible. Based on the fluorescence quenching of the nanocrystals in the presence of calf thymus deoxyribonucleic acid (ct-DNA), a fluorescence quenching method has been developed for the determination of ct-DNA by using the nanocrystals as a novel fluorescence probe. The pH value of the system was selected at pH 7.4, with excitation and emission wavelength at 380 and 522 nm, respectively. Under the optimal conditions, the fluorescence quenching intensity of the system is linear with the concentration of ct-DNA in the range of 0.1-3.5 μg/mL ( r = 0.9987). The detection limit is 0.06 μg/mL. And two synthetic samples were analyzed satisfactorily.

  5. Alginic acid-based macromolecular chemiluminescent probe for universal protein assay on a solid-phase membrane.

    PubMed

    Krawczyk, Tomasz; Kondo, Midori; Azam, Md Golam; Zhang, Huan; Shibata, Takayuki; Kai, Masaaki

    2010-11-01

    A novel chemiluminescent (CL) technique for the rapid determination of proteins on a membrane is described. The method utilizes an interaction between luminol-labeled alginic acid macromolecule and proteins. The synthesis of the macromolecular probe consists of the oxidation of alginic acid with NaIO(4), the introduction of luminol through imine formation as a CL tag, and the reduction of the conjugate with NaBH(4) to obtain the stable probe. The analytical protocol consists of adsorbing proteins on a poly(vinylidene difluoride) (PVDF) membrane, incubating the membrane for 30 min with the probe solution in the presence of boric acid and a surfactant, two short washing steps in order to remove an excess of the probe, and detection of CL intensity with hemin, tetra-n-propylammonium hydroxide and H(2)O(2). This proposed CL assay for proteins can be finished within 1 h, and indicates the detection limit of 15-250 ng of proteins on the membrane. The CL signals in the calibration curves for some proteins such as albumin show proportional intensities against the amounts of the proteins less than ca. 125 ng, though there is a logarithmic relationship between the CL signals and the protein amounts larger than ca. 125 ng. However, some other proteins indicate the proportional CL intensities against the increasing amounts in wider range up to 500 ng of the proteins. The synthesised alginic acid-based probe indicates specific selectivity towards proteins, and should be used as a CL probe for the universal detection of various proteins on a solid-phase membrane even in the presence of DNA and RNA.

  6. Probe depth matters in dermal microdialysis sampling of benzoic acid after topical application: an ex vivo study in human skin.

    PubMed

    Holmgaard, R; Benfeldt, E; Bangsgaard, N; Sorensen, J A; Brosen, K; Nielsen, F; Nielsen, J B

    2012-01-01

    Microdialysis (MD) in the skin - dermal microdialysis (DMD) - is a unique technique for sampling of topically as well as systemically administered drugs at the site of action, e.g. sampling of dermatological drug concentrations in the dermis. Debate has concerned the existence of a correlation between the depth of the sampling device - the probe - in the dermis and the amount of drug sampled following topical drug administration. This study evaluates the relation between probe depth and drug sampling using dermal DMD sampling ex vivo in human skin. We used superficial (<1 mm), intermediate (1-2 mm) and deep (>2 mm) positioning of the linear MD probe in the dermis of human abdominal skin, followed by topical application of 4 mg/ml of benzoic acid (BA) in skin chambers overlying the probes. Dialysate was sampled every hour for 12 h and analysed for BA content by high-performance liquid chromatography. Probe depth was measured by 20-MHz ultrasound scanning. The area under the time-versus-concentration curve (AUC) describes the drug exposure in the tissue during the experiment and is a relevant parameter to compare for the 3 dermal probe depths investigated. The AUC(0-12) were: superficial probes: 3,335 ± 1,094 μg·h/ml (mean ± SD); intermediate probes: 2,178 ± 1,068 μg·h/ml, and deep probes: 1,159 ± 306 μg·h/ml. AUC(0-12) sampled by the superficial probes was significantly higher than that of samples from the intermediate and deeply positioned probes (p value <0.05). There was a significant inverse correlation between probe depth and AUC(0-12) sampled by the same probe (p value <0.001, r(2) value = 0.5). The mean extrapolated lag-times (±SD) for the superficial probes were 0.8 ± 0.1 h, for the intermediate probes 1.7 ± 0.5 h, and for the deep probes 2.7 ± 0.5 h, which were all significantly different from each other (p value <0.05). In conclusion, this paper demonstrates that there is an inverse relationship between the depth of the probe in the dermis

  7. Novel molecular beacon DNA probes for protein-nucleic acid interaction studies

    NASA Astrophysics Data System (ADS)

    Li, Jianwei J.; Perlette, John; Fang, Xiaohong; Kelley, Shannon; Tan, Weihong

    2000-03-01

    We report a novel approach to study protein-nucleic acid interactions by using molecular beacons (MBs). Molecular beacons are hairpin-shaped DNA oligonucleotide probes labeled with a fluorophore and a quencher, and can report the presence of target DNA/RNA sequences. MBs can also report the existence of single-stranded DNA binding proteins (SSB) through non-sequence specific binding. The interaction between SSB and MB has resulted in significant fluorescence restoration of the MB. The fluorescence enhancement brought by SSB and by complementary DNA is very comparable. The molar ratio of the binding between SSB and the molecular beacon is 1:1 with a binding constant of 2 X 107 M-1. Using the MB-SSB binding, we are able to determine SSB at 2 X 10-10 M with a conventional spectrometer. We have also applied MB DNA probes for the analysis of an enzyme lactic dehydrogenase (LDH), and for the investigation of its binding properties with ssDNA. The biding process between MB and different isoenzymes of LDH has been studied. We also show that there are significant differences in MB binding affinity to different proteins, which will enable selective binding studies of a variety of proteins. This new approach is potentially useful for protein-DNA/RNA interaction studies that require high sensitivity, speed and convenience. The results also open the possibility of using easily obtainable, custom designed, modified DNA molecules for studies of drug interactions and targeting. Our results demonstrate that MB can be effectively used for sensitive protein quantitation and for efficient protein-DNA interaction studies. MB has the signal transduction mechanism built within the molecule, and can thus be used for quick protein assay development and for real-time measurements.

  8. Peptide nucleic acid probe for protein affinity purification based on biotin-streptavidin interaction and peptide nucleic acid strand hybridization.

    PubMed

    Tse, Jenny; Wang, Yuanyuan; Zengeya, Thomas; Rozners, Eriks; Tan-Wilson, Anna

    2015-02-01

    We describe a new method for protein affinity purification that capitalizes on the high affinity of streptavidin for biotin but does not require dissociation of the biotin-streptavidin complex for protein retrieval. Conventional reagents place both the selectively reacting group (the "warhead") and the biotin on the same molecule. We place the warhead and the biotin on separate molecules, each linked to a short strand of peptide nucleic acid (PNA), synthetic polymers that use the same bases as DNA but attached to a backbone that is resistant to attack by proteases and nucleases. As in DNA, PNA strands with complementary base sequences hybridize. In conditions that favor PNA duplex formation, the warhead strand (carrying the tagged protein) and the biotin strand form a complex that is held onto immobilized streptavidin. As in DNA, the PNA duplex dissociates at moderately elevated temperature; therefore, retrieval of the tagged protein is accomplished by a brief exposure to heat. Using iodoacetate as the warhead, 8-base PNA strands, biotin, and streptavidin-coated magnetic beads, we demonstrate retrieval of the cysteine protease papain. We were also able to use our iodoacetyl-PNA:PNA-biotin probe for retrieval and identification of a thiol reductase and a glutathione transferase from soybean seedling cotyledons.

  9. Photoluminescence of Diamondoid Crystals

    SciTech Connect

    Clay, William; Sasagawa, Takao; Iwasa, Akio; Liu, Zhi; Dahl, Jeremy E.; Carlson, Robert M.K.; Kelly, Michael; Melos, Nicholas; Shen, Zhi-Xun; /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /Stanford U., Geballe Lab. /SIMES, Stanford

    2012-04-03

    The photoluminescence of diamondoids in the solid state is examined. All of the diamondoids are found to photoluminesce readily with initial excitation wavelengths ranging from 233 nm to 240 nm (5.3 eV). These excitation energies are more than 1 eV lower than any previously studied saturated hydrocarbon material. The emission is found to be heavily shifted from the absorption, with emission wavelengths of roughly 295 nm (4.2 eV) in all cases. In the dissolved state, however, no uorescence is observed for excitation wavelengths as short as 200 nm. We also discuss predictions and measurements of the quantum yield. Our predictions indicate that the maximum yield may be as high as 25%. Our measurement of one species, diamantane, gives a yield of 11%, the highest ever reported for a saturated hydrocarbon, even though it was likely not at the optimal excitation wavelength.

  10. [Oligonucleotide derivatives in the nucleic acid hybridization analysis. I. Covalent immobilization of oligonucleotide probes onto the nylon].

    PubMed

    Dmitrienko, E V; Pyshnaia, I A; Pyshnyĭ, D V

    2010-01-01

    The features of UV-induced immobilization of oligonucleotides on a nylon membranes and the effectiveness of enzymatic labeling of immobilized probes at heterophase detection of nucleic acids are studied. Short terminal oligothymidilate (up to 10 nt) sequences are suggested to attach to the probe via a flexible ethylene glycol based linker. The presence of such fragment enhances the intensity of immobilization and reduces UV-dependent degradation of the targeted (sequence-specific) part of the probe by reducing the dose needed for the immobilization of DNA. The optimum dose of UV-irradiation is determined to be ~0.4 J/cm(2) at the wavelength 254 nm. This dose provides high level of hybridization signal for immobilized probes with various nucleotide composition of the sequence specific moiety. The amide groups of the polyamide are shown to play the key role in the photoinduced immobilization of nucleic acids, whereas the primary amino groups in the structure of PA is not the center responsible for the covalent binding of DNA by UV-irradiation, as previously believed. Various additives in the soaking solution during the membrane of UV-dependent immobilization of probes are shown to influence its effectiveness. The use of alternative to UV-irradiation system of radical generation are shown to provide the immobilization of oligonucleotides onto the nylon membrane.

  11. Hybridization properties of long nucleic acid probes for detection of variable target sequences, and development of a hybridization prediction algorithm.

    PubMed

    Ohrmalm, Christina; Jobs, Magnus; Eriksson, Ronnie; Golbob, Sultan; Elfaitouri, Amal; Benachenhou, Farid; Strømme, Maria; Blomberg, Jonas

    2010-11-01

    One of the main problems in nucleic acid-based techniques for detection of infectious agents, such as influenza viruses, is that of nucleic acid sequence variation. DNA probes, 70-nt long, some including the nucleotide analog deoxyribose-Inosine (dInosine), were analyzed for hybridization tolerance to different amounts and distributions of mismatching bases, e.g. synonymous mutations, in target DNA. Microsphere-linked 70-mer probes were hybridized in 3M TMAC buffer to biotinylated single-stranded (ss) DNA for subsequent analysis in a Luminex® system. When mismatches interrupted contiguous matching stretches of 6 nt or longer, it had a strong impact on hybridization. Contiguous matching stretches are more important than the same number of matching nucleotides separated by mismatches into several regions. dInosine, but not 5-nitroindole, substitutions at mismatching positions stabilized hybridization remarkably well, comparable to N (4-fold) wobbles in the same positions. In contrast to shorter probes, 70-nt probes with judiciously placed dInosine substitutions and/or wobble positions were remarkably mismatch tolerant, with preserved specificity. An algorithm, NucZip, was constructed to model the nucleation and zipping phases of hybridization, integrating both local and distant binding contributions. It predicted hybridization more exactly than previous algorithms, and has the potential to guide the design of variation-tolerant yet specific probes.

  12. Sucrose esters of carboxylic acids in glandular trichomes ofSolanum berthaultii deter settling and probing by green peach aphid.

    PubMed

    Neal, J J; Tingey, W M; Steffens, J C

    1990-02-01

    Removal of type B trichome exudate fromSolanum berthaultii leaflets leads to a decrease in tarsal gumming and mortality and an increase in feeding by the green peach aphid,Myzus persicae. Type B trichome exudate of theS. berthaultii accession PI 473331 is composed of a complex of 3',3,4,6-tetra-O-acyl sucroses containing primarily short-chain branched carboxylic acids. The acyl constituents are primarily derived from 2-methylpropanoic, 2-methylbutyric, and 8-methylnonanoic acids but constituents derived fromn-decanoic and dodecanoic acids are also present. Sucrose esters inhibit settling and probing by aphids in glass feeding cages.

  13. Quantification of Syntrophic Fatty Acid-β-Oxidizing Bacteria in a Mesophilic Biogas Reactor by Oligonucleotide Probe Hybridization

    PubMed Central

    Hansen, Kaare H.; Ahring, Birgitte K.; Raskin, Lutgarde

    1999-01-01

    Small-subunit rRNA sequences were obtained for two saturated fatty acid-β-oxidizing syntrophic bacteria, Syntrophomonas sapovorans and Syntrophomonas wolfei LYB, and sequence analysis confirmed their classification as members of the family Syntrophomonadaceae. S. wolfei LYB was closely related to S. wolfei subsp. wolfei, but S. sapovorans did not cluster with the other members of the genus Syntrophomonas. Five oligonucleotide probes targeting the small-subunit rRNA of different groups within the family Syntrophomonadaceae, which contains all currently known saturated fatty acid-β-oxidizing syntrophic bacteria, were developed and characterized. The probes were designed to be specific at the family, genus, and species levels and were characterized by temperature-of-dissociation and specificity studies. To demonstrate the usefulness of the probes for the detection and quantification of saturated fatty acid-β-oxidizing syntrophic bacteria in methanogenic environments, the microbial community structure of a sample from a full-scale biogas plant was determined. Hybridization results with probes for syntrophic bacteria and methanogens were compared to specific methanogenic activities and microbial numbers determined with most-probable-number estimates. Most of the methanogenic rRNA was comprised of Methanomicrobiales rRNA, suggesting that members of this order served as the main hydrogen-utilizing microorganisms. Between 0.2 and 1% of the rRNA was attributed to the Syntrophomonadaceae, of which the majority was accounted for by the genus Syntrophomonas. PMID:10543784

  14. Photoluminescence of annealed biomimetic apatites.

    PubMed

    Zollfrank, Cordt; Müller, Lenka; Greil, Peter; Müller, Frank A

    2005-11-01

    Biomimetic apatite coatings are widely used in orthopaedic applications to provide bioinert material surfaces with bioactive behaviour by means of initiating bone growth at the implant surface. In this study we manufactured biomimetic calcium phosphate coatings consisting of a calcium deficient carbonated apatite by immersing activated titanium platelets into simulated body fluid. The development of the crystal phases was monitored by X-ray diffractometry in addition to Fourier-transform infrared spectroscopy. The microstructure of the biomimetic apatites and phase composition was analysed using scanning and transmission electron microscopy as well as attached energy dispersive X-ray spectrometry. The samples were annealed in air yielding in an inherent luminescence of the biomimetic apatite up to temperatures of 600 degrees C. The photo-induced emission spectra were recorded in the range from 400 to 750 nm at excitation wavelengths ranging 310-450 nm. A blue (437 nm) and a green (561 nm) emission were found between 200 and 600 degrees C visually appearing white. Photoluminescence of annealed biomimetic apatites might be of interest for histological probing and monitoring of bone re-modelling. The results are discussed in terms of chemical and crystallographic changes in the calcium phosphate layer during heat treatment.

  15. Differentiation of Candida albicans and Candida dubliniensis by Fluorescent In Situ Hybridization with Peptide Nucleic Acid Probes

    PubMed Central

    Oliveira, Kenneth; Haase, Gerhard; Kurtzman, Cletus; Hyldig-Nielsen, Jens Jo/rgen; Stender, Henrik

    2001-01-01

    The recent discovery of Candida dubliniensis as a separate species that traditionally has been identified as Candida albicans has led to the development of a variety of biochemical and molecular methods for the differentiation of these two pathogenic yeasts. rRNA sequences are well-established phylogenetic markers, and probes targeting species-specific rRNA sequences have been used in diagnostic assays for the detection and identification of microorganisms. Peptide nucleic acid (PNA) is a DNA mimic with improved hybridization characteristics, and the neutral backbone of PNA probes offers significant advantages in whole-cell in situ hybridization assays. In this study, we developed PNA probes targeting the rRNAs of C. albicans and C. dubliniensis and applied them to a fluorescence in situ hybridization method (PNA FISH) for differentiation between C. albicans and C. dubliniensis. Liquid cultures were smeared onto microscope slides, heat fixed, and then hybridized for 30 min. Unhybridized PNA probe was removed by washing, and smears were examined by fluorescence microscopy. Evaluation of the PNA FISH method using smears of 79 C. dubliniensis and 70 C. albicans strains showed 100% sensitivity and 100% specificity for both PNA probes. We concluded that PNA FISH is a powerful tool for the differentiation of C. albicans and C. dubliniensis. PMID:11682542

  16. Intracellular surface-enhanced Raman scattering probe based on gold nanorods functionalized with mercaptohexadecanoic acid with reduced cytotoxicity.

    PubMed

    Liu, Min; Wang, Zhuyuan; Zong, Shenfei; Zhang, Ruohu; Yang, Jing; Cui, Yiping

    2012-01-01

    A surface-enhanced Raman scattering (SERS) probe for intracellular detection was demonstrated by utilizing gold nanorods (GNRs) coated with p-aminothiophenol as the Raman reporters. In this probe, to reduce the cytotoxicity of GNRs, cetyltrimethylammonium bromide (CTAB) molecules adsorbed on the surfaces of GNRs as ligands were replaced by mercaptohexadecanoic acid via a "round-trip" phase change method. Such a ligand exchange can reduce the toxicity of the probe compared to the original CTAB-stabilized GNRs, which were confirmed by both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and bright field view of HeLa cells. Meanwhile, the transmission electron microscopy images indicated that there is no significant morphologic change of GNRs before and after the ligand exchange. Moreover, its SERS performance was adequately retained after the incorporation of the probe into living HeLa cells. This new type of SERS probe is expected to have great potential in intracellular imaging or sensing applications.

  17. Detection and quantification of genetically modified organisms using very short, locked nucleic acid TaqMan probes.

    PubMed

    Salvi, Sergio; D'Orso, Fabio; Morelli, Giorgio

    2008-06-25

    Many countries have introduced mandatory labeling requirements on foods derived from genetically modified organisms (GMOs). Real-time quantitative polymerase chain reaction (PCR) based upon the TaqMan probe chemistry has become the method mostly used to support these regulations; moreover, event-specific PCR is the preferred method in GMO detection because of its high specificity based on the flanking sequence of the exogenous integrant. The aim of this study was to evaluate the use of very short (eight-nucleotide long), locked nucleic acid (LNA) TaqMan probes in 5'-nuclease PCR assays for the detection and quantification of GMOs. Classic TaqMan and LNA TaqMan probes were compared for the analysis of the maize MON810 transgene. The performance of the two types of probes was tested on the maize endogenous reference gene hmga, the CaMV 35S promoter, and the hsp70/cryIA(b) construct as well as for the event-specific 5'-integration junction of MON810, using plasmids as standard reference molecules. The results of our study demonstrate that the LNA 5'-nuclease PCR assays represent a valid and reliable analytical system for the detection and quantification of transgenes. Application of very short LNA TaqMan probes to GMO quantification can simplify the design of 5'-nuclease assays.

  18. Visualization of the mycelia of wood-rotting fungi by fluorescence in situ hybridization using a peptide nucleic acid probe.

    PubMed

    Nakada, Yuji; Nakaba, Satoshi; Matsunaga, Hiroshi; Funada, Ryo; Yoshida, Makoto

    2013-01-01

    White rot fungus, Phanerochaete chrysosporium, and brown rot fungus, Postia placenta, grown on agar plates, were visualized by fluorescence in situ hybridization (FISH) using a peptide nucleic acid (PNA) probe. Mycelia grown on wood chips were also clearly detected by PNA-FISH following blocking treatment. To the best of our knowledge, this is the first report on the visualization of fungi in wood by FISH.

  19. A high-resolution mitochondria-targeting ratiometric fluorescent probe for detection of the endogenous hypochlorous acid

    NASA Astrophysics Data System (ADS)

    Zhou, Liyi; Lu, Dan-Qing; Wang, Qianqian; Hu, Shunqin; Wang, Haifei; Sun, Hongyan; Zhang, Xiaobing

    2016-09-01

    Hypochlorite anion, one of the biologically important reactive oxygen species, plays an essential role in diverse normal biochemical functions and abnormal pathological processes. Herein, an efficient high-resolution mitochondria-targeting ratiometric fluorescent probe for hypochlorous acid detection has been designed, synthesized and characterized. It is easily synthesized by the condensation reaction (Cdbnd C) of a 2-(2-hydroxyphenyl) quinazolin-4(3H)-one fluorophore and a cyanine group (mitochondria-targeting), which made the whole molecular a large Stokes shift (210 nm) and the two well-resolved emission peaks separated by 140 nm. As a result, it is considered as a good candidate for high resolution hypochlorous acid imaging in live cells. The ratiometric fluorescent probe exhibited outstanding features of high sensitivity, high selectivity, rapid response time (within 50 s), and excellent mitochondria-targeting ability. Moreover, the probe can also be successfully applied to imaging endogenously hypochlorous acid in the mitochondria of living cells with low cytotoxicity, and high resolution.

  20. A novel strategy for functionalizable photoluminescent magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Yan, Huan; Sung, Baeckkyoung; Kim, Min-Ho; Kim, Chanjoong

    2014-12-01

    This study presents functionalizable photoluminescent magnetic iron oxide nanoparticles (PLMNPs) produced by heating magnetic nanoparticles coated with non-photoluminescent hydrophilic poly(acrylic acid) (PAA) but without any add-on photoluminescent chemicals. The photoluminescence of PLMNPs is originated from a carbon nanodot layer that is converted from the PAA polymer coating layer during the heating process. Interestingly, PLMNPs are more photo-stable than conventional organic dyes. Further functionalization of PLMNPs is easily achieved through the coupling reaction with carboxyl groups of the coating layer on the surface. PLMNPs can be remotely heated by applying an alternating magnetic field due to the superparamagnetism, and are found to have good heating efficiency. All these advantages make these nanoparticles appealing for various biomedical applications, such as dual modality imaging and hyperthermia treatment.

  1. Theoretical study of the NLO responses of some natural and unnatural amino acids used as probe molecules.

    PubMed

    Derrar, S N; Sekkal-Rahal, M; Derreumaux, P; Springborg, M

    2014-08-01

    The first hyperpolarizabilities β of the natural aromatic amino acids tryptophan and tyrosine have been investigated using several methods and basis sets. Some of the theoretical results obtained were compared to the only experimental hyper-Rayleigh scattering data available. The sensitivity of tryptophan to its local environment was analyzed by constructing two-dimensional potential energy plots around the dipeptide tryptophan-lysine. Static hyperpolarizabilities β(0) of the found minima were calculated by a second-order Møller-Plesset (MP2) method in combination with the 6-31+G(d) basis set. Moreover, the efficiency of tryptophan and those of a series of unnatural amino acids as endogenous probe molecules were tested by calculating the nonlinear responses of some peptides. Impressive results were obtained for the amino acid ALADAN, which shows significantly improved nonlinear performance compared to other amino acids with weak nonlinear responses.

  2. An intuitive method to probe phase structure by upconversion photoluminescence of Er3+ doped in ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3

    NASA Astrophysics Data System (ADS)

    Yao, Yongjie; Luo, Laihui; Li, Weiping; Zhou, Jun; Wang, Feifei

    2015-02-01

    (0.97-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3-0.03Pb(Er1/2Nb1/2)O3 (PMN-xPT:Er) ceramics with different PT contents are prepared. The dielectric, piezoelectric, ferroelectric, and upconversion (UC) photoluminescence properties of the ceramics are investigated. The crystal structure of PMN-xPT:Er evolves from rhombohedral to the morphotropic phase boundary (MPB), and then to the tetragonal phase as the PT content increases. The ratio of red to green emission intensities of UC emission is strongly correlated with the phase structure of the host PMN-xPT:Er ceramic. The origin of this correlation is discussed based on Judd-Ofelt theory. Furthermore, based on the evolution of crystal symmetry of the PMN-xPT:Er ceramics, the crystal structure of the MPB phase of PMN-xPT is suggested.

  3. Detection of chromosomal inversions using non-repetitive nucleic acid probes

    NASA Technical Reports Server (NTRS)

    Bailey, Susan M. (Inventor); Ray, F. Andrew (Inventor); Goodwin, Edwin H. (Inventor); Bedford, Joel S. (Inventor); Cornforth, Michael N. (Inventor)

    2012-01-01

    A method for the identification of chromosomal inversions is described. Single-stranded sister chromatids are generated, for example by CO-FISH. A plurality of non-repetitive, labeled probes of relatively small size are hybridized to portions of only one of a pair of single-stranded sister chromatids. If no inversion exists, all of the probes will hybridize to a first chromatid. If an inversion has occurred, these marker probes will be detected on the sister chromatid at the same location as the inversion on the first chromatid.

  4. Detection of Chromosomal Inversions Using Non-Repetitive Nucleic Acid Probes

    NASA Technical Reports Server (NTRS)

    Bailey, Susan M. (Inventor); Ray, F. Andrew (Inventor); Goodwin, Edwin H. (Inventor); Bedford, Joel S. (Inventor); Cornforth, Michael N. (Inventor)

    2014-01-01

    A method and a kit for the identification of chromosomal inversions are described. Single-stranded sister chromatids are generated, for example by CO-FISH. A plurality of non-repetitive, labeled probes of relatively small size are hybridized to portions of only one of a pair of single-stranded sister chromatids. If no inversion exists, all of the probes will hybridize to a first chromatid. If an inversion has occurred, these marker probes will be detected on the sister chromatid at the same location as the inversion on the first chromatid.

  5. Detection of Sialic Acid-Utilising Bacteria in a Caecal Community Batch Culture Using RNA-Based Stable Isotope Probing

    PubMed Central

    Young, Wayne; Egert, Markus; Bassett, Shalome A.; Bibiloni, Rodrigo

    2015-01-01

    Sialic acids are monosaccharides typically found on cell surfaces and attached to soluble proteins, or as essential components of ganglioside structures that play a critical role in brain development and neural transmission. Human milk also contains sialic acid conjugated to oligosaccharides, glycolipids, and glycoproteins. These nutrients can reach the large bowel where they may be metabolised by the microbiota. However, little is known about the members of the microbiota involved in this function. To identify intestinal bacteria that utilise sialic acid within a complex intestinal community, we cultured the caecal microbiota from piglets in the presence of 13C-labelled sialic acid. Using RNA-based stable isotope probing, we identified bacteria that consumed 13C-sialic acid by fractionating total RNA in isopycnic buoyant density gradients followed by 16S rRNA gene analysis. Addition of sialic acid caused significant microbial community changes. A relative rise in Prevotella and Lactobacillus species was accompanied by a corresponding reduction in the genera Escherichia/Shigella, Ruminococcus and Eubacterium. Inspection of isotopically labelled RNA sequences suggests that the labelled sialic acid was consumed by a wide range of bacteria. However, species affiliated with the genus Prevotella were clearly identified as the most prolific users, as solely their RNA showed significantly higher relative shares among the most labelled RNA species. Given the relevance of sialic acid in nutrition, this study contributes to a better understanding of their microbial transformation in the intestinal tract with potential implications for human health. PMID:25816158

  6. Hybridization probe for femtomolar quantification of selected nucleic acid sequences on a disposable electrode.

    PubMed

    Jenkins, Daniel M; Chami, Bilal; Kreuzer, Matthias; Presting, Gernot; Alvarez, Anne M; Liaw, Bor Yann

    2006-04-01

    Mixed monolayers of electroactive hybridization probes on gold surfaces of a disposable electrode were investigated as a technology for simple, sensitive, selective, and rapid gene identification. Hybridization to the ferrocene-labeled hairpin probes reproducibly diminished cyclic redox currents, presumably due to a displacement of the label from the electrode. Observed peak current densities were roughly 1000x greater than those observed in previous studies, such that results could easily be interpreted without the use of algorithms to correct for background polarization currents. Probes were sensitive to hybridization with a number of oligonucleotide sequences with varying homology, but target oligonucleotides could be distinguished from competing nontarget sequences based on unique "melting" profiles from the probe. Detection limits were demonstrated down to nearly 100 fM, which may be low enough to identify certain genetic conditions or infections without amplification. This technology has rich potential for use in field devices for gene identification as well as in gene microarrays.

  7. Human papillomavirus 35 nucleic acid hybridization probes and methods for employing the same

    SciTech Connect

    Lorincz, A.T.

    1989-07-18

    This patent describes an HPV 35 hybridization probe comprising a member selected from the group consisting of (i) HPV 35 DNA or fragments thereof labelled with a marker and (ii) HPV 35 RNA or fragments thereof labelled with a marker.

  8. Human papillomavirus 43 nucleic acid hybridization probes and methods for employing the same

    SciTech Connect

    Lorincz, A.T.

    1989-07-18

    This patent describes an HPV 43 hybridization probe comprising a member selected from the group consisting of (i) HPV 43 DNA or fragments thereof labelled with a marker and (ii) HPV 43 RNA or fragments thereof labelled with a marker.

  9. Human papillomavirus 56 nucleic acid hybridization probes and methods for employing the same

    SciTech Connect

    Lorinez, A.T.

    1990-03-13

    This patent describes an HPV 56 hybridization probe. It comprises: a member selected from the group consisting of HPV 56 DNA or fragments thereof labelled with a marker and HPV 56 RNA or fragments thereof labelled with a marker.

  10. Human papillomavirus 44 nucleic acid hybridization probes and methods for employing the same

    SciTech Connect

    Lorincz, A.T.

    1989-07-18

    This patent describes an HPV 44 hybridization probe comprising a member selected from the group consisting of (1) HPV 44 DNA or fragments thereof labelled with a marker and (ii) HPV 44 RNA or fragments thereof labelled with a marker.

  11. Making Graphene Nanoribbons Photoluminescent.

    PubMed

    Senkovskiy, B V; Pfeiffer, M; Alavi, S K; Bliesener, A; Zhu, J; Michel, S; Fedorov, A V; German, R; Hertel, D; Haberer, D; Petaccia, L; Fischer, F R; Meerholz, K; van Loosdrecht, P H M; Lindfors, K; Grüneis, A

    2017-04-03

    We demonstrate the alignment-preserving transfer of parallel graphene nanoribbons (GNRs) onto insulating substrates. The photophysics of such samples is characterized by polarized Raman and photoluminescence (PL) spectroscopies. The Raman scattered light and the PL are polarized along the GNR axis. The Raman cross section as a function of excitation energy has distinct excitonic peaks associated with transitions between the one-dimensional parabolic subbands. We find that the PL of GNRs is intrinsically low but can be strongly enhanced by blue laser irradiation in ambient conditions or hydrogenation in ultrahigh vacuum. These functionalization routes cause the formation of sp(3) defects in GNRs. We demonstrate the laser writing of luminescent patterns in GNR films for maskless lithography by the controlled generation of defects. Our findings set the stage for further exploration of the optical properties of GNRs on insulating substrates and in device geometries.

  12. Y chromosome specific nucleic acid probe and method for identifying the Y chromosome in SITU

    DOEpatents

    Gray, Joe W.; Weier, Heinz-Ulrich

    1999-01-01

    A method for producing a Y chromosome specific probe selected from highly repeating sequences on that chromosome is described. There is little or no nonspecific binding to autosomal and X chromosomes, and a very large signal is provided. Inventive primers allowing the use of PCR for both sample amplification and probe production are described, as is their use in producing large DNA chromosome painting sequences.

  13. Y chromosome specific nucleic acid probe and method for determining the Y chromosome in situ

    DOEpatents

    Gray, J.W.; Weier, H.U.

    1998-11-24

    A method for producing a Y chromosome specific probe selected from highly repeating sequences on that chromosome is described. There is little or no nonspecific binding to autosomal and X chromosomes, and a very large signal is provided. Inventive primers allowing the use of PCR for both sample amplification and probe production are described, as is their use in producing large DNA chromosome painting sequences. 9 figs.

  14. Y chromosome specific nucleic acid probe and method for determining the Y chromosome in situ

    DOEpatents

    Gray, Joe W.; Weier, Heinz-Ulrich

    1998-01-01

    A method for producing a Y chromosome specific probe selected from highly repeating sequences on that chromosome is described. There is little or no nonspecific binding to autosomal and X chromosomes, and a very large signal is provided. Inventive primers allowing the use of PCR for both sample amplification and probe production are described, as is their use in producing large DNA chromosome painting sequences.

  15. Y chromosome specific nucleic acid probe and method for determining the Y chromosome in situ

    DOEpatents

    Gray, Joe W.; Weier, Heinz-Ulrich

    2001-01-01

    A method for producing a Y chromosome specific probe selected from highly repeating sequences on that chromosome is described. There is little or no nonspecific binding to autosomal and X chromosomes, and a very large signal is provided. Inventive primers allowing the use of PCR for both sample amplification and probe production are described, as is their use in producing large DNA chromosome painting sequences.

  16. Y chromosome specific nucleic acid probe and method for identifying the Y chromosome in SITU

    DOEpatents

    Gray, J.W.; Weier, H.U.

    1999-03-30

    A method for producing a Y chromosome specific probe selected from highly repeating sequences on that chromosome is described. There is little or no nonspecific binding to autosomal and X chromosomes, and a very large signal is provided. Inventive primers allowing the use of PCR for both sample amplification and probe production are described, as is their use in producing large DNA chromosome painting sequences. 9 figs.

  17. NanoCluster Beacon - A New Molecular Probe for Homogeneous Detection of Nucleic Acid Targets

    DTIC Science & Technology

    2011-02-01

    requires only a single preparation step (i.e. nanocluster formation on NC probes), but because there is no need to remove excess silver ions or...Oligonucleotide-templated nanoclusters consisting of a few atoms of silver (DNA/Ag NCs) have been made into a new molecular probe that “lights up...upon target DNA binding, termed a NanoCluster Beacon (NCB). We discovered that interactions between silver nanoclusters and a proximal, guanine- rich

  18. A universal strategy for visual chiral recognition of α-amino acids with L-tartaric acid-capped gold nanoparticles as colorimetric probes.

    PubMed

    Song, Guoxin; Zhou, Fulin; Xu, Chunli; Li, Baoxin

    2016-02-21

    The ability to recognize and quantify the chirality of alpha-amino acids constitutes the basis of many critical areas for specific targeting in drug development and metabolite probing. It is still challenging to conveniently distinguish the enantiomer of amino acids largely due to the lack of a universal and simple strategy. In this work, we report a strategy for the visual recognition of α-amino acids. It is based on the chirality of L-tartaric acid-capped gold nanoparticles (L-TA-capped AuNPs, ca. 13 nm in diameter). All of 19 right-handed α-amino acids can induce a red-to-blue color change of L-TA-capped AuNP solution, whereas all of the left-handed amino acids (except cysteine) cannot. The chiral recognition can be achieved by the naked eye and a simple spectrophotometer. This method does not require complicated chiral modification, and excels through its low-cost, good availability of materials and its simplicity. Another notable feature of this method is its high generality, and this method can discriminate almost all native α-amino acid enantiomers. This versatile method could be potentially used for high-throughput chiral recognition of amino acids.

  19. Probing the Substrate Specificity and Protein-Protein Interactions of the E. coli Fatty Acid Dehydratase, FabA

    PubMed Central

    Finzel, Kara; Nguyen, Chi; Jackson, David R.; Gupta, Aarushi; Tsai, Shiou-Chuan; Burkart, Michael D.

    2015-01-01

    Summary Microbial fatty acid biosynthetic enzymes are important targets for areas as diverse as antibiotic development to biofuel production. Elucidating the molecular basis of chain length control during fatty acid biosynthesis is crucial for the understanding of regulatory processes of this fundamental metabolic pathway. In Escherichia coli, the acyl carrier protein (AcpP) plays a central role by sequestering and shuttling the growing acyl chain between fatty acid biosynthetic enzymes. FabA, a β-hydroxylacyl-AcpP dehydratase, is an important enzyme in controlling fatty acid chain length and saturation levels. FabA-AcpP interactions are transient in nature and thus difficult to visualize. In this study, four mechanistic crosslinking probes mimicking varying acyl chain lengths were synthesized to systematically probe for modified chain length specificity of fourteen FabA mutants. These studies provide evidence for the AcpP interacting “positive patch,” FabA mutations that altered substrate specificity, and the roles that the FabA “gating residues” play in chain-length selection. PMID:26526101

  20. Fluorescent amino acid undergoing excited state intramolecular proton transfer for site-specific probing and imaging of peptide interactions.

    PubMed

    Sholokh, Marianna; Zamotaiev, Oleksandr M; Das, Ranjan; Postupalenko, Viktoriia Y; Richert, Ludovic; Dujardin, Denis; Zaporozhets, Olga A; Pivovarenko, Vasyl G; Klymchenko, Andrey S; Mély, Yves

    2015-02-12

    Fluorescent amino acids bearing environment-sensitive fluorophores are highly valuable tools for site-selective probing of peptide/ligand interactions. Herein, we synthesized a fluorescent l-amino acid bearing the 4'-methoxy-3-hydroxyflavone fluorophore (M3HFaa) that shows dual emission, as a result of an excited state intramolecular proton transfer (ESIPT). The dual emission of M3HFaa was found to be substantially more sensitive to hydration as compared to previous analogues. By replacing the Ala30 and Trp37 residues of a HIV-1 nucleocapsid peptide, M3HFaa was observed to preserve the peptide structure and functions. Interaction of the labeled peptides with nucleic acids and lipid vesicles produced a strong switch in their dual emission, favoring the emission of the ESIPT product. This switch was associated with the appearance of long-lived fluorescence lifetimes for the ESIPT product, as a consequence of the rigid environment in the complexes that restricted the relative motions of the M3HFaa aromatic moieties. The strongest restriction and thus the longest fluorescence lifetimes were observed at position 37 in complexes with nucleic acids, where the probe likely stacks with the nucleobases. Based on the dependence of the lifetime values on the nature of the ligand and the labeled position, two-photon fluorescence lifetime imaging was used to identify the binding partners of the labeled peptides microinjected into living cells. Thus, M3HFaa appears as a sensitive tool for monitoring site selectively peptide interactions in solution and living cells.

  1. Fluorescence In Situ Hybridization with Peptide Nucleic Acid Probes for Rapid Identification of Candida albicans Directly from Blood Culture Bottles

    PubMed Central

    Rigby, Susan; Procop, Gary W.; Haase, Gerhard; Wilson, Deborah; Hall, Geraldine; Kurtzman, Cletus; Oliveira, Kenneth; Von Oy, Sabina; Hyldig-Nielsen, Jens J.; Coull, James; Stender, Henrik

    2002-01-01

    A new fluorescence in situ hybridization (FISH) method that uses peptide nucleic acid (PNA) probes for identification of Candida albicans directly from positive-blood-culture bottles in which yeast was observed by Gram staining (herein referred to as yeast-positive blood culture bottles) is described. The test (the C. albicans PNA FISH method) is based on a fluorescein-labeled PNA probe that targets C. albicans 26S rRNA. The PNA probe is added to smears made directly from the contents of the blood culture bottle and hybridized for 90 min at 55°C. Unhybridized PNA probe is removed by washing of the mixture (30 min), and the smears are examined by fluorescence microscopy. The specificity of the method was confirmed with 23 reference strains representing phylogenetically related yeast species and 148 clinical isolates covering the clinically most significant yeast species, including C. albicans (n = 72), C. dubliniensis (n = 58), C. glabrata (n = 5), C. krusei (n = 2), C. parapsilosis (n = 4), and C. tropicalis (n = 3). The performance of the C. albicans PNA FISH method as a diagnostic test was evaluated with 33 routine and 25 simulated yeast-positive blood culture bottles and showed 100% sensitivity and 100% specificity. It is concluded that this 2.5-h method for the definitive identification of C. albicans directly from yeast-positive blood culture bottles provides important information for optimal antifungal therapy and patient management. PMID:12037084

  2. Real-time, in-situ analysis of silver ions using nucleic acid probes modified silica microfiber interferometry.

    PubMed

    Yu, Bo; Huang, Yunyun; Zhou, Jun; Guo, Tuan; Guan, Bai-Ou

    2017-04-01

    A sensitive Ag(+) sensor based on nucleic acid probes modified silica microfiber interferometry is designed and developed. The probes on microfiber surface plays the part on catching Ag(+) as tentacles, while their conformation change from random coils to hairpins. It induces the fiber surface refractive index change, which is captured by the optical fiber and translated into a significant wavelength shift in the interferometric fringe. Such a combination enables an improved concentration sensitivity of 0.22nm/log M and limit of detection of 1.36 × 10(-9)M, taking the advantage of real-time and in-situ analysis. It shows good selectivity in the present of many other metal ions and offers potential to analysis in real matrix, especially in the environmental samples must be analyzed in a short time. This may provide insights into the preparation of sensing platforms for optical quantification of other small molecular, supplementing the existing tools.

  3. Focused upon hybridization: rapid and high sensitivity detection of DNA using isotachophoresis and peptide nucleic acid probes.

    PubMed

    Ostromohov, Nadya; Schwartz, Ortal; Bercovici, Moran

    2015-09-15

    We present a novel assay for rapid and high sensitivity detection of nucleic acids without amplification. Utilizing the neutral backbone of peptide nucleic acids (PNA), our method is based on the design of low electrophoretic mobility PNA probes, which do not focus under isotachophoresis (ITP) unless bound to their target sequence. Thus, background noise associated with free probes is entirely eliminated, significantly improving the signal-to-noise ratio while maintaining a simple single-step assay requiring no amplification steps. We provide a detailed analytical model and experimentally demonstrate the ability to detect targets as short as 17 nucleotides (nt) and a limit of detection of 100 fM with a dynamic range of 5 decades. We also demonstrate that the assay can be successfully implemented for detection of DNA in human serum without loss of signal. The assay requires 15 min to complete, and it could potentially be used in applications where rapid and highly sensitive amplification-free detection of nucleic acids is desired.

  4. Novel, highly photoluminescent Eu(III) and Tb(III) tetrazolate-2-pyridine-1-oxide complexes

    NASA Astrophysics Data System (ADS)

    Pietraszkiewicz, Marek; Mal, Suraj; Pietraszkiewicz, Oksana

    2012-07-01

    Tetrazole-2-pyridine-1-oxide was prepared from 2-cyanopyridine and sodium azide, followed by oxidation with m-chloroperbenzoic acid. This ligand forms neutral 1:3 complexes with Eu(III) and Tb(III) cations. The complexes are photoluminescent in solution, with photoluminescence quantum yields 13% and 31%, respectively.

  5. Real-Time PCR Genotyping using Taqman Probes to Detect High Oleic Acid Peanuts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Oleic acid, a monounsaturated, omega-9 fatty acid is an important agronomic trait in peanut cultivars because it provides increased shelf life, improved flavor, enhanced fatty acid composition, and a beneficial effect on human health. Currently, most high oleic peanuts confer limited resistance to ...

  6. Probing the acidity of carboxylic acids in protic ionic liquids, water, and their binary mixtures: activation energy of proton transfer.

    PubMed

    Shukla, Shashi Kant; Kumar, Anil

    2013-02-28

    Acidity functions were used to express the ability of a solvent/solution to donate/accept a proton to a solute. The present work accounts for the acidity determination of HCOOH, CH3COOH, and CH3CH2COOH in the alkylimidazolium-based protic ionic liquids (PILs), incorporated with carboxylate anion, water, and in a binary mixture of PIL and water using the Hammett acidity function, H0. A reversal in the acidity trend was observed, when organic acids were transferred from water to PIL. It was emphasized that an increased stabilization offered by PIL cation toward the more basic conjugate anion of organic acid was responsible for this anomalous change in acidity order in PILs, which was absent in water. The greater stabilization of a basic organic anion by PIL cation is discussed in terms of the stable hard–soft acid base (HSAB) pairing. A change in the H0 values of these acids was observed with a change in temperature, and a linear correlation between the ln H0 and 1/T was noted. This relationship points toward the activation energy of proton transfer (E(a,H+)), a barrier provided by the medium during the proton transfer from Brønsted acid to indicator. The H0 function in binary mixtures points to the involvement of pseudosolvent, the behavior of which changes with the nature and concentration of acid. The presence of the maxima/minima in the H0 function is discussed in terms of the synergetic behavior of the pseudosolvent composed of the mixtures of aqueous PILs.

  7. Nitrogen-doped carbon dots as multifunctional fluorescent probes

    NASA Astrophysics Data System (ADS)

    Du, Fengyi; Jin, Xin; Chen, Junhui; Hua, Ye; Cao, Mulan; Zhang, Lirong; Li, Jianan; Zhang, Li; Jin, Jie; Wu, Chaoyang; Gong, Aihua; Xu, Wenrong; Shao, Qixiang; Zhang, Miaomiao

    2014-11-01

    Highly fluorescent nitrogen-doped carbon dots (NCDs) were prepared through the hydrothermal carbonization of citric acid and ammonium acetate. The resulting NCDs were quasi-spherical particles with an average diameter of approximately 2.1 nm. They exhibited excellent photoluminescent properties and had favorable solubility in water. Furthermore, the NCDs had low cytotoxicity and were readily integrated with cytoplasm. This makes them particularly suitable for multicolor bioimaging. Most importantly, NCDs internalized by cancer cells can be detected at four channels simultaneously with flow cytometry, which further demonstrates that the NCDs can be used as multifunctional fluorescent probes for biomedical applications.

  8. Proteomic-based stable isotope probing reveals taxonomically Distinct Patterns in Amino Acid Assimilation by Coastal Marine Bacterioplankton

    DOE PAGES

    Bryson, Samuel; Li, Zhou; Pett-Ridge, Jennifer; ...

    2016-04-26

    Heterotrophic marine bacterioplankton are a critical component of the carbon cycle, processing nearly a quarter of annual global primary production, yet defining how substrate utilization preferences and resource partitioning structure these microbial communities remains a challenge. In this study, we utilized proteomics-based stable isotope probing (proteomic SIP) to characterize the assimilation of amino acids by coastal marine bacterioplankton populations. We incubated microcosms of seawater collected from Newport, OR and Monterey Bay, CA with 1 M 13C-amino acids for 15 and 32 hours. Subsequent analysis of 13C incorporation into protein biomass quantified the frequency and extent of isotope enrichment for identifiedmore » proteins. Using these metrics we tested whether amino acid assimilation patterns were different for specific bacterioplankton populations. Proteins associated with Rhodobacterales and Alteromonadales tended to have a significantly high number of tandem mass spectra from 13C-enriched peptides, while Flavobacteriales and SAR11 proteins generally had significantly low numbers of 13C-enriched spectra. Rhodobacterales proteins associated with amino acid transport and metabolism had an increased frequency of 13C-enriched spectra at time-point 2, while Alteromonadales ribosomal proteins were 13C- enriched across time-points. Overall, proteomic SIP facilitated quantitative comparisons of dissolved free amino acids assimilation by specific taxa, both between sympatric populations and between protein functional groups within discrete populations, allowing an unprecedented examination of population-level metabolic responses to resource acquisition in complex microbial communities.« less

  9. Ancillary ligand-assisted assembly of C3-symmetric 4,4‧,4″-nitrilotribenzoic acid with divalent Zn2+ ions: Syntheses, topological structures, and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Cui, Li-Ting; Niu, Yan-Fei; Han, Jie; Zhao, Xiao-Li

    2015-07-01

    4,4‧,4″-nitrilotribenzoic acid (H3L), a C3-symmetric ligand, was found to self-assemble into two polymorphs driven by intermolecular hydrogen-bonding interactions. Reactions of this ligand with Zn2+ under solvothermal conditions resulted in four new coordination polymers bearing interesting structural motifs: [Zn2(L)2(py)2]·2(H2NMe2)+·DMF·2H2O (1), [Zn2(L)(H2L)(bipy)]·1.5H2O·Guest (2), [Zn2(L)2(bipy)]·2(H2NMe2)+·2DMF (3), and [Zn3(L)2(bpa)]·2H2O·Guest (4) (H3L=4,4‧,4‧‧-nitrilotribenzoic acid, DMF=dimethylformamide, py=pyridine, bipy=4,4‧-bipyridine, bpa=1,2-bis(4-pyridyl)diazene). Single-crystal structural analysis revealed that compound 1 exhibits a rare example of twofold interpenetrating anionic 3D (3,3)-net framework containing helical channels, whereas in 2, the 3D pillar-layer structure generated from bipy-pillared Zn2(L)(H2L) layer is further reinforced by intermolecular hydrogen bonding among pairs of free -COOH units. Compound 3 shows an interesting entangled architecture of 2D→3D parallel polycatenation consisting five-coordinated Zn2+ ions. Compound 4 displays a 3D pillar-layer framework with trimeric Zn3(CO2)6 serving as secondary building unit (SBU). The syntheses, structures, thermal stabilities, powder X-ray diffractions and solid-state photoluminescence properties for these crystalline materials have been carried out. In addition, supramolecular assembly of H3L under solvothermal conditions will also be addressed.

  10. Hybridization-based detection of Helicobacter pylori at human body temperature using advanced locked nucleic acid (LNA) probes.

    PubMed

    Fontenete, Sílvia; Guimarães, Nuno; Leite, Marina; Figueiredo, Céu; Wengel, Jesper; Filipe Azevedo, Nuno

    2013-01-01

    The understanding of the human microbiome and its influence upon human life has long been a subject of study. Hence, methods that allow the direct detection and visualization of microorganisms and microbial consortia (e.g. biofilms) within the human body would be invaluable. In here, we assessed the possibility of developing a variant of fluorescence in situ hybridization (FISH), named fluorescence in vivo hybridization (FIVH), for the detection of Helicobacter pylori. Using oligonucleotide variations comprising locked nucleic acids (LNA) and 2'-O-methyl RNAs (2'OMe) with two types of backbone linkages (phosphate or phosphorothioate), we were able to successfully identify two probes that hybridize at 37 °C with high specificity and sensitivity for H. pylori, both in pure cultures and in gastric biopsies. Furthermore, the use of this type of probes implied that toxic compounds typically used in FISH were either found to be unnecessary or could be replaced by a non-toxic substitute. We show here for the first time that the use of advanced LNA probes in FIVH conditions provides an accurate, simple and fast method for H. pylori detection and location, which could be used in the future for potential in vivo applications either for this microorganism or for others.

  11. Spectroscopic quantification of 5-hydroxymethylcytosine in genomic DNA using boric acid-functionalized nano-microsphere fluorescent probes.

    PubMed

    Chen, Hua-Yan; Wei, Jing-Ru; Pan, Jiong-Xiu; Zhang, Wei; Dang, Fu-Quan; Zhang, Zhi-Qi; Zhang, Jing

    2017-05-15

    5-hydroxymethylcytosine (5hmC) is the sixth base of DNA. It is involved in active DNA demethylation and can be a marker of diseases such as cancer. In this study, we developed a simple and sensitive 2-(4-boronophenyl)quinoline-4-carboxylic acid modified poly (glycidyl methacrylate (PBAQA-PGMA) fluorescent probe to detect the 5hmC content of genomic DNA based on T4 β-glucosyltransferase-catalyzed glucosylation of 5hmC. The fluorescence-enhanced intensity recorded from the DNA sample was proportional to its 5-hydroxymethylcytosine content and could be quantified by fluorescence spectrophotometry. The developed probe showed good detection sensitivity and selectivity and a good linear relationship between the fluorescence intensity and the concentration of 5 hmC within a 0-100nM range. Compared with other fluorescence detection methods, this method not only could determine trace amounts of 5 hmC from genomic DNA but also could eliminate the interference of fluorescent dyes and the need for purification. It also could avoid multiple labeling. Because the PBAQA-PGMA probe could enrich the content of glycosyl-5-hydroxymethyl-2-deoxycytidine from a complex ground substance, it will broaden the linear detection range and improve sensitivity. The limit of detection was calculated to be 0.167nM after enrichment. Furthermore, the method was successfully used to detect 5-hydroxymethylcytosine from mouse tissues.

  12. Mercaptopropionic acid-capped CdTe quantum dots as fluorescence probe for the determination of salicylic acid in pharmaceutical products.

    PubMed

    Bunkoed, Opas; Kanatharana, Proespichaya

    2015-11-01

    Mercaptopropionic acid (MPA)-capped cadmium telluride (CdTe) quantum dot (QDs) fluorescent probes were synthesized in aqueous solution and used for the determination of salicylic acid. The interaction between the MPA-capped CdTe QDs and salicylic acid was studied using fluorescence spectroscopy and some parameters that could modify the fluorescence were investigated to optimize the measurements. Under optimum conditions, the quenched fluorescence intensity of MPA-capped CdTe QDs was linearly proportional to the concentration of salicylic acid in the range of 0.5-40 µg mL(-1) with a coefficient of determination of 0.998, and the limit of detection was 0.15 µg mL(-1). The method was successfully applied to the determination of salicylic acid in pharmaceutical products, and satisfactory results were obtained that were in agreement with both the high pressure liquid chromatography (HPLC) method and the claimed values. The recovery of the method was in the range 99 ± 3% to 105 ± 9%. The proposed method is simple, rapid, cost effective, highly sensitivity and eminently suitable for the quality control of pharmaceutical preparation. The possible mechanisms for the observed quenching reaction was also discussed.

  13. A confocal study on the visualization of chromaffin cell secretory vesicles with fluorescent targeted probes and acidic dyes.

    PubMed

    Moreno, Alfredo; SantoDomingo, Jaime; Fonteriz, Rosalba I; Lobatón, Carmen D; Montero, Mayte; Alvarez, Javier

    2010-12-01

    Secretory vesicles have low pH and have been classically identified as those labelled by a series of acidic fluorescent dyes such as acridine orange or neutral red, which accumulate into the vesicles according to the pH gradient. More recently, several fusion proteins containing enhanced green fluorescent protein (EGFP) and targeted to the secretory vesicles have been engineered. Both targeted fluorescent proteins and acidic dyes have been used, separately or combined, to monitor the dynamics of secretory vesicle movements and their fusion with the plasma membrane. We have now investigated in detail the degree of colocalization of both types of probes using several fusion proteins targeted to the vesicles (synaptobrevin2-EGFP, Cromogranin A-EGFP and neuropeptide Y-EGFP) and several acidic dyes (acridine orange, neutral red and lysotracker red) in chromaffin cells, PC12 cells and GH(3) cells. We find that all the acidic dyes labelled the same population of vesicles. However, that population was largely different from the one labelled by the targeted proteins, with very little colocalization among them, in all the cell types studied. Our data show that the vesicles containing the proteins more characteristic of the secretory vesicles are not labelled by the acidic dyes, and vice versa. Peptide glycyl-L-phenylalanine 2-naphthylamide (GPN) produced a rapid and selective disruption of the vesicles labelled by acidic dyes, suggesting that they could be mainly lysosomes. Therefore, these labelling techniques distinguish two clearly different sets of acidic vesicles in neuroendocrine cells. This finding should be taken into account whenever vesicle dynamics is studied using these techniques.

  14. Carboxylic Acid Ionophores as Probes of the Role of Calcium in Biological Systems

    NASA Technical Reports Server (NTRS)

    Reed, P. W.

    1983-01-01

    The biological effects of calcium ionophores are described, focusing on arachidonic acid oxygenation, and the formation of a number of oxygenated metabolites of arachidonic acid. These metabolites are involved in a number of bodily functions, and their production may be regulated by calcium.

  15. Probing acid-amide intermolecular hydrogen bonding by NMR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Chaudhari, Sachin Rama; Suryaprakash, N.

    2012-05-01

    Benzene carboxylic acids and benzamide act as their self-complement in molecular recognition to form inter-molecular hydrogen bonded dimers between amide and carboxylic acid groups, which have been investigated by 1H, 13C and 15N NMR spectroscopy. Extensive NMR studies using diffusion ordered spectroscopy (DOSY), variable temperature 1D, 2D NMR, established the formation of heterodimers of benzamide with benzoic acid, salicylic acid and phenyl acetic acid in deuterated chloroform solution. Association constants for the complex formation in the solution state have been determined. The results are ascertained by X-ray diffraction in the solid state. Intermolecular interactions in solution and in solid state were found to be similar. The structural parameters obtained by X-ray diffraction studies are compared with those obtained by DFT calculations.

  16. Stimuli-responsive photoluminescent liquid crystals.

    PubMed

    Yamane, Shogo; Tanabe, Kana; Sagara, Yoshimitsu; Kato, Takashi

    2012-01-01

    We describe mechanochromic and thermochromic photoluminescent liquid crystals. In particular, mechanochromic photoluminescent liquid crystals found recently, which are new stimuli-responsive materials are reported. For example, photoluminescent liquid crystals having bulky dendritic moieties with long alkyl chains change their photoluminescent colors by mechanical stimuli associated with isothermal phase transitions. The photoluminescent properties of molecular assemblies depend on their assembled structures. Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Mechanochromic photoluminescent properties are also observed for a photoluminescent metallomesogen and a liquid-crystalline polymer. We also show thermochromic photoluminescent liquid crystals based on origo-(p-phenylenevinylene) and anthracene moieties and a thermochromic photoluminescent metallocomplex.

  17. Probing the Sophisticated Synergistic Allosteric Regulation of Aromatic Amino Acid Biosynthesis in Mycobacterium tuberculosis Using ᴅ-Amino Acids

    PubMed Central

    Reichau, Sebastian; Blackmore, Nicola J.; Jiao, Wanting; Parker, Emily J.

    2016-01-01

    Chirality plays a major role in recognition and interaction of biologically important molecules. The enzyme 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS) is the first enzyme of the shikimate pathway, which is responsible for the synthesis of aromatic amino acids in bacteria and plants, and a potential target for the development of antibiotics and herbicides. DAH7PS from Mycobacterium tuberculosis (MtuDAH7PS) displays an unprecedented complexity of allosteric regulation, with three interdependent allosteric binding sites and a ternary allosteric response to combinations of the aromatic amino acids l-Trp, l-Phe and l-Tyr. In order to further investigate the intricacies of this system and identify key residues in the allosteric network of MtuDAH7PS, we studied the interaction of MtuDAH7PS with aromatic amino acids that bear the non-natural d-configuration, and showed that the d-amino acids do not elicit an allosteric response. We investigated the binding mode of d-amino acids using X-ray crystallography, site directed mutagenesis and isothermal titration calorimetry. Key differences in the binding mode were identified: in the Phe site, a hydrogen bond between the amino group of the allosteric ligands to the side chain of Asn175 is not established due to the inverted configuration of the ligands. In the Trp site, d-Trp forms no interaction with the main chain carbonyl group of Thr240 and less favourable interactions with Asn237 when compared to the l-Trp binding mode. Investigation of the MtuDAH7PSN175A variant further supports the hypothesis that the lack of key interactions in the binding mode of the aromatic d-amino acids are responsible for the absence of an allosteric response, which gives further insight into which residues of MtuDAH7PS play a key role in the transduction of the allosteric signal. PMID:27128682

  18. Probing the Sophisticated Synergistic Allosteric Regulation of Aromatic Amino Acid Biosynthesis in Mycobacterium tuberculosis Using ᴅ-Amino Acids.

    PubMed

    Reichau, Sebastian; Blackmore, Nicola J; Jiao, Wanting; Parker, Emily J

    2016-01-01

    Chirality plays a major role in recognition and interaction of biologically important molecules. The enzyme 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS) is the first enzyme of the shikimate pathway, which is responsible for the synthesis of aromatic amino acids in bacteria and plants, and a potential target for the development of antibiotics and herbicides. DAH7PS from Mycobacterium tuberculosis (MtuDAH7PS) displays an unprecedented complexity of allosteric regulation, with three interdependent allosteric binding sites and a ternary allosteric response to combinations of the aromatic amino acids l-Trp, l-Phe and l-Tyr. In order to further investigate the intricacies of this system and identify key residues in the allosteric network of MtuDAH7PS, we studied the interaction of MtuDAH7PS with aromatic amino acids that bear the non-natural d-configuration, and showed that the d-amino acids do not elicit an allosteric response. We investigated the binding mode of d-amino acids using X-ray crystallography, site directed mutagenesis and isothermal titration calorimetry. Key differences in the binding mode were identified: in the Phe site, a hydrogen bond between the amino group of the allosteric ligands to the side chain of Asn175 is not established due to the inverted configuration of the ligands. In the Trp site, d-Trp forms no interaction with the main chain carbonyl group of Thr240 and less favourable interactions with Asn237 when compared to the l-Trp binding mode. Investigation of the MtuDAH7PSN175A variant further supports the hypothesis that the lack of key interactions in the binding mode of the aromatic d-amino acids are responsible for the absence of an allosteric response, which gives further insight into which residues of MtuDAH7PS play a key role in the transduction of the allosteric signal.

  19. Probing Protein Structure by Amino Acid-Specific Covalent Labeling and Mass Spectrometry

    PubMed Central

    Mendoza, Vanessa Leah; Vachet, Richard W.

    2009-01-01

    For many years, amino acid-specific covalent labeling has been a valuable tool to study protein structure and protein interactions, especially for systems that are difficult to study by other means. These covalent labeling methods typically map protein structure and interactions by measuring the differential reactivity of amino acid side chains. The reactivity of amino acids in proteins generally depends on the accessibility of the side chain to the reagent, the inherent reactivity of the label and the reactivity of the amino acid side chain. Peptide mass mapping with ESI- or MALDI-MS and peptide sequencing with tandem MS are typically employed to identify modification sites to provide site-specific structural information. In this review, we describe the reagents that are most commonly used in these residue-specific modification reactions, details about the proper use of these covalent labeling reagents, and information about the specific biochemical problems that have been addressed with covalent labeling strategies. PMID:19016300

  20. Diverse Cd(II) compounds based on N-benzoyl-L-glutamic acid and N-donor ligands: Structures and photoluminescent properties

    SciTech Connect

    Ma, Ning; Guo, Wei-Ying; Song, Hui-Hua Yu, Hai-Tao

    2016-01-15

    Five new Cd(II) coordination polymers with N-benzoyl-L-glutamic acid (H{sub 2}bzgluO) and different N-donor ligands, [Cd(bzgluO)(2,2′-bipy)(H{sub 2}O)]{sub n} (1), [Cd(bzgluO)(2,4′-bipy){sub 2}(H{sub 2}O)·3H{sub 2}O]{sub n} (2), [Cd(bzgluO)(phen)·H{sub 2}O]{sub n} (3), [Cd(bzgluO)(4,4′-bipy)(H{sub 2}O)]{sub n} (4), [Cd(bzgluO)(bpp)(H{sub 2}O)·2H{sub 2}O]{sub n} (5) were synthesized (2,2′-bipy=2,2′-bipyridine, 2,4′-bipy=2,4′-bipyridine, phen=1,10-phenanthroline, 4,4′-bipy=4,4′-bipyridine, bpp=1,3-di(4-pyridyl)propane). Compounds 1–2 exhibit a 1D single-chain structure. Compound 1 generates a 2D supramolecular structure via π–π stacking and hydrogen bonding, 3D architecture of compound 2 is formed by hydrogen bonding. Compound 3 features a 1D double-chain structure, which are linked by π–π interactions into a 2D supramolecular layer. Compounds 4-5 display a 2D network structure. Neighboring layers of 4 are extended into a 3D supramolecular architecture through hydrogen bonding. The structural diversity of these compounds is attributed to the effect of ancillary N-donor ligands and coordination modes of H{sub 2}bzgluO. Luminescent properties of 1–5 were studied at room temperature. Circular dichroism of compounds 1, 2 and 5 were investigated. - Graphical abstract: Five new Cd(II) metal coordination compounds with H{sub 2}bzgluO and different N-donor ligands were synthesized and characterized. Compounds 1, 2 and 3 present 1D structures, compounds 4 and 5 display 2D networks. Results indicate that auxiliary ligands and coordination modes of H{sub 2}bzgluO play an important role in governing the formation of final frameworks, and the hydrogen-bonding and π–π stacking interactions contribute the formation of the diverse supramolecular architectures. Furthermore, the different crystal structures influence the emission spectra significantly. - Highlights: • It is rarely reported that complexes prepared with N-benzoyl-L-glutamic acid

  1. Photoluminescent 3D lanthanide-organic frameworks based on 2,5-dioxo-1,4-piperazinylbis(methylphosphonic) acid formed via in situ cyclodehydration of glyphosates.

    PubMed

    Zhou, Yunshan; Guo, Yan; Xu, Sheng; Zhang, Lijuan; Ahmad, Waqar; Shi, Zonghai

    2013-06-03

    Hydrothermal reactions of lanthanide nitrates with glyphosate have resulted three new isostructural 3D lanthanide-organic frameworks, Ln(NO3)(H2L) [Ln = Eu (1), Tb (2), Gd (3); H4L = 2,5-dioxo-1,4-piperazinylbis(methylphosphonic) acid], with good yields, where H4L as a new ligand was formed via in situ cyclodehydration of original ligand glyphosates during the hydrothermal reaction. The compounds were thoroughly characterized by IR, UV-vis, elemental analysis, single-crystal X-ray diffraction analysis, powder X-ray diffraction analysis, and thermogravimetric/differential thermal analysis (TG-DTA). Three compounds display 3D 6,6-connected open frameworks with 4(13)·6(2) topology possessing 1D channels in which NO3(-) anions act as troglodytes by chelating Ln(3+) centers. The TG-DTA study of the compounds showed remarkable thermal stability up to 380 °C. Under room temperature UV-light irradiation, the Eu(3+) and Tb(3+) compounds showed the corresponding characteristic Ln(3+) intra 4f(n) emission peaks. The triplet energy level (21882 cm(-1)) of the ligand (H4L) was determined from the emission spectrum of its Gd(3+) compound at 77 K. The emission lifetimes (1.54 ms of (5)D0 for compound 1 and 1.98 ms of (5)D4 for compound 2) and absolute emission quantum yields (10.1% for compound 1 and 5.9% for compound 2) were also determined.

  2. Probing Phosphorus Efficient Low Phytic Acid Content Soybean Genotypes with Phosphorus Starvation in Hydroponics Growth System.

    PubMed

    Kumar, Varun; Singh, Tiratha Raj; Hada, Alkesh; Jolly, Monica; Ganapathi, Andy; Sachdev, Archana

    2015-10-01

    Phosphorus is an essential nutrient required for soybean growth but is bound in phytic acid which causes negative effects on both the environment as well as the animal nutrition. Lowering of phytic acid levels is associated with reduced agronomic characteristics, and relatively little information is available on the response of soybean plants to phosphorus (P) starvation. In this study, we evaluated the effects of different P starvation concentrations on the phytic acid content, growth, and yield of seven mutant genotypes along with the unirradiated control, JS-335, in a hydroponics growth system. The low phytic acid containing mutant genotypes, IR-JS-101, IR-DS-118, and IR-V-101, showed a relatively high growth rate in low P concentration containing nutrient solution (2 μM), whereas the high P concentration (50 μM) favored the growth of IR-DS-111 and IR-DS-115 mutant genotypes containing moderate phytate levels. The mutant genotypes with high phytic acid content, IR-DS-122, IR-DS-114, and JS-335, responded well under P starvation and did not have any significant effect on the growth and yield of plants. Moreover, the reduction of P concentration in nutrient solution from 50 to 2 μM also reduced the phytic acid content in the seeds of all the soybean genotypes under study. The desirable agronomic performance of low phytic acid containing mutant genotype IR-DS-118 reported in this study suggested it to be a P-efficient genotype which could be considered for agricultural practices under P limiting soils.

  3. Boronic acids as probes for investigation of allosteric modulation of the chemokine receptor CXCR3.

    PubMed

    Bernat, Viachaslau; Admas, Tizita Haimanot; Brox, Regine; Heinemann, Frank W; Tschammer, Nuska

    2014-11-21

    The chemokine receptor CXCR3 is a G protein-coupled receptor, which conveys extracellular signals into cells by changing its conformation upon agonist binding. To facilitate the mechanistic understanding of allosteric modulation of CXCR3, we combined computational modeling with the synthesis of novel chemical tools containing boronic acid moiety, site-directed mutagenesis, and detailed functional characterization. The design of boronic acid derivatives was based on the predictions from homology modeling and docking. The choice of the boronic acid moiety was dictated by its unique ability to interact with proteins in a reversible covalent way, thereby influencing conformational dynamics of target biomolecules. During the synthesis of the library we have developed a novel approach for the purification of drug-like boronic acids. To validate the predicted binding mode and to identify amino acid residues responsible for the transduction of signal through CXCR3, we conducted a site-directed mutagenesis study. With the use of allosteric radioligand RAMX3 we were able to establish the existence of a second allosteric binding pocket in CXCR3, which enables different binding modes of structurally closely related allosteric modulators of CXCR3. We have also identified residues Trp109(2.60) and Lys300(7.35) inside the transmembrane bundle of the receptor as crucial for the regulation of the G protein activation. Furthermore, we report the boronic acid 14 as the first biased negative allosteric modulator of the receptor. Overall, our data demonstrate that boronic acid derivatives represent an outstanding tool for determination of key receptor-ligand interactions and induction of ligand-biased signaling.

  4. Array of nucleic acid probes on biological chips for diagnosis of HIV and methods of using the same

    DOEpatents

    Chee, Mark; Gingeras, Thomas R.; Fodor, Stephen P. A.; Hubble, Earl A.; Morris, MacDonald S.

    1999-01-19

    The invention provides an array of oligonucleotide probes immobilized on a solid support for analysis of a target sequence from a human immunodeficiency virus. The array comprises at least four sets of oligonucleotide probes 9 to 21 nucleotides in length. A first probe set has a probe corresponding to each nucleotide in a reference sequence from a human immunodeficiency virus. A probe is related to its corresponding nucleotide by being exactly complementary to a subsequence of the reference sequence that includes the corresponding nucleotide. Thus, each probe has a position, designated an interrogation position, that is occupied by a complementary nucleotide to the corresponding nucleotide. The three additional probe sets each have a corresponding probe for each probe in the first probe set. Thus, for each nucleotide in the reference sequence, there are four corresponding probes, one from each of the probe sets. The three corresponding probes in the three additional probe sets are identical to the corresponding probe from the first probe or a subsequence thereof that includes the interrogation position, except that the interrogation position is occupied by a different nucleotide in each of the four corresponding probes.

  5. d-Amino Acid Probes for Penicillin Binding Protein-based Bacterial Surface Labeling*

    PubMed Central

    Fura, Jonathan M.; Kearns, Daniel; Pires, Marcos M.

    2015-01-01

    Peptidoglycan is an essential and highly conserved mesh structure that surrounds bacterial cells. It plays a critical role in retaining a defined cell shape, and, in the case of pathogenic Gram-positive bacteria, it lies at the interface between bacterial cells and the host organism. Intriguingly, bacteria can metabolically incorporate unnatural d-amino acids into the peptidoglycan stem peptide directly from the surrounding medium, a process mediated by penicillin binding proteins (PBPs). Metabolic peptidoglycan remodeling via unnatural d-amino acids has provided unique insights into peptidoglycan biosynthesis of live bacteria and has also served as the basis of a synthetic immunology strategy with potential therapeutic implications. A striking feature of this process is the vast promiscuity displayed by PBPs in tolerating entirely unnatural side chains. However, the chemical space and physical features of this side chain promiscuity have not been determined systematically. In this report, we designed and synthesized a library of variants displaying diverse side chains to comprehensively establish the tolerability of unnatural d-amino acids by PBPs in both Gram-positive and Gram-negative organisms. In addition, nine Bacillus subtilis PBP-null mutants were evaluated with the goal of identifying a potential primary PBP responsible for unnatural d-amino acid incorporation and gaining insights into the temporal control of PBP activity. We empirically established the scope of physical parameters that govern the metabolic incorporation of unnatural d-amino acids into bacterial peptidoglycan. PMID:26499795

  6. Ninhydrin-sodium molybdate chromogenic analytical probe for the assay of amino acids and proteins.

    PubMed

    Anantharaman, Shivakumar; Padmarajaiah, Nagaraja; Al-Tayar, Naef Ghllab Saeed; Shrestha, Ashwinee Kumar

    2017-02-15

    A sensitive method has been proposed for the quantification of amino acids and proteins using ninhydrin and sodium molybdate as chromogenic substrates in citrate buffer of pH5.6. A weak molybdate-hydrindantin complex plays the role in the formation of Ruhemann's purple. The linear response for the amino acid, amino acid mixture and Bovine serum albumin is between 0.999 and 66.80μM, 1.52 and 38μM and 5 and 100μg/L, respectively. The molar absorptivity of the individual amino acid by the proposed reaction extends from 0.58×10(4) to 2.86×10(4)M(-1)cm(-1). The linearity equations for the proposed ninhydrin-molybdate for amino acid mixture is Abs=0.021×Conc (μM)-0.002. The applicability of the proposed method has been justified in food and biological samples in conjunction with Kjeldahl method.

  7. Ninhydrin-sodium molybdate chromogenic analytical probe for the assay of amino acids and proteins

    NASA Astrophysics Data System (ADS)

    Anantharaman, Shivakumar; Padmarajaiah, Nagaraja; Al-Tayar, Naef Ghllab Saeed; Shrestha, Ashwinee Kumar

    2017-02-01

    A sensitive method has been proposed for the quantification of amino acids and proteins using ninhydrin and sodium molybdate as chromogenic substrates in citrate buffer of pH 5.6. A weak molybdate-hydrindantin complex plays the role in the formation of Ruhemann's purple. The linear response for the amino acid, amino acid mixture and Bovine serum albumin is between 0.999 and 66.80 μM, 1.52 and 38 μM and 5 and 100 μg/L, respectively. The molar absorptivity of the individual amino acid by the proposed reaction extends from 0.58 × 104 to 2.86 × 104 M- 1 cm- 1. The linearity equations for the proposed ninhydrin-molybdate for amino acid mixture is Abs = 0.021 × Conc (μM) - 0.002. The applicability of the proposed method has been justified in food and biological samples in conjunction with Kjeldahl method.

  8. Proteomic-based stable isotope probing reveals taxonomically Distinct Patterns in Amino Acid Assimilation by Coastal Marine Bacterioplankton

    SciTech Connect

    Bryson, Samuel; Li, Zhou; Pett-Ridge, Jennifer; Robert L. Hettich; Mayali, Xavier; Pan, Chongle; Mueller, Ryan S.

    2016-04-26

    Heterotrophic marine bacterioplankton are a critical component of the carbon cycle, processing nearly a quarter of annual global primary production, yet defining how substrate utilization preferences and resource partitioning structure these microbial communities remains a challenge. In this study, we utilized proteomics-based stable isotope probing (proteomic SIP) to characterize the assimilation of amino acids by coastal marine bacterioplankton populations. We incubated microcosms of seawater collected from Newport, OR and Monterey Bay, CA with 1 M 13C-amino acids for 15 and 32 hours. Subsequent analysis of 13C incorporation into protein biomass quantified the frequency and extent of isotope enrichment for identified proteins. Using these metrics we tested whether amino acid assimilation patterns were different for specific bacterioplankton populations. Proteins associated with Rhodobacterales and Alteromonadales tended to have a significantly high number of tandem mass spectra from 13C-enriched peptides, while Flavobacteriales and SAR11 proteins generally had significantly low numbers of 13C-enriched spectra. Rhodobacterales proteins associated with amino acid transport and metabolism had an increased frequency of 13C-enriched spectra at time-point 2, while Alteromonadales ribosomal proteins were 13C- enriched across time-points. Overall, proteomic SIP facilitated quantitative comparisons of dissolved free amino acids assimilation by specific taxa, both between sympatric populations and between protein functional groups within discrete populations, allowing an unprecedented examination of population-level metabolic responses to resource acquisition in complex microbial communities.

  9. Label-free electronic probing of nucleic acids and proteins at the nanoscale using the nanoneedle biosensor

    PubMed Central

    Esfandyarpour, Rahim; Javanmard, Mehdi; Koochak, Zahra; Esfandyarpour, Hesaam; Harris, James S.; Davis, Ronald W.

    2013-01-01

    Detection of proteins and nucleic acids is dominantly performed using optical fluorescence based techniques, which are more costly and timely than electrical detection due to the need for expensive and bulky optical equipment and the process of fluorescent tagging. In this paper, we discuss our study of the electrical properties of nucleic acids and proteins at the nanoscale using a nanoelectronic probe we have developed, which we refer to as the Nanoneedle biosensor. The nanoneedle consists of four thin film layers: a conductive layer at the bottom acting as an electrode, an oxide layer on top, and another conductive layer on top of that, with a protective oxide above. The presence of proteins and nucleic acids near the tip results in a decrease in impedance across the sensing electrodes. There are three basic mechanisms behind the electrical response of DNA and protein molecules in solution under an applied alternating electrical field. The first change stems from modulation of the relative permittivity at the interface. The second mechanism is the formation and relaxation of the induced dipole moment. The third mechanism is the tunneling of electrons through the biomolecules. The results presented in this paper can be extended to develop low cost point-of-care diagnostic assays for the clinical setting. PMID:24404047

  10. Novel emissive bio-inspired non-proteinogenic coumarin-alanine amino acid: fluorescent probe for polyfunctional systems.

    PubMed

    Oliveira, Elisabete; Capelo, José Luis; Lima, João Carlos; Lodeiro, Carlos

    2012-10-01

    Two new bio-inspired non-proteinogenic compounds L1 and L2, containing coumarin and/or acridine chromophores and bearing as spacer an alanine amino acid were successfully synthesized and fully characterized by elemental analysis, (1)H and (13)C NMR, infrared spectroscopy (KBr discs), melting point, ESI-TOF (electrospray ionization-time of flight-mass), UV-vis absorption and emission spectroscopy, fluorescence quantum yields and lifetime measurements. A relative fluorescence quantum yield of 0.02 was determined for both compounds. In L2 the presence of an intramolecular energy transfer from the coumarin to the acridine unit was observed. L1 and L2 are quite sensitive to the basicity of the environment. At alkaline values both compounds show a strong quenching in the fluorescence emission, attributed to the photoinduced electron transfer (PET). However, both deprotonated forms recover the emission with the addition of Zn(2+), Cd(2+) and Al(3+) metal ions. As multifunctional emissive probes, the titration of L1 and L2 with lanthanides (III), Eu(3+) and Tb(3+) was also explored as new visible bio-probes in the absence and in the presence of liposomes. In a liposomal environment a lower energy transfer was observed.

  11. Identification and quantification of acetic acid bacteria in wine and vinegar by TaqMan-MGB probes.

    PubMed

    Torija, M J; Mateo, E; Guillamón, J M; Mas, A

    2010-04-01

    A Real-Time PCR (RT-PCR) assay was developed using TaqMan minor groove binder (MGB) probes for the specific detection and quantification of five acetic acid bacteria (AAB) species (Acetobacter pasteurianus, Acetobacter aceti, Gluconacetobacter hansenii, Gluconacetobacter europaeus and Gluconobacter oxydans) in wine and vinegar. The primers and probes, designed from the 16S rRNA gene, showed good specificity with the target AAB species. The technique was tested on AAB grown in glucose medium (GY) and inoculated samples of red wine and wine vinegar. Standard curves were constructed with the five target species in all these matrices. Quantification was linear over at least 5 log units using both serial dilution of purified DNA and cells. When this technique was tested in GY medium and inoculated matrices, at least 10(2)-10(3) cells/ml were detected. To quantify low populations of AAB in microbiologically complex samples, a PCR enrichment including part of the 16S-23S rRNA gene ITS region was needed to increase the amount of target DNA compared to non-target DNA. The RT-PCR assay used in this study is a reliable, specific and fast method for quantifying these five AAB species in wine and vinegar.

  12. Phenylboronic acid-based (19)F MRI probe for the detection and imaging of hydrogen peroxide utilizing its large chemical-shift change.

    PubMed

    Nonaka, Hiroshi; An, Qi; Sugihara, Fuminori; Doura, Tomohiro; Tsuchiya, Akira; Yoshioka, Yoshichika; Sando, Shinsuke

    2015-01-01

    Herein, we report on a new (19)F MRI probe for the detection and imaging of H2O2. Our designed 2-fluorophenylboronic acid-based (19)F probe promptly reacted with H2O2 to produce 2-fluorophenol via boronic acid oxidation. The accompanying (19)F chemical-shift change reached 31 ppm under our experimental conditions. Such a large chemical-shift change allowed for the imaging of H2O2 by (19)F chemical-shift-selective MRI.

  13. Ancillary ligand-assisted assembly of C{sub 3}-symmetric 4,4′,4″-nitrilotribenzoic acid with divalent Zn{sup 2+} ions: Syntheses, topological structures, and photoluminescence properties

    SciTech Connect

    Cui, Li-Ting; Niu, Yan-Fei; Han, Jie; Zhao, Xiao-Li

    2015-07-15

    4,4′,4″-nitrilotribenzoic acid (H{sub 3}L), a C{sub 3}-symmetric ligand, was found to self-assemble into two polymorphs driven by intermolecular hydrogen-bonding interactions. Reactions of this ligand with Zn{sup 2+} under solvothermal conditions resulted in four new coordination polymers bearing interesting structural motifs: [Zn{sub 2}(L){sub 2}(py){sub 2}]·2(H{sub 2}NMe{sub 2}){sup +}·DMF·2H{sub 2}O (1), [Zn{sub 2}(L)(H{sub 2}L)(bipy)]·1.5H{sub 2}O·Guest (2), [Zn{sub 2}(L){sub 2}(bipy)]·2(H{sub 2}NMe{sub 2}){sup +}·2DMF (3), and [Zn{sub 3}(L){sub 2}(bpa)]·2H{sub 2}O·Guest (4) (H{sub 3}L=4,4′,4′′-nitrilotribenzoic acid, DMF=dimethylformamide, py=pyridine, bipy=4,4′-bipyridine, bpa=1,2-bis(4-pyridyl)diazene). Single-crystal structural analysis revealed that compound 1 exhibits a rare example of twofold interpenetrating anionic 3D (3,3)-net framework containing helical channels, whereas in 2, the 3D pillar-layer structure generated from bipy-pillared Zn{sub 2}(L)(H{sub 2}L) layer is further reinforced by intermolecular hydrogen bonding among pairs of free –COOH units. Compound 3 shows an interesting entangled architecture of 2D→3D parallel polycatenation consisting five-coordinated Zn{sup 2+} ions. Compound 4 displays a 3D pillar-layer framework with trimeric Zn{sub 3}(CO{sub 2}){sub 6} serving as secondary building unit (SBU). The syntheses, structures, thermal stabilities, powder X-ray diffractions and solid-state photoluminescence properties for these crystalline materials have been carried out. In addition, supramolecular assembly of H{sub 3}L under solvothermal conditions will also be addressed. - Graphical abstract: Supramolecular assembly of 4,4′,4′′-nitrilotribenzoic acid and its ligand behavior toward Zn{sup 2+} were investigated, which exhibit two polymorphs of the free acid and four metal coordination polymers bearing interesting structural motifs. - Highlights: • Two polymorphs of H{sub 3}L showing different hydrogen

  14. Energetics of side-chain snorkeling in transmembrane helices probed by nonproteinogenic amino acids.

    PubMed

    Öjemalm, Karin; Higuchi, Takashi; Lara, Patricia; Lindahl, Erik; Suga, Hiroaki; von Heijne, Gunnar

    2016-09-20

    Cotranslational translocon-mediated insertion of membrane proteins into the endoplasmic reticulum is a key process in membrane protein biogenesis. Although the mechanism is understood in outline, quantitative data on the energetics of the process is scarce. Here, we have measured the effect on membrane integration efficiency of nonproteinogenic analogs of the positively charged amino acids arginine and lysine incorporated into model transmembrane segments. We provide estimates of the influence on the apparent free energy of membrane integration (ΔGapp) of "snorkeling" of charged amino acids toward the lipid-water interface, and of charge neutralization. We further determine the effect of fluorine atoms and backbone hydrogen bonds (H-bonds) on ΔGapp These results help establish a quantitative basis for our understanding of membrane protein assembly in eukaryotic cells.

  15. Energetics of side-chain snorkeling in transmembrane helices probed by nonproteinogenic amino acids

    PubMed Central

    Öjemalm, Karin; Higuchi, Takashi; Lara, Patricia; Lindahl, Erik; Suga, Hiroaki

    2016-01-01

    Cotranslational translocon-mediated insertion of membrane proteins into the endoplasmic reticulum is a key process in membrane protein biogenesis. Although the mechanism is understood in outline, quantitative data on the energetics of the process is scarce. Here, we have measured the effect on membrane integration efficiency of nonproteinogenic analogs of the positively charged amino acids arginine and lysine incorporated into model transmembrane segments. We provide estimates of the influence on the apparent free energy of membrane integration (ΔGapp) of “snorkeling” of charged amino acids toward the lipid–water interface, and of charge neutralization. We further determine the effect of fluorine atoms and backbone hydrogen bonds (H-bonds) on ΔGapp. These results help establish a quantitative basis for our understanding of membrane protein assembly in eukaryotic cells. PMID:27601675

  16. Near-infrared spectroscopy (NIRS) with a fibre-optic probe for the prediction of the amino acid composition in animal feeds.

    PubMed

    González-Martín, Inmaculada; Alvarez-García, Noelia; González-Cabrera, José Miguel

    2006-05-15

    The amino acids alanine, aspartic acid, glutamic acid, glycine, phenylalanine, valine, lysine, proline, and tyrosine present in feeds with different textures (blocks, tablets, granules and flour (meal) and used in different stages of animal feeding regimes (lactation, growth, maintenance, etc.) were analysed using near-infrared reflectance spectroscopy (NIRS) technology together with a remote reflectance fibre-optic probe. The method allows immediate control of the animal feeds without prior sample treatment or destruction through direct application of the fibre-optic probe on the sample. The regression method used was Modified Partial Least Squares (MPLS). The equations developed to determine the amino acid contents of the feeds afforded high values for the RSQ coefficient (0.814-0.963) in all the amino acids with the exception of lysine (0.687). The statistical prediction descriptors SEP, SEP(C) (with values between 0.134 for valine and 0.015 for aspartic acid) and bias indicated that the amino acid values in feeds predicted with NIRS with a fibre optic probe are comparable to those obtained with the chemical ion-exchange HPLC method.

  17. Amino acid-based ionic liquids: using XPS to probe the electronic environment via binding energies.

    PubMed

    Hurisso, Bitu Birru; Lovelock, Kevin R J; Licence, Peter

    2011-10-21

    Here we report the synthesis and characterisation by X-ray photoelectron spectroscopy (XPS) of eight high purity amino acid-based ionic liquids (AAILs), each containing the 1-octyl-3-methylimidazolium, [C(8)C(1)Im](+), as a standard reference cation. All expected elements were observed and the electronic environments of these elements identified. A fitting model for the carbon 1s region of the AAILs is reported; the C aliphatic component of the cation was used as an internal reference to obtain a series of accurate and reproducible binding energies. Comparisons are made between XP spectra of the eight AAILs and selected non-functionalised ionic liquids. 1-octyl-3-methylimidazolium acetate was also studied as a model of the carboxyl containing amino acid anion. The influence of anionic substituent groups on the measured binding energies of all elements is presented, and communication between anion and cation is investigated. This data is interpreted in terms of hard and soft anions and compared to the Kamlet-Taft hydrogen bond acceptor ability, β, for the ionic liquids. A linear correlation is presented which suggests that the functional side chain, or R group, of the amino acid has little impact upon the electronic environment of the charge-bearing moieties within the anions and cations studied.

  18. Re-engineering of CYP2C9 to probe acid-base substrate selectivity.

    PubMed

    Tai, Guoying; Dickmann, Leslie J; Matovic, Nicholas; DeVoss, James J; Gillam, Elizabeth M J; Rettie, Allan E

    2008-10-01

    A common feature of many CYP2C9 ligands is their weak acidity. As revealed by crystallography, the structural basis for this behavior involves a charge-pairing interaction between an anionic moiety on the substrate and an active site R108 residue. In the present study we attempted to re-engineer CYP2C9 to better accept basic ligands by charge reversal at this key residue. We expressed and purified the R108E and R108E/D293N mutants and compared their ability with that of native CYP2C9 to interact with (S)-warfarin, diclofenac, pyrene, propranolol, and ibuprofen amine. As expected, the R108E mutant maintained all the native enzyme's pyrene 1-hydroxylation activity, but catalytic activity toward diclofenac and (S)-warfarin was abrogated. In contrast, the double mutant displayed much less selectivity in its behavior toward these control ligands. Neither of the mutants displayed significant enhancement of propranolol metabolism, and all three preparations exhibited a type II (inhibitor) rather than type I (substrate) spectrum with ibuprofen amine, although binding became progressively weaker with the single and double mutants. Collectively, these data underscore the importance of the amino acid at position 108 in the acid substrate selectivity of CYP2C9, highlight the accommodating nature of the CYP2C9 active site, and provide a cautionary note regarding facile re-engineering of these complex cytochrome P450 active sites.

  19. Using modern tools to probe the structure-function relationship of fatty acid synthases

    PubMed Central

    Burkart, Michael D.

    2015-01-01

    Fatty acid biosynthesis is essential to life and represents one of the most conserved pathways in Nature, preserving the same handful of chemical reactions over all species. Recent interest in the molecular details of the de novo fatty acid synthase (FAS) has been heightened by demand for renewable fuels and the emergence of multidrug resistant bacterial strains. Central to FAS is the acyl carrier protein (ACP), a protein chaperone that shuttles the growing acyl chain between catalytic enzymes within the FAS. Human efforts to alter fatty acid biosynthesis for oil production, chemical feedstock or antimicrobial purposes has been met with limited success in part due to a lack of detailed molecular information behind the ACP-partner protein interactions inherent to the pathway. This review will focus on recently developed tools for the modification of ACP and analysis of protein-protein interactions, such as mechanism-based crosslinking, and the studies exploiting them. Discussion specific to each enzymatic domain focuses first on mechanism and known inhibitors, followed by available structures and known interactions with ACP. While significant unknowns remain, new understandings into the intricacies of FAS point to future advances in manipulating this complex molecular factory. PMID:25676190

  20. Vanadium-fulvic acid chemistry: conformational and binding studies by electron spin probe techniques

    NASA Astrophysics Data System (ADS)

    Templeton, G. Daniel, III; Chasteen, N. Dennis

    1980-05-01

    Two fractions of soil fulvic acid (FA) were separated by gel filtration chromatography. An observed increase in volume of the heavier fraction (FA I) with increasing pH was attributed to aggregation, intramolecular negative charge repulsions and the rupture of hydrogen bonds, which control molecular conformation. Optical absorption properties and elemental analyses of both fractions were determined. The stability constants and stoichiometries of FA complexes with vanadyl, VO 2+, at pH 5.0 and ionic strength of 0.04 M were measured by electron paramagnetic resonance (EPR) spectroscopy. EPR spectra of model VO 2+ complexes with phthalic and salicylic acids, which are the probable functional groups present in FA, are identical to those of the VO 2+-FA complexes. Aggregation of FA I occurs in the presence of VO 2+ to form a complex that can be approximated as '(VO) 2(FA I) 6'. The average site distance between vanadyl ions in this complex is shown to be greater than 1.2 nm. EPR parameters for FA I suggest binding by carboxylate groups. These parameters are compared with those of other vanadyl complexes with fulvic and humic acids reported by others. Reduction of VO 3- to VO 2+ by these materials is discussed.

  1. Radioluminescence and photoluminescence of Th:CaF2 crystals

    NASA Astrophysics Data System (ADS)

    Stellmer, Simon; Schreitl, Matthias; Schumm, Thorsten

    2015-10-01

    We study thorium-doped CaF2 crystals as a possible platform for optical spectroscopy of the 229Th nuclear isomer transition. We anticipate two major sources of background signal that might cover the nuclear spectroscopy signal: VUV-photoluminescence, caused by the probe light, and radioluminescence, caused by the radioactive decay of 229Th and its daughters. We find a rich photoluminescence spectrum at wavelengths above 260 nm, and radioluminescence emission above 220 nm. This is very promising, as fluorescence originating from the isomer transition, predicted at a wavelength shorter than 200 nm, could be filtered spectrally from the crystal luminescence. Furthermore, we investigate the temperature-dependent decay time of the luminescence, as well as thermoluminescence properties. Our findings allow for an immediate optimization of spectroscopy protocols for both the initial search for the nuclear transition using synchrotron radiation, as well as future optical clock operation with narrow-linewidth lasers.

  2. Radioluminescence and photoluminescence of Th:CaF2 crystals

    PubMed Central

    Stellmer, Simon; Schreitl, Matthias; Schumm, Thorsten

    2015-01-01

    We study thorium-doped CaF2 crystals as a possible platform for optical spectroscopy of the 229Th nuclear isomer transition. We anticipate two major sources of background signal that might cover the nuclear spectroscopy signal: VUV-photoluminescence, caused by the probe light, and radioluminescence, caused by the radioactive decay of 229Th and its daughters. We find a rich photoluminescence spectrum at wavelengths above 260 nm, and radioluminescence emission above 220 nm. This is very promising, as fluorescence originating from the isomer transition, predicted at a wavelength shorter than 200 nm, could be filtered spectrally from the crystal luminescence. Furthermore, we investigate the temperature-dependent decay time of the luminescence, as well as thermoluminescence properties. Our findings allow for an immediate optimization of spectroscopy protocols for both the initial search for the nuclear transition using synchrotron radiation, as well as future optical clock operation with narrow-linewidth lasers. PMID:26502749

  3. Locked Nucleic Acid Probe-Based Real-Time PCR Assay for the Rapid Detection of Rifampin-Resistant Mycobacterium tuberculosis.

    PubMed

    Zhao, Yong; Li, Guilian; Sun, Chongyun; Li, Chao; Wang, Xiaochen; Liu, Haican; Zhang, Pingping; Zhao, Xiuqin; Wang, Xinrui; Jiang, Yi; Yang, Ruifu; Wan, Kanglin; Zhou, Lei

    2015-01-01

    Drug-resistant Mycobacterium tuberculosis can be rapidly diagnosed through nucleic acid amplification techniques by analyzing the variations in the associated gene sequences. In the present study, a locked nucleic acid (LNA) probe-based real-time PCR assay was developed to identify the mutations in the rpoB gene associated with rifampin (RFP) resistance in M. tuberculosis. Six LNA probes with the discrimination capability of one-base mismatch were designed to monitor the 23 most frequent rpoB mutations. The target mutations were identified using the probes in a "probe dropout" manner (quantification cycle = 0); thus, the proposed technique exhibited superiority in mutation detection. The LNA probe-based real-time PCR assay was developed in a two-tube format with three LNA probes and one internal amplification control probe in each tube. The assay showed excellent specificity to M. tuberculosis with or without RFP resistance by evaluating 12 strains of common non-tuberculosis mycobacteria. The limit of detection of M. tuberculosis was 10 genomic equivalents (GE)/reaction by further introducing a nested PCR method. In a blind validation of 154 clinical mycobacterium isolates, 142/142 (100%) were correctly detected through the assay. Of these isolates, 88/88 (100%) were determined as RFP susceptible and 52/54 (96.3%) were characterized as RFP resistant. Two unrecognized RFP-resistant strains were sequenced and were found to contain mutations outside the range of the 23 mutation targets. In conclusion, this study established a sensitive, accurate, and low-cost LNA probe-based assay suitable for a four-multiplexing real-time PCR instrument. The proposed method can be used to diagnose RFP-resistant tuberculosis in clinical laboratories.

  4. Fatty acid binding sites of human and bovine albumins: Differences observed by spin probe ESR

    NASA Astrophysics Data System (ADS)

    Muravsky, Vladimir; Gurachevskaya, Tatjana; Berezenko, Stephen; Schnurr, Kerstin; Gurachevsky, Andrey

    2009-09-01

    Bovine and human serum albumins and recombinant human albumin, all non-covalently complexed with 5- and 16-doxyl stearic acids, were investigated by ESR spectroscopy in solution over a range of pH values (5.5-8.0) and temperatures (25-50 °C), with respect to the allocation and mobility of fatty acid (FA) molecules bound to the proteins and conformation of the binding sites. In all proteins bound FA undergo a permanent intra-albumin migration between the binding sites and inter-domain residence. Nature identity of the recombinant human albumin to its serum-derived analog was observed. However, the binding sites of bovine albumin appeared shorter in length and wider in diameter than those of human albumin. Presumably, less tightly folded domains in bovine albumin allow better penetration of water molecules in the interior of the globule that resulted in higher activation energy of FA dissociation from the binding site. Thus, the sensitive technique based on ESR non-covalent spin labeling allowed quantitative analysis and reliable comparison of the fine features of binding proteins.

  5. Probing the transition state for nucleic acid hybridization using phi-value analysis.

    PubMed

    Kim, Jandi; Shin, Jong-Shik

    2010-04-27

    Genetic regulation by noncoding RNA elements such as microRNA and small interfering RNA (siRNA) involves hybridization of a short single-stranded RNA with a complementary segment in a target mRNA. The physical basis of the hybridization process between the structured nucleic acids is not well understood primarily because of the lack of information about the transition-state structure. Here we use transition-state theory, inspired by phi-value analysis in protein folding studies, to provide quantitative analysis of the relationship between changes in the secondary structure stability and the activation free energy. Time course monitoring of the hybridization reaction was performed under pseudo-steady-state conditions using a single fluorophore. The phi-value analysis indicates that the native secondary structure remains intact in the transition state. The nativelike transition state was confirmed via examination of the salt dependence of the hybridization kinetics, indicating that the number of sodium ions associated with the transition state was not substantially affected by changes in the native secondary structure. These results propose that hybridization between structured nucleic acids undergoes a transition state leading to formation of a nucleation complex and then is followed by sequential displacement of preexisting base pairings involving successive small energy barriers. The proposed mechanism might provide new insight into physical processes during small RNA-mediated gene silencing, which is essential to selection of a target mRNA segment for siRNA design.

  6. 3-D silver(I)-lanthanide(III) heterometallic-organic frameworks constructed from 2,2'-bipyridine-3,3'-dicarboxylic acid: synthesis, structure, photoluminescence, and their remarkable thermostability.

    PubMed

    Zhou, Yunshan; Li, Xiaomin; Zhang, Lijuan; Guo, Yan; Shi, Zonghai

    2014-04-07

    A new family of silver(I)-lanthanide(III) heterometallic-organic frameworks having the formula [AgLn(bpdc)2] (Ln = Eu (1), Tb (2), Sm (3), Dy (4), Y (5), Yb (6), Er (7), Ho (8); H2bpdc = 2,2'-bipyridine-3,3'-dicarboxylic acid), each of which crystallizes in the monoclinic space group C2/c with Z = 4, has been hydrothermally synthesized. The compounds were characterized by means of IR, elemental analysis, thermogravimetric-differential thermal analysis, and powder X-ray diffraction (XRD), wherein compounds 1, 2, and 4-8 were structurally characterized. The powder XRD and single-crystal structures of the title compounds indicate that all the compounds are isostructural and feature a three-dimensional (3-D) open framework. In the structures of the compounds, bpdc(2-) ligands link Ln(3+) through their carboxylic groups, resulting in the formation of a one-dimensional {Ln(bpdc)2}n infinite chain along the c direction. The adjacent chains are then connected to each other through the coordination interaction between Ag(+) and the pyridyl N atoms of bpdc(2-) ligands from the chains, resulting in a 3-D (2,4,6)-connected open framework with (4(11)·6(4))(4(3)·8(2)·10)(8)2 topology. The compounds show remarkable good thermally stability up to 370 °C because neither aquo ligands nor lattice water molecules exist in the composition of the compounds. The photoluminescent properties of compounds 1 and 2 were studied in detail. The energy level of the triplet states of the ligand H2bpdc 21,505 cm(-1) (465 nm) was determined based on the 77 K emission spectrum of the compound [Gd2(bpdc)3(phen)2(H2O)2]·6H2O 9. The (5)D0 and (5)D4 emission lifetimes (1.58 and 1.76 ms) and the overall quantum yields (21% and 22%) were determined for the compounds 1 and 2, respectively.

  7. Adaptation and validation of E-probe diagnostic nucleic acid analysis for detection of Escherichia coli O157:H7 in metagenomic data of complex food matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Foodborne pathogens are an increasing problem threatening the US food supply. The need for rapid sensitive diagnostic tools that can address multiple types and taxonomic classes of foodbourne pathogens is growing. This paper describes the adaptation of E-probe Diagnostic Nucleic acid Analysis (EDNA)...

  8. ESTIMATION OF BACTERIAL CELL NUMBERS IN HUMIC ACID-RICH SALT MARSH SEDIMENTS WITH PROBES DIRECTED TO 16S RIBOSOMAL DNA

    EPA Science Inventory

    The feasibility of using probes directed towards ribosomal DNAs (rDNAs) as a quantitative approach to estimating cell numbers was examined and applied to study the structure of a bacterial community in humic acid-rich salt marsh sediments. Hybridizations were performed with membr...

  9. Association of a cucumber mosaic virus strain with mosaic disease of banana, Musa paradisiaca--an evidence using immuno/nucleic acid probe.

    PubMed

    Srivastava, A; Raj, S K; Haq, Q M; Srivastava, K M; Singh, B P; Sane, P V

    1995-12-01

    Virus causing severe chlorosis/mosaic disease of banana was identified as a strain of cucumber mosaic virus (CMV). Association of CMV with the disease was established by Western immunoblot using polyclonal antibodies to CMV-T and slot blot hybridization with nucleic acid probe of CMV-P genome.

  10. New Real-Time PCR Assay Using Locked Nucleic Acid Probes To Assess Prevalence of ParC Mutations in Fluoroquinolone-Susceptible Streptococcus pneumoniae Isolates from France

    PubMed Central

    Decousser, Jean-Winoc; Methlouthi, Imen; Pina, Patrick; Collignon, Anne; Allouch, Pierre

    2006-01-01

    A real-time PCR assay with locked nucleic acid probes was developed to screen mutations at codons 79 and 83 of the Streptococcus pneumoniae parC gene. Only silent mutations were detected among 236 French invasive fluoroquinolone-susceptible strains. This test could be useful for some high-risk patients or in national surveys. PMID:16569894

  11. Systematic safety evaluation on photoluminescent carbon dots

    NASA Astrophysics Data System (ADS)

    Wang, Kan; Gao, Zhongcai; Gao, Guo; Wo, Yan; Wang, Yuxia; Shen, Guangxia; Cui, Daxiang

    2013-03-01

    Photoluminescent carbon dots (C-dots) were prepared using the improved nitric acid oxidation method. The C-dots were characterized by tapping-mode atomic force microscopy, and UV-vis absorption spectroscopy. The C-dots were subjected to systematic safety evaluation via acute toxicity, subacute toxicity, and genotoxicity experiments (including mouse bone marrow micronuclear test and Salmonella typhimurium mutagenicity test). The results showed that the C-dots were successfully prepared with good stability, high dispersibility, and water solubility. At all studied C-dot dosages, no significant toxic effect, i.e., no abnormality or lesion, was observed in the organs of the animals. Therefore, the C-dots are non-toxic to mice under any dose and have potential use in fluorescence imaging in vivo, tumor cell tracking, and others.

  12. ESA mission ROSETTA will probe for chirality of cometary amino acids.

    PubMed

    Thiemann, W H; Meierhenrich, U

    2001-01-01

    New crucial theoretical investigations on the origin of biomolecular chirality are reviewed briefly. With the goal to investigate these theories our team is going to perform the 'chirality-experiment' in the near future with cometary matter. In 2012 the robotical lander RoLand will detach from the orbiter of the ROSETTA spacecraft and set down on the surface of comet 46P/Wirtanen in order to separate and identify cometary organic compounds via GC-MS in situ. Chiral organics will be separated into their enantiomers by application of 3 capillary columns coated with different kinds of stationary phases. Non-volatile compounds like amino acids will be derivatized in especially developed gas phase alkylation steps avoiding reactions in the liquid phase. The results of these preliminary gas phase reactions are presented in this article.

  13. A chromo- and fluorogenic sensor for probing the cancer biomarker lysophosphatidic acid.

    PubMed

    Zhao, Wenwen; Liu, Weimin; Zhang, Wenjun; Zeng, Lintao; Fan, Zhiyuan; Wu, Jiasheng; Wang, Pengfei

    2012-04-21

    A novel chromo- and fluorogenic sensor, 4-(4-dimethylaminostyryl)-1-hexadecylpyridinium (DSHP) for lysophosphatidic acid (LPA) was successfully developed by incorporating a long alkyl chain into the cyanine molecule. DSHP shows excellent selectivity and high sensitivity towards LPA with a detection limit of about 7.09 × 10(-7) M based on electrostatic and hydrophobic interactions between the sensor and LPA. Upon addition of LPA ranging from 0 to 7.5 × 10(-4) M, DSHP displays an 'on-off-on' fluorescence response and obvious colour change. Good linear relationships between the fluorescence intensity and LPA concentrations were achieved in the fluorescence quenching ranges of 0-28 μM and 34-52 μM, which could be attributed to the combined effects of the photoinduced electron transfer and LPA-induced aggregation of the sensor molecules.

  14. Pharmacophore-based database mining for probing fragmental drug-likeness of diketo acid analogues.

    PubMed

    Bak, A; Magdziarz, T; Polanski, J

    2012-01-01

    A number of the structurally diverse chemical compounds with functional diketo acid (DKA) subunit(s) have been revealed by combined online and MoStBiodat 3D pharmacophore-guided ZINC and PubChem database screening. We used the structural data available from such screening to analyse the similarities of the compounds containing the DKA fragment. Generally, the analysis by principal component analysis and self-organizing neural network approaches reveals four families of compounds complying with the chemical constitution (aromatic, aliphatic) of the compounds. From a practical point of view, similar studies may reveal potential bioisosteres of known drugs, e.g. raltegravir/elvitegravir. In this context, it seems that mono-halogenated aryl substructures with para group show the closest similarity to these compounds, in contrast to structures where the aromatic ring is halogenated in both ortho- and para-locations.

  15. In vivo quantitative visualization of hypochlorous acid in the liver using a novel selective two-photon fluorescent probe

    NASA Astrophysics Data System (ADS)

    Wang, Haolu; Jayachandran, Aparna; Gravot, Germain; Liang, Xiaowen; Thorling, Camilla A.; Zhang, Run; Liu, Xin; Roberts, Michael S.

    2016-11-01

    Hypochlorous acid (HOCl) plays a vital role in physiological events and diseases. During hepatic ischemia-reperfusion (I/R) injury, HOCl is generated by neutrophils and diffuses into hepatocytes, causing oxidant stress-mediated injury. Although many probes have been developed to detect HOCl, most were difficult to be distinguished from endogenous fluorophores in intravital imaging and only can be employed under one-photon microscopy. A novel iridium(III) complex-based ferrocene dual-signaling chemosensor (Ir-Fc) was designed and synthesized. Ir-Fc exhibited a strong positive fluorescent response only in the presence of HOCl, whereas negligible fluorescent signals were observed upon the additions of other reactive oxygen/nitrogen species and metal ions. There was a good linear relationship between probe responsive fluorescent intensity and HOCl concentration. Ir-Fc was then intravenously injected into BALB/c mice at the final concentration of 50 μM and the mouse livers were imaged using multiphoton microscopy (MPM). In the I/R liver, reduced autofluorescence was detected by MPM, indicating the hepatocyte necrosis. Remarkable enhancement of red fluorescence was observed in hepatocytes with decreased autofluorescence, indicating the reaction of Ir-Fc with endogenous HOCl molecules. The cellular concentration of HOCl was first calculated based on the intensity of MPM images. No obvious toxic effects were observed in histological examination of major organs after Ir-Fc injection. In summary, Ir-Fc has low cytotoxicity, high specificity to HOCl, and rapid "off-on" fluorescence. It is suitable for dynamic quantitatively monitoring HOCl generation using MPM at the cellular level. This technique can be readily extended to examination of liver diseases and injury.

  16. A new method for ABO genotyping using fluorescence melting curve analysis based on peptide nucleic acid probes.

    PubMed

    Lee, Kyungmyung; Park, Hyun-Chul; An, Sanghyun; Ahn, Eu-Ree; Lee, Yang-Han; Kim, Mi-Jung; Lee, Eun-Jung; Park, Jae Sin; Jung, Jin Wook; Lim, Sikeun

    2015-09-01

    ABO genotyping has been routinely used to identify suspects or unknown remains in crime investigations. Probe-based fluorescence melting curve analysis (FMCA) is a powerful tool for mutation detection and is based on melting temperature shifts due to thermal denaturation. In the present study, we developed a new method for ABO genotyping using peptide nucleic acid (PNA) probe-based FMCA. This method allowed for the simultaneous detection of three single nucleotide polymorphism (SNP) sites in the ABO gene (nucleotide positions 261, 526, and 803) and the determination of 14 ABO genotypes (A/A, A/O01 or A/O02, A/O03, B/B, B/O01 or B/O02, B/O03, O01/O01 or O01/O02 or O02/O02, O01/O03 or O02/O03, O03/O03, A/B, cis-AB01/A, cis-AB01/B, cis-AB01/O01 or cis-AB01/O02, and cis-AB01/cis-AB01). Using this method, we analyzed 80 samples and successfully identified ABO genotypes (A/A [n=5], A/O01 or A/O02 [n=23], B/B [n=3], B/O01 or B/O02 [n=18], A/B [n=9], O01/O01 or O01/O02 or O02/O02 [n=20], cis-AB01/A [n=1], and cis-AB01/O01 or cis-AB01/O02 [n=1]). In addition, all steps in the method, including polymerase chain reaction, PNA probe hybridization, and FMCA, could be performed in one single closed tube in less than 3h. Since no processing or separation steps were required during analysis, this method was more convenient and rapid than traditional methods and reduced the risk of contamination. Thus, this method may be an effective and helpful tool in forensic investigations.

  17. New organically templated photoluminescence iodocuprates(I)

    SciTech Connect

    Hou Qin; Zhao Jinjing; Zhao Tianqi; Jin Juan; Yu Jiehui; Xu Jiqing

    2011-07-15

    Two types of organic cyclic aliphatic diamine molecules piperazine (pip) and 1,3-bis(4-piperidyl)propane (bpp) were used, respectively, to react with an inorganic mixture of CuI and KI in the acidic CH{sub 3}OH solutions under the solvothermal conditions, generating finally three new organically templated iodocuprates as 2-D layered [(Hpip)Cu{sub 3}I{sub 4}] 1, 1-D chained [tmpip][Cu{sub 2}I{sub 4}] 2 (tmpip=N,N,N',N'-tetramethylpiperazinium) and dinuclear [H{sub 2}bpp]{sub 2}[Cu{sub 2}I{sub 5}] I.2H{sub 2}O 3. Note that the templating agent tmpip{sup 2+} in compound 2 originated from the in situ N-alkylation reaction between the pip molecule and the methanol solvent. The photoluminescence analysis indicates that the title compounds emit the different lights: yellow for 1, blue for 2 and yellow-green for 3, respectively. - Graphical abstract: The solvothermal self-assemblies of CuI, KI and pip/bpp in acidic CH{sub 3}OH solutions created three iodocuprates 2-D layered [(Hpip)Cu{sub 3}I{sub 4}] 1, 1-D chained [tmpip][Cu{sub 2}I{sub 4}] 2 and dinuclear [H{sub 2}bpp]{sub 2}[Cu{sub 2}I{sub 5}] I.2H{sub 2}O 3. Highlights: > A new layered iodocuprate(I) with 20-membered rings was hydrothermally prepared. > A simple approach to prepare the new organic templating agent was reported. > Photoluminescence analysis indicates the emission for iodocuprate(I) is associated with the Cu...Cu interactions.

  18. On the cellular metabolism of the click chemistry probe 19-alkyne arachidonic acid.

    PubMed

    Robichaud, Philippe Pierre; Poirier, Samuel J; Boudreau, Luc H; Doiron, Jérémie A; Barnett, David A; Boilard, Eric; Surette, Marc E

    2016-10-01

    Alkyne and azide analogs of natural compounds that can be coupled to sensitive tags by click chemistry are powerful tools to study biological processes. Arachidonic acid (AA) is a FA precursor to biologically active compounds. 19-Alkyne-AA (AA-alk) is a sensitive clickable AA analog; however, its use as a surrogate to study AA metabolism requires further evaluation. In this study, AA-alk metabolism was compared with that of AA in human cells. Jurkat cell uptake of AA was 2-fold greater than that of AA-alk, but significantly more AA-Alk was elongated to 22:4. AA and AA-alk incorporation into and remodeling between phospholipid (PL) classes was identical indicating equivalent CoA-independent AA-PL remodeling. Platelets stimulated in the pre-sence of AA-alk synthesized significantly less 12-lipoxygenase (12-LOX) and cyclooxygenase products than in the presence of AA. Ionophore-stimulated neutrophils produced significantly more 5-LOX products in the presence of AA-alk than AA. Neutrophils stimulated with only exogenous AA-alk produced significantly less 5-LOX products compared with AA, and leukotriene B4 (LTB4)-alk was 12-fold less potent at stimulating neutrophil migration than LTB4, collectively indicative of weaker leukotriene B4 receptor 1 agonist activity of LTB4-alk. Overall, these results suggest that the use of AA-alk as a surrogate for the study of AA metabolism should be carried out with caution.

  19. Probing Gαi1 Protein Activation at Single Amino Acid Resolution

    PubMed Central

    Sun, Dawei; Maeda, Shoji; Matkovic, Milos; Mendieta, Sandro; Mayer, Daniel; Dawson, Roger; Schertler, Gebhard F.X.; Madan Babu, M.; Veprintsev, Dmitry B.

    2016-01-01

    We present comprehensive single amino acid resolution maps of the residues stabilising the human Gαi1 subunit in nucleotide- and receptor-bound states. We generated these maps by measuring the effects of alanine mutations on the stability of Gαi1 and of the rhodopsin-Gαi1 complex. We identified stabilization clusters in the GTPase and helical domains responsible for structural integrity and the conformational changes associated with activation. In activation cluster I, helices α1 and α5 pack against strands β1-3 to stabilize the nucleotide-bound states. In the receptor-bound state, these interactions are replaced by interactions between α5 and strands β4-6. Key residues in this cluster are Y320, crucial for the stabilization of the receptor-bound state, and F336, which stabilizes nucleotide-bound states. Destabilization of helix α1, caused by rearrangement of this activation cluster, leads to the weakening of the inter-domain interface and release of GDP. PMID:26258638

  20. Probing the interaction of the amino acid alanine with the surface of ZnO(1010).

    PubMed

    Gao, Y K; Traeger, F; Shekhah, O; Idriss, H; Wöll, C

    2009-10-01

    The adsorption modes and stability of the amino acid alanine (NH(2)-CH(CH(3))-COOH) have been studied on the nonpolar single crystal surface of zinc oxide, ZnO(1010), experimentally by X-ray photoelectron spectroscopy (XPS) and computationally using density functional theory (DFT). Deposition at 200 K was found to lead to the formation of multilayers identified by an XPS N1s peak at 401.7 eV assigned to the NH(3)(+) group, a fingerprint of the zwitterionic structure of alanine in the solid state. Heating to 300 K resulted in the removal of most of the multilayers with the remaining surface coverage estimated to 0.4 with respect to Zn cations. At this temperature most of the alanine molecules are found to be deprotonated (dissociated), yielding a carboxylate species (NH(2)-CH(CH(3))-COO(-) (a) + OH (s); where O is surface oxygen, (a) for adsorbed and (s) for surface species). Further heating of the surface resulted in a gradual decrease of the surface coverage and by 500 K a large fraction of adsorbed alanine molecules have desorbed from the surface. Total energy DFT computations of different adsorbate species identified two stable dissociative adsorption modes: bidentate and monodentate. The bidentate species with adsorption energy of 1.75 eV was found to be more stable than the monodentate species by about 0.7 eV.

  1. Probing the interaction of caffeic acid with ZnO nanoparticles.

    PubMed

    Belay, Abebe; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2016-05-01

    The binding of ZnO nanoparticles (NPs) and caffeic acid (CFA) was investigated using fluorescence quenching, UV/vis absorption spectrscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) at different temperatures. The study results indicated fluorescence quenching between ZnO NPs and CFA rationalized in terms of a static quenching mechanism or the formation of non-fluorescent CFA-ZnO. From fluorescence quenching spectral analysis, the binding constant (K(a)), number of binding sites (n) and thermodynamic properties were determined. Values of the quenching (K(SV)) and binding (K(a)) constants decrease with increasing temperature and the number of binding sites n = 2. The thermodynamic parameters determined using Van't Hoff equation indicated that binding occurs spontaneously involving the hydrogen bond, and van der Waal's forces played a major role in the reaction of ZnO NPs with CFA. The FTIR, TEM and DLS measurements also indicated differences in the structure, morphology and size of CFA, ZnO NPs and their corresponding CFA-ZnO.

  2. Estimation of Bacterial Cell Numbers in Humic Acid-Rich Salt Marsh Sediments with Probes Directed to 16S Ribosomal DNA

    PubMed Central

    Edgcomb, Virginia P.; McDonald, John H.; Devereux, Richard; Smith, David W.

    1999-01-01

    The feasibility of using probes directed towards ribosomal DNAs (rDNAs) as a quantitative approach to estimating cell numbers was examined and applied to study the structure of a bacterial community in humic acid-rich salt marsh sediments. Hybridizations were performed with membrane-bound nucleic acids by using seven group-specific DNA oligonucleotide probes complementary to 16S rRNA coding regions. These included a general eubacterial probe and probes encompassing most members of the gram-negative, mesophilic sulfate-reducing bacteria (SRB). DNA was extracted from sediment samples, and contaminating materials were removed by a series of steps. Efficiency of DNA extraction was 48% based on the recovery of tritiated plasmid DNA added to samples prior to extraction. Reproducibility of the extraction procedure was demonstrated by hybridizations to replicate samples. Numbers of target cells in samples were estimated by comparing the amount of hybridization to extracted DNA obtained with each probe to that obtained with a standard curve of genomic DNA for reference strains included on the same membrane. In June, numbers of SRB detected with an SRB-specific probe ranged from 6.0 × 107 to 2.5 × 109 (average, 1.1 × 109 ± 5.2 × 108) cells g of sediment−1. In September, numbers of SRB detected ranged from 5.4 × 108 to 7.3 × 109 (average, 2.5 × 109 ± 1.5 × 109) cells g of sediment−1. The capability of using rDNA probes to estimate cell numbers by hybridization to DNA extracted from complex matrices permits initiation of detailed studies on community composition and changes in communities based on cell numbers in formerly intractable environments. PMID:10103245

  3. Chromatographic analysis of the effects of fatty acids and glycation on binding by probes for Sudlow sites I and II to human serum albumin.

    PubMed

    Anguizola, Jeanethe; Debolt, Erin; Suresh, D; Hage, David S

    2016-05-15

    The primary endogenous ligands of human serum albumin (HSA) are non-esterified fatty acids, with 0.1-2mol of fatty acids normally being bound to HSA. In type II diabetes, fatty acid levels in serum are often elevated, and the presence of high glucose results in an increase in the non-enzymatic glycation of HSA. High-performance affinity chromatography (HPAC) was used to examine the combined effects of glycation and the presence of long chain fatty acids on the binding of HSA with R-warfarin and l-tryptophan (i.e., probes for Sudlow sites I and II, the major sites for drugs on this protein). Zonal elution competition studies were used to examine the interactions of myristic acid, palmitic acid and stearic acid with these probes on HSA. It was found that all these fatty acids had direct competition with R-warfarin at Sudlow site I of normal HSA and glycated HSA, with the glycated HSA typically having stronger binding for the fatty acids at this site. At Sudlow site II, direct competition was observed for all the fatty acids with l-tryptophan when using normal HSA, while glycated HSA gave no competition or positive allosteric interactions between these fatty acids and l-tryptophan. These data indicated that glycation can alter the interactions of drugs and fatty acids at specific binding sites on HSA. The results of this study should lead to a better understanding of how these interactions may change during diabetes and demonstrate how HPAC can be used to examine drug/solute-protein interactions in complex systems.

  4. Quantum dot photoluminescence lifetime-based pH nanosensor.

    PubMed

    Ruedas-Rama, Maria J; Orte, Angel; Hall, Elizabeth A H; Alvarez-Pez, Jose M; Talavera, Eva M

    2011-03-14

    The first CdSe/ZnS quantum dot photoluminescence lifetime-based pH nanosensor has been developed. The average lifetime of mercaptopropionic acid-capped QD nanosensors showed a linear response in the pH range of 5.2-6.9. These nanosensors have been satisfactorily applied for pH estimation in simulated intracellular media, with high sensitivity and high selectivity toward most of the intracellular components.

  5. Red photoluminescence BCNO synthesized from graphene oxide nanosheets

    NASA Astrophysics Data System (ADS)

    Kang, Yue; Chu, Zeng-yong; Ma, Tian; Li, Wei-ping; Zhang, Dong-jiu; Tang, Xiao-yu

    2016-01-01

    In this paper, we demonstrate the conversion of graphene oxide (GO) into boron carbon oxynitride (BCNO) hybrid nanosheets via a reaction with boric acid and urea, during which the boron and nitrogen atoms are incorporated into graphene nanosheets. The experimental results reveal that GO is important for the photoluminescence (PL) BCNO phosphor particles. More importantly, in this system, the prepared BCNO phosphors can be used to prepare the materials needed for red light emitting diodes (LEDs).

  6. Preparation and application of cysteine-capped ZnS nanoparticles as fluorescence probe in the determination of nucleic acids

    NASA Astrophysics Data System (ADS)

    Li, Yongxin; Chen, Jinlong; Zhu, Changqin; Wang, Lun; Zhao, Danhua; Zhuo, Shujuan; Wu, Yuqin

    2004-07-01

    Cysteine-capped ZnS nanometer-sized fluorescent particles were produced by a colloidal aqueous synthesis. The functionalized nanoparticles are water-soluble and suitable for biological application. A synchronous fluorescence method has been developed for the rapid determination of DNA with functionalized nano-ZnS as a fluorescence probe, based on the synchronous fluorescence enhancement of cysteine-capped nano-ZnS in the presence of DNA. When Δ λ=190 nm, maximum synchronous fluorescence is produced at 267 nm at pH 5.12. Under optimum conditions, the synchronous fluorescence intensity is proportional to the concentration of nucleic acids in the range 0.1-1.2 μg ml -1 for calf thymus DNA, 0.1-0.6 μg ml -1 for fish sperm DNA. The corresponding detection limit is 32.9 ng ml -1 for calf thymus DNA and 24.6 ng ml -1 for fish sperm DNA. This method is simple, inexpensive, rapid and sensitive. The recovery and relative standard deviation are satisfactory.

  7. Counterion distribution surrounding spherical nucleic acid-Au nanoparticle conjugates probed by small-angle x-ray scattering.

    PubMed

    Kewalramani, Sumit; Zwanikken, Jos W; Macfarlane, Robert J; Leung, Cheuk-Yui; Olvera de la Cruz, Monica; Mirkin, Chad A; Bedzyk, Michael J

    2013-12-23

    The radial distribution of monovalent cations surrounding spherical nucleic acid-Au nanoparticle conjugates (SNA-AuNPs) is determined by in situ small-angle x-ray scattering (SAXS) and classical density functional theory (DFT) calculations. Small differences in SAXS intensity profiles from SNA-AuNPs dispersed in a series of solutions containing different monovalent ions (Na(+), K(+), Rb(+), or Cs(+)) are measured. Using the "heavy ion replacement" SAXS (HIRSAXS) approach, we extract the cation-distribution-dependent contribution to the SAXS intensity and show that it agrees with DFT predictions. The experiment-theory comparisons reveal the radial distribution of cations as well as the conformation of the DNA in the SNA shell. The analysis shows an enhancement to the average cation concentration in the SNA shell that can be up to 15-fold, depending on the bulk solution ionic concentration. The study demonstrates the feasibility of HIRSAXS in probing the distribution of monovalent cations surrounding nanoparticles with an electron dense core (e.g., metals).

  8. Synthesis of fluorescent D-amino acids (FDAAs) and their use for probing peptidoglycan synthesis and bacterial growth in situ

    PubMed Central

    Kuru, Erkin; Tekkam, Srinivas; Hall, Edward

    2015-01-01

    Fluorescent D-amino acids (FDAAs) are efficiently incorporated into the peptidoglycan of diverse bacterial species at the sites of active peptidoglycan biosynthesis, allowing specific and covalent probing of bacterial growth with minimal perturbation. Here, we provide a protocol for the synthesis of four FDAAs emitting light in blue, green or red and for their use in peptidoglycan labeling of live bacteria. Our modular synthesis protocol gives easy access to a library of different FDAAs made with commercially available fluorophores. FDAAs can be synthesized in a typical chemistry laboratory in 2–3 days. The simple labeling procedure involves addition of the FDAAs to the bacterial sample for the desired labeling duration and stopping further label incorporation by fixation or by washing away excess dye. We discuss several scenarios for the use of these labels including short or long labeling durations, and the combination of different labels in pure culture or complex environmental samples. Depending on the experiment, FDAA labeling can take as little as 30 s for a rapidly growing species such as Escherichia coli. PMID:25474031

  9. Conformers of β-aminoisobutyric acid probed by jet-cooled microwave and matrix isolation infrared spectroscopic techniques.

    PubMed

    Kuş, N; Sharma, A; Peña, I; Bermúdez, M C; Cabezas, C; Alonso, J L; Fausto, R

    2013-04-14

    β-aminoisobutyric acid (BAIBA) has been studied in isolation conditions: in the gas phase and trapped into a cryogenic N2 matrix. A solid sample of the compound was vaporized by laser ablation and investigated through their rotational spectra in a supersonic expansion using two different spectroscopic techniques: broadband chirped pulse Fourier transform microwave spectroscopy and conventional molecular beam Fourier transform microwave spectroscopy. Four conformers with structures of two types could be successfully identified by comparison of the experimental rotational and (14)N nuclear quadruple coupling constants with those predicted theoretically: type A, bearing an OH⋯N intramolecular hydrogen bond and its carboxylic group in the trans geometry (H-O-C=O dihedral ∼180°), and type B, having an NH⋯O bond and the cis arrangement of the carboxylic group. These two types of conformers could also be trapped from the gas phase into a cryogenic N2 matrix and probed by Fourier transform infrared (IR) spectroscopy. In situ irradiation of BAIBA isolated in N2 matrix of type B conformers using near-IR radiation tuned at the frequency of the O-H stretching 1st overtone (∼6930 cm(-1)) of these forms allowed to selectively convert them into type A conformers and into a new type of conformers of higher energy (type D) bearing an NH⋯O=C bond and a O-H "free" trans carboxylic group.

  10. Conformers of β-aminoisobutyric acid probed by jet-cooled microwave and matrix isolation infrared spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Kuş, N.; Sharma, A.; Peña, I.; Bermúdez, M. C.; Cabezas, C.; Alonso, J. L.; Fausto, R.

    2013-04-01

    β-aminoisobutyric acid (BAIBA) has been studied in isolation conditions: in the gas phase and trapped into a cryogenic N2 matrix. A solid sample of the compound was vaporized by laser ablation and investigated through their rotational spectra in a supersonic expansion using two different spectroscopic techniques: broadband chirped pulse Fourier transform microwave spectroscopy and conventional molecular beam Fourier transform microwave spectroscopy. Four conformers with structures of two types could be successfully identified by comparison of the experimental rotational and 14N nuclear quadruple coupling constants with those predicted theoretically: type A, bearing an OH⋯N intramolecular hydrogen bond and its carboxylic group in the trans geometry (H-O-C=O dihedral ˜180°), and type B, having an NH⋯O bond and the cis arrangement of the carboxylic group. These two types of conformers could also be trapped from the gas phase into a cryogenic N2 matrix and probed by Fourier transform infrared (IR) spectroscopy. In situ irradiation of BAIBA isolated in N2 matrix of type B conformers using near-IR radiation tuned at the frequency of the O-H stretching 1st overtone (˜6930 cm-1) of these forms allowed to selectively convert them into type A conformers and into a new type of conformers of higher energy (type D) bearing an NH⋯O=C bond and a O-H "free" trans carboxylic group.

  11. Tough photoluminescent hydrogels doped with lanthanide.

    PubMed

    Wang, Mei Xiang; Yang, Can Hui; Liu, Zhen Qi; Zhou, Jinxiong; Xu, Feng; Suo, Zhigang; Yang, Jian Hai; Chen, Yong Mei

    2015-03-01

    Photoluminescent hydrogels have emerged as novel soft materials with potential applications in many fields. Although many photoluminescent hydrogels have been fabricated, their scope of usage has been severely limited by their poor mechanical performance. Here, a facile strategy is reported for preparing lanthanide (Ln)-alginate/polyacrylamide (PAAm) hydrogels with both high toughness and photoluminescence, which has been achieved by doping Ln(3+) ions (Ln = Eu, Tb, Eu/Tb) into alginate/PAAm hydrogel networks, where Ln(3+) ions serve as both photoluminescent emitters and physical cross-linkers. The resulting hydrogels exhibit versatile advantages including excellent mechanical properties (∼ MPa strength, ≈ 20 tensile strains, ≈ 10(4) kJ m(-3) energy dissipation), good photoluminescent performance, tunable emission color, excellent processability, and cytocompatibility. The developed tough photoluminescent hydrogels hold great promises for expanding the usage scope of hydrogels.

  12. On the pH-dependent quenching of quantum dot photoluminescence by redox active dopamine.

    PubMed

    Ji, Xin; Palui, Goutam; Avellini, Tommaso; Na, Hyon Bin; Yi, Chongyue; Knappenberger, Kenneth L; Mattoussi, Hedi

    2012-04-04

    We investigated the charge transfer interactions between luminescent quantum dots (QDs) and redox active dopamine. For this, we used pH-insensitive ZnS-overcoated CdSe QDs rendered water-compatible using poly (ethylene glycol)-appended dihydrolipoic acid (DHLA-PEG), where a fraction of the ligands was amine-terminated to allow for controlled coupling of dopamine-isothiocyanate onto the nanocrystal. Using this sample configuration, we probed the effects of changing the density of dopamine and the buffer pH on the fluorescence properties of these conjugates. Using steady-state and time-resolved fluorescence, we measured a pronounced pH-dependent photoluminescence (PL) quenching for all QD-dopamine assemblies. Several parameters affect the PL loss. First, the quenching efficiency strongly depends on the number of dopamines per QD-conjugate. Second, the quenching efficiency is substantially increased in alkaline buffers. Third, this pH-dependent PL loss can be completely eliminated when oxygen-depleted buffers are used, indicating that oxygen plays a crucial role in the redox activity of dopamine. We attribute these findings to charge transfer interactions between QDs and mainly two forms of dopamine: the reduced catechol and oxidized quinone. As the pH of the dispersions is changed from acidic to basic, oxygen-catalyzed transformation progressively reduces the dopamine potential for oxidation and shifts the equilibrium toward increased concentration of quinones. Thus, in a conjugate, a QD can simultaneously interact with quinones (electron acceptors) and catechols (electron donors), producing pH-dependent PL quenching combined with shortening of the exciton lifetime. This also alters the recombination kinetics of the electron and hole of photoexcited QDs. Transient absorption measurements that probed intraband transitions supported those findings where a simultaneous pronounced change in the electron and hole relaxation rates was measured when the pH was changed from

  13. Folic acid-conjugated core/shell ZnS:Mn/ZnS quantum dots as targeted probes for two photon fluorescence imaging of cancer cells.

    PubMed

    Geszke, Malgorzata; Murias, Marek; Balan, Lavinia; Medjahdi, Ghouti; Korczynski, Jaroslaw; Moritz, Michal; Lulek, Janina; Schneider, Raphaël

    2011-03-01

    This work presents a novel approach to producing water soluble manganese-doped core/shell ZnS/ZnS quantum dots (ZnS:Mn/ZnS). The Mn-doped ZnS core was prepared through a nucleation doping strategy and a ZnS shell was grown on ZnS:Mn d-dots by decomposition of Zn(2+)-3-mercaptopropionic acid (MPA) complexes at 100 °C. It was found that the Mn2+(4)T1→6A1 fluorescence emission at ∼590 nm significantly increased after growth of the shell when the Mn2+ doping content was 4.0 at.%. A photoluminescence quantum yield of ∼22% was obtained for core/shell nanocrystals. The nanoparticles were structurally and compositionally characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and dynamic light scattering. The surface MPA molecules favor the dispersion of ZnS:Mn/ZnS QDs in aqueous media and make possible conjugation with targeting folic acid molecules. The folate receptor-mediated delivery of folic acid-conjugated ZnS:Mn/ZnS QDs was demonstrated using confocal microscopy with biphotonic excitation. Bare and folate-conjugated QDs exhibit only weak cytotoxicity towards folate receptor-positive T47D cancer cells and MCF-7 cells, used as a reference, at high concentrations (mmolar range) after 72h incubation.

  14. A genetically encoded probe for the identification of proteins that form sulfenic acid in response to H2O2 in Saccharomyces cerevisiae.

    PubMed

    Takanishi, Christina L; Wood, Matthew J

    2011-06-03

    It is widely known that reactive oxygen species (ROS), such as hydrogen peroxide, play important roles in cellular signaling and initiation of oxidative stress responses via thiol modifications. Identification of the targets of these modifications will provide a better understanding of the relationship between ROS and human diseases, such as cancer and atherosclerosis. Sulfenic acid is the principle product of a reaction between hydrogen peroxide and a reactive protein cysteine. This reversible post-translational modification plays an important role in enzyme active sites, signaling transduction via disulfide bond formation, as well as an intermediate to overoxidation products during oxidative stress. By re-engineering the C-terminal cysteine rich domain (cCRD) of the Yap1 transcription factor, we were able to create a genetically encoded probe for the general detection and identification of proteins that form sulfenic acid in vivo. The Yap1-cCRD probe has been used previously in the identification of proteins that form sulfenic acid in Escherichia coli. Here we demonstrate the successful use of the Yap1-cCRD probe in the identification of proteins that form sulfenic acid in response to hydrogen peroxide in Saccharomyces cerevisiae.

  15. Unravelling the Bacterial Vaginosis-Associated Biofilm: A Multiplex Gardnerella vaginalis and Atopobium vaginae Fluorescence In Situ Hybridization Assay Using Peptide Nucleic Acid Probes.

    PubMed

    Hardy, Liselotte; Jespers, Vicky; Dahchour, Nassira; Mwambarangwe, Lambert; Musengamana, Viateur; Vaneechoutte, Mario; Crucitti, Tania

    2015-01-01

    Bacterial vaginosis (BV), a condition defined by increased vaginal discharge without significant inflammation, is characterized by a change in the bacterial composition of the vagina. Lactobacillus spp., associated with a healthy vaginal microbiome, are outnumbered by BV-associated organisms. These bacteria could form a polymicrobial biofilm which allows them to persist in spite of antibiotic treatment. In this study, we examined the presence of Gardnerella vaginalis and Atopobium vaginae in vaginal biofilms using Peptide Nucleic Acid (PNA) probes targeting these bacteria. For this purpose, we developed three new PNA probes for A. vaginae. The most specific A. vaginae probe, AtoITM1, was selected and then used in an assay with two existing probes, Gard162 and BacUni-1, to evaluate multiplex FISH on clinical samples. Using quantitative polymerase chain reaction (qPCR) as the gold standard, we demonstrated a sensitivity of 66.7% (95% confidence interval: 54.5% - 77.1%) and a specificity of 89.4% (95% confidence interval: 76.1% - 96%) of the new AtoITM1 probe. FISH enabled us to show the presence of a polymicrobial biofilm in bacterial vaginosis, in which Atopobium vaginae is part of a Gardnerella vaginalis-dominated biofilm. We showed that the presence of this biofilm is associated with high bacterial loads of A. vaginae and G. vaginalis.

  16. Unravelling the Bacterial Vaginosis-Associated Biofilm: A Multiplex Gardnerella vaginalis and Atopobium vaginae Fluorescence In Situ Hybridization Assay Using Peptide Nucleic Acid Probes

    PubMed Central

    Hardy, Liselotte; Jespers, Vicky; Dahchour, Nassira; Mwambarangwe, Lambert; Musengamana, Viateur; Vaneechoutte, Mario; Crucitti, Tania

    2015-01-01

    Bacterial vaginosis (BV), a condition defined by increased vaginal discharge without significant inflammation, is characterized by a change in the bacterial composition of the vagina. Lactobacillus spp., associated with a healthy vaginal microbiome, are outnumbered by BV-associated organisms. These bacteria could form a polymicrobial biofilm which allows them to persist in spite of antibiotic treatment. In this study, we examined the presence of Gardnerella vaginalis and Atopobium vaginae in vaginal biofilms using Peptide Nucleic Acid (PNA) probes targeting these bacteria. For this purpose, we developed three new PNA probes for A. vaginae. The most specific A. vaginae probe, AtoITM1, was selected and then used in an assay with two existing probes, Gard162 and BacUni-1, to evaluate multiplex FISH on clinical samples. Using quantitative polymerase chain reaction (qPCR) as the gold standard, we demonstrated a sensitivity of 66.7% (95% confidence interval: 54.5% - 77.1%) and a specificity of 89.4% (95% confidence interval: 76.1% - 96%) of the new AtoITM1 probe. FISH enabled us to show the presence of a polymicrobial biofilm in bacterial vaginosis, in which Atopobium vaginae is part of a Gardnerella vaginalis-dominated biofilm. We showed that the presence of this biofilm is associated with high bacterial loads of A. vaginae and G. vaginalis. PMID:26305575

  17. Use of dimedone-based chemical probes for sulfenic acid detection evaluation of conditions affecting probe incorporation into redox-sensitive proteins.

    PubMed

    Klomsiri, Chananat; Nelson, Kimberly J; Bechtold, Erika; Soito, Laura; Johnson, Lynnette C; Lowther, W Todd; Ryu, Seong-Eon; King, S Bruce; Furdui, Cristina M; Poole, Leslie B

    2010-01-01

    Sulfenic acids, formed as transient intermediates during the reaction of cysteine residues with peroxides, play significant roles in enzyme catalysis and regulation, and are also involved in the redox regulation of transcription factors and other signaling proteins. Therefore, interest in the identification of protein sulfenic acids has grown substantially in the past few years. Dimedone, which specifically traps sulfenic acids, has provided the basis for the synthesis of a novel group of compounds that derivatize 1,3-cyclohexadione, a dimedone analogue, with reporter tags such as biotin for affinity capture and fluorescent labels for visual detection. These reagents allow identification of the cysteine sites and proteins that are sensitive to oxidation and permit identification of the cellular conditions under which such oxidations occur. We have shown that these compounds are reactive and specific toward sulfenic acids and that the labeled proteins can be detected at high sensitivity using gel analysis or mass spectrometry. Here, we further characterize these reagents, showing that the DCP-Bio1 incorporation rates into three sulfenic acid containing proteins, papaya papain, Escherichia coli fRMsr, and the Salmonella typhimurium peroxiredoxin AhpC, are significantly different and, in the case of fRMsr, are unaffected by changes in buffer pH from 5.5 and 8.0. We also provide protocols to label protein sulfenic acids in cellular proteins, either by in situ labeling of intact cells or by labeling at the time of lysis. We show that the addition of alkylating reagents and catalase to the lysis buffer is critical in preventing the formation of sulfenic acid subsequent to cell lysis. Data presented herein also indicate that the need to standardize, as much as possible, the protein and reagent concentrations during labeling. Finally, we introduce several new test or control proteins that can be used to evaluate labeling procedures and efficiencies.

  18. Development and Evaluation of Novel Real-Time Reverse Transcription-PCR Assays with Locked Nucleic Acid Probes Targeting Leader Sequences of Human-Pathogenic Coronaviruses.

    PubMed

    Chan, Jasper Fuk-Woo; Choi, Garnet Kwan-Yue; Tsang, Alan Ka-Lun; Tee, Kah-Meng; Lam, Ho-Yin; Yip, Cyril Chik-Yan; To, Kelvin Kai-Wang; Cheng, Vincent Chi-Chung; Yeung, Man-Lung; Lau, Susanna Kar-Pui; Woo, Patrick Chiu-Yat; Chan, Kwok-Hung; Tang, Bone Siu-Fai; Yuen, Kwok-Yung

    2015-08-01

    Based on findings in small RNA-sequencing (Seq) data analysis, we developed highly sensitive and specific real-time reverse transcription (RT)-PCR assays with locked nucleic acid probes targeting the abundantly expressed leader sequences of Middle East respiratory syndrome coronavirus (MERS-CoV) and other human coronaviruses. Analytical and clinical evaluations showed their noninferiority to a commercial multiplex PCR test for the detection of these coronaviruses.

  19. Fluorescence determination of DNA with 1-pyrenebutyric acid nanoparticles coated with β-cyclodextrin as a fluorescence probe

    NASA Astrophysics Data System (ADS)

    Wang, Lun; Bian, Guirong; Wang, Leyu; Dong, Ling; Chen, Hongqi; Xia, Tingting

    2005-04-01

    A novel ultrasonication method has been successfully developed for the preparation of 1-pyrenebutyric acid (PBAC)/β-cyclodextrin(β-CD) complex nanoparticles. The as-prepared nanoparticles are characterized by transmission electron microscopy (TEM), fluorescence excitation and emission spectroscopy. Complex nanoparticles prepared with ultrasonication are smaller and better dispersed than single PBAC nanoparticles. At pH 3.0, the relative fluorescence intensity of complex nanoparticles of PBAC/β-CD can be quenched by the concentration of DNA. Based on this, a novel fluorimetric method has been developed for rapid determination of DNA. In comparison with single organic fluorophores, these nanoparticle probes are better water-solubility, more stable and do not suffer from blinking. Under optimum conditions, the calibration graphs are linear over the range 0.2-15 μg mL -1 for calf thymus DNA (ct-DNA) and 0.3-12 μg mL -1 for fish sperm DNA (fs-DNA). The corresponding detection limit is 0.01 μg mL -1 for ct-DNA and 0.02 μg mL -1 for fs-DNA. The relative standard deviation of seven replicate measurements is 1.2% for 2.0 μg mL -1 ct-DNA and 1.4% for 2.0 μg mL -1 fs-DNA, respectively. The method is simple and sensitive. The recovery and relative standard deviation are very satisfactory. A mechanism proposed to explain the process also has been studied.

  20. Hydrothermal synthetic mercaptopropionic acid stabled CdTe quantum dots as fluorescent probes for detection of Ag⁺.

    PubMed

    Gan, Ting-Ting; Zhang, Yu-Jun; Zhao, Nan-Jing; Xiao, Xue; Yin, Gao-Fang; Yu, Shao-Hui; Wang, Huan-Bo; Duan, Jing-Bo; Shi, Chao-Yi; Liu, Wen-Qing

    2012-12-01

    Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) with particle size 3 nm have been successfully synthesized in aqueous medium by hydrothermal synthesis method. And the effects of different metal ions on MPA capped CdTe QDs fluorescence were studied using fluorescence spectrometry. The results demonstrated that at the same concentration level, Ag(+) could strongly quench CdTe QDs fluorescence, and the other metal ions had little effect on CdTe QDs fluorescence except Cu(2+). On the basis of this fact, a rapid, simple, highly sensitive and selective method based on fluorescence quenching principle for Ag(+) detection in aqueous solution was proposed. Under optimal conditions, the quenched fluorescence intensity (F(0)-F) increased linearly with the concentration of Ag(+) ranging from 4 × 10(-7) to 32 × 10(-7)mol L(-1). The limit of detection for Ag(+) was 4.106 × 10(-8)mol L(-1). The obtained plot of F(0)/F versus [Ag(+)] was an upward curvature, concave towards the y-axis, rather than a straight line. The modified form of the Stern-Volmer equation was third order in Ag(+) concentration. According to the modified Stern-Volmer equation, it can be inferred that dynamic quenching and static quenching simultaneously occurred when Ag(+) interacted with MPA capped CdTe QDs. At the same time other factors might also influence the quenching process. Based on this study, hydrothermal synthesized MPA capped CdTe QDs with particle size 3 nm may be used as a novel fluorescence probe to quantificationally and selectively detect Ag(+).

  1. Photoluminescence of Conjugated Star Polymers

    NASA Astrophysics Data System (ADS)

    Ferguson, J. B.; Prigodin, N. V.; Epstein, A. J.; Wang, F.

    2000-10-01

    Higher dimensionality "star" polymers provide new properties beyond those found in their linear analogs. They have been used to improving electronic properties for nonlinear optics through exciton transfer and molecular antenna structures for example (M. Kawa, J. M. J. Frechet, Chem. Mater. 10, 286 (1998).). We report on photoluminescence properties of star polymers with a hyperbranched core (both hyperbranched phenlyene and hyperbranched triphenylamine) and polyhexylthiophene arms. The arm is a conjugated oligomer of polythiophene that has been investigated extensively for metallic like conductivity when doped as well as utilized in field effect transistors in its undoped form (A. Tsumara, H. Koezuka, T. Ando, Appl. Phys. Lett. 49, 1210 (1986).). The cores are respectively, a nonconjugated polymer in the case of hyperbranched phenlyene and a conjugated polymer in the case of hyperbranched triphenylamine. The photoluminesce spectrum (λ_max at 575 nm) is identical for both star polymers with the two electronically different hyperbranched cores and for linear polythiophene alone. We conclude the wave functions of the core and arms do not strongly interact to form states different from their individual states and excitons formed on the hyperbranched cores migrate to the lower bandgap polythiophene before recombining.

  2. Bioanalytical system for detection of cancer cells with photoluminescent ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Viter, R.; Jekabsons, K.; Kalnina, Z.; Poletaev, N.; Hsu, S. H.; Riekstina, U.

    2016-11-01

    Using photoluminescent ZnO nanorods and carbohydrate marker SSEA-4, a novel cancer cell recognition system was developed. Immobilization of SSEA-4 antibodies (αSSEA-4) on ZnO nanorods was performed in buffer solution (pH = 7.1) over 2 h. The cancer cell line probes were fixed on the glass slide. One hundred microliters of ZnO-αSSEA-4 conjugates were deposited on the cell probe and exposed for 30 min. After washing photoluminescence spectra were recorded. Based on the developed methodology, ZnO-αSSEA-4 probes were tested on patient-derived breast and colorectal carcinoma cells. Our data clearly show that the carbohydrate SSEA-4 molecule is expressed on cancer cell lines and patient-derived cancer cells. Moreover, SSEA-4 targeted ZnO nanorods bind to the patient-derived cancer cells with high selectivity and the photoluminescence signal increased tremendously compared to the signal from the control samples. Furthermore, the photoluminescence intensity increase correlated with the extent of malignancy in the target cell population. A novel portable bioanalytical system, based on optical ZnO nanorods and fiber optic detection system was developed. We propose that carbohydrate SSEA-4 specific ZnO nanorods could be used for the development of cancer diagnostic biosensors and for targeted therapy.

  3. Positively charged polymer brush-functionalized filter paper for DNA sequence determination following Dot blot hybridization employing a pyrrolidinyl peptide nucleic acid probe.

    PubMed

    Laopa, Praethong S; Vilaivan, Tirayut; Hoven, Voravee P

    2013-01-07

    As inspired by the Dot blot analysis, a well known technique in molecular biology and genetics for detecting biomolecules, a new paper-based platform for colorimetric detection of specific DNA sequences employing peptide nucleic acid (PNA) as a probe has been developed. In this particular study, a pyrrolidinyl PNA bearing a conformationally rigid d-prolyl-2-aminocyclopentanecarboxylic acid backbone (acpcPNA) was used as a probe. The filter paper was modified to be positively charged with grafted polymer brushes of quaternized poly(dimethylamino)ethyl methacrylate (QPDMAEMA) prepared by surface-initiated polymerization of 2-(dimethylamino)ethyl methacrylate from the filter paper via ARGET ATRP followed by quaternization with methyl iodide. Following the Dot blot format, a DNA target was first immobilized via electrostatic interactions between the positive charges of the QPDMAEMA brushes and negative charges of the phosphate backbone of DNA. Upon hybridization with the biotinylated pyrrolidinyl peptide nucleic acid (b-PNA) probe, the immobilized DNA can be detected by naked eye observation of the yellow product generated by the enzymatic reaction employing HRP-labeled streptavidin. It has been demonstrated that this newly developed assay was capable of discriminating between complementary and single base mismatch targets at a detection limit of at least 10 fmol. In addition, the QPDMAEMA-grafted filter paper exhibited a superior performance to the commercial membranes, namely Nylon 66 and nitrocellulose.

  4. Analysis of Protein–Protein Interactions in MCF-7 and MDA-MB-231 Cell Lines Using Phthalic Acid Chemical Probes

    PubMed Central

    Liang, Shih-Shin; Wang, Tsu-Nai; Tsai, Eing-Mei

    2014-01-01

    Phthalates are a class of plasticizers that have been characterized as endocrine disrupters, and are associated with genital diseases, cardiotoxicity, hepatotoxicity, and nephrotoxicity in the GeneOntology gene/protein database. In this study, we synthesized phthalic acid chemical probes and demonstrated differing protein–protein interactions between MCF-7 cells and MDA-MB-231 breast cancer cell lines. Phthalic acid chemical probes were synthesized using silicon dioxide particle carriers, which were modified using the silanized linker 3-aminopropyl triethoxyslane (APTES). Incubation with cell lysates from breast cancer cell lines revealed interactions between phthalic acid and cellular proteins in MCF-7 and MDA-MB-231 cells. Subsequent proteomics analyses indicated 22 phthalic acid-binding proteins in both cell types, including heat shock cognate 71-kDa protein, ATP synthase subunit beta, and heat shock protein HSP 90-beta. In addition, 21 MCF-7-specific and 32 MDA-MB-231 specific phthalic acid-binding proteins were identified, including related proteasome proteins, heat shock 70-kDa protein, and NADPH dehydrogenase and ribosomal correlated proteins, ras-related proteins, and members of the heat shock protein family, respectively. PMID:25402641

  5. Development of Intrinsically Photoluminescent and Photostable Polylactones

    PubMed Central

    Xie, Zhiwei; Zhang, Yi; Liu, Li; Weng, Hong; Mason, Ralph P.; Tang, Liping; Nguyen, Kytai T.; Hsieh, Jer-Tsong

    2014-01-01

    A method of introducing intrinsically photoluminescent properties to biodegradable polymer was introduced, exemplified by the synthesis of intrinsically photoluminescent polylactones that enable non-invasively monitoring and tracking material degradation in vivo in real-time and the formation of theranostic nanoparticles for cancer imaging and drug delivery. PMID:24668888

  6. Highly Sensitive and Selective Method for Detecting Ultratrace Levels of Aqueous Uranyl Ions by Strongly Photoluminescent-Responsive Amine-Modified Cadmium Sulfide Quantum Dots.

    PubMed

    Dutta, R K; Kumar, Ambika

    2016-09-20

    Detection of ultratrace levels of aqueous uranyl ions without using sophisticated analytical instrumentation and a tedious sample preparation method is a challenge for environmental monitoring and mitigation. Here we present a novel yet simple analytical method for highly sensitive and specific detection of uranyl ions via photoluminescence quenching of CdS quantum dots. We have demonstrated a new approach for synthesizing highly water-soluble and strong photoluminescence-emitting CdS quantum dots (i.e., CdS-MAA and CdS-MAA-TU) of sizes less than 3 nm. The structural, morphological, and optical properties of both the batches of CdS quantum dots were thoroughly characterized by XRD, high-resolution transmission electron microscopy (HRTEM), zeta potential, UV-visible absorption, and photoluminescence spectroscopy. Compared to the batch of CdS quantum dots prepared by capping with only mercaptoacetic acid (CdS-MAA), the batch prepared by capping with mercaptoacetic acid and thiourea in tandem (CdS-MAA-TU) exhibited higher quantum yield= 16.64 ± 1.02%, and more importantly, CdS-MAA-TU exhibited significantly a higher order of photoluminescence quenching responses when treated with ultratrace concentrations of uranyl ions. Under the optimized conditions, the sensitivity of detecting uranyl ion by CdS-MAA-TU was several folds better (0.316 L/ μg) than that of CdS-MAA (0.0053 (L/μg/), as determined from their respective Stern-Volmer plots. Qualitatively, CdS-MAA-TU probe can be used for visual detection of uranyl ions of concentration greater than 5 μg/L. However, the instrumental method of analysis based on photoluminescence spectroscopy confirmed the feasibility for quantitative analysis of ultratrace concentrations of uranyl ions as implied from a very low limit of detection (LoD = 0.07 μg/L) and limit of quantification (LoQ = and 0.231 μg/L). Systematic studies revealed very high selectivity for uranyl ion detection, though minor interference from Cu(2+), Pb(2

  7. Development of a novel europium complex-based luminescent probe for time-gated luminescence imaging of hypochlorous acid in living samples

    NASA Astrophysics Data System (ADS)

    Liu, Xiangli; Guo, Lianying; Song, Bo; Tang, Zhixin; Yuan, Jingli

    2017-03-01

    Luminescent lanthanide complexes are key reagents used in the time-gated luminescence bioassay technique, but functional lanthanide complexes that can act as luminescent probes for specifically responding to analytes are very limited. In this work, we designed and synthesized a novel Eu3+ complex-based luminescence probe for hypochlorous acid (HOCl), NPPTTA-Eu3+, by using terpyridine polyacid-Eu3+, dinitrophenyl, and hydrazine as luminophore, quencher and HOCl-recognizer moieties, respectively. In the absence of HOCl, the probe is non-luminescent due to the strong luminescence quenching of the dinitrophenyl group in the complex. However, upon reaction with HOCl, the dinitrophenyl moiety is rapidly cleaved from the probe, which affords a strongly luminescent Eu3+ complex CPTTA-Eu3+, accompanied by a ∼900-fold luminescence enhancement with a long luminescence lifetime of 1.41 ms. This unique luminescence response of NPPTTA-Eu3+ to HOCl allowed NPPTTA-Eu3+ to be conveniently used as a probe for highly selective and sensitive detection of HOCl under the time-gated luminescence mode. In addition, by loading NPPTTA-Eu3+ into RAW 264.7 macrophage cells and Daphnia magna, the generation of endogenous HOCl in RAW 264.7 cells and the uptake of exogenous HOCl by Daphnia magna were successfully imaged on a true-color time-gated luminescence microscope. The results demonstrated the practical applicability of NPPTTA-Eu3+ as an efficient probe for time-gated luminescence imaging of HOCl in living cells and organisms.

  8. Synthesis of a new Ni-phenanthroline complex and its application as an electrochemical probe for detection of nucleic acid.

    PubMed

    Qiu, Bin; Guo, Longhua; Guo, Chunhua; Guo, Zhiyong; Lin, Zhenyu; Chen, Guonan

    2011-01-15

    A new DNA sensor using a nickel(II) phenanthroline complex ([Ni(phen)(2)PHPIP]·2ClO(4)) as the electrochemical probe was developed. The sensor is very sensitive and selective for calf thymus DNA (ctDNA) detection in aqueous medium. The Ni-phenanthroline probe was synthesized by a two-step preparation using p-hydroxy-phenylimidazo-1,10-phenanthroline (PHPIP) as the ligand and characterized with IR, UV and MS. Some interesting electrochemical properties of the Ni-complex and the interactions of the complex with ctDNA were reported. The calculated dynamics parameters of the electrode process indicate that there are obvious interactions between the probe and the ctDNA in aqueous solution. Under constant potential conditions, the redox current peak of the probe (Ni-complex) decreases obviously as the probe interacts/binds with ctDNAs. This unexpected electrochemical behavior may suggest that a new adduct through the binding of Ni-phenanthroline complex with ctDNA is formed electrochemically. By estimation, the binding ratio of the probe and ctDNA was found to be 1:1 with a binding constant β=4.29×10(5) mol L(-1) in aqueous solution at room temperature.

  9. 1,5-Benzodiazepin-2-ones: Investigation of a Family of Photoluminescent Materials.

    PubMed

    Mtiraoui, Hasan; Gharbi, Rafik; Msaddek, Moncef; Bretonnière, Yann; Andraud, Chantal; Sabot, Cyrille; Renard, Pierre-Yves

    2016-06-03

    Photoluminescent materials, that are now ubiquitous in our everyday life, have particularly attracted the attention of the scientific community these past few years due to potential important applications such as in bioimaging, sensing, or optoelectronics. In this context, relatively few different families of molecules have been reported to exhibit fluorescence in the aggregated or solid-state through the excited-state intramolecular proton transfer (ESIPT) photochemical process. The preparation and subsequent determination of photochemical properties of an underexplored family of 1,5-benzodiazepin-2-one derivatives are reported. From these data and X-ray diffraction analysis study, it emerged that photoluminescence (in the range 520-655 nm) was mostly attributed to ESIPT. The photoluminescent potential of 1,5-benzodiazepin-2-ones, their facile access, and functionalization were demonstrated through the preparation of two fluorogenic probes for the selective detection of biothiols.

  10. A peptide nucleic acid-functionalized carbon nitride nanosheet as a probe for in situ monitoring of intracellular microRNA.

    PubMed

    Liao, Xianjiu; Wang, Quanbo; Ju, Huangxian

    2015-06-21

    A novel probe for recognition of both cancer cells and intracellular microRNA (miRNA) is designed by functionalizing a carbon nitride nanosheet (f-CNNS) with a Cy5-labeled peptide nucleic acid (Cy5-PNA) and folate. The interaction between Cy5-PNA and CNNS quenches the fluorescence of Cy5, and the presence of folate endows the probe with good specificity to folate acceptor overexpressed cells. The probe can be specifically taken up by cancer cells with an incubation step. Upon the recognition of the PNA to complementary miRNA, the hybridization product is released from the CNNS surface, which leads to the fluorescence recovery and provides a specific method for sensing of miRNA. Thus, this probe can be used for cell-specific intracellular miRNA sensing with a confocal microscope. Using miRNA-18a as a target model, the dynamic changes of its expression level inside living cells can be monitored with the proposed method. This method possesses promising applications in the study of miRNA related bioprocesses and biomedicine.

  11. Dextran-encapsulated photoluminescent gold nanoclusters: synthesis and application

    NASA Astrophysics Data System (ADS)

    Chiu, Wei-Ju; Chen, Wei-Yu; Lai, Hong-Zheng; Wu, Ching-Yi; Chiang, Hsiang-Lin; Chen, Yu-Chie

    2014-07-01

    Dextrans are widely used as additives in food, pharmaceutical, and cosmetics because of their hydrophilicity, biocompatibility, and low toxicity. These features allow the use of dextrans to modify the surface of nanoparticles to improve cell compatibility for biomedical applications. Additionally, dextran molecules covalently bound with fluorescent dyes are frequently used as tracers in animal studies. These facts show that dextrans are useful compounds for biomedicine-related applications and research. Our aim was to explore a facile way to generate dextran-derived nanoparticles with photoluminescent property for the use in fluorescence imaging of bacteria and cancer cells. Dextran-encapsulated gold nanoclusters (AuNCs@dextran) were generated through a one-pot reaction by stirring dextrans and aqueous tetrachloroauric acid overnight. The generated AuNCs exhibit bright and green photoluminescence under the illumination of an ultraviolet lamp ( λ max = 365 nm), and high cell biocompatibility was found as well. Therefore, the generated AuNCs can be used as fluorescence tracers and nanoprobes. We explored the suitability of AuNCs@dextran as labeling agents for bacteria, such as Staphylococcus aureus and Escherichia coli. After the bacteria were labeled by AuNCs@dextran, they became quite visible under a fluorescence microscope. Additionally, we demonstrated that nanocomposites composed of AuNCs@dextran and silica beads can be readily internalized by cancer cells. The nanocomposites can be readily detected in the cells through their photoluminescence, suggesting possible applications in drug delivery and fluorescence imaging.

  12. Photoluminescence from semiconductor cadmium selenide nanocrystals

    NASA Astrophysics Data System (ADS)

    Nazzal, Amjad Yousef

    In this dissertation, the photoluminescence (PL) emission properties from different CdSe nanocrystals (NCs) dispersed in polymer thin films were investigated. The PL spectroscopy was used as a probing tool to study core and surface-related emission properties of the CdSe NCs under investigation. The results found in these studies are promising from the point of view of fundamental understanding as well as the possible employments of the emission properties of CdSe NCs in certain technological applications. The studies presented in this dissertation include the following: (i) PL polarization spectroscopy of single CdSe NCs was performed on a system of colloidal CdSe quantum rods (QRs). Our experimental measurements suggest a strong polarization dependence of both excitation and emission, and confirm the unique linear dipole in the QRs along the long axis of the rod, i.e. the c axis of wurtzite structure, which is in agreement with the previous theoretical predictions. These results are very important because it represents an experimental test to the available theoretical models used in exploring the rich electronic spectra of these NC systems. These results also show the importance of the shape anisotropy on the electronic spectrum of NCs. (ii) Environmental effects on the PL from highly luminescent bare-core CdSe and core/shell CdSe/ZnS NCs were systematically investigated under different atmospheric environments and photo-irradiation conditions. In this study, the PL was used as a probe to detect changes in the electronic spectrum of the NCs due to photo-induced interactions on the surface of the NCs with the local surrounding atmosphere. Such studies are very important to provide a good understanding of the optimum operational conditions for emission applications of NCs in solid-state devices and also give a simple way of studying the surface of the NCs indirectly by investigating the surface interactions with different molecular systems and their effects on the

  13. Assessing the acidity of high silica chabazite H-SSZ-13 by FTIR using CO as molecular probe: Comparison with H-SAPO-34.

    PubMed

    Bordiga, Silvia; Regli, Laura; Cocina, Donato; Lamberti, Carlo; Bjørgen, Morten; Lillerud, Karl Petter

    2005-02-24

    Zeolitic materials based on the chabazite topology, such as H-SAPO-34, possess unique shape-selectivity properties for converting methanol into light olefins. In addition to the topology, zeolite acidity is inherently linked to catalyst activity and selectivity. The acidic properties of high silica chabazite (H-SSZ-13) have attracted much attention in the past decade because the material represents an idealized model system having one acidic site per cage. Conclusions drawn so far have essentially been founded on quantum chemical methods. An experimentally based benchmark of the acidity of H-SSZ-13 has hitherto not been available. In this work, transmission FTIR spectroscopy provides a description of the different acidic sites of H-SSZ-13 by using CO as molecular probe at 70 K. The results demonstrate that H-SSZ-13 is a strongly Brønsted acidic material, essentially having two distinct families of acidic sites. In contrast to numerous preceding reports, we find it fundamental to consider proton distributions among all four possible sites, and do not delimit the interpretations to only two sites. The present data consistently suggest the most abundant family of protons to have three members being located on different crystalline positions on the eight-membered-ring window giving access to the chabazite cage. Consequently, these protons are exposed to two neighboring cages. The second, and less abundant family, is constituted by only one site that is situated on the six-membered ring defining the top/bottom of the barrel-shaped chabazite cage. This proton is therefore only exposed to one cage and requires a higher CO pressure to form adducts. Toward CO, both families of sites possess the same acidity. Parallel experiments were also carried out for the isostructural and commercially important H-SAPO-34 having an equal density of acidic sites. This is the first attempt to directly compare, on an experimental basis, the acidity of these two materials.

  14. Polyvinyl alcohol as photoluminescent conductive polymer

    NASA Astrophysics Data System (ADS)

    Ruiz-Limón, B.; Wetzel, G. B. J.; Olivares-Pérez, A.; Ponce-Lee, E. L.; Hernández-Garay, M. P.; Páez-Trujillo, G.; Toxqui-López, S.; Fuentes-Tapia, I.

    2007-02-01

    We synthesized a photoluminescent conductor polymer composed of polyvinyl alcohol, which was doped with nickel chloride to decrease its resistivity (300 Ωcm) and benzalkonium chloride to obtain photoluminescence properties, when it is radiated with a green laser beam (532 nm). We compared its absorbance curve and its energy emitted curve to observe the amount energy that is taken advantage of this process. Besides we research the photoluminescence behavior when an electric currant is applied in our conductor polymer, obtaining a modulation capacity.

  15. Identification of PCR-amplified genetically modified organisms (GMOs) DNA by peptide nucleic acid (PNA) probes in anion-exchange chromatographic analysis.

    PubMed

    Rossi, Stefano; Lesignoli, Francesca; Germini, Andrea; Faccini, Andrea; Sforza, Stefano; Corradini, Roberto; Marchelli, Rosangela

    2007-04-04

    PCR products obtained by selective amplification of transgenic DNA derived from food samples containing Roundup Ready soybean or Bt-176 maize have been analyzed by anion-exchange HPLC. Peptide nucleic acids (PNAs), oligonucleotide analogues known to bind to complementary single-stranded DNA with high affinity and specificity, have been used as specific probes in order to assess the identity of the peaks observed. Two different protocols were adopted in order to obtain single-stranded DNA: amplification with an excess of one primer or digestion of one DNA strand. The single-stranded DNA was mixed with the PNA probe, and the presence of a specific sequence was revealed through detection of the corresponding PNA:DNA peak with significantly different retention time. Advantages and limits of this approach are discussed. The method was tested with reference materials and subsequently applied to commercial samples.

  16. A facile carbon dots based fluorescent probe for ultrasensitive detection of ascorbic acid in biological fluids via non-oxidation reduction strategy.

    PubMed

    Kong, Weiheng; Wu, Di; Li, Guoliang; Chen, Xuefeng; Gong, Peiwei; Sun, Zhiwei; Chen, Guang; Xia, Lian; You, Jinmao; Wu, Yongning

    2017-04-01

    A rapid, facile and ultrasensitive fluorescence sensing system based on nitrogen-doped carbon dots (N-doped CDs) for the detection of ascorbic acid (AA) was developed. The highly photoluminescent N-doped CDs with excellent solubility in water and good biocompatibility were prepared by a one-step hydrothermal synthesis and gave the fluorescence quantum yield of 47%. The addition of AA can intensively suppress the fluorescence of the N-doped CDs through the synergistic effect of the inner filter effect (IFE) and the static quenching effect (SQE). Benefited from the remarkable synergistic effect of IFE and SQE, a facile and ultrasensitive sensor was constructed successfully for AA sensing. The detection procedure was achieved within 2min. The linear response range of AA was obtained from 10(-3) to 10(-8) M with a detection limit of 5nM. This developed method enjoyed many merits including more simplicity, lost cost, high sensitivity, good selectivity, rapid response and excellent biocompatibility. Notably, the proposed fluorescent sensor exhibits excellent performance and applicability for AA determination in human serum and rat brain microdialysate, and may provide a fast yet facile route for AA detection in physiological and pathological fields.

  17. Changing interfaces: Photoluminescent ZnO nanoparticle powders in different aqueous environments

    NASA Astrophysics Data System (ADS)

    Kocsis, Krisztina; Niedermaier, Matthias; Bernardi, Johannes; Berger, Thomas; Diwald, Oliver

    2016-10-01

    We transformed vapor phase grown ZnO nanoparticle powders into aqueous ZnO nanoparticle dispersions and studied the impact of associated microstructure and interface property changes on their spectroscopic properties. With photoluminescence (PL) spectroscopy, we probed oxygen interstitials Oi2 - in the near surface region and tracked their specific PL emission response at hvEM = 2.1 eV during the controlled conversion of the solid-vacuum into the solid-liquid interface. While oxygen adsorption via the gas phase does affect the intensity of the PL emission bands, the O2 contact with ZnO nanoparticles across the solid-liquid interface does not. Moreover, we found that the near band edge emission feature at hvEM = 3.2 eV gains relative intensity with regard to the PL emission features in the visible light region. Searching for potential PL indicators that are specific to early stages of particle dissolution, we addressed for aqueous ZnO nanoparticle dispersions the effect of formic acid adsorption. In the absence of related spectroscopic features, we were able to consistently track ZnO nanoparticle dissolution and the concomitant formation of solvated Zinc formate species by means of PL and FT-IR spectroscopy, dynamic light scattering, and zeta potential measurements. For a more consistent and robust assessment of nanoparticle properties in different continuous phases, we discuss characterization challenges and potential pitfalls that arise upon replacing the solid-gas with the solid-liquid interface.

  18. Cellular delivery of quantum dot-bound hybridization probe for detection of intracellular pre-microRNA using chitosan/poly(γ-glutamic acid) complex as a carrier.

    PubMed

    Geng, Yao; Lin, Dajie; Shao, Lijia; Yan, Feng; Ju, Huangxian

    2013-01-01

    A quantum dot (QD)-bound hybridization probe was designed for detection of intracellular pre-miRNA using chitosan (CS)/poly(γ-glutamic acid) (γ-PGA) complex as a gene vector. The probe was prepared by assembling thiolated RNA to gold nanoparticle (Au NP) via Au-S bond and then binding 3'-end amine of the RNA to the carboxy group capped on quantum dot surface. The QD-RNA-Au NP probe was assembled on the vector by mixing with aqueous γ-PGA solution and then CS solution to construct a gene delivery system for highly effective cellular uptake and delivery. After the probe was released from CS/γ-PGA complex to the cytoplasm by electrostatic repulsion at intracellular pH, it hybridized with pre-miRNA precursor as target. The formed product was then cleaved by RNase III Dicer, leading to the separation of QDs from Au NPs and fluorescence emission of QDs, which could be detected by confocal microscopic imaging to monitor the amount of the intracellular pre-miRNA precursor. The in vitro assays revealed that the QD-RNA-Au NP was a robust, sensitive and selective probe for quantitative detection of target pre-miRNA. Using MDA-MB231 and MCF-7 breast cancer cells as models, the relative amount of pre-miRNA let-7a could be successfully compared. Since the amount of miRNA is related to the progress and prognosis of cancer, this strategy could be expected to hold promising application potential in medical research and clinical diagnostics.

  19. Plasmonically enhanced photoluminescence of nanoscale semiconductors

    NASA Astrophysics Data System (ADS)

    Abraham, Gabrielle; Tejerina, Alejandro; Churchill, Hugh; Bajwa, Pooja; Heyes, Collin; Herzog, Joseph B.

    2016-03-01

    Recent work has shown that plasmonic structures enhance the emitted light of nanoscale semiconductor materials, such as the photoluminescence of colloidal quantum dots (QDs) and MoS2 2D materials. This project will compare the photoluminescence of CdSe colloidal quantum dots and MoS2. A variety of studies will be performed such as photobleaching effects, how photoluminescence relates to lifetime of sample, and polarization studies. In addition, this project will further the understanding of plasmonically enhanced photoluminescence between these semiconductor nanostructures and metal nanostructures. Initial studies will drop cast colloidal metal nanospheres onto quantum dots and MoS2, while future work will fabricate gold structures with electron beam lithography.

  20. Time-Resolved Photoluminescence and Photovoltaics

    SciTech Connect

    Metzger, W. K.; Ahrenkiel, R. K.; Dippo, P.; Geisz, J.; Wanlass, M. W.; Kurtz, S.

    2005-01-01

    The time-resolved photoluminescence (TRPL) technique and its ability to characterize recombination in bulk photovoltaic semiconductor materials are reviewed. Results from a variety of materials and a few recent studies are summarized and compared.

  1. Differentiating among plant spectra by combining pH dependent photoluminescence spectroscopy with multi-way principal component analysis (MPCA)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowing the botanical composition of the standing crop is essential for managing ecosystem health and herbivory. Photoluminescence spectroscopic probes offer the potential for real-time measurements of animal diet composition. Spectral emission signatures (excitation at 365 nm) from three different ...

  2. Sensitive, Efficient Quantitation of 13C-Enriched Nucleic Acids via Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry for Applications in Stable Isotope Probing.

    PubMed

    Wilhelm, Roland; Szeitz, András; Klassen, Tara L; Mohn, William W

    2014-12-01

    Stable isotope probing (SIP) of nucleic acids is a powerful tool for studying the functional traits of microbial populations within complex communities, but SIP involves a number of technical challenges. Many of the difficulties in DNA-SIP and RNA-SIP experiments can be effectively overcome with an efficient, sensitive method for quantitating the isotopic enrichment of nucleic acids. Here, we present a sensitive method for quantitating (13)C enrichment of nucleic acids, requiring a few nanograms of sample, and we demonstrate its utility in typical DNA-SIP and RNA-SIP experiments. All five nucleobases (adenine, guanine, cytosine, thymine, and uracil) were separated and detected by using ultrahigh-performance liquid chromatography-tandem mass spectrometry. We detected all isotopic species in samples with as low as 1.5 atom% (13)C above natural abundance, using 1-ng loadings. Quantitation was used to characterize the isotopic enrichment kinetics of cellulose- and lignin-based microcosm experiments and to optimize the recovery of enriched nucleic acids. Application of our method will minimize the quantity of expensive isotopically labeled substrates required and reduce the risk of failed experiments due to insufficient recovery of labeled nucleic acids for sequencing library preparation.

  3. Sensitive, Efficient Quantitation of 13C-Enriched Nucleic Acids via Ultrahigh-Performance Liquid Chromatography–Tandem Mass Spectrometry for Applications in Stable Isotope Probing

    PubMed Central

    Wilhelm, Roland; Szeitz, András; Klassen, Tara L.

    2014-01-01

    Stable isotope probing (SIP) of nucleic acids is a powerful tool for studying the functional traits of microbial populations within complex communities, but SIP involves a number of technical challenges. Many of the difficulties in DNA-SIP and RNA-SIP experiments can be effectively overcome with an efficient, sensitive method for quantitating the isotopic enrichment of nucleic acids. Here, we present a sensitive method for quantitating 13C enrichment of nucleic acids, requiring a few nanograms of sample, and we demonstrate its utility in typical DNA-SIP and RNA-SIP experiments. All five nucleobases (adenine, guanine, cytosine, thymine, and uracil) were separated and detected by using ultrahigh-performance liquid chromatography–tandem mass spectrometry. We detected all isotopic species in samples with as low as 1.5 atom% 13C above natural abundance, using 1-ng loadings. Quantitation was used to characterize the isotopic enrichment kinetics of cellulose- and lignin-based microcosm experiments and to optimize the recovery of enriched nucleic acids. Application of our method will minimize the quantity of expensive isotopically labeled substrates required and reduce the risk of failed experiments due to insufficient recovery of labeled nucleic acids for sequencing library preparation. PMID:25217022

  4. Design of Selenium-Based Chiral Chemical Probes for Simultaneous Enantio- and Chemosensing of Chiral Carboxylic Acids with Remote Stereogenic Centers by NMR Spectroscopy.

    PubMed

    Shyshkanov, Sergey A; Orlov, Nikolai V

    2016-10-17

    Selenium-based enantiopure chiral chemical probes have been designed in a modular way starting from available amino alcohols. The probes developed were found to be efficient in chemoselective interaction with carboxylic functions of chiral substrates leading to diastereomeric amide formation and in sensing α-, β-, and remote (up to seven bonds away from the carboxylic group) chiral centers by using (77) Se NMR spectroscopy. As a result, it was possible to determine the enantiomeric ratio of structurally diverse individual chiral acids including polyfunctional compounds and drugs with high accuracy. An approach to analyzing the crude reaction mixtures has been successfully developed by using bifunctional selenium- and fluorine-containing chiral probes. More importantly, it was revealed that, based on the (77) Se NMR data obtained, it is possible to obtain primary information about the location and nature of the substituents at the chiral center (chemo- and enantiosensing), which can simplify the structural elucidation of complex compounds. The derivatization procedure takes as little as 5 min and can be performed directly in an NMR tube followed by NMR measurements without any isolation and purification steps.

  5. Screening of Israeli Holstein-Friesian cattle for restriction fragment length polymorphisms using homologous and heterologous deoxyribonucleic acid probes.

    PubMed

    Hallerman, E M; Nave, A; Soller, M; Beckmann, J S

    1988-12-01

    Genomic DNA of Israeli Holstein-Friesian dairy cattle were screened with a battery of 17 cloned or subcloned DNA probes in an attempt to document restriction fragment length polymorphisms at a number of genetic loci. Restriction fragment length polymorphisms were observed at the chymosin, oxytocin-neurophysin I, lutropin beta, keratin III, keratin VI, keratin VII, prolactin, and dihydrofolate reductase loci. Use of certain genomic DNA fragments as probes produced hybridization patterns indicative of satellite DNA at the respective loci. Means for distinguishing hybridizations to coding sequences for unique genes from those to satellite DNA were developed. Results of this study are discussed in terms of strategy for the systematic development of large numbers of bovine genomic polymorphisms.

  6. Incorporation of extra amino acids in peptide recognition probe to improve specificity and selectivity of an electrochemical peptide-based sensor.

    PubMed

    Zaitouna, Anita J; Maben, Alex J; Lai, Rebecca Y

    2015-07-30

    We investigated the effect of incorporating extra amino acids (AA) at the n-terminus of the thiolated and methylene blue-modified peptide probe on both specificity and selectivity of an electrochemical peptide-based (E-PB) HIV sensor. The addition of a flexible (SG)3 hexapeptide is, in particular, useful in improving sensor selectivity, whereas the addition of a highly hydrophilic (EK)3 hexapeptide has shown to be effective in enhancing sensor specificity. Overall, both E-PB sensors fabricated using peptide probes with the added AA (SG-EAA and EK-EAA) showed better specificity and selectivity, especially when compared to the sensor fabricated using a peptide probe without the extra AA (EAA). For example, the selectivity factor recorded in the 50% saliva was ∼2.5 for the EAA sensor, whereas the selectivity factor was 7.8 for both the SG-EAA and EK-EAA sensors. Other sensor properties such as the limit of detection and dynamic range were minimally affected by the addition of the six AA sequence. The limit of detection was 0.5 nM for the EAA sensor and 1 nM for both SG-EAA and EK-EAA sensors. The saturation target concentration was ∼200 nM for all three sensors. Unlike previously reported E-PB HIV sensors, the peptide probe functions as both the recognition element and antifouling passivating agent; this modification eliminates the need to include an additional antifouling diluent, which simplifies the sensor design and fabrication protocol.

  7. Fluorescence sensing of phosdrin pesticide by the luminescent Eu(III)- and Tb(III)-bis(coumarin-3-carboxylic acid) probes

    NASA Astrophysics Data System (ADS)

    Hussein, Belal H. M.; Khairy, Gasser M.; Kamel, Rasha M.

    2016-04-01

    Luminescence quenching of the Eu(III)- and Tb(III)-bis (coumarin-3-carboxylic acid) (Ln(III)-(CCA)2) probes has been studied in the presence of organophosphorus or organochlorine pesticides; Phosdrin (P1), Malathion (P2), Profenofos (P3), Formothion (P4), Heptachlor (P5), and Endosulfan (P6). The luminescence intensity of lanthanide complex probes Ln(III)-(CCA)2 decreases as the concentration of the Phosdrin pesticide increases, while the other investigated pesticides have no significant influence on the lanthanide fluorescent intensities. It is observed that the quenching of Eu(III) and Tb(III)-coumarin-3-carboxylic acid by Phosdrin proceeds via static quenching processes according to Stern-Volmer plot. The binding constants (K) and the thermodynamic parameters of the interaction of Ln(III)-(CCA)2 with Phosdrin have been determined. A direct method for the determination of the Phosdrin in ethanol has been developed based on the luminescence changes of the Ln(III)-(CCA)2-phosdrin ternary complexes. The detection limits of P1 were 6.28 and 1.07 μM in case of Eu(III) and Tb(III)-complex, respectively. The influence of various interfering species on the detection of P1 has been investigated to assess the analytical applicability of the method. The new method was applied to determine the Phosdrin pesticide in different types of water samples.

  8. Probing the General Time Scale Question of Boronic Acid Binding with Sugars in Aqueous Solution at Physiological pH

    PubMed Central

    Ni, Nanting; Laughlin, Sarah; Wang, Yingji; Feng, You; Zheng, Yujun

    2012-01-01

    The boronic acid group is widely used in chemosensor design due to its ability to reversibly bind diol-containing compounds. The thermodynamic properties of the boronic acid-diol binding process have been investigated extensively. However, there are few studies of the kinetic properties of such binding processes. In this report, stopped-flow method was used for the first time to study the kinetic properties of the binding between three model arylboronic acids, 4-, 5-, and 8-isoquinolinylboronic acids, and various sugars. With all the boronic acid-diol pair sexamined, reactions were complete within seconds. The kon values with various sugars follow the order of D-fructose >D-tagatose>D-mannose >D-glucose. This trend tracks the thermodynamic binding affinities for these sugars and demonstrates that the “on” rate is the key factor determining the binding constant. PMID:22464680

  9. Probing the origin of acetyl-CoA and oxaloacetate entering the citric acid cycle from the 13C labeling of citrate released by perfused rat hearts.

    PubMed

    Comte, B; Vincent, G; Bouchard, B; Des Rosiers, C

    1997-10-17

    We present a strategy for simultaneous assessment of the relative contributions of anaplerotic pyruvate carboxylation, pyruvate decarboxylation, and fatty acid oxidation to citrate formation in the perfused rat heart. This requires perfusing with a mix of 13C-substrates and determining the 13C labeling pattern of a single metabolite, citrate, by gas chromatography-mass spectrometry. The mass isotopomer distributions of the oxaloacetate and acetyl moieties of citrate allow calculation of the flux ratios: (pyruvate carboxylation)/(pyruvate decarboxylation), (pyruvate carboxylation)/(citrate synthesis), (pyruvate decarboxylation)/(citrate synthesis) (pyruvate carboxylation)/(fatty acid oxidation), and (pyruvate decarboxylation)/(fatty acid oxidation). Calculations, based on precursor-product relationship, are independent of pool size. The utility of our method was demonstrated for hearts perfused under normoxia with [U-13C3](lactate + pyruvate) and [1-13C]octanoate under steady-state conditions. Under these conditions, effluent and tissue citrate were similarly enriched in all 13C mass isotopomers. The use of effluent citrate instead of tissue citrate allows probing substrate fluxes through the various reactions non-invasively in the intact heart. The methodology should also be applicable to hearts perfused with other 13C-substrates, such as 1-13C-labeled long chain fatty acid, and under various conditions, provided that assumptions on which equations are developed are valid.

  10. Acid-base equilibrium dynamics in methanol and dimethyl sulfoxide probed by two-dimensional infrared spectroscopy.

    PubMed

    Lee, Chiho; Son, Hyewon; Park, Sungnam

    2015-07-21

    Two-dimensional infrared (2DIR) spectroscopy, which has been proven to be an excellent experimental method for studying thermally-driven chemical processes, was successfully used to investigate the acid dissociation equilibrium of HN3 in methanol (CH3OH) and dimethyl sulfoxide (DMSO) for the first time. Our 2DIR experimental results indicate that the acid-base equilibrium occurs on picosecond timescales in CH3OH but that it occurs on much longer timescales in DMSO. Our results imply that the different timescales of the acid-base equilibrium originate from different proton transfer mechanisms between the acidic (HN3) and basic (N3(-)) species in CH3OH and DMSO. In CH3OH, the acid-base equilibrium is assisted by the surrounding CH3OH molecules which can directly donate H(+) to N3(-) and accept H(+) from HN3 and the proton migrates through the hydrogen-bonded chain of CH3OH. On the other hand, the acid-base equilibrium in DMSO occurs through the mutual diffusion of HN3 and N3(-) or direct proton transfer. Our 2DIR experimental results corroborate different proton transfer mechanisms in the acid-base equilibrium in protic (CH3OH) and aprotic (DMSO) solvents.

  11. A Rapid Approach for Fabricating Boronic Acid-Functionalized Plates for On-Probe Detection of Glycoprotein and Glycopeptide

    PubMed Central

    Liu, Yu-Ching; Chen, Chao-Jung

    2017-01-01

    We developed a rapid and simple approach without using complex mechanical or chemical protocols to fabricate boronic acid-functionalized plates for glycoprotein or glycopeptide enrichment and mass spectrometry (MS) analysis. By coating the boronic acid-functionalized silica particles on a polydimethylsiloxane (PDMS)-coated matrix-assisted laser desorption/ionization (MALDI) plate, these particles can form a firmly monolayer of particles on PDMS membrane for sample handling without peeling off. The boronic acid particles-coated PDMS plate (BP plate) was successfully applied to the enrichment of horseradish peroxidase (HRP) protein and their digested glycopeptides. PMID:28337401

  12. Boron-doped graphene quantum dots for selective glucose sensing based on the "abnormal" aggregation-induced photoluminescence enhancement.

    PubMed

    Zhang, Li; Zhang, Zhi-Yi; Liang, Ru-Ping; Li, Ya-Hua; Qiu, Jian-Ding

    2014-05-06

    A hydrothermal approach for the cutting of boron-doped graphene (BG) into boron-doped graphene quantum dots (BGQDs) has been proposed. Various characterizations reveal that the boron atoms have been successfully doped into graphene structures with the atomic percentage of 3.45%. The generation of boronic acid groups on the BGQDs surfaces facilitates their application as a new photoluminescence (PL) probe for label free glucose sensing. It is postulated that the reaction of the two cis-diol units in glucose with the two boronic acid groups on the BGQDs surfaces creates structurally rigid BGQDs-glucose aggregates, restricting the intramolecular rotations and thus resulting in a great boost in the PL intensity. The present unusual "aggregation-induced PL increasing" sensing process excludes any saccharide with only one cis-diol unit, as manifested by the high specificity of BGQDs for glucose over its close isomeric cousins fructose, galactose, and mannose. It is believed that the doping of boron can introduce the GQDs to a new kind of surface state and offer great scientific insights to the PL enhancement mechanism with treatment of glucose.

  13. A sensitive gel-based method combining distinct cyclophellitol-based probes for the identification of acid/base residues in human retaining β-glucosidases.

    PubMed

    Kallemeijn, Wouter W; Witte, Martin D; Voorn-Brouwer, Tineke M; Walvoort, Marthe T C; Li, Kah-Yee; Codée, Jeroen D C; van der Marel, Gijsbert A; Boot, Rolf G; Overkleeft, Herman S; Aerts, Johannes M F G

    2014-12-19

    Retaining β-exoglucosidases operate by a mechanism in which the key amino acids driving the glycosidic bond hydrolysis act as catalytic acid/base and nucleophile. Recently we designed two distinct classes of fluorescent cyclophellitol-type activity-based probes (ABPs) that exploit this mechanism to covalently modify the nucleophile of retaining β-glucosidases. Whereas β-epoxide ABPs require a protonated acid/base for irreversible inhibition of retaining β-glucosidases, β-aziridine ABPs do not. Here we describe a novel sensitive method to identify both catalytic residues of retaining β-glucosidases by the combined use of cyclophellitol β-epoxide- and β-aziridine ABPs. In this approach putative catalytic residues are first substituted to noncarboxylic amino acids such as glycine or glutamine through site-directed mutagenesis. Next, the acid/base and nucleophile can be identified via classical sodium azide-mediated rescue of mutants thereof. Selective labeling with fluorescent β-aziridine but not β-epoxide ABPs identifies the acid/base residue in mutagenized enzyme, as only the β-aziridine ABP can bind in its absence. The Absence of the nucleophile abolishes any ABP labeling. We validated the method by using the retaining β-glucosidase GBA (CAZy glycosylhydrolase family GH30) and then applied it to non-homologous (putative) retaining β-glucosidases categorized in GH1 and GH116: GBA2, GBA3, and LPH. The described method is highly sensitive, requiring only femtomoles (nanograms) of ABP-labeled enzymes.

  14. Dopamine-functionalized InP/ZnS quantum dots as fluorescence probes for the detection of adenosine in microfluidic chip

    PubMed Central

    Ankireddy, Seshadri Reddy; Kim, Jongsung

    2015-01-01

    Microbeads are frequently used as solid supports for biomolecules such as proteins and nucleic acids in heterogeneous microfluidic assays. Chip-based, quantum dot (QD)-bead-biomolecule probes have been used for the detection of various types of DNA. In this study, we developed dopamine (DA)-functionalized InP/ZnS QDs (QDs-DA) as fluorescence probes for the detection of adenosine in microfluidic chips. The photoluminescence (PL) intensity of the QDs-DA is quenched by Zn2+ because of the strong coordination interactions. In the presence of adenosine, Zn2+ cations preferentially bind to adenosine, and the PL intensity of the QDs-DA is recovered. A polydimethylsiloxane-based microfluidic chip was fabricated, and adenosine detection was confirmed using QDs-DA probes. PMID:26347351

  15. Site-selective transient photoluminescence enhancement of impurity-trapped excitons in NaMgF3:Yb2+

    NASA Astrophysics Data System (ADS)

    Hughes-Currie, Rosa B.; Senanayake, Pubudu S.; Wells, Jon-Paul R.; Reid, Michael F.; Berden, Giel; Reeves, Roger J.; Meijerink, Andries

    2013-09-01

    The excited-state structure of impurity-trapped excitons are measured in a multisite system. We use a two-color (UV-IR) pulsed photoluminescence enhancement technique, which probes the interlevel transitions and dynamics of impurity-trapped excitons in doped insulating phosphor materials. The technique is applied to NaMgF3:Yb2+, which exhibits emission from two charge-compensation centers with peaks at 22300 cm-1 (448 nm) and 24000 cm-1 (417 nm). The observed photoluminescence enhancement is caused by a combination of intraexcitonic excitation and electron trap liberation. The electron traps are inferred to have a depth of approximately 800 cm-1.

  16. Biopolymer-mediated analyte detection via photoluminescence modulation of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Heller, Daniel

    Single-walled carbon nanotubes (SWNT) have unique photo-physical properties which, through the work in this dissertation, are investigated and harnessed to produce optical sensors with unique capabilities. Early studies of the modulation of SWNT optical properties---both photoluminescence and resonance Raman scattering---demonstrate their tunable nature. Solution dispersed SWNT are sorted by length and the photoluminescence quantum yield is shown to increase nonlinearly with length, suggesting that SWNT ends quench the exciton. The change in Raman scattering cross section and resonant window is mapped as a function of SWNT aggregation, as well as sonochemical effects on photoluminescence. Nanotube photoluminescence and scattering are then detected, via imaging and spectrometry, from within live murine macrophage cells, and shown to be extremely resilient, demonstrating the potential of nanotube-based molecular probes and biosensors. The work culminates in several major findings in optical sensing. We show that a nanotube-ds(GT)15 DNA complex can detect genotoxic analytes by solvatochromism, and measure this from within live cells and tissues in real-time. We find that such optical signals can be multiplexed, resulting in analyte fingerprinting, and a bioanalyte can be detected at the single-molecule level stochastic operation of such sensors. These concepts are employed to detect, identify, and measure bioanalytes, such as reactive oxygen species, as well as explosives, such as TNT and RDX, with single-molecule sensitivity.

  17. A comparative IR characterization of acidic sites on HY zeolite by pyridine and CO probes with silica-alumina and γ-alumina references.

    PubMed

    Kondo, Junko N; Nishitani, Ryoko; Yoda, Eisuke; Yokoi, Toshiyuki; Tatsumi, Takashi; Domen, Kazunari

    2010-10-07

    Using IR spectroscopy, three different surface states of HY zeolite were probed by successive adsorption of CO at 143 K followed by evacuation and pyridine adsorption at 523 K: HY zeolite [1] without strong Lewis acid sites (LAS); [2] after high temperature (873 K) evacuation to convert Brønsted acid sites (BAS) to strong LAS; and [3] after water re-adsorption on HY zeolite [2] to recover BAS from LAS. The original surface of HY zeolite [1] seemed to be recovered on HY zeolite [3] after high temperature evacuation and water treatment by CO adsorption, while a part of generated LAS on HY zeolite [2] seemed irreversible on HY zeolite [3] to HY zeolite [1] by pyridine adsorption. To clarify this discrepancy, re-examination of the IR spectra of adsorbed CO and pyridine on γ-alumina and silica-alumina after similar treatments to those on HY zeolite was conducted. Based on the results of CO adsorption on γ-alumina and silica-alumina, the presence of extra-framework aluminium sites on HY zeolite [1] was confirmed. High temperature evacuation of HY zeolite [1] formed very strong LAS, a part of which was irreversible to BAS by water re-adsorption at room temperature. The irreversible sites on HY zeolite [3] were assigned to non-acidic OH groups attributed to silica-alumina. The non-acidic OH groups on HY zeolite [3], which were BAS on HY zeolite [1], hydrogen-bonded to pyridine to show IR spectra similar to those adsorbed on LAS. Thus, LAS on HY zeolite [3] seemed irreversible by pyridine adsorption after water re-adsorption. On the other hand, CO adsorbed on non-acidic OH groups showed a band at only slightly lower frequency (2160 cm(-1)) than that of BAS (2178 cm(-1)), resulting in overlapps and ignoring their presence. Thus, CO adsorption seemed to show that complete recovery of LAS to BAS occurred.

  18. [Measurement of fruit maturity based on laser-induced photoluminescence spectrum].

    PubMed

    Wang, Le-yan; Zhang, Dong-xian; Zhang, Hai-jun; Wang, Xiao-ping

    2008-12-01

    Grounding on the concepts of biophotonics measurement, the authors first used a red semiconductor laser (655 nm) to irradiate fruits. Compared with other kinds of illuminating sources, the red semiconductor laser is less expensive and takes little space. The laser-induced photoluminescence spectrums could be detected by coupling fibre-optics probe when the fruits are illuminated by laser. And the spectrum has a distinct peak of relative intensity around the 685 nm wavelength that varies with the degree of fruit maturity. Sugar content measurement was used to prove the laser-induced photoluminescence measurement. The authors tested the sugar content of the fruit specimens, and found that the relative peak value of the fruits' laser-induced photoluminescence spectrum decreases with the increase in their sugar content. The authors used partial least-squares (PLS) regression to perform an analysis of the relationship between the laser-induced photoluminescence intensity and the sugar content, fitting a curve of the two parameters. The correlation coefficient r of the fitted value and the actual value is 98.92% for red-inside plum and 97.31% for nectarine. So the authors could generalize that there is an approximate linear relationship between the peak value of laser-induced photoluminescence intensity and the sugar content of fruits, and we could use the maturity measurement based on this concept to decide the fruit ripeness. The authors designed the analytic program for this laser-induced photoluminescence spectrum measurement system, which mainly realizes two functions: generating the standard ripe spectrum of a certain kind of fruit from a quantity of their spectra, and, according to this standard spectrum, determining the maturity degree of an unknown spectrum, and at the same time, displaying the unknown laser-induced photoluminescence spectrum. Incorporating this analytic program with the optical spectrometer, it becomes conceivable to test the fruit maturity

  19. Single glass nanopore-based regenerable sensing platforms with a non-immobilized polyglutamic acid probe for selective detection of cupric ions.

    PubMed

    Chen, Lizhen; He, Haili; Xu, Xiaolong; Jin, Yongdong

    2015-08-19

    A single glass capillary nanopore-based sensing platform for rapid and selective detection of cupric ions is demonstrated by utilizing polyglutamic acid (PGA) as a non-immobilized probe. The detection is based on the significant decrease of ionic current through nanopore and the reversal of ion current rectification responses induced by the chelated cupric ions on the probes when in the presence of cupric ions. PGA shows high selectivity for detecting cupric ions rather than other metal ions. The sensitivity of the sensing platform can be improved about 1-2 orders of magnitude by employing asymmetric salt gradients during the measurements. And the PGA-based nanopore sensing platform shows excellent regenerability for Cu(2+) sensing applications. In addition, the method is found effective and reliable for the detection of cupric ions in real samples with small volume down to 20 μL. This nanopore-based sensing platform will find promising practical applications for the detection of cupric ions.

  20. Highly photoluminescent MoO(x) quantum dots: Facile synthesis and application in off-on Pi sensing in lake water samples.

    PubMed

    Xiao, Sai Jin; Zhao, Xiao Jing; Zuo, Jun; Huang, Hai Qing; Zhang, Li

    2016-02-04

    Molybdenum oxide (MoOx) is a well-studied transition-metal semiconductor material, and has a wider band gap than MoS2 which makes it become a promising versatile probe in a variety of fields, such as gas sensor, catalysis, energy storage ect. However, few MoOx nanomaterials possessing photoluminescence have been reported until now, not to mention the application as photoluminescent probes. Herein, a one-pot method is developed for facile synthesis of highly photoluminescent MoOx quantum dots (MoOx QDs) in which commercial molybdenum disulfide powder and hydrogen peroxide (H2O2) are involved as the precursor and oxidant, respectively. Compared with current synthesis methods, the proposed one has the advantages of rapid, one-pot, easily prepared, environment friendly as well as strong photoluminescence. The obtained MoOx QDs is further utilized as an efficient photoluminescent probe, and a new off-on sensor has been constructed for phosphate (Pi) determination in complicated lake water samples, attributed to the fact that the binding affinity of Eu(3+) ions to the oxygen atoms from Pi is much higher than that from the surface of MoOx QDs. Under the optimal conditions, a good linear relationship was found between the enhanced photoluminescence intensity and Pi concentration in the range of 0.1-160.0 μM with the detection limit of 56 nM (3σ/k). The first application of the photoluminescent MoOx nanomaterials for ion photochemical sensing will open the gate of employing MoOx nanomaterials as versatile probes in a variety of fields, such as chemi-/bio-sensor, cell imaging, biomedical and so on.

  1. Probing metal ion complexation with salicylic acid and its derivatives with excited state proton transfer and luminescence anisotropy

    SciTech Connect

    Wang, Z.; Friedrich, D.M.; Ainsworth, C.C.

    1996-10-01

    Salicylic acid and its derivatives in which the phenolic proton is preserved show a characteristic dual fluorescence: one band in the UV, due to a {open_quotes}normal{close_quotes} excited state emission, and the other in the visible range, is assigned to excited state intramolecular proton transfer (ESIPT). The transition energy, quantum yield and fluorescence lifetime as well as fluorescence anisotropy are sensitive to the solvent environment, temperature and properties of the substituents (complexation) at the phenolic and carboxylic oxygens. The ESIPT band disappears in molecules in which the intramolecular hydrogen bond between phenolic hydrogen and the carbonyl oxygen is prohibited. In this work, the complexation of Na(I), Ca(II), Al(III) and La(III) with salicylic acid, 3-hydroxybenzoic acid, methylsalicylate and anisic acid in both aqueous and non-aqueous solvents has been studied by absorption and steady state luminescence spectroscopy, picosecond to nanosecond luminescence lifetimes and luminescence anisotropy measurements in a range of solvent and in ethanol at 77 K. Speciation in these complex systems, binding characteristics between the metal ion and the ligand, and ligand-centered energetics are discussed in terms of the spectroscopic properties, luminescence and anisotropy decay kinetics.

  2. Probing thermal stability of the β-lactoglobulin-oleic acid complex by fluorescence spectroscopy and molecular modeling

    NASA Astrophysics Data System (ADS)

    Simion (Ciuciu), Ana-Maria; Aprodu, Iuliana; Dumitrașcu, Loredana; Bahrim, Gabriela Elena; Alexe, Petru; Stănciuc, Nicoleta

    2015-09-01

    Bovine β-lactoglobulin is able to interact with different bioactive compounds, thus being an important candidate in the development of delivery systems with improved functionality. The heat induced changes in the β-lactoglobulin-oleic acid complex were examined by means of fluorescence spectroscopy and molecular modeling techniques. Fluorescence spectroscopy results indicated a rigid protein structure in the temperature range 25-70 °C, whereas at temperatures over 75 °C, the rearrangements of the polypeptide chains led to higher exposure of hydrophobic residues. The most significant increase of the accessible surface area with temperature increase was identified in case of Tyr99 and Tyr102. The phase diagram method indicated an all or none transition between two conformations. Due to conformational changes, no contact between Ile56 or Lys60 and the fatty acid could be identified at 85 °C, but new non-bonding interaction were established with Ile12 and Val15. The results obtained in this study provide important details about thermal induced changes in the conformation of β-lactoglobulin-oleic acid complex. Significant conformational changes were registered above 75 °C, suggesting the possibility of obtaining highly functional complexes between whey proteins and natural unsaturated fatty acids.

  3. Probing High School Students' Cognitive Structures and Key Areas of Learning Difficulties on Ethanoic Acid Using the Flow Map Method

    ERIC Educational Resources Information Center

    Zhou, Qing; Wang, Tingting; Zheng, Qi

    2015-01-01

    The purpose of this study was primarily to explore high school students' cognitive structures and to identify their learning difficulties on ethanoic acid through the flow map method. The subjects of this study were 30 grade 1 students from Dong Yuan Road Senior High School in Xi'an, China. The interviews were conducted a week after the students…

  4. Dopamine functionalized-CdTe quantum dots as fluorescence probes for l-histidine detection in biological fluids.

    PubMed

    Shi, Fanping; Liu, Siyu; Su, Xingguang

    2014-07-01

    In this paper, we developed dopamine functionalized-CdTe quantum dots as fluorescence probes for the determination of l-histidine. Firstly, CdTe was covalently linked to dopamine to form a kind of fluorescence sensor with pyrocatechol structure on the surface. The photoluminescence intensity of CdTe-dopamine (QDs-DA) could be quenched by Ni(2+) due to the strong coordination interaction between the pyrocatechol structure of QDs-DA and Ni(2+). In the presence of l-histidine, Ni(2+) preferred to bind with l-histidine due to high affinity of Ni(2+) to l-histidine and the photoluminescence intensity of QDs-DA was recovered. The recovered photoluminescence intensity of QDs-DA was proportional to the concentration of l-histidine in the ranges of 1.0×10(-6)-1.0×10(-4)mol L(-1) and the detection limit was 5.0×10(-7)mol L(-1) respectively. The established method showed a good selectivity for l-histidine among other common amino acids, and it was applied for determination of l-histidine in human serum sample with satisfactory results.

  5. Spectrophotometric probe

    DOEpatents

    Prather, W.S.; O'Rourke, P.E.

    1994-08-02

    A support structure is described bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe. 3 figs.

  6. Spectrophotometric probe

    DOEpatents

    Prather, William S.; O'Rourke, Patrick E.

    1994-01-01

    A support structure bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe.

  7. Probing pH and pressure effects on the apomyoglobin heme pocket with the 2'-(N,N-dimethylamino)-6-naphthoyl-4-trans-cyclohexanoic acid fluorophore.

    PubMed Central

    Sire, O; Alpert, B; Royer, C A

    1996-01-01

    The environmentally sensitive fluorophore 2'-(N,N-dimethylamino)-6-naphthoyl-4-trans-cyclohexanoic acid (DANCA) has been used to probe the apomyoglobin heme pocket. The unexpected polarity of this domain is generally interpreted as arising from dynamic dipolar relaxation of the peptide dipoles surrounding the heme pocket. In the present work we reexamine the photophysical properties of DANCA in a variety of solvents and complexed with apomyoglobin (apoMb) to further probe the heme pocket environment as a function of external solvent conditions. Absorption and excitation spectra in a number of solvents are consistent with the well-known pi*<--pi (LE) and pi*<--n (CT) electronic absorption transitions observed for naphthylamine derivatives. Dual emission is also a well-documented property of such derivatives. Based on the time scale of the heterogeneity in the decay of the DANCA fluorophore observed in a series of solvents, we propose that the emission properties of DANCA in apoMb are not uniquely attributable to dynamic relaxation events, but also reflect dual emission from both a long-lived, red CT state and the shorter-lived, blue LE state. The pH studies in the range of pH 5-9 of the emission properties of DANCA in apoMb support this hypothesis. They also suggest a specific interaction of DANCA with one or both of the pocket histidyl residues, which leads to a drastic static quenching and red shift of the bound DANCA fluorescence upon protonation. Similar effects are observed with increasing pressure, indicating that these two perturbations alter the DANCA-apoMb complex in a similar fashion. The pressure-induced form of the protein is distinct both energetically and structurally from the previously characterized acid intermediate, in that it is populated above pH 5 and retains a significant degree of integrity of the heme pocket. PMID:8744328

  8. Detection of hydrogen sulfide through photoluminescence quenching of penicillamine-copper nanocluster aggregates

    NASA Astrophysics Data System (ADS)

    Ma, Jia-Ying; Chen, Po-Cheng; Chang, Huan-Tsung

    2014-05-01

    We have developed a one-pot, inexpensive, simple and rapid method to synthesize photoluminescent copper nanocluster (Cu NC) aggregates from Cu2+ ions in 65% (v v-1) dimethylformamide aqueous solution containing penicillamine (PA) as a capping and reducing agent. As-prepared PA-Cu NC aggregates emit at 580 nm when excited at 326 nm, with a quantum yield of 2.0%. The photoluminescence of PA-Cu NC aggregates originate from ligand-to-metal charge transfer, which is supported by a long lifetime (126.5 ns) and a large Stokes shift (254 nm). As-prepared PA-Cu NC aggregates have different emission wavelengths with the same excitation wavelength in various organic-aqueous solutions. The PA-Cu NC aggregates are highly selective and sensitive to the detection of hydrogen sulfide (H2S), based on analyte-induced photoluminescence quenching through the formation of CuS nanoparticles. The probe allows the detection of H2S, with a linear range of 1-100 μM and a limit of detection (signal-to-noise ratio = 3) of 500 nM. The practicality of this probe has been validated through the analysis of hot spring water samples.

  9. Detection of hydrogen sulfide through photoluminescence quenching of penicillamine-copper nanocluster aggregates.

    PubMed

    Ma, Jia-Ying; Chen, Po-Cheng; Chang, Huan-Tsung

    2014-05-16

    We have developed a one-pot, inexpensive, simple and rapid method to synthesize photoluminescent copper nanocluster (Cu NC) aggregates from Cu(2+) ions in 65% (v v(-1)) dimethylformamide aqueous solution containing penicillamine (PA) as a capping and reducing agent. As-prepared PA-Cu NC aggregates emit at 580 nm when excited at 326 nm, with a quantum yield of 2.0%. The photoluminescence of PA-Cu NC aggregates originate from ligand-to-metal charge transfer, which is supported by a long lifetime (126.5 ns) and a large Stokes shift (254 nm). As-prepared PA-Cu NC aggregates have different emission wavelengths with the same excitation wavelength in various organic-aqueous solutions. The PA-Cu NC aggregates are highly selective and sensitive to the detection of hydrogen sulfide (H₂S), based on analyte-induced photoluminescence quenching through the formation of CuS nanoparticles. The probe allows the detection of H₂S, with a linear range of 1-100 μM and a limit of detection (signal-to-noise ratio = 3) of 500 nM. The practicality of this probe has been validated through the analysis of hot spring water samples.

  10. Blue photoluminescent carbon nanodots from limeade.

    PubMed

    Suvarnaphaet, Phitsini; Tiwary, Chandra Sekhar; Wetcharungsri, Jutaphet; Porntheeraphat, Supanit; Hoonsawat, Rassmidara; Ajayan, Pulickel Madhavapanicker; Tang, I-Ming; Asanithi, Piyapong

    2016-12-01

    Carbon-based photoluminescent nanodot has currently been one of the promising materials for various applications. The remaining challenges are the carbon sources and the simple synthetic processes that enhance the quantum yield, photostability and biocompatibility of the nanodots. In this work, the synthesis of blue photoluminescent carbon nanodots from limeade via a single-step hydrothermal carbonization process is presented. Lime carbon nanodot (L-CnD), whose the quantum yield exceeding 50% for the 490nm emission in gram-scale amounts, has the structure of graphene core functionalized with the oxygen functional groups. The micron-sized flake of the as-prepared L-CnD powder exhibits multicolor emission depending on an excitation wavelength. The L-CnDs are demonstrated for rapidly ferric-ion (Fe(3+)) detection in water compared to Fe(2+), Cu(2+), Co(2+), Zn(2+), Mn(2+) and Ni(2+) ions. The photoluminescence quenching of L-CnD solution under UV light is used to distinguish the Fe(3+) ions from others by naked eyes as low concentration as 100μM. Additionally, L-CnDs provide exceptional photostability and biocompatibility for imaging yeast cell morphology. Changes in morphology of living yeast cells, i.e. cell shape variation, and budding, can be observed in a minute-period until more than an hour without the photoluminescent intensity loss.

  11. Probing dark exciton diffusion using photovoltage

    PubMed Central

    Mullenbach, Tyler K.; Curtin, Ian J.; Zhang, Tao; Holmes, Russell J.

    2017-01-01

    The migration of weakly and non-luminescent (dark) excitons remains an understudied subset of exciton dynamics in molecular thin films. Inaccessible via photoluminescence, these states are often probed using photocurrent methods that require efficient charge collection. Here we probe exciton harvesting in both luminescent and dark materials using a photovoltage-based technique. Transient photovoltage permits a real-time measurement of the number of charges in an organic photovoltaic cell, while avoiding non-geminate recombination losses. The extracted exciton diffusion lengths are found to be similar to those determined using photocurrent. For the luminescent material boron subphthalocyanine chloride, the photovoltage determined diffusion length is less than that extracted from photoluminescence. This indicates that while photovoltage circumvents non-geminate losses, geminate recombination at the donor–acceptor interface remains the primary recombination pathway. Photovoltage thus offers a general approach for extracting a device-relevant diffusion length, while also providing insight in to the dominant carrier recombination pathways. PMID:28128206

  12. Probing dark exciton diffusion using photovoltage

    NASA Astrophysics Data System (ADS)

    Mullenbach, Tyler K.; Curtin, Ian J.; Zhang, Tao; Holmes, Russell J.

    2017-01-01

    The migration of weakly and non-luminescent (dark) excitons remains an understudied subset of exciton dynamics in molecular thin films. Inaccessible via photoluminescence, these states are often probed using photocurrent methods that require efficient charge collection. Here we probe exciton harvesting in both luminescent and dark materials using a photovoltage-based technique. Transient photovoltage permits a real-time measurement of the number of charges in an organic photovoltaic cell, while avoiding non-geminate recombination losses. The extracted exciton diffusion lengths are found to be similar to those determined using photocurrent. For the luminescent material boron subphthalocyanine chloride, the photovoltage determined diffusion length is less than that extracted from photoluminescence. This indicates that while photovoltage circumvents non-geminate losses, geminate recombination at the donor-acceptor interface remains the primary recombination pathway. Photovoltage thus offers a general approach for extracting a device-relevant diffusion length, while also providing insight in to the dominant carrier recombination pathways.

  13. A new dual-channel optical signal probe for Cu2+ detection based on morin and boric acid.

    PubMed

    Wang, Peng; Yuan, Bin Fang; Li, Nian Bing; Luo, Hong Qun

    2014-01-01

    In this work we utilized the common analytical reagent morin to develop a new a dual-channel, cost-effective, and sensitive method for determination of Cu(2+). It is found that morin is only weakly fluorescent by itself, but forms highly fluorescent complexes with boric acid. Moreover, the fluorescence of complexes of morin with boric acid is quenched linearly by Cu(2+) in a certain concentration range. Under optimum conditions, the fluorescence quenching efficiency was linearly proportional to the concentration of cupric ions in the range of 0.5-25 μM with high sensitivity, and the detection limit for Cu(2+) was 0.38 μM. The linear range was 1-25 μM determined by spectrophotometry, and the detection limit for cupric ions was 0.8 μM. Furthermore, the mechanism of sensitive fluorescence quenching response of morin to Cu(2+) is discussed.

  14. Probing the "additive effect" in the proline and proline hydroxamic acid catalyzed asymmetric addition of nitroalkanes to cyclic enones.

    PubMed

    Hanessian, Stephen; Govindan, Subramaniyan; Warrier, Jayakumar S

    2005-11-01

    The effect of chirality and steric bulk of 2,5-disubstituted piperazines as additives in the conjugate addition of 2-nitropropane to cyclohexenone, catalyzed by l-proline, was investigated. Neither chirality nor steric bulk affects the enantioselectivity of addition, which gives 86-93% ee in the presence of achiral and chiral nonracemic 2,5-disubstituted piperazines. Proline hydroxamic acid is shown for the first time to be an effective organocatalyst in the same Michael reaction.

  15. Accurate radiation temperature and chemical potential from quantitative photoluminescence analysis of hot carrier populations

    NASA Astrophysics Data System (ADS)

    Gibelli, François; Lombez, Laurent; Guillemoles, Jean-François

    2017-02-01

    In order to characterize hot carrier populations in semiconductors, photoluminescence measurement is a convenient tool, enabling us to probe the carrier thermodynamical properties in a contactless way. However, the analysis of the photoluminescence spectra is based on some assumptions which will be discussed in this work. We especially emphasize the importance of the variation of the material absorptivity that should be considered to access accurate thermodynamical properties of the carriers, especially by varying the excitation power. The proposed method enables us to obtain more accurate results of thermodynamical properties by taking into account a rigorous physical description and finds direct application in investigating hot carrier solar cells, which are an adequate concept for achieving high conversion efficiencies with a relatively simple device architecture.

  16. Accurate radiation temperature and chemical potential from quantitative photoluminescence analysis of hot carrier populations.

    PubMed

    Gibelli, François; Lombez, Laurent; Guillemoles, Jean-François

    2017-02-15

    In order to characterize hot carrier populations in semiconductors, photoluminescence measurement is a convenient tool, enabling us to probe the carrier thermodynamical properties in a contactless way. However, the analysis of the photoluminescence spectra is based on some assumptions which will be discussed in this work. We especially emphasize the importance of the variation of the material absorptivity that should be considered to access accurate thermodynamical properties of the carriers, especially by varying the excitation power. The proposed method enables us to obtain more accurate results of thermodynamical properties by taking into account a rigorous physical description and finds direct application in investigating hot carrier solar cells, which are an adequate concept for achieving high conversion efficiencies with a relatively simple device architecture.

  17. Probing the chemical mechanism and critical regulatory amino acid residues of Drosophila melanogaster arylalkylamine N-acyltransferase like 2.

    PubMed

    Dempsey, Daniel R; Carpenter, Anne-Marie; Ospina, Santiago Rodriguez; Merkler, David J

    2015-11-01

    Arylalkylamine N-acyltransferase like 2 (AANATL2) catalyzes the formation of N-acylarylalkylamides from the corresponding acyl-CoA and arylalkylamine. The N-acylation of biogenic amines in Drosophila melanogaster is a critical step for the inactivation of neurotransmitters, cuticle sclerotization, and melatonin biosynthesis. In addition, D. melanogaster has been used as a model system to evaluate the biosynthesis of fatty acid amides: a family of potent cell signaling lipids. We have previously showed that AANATL2 catalyzes the formation of N-acylarylakylamides, including long-chain N-acylserotonins and N-acyldopamines. Herein, we define the kinetic mechanism for AANATL2 as an ordered sequential mechanism with acetyl-CoA binding first followed by tyramine to generate the ternary complex prior to catalysis. Bell shaped kcat,app - acetyl-CoA and (kcat/Km)app - acetyl-CoA pH-rate profiles identified two apparent pKa,app values of ∼7.4 and ∼8.9 that are critical to catalysis, suggesting the AANATL2-catalyzed formation of N-acetyltyramine occurs through an acid/base chemical mechanism. Site-directed mutagenesis of a conserved glutamate that corresponds to the catalytic base for other D. melanogaster AANATL enzymes did not produce a substantial depression in the kcat,app value nor did it abolish the pKa,app value attributed to the general base in catalysis (pKa ∼7.4). These data suggest that AANATL2 catalyzes the formation of N-acylarylalkylamides using either different catalytic residues or a different chemical mechanism relative to other D. melanogaster AANATL enzymes. In addition, we constructed other site-directed mutants of AANATL2 to help define the role of targeted amino acids in substrate binding and/or enzyme catalysis.

  18. Folic acid-targeted magnetic Tb-doped CeF3 fluorescent nanoparticles as bimodal probes for cellular fluorescence and magnetic resonance imaging.

    PubMed

    Ma, Zhi-Ya; Liu, Yu-Ping; Bai, Ling-Yu; An, Jie; Zhang, Lin; Xuan, Yang; Zhang, Xiao-Shuai; Zhao, Yuan-Di

    2015-10-07

    Magnetic fluorescent nanoparticles (NPs) have great potential applications for diagnostics, imaging and therapy. We developed a facile polyol method to synthesize multifunctional Fe3O4@CeF3:Tb@CeF3 NPs with small size (<20 nm), high water solubility and good biocompatibility. The NPs were modified by ligand exchange reactions with citric acid (CA) to obtain carboxyl-functionalized NPs (Fe3O4@CeF3:Tb@CeF3-COOH). Folic acid (FA) as an affinity ligand was then covalently conjugated onto NPs to yield Fe3O4@CeF3:Tb@CeF3-FA NPs. They were then applied as multimodal imaging agents for simultaneous in vitro targeted fluorescence imaging and magnetic resonance imaging (MRI) of HeLa cells with overexpressed folate receptors (FR). The results indicated that these NPs had strong luminescence and enhanced T2-weighted MR contrast and would be promising candidates as multimodal probes for both fluorescence and MRI imaging.

  19. Probing of the combined effect of bisquaternary ammonium antimicrobial agents and acetylsalicylic acid on model phospholipid membranes: differential scanning calorimetry and mass spectrometry studies.

    PubMed

    Kasian, N A; Pashynska, V A; Vashchenko, O V; Krasnikova, A O; Gömöry, A; Kosevich, M V; Lisetski, L N

    2014-12-01

    A model molecular biosystem of hydrated dipalmitoylphosphatidylcholine (DPPC) bilayers that mimics cell biomembranes is used to probe combined membranotropic effects of drugs by instrumental techniques of molecular biophysics. Differential scanning calorimetry reveals that doping of the DPPC model membrane with individual bisquaternary ammonium compounds (BQAC) decamethoxinum, ethonium, thionium and acetylsalicylic acid (ASA) leads to lowering of the membrane melting temperature (Tm) pointing to membrane fluidization. Combined application of the basic BQAC and acidic ASA causes an opposite effect on Tm (increase), corresponding to the membrane densification. Thus, modulation of the membranotropic effects upon combined use of the drugs studied can be revealed at the level of model membranes. Formation of noncovalent supramolecular complexes of the individual BQACs and ASA with DPPC molecules, which may be involved in the mechanism of the drug-membrane interaction at the molecular level, is demonstrated by electrospray ionization (ESI) mass spectrometry. In the ternary (DPPC + ASA + BQAC) model systems, the stable complexes of the BQAC dication with the ASA anion, which may be responsible for modulation of the membranotropic effects of the drugs, were recorded by ESI mass spectrometry. The proposed approach can be further developed for preliminary evaluation of the combined effects of the drugs at the level of model lipid membranes prior to tests on living organisms.

  20. Probing the Active Site of MIO-dependent Aminomutases, Key Catalysts in the Biosynthesis of amino Acids Incorporated in Secondary Metabolites

    SciTech Connect

    Cooke, H.; Bruner, S

    2010-01-01

    The tyrosine aminomutase SgTAM produces (S)-{beta}-tyrosine from L-tyrosine in the biosynthesis of the enediyne antitumor antibiotic C-1027. This conversion is promoted by the methylideneimidazole-5-one (MIO) prosthetic group. MIO was first identified in the homologous family of ammonia lyases, which deaminate aromatic amino acids to form {alpha},{beta}-unsaturated carboxylates. Studies of substrate specificity have been described for lyases but there have been limited reports in altering the substrate specificity of aminomutases. Furthermore, it remains unclear as to what structural properties are responsible for catalyzing the presumed readdition of the amino group into the {alpha},{beta}-unsaturated intermediates to form {beta}-amino acids. Attempts to elucidate specificity and mechanistic determinants of SgTAM have also proved to be difficult as it is recalcitrant to perturbations to the active site via mutagenesis. An X-ray cocrystal structure of the SgTAM mutant of the catalytic base with L-tyrosine verified important substrate binding residues as well as the enzymatic base. Further mutagenesis revealed that removal of these crucial interactions renders the enzyme inactive. Proposed structural determinants for mutase activity probed via mutagenesis, time-point assays and X-ray crystallography revealed a complicated role for these residues in maintaining key quaternary structure properties that aid in catalysis.

  1. Investigation of Humidity Dependent Surface Morphology and Proton Conduction in Multi-Acid Side Chain Membranes by Conductive Probe Atomic Force Microscopy.

    PubMed

    Economou, Nicholas J; Barnes, Austin M; Wheat, Andrew J; Schaberg, Mark S; Hamrock, Steven J; Buratto, Steven K

    2015-11-05

    In this report, we employ phase-contrast tapping mode and conductive probe atomic force microscopy (cp-AFM) as tools to investigate the nanoscale morphology and proton conductance of a 3M perfluoro-imide acid (PFIA) membrane (625 EW) over a large range of relative humidity (3-95% RH). As a point of comparison, we also investigate 3M perfluorosulfonic acid (PFSA) (825 EW) and Nafion 212. With AFM, we assess the membrane's water retention and mechanical stability at low RH and high RH, respectively. Cp-AFM allows us to spatially resolve the hydrophilic and electrochemically active domains under a similar set of conditions and observe directly the ties between membrane morphology and proton conductance. From our data, we are able to correlate the improved water retention indicated by the size of the hydrophilic domains with the proton conductance in the PFIA membrane at elevated temperature and compare the result with that observed for the PFSA and Nafion. At high RH conditions, we see evidence of a nearly continuous hydrophilic phase, which indicates a high degree of swelling.

  2. Probing Nucleic Acid Interactions and Pre-mRNA Splicing by Förster Resonance Energy Transfer (FRET) Microscopy

    PubMed Central

    Šimková, Eva; Staněk, David

    2012-01-01

    Förster resonance energy transfer (FRET) microscopy is a powerful technique routinely used to monitor interactions between biomolecules. Here, we focus on the techniques that are used for investigating the structure and interactions of nucleic acids (NAs). We present a brief overview of the most commonly used FRET microscopy techniques, their advantages and drawbacks. We list experimental approaches recently used for either in vitro or in vivo studies. Next, we summarize how FRET contributed to the understanding of pre-mRNA splicing and spliceosome assembly. PMID:23203103

  3. Amorphous/nanocrystalline silicon biosensor for the specific identification of unamplified nucleic acid sequences using gold nanoparticle probes

    NASA Astrophysics Data System (ADS)

    Martins, Rodrigo; Baptista, Pedro; Raniero, Leandro; Doria, Gonçalo; Silva, Leonardo; Franco, Ricardo; Fortunato, Elvira

    2007-01-01

    Amorphous/nanocrystalline silicon pi 'ii'n devices fabricated on micromachined glass substrates are integrated with oligonucleotide-derivatized gold nanoparticles for a colorimetric detection method. The method enables the specific detection and quantification of unamplified nucleic acid sequences (DNA and RNA) without the need to functionalize the glass surface, allowing for resolution of single nucleotide differences between DNA and RNA sequences—single nucleotide polymorphism and mutation detection. The detector's substrate is glass and the sample is directly applied on the back side of the biosensor, ensuring a direct optical coupling of the assays with a concomitant maximum photon capture and the possibility to reuse the sensor.

  4. Characterisation of embroidered 3D electrodes by use of anthraquinone-1,5-disulfonic acid as probe system

    NASA Astrophysics Data System (ADS)

    Aguiló-Aguayo, Noemí; Bechtold, Thomas

    2014-05-01

    New electrode designs are required for electrochemical applications such as batteries or fuel cells. Embroidered 3D Cu porous electrodes with a geometric surface of 100 cm2 are presented and characterised by means of the anthraquinone-1,5-disfulfonic acid (AQDS2-) redox system in alkaline solution. The electrochemical behaviour of the 3D electrode is established by the comparison of cyclic voltammetry responses using a micro cell and a 100 cm2 plane Cu-plate electrode. Dependencies of the peak currents and peak-to-peak potential separation on scan rate and AQDS2- concentration are studied. The AQDS2- characterisation is also performed by means of spectroelectrochemical experiments.

  5. A novel magnetic field probing technique for determining state of health of sealed lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Khare, Neeta; Singh, Pritpal; Vassiliou, John K.

    2012-11-01

    State of Health (SOH) is a critical index for a Sealed Lead-Acid (SLA) battery diagnostic which provides the information about battery replacement and aging effects. SOH is a complex function of chemical parameters of a battery such as stratification in electrolyte, electrode structure (sulfation and hard sulfation) in addition to electrical parameters of a battery. This paper describes a method of online determination of stratification, electrode structure, electrode polarization and current profile within the battery under the influence of a magnetic field. An AC magnetic field is used as a noninvasive tool during battery cycles. An induced emf in a secondary coil (SCV) is used as a measure of change in the magnetic field. The H+ proton density varies with change in sulfuric acid (electrolyte) concentration during battery cycles. The magnetic flux lines are affected by the density of H+ protons whose magnetic dipole moments try to align along the magnetic flux lines. The stratification is seen by a 12% decrease in magnetic flux linking from the top to the bottom of the electrolyte in a battery. Additional experimental results demonstrate the variation in magnetic flux linking which correlates with current profile across the electrode and electrode structure.

  6. Molecular dynamics approach to probe the allosteric inhibition of PTP1B by chlorogenic and cichoric acid.

    PubMed

    Baskaran, Sarath Kumar; Goswami, Nabajyoti; Selvaraj, Sudhagar; Muthusamy, Velusamy Shanmuganathan; Lakshmi, Baddireddi Subhadra

    2012-08-27

    Protein tyrosine phosphatase 1B (PTP1B), a major negative regulator of the insulin and leptin signaling pathway, is a potential target for therapeutic intervention against diabetes and obesity. The recent discovery of an allosteric site in PTP1B has created an alternate strategy in the development of PTP1B targeted therapy. The current study investigates the molecular interactions between the allosteric site of PTP1B with two caffeoyl derivatives, chlorogenic acid (CGA) and cichoric acid (CHA), using computational strategies. Molecular docking analysis with CGA and CHA at the allosteric site of PTP1B were performed and the resulting protein-ligand complexes used for molecular dynamics simulation studies for a time scale of 10 ns. Results show stable binding of CGA and CHA at the allosteric site of PTP1B. The flexibility of the WPD loop was observed to be constrained by CGA and CHA in the open (inactive), providing molecular mechanism of allosteric inhibition. The allosteric inhibition of CGA and CHA of PTP1B was shown to be favorable due to no restriction by the α-7 helix in the binding of CGA and CHA at the allosteric binding site. In conclusion, our results exhibit an inhibitory pattern of CGA and CHA against PTP1B through potent binding at the allosteric site.

  7. Using rumen probes to examine effects of conjugated linoleic acids and dietary concentrate proportion on rumen pH and rumen temperature of periparturient dairy cows.

    PubMed

    Petzold, M; Meyer, U; Spilke, J; Dänicke, S

    2014-08-01

    The study aimed to examine the influence of supplemented conjugated linoleic acids (CLA) to periparturient cows receiving different concentrate proportions antepartum on rumen pH (RpH) and rumen temperature (RT). Twenty pregnant German Holstein cows were equipped with rumen probes for continuous RpH and RT measurement in a frequency of 15 min to investigate effects of dietary concentrate and CLA around parturition and the impact of parturition itself on RpH and RT. Cows had ad libitum access to partial mixed rations, 3 weeks prior to calving until day 7 post-partum. Antepartum, cows received 100 g/day control fat (CON) or CLA supplement, either in low (20%; CON-20, CLA-20) or high concentrate diet (60%; CON-60, CLA-60). Post-partum, concentrate proportion was adjusted to 50% while fat supplementation continued. Compared with adapted feeding, high concentrate proportions antepartum tended to increase DMI and reduced RpH. Groups CON-60 and CLA-60 spent more than 4 h per day below RpH 5.6 during late pregnancy, indicating the presence of subacute rumen acidosis (SARA). The RT remained unaffected antepartum. Before calving, cows spent less time below RpH 5.6 and SARA could be detected in each group post-partum. Mean RpH increased slightly antepartum, whereas few hours before parturition a sharp decrease in RpH could be observed, accompanied with increased RT. Overall, it seems that CLA supplementation influences RpH and RT. Bearing in mind that rumen parameters fluctuate during day and herd level must be known, rumen probes for continuous RpH and RT measurement could be a useful management tool for animal health surveillance and may also help to predict parturition.

  8. Mn-doped ZnS quantum dot imbedded two-fragment imprinting silica for enhanced room temperature phosphorescence probing of domoic acid.

    PubMed

    Dan, Li; Wang, He-Fang

    2013-05-21

    A novel strategy was presented to construct the enhanced molecularly imprinted polymer (MIP)-based room temperature phosphorescence (RTP) probe by combining the RTP of Mn-doped ZnS quantum dots (Mn-ZnS QDs) and two-fragment imprinting. Two fragments or structurally similar parts of the target analytes were used as the dummy templates. Polyethyleneimine capped Mn-ZnS (PEI-Mn-ZnS) QDs, offering the binding sites to interact with the carboxyl groups of templates, were imbedded into MIPs by the hydrolysis of tetraethoxysilane. The rebinding of the target analytes to their fragments' cavities (recognition sites) modulated the selective aggregation of Mn-ZnS QDs in QDs-MIPs and resulted in the RTP enhancement. This new method was suitable for the selective enhanced RTP detection of nonphosphorescent analytes without any derivatization and inducers. The proposed methodology was applied to construct the high selective enhanced MIP-based RTP probe for domoic acid (DA) detection. The RTP enhancement of two-fragment imprinting silica was about 2 times of one-fragment imprinting silica and 4 times of the nonimprinting silica. The two-fragment imprinting silica exhibited the linear RTP enhancement to DA in the range of 0.25-3.5 μM in buffer and 0.25-1.5 μM in shellfish sample. The precision for 11 replicate detections of 1.25 μM DA was 0.65% (RSD), and the limit of detection was 67 nM in buffer and 2.0 μg g(-1) wet weight (w/w) in shellfish sample.

  9. Germinal Center Marker GL7 Probes Activation-Dependent Repression of N-Glycolylneuraminic Acid, a Sialic Acid Species Involved in the Negative Modulation of B-Cell Activation▿ †

    PubMed Central

    Naito, Yuko; Takematsu, Hiromu; Koyama, Susumu; Miyake, Shizu; Yamamoto, Harumi; Fujinawa, Reiko; Sugai, Manabu; Okuno, Yasushi; Tsujimoto, Gozoh; Yamaji, Toshiyuki; Hashimoto, Yasuhiro; Itohara, Shigeyoshi; Kawasaki, Toshisuke; Suzuki, Akemi; Kozutsumi, Yasunori

    2007-01-01

    Sialic acid (Sia) is a family of acidic nine-carbon sugars that occupies the nonreducing terminus of glycan chains. Diversity of Sia is achieved by variation in the linkage to the underlying sugar and modification of the Sia molecule. Here we identified Sia-dependent epitope specificity for GL7, a rat monoclonal antibody, to probe germinal centers upon T cell-dependent immunity. GL7 recognizes sialylated glycan(s), the α2,6-linked N-acetylneuraminic acid (Neu5Ac) on a lactosamine glycan chain(s), in both Sia modification- and Sia linkage-dependent manners. In mouse germinal center B cells, the expression of the GL7 epitope was upregulated due to the in situ repression of CMP-Neu5Ac hydroxylase (Cmah), the enzyme responsible for Sia modification of Neu5Ac to Neu5Gc. Such Cmah repression caused activation-dependent dynamic reduction of CD22 ligand expression without losing α2,6-linked sialylation in germinal centers. The in vivo function of Cmah was analyzed using gene-disrupted mice. Phenotypic analyses showed that Neu5Gc glycan functions as a negative regulator for B-cell activation in assays of T-cell-independent immunization response and splenic B-cell proliferation. Thus, Neu5Gc is required for optimal negative regulation, and the reaction is specifically suppressed in activated B cells, i.e., germinal center B cells. PMID:17296732

  10. Effect of chemical heterogeneity on photoluminescence of graphite oxide treated with S-/N-containing modifiers

    NASA Astrophysics Data System (ADS)

    Ebrahim, Amani M.; Rodríguez-Castellón, Enrique; Montenegro, José María; Bandosz, Teresa J.

    2015-03-01

    Graphite oxide (GO) obtained using Hummers method was modified by hydrothermal treatment either with sulfanilic acid or polystyrene (3-ammonium) sulfonate at 100 °C or 85 °C, respectively. Both modifiers contain sulfur in the oxidized forms and nitrogen in the reduced forms. The materials were characterized using FTIR, XPS, thermal analysis, potentiometric titration and SEM. Their photoluminescent properties and their alteration with an addition of Ag+ were also measured. As a result of these modifications nitrogen was introduced to the graphene layers as amines, imides, amides, and sulfur as sulfones and sulfonic acids. Moreover, the presence of polyaniline was detected. This significantly affected the polarity, acid-base character, and conductivity of the materials. Apparently carboxylic groups of GO were involved in the surface reactions. The modified GOs lost their layered structure and the modifications resulted in the high degree of structural and chemical heterogeneity. Photoluminescence in visible light was recorded and linked to the presence of heteroatoms. For the polystyrene (3-ammonium) sulfonate modified sample addition of Ag+ quenched the photoluminescence at low wavelength showing sensitivity as a possible optical detector. No apparent effect was found for the sulfanilic acid modified sample.

  11. Photoluminescence of Mn+ doped GaAs

    NASA Astrophysics Data System (ADS)

    Zhou, Huiying; Qu, Shengchun; Liao, Shuzhi; Zhang, Fasheng; Liu, Junpeng; Wang, Zhanguo

    2010-10-01

    Photoluminescence is one of the most useful techniques to obtain information about optoelectronic properties and defect structures of materials. In this work, the room-temperature and low temperature photoluminescence of Mn-doped GaAs were investigated, respectively. Mn-doped GaAs structure materials were prepared by Mn+ ion implantation at room temperature into GaAs. The implanted samples were subsequently annealed at various temperatures under N2 atmosphere to recrystallize the samples and remove implant damage. A strong peak was found for the sample annealed at 950 °C for 5 s. Transitions near 0.989 eV (1254 nm), 1.155 eV (1074 nm) and 1.329 eV (933 nm) were identified and formation of these emissions was analyzed for all prepared samples. This structure material could have myriad applications, including information storage, magnet-optical properties and energy level engineering.

  12. Ferritin protein encapsulated photoluminescent rare earth nanoparticle

    NASA Astrophysics Data System (ADS)

    Harada, T.; Yoshimura, H.

    2013-07-01

    Rare earth (yttrium (Y), europium (Eu), and terbium (Tb)) nanoparticles and Eu and Tb doped Y nanoparticles are synthesized in an apoferritin cavity. They exhibit a narrow size distribution and a high stability in an aqueous solution at pH 8.5. Eu and Eu doped Y (Y:Eu) nanoparticles exhibit red photoluminescence (emission peaks: 590 and 614 nm), while Tb and Tb doped Y (Y:Tb) nanoparticles exhibit green photoluminescence (emission peaks: 488, 544, 582, and 618 nm). High-resolution electron microscopy observations reveal that about 5% of the nanoparticles have a lattice structure, while the remaining nanoparticles are amorphous. Electron diffraction of the Y nanoparticles gives lattice spacings corresponding to the cubic structure of yttrium oxide (Y2O3). The most optimal dopant content for luminescence of Y:Eu and Y:Tb nanoparticles in apoferritin cavity are about 60% and 40%, respectively.

  13. Magneto photoluminescence measurements of tungsten disulphide monolayers

    NASA Astrophysics Data System (ADS)

    Kuhnert, Jan; Rahimi-Iman, Arash; Heimbrodt, Wolfram

    2017-03-01

    Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer thickness the inversion symmetry of the crystal is broken and spin and valley are coupled to each other. The degeneracy between the two equivalent valleys, K and K‧, respectively, can be lifted by applying an external magnetic field. Here, we present photoluminescence measurements of CVD-grown tungsten disulphide (WS2) monolayers at temperatures of 2 K. By applying magnetic fields up to 7 T in Faraday geometry, a splitting of the photoluminescence peaks can be observed. The magnetic field dependence of the A-exciton, the trion and three bound exciton states is discussed and the corresponding g-factors are determined.

  14. A Comprehensive Spectroscopic and Computational Investigation to Probe the Interaction of Antineoplastic Drug Nordihydroguaiaretic Acid with Serum Albumins.

    PubMed

    Nusrat, Saima; Siddiqi, Mohammad Khursheed; Zaman, Masihuz; Zaidi, Nida; Ajmal, Mohammad Rehan; Alam, Parvez; Qadeer, Atiyatul; Abdelhameed, Ali Saber; Khan, Rizwan Hasan

    2016-01-01

    Exogenous drugs that are used as antidote against chemotheray, inflammation or viral infection, gets absorbed and interacts reversibly to the major serum transport protein i.e. albumins, upon entering the circulatory system. To have a structural guideline in the rational drug designing and in the synthesis of drugs with greater efficacy, the binding mechanism of an antineoplastic and anti-inflammatory drug Nordihydroguaiaretic acid (NDGA) with human and bovine serum albumins (HSA & BSA) were examined by spectroscopic and computational methods. NDGA binds to site II of HSA with binding constant (Kb) ~105 M-1 and free energy (ΔG) ~ -7.5 kcal.mol-1. It also binds at site II of BSA but with lesser binding affinity (Kb) ~105 M-1 and ΔG ~ -6.5 kcal.mol-1. The negative value of ΔG, ΔH and ΔS for both the albumins at three different temperatures confirmed that the complex formation process between albumins and NDGA is spontaneous and exothermic. Furthermore, hydrogen bonds and hydrophobic interactions are the main forces involved in complex formation of NDGA with both the albumins as evaluated from fluorescence and molecular docking results. Binding of NDGA to both the albumins alter the conformation and causes minor change in the secondary structure of proteins as indicated by the CD spectra.

  15. Preparation of Au Nanoclusters-Modified Polylactic Acid Fiber with Bright Red Fluorescence and its Use as Sensing Probe.

    PubMed

    Zhu, Wenli; Li, Huili; Wan, Ajun; Liu, Lanbo

    2017-01-01

    In present work, the Au nanoclusters-modified polylactic acid fiber (PLA-Au NCs) with bright red fluorescence were fabricated by the encapsulation of Au nanoclusters (Au NCs) in the PLA fiber treated with H2O2. The Au25 nanoclusters stabilized by bovine serum albumin (BSA-Au NCs) were prepared via an improved "green" synthetic routine. With pretreatment of the PLA fiber in H2O2 concentration of 12 and 18 %, the as-prepared PLA-Au NCs exhibited brighter red emission with a strong peak centered at ~640 nm than BSA-Au NCs. The fluorescence can be quenched by nitric oxide (NO). A good linear relationship between the relative fluorescence quenching intensity of the as-prepared PLA-Au NCs and the concentration of NO can be obtained in the range of 0.0732 to 0.7320 mM, and the detection limit was 0.0070 mM.

  16. A Comprehensive Spectroscopic and Computational Investigation to Probe the Interaction of Antineoplastic Drug Nordihydroguaiaretic Acid with Serum Albumins

    PubMed Central

    Nusrat, Saima; Siddiqi, Mohammad Khursheed; Zaman, Masihuz; Zaidi, Nida; Ajmal, Mohammad Rehan; Alam, Parvez; Qadeer, Atiyatul; Abdelhameed, Ali Saber

    2016-01-01

    Exogenous drugs that are used as antidote against chemotheray, inflammation or viral infection, gets absorbed and interacts reversibly to the major serum transport protein i.e. albumins, upon entering the circulatory system. To have a structural guideline in the rational drug designing and in the synthesis of drugs with greater efficacy, the binding mechanism of an antineoplastic and anti-inflammatory drug Nordihydroguaiaretic acid (NDGA) with human and bovine serum albumins (HSA & BSA) were examined by spectroscopic and computational methods. NDGA binds to site II of HSA with binding constant (Kb) ~105 M-1 and free energy (ΔG) ~ -7.5 kcal.mol-1. It also binds at site II of BSA but with lesser binding affinity (Kb) ~105 M-1 and ΔG ~ -6.5 kcal.mol-1. The negative value of ΔG, ΔH and ΔS for both the albumins at three different temperatures confirmed that the complex formation process between albumins and NDGA is spontaneous and exothermic. Furthermore, hydrogen bonds and hydrophobic interactions are the main forces involved in complex formation of NDGA with both the albumins as evaluated from fluorescence and molecular docking results. Binding of NDGA to both the albumins alter the conformation and causes minor change in the secondary structure of proteins as indicated by the CD spectra. PMID:27391941

  17. A novel turn-on fluorescent strategy for sensing ascorbic acid using graphene quantum dots as fluorescent probe.

    PubMed

    Liu, Hua; Na, Weidan; Liu, Ziping; Chen, Xueqian; Su, Xingguang

    2017-06-15

    In this paper, a facile and rapid fluorescence turn-on assay for fluorescent detection of ascorbic acid (AA) was developed by using the orange emission graphene quantum dots (GQDs). In the presence of horse radish peroxidase (HRP) and hydrogen peroxide (H2O2), catechol can be oxidized by hydroxyl radicals and converted to o-benzoquinone, which can significantly quench the fluorescence of GQDs. However, when AA present in the system, it can consume part of H2O2 and hydroxyl radicals to inhibit the generation of o-benzoquinone, resulting in fluorescence recovery. Under the optimized experimental conditions, the fluorescence intensity was linearly correlated with the concentration of H2O2 in the range of 3.33-500µM with a detection limit of 1.2µM. The linear detection for AA was in the range from 1.11 to 300µM with a detection limit of 0.32µM. The proposed method was applied to the determination of AA in human serum samples with satisfactory results.

  18. Sulphonic acid derivatives as probes of pore properties of volume-regulated anion channels in endothelial cells.

    PubMed

    Droogmans, G; Maertens, C; Prenen, J; Nilius, B

    1999-09-01

    1. We have used the whole-cell patch-clamp technique to study the effects of 4-sulphonic-calixarenes and some other poly-sulphonic acid agents, such as suramin and basilen blue, on volume-regulated anion channel (VRAC) currents in cultured endothelial cells (CPAE cells). 2. The 4-sulphonic-calixarenes induced a fast inhibition at positive potentials but were ineffective at negative potentials. At small positive potentials, 4-sulphonic-calix[4]arene was a more effective inhibitor than 4-sulphonic-calix[6]arene and -calix[8]arene, which became more effective at more positive potentials. 3. Also suramin and basilen blue induced a voltage dependent current inhibition, reaching a maximum around +40 mV and declining at more positive potentials. 4. The voltage dependence of inhibition was modelled by assuming that these negatively charged molecules bind to a site inside VRAC that senses a fraction delta of the applied electrical field, ranging beween 0.16 to 0.32. 4-Sulphonic-calix[4]arene, suramin and basilen blue bind and occlude VRAC at moderate potentials, but permeate the channel at more positive potentials. 4-Sulphonic-calix[6]arene and -calix[8]arene however do not permeate the channel. From the structural information of the calixarenes, we estimate a lower and upper limit of 11*12 and 17*12 A2 respectively for the cross-sectional area of the pore.

  19. Effect of alloying on the photoluminescence of the CuInS2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Kim, Young-Kuk; Choi, Chul-Jin

    2011-10-01

    We have developed a novel route to highly luminescent Cd-free core-shell nanocrystals. By simply refluxing assynthesized CuInS2 nanocrystals with zinc acetate and palmitic acid, highly luminescent CuInS2/ZnS nanocrystals were synthesized. We modified the photoluminescence of the grown nanocrystal by alloying foreign atoms. Nanocrystals with alloyed cores were synthesized by adding selenium and nanocrystals with alloyed shell layers were synthesized by refluxing the as-synthesized CuInS2 nanocrystals with mixture of cadmium acetate, zinc acetate and palmitic acid. It was found that the emission wavelength of the nanocrystals was shifted to longer wavelength side by alloying. The photoluminescence spectra showed clear red-shift without significant minimization of emission intensity. A Detailed study on the emission process of nanocrystals implies that the formation of shell layers with small lattice mismatch minimized mismatch strain generated from the shell layers in contrast to core alloyed nanocrystals.

  20. Molecularly imprinted ultrathin graphitic carbon nitride nanosheets-Based electrochemiluminescence sensing probe for sensitive detection of perfluorooctanoic acid.

    PubMed

    Chen, Sihua; Li, Aimin; Zhang, Lizhi; Gong, Jingming

    2015-10-08

    Driven by the urgent demand for the determination of low level perfluorooctanoic acid (PFOA) present in environment, a novel electrochemiluminescence (ECL) sensor has been first developed for the detection of PFOA using the molecularly imprinted polypyrrole modified two-dimensional ultrathin g-C3N4 (utg-C3N4) nanosheets as a cathodic ECL emitter with S2O8(2-) as coreactant. The prepared molecularly imprinted polymer (MIP) functionalized utg-C3N4 nanosheets (MIP@utg-C3N4) exhibit a stable and significantly amplified ECL signal. It is found that the targets of PFOA could be efficiently oxidized by the electro-generated strong oxidants of SO4(-) (from the reduction of coreactant S2O8(2-)), thus leading to a low yield of the excited utg-C3N4 (g-C3N4*) and finally a decrease in ECL signal. Based on this, a highly sensitive and selective MIP@utg-C3N4-based signal-off ECL sensor is developed for sensing PFOA. Such a newly designed ECL sensor exhibits highly linear over the PFOA concentration in two ranges, from 0.02 to 40.0 ng mL(-1) and 50.0-400.0 ng mL(-1). The detection limit (S/N = 3) is estimated to be 0.01 ng mL(-1) (i.e. 0.01 ppb), comparable to the results obtained by using well-established liquid chromatography-tandem mass spectrometry (LC-MS/MS). Toward practical applications, this low-cost and sensitive assay was successfully applied to measure PFOA in real water samples, showing fine applicability for the detection of PFOA in real samples.

  1. Probing the role of lysine 16 in ras p[sup 21] protein with unnatural amino acids

    SciTech Connect

    Chung, H.H.; Benson, D.R.; Schultz, P.G. )

    1993-07-14

    Mamalian proteins encoded by the ras gene are thought to function as regulators of various signal transduction processes involved in cell growth and differentiation. The chemical basis for the regulation is cycling of the protein between the inactive guanosine diphosphate (GDP)-bound state and the active guanosine triphophate (GTP)-bound state. Loop 1 of ras contains the GXXXXGK(S/T) motif (residues 10-17), which is found in all ras-related proteins, G proteins, and other nucleotide-binding proteins. Structural and biochemical studies have suggested that Lys 16 of loop 1 is critical for substrate binding and catalysis. The [epsilon]-amino group is involved in ion pair interactions with the [Beta]-and [gamma]-phosphates of GTP and forms hydrogen bonds with the main-chain oxygens of Gly 10 and Ala 11. In order to better understand the role of the key residue in ras function, we have replaced Lys 16 with a number of unnatural amino acid analogues, including (aminoethyl)cysteine, (hydroxyethyl)cysteine, (aminoethyl)homocysteine, and ornithine. We were surprised to find that the [open quotes]unnatural[close quotes] mutant ras proteins retained high levels of GAP-stimulated GTPase activity and GTP dissociation rates comparable to that of wild-type ras. These results may indicate that, in the GAP-activated form, Lys 16 is not involved in transition-state stabilization or GTP binding. However, replacement of Lys 16 with the isosteric uncharged Lys analogue, (hydroxyethyl)cysteine, led to a complete loss of GAP-stimulated GTPase activity, demonstrating the importance of the charged ammonium side chain. 22 refs., 1 fig., 1 tab.

  2. Using Unnatural Amino Acids to Probe the Energetics of Oxyanion Hole Hydrogen Bonds in the Ketosteroid Isomerase Active Site

    PubMed Central

    2015-01-01

    Hydrogen bonds are ubiquitous in enzyme active sites, providing binding interactions and stabilizing charge rearrangements on substrate groups over the course of a reaction. But understanding the origin and magnitude of their catalytic contributions relative to hydrogen bonds made in aqueous solution remains difficult, in part because of complexities encountered in energetic interpretation of traditional site-directed mutagenesis experiments. It has been proposed for ketosteroid isomerase and other enzymes that active site hydrogen bonding groups provide energetic stabilization via “short, strong” or “low-barrier” hydrogen bonds that are formed due to matching of their pKa or proton affinity to that of the transition state. It has also been proposed that the ketosteroid isomerase and other enzyme active sites provide electrostatic environments that result in larger energetic responses (i.e., greater “sensitivity”) to ground-state to transition-state charge rearrangement, relative to aqueous solution, thereby providing catalysis relative to the corresponding reaction in water. To test these models, we substituted tyrosine with fluorotyrosines (F-Tyr’s) in the ketosteroid isomerase (KSI) oxyanion hole to systematically vary the proton affinity of an active site hydrogen bond donor while minimizing steric or structural effects. We found that a 40-fold increase in intrinsic F-Tyr acidity caused no significant change in activity for reactions with three different substrates. F-Tyr substitution did not change the solvent or primary kinetic isotope effect for proton abstraction, consistent with no change in mechanism arising from these substitutions. The observed shallow dependence of activity on the pKa of the substituted Tyr residues suggests that the KSI oxyanion hole does not provide catalysis by forming an energetically exceptional pKa-matched hydrogen bond. In addition, the shallow dependence provides no indication of an active site electrostatic

  3. ANTS-anchored Zn-Al-CO3-LDH particles as fluorescent probe for sensing of folic acid

    NASA Astrophysics Data System (ADS)

    Liu, Pengfei; Liu, Dan; Liu, Yanhuan; Li, Lei

    2016-09-01

    A novel fluorescent nanosensor for detecting folic acid (FA) in aqueous media has been developed based on 8-aminonaphthalene-1,3,6-trisulfonate (ANTS) anchored to the surface of Zn-Al-CO3-layered double hydroxides (LDH) particles. The nanosensor showed high fluorescence intensity and good photostability due to a strong coordination interaction between surface Zn2+ ions of Zn-Al-CO3-LDH and N atoms of ANTS, which were verified by result of X-ray photoelectron spectroscopy (XPS). ANTS-anchored on the surface of Zn-Al-CO3-LDH restricted the intra-molecular rotation leading to ANTS-anchored J-type aggregation emission enhancement. ANTS-anchored Zn-Al-CO3-LDH particles exhibited highly sensitive and selective response to FA over other common metal ions and saccharides present in biological fluids. The proposed mechanism was that oxygen atoms of -SO3 groups in ANTS-anchored on the surface of Zn-Al-CO3-LDH were easily collided by FA molecules to form potential hydrogen bonds between ANTS-anchored and FA molecules, which could effectively quench the ANTS-anchored fluorescence. Under the simulated physiological conditions (pH of 7.4), the fluorescence quenching was fitted to Stern-Volmer equation with a linear response in the concentration range of 1 μM to 200 μM with a limit of detection of 0.1 μM. The results indicate that ANTS-anchored Zn-Al-CO3-LDH particles can afford a very sensitive system for the sensing FA in aqueous solution.

  4. Probing the conformation of a conserved glutamic acid within the Cl(-) pathway of a CLC H(+)/Cl(-) exchanger.

    PubMed

    Vien, Malvin; Basilio, Daniel; Leisle, Lilia; Accardi, Alessio

    2017-04-03

    The CLC proteins form a broad family of anion-selective transport proteins that includes both channels and exchangers. Despite extensive structural, functional, and computational studies, the transport mechanism of the CLC exchangers remains poorly understood. Several transport models have been proposed but have failed to capture all the key features of these transporters. Multiple CLC crystal structures have suggested that a conserved glutamic acid, Gluex, can adopt three conformations and that the interconversion of its side chain between these states underlies H(+)/Cl(-) exchange. One of these states, in which Gluex occupies the central binding site (Scen) while Cl(-) ions fill the internal and external sites (Sint and Sext), has only been observed in one homologue, the eukaryotic cmCLC. The existence of such a state in other CLCs has not been demonstrated. In this study, we find that during transport, the prototypical prokaryotic CLC exchanger, CLC-ec1, adopts a conformation with functional characteristics that match those predicted for a cmCLC-like state, with Gluex trapped in Scen between two Cl(-) ions. Transport by CLC-ec1 is reduced when [Cl(-)] is symmetrically increased on both sides of the membrane and mutations that disrupt the hydrogen bonds stabilizing Gluex in Scen destabilize this trapped state. Furthermore, inhibition of transport by high [Cl(-)] is abolished in the E148A mutant, in which the Gluex side chain is removed. Collectively, our results suggest that, during the CLC transport cycle, Gluex can occupy Scen as well as the Sext position in which it has been captured crystallographically and that hydrogen bonds with the side chains of residues that coordinate ion binding to Scen play a role in determining the equilibrium between these two conformations.

  5. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species.

    PubMed

    Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

    2017-02-10

    In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters.

  6. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species

    PubMed Central

    Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

    2017-01-01

    In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)-capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters. PMID:28208642

  7. Photoluminescence of water-soluble CdSe/ZnS nanoparticles in complexes with cationic and anionic polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Strekal', N.; Kulakovich, O.; Belyaev, A.; Stsiapura, V.; Maskevich, S.

    2008-01-01

    The data on the influence of polyelectrolytes on the photon emission probability of water-soluble CdSe/ZnS nanoparticles are obtained. The decrease in the photoluminescence quantum yield of nanoparticles occurring upon their transfer to aqueous solutions from toluene (in the course of solubilization) depends on the ionic nature of an agent applied for the replacement of trioctylphosphine oxide residues on the surface of nanoparticles. It turns out that such a cationic modifying agent as cysteamine leads to an insignificant (˜10%) decrease in the photoluminescence quantum yield of nanoparticles. The use of such an anionic agent as mercaptoacetic acid causes a significant (˜80%) decrease in the quantum yield and the average decay time of photoluminescence. For nanoparticles modified by mercaptoacetic acid (anionic nanoparticles), this decrease is partially compensated if these particles interact with polyelectrolytes whose backbone is oppositely charged (cationic polyelectrolytes), such as polyallylamine and polydiallyldimethylammonium chloride. In this case, the photoluminescence quantum yield shows a reverse increase by 40%, remaining the same within a matter of months or longer. In contrast to this, cationic nanoparticles, only slightly quenched by cysteamine at the stage of solubilization, are appreciably degraded in complexes with anionic polyelectrolytes in solutions and upon immobilization of complexes on a substrate, so that their photoluminescence quantum yield irreversible decreases to zero within a few days. Possible mechanisms of the effects observed are discussed and their consideration in polyelectrolyte-based molecular lithography.

  8. DNA detection using plasmonic enhanced near-infrared photoluminescence of gallium arsenide.

    PubMed

    Tang, Longhua; Chun, Ik Su; Wang, Zidong; Li, Jinghong; Li, Xiuling; Lu, Yi

    2013-10-15

    Efficient near-infrared detection of specific DNA with single nucleotide polymorphism selectivity is important for diagnostics and biomedical research. Herein, we report the use of gallium arsenide (GaAs) as a sensing platform for probing DNA immobilization and targeting DNA hybridization, resulting in ∼8-fold enhanced GaAs photoluminescence (PL) at ∼875 nm. The new signal amplification strategy, further coupled with the plasmonic effect of Au nanoparticles, is capable of detecting DNA molecules with a detection limit of 0.8 pM and selectivity against single base mismatches. Such an ultrasensitive near-infrared sensor can find a wide range of biochemical and biomedical applications.

  9. Defect States in Copper Indium Gallium Selenide Solar Cells from Two-Wavelength Excitation Photoluminescence Spectroscopy

    SciTech Connect

    Jensen, Soren A.; Dippo, Patricia; Mansfield, Lorelle M.; Glynn, Stephen; Kuciauskas, Darius

    2016-11-21

    We use two-wavelength excitation photoluminescence spectroscopy to probe defect states in CIGS thin films. Above-Eg excitation is combined with a tunable IR bias light that modulates the population of the defect states. We find that IR illumination in the range of 1400-2000 nm (0.62-0.89 eV) causes a reduction of the PL intensity, the magnitude of which scales linearly with IR power. Further, KF post deposition treatment has only a modest influence on the effect of the IR excitation. Initial data suggest that we have developed an optical characterization tool for band-gap defect states.

  10. Photoluminescent carbon dots synthesized by microwave treatment for selective image of cancer cells.

    PubMed

    Yang, Xudong; Yang, Xue; Li, Zhenyu; Li, Shouying; Han, Yexuan; Chen, Yang; Bu, Xinyuan; Su, Chunyan; Xu, Hong; Jiang, Yingnan; Lin, Quan

    2015-10-15

    In this work, a simple, low-cost and one-step microwave approach has been demonstrated for the synthesis of water-soluble carbon dots (C-dots). The average size of the resulting C-dots is about 4 nm. From the photoluminescence (PL) measurements, the C-dots exhibit excellent biocompatibility and intense PL with the high quantum yield (QY) at Ca. 25%. Significantly, the C-dots have excellent biocompatibility and the capacity to specifically target the cells overexpressing the folate receptor (FR). These exciting results indicate the as-prepared C-dots are promising biocompatible probe for cancer diagnosis and treatment.

  11. Detecting asymptomatic Trichomonas vaginalis in females using the BD ProbeTec™ Trichomonas vaginalis Q(x) nucleic acid amplification test.

    PubMed

    Lord, Emily; Newnham, Tana; Dorrell, Lucy; Jesuthasan, Gerald; Clarke, Lorraine; Jeffery, Katie; Sherrard, Jackie

    2017-03-01

    Trichomonas vaginalis (TV) rates in women are increasing and many are asymptomatic. Nucleic acid amplification tests (NAATs) are becoming the 'gold standard' for diagnosis. We aimed to establish our asymptomatic TV rates by testing all women attending Oxfordshire's Sexual Health service, regardless of symptoms, using the BD ProbeTec™ TV Q(x) NAATs (BDQ(x)). During BDQ(x)'s verification process, the sensitivity and specificity were calculated using results of 220 endocervical samples from symptomatic women, compared with culture. BDQ(x) was subsequently implemented and prospectively evaluated over 6 months in female attendees. Wet mount microscopy was also performed in symptomatics. Demographic and clinical characteristics of those diagnosed were analysed. From 220 samples tested by BDQ(x) and culture: 5 were positive on both and one solely using BDQ(x), giving a sensitivity and specificity of 100% and 99.53%, respectively. In the prospective cohort, of 5775 BDQ(x) tests, 33 (0.57%) were positive. 11/33 (33%) patients were asymptomatic. All patients diagnosed had risk factors: age >25 years (85%), residence in a deprived area (79%) and black ethnicity (21%). Despite BDQ(x) being highly sensitive and specific, with our low TV prevalence universal screening may not be justified. Targeted screening using local demographic data merits further investigation.

  12. Effect of Glucose on the Fatty Acid Composition of Cupriavidus necator JMP134 during 2,4-Dichlorophenoxyacetic Acid Degradation: Implications for Lipid-Based Stable Isotope Probing Methods▿†

    PubMed Central

    Lerch, Thomas Z.; Dignac, Marie-France; Barriuso, Enrique; Mariotti, André

    2011-01-01

    Combining lipid biomarker profiling with stable isotope probing (SIP) is a powerful technique for studying specific microbial populations responsible for the degradation of organic pollutants in various natural environments. However, the presence of other easily degradable substrates may induce significant physiological changes by altering both the rate of incorporation of the target compound into the biomass and the microbial lipid profiles. In order to test this hypothesis, Cupriavidus necator JMP134, a 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacterium, was incubated with [13C]2,4-D, [13C]glucose, or mixtures of both substrates alternatively labeled with 13C. C. necator JMP134 exhibited a preferential use of 2,4-D over glucose. The isotopic analysis showed that glucose had only a small effect on the incorporation of the acetic chain of 2,4-D into the biomass (at days 2 and 3) and no effect on that of the benzenic ring. The addition of glucose did change the fatty acid methyl ester (FAME) composition. However, the overall FAME isotopic signature reflected that of the entire biomass. Compound-specific individual isotopic analyses of FAME composition showed that the 13C-enriched FAME profiles were slightly or not affected when tracing the 2,4-D acetic chain or 2,4-D benzenic ring, respectively. This batch study is a necessary step for validating the use of lipid-based SIP methods in complex environments. PMID:21856833

  13. Probing the interaction induced conformation transitions in acid phosphatase with cobalt ferrite nanoparticles: Relation to inhibition and bio-activity of Chlorella vulgaris acid phosphatase.

    PubMed

    Ahmad, Farooq; Zhou, Xing; Yao, Hongzhou; Zhou, Ying; Xu, Chao

    2016-09-01

    The present study explored the interaction and kinetics of cobalt ferrite nanoparticles (NPs) with acid phosphatase (ACP) by utilizing diverse range of spectroscopic techniques. The results corroborate, the CoFe2O4 NPs cause fluorescence quenching in ACP by static quenching mechanism. The negative values of van't Hoff thermodynamic expressions (ΔH=-0.3293Jmol(-1)K(-1) and ΔG=-3.960kJmol(-1)K(-1)) corroborate the spontaneity and exothermic nature of static quenching. The positive value of ΔS (13.2893Jmol(-1)K(-1)) corroborate that major contributors of higher and stronger binding affinity among CoFe2O4 NPs with ACP were electrostatic. In addition, FTIR, UV-CD, UV-vis spectroscopy and three dimensional fluorescence (3D) techniques confirmed that CoFe2O4 NPs binding induces microenvironment perturbations leading to secondary and tertiary conformation changes in ACP to a great extent. Furthermore, synchronous fluorescence spectroscopy (SFS) affirmed the comparatively significant changes in microenvironment around tryptophan (Trp) residue by CoFe2O4 NPs. The effect of CoFe2O4 NPs on the activation kinetics of ACP was further examined in Chlorella vulgaris. Apparent Michaelis constant (Km) values of 0.57 and 26.5mM with activation energy values of 0.538 and 3.428kJmol(-1) were determined without and with 200μM CoFe2O4 NPs. Apparent Vmax value of -7Umml(-1) corroborate that enzyme active sites were completely captured by the NPs leaving no space for the substrate. The results confirmed that CoFe2O4 NPs ceased the activity by unfolding of ACP enzyme. This suggests CoFe2O4 NPs perturbed the enzyme activity by transitions in conformation and hence the metabolic activity of ACP. This study provides the pavement for novel and simple approach of using sensitive biomarkers for sensing NPs in environment.

  14. Printable temperature-responsive hybrid hydrogels with photoluminescent carbon nanodots

    NASA Astrophysics Data System (ADS)

    Li, Panpan; Huang, Lei; Lin, Youjie; Shen, Leo; Chen, Qi; Shi, Wangzhou

    2014-02-01

    Smart ink-like hybrid hydrogels that simultaneously possess semi-interpenetrating network structure, strong photoluminescence and temperature sensitivity are successfully fabricated based on the crosslink of poly(acrylamide) (PAAm) in the presence of poly(N-isopropylacrylamide) (PNIPAM) and carbon nanodots (CNDs) at room temperature. The resulting hybrid hydrogels were highly photoluminescent. The photoluminescence was sensitive to external temperature stimuli and reversible. Moreover, the hybrid hydrogels were applied as fluorescent inks for patterning using gravure printing, which may open a door towards developing smart CND based thermosensitive photoluminescent markers and sensors.

  15. Preparation and photoluminescence properties of MMoO4 (M = Cu, Ni, Zn) nano-particles synthesized via electrolysis

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Yin, Jiajia; Min, Fanqi; Jia, Lili; Zhang, Daoming; Zhang, Quansheng; Xie, Jingying

    2017-01-01

    Metal molybdate (MMoO4, M = Cu, Ni, Zn) nano-particles were successfully synthesized by electrochemical method in a cation exchange membrane electrolytic cell with Na2MoO4 solution as anolyte, diluted hydrochloric acid (HCl) as catholyte, metal (Cu, Ni, Zn) as anode and stainless steel as cathode. The composition, morphology, structure, microstructure and photoluminescence property of the synthesized MMoO4 were investigated and characterized. The results show that the photoluminescence spectra of electrolytic synthesized MMoO4 have fine structures, which is markedly different from the existing research.

  16. Photoluminescence in anthracene and it's derivatives

    NASA Astrophysics Data System (ADS)

    Vyas, Arpita; Mirgane, Nitin A.; Moharil, S. V.; Muley, Aarti Iyer

    2016-05-01

    The anthracene and it's derivative 9-chloro acridine and Anthracene-9-ylmethylacetate have prepared in Poly vinyl alcohol(PVOH). Their photoluminescence properties have studied. The pure anthracene has an emission at 424 and 443nm. The intense peak is observed at 465nm and shoulder at 407nm. The derivatives of anthracene Anthracene-9-ylmethylacetate shows an emission around 440nm for the excitation at 393nm and 9-chloro acridine shows emission around 360nm for the excitation at 290nm. The major problem of this organic material is the stability. The composites prepared in the medium of PVOH are more stable.

  17. Photoluminescence study in diaminobenzene functionalized graphene oxide

    SciTech Connect

    Gupta, Abhisek E-mail: cnssks@iacs.res.in; Saha, Shyamal K. E-mail: cnssks@iacs.res.in

    2014-10-15

    Being an excellent electronic material graphene is a very poor candidate for optoelectronic applications. One of the major strategies to develop the optical property in GO is the functionalization of graphene oxide (GO). In the present work GO sheets are functionalized by o-phenylenediamine to achieve diaminobenzene functionalized GO composite (DAB-GO). Formation of DAB-GO composite is further characterized by FTIR, UV, Raman studies. Excellent photoluminescence is observed in DAB-GO composite via passivation of the surface reactive sites by ring-opening amination of epoxides of GO.

  18. Photoluminescence Study of Copper Selenide Thin Films

    NASA Astrophysics Data System (ADS)

    Urmila, K. S.; Asokan, T. Namitha; Pradeep, B.

    2011-10-01

    Thin films of Copper Selenide of composition of composition Cu7Se4 with thickness 350 nm are deposited on glass substrate at a temperature of 498 K±5 K and pressure of 10-5 mbar using reactive evaporation, a variant of Gunther's three temperature method with high purity Copper (99.999%) and Selenium (99.99%) as the elemental starting material. The deposited film is characterized structurally using X-ray Diffraction. The structural parameters such as lattice constant, particle size, dislocation density; number of crystallites per unit area and strain in the film are evaluated. Photoluminescence of the film is analyzed at room temperature using Fluoro Max-3 Spectrofluorometer.

  19. Optical probe

    DOEpatents

    Hencken, Kenneth; Flower, William L.

    1999-01-01

    A compact optical probe is disclosed particularly useful for analysis of emissions in industrial environments. The instant invention provides a geometry for optically-based measurements that allows all optical components (source, detector, rely optics, etc.) to be located in proximity to one another. The geometry of the probe disclosed herein provides a means for making optical measurements in environments where it is difficult and/or expensive to gain access to the vicinity of a flow stream to be measured. Significantly, the lens geometry of the optical probe allows the analysis location within a flow stream being monitored to be moved while maintaining optical alignment of all components even when the optical probe is focused on a plurality of different analysis points within the flow stream.

  20. In situ hybridization for Coccidioides immitis 5.8S ribosomal RNA sequences in formalin-fixed, paraffin-embedded pulmonary specimens using a locked nucleic acid probe: a rapid means for identification in tissue sections.

    PubMed

    Montone, Kathleen T; Litzky, Leslie A; Feldman, Michael D; Peterman, Heather; Mathis, Benjamin; Baliff, Jeffrey; Kaiser, Larry R; Kucharczuk, John; Nachamkin, Irving

    2010-06-01

    Coccidioides immitis/Coccidioides posadasii are common causes of pulmonary infection in certain geographic areas, and are highly infectious when working with culture isolates in the laboratory. Rapid techniques to accurately identify this pathogen in tissues may be of benefit for diagnosis and in limiting the exposure of laboratory personnel to this agent. Locked nucleic acids (LNA) are modified nucleotides in which a ribonucleoside is linked between the 2'-oxygen and the 4'-carbon atoms with a methylene unit. LNA oligonucleotides exhibit increased thermal stability and make excellent probes for in situ hybridization (ISH). In this study, ISH utilizing a biotin-labeled LNA probe targeting Coccidioides sp. ribosomal RNA sequences in 6 formalin-fixed, paraffin-embedded pulmonary tissue specimens from 6 patients with culture positive or histologic findings suggestive of Coccidioides sp. infection is described. The cultures of the pulmonary specimens confirmed C. immitis in 3 of 6 patients. The ISH procedure with the LNA probe was positive in all 6 cases, although the number of organisms that were highlighted varied from rare to numerous. ISH with a biotin-labeled DNA probe of the same sequence was positive in 4 of the 6 cases and the signal intensity and number of organisms was much less than that observed with the LNA probe. Negative control tissues containing a variety of different fungal pathogens including Aspergillus sp., Fusarium sp., Blastomyces dermatitidis, Candida sp, Histoplasma capsulatum, and Zygomyces did not hybridize with the LNA and DNA probes. ISH with an LNA oligonucleotide probe targeting Coccidioides sp. ribosomal RNA is useful for rapid ISH. ISH could be rapidly performed when fungal pathogens are observed in tissue but cultures are negative or have not been performed.

  1. Synthesis of circular double-stranded DNA having single-stranded recognition sequence as molecular-physical probe for nucleic acid hybridization detection based on atomic force microscopy imaging.

    PubMed

    Nakano, Koji; Matsunaga, Hideshi; Murata, Masaharu; Soh, Nobuaki; Imato, Toshihiko

    2009-08-01

    A new class of DNA probes having a mechanically detectable tag is reported. The DNA probe, which consists of a single-stranded recognition sequence and a double-stranded circular DNA entity, was prepared by polymerase reaction. M13mp18 single strand and a 32mer oligodeoxynucleotide whose 5'-end is decorated with the recognition sequence were used in combination as template and primer, respectively. We have successfully demonstrated that the DNA probe is useful for bioanalytical purposes: by deliberately attaching target DNA molecules onto Au(111) substrates and by mechanically reading out the tag-entity using a high-resolution microscopy including atomic force microscopy, visualization/detection of the individual target/probe DNA conjugate was possible simply yet straightforwardly. The present DNA probe can be characterized as a 100%-nucleic acid product material. It is simply available by one-pod synthesis. A surface topology parameter, image roughness, has witnessed its importance as a quantitative analysis index with particular usability in the present visualization/detection method.

  2. A turn-on highly selective and ultrasensitive determination of copper (II) in an aqueous medium using folic acid capped gold nanoparticles as the probe

    NASA Astrophysics Data System (ADS)

    Vasimalai, N.; Prabhakarn, A.; John, S. Abraham

    2013-12-01

    This paper describes a ‘turn-on’ fluorescent determination of Cu(II) in an aqueous medium using folic acid capped gold nanoparticles (FA-AuNPs) as the probe. The FA-AuNPs were synthesized by the wet chemical method and were characterized by UV-visible, fluorescence, HR-TEM, XRD, zeta potential, and DLS techniques. The FA-AuNPs show an absorption maximum at 510 nm and an emission maximum at 780 nm (λex: 510 nm). On adding 10 μM Cu(II), the wine-red color of FA-AuNPs changed to purple and the absorbance at 510 nm decreased. The observed changes were ascribed to the aggregation of AuNPs. This was confirmed by DLS and HR-TEM studies. Interestingly, the emission intensity of FA-AuNPs was enhanced even in the presence of a picomolar concentration of Cu(II). Based on the enhancement of the emission intensity, the concentration of Cu(II) was determined. The FA-AuNPs showed an extreme selectivity towards the determination of 10 nM Cu(II) in the presence of 10 000-fold higher concentration of interferences except EDTA and the carboxylate anion. A good linearity was observed from 10 × 10-9 to 1 × 10-12 M Cu(II), and the detection limit was found to be 50 fM l-1 (S/N = 3). The proposed method was successfully applied to determine Cu(II) in real samples. The results obtained were validated with ICP-AES.

  3. Gold nanoclusters as switch-off fluorescent probe for detection of uric acid based on the inner filter effect of hydrogen peroxide-mediated enlargement of gold nanoparticles.

    PubMed

    Liu, Yanyan; Li, Hongchang; Guo, Bin; Wei, Lijuan; Chen, Bo; Zhang, Youyu

    2017-05-15

    Herein we report a novel switch-off fluorescent probe for highly selective determination of uric acid (UA) based on the inner filter effect (IFE), by using poly-(vinylpyrrolidone)-protected gold nanoparticles (PVP-AuNPs) and chondroitin sulfate-stabilized gold nanoclusters (CS-AuNCs) as the IFE absorber/fluorophore pair. In this IFE-based fluorometric assay, the newly designed CS-AuNCs were explored as an original fluorophore and the hydrogen peroxide (H2O2) -driven formed PVP-AuNPs can be a powerful absorber to influence the excitation of the fluorophore, due to the complementary overlap between the absorption band of PVP-AuNPs and the emission band of CS-AuNCs. Under the optimized conditions, the extent of the signal quenching depends linearly on the H2O2 concentration in the range of 1-100μM (R(2) =0.995) with a detection limit down to 0.3μM. Based on the H2O2-dependent fluorescence IFE principle, we further developed a new assay strategy to enable selective sensing of UA by using a specific uricase-catalyzed UA oxidation as the in situ H2O2 generator. The proposed uricase-linked IFE-based assay exhibited excellent analytical performance for measuring UA over the concentration ranging from 5 to 100μM (R(2)=0.991), and can be successfully applied to detection of UA as low as 1.7μM (3σ) in diluted human serum samples.

  4. Influence of cysteine doping on photoluminescence intensity from semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kurnosov, N. V.; Leontiev, V. S.; Linnik, A. S.; Karachevtsev, V. A.

    2015-03-01

    Photoluminescence (PL) from semiconducting single-walled carbon nanotubes can be applied for detection of cysteine. It is shown that cysteine doping (from 10-8 to 10-3 M) into aqueous suspension of nanotubes with adsorbed DNA leads to increase of PL intensity. The PL intensity was enhanced by 27% at 10-3 M cysteine concentration in suspension. Most likely, the PL intensity increases due to the passivation of p-defects on the nanotube by the cysteine containing reactive thiol group. The effect of doping with other amino acids without this group (methionine, serine, aspartic acid, lysine, proline) on the PL intensity is essentially weaker.

  5. Hydrothermal synthesis, crystal structures and photoluminescence properties of mixed europium-yttrium organic frameworks

    NASA Astrophysics Data System (ADS)

    Han, Yinfeng; Fu, Lianshe; Mafra, Luís; Shi, Fa-Nian

    2012-02-01

    Three mixed europium-yttrium organic frameworks: Eu2-xYx(Mel)(H2O)6 (Mel=mellitic acid or benzene-1,2,3,4,5,6-hexacarboxylic acid, x=0.38 1, 0.74 2, and 0.86 3) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu3+ lifetime becomes longer in these MOFs than those of the Eu analog.

  6. The correlation of blue shift of photoluminescence and morphology of silicon nanoporous

    NASA Astrophysics Data System (ADS)

    Al-Jumaili, Batool E. B.; Talib, Zainal A.; Josephine L., Y.; Paiman, Suriati B.; Ahmed, Naser M.; Al-Jumaily, Abdulmajeed H. J.; Ramizy, Asmiet; Abdulateef, Sinan A.; Muh'd, Ibrahim B.; Mofdal, Manahil E. E.

    2016-07-01

    Porous silicon with diameters ranging from 6.41 to 7.12 nm were synthesized via electrochemical etching by varied anodization current density in ethanoic solutions containing aqueous hydrofluoric acid up to 65mA/cm2.The luminescence properties of the nanoporous at room temperature were analyzed via photoluminescence spectroscopy. Photoluminescence PL spectra exhibit a broad emission band in the range of 360-700 nm photon energy. The PL spectrum has a blue shift in varied anodization current density; the blue shift incremented as the existing of anodization although the intensity decreased. The current blue shift is owning to alteration of silicon nanocrystal structure at the superficies. The superficial morphology of the PS layers consists of unified and orderly distribution of nanocrystalline Si structures, have high porosity around (93.75%) and high thickness 39.52 µm.

  7. Highly Photoluminescent Molybdenum Oxide Quantum Dots: One-Pot Synthesis and Application in 2,4,6-Trinitrotoluene Determination.

    PubMed

    Xiao, Sai Jin; Zhao, Xiao Jing; Hu, Ping Ping; Chu, Zhao Jun; Huang, Cheng Zhi; Zhang, Li

    2016-03-01

    As a well-studied transition-metal semiconductor material, MoOx has a wider band gap than molybdenum disulfide (MoS2), and its property varies dramatically for the existence of several different allotropes and suboxide phases of molybdenum oxides (MoOx, x < 3). In this manuscript, a one-pot method possessing the advantages of one pot, easily prepared, rapid, and environmentally friendly, has been developed for facile synthesis of highly photoluminescent MoOx quantum dots (MoOx QDs), in which commercial molybdenum disulfide (MoS2) powder and hydrogen peroxide (H2O2) are employed as the precursor and oxidant, respectively. The obtained MoOx QDs can be further utilized as an efficient photoluminescent probe, and a new turn-off sensor is developed for 2,4,6-trinitrotoluene (TNT) determination based on the fact that the photoluminescence of MoOx QDs can be quenched by the Meisenheimer complexes formed in the strong alkali solution through the inner filter effect (IFE). Under the optimal conditions, the decreased photoluminescence of MoOx QDs shows a good linear relationship to the concentration of TNT ranging from 0.5 to 240.0 μM, and the limit of detection was 0.12 μM (3σ/k). With the present turn-off sensor, TNT in river water samples can be rapidly and selectively detected without tedious sample pretreatment processes.

  8. Optical properties in complex-structured nanometric quantum wells: Photoluminescence, photoluminescence excitation, and Stokes shift

    NASA Astrophysics Data System (ADS)

    Silva, A. A. P.; Vasconcellos, Áurea. R.; Luzzi, Roberto; Meneses, E. A.; Laureto, E.

    2009-10-01

    Systems in which one or more directions are in the nanometric space scale exhibit significantly some peculiar phenomena and processes. We consider here the case of nanometric quantum wells with complex structure, displaying fractal-like characteristics, which are part of semiconductor heterostructures. An extensive theoretical study of the optical properties of photoluminescence and excited photoluminescence, and then involving absorption and the question of emergence of the so-called Stokes shift that is observed in some cases are performed. The results are compared with some experimental data. This is of relevance for opening up the possibility to use optical measurements to perform a (nondestructive) quality control of samples grown under different methods and protocols.

  9. Preparation ways and photoluminescence of mesoporous alumina

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Liu, J.; Zhao, X.; Wu, G.

    2010-12-01

    High specific surface area (SSA) mesoporous alumina (MA) is synthesized by a sol-gel method using pelagic clay as the raw material. The MA synthesized with a (1-hexadecyl) trimethylammonium bromide (CTAB): utea mixed template shows a SSA of 385.56 m2/g and a mean pore size of 3.6 nm. And the SSA of the MA synthesized with the mixed template is increased compared with the MA synthesized with a CTAB single template. Simultaneously, the MA exhibits a blue photoluminescence which come from the defect F+ and F centers, and the higher PL emission of the MA synthesized with a CTAB: utea mixed template is attributed to the high defect center density in the MA.

  10. Photoluminescence studies in epitaxial CZTSe thin films

    NASA Astrophysics Data System (ADS)

    Sendler, Jan; Thevenin, Maxime; Werner, Florian; Redinger, Alex; Li, Shuyi; Hägglund, Carl; Platzer-Björkman, Charlotte; Siebentritt, Susanne

    2016-09-01

    Epitaxial Cu 2 ZnSnSe 4 (CZTSe) thin films were grown by molecular beam epitaxy on GaAs(001) using two different growth processes, one containing an in-situ annealing stage as used for solar cell absorbers and one for which this step was omitted. Photoluminescences (PL) measurements carried out on these samples show no dependence of the emission shape on the excitation intensity at different temperatures ranging from 4 K to 300 K . To describe the PL measurements, we employ a model with fluctuating band edges in which the density of states of the resulting tail states does not seem to depend on the excited charge carrier density. In this interpretation, the PL measurements show that the annealing stage removes a defect level, which is present in the samples without this annealing.

  11. Highly nonlinear photoluminescence threshold in porous silicon

    SciTech Connect

    Nayfeh, M.; Akcakir, O.; Therrien, J.; Yamani, Z.; Barry, N.; Yu, W.; Gratton, E.

    1999-12-27

    Porous silicon is excited using near-infrared femtosecond pulsed and continuous wave radiation at an average intensity of {approx}10{sup 6} W/cm{sup 2} (8x10{sup 10} W/cm{sup 2} peak intensity in pulsed mode). Our results demonstrate the presence of micron-size regions for which the intensity of the photoluminescence has a highly nonlinear threshold, rising by several orders of magnitude near this incident intensity for both the pulsed and continuous wave cases. These results are discussed in terms of stimulated emission from quantum confinement engineered intrinsic Si-Si radiative traps in ultrasmall nanocrystallites, populated following two-photon absorption. (c) 1999 American Institute of Physics.

  12. Nanopowder Metal Oxide for Photoluminescent Gas Sensing

    NASA Astrophysics Data System (ADS)

    Zhyrovetsky, V. M.; Popovych, D. I.; Savka, S. S.; Serednytski, A. S.

    2017-02-01

    Gas sensing properties of metal oxide nanopowders (ZnO, TiO2, WO3, SnO2) with average diameters of 40-60 nm were analyzed by room-temperature photoluminescence spectroscopy. The influence of gas environment (O2, N2, H2, CO, CO2) on the emission intensity was investigated for metal oxide nanopowders with surface doped by impurities (Pt, Ag, Au, Sn, Ni or Cu). Established physicochemical regularities of modification of surface electronic states of initial and doped nanopowders during gas adsorption. The nature of metal oxide nanopowder gas-sensing properties (adsorption capacity, sensitivity, selectivity) has been established and the design and optimal materials for the construction of the multi-component sensing matrix have been selected.

  13. Simulation of J-aggregate microcavity photoluminescence

    NASA Astrophysics Data System (ADS)

    Michetti, Paolo; La Rocca, Giuseppe C.

    2008-05-01

    We have developed a model in order to account for the photoexcitation dynamics of J-aggregate films and strongly coupled J-aggregate microcavities. The J aggregates are described as a disordered Frenkel exciton system in which relaxation occurs due to the presence of a thermal bath of molecular vibrations. The correspondence between the photophysics in J-aggregate films and that in J-aggregate microcavities is obtained by introducing a model polariton wave function mixing cavity photon modes and J-aggregate super-radiant excitons. With the same description of the material properties, we have calculated both absorption and luminescence spectra for the J-aggregate film and the photoluminescence of strongly coupled organic microcavities. The model is able to account for the fast relaxation dynamics in organic microcavities following nonresonant pumping and explains the temperature dependence of the ratio between the upper polariton and the lower polariton luminescence.

  14. Pollution Probe.

    ERIC Educational Resources Information Center

    Chant, Donald A.

    This book is written as a statement of concern about pollution by members of Pollution Probe, a citizens' anti-pollution group in Canada. Its purpose is to create public awareness and pressure for the eventual solution to pollution problems. The need for effective government policies to control the population explosion, conserve natural resources,…

  15. Design, synthesis, and biological evaluation of 4-(5-dimethylamino-naphthalene-1-sulfon-amido)-3-(4-iodophenyl)butanoic acid as a novel molecular probe for apoptosis imaging

    SciTech Connect

    Zeng, Wenbin; Miao, Weimin; Le Puil, Michael; Shi, Guangqing; Biggerstaff, John; Kabalka, George W.; Townsend, David

    2010-07-30

    Research highlights: {yields} Annexin V is the gold standard probe for imaging apoptosis. {yields} Unfavorable profiles of Annexin V make it difficult to apply in the clinic. {yields} A novel small-molecular probe DNSBA was designed as an alternative to Annexin V. {yields} DNSBA specifically and selectively detect apoptotic cancer cells at all stages. {yields} DNSBA is a potential SPECT and PET agent when labeled with radioiodine. -- Abstract: Apoptosis (programmed cell death) plays a crucial role in the pathogenesis of many disorders, thus the detection of apoptotic cells can provide the physician with important information to further therapeutic strategies and would substantially advance patient care. A small molecule, 4-(5-dimethylamino-naphthalene-1-sulfonamido)-3-(4-iodo-phenyl)butanoic acid (DNSBA), was designed as a novel probe for imaging apoptosis and synthesized with good yield. The biological characterization demonstrated that DNSBA can be used to specifically and selectively detect apoptotic cancer cells at all stages. DNSBA is also designed as a potential SPECT and PET probe when labeled with radioiodine (I-123, -124, and -131).

  16. Signal enhancement for gene detection based on a redox reaction of [Fe(CN)(6)](4-) mediated by ferrocene at the terminal of a peptide nucleic acid as a probe with hybridization-amenable conformational flexibility.

    PubMed

    Aoki, Hiroshi; Tao, Hiroaki

    2008-07-01

    Electrochemically enhanced DNA detection was demonstrated by utilizing the couple of a synthesized ferrocene-terminated peptide nucleic acid (PNA) with a cysteine anchor and a sacrificial electron donor [Fe(CN)(6)](4-). DNA detection sensors were prepared by modifying a gold electrode surface with a mixed monolayer of the probe PNA and 11-hydroxy-1-undecanethiol (11-HUT), protecting [Fe(CN)(6)](4-) from any unexpected redox reaction. Before hybridization, the terminal ferrocene moiety of the probe was subject to a redox reaction due to the flexible probe structure and, in the presence of [Fe(CN)(6)](4-), the observed current was amplified based on regeneration of the ferrocene moiety. Hybridization decreased the redox current of the ferrocene. This occurred because hybridization rigidified the probe structure: the ferrocene moiety was then removed from the electrode surface, and the redox reaction of [Fe(CN)(6)](4-) was again prevented. The change in the anodic current before and after hybridization was enhanced 1.75-fold by using the electron donor [Fe(CN)(6)](4-). Sequence-specific detection of the complementary target DNA was also demonstrated.

  17. Photoluminescence and Raman spectroscopy of photoelectrochemical solar cells

    SciTech Connect

    Garuthara, R.K.A.

    1986-01-01

    The CdSe/polysulfide system was studied in order to produce low-cost liquid-junction solar cells. Three basic area were investigated: (1) space-charge-layer effects, (2) aging of photoanodes due to slow chemical changes on electrode surface, and (3) the effect of photoetching and the impurity centers in photoanodes. Relaxation spectrum analysis, photoluminescence, modulated photoluminescence, and Raman spectroscopy were utilized to study these areas. The potential distribution at the interface of n-type CdSe/polysulfide was examined. At reverse bias and at electrode potential, the modulated photoluminescence is described by the dead layer model. The electrical characterization of the interface, based on modulated photoluminescence, agrees with the relaxation spectrum-analysis measurements. The slow chemical changes on the CdSe/polysulfide liquid-junction solar cells, as a function of aging procedures, were studied using photoluminescence and Raman spectroscopy. For the first time, it is reported that cells do age under open-circuit conditions. The effect of photoetching on single crystal n-type CdSe was investigated, using photoluminescence spectroscopy. A blue-shift is observed in the photoluminescence spectrum of crystals when the doping density is decreased.

  18. From natural attapulgite to phosphor materials: Characterization, photoluminescence and structure

    SciTech Connect

    Wang, Wenjie; Gu, Zheng; Gao, Xiuping; Jiang, Huie; Liu, Weisheng

    2014-08-15

    Highlights: • Sr{sub 2.965}Al{sub 0.08}Si{sub 0.92}O{sub 5}:0.025Ce{sup 3+}, 0.01Eu{sup 2+} phosphor was synthesized from natural attapulgite. • Pure Sr{sub 3}SiO{sub 5} phase can be easily obtained. • It provides a new application field as phosphor for natural attapulgite. - Abstract: Sr{sub 2.965}Al{sub 0.08}Si{sub 0.92}O{sub 5}:0.025Ce{sup 3+}, 0.01Eu{sup 2+} (SrAlSiO:Ce{sup 3+}, Eu{sup 2+}) phosphor from natural attapulgite (ATP) was synthesized by solid-state reaction method. For the use of ATP as a source of Si and Al, pretreatment process including mechanical grinding and acid leaching were involved. X-ray diffraction patterns confirmed the formation of silicates in a wide temperature field, whereas Sr{sub 3}SiO{sub 5} within a single step. The ATP fibers were tuning into phosphor particles (about 1.5–3.0 μm) after calcination. Furthermore, photoluminescence spectra of the SrAlSiO:Ce{sup 3+}, Eu{sup 2+} phosphor was also in good agreement with the literature results, indicating a promising potential application as an effective candidate for warm-white LEDs materials.

  19. Serotypic differentiation of rotaviruses in field samples from diarrheic pigs by using nucleic acid probes specific for porcine VP4 and human and porcine VP7 genes.

    PubMed Central

    Rosen, B I; Parwani, A V; Lopez, S; Flores, J; Saif, L J

    1994-01-01

    Of 216 fecal and intestinal samples collected from nursing or weaned diarrheic pigs in the United States and Canada, 57 were identified as group A rotavirus positive by RNA electrophoresis and silver staining. Fifty-seven and 52 rotavirus-positive samples were analyzed by hybridization with Gottfried and OSU PCR-derived gene 9 and 4 probes, respectively. Only 17 samples were identified with either homologous VP4 (P)- or VP7 (G)-coding genes or both. One rotavirus identified as G4 and P7 was similar to the previously characterized interserotype rotavirus, SB-1A. Additional hybridization analyses were performed with PCR-derived probes prepared from gene 9 cDNA of the human rotaviruses Wa (G1), DS-1 (G2), and P (G3) and of the porcine rotavirus YM (G11). Eleven of 52 samples collected and analyzed from swine in Ohio, California, and Nebraska were identified as G11. No samples with G1-, G2-, or G3-type specificities were detected among the 25 of 57 rotavirus-positive samples analyzed with human rotavirus-derived probes. Further investigations with a PCR-derived gene 4 probe prepared from porcine rotavirus YM revealed hybridization specificities similar to those of the OSU gene 4 probe. Images PMID:8150940

  20. On the origin of photoluminescence in indium oxide octahedron structures

    SciTech Connect

    Kumar, Mukesh; Singh, V. N.; Mehta, B. R.; Singh, J. P.; Singh, F.; Lakshmi, K. V.

    2008-04-28

    A sixfold decrease in photoluminescence signal intensity at 590 nm with increase in deposition time from 3 to 12 h has been observed in single crystalline indium oxide octahedron structures grown by vapor-phase evaporation method. Electron paramagnetic resonance and energy dispersive x-ray analysis confirm that the concentration of oxygen vacancies increases with deposition time. These results are contrary to the previous reports where oxygen vacancies were shown to be responsible for photoluminescence in indium oxide structures. Our results indicate that indium interstitials and their associated complex defects other than oxygen vacancies are responsible for the photoluminescence in In{sub 2}O{sub 3} microstructures.

  1. Studies on surface plasmon resonance and photoluminescence of silver nanoparticles.

    PubMed

    Smitha, S L; Nissamudeen, K M; Philip, Daizy; Gopchandran, K G

    2008-11-01

    Silver nanoparticles of different sizes were prepared by citrate reduction and characterized by UV-vis absorbance spectra, TEM images and photoluminescence spectra. The morphology of the colloids obtained consists of a mixture of nanorods and spheres. The surface plasmon resonance (SPR) and photoemission properties of Ag nanoparticles are found to be sensitive to citrate concentration. A blue shift in SPR and an enhancement in photoluminescence intensity are observed with increase in citrate concentration. Effect of addition of KCl and variation of pH in photoluminescence was also studied.

  2. Photoluminescence Imaging of Polyfluorene Surface Structures on Semiconducting Carbon Nanotubes: Implications for Thin Film Exciton Transport

    SciTech Connect

    Hartmann, Nicolai F.; Pramanik, Rajib; Dowgiallo, Anne-Marie; Ihly, Rachelle; Blackburn, Jeffrey L.; Doorn, Stephen K.

    2016-12-27

    Single-walled carbon nanotubes (SWCNTs) have potential to act as light-harvesting elements in thin film photovoltaic devices, but performance is in part limited by the efficiency of exciton diffusion processes within the films. Factors contributing to exciton transport can include film morphology encompassing nanotube orientation, connectivity, and interaction geometry. Such factors are often defined by nanotube surface structures that are not yet well understood. Here, we present the results of a combined pump-probe and photoluminescence imaging study of polyfluorene (PFO)-wrapped (6,5) and (7,5) SWCNTs that provide additional insight into the role played by polymer structures in defining exciton transport. Pump-probe measurements suggest exciton transport occurs over larger length scales in films composed of PFO-wrapped (7,5) SWCNTs, compared to those prepared from PFO-bpy-wrapped (6,5) SWCNTs. To explore the role the difference in polymer structure may play as a possible origin of differing transport behaviors, we performed a photoluminescence imaging study of individual polymer-wrapped (6,5) and (7,5) SWCNTs. The PFO-bpy-wrapped (6,5) SWCNTs showed more uniform intensity distributions along their lengths, in contrast to the PFO-wrapped (7,5) SWCNTs, which showed irregular, discontinuous intensity distributions. These differences likely originate from differences in surface coverage and suggest the PFO wrapping on (7,5) nanotubes produces a more open surface structure than is available with the PFO-bpy wrapping of (6,5) nanotubes. The open structure likely leads to improved intertube coupling that enhances exciton transport within the (7,5) films, consistent with the results of our pump-probe measurements.

  3. Photoluminescence Imaging of Polyfluorene Surface Structures on Semiconducting Carbon Nanotubes: Implications for Thin Film Exciton Transport.

    PubMed

    Hartmann, Nicolai F; Pramanik, Rajib; Dowgiallo, Anne-Marie; Ihly, Rachelle; Blackburn, Jeffrey L; Doorn, Stephen K

    2016-12-27

    Single-walled carbon nanotubes (SWCNTs) have potential to act as light-harvesting elements in thin film photovoltaic devices, but performance is in part limited by the efficiency of exciton diffusion processes within the films. Factors contributing to exciton transport can include film morphology encompassing nanotube orientation, connectivity, and interaction geometry. Such factors are often defined by nanotube surface structures that are not yet well understood. Here, we present the results of a combined pump-probe and photoluminescence imaging study of polyfluorene (PFO)-wrapped (6,5) and (7,5) SWCNTs that provide additional insight into the role played by polymer structures in defining exciton transport. Pump-probe measurements suggest exciton transport occurs over larger length scales in films composed of PFO-wrapped (7,5) SWCNTs, compared to those prepared from PFO-bpy-wrapped (6,5) SWCNTs. To explore the role the difference in polymer structure may play as a possible origin of differing transport behaviors, we performed a photoluminescence imaging study of individual polymer-wrapped (6,5) and (7,5) SWCNTs. The PFO-bpy-wrapped (6,5) SWCNTs showed more uniform intensity distributions along their lengths, in contrast to the PFO-wrapped (7,5) SWCNTs, which showed irregular, discontinuous intensity distributions. These differences likely originate from differences in surface coverage and suggest the PFO wrapping on (7,5) nanotubes produces a more open surface structure than is available with the PFO-bpy wrapping of (6,5) nanotubes. The open structure likely leads to improved intertube coupling that enhances exciton transport within the (7,5) films, consistent with the results of our pump-probe measurements.

  4. Tailoring room temperature photoluminescence of antireflective silicon nanofacets

    SciTech Connect

    Basu, Tanmoy; Kumar, M.; Ghatak, J.; Som, T.; Kanjilal, A.; Sahoo, P. K.

    2014-09-21

    In this paper, a fluence-dependent antireflection performance is presented from ion-beam fabricated nanofaceted-Si surfaces. It is also demonstrated that these nanofacets are capable of producing room temperature ultra-violet and blue photoluminescence which can be attributed to inter-band transitions of the localized excitonic states of different Si-O bonds at the Si/SiO{sub x} interface. Time-resolved photoluminescence measurements further confirm defect-induced radiative emission from the surface of silicon nanofacets. It is observed that the spectral characteristics remain unchanged, except an enhancement in the photoluminescence intensity with increasing ion-fluence. The increase in photoluminescence intensity by orders of magnitude stronger than that of a planar Si substrate is due to higher absorption of incident photons by nanofaceted structures.

  5. Surface plasmon enhanced photoluminescence from copper nanoparticles: Influence of temperature

    SciTech Connect

    Yeshchenko, Oleg A. Bondarchuk, Illya S.; Losytskyy, Mykhaylo Yu.

    2014-08-07

    Anomalous temperature dependence of surface plasmon enhanced photoluminescence from copper nanoparticles embedded in a silica host matrix has been observed. The quantum yield of photoluminescence increases as the temperature increases. The key role of such an effect is the interplay between the surface plasmon resonance and the interband transitions in the copper nanoparticles occurring at change of the temperature. Namely, the increase of temperature leads to the red shift of the resonance. The shift leads to increase of the spectral overlap of the resonance with photoluminescence band of copper as well as to the decrease of plasmon damping caused by interband transitions. Such mechanisms lead to the increase of surface plasmon enhancement factor and, consequently, to increase of the quantum yield of the photoluminescence.

  6. Photoluminescence properties of silica aerogel/porous silicon nanocomposites

    NASA Astrophysics Data System (ADS)

    Karlash, A. Yu; Zakharko, Yu E.; Skryshevsky, V. A.; Tsiganova, A. I.; Kuznetsov, G. V.

    2010-08-01

    The luminescent properties of nanocomposite pellets based on silica aerogel and porous Si powder are studied depending on the ratio of chemical compounds. The photoluminescence of nanocomposites is characterized by a red-orange band related to silicon nanoparticles and a blue-green band related to silica aerogel with close values of decay time and activation energy. Remarkable tuning of nanocomposites' photoluminescence spectra in the RGB region is established allowing their use as promising phosphor materials for light-emitting diodes. The outgoing spectra of pellet photoluminescence are guided by the chemical composition ratio, porous Si and silica aerogel technology, and the storage time in ambient atmosphere. It was shown that using the silica aerogel as a dielectric matrix considerably increases the stability of photoluminescence yield of silicon nanoparticles.

  7. Photoluminescence imaging of solitary dopant sites in covalently doped single-wall carbon nanotubes

    SciTech Connect

    Hartmann, Nicolai F.; Yalcin, Sibel Ebru; Adamska, Lyudmyla; Haroz, Erik H.; Ma, Xuedan; Tretiak, Sergei; Htoon, Han; Doorn, Stephen K.

    2015-11-11

    Covalent dopants in semiconducting single wall carbon nanotubes (SWCNTs) are becoming important as routes for introducing new photoluminescent emitting states with potential for enhanced quantum yields, new functionality, and as species capable of near-IR room-temperature single photon emission. The origin and behavior of the dopant-induced emission is thus important to understand as a key requirement for successful room-T photonics and optoelectronics applications. Here, we use direct correlated two-color photoluminescence imaging to probe how the interplay between the SWCNT bright E11 exciton and solitary dopant sites yields the dopant-induced emission for three different dopant species: oxygen, 4-methoxybenzene, and 4-bromobenzene. We introduce a route to control dopant functionalization to a low level as a means for introducing spatially well-separated solitary dopant sites. Resolution of emission from solitary dopant sites and correlation to their impact on E11 emission allows confirmation of dopants as trapping sites for localization of E11 excitons following their diffusive transport to the dopant site. Imaging of the dopant emission also reveals photoluminescence intermittency (blinking), with blinking dynamics being dependent on the specific dopant. Density functional theory calculations were performed to evaluate the stability of dopants and delineate the possible mechanisms of blinking. Furthermore, theoretical modeling suggests that the trapping of free charges in the potential well created by permanent dipoles introduced by dopant atoms/groups is likely responsible for the blinking, with the strongest effects being predicted and observed for oxygen-doped SWCNTs.

  8. Photoluminescence imaging of solitary dopant sites in covalently doped single-wall carbon nanotubes

    DOE PAGES

    Hartmann, Nicolai F.; Yalcin, Sibel Ebru; Adamska, Lyudmyla; ...

    2015-11-11

    Covalent dopants in semiconducting single wall carbon nanotubes (SWCNTs) are becoming important as routes for introducing new photoluminescent emitting states with potential for enhanced quantum yields, new functionality, and as species capable of near-IR room-temperature single photon emission. The origin and behavior of the dopant-induced emission is thus important to understand as a key requirement for successful room-T photonics and optoelectronics applications. Here, we use direct correlated two-color photoluminescence imaging to probe how the interplay between the SWCNT bright E11 exciton and solitary dopant sites yields the dopant-induced emission for three different dopant species: oxygen, 4-methoxybenzene, and 4-bromobenzene. We introducemore » a route to control dopant functionalization to a low level as a means for introducing spatially well-separated solitary dopant sites. Resolution of emission from solitary dopant sites and correlation to their impact on E11 emission allows confirmation of dopants as trapping sites for localization of E11 excitons following their diffusive transport to the dopant site. Imaging of the dopant emission also reveals photoluminescence intermittency (blinking), with blinking dynamics being dependent on the specific dopant. Density functional theory calculations were performed to evaluate the stability of dopants and delineate the possible mechanisms of blinking. Furthermore, theoretical modeling suggests that the trapping of free charges in the potential well created by permanent dipoles introduced by dopant atoms/groups is likely responsible for the blinking, with the strongest effects being predicted and observed for oxygen-doped SWCNTs.« less

  9. Resonance excitation of photoluminescence in sodium uranyl acetate crystals

    NASA Astrophysics Data System (ADS)

    Gorelik, V. S.; Korshunov, V. M.; Voinov, Yu. P.

    2016-12-01

    The photoluminescence spectra of sodium uranyl acetate polycrystals are recorded under excitation by different sources (semiconductor light-emitting diodes, cw lasers, and repetitively pulsed lasers). The excitation wavelengths fall into the absorption band of this solid, which makes it possible to record photoluminescence beginning from an extremely small volume of the material (10-10 cm3) at exposures of 10-3 s.

  10. Using quantum dot photoluminescence for load detection

    NASA Astrophysics Data System (ADS)

    Moebius, M.; Martin, J.; Hartwig, M.; Baumann, R. R.; Otto, T.; Gessner, T.

    2016-08-01

    We propose a novel concept for an integrable and flexible sensor capable to visualize mechanical impacts on lightweight structures by quenching the photoluminescence (PL) of CdSe quantum dots. Considering the requirements such as visibility, storage time and high optical contrast of PL quenching with low power consumption, we have investigated a symmetrical and an asymmetrical layer stack consisting of semiconductor organic N,N,N',N'-Tetrakis(3-methylphenyl)-3,3'-dimethylbenzidine (HMTPD) and CdSe quantum dots with elongated CdS shell. Time-resolved series of PL spectra from layer stacks with applied voltages of different polarity and simultaneous observation of power consumption have shown that a variety of mechanisms such as photo-induced charge separation and charge injection, cause PL quenching. However, mechanisms such as screening of external field as well as Auger-assisted charge ejection is working contrary to that. Investigations regarding the influence of illumination revealed that the positive biased asymmetrical layer stack is the preferred sensor configuration, due to a charge carrier injection at voltages of 10 V without the need of coincident illumination.

  11. Ionodeterioration of the silicon nanocrystal photoluminescence

    SciTech Connect

    Demarche, J.; Terwagne, G.; Barba, D.; Ross, G. G.

    2011-12-01

    The photoluminescence (PL) of Si nanocrystals (Si-nc) embedded in fused silica has been investigated under simultaneous excitations by laser and low energy proton beam. Ionodegradation of the sample, characterized by a rapid decrease and a spectral blueshift of the PL emission has been observed. These effects are associated with the creation of non-radiative centers in the Si-nc. Micro-Raman spectroscopy analysis shows that the proton beam has not changed the average size of Si-nc, but has disturbed a fraction of Si-Si bonds inside the Si-nc, which is consistent with both simulations and direct measurements. A post-annealing performed at 400 deg. C for 1 h can restore the structural properties of the Si-nc, but only a part of their nominal PL emission intensity is recovered. Characterization of the damage induced by low energy proton irradiation reported in this paper makes the use of light ion beams relevant for the experimental investigation of nanostructured systems, such as ionoluminescence measurements.

  12. Understanding ligand-centred photoluminescence through flexibility and bonding of anthraquinone inorganic-organic frameworks

    SciTech Connect

    Furman, Joshua D; Burwood, Ryan P; Tang, Min; Mikhailovsky, Alexander A; Cheetham, Anthony K

    2011-11-17

    Five novel inorganic-organic framework compounds containing the organic chromophore ligand anthraquinone-2,3-dicarboxylic acid (abbreviated H2AQDC) and calcium (CaAQDC), zinc (ZnAQDC), cadmium (CdAQDC), manganese (MnAQDC), and nickel (NiAQDC), respectively, have been synthesized. The photoluminescence of these materials is only visible at low temperatures and this behaviour has been evaluated in terms of ligand rigidity. It is proposed that the 2,3 position bonding sites result in luminescence-quenching ligand motion, as supported by X-ray diffraction and temperature-dependent luminescence studies.

  13. Synthesis and Photoluminescence Properties of Li2SrSiO4 Activated with Dy3+ and Sm3+

    NASA Astrophysics Data System (ADS)

    Erdoğmuş, E.

    2015-01-01

    Li2SrSiO4:M (M: Dy3+ and Sm3+) phosphors were synthesized by the conventional solid state reaction. The synthesized materials were characterized by powder XRD. The emission and excitation spectra of these phosphors were measured at room temperature with a spectrofluorometer. The first phosphor, Li2SrSiO4:Dy3+, emits at 479, 573, and 666 nm upon 351 nm excitation. The second phosphor, Li2SrSiO4:Sm3+, emits at 561-571, 594, 647-655, and 703-713 nm upon 399 nm excitation. Also, the dependence of the photoluminescence properties of both phosphors on boric acid concentration was investigated. The results showed that boric acid was effective in improving the photoluminescence intensity of both phosphors.

  14. Photoluminescence and doping mechanism of theranostic Eu3+/Fe3+ dual-doped hydroxyapatite nanoparticles

    PubMed Central

    Chen, Min-Hua; Yoshioka, Tomohiko; Ikoma, Toshiyuki; Hanagata, Nobutaka; Lin, Feng-Huei; Tanaka, Junzo

    2014-01-01

    Theranostic nanoparticles currently have been regarded as an emerging concept of ‘personalized medicine’ with diagnostic and therapeutic dual-functions. Eu3+ doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca2+ with Fe3+ in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu3+ and Fe3+ doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu3+ and Fe3+ doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu3+ and Fe3+, and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications. PMID:27877717

  15. The use of multiple probe molecules for the study of the acid-base properties of aluminium hydroxyfluoride having the hexagonal tungsten bronze structure: FTIR and [36Cl] radiotracer studies.

    PubMed

    Dambournet, Damien; Leclerc, Hervé; Vimont, Alexandre; Lavalley, Jean-Claude; Nickkho-Amiry, Mahmood; Daturi, Marco; Winfield, John M

    2009-03-07

    The combination of several probe molecules has enabled the construction of a detailed picture of the surface of aluminium hydroxyl fluoride, AlF(2.6)(OH)(0.4), which has the hexagonal tungsten bronze (HTB) structure. Using pyridine as a probe leads to features at 1628 cm(-1), ascribed to very strong Lewis acid sites, and at 1620-1623 cm(-1), which is the result of several different types of Lewis sites. This heterogeneity is indicated also from CO adsorption at 100 K; the presence of five different types of Lewis site is deduced and is suggested to arise from the hydroxylated environment. Brønsted acid sites of medium strength are indicated by adsorption of lutidine and CO. Adsorption of lutidine occurs at OH groups, which are exposed at the surface and CO reveals that these OH groups have a single environment that can be correlated with their specific location inside the bulk, assuming that the surface OH group may reflect the bulk OH periodicity. A correlation between the data obtained from CO and pyridine molecules has been established using co-adsorption experiments, which also highlight the inductive effect produced by pyridine. Adsorption of the strong Brønsted acid, anhydrous hydrogen chloride, detected by monitoring the beta(-) emission of [(36)Cl]-HCl at the surface, indicates that surface hydroxyl groups can behave also as a Brønsted base and that H(2)O-HCl interactions, either within the hexagonal channels or at the surface are possible. Finally, the formation of strongly bound H(36)Cl as a result of the room temperature dehydrochlorination of [(36)Cl]-labelled tert-butyl chloride provides additional evidence that HTB-AlF(2.6)(OH)(0.4) can behave as a Lewis acid.

  16. A nucleic acid probe labeled with desmethyl thiazole orange: a new type of hybridization-sensitive fluorescent oligonucleotide for live-cell RNA imaging.

    PubMed

    Okamoto, Akimitsu; Sugizaki, Kaori; Yuki, Mizue; Yanagisawa, Hiroyuki; Ikeda, Shuji; Sueoka, Takuma; Hayashi, Gosuke; Wang, Dan Ohtan

    2013-01-14

    A new fluorescent nucleotide with desmethyl thiazole orange dyes, D'(505), has been developed for expansion of the function of fluorescent probes for live-cell RNA imaging. The nucleoside unit of D'(505) for DNA autosynthesis was soluble in organic solvents, which made the preparation of nucleoside units and the reactions in the cycles of DNA synthesis more efficient. The dyes of D'(505)-containing oligodeoxynucleotide were protonated below pH 7 and the oligodeoxynucleotide exhibited hybridization-sensitive fluorescence emission through the control of excitonic interactions of the dyes of D'(505). The simplified procedure and effective hybridization-sensitive fluorescence emission produced multicolored hybridization-sensitive fluorescent probes, which were useful for live-cell RNA imaging. The acceptor-bleaching method gave us information on RNA in a specific cell among many living cells.

  17. Photoluminescence intensity enhancement in SWNT aqueous suspensions due to reducing agent doping: Influence of adsorbed biopolymer

    NASA Astrophysics Data System (ADS)

    Kurnosov, N. V.; Leontiev, V. S.; Linnik, A. S.; Lytvyn, O. S.; Karachevtsev, V. A.

    2014-06-01

    The influence of biopolymer wrapped around nanotube on the enhancement of the semiconducting single-walled carbon nanotube (SWNT) photoluminescence (PL) in aqueous suspension which increases due to the reducing agent dithiothreitol (DTT) doping effect was revealed. The greatest enhancement of PL was observed for SWNTs covered with double- or single stranded DNA (above 170%) and DTT weak influence was revealed for SWNTs:polyC suspension (∼45%). The magnitude of the PL enhancement depends also on nanotube chirality and sample aging. The behavior of PL from SWNTs covered with various polymers is explained by the different biopolymers ordering on the nanotube surface. The ordered polymer conformation on the nanotube weakens the reducing agent doping effect. The method of reducing agent doping of nanotube:biopolymer aqueous suspension can serve as a sensitive luminescent probe of the biopolymer ordering on the carbon nanotube and can be used to increase the sensitivity of luminescent biosensors.

  18. Measuring long-range carrier diffusion across multiple grains in polycrystalline semiconductors by photoluminescence imaging.

    PubMed

    Alberi, K; Fluegel, B; Moutinho, H; Dhere, R G; Li, J V; Mascarenhas, A

    2013-01-01

    Thin-film polycrystalline semiconductors are currently at the forefront of inexpensive large-area solar cell and integrated circuit technologies because of their reduced processing and substrate selection constraints. Understanding the extent to which structural and electronic defects influence carrier transport in these materials is critical to controlling the optoelectronic properties, yet many measurement techniques are only capable of indirectly probing their effects. Here we apply a novel photoluminescence imaging technique to directly observe the low temperature diffusion of photocarriers through and across defect states in polycrystalline CdTe thin films. Our measurements show that an inhomogeneous distribution of localized defect states mediates long-range hole transport across multiple grain boundaries to locations exceeding 10 μm from the point of photogeneration. These results provide new insight into the key role deep trap states have in low temperature carrier transport in polycrystalline CdTe by revealing their propensity to act as networks for hopping conduction.

  19. Measuring long-range carrier diffusion across multiple grains in polycrystalline semiconductors by photoluminescence imaging

    NASA Astrophysics Data System (ADS)

    Alberi, K.; Fluegel, B.; Moutinho, H.; Dhere, R. G.; Li, J. V.; Mascarenhas, A.

    2013-10-01

    Thin-film polycrystalline semiconductors are currently at the forefront of inexpensive large-area solar cell and integrated circuit technologies because of their reduced processing and substrate selection constraints. Understanding the extent to which structural and electronic defects influence carrier transport in these materials is critical to controlling the optoelectronic properties, yet many measurement techniques are only capable of indirectly probing their effects. Here we apply a novel photoluminescence imaging technique to directly observe the low temperature diffusion of photocarriers through and across defect states in polycrystalline CdTe thin films. Our measurements show that an inhomogeneous distribution of localized defect states mediates long-range hole transport across multiple grain boundaries to locations exceeding 10 μm from the point of photogeneration. These results provide new insight into the key role deep trap states have in low temperature carrier transport in polycrystalline CdTe by revealing their propensity to act as networks for hopping conduction.

  20. Determination of captopril using selective photoluminescence enhancement of 2-mercaptopropionic modified CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Khan, Sarzamin; Lima, Alex A.; Larrudé, Dunieskys G.; Romani, Eric C.; Aucelio, Ricardo Q.

    2014-04-01

    A photoluminescent probe for the determination of captopril is proposed based on the enhancement of luminescence from 2-mercaptopropionic modified CdTe quantum dots (2-MPA-CdTe QDs). Under optimum conditions, the calibration model (the Langmuir binding isotherm) was linear up to 4.8 × 10-4 mol L-1 with equilibrium binding constant of 3.2 × 104 L mol-1 and limit of detection (xb + 3 sb) of 2.7 × 10-7 mol L-1 (59 ng mL-1). The approach was tested in the determination of captopril in pharmaceutical formulations and the results were in agreement with the ones obtained using reference method. The possible mechanism of interaction is also investigated by Raman and electronic absorption spectroscopy and dynamic light scattering.

  1. Convenient synthesis of stable silver quantum dots with enhanced photoluminescence emission by laser fragmentation

    NASA Astrophysics Data System (ADS)

    Shuang, Li; Ming, Chen

    2016-04-01

    A new strategy for the facile synthesis of very stable and mono-dispersed silver (Ag) quantum dots (QDs) is developed by laser fragmentation of bulk Ag in water using polysorbate 80 as a dispersing and stabilizing agent. The surfactant plays an important role in the formation of size-controlled Ag nano-structures. The Ag QDs have excellent photo-stability of ∼500 h and enhanced photoluminescence (PL) at 510 nm. This has significant implications for selective and ultrasensitive PL probes. Based on laser fragmentation in the biocompatible surfactant solution, our results have opened up a novel paradigm to obtain stable metal QDs directly from bulk targets. This is a breakthrough in the toxicity problems that arise from standard chemical fabrication. Project supported by the National Natural Science Foundation of China (Grant Nos. 11575102, 11105085, 11275116, and 11375108) and the Fundamental Research Funds of Shandong University, China (Grant No. 2015JC007).

  2. Measuring long-range carrier diffusion across multiple grains in polycrystalline semiconductors by photoluminescence imaging

    PubMed Central

    Alberi, K.; Fluegel, B.; Moutinho, H.; Dhere, R. G.; Li, J. V.; Mascarenhas, A.

    2013-01-01

    Thin-film polycrystalline semiconductors are currently at the forefront of inexpensive large-area solar cell and integrated circuit technologies because of their reduced processing and substrate selection constraints. Understanding the extent to which structural and electronic defects influence carrier transport in these materials is critical to controlling the optoelectronic properties, yet many measurement techniques are only capable of indirectly probing their effects. Here we apply a novel photoluminescence imaging technique to directly observe the low temperature diffusion of photocarriers through and across defect states in polycrystalline CdTe thin films. Our measurements show that an inhomogeneous distribution of localized defect states mediates long-range hole transport across multiple grain boundaries to locations exceeding 10 μm from the point of photogeneration. These results provide new insight into the key role deep trap states have in low temperature carrier transport in polycrystalline CdTe by revealing their propensity to act as networks for hopping conduction. PMID:24158163

  3. Deep ultraviolet photoluminescence of Tm-doped AlGaN alloys

    SciTech Connect

    Nepal, N.; Zavada, J. M.; Lee, D. S.; Steckl, A. J.; Sedhain, A.; Lin, J. Y.; Jiang, H. X.

    2009-03-16

    The ultraviolet (UV) photoluminescence (PL) properties of Tm-doped Al{sub x}Ga{sub 1-x}N (0.39{<=}x{<=}1) alloys grown by solid-source molecular beam epitaxy were probed using above-bandgap excitation from a laser source at 197 nm. The PL spectra show dominant UV emissions at 298 and 358 nm only for samples with x=1 and 0.81. Temperature dependence of the PL intensities of these emission lines reveals exciton binding energies of 150 and 57 meV, respectively. The quenching of these UV emissions appears related to the thermal activation of the excitons bound to rare-earth structured isovalent (RESI) charge traps, which transfer excitonic energy to Tm{sup 3+} ions resulting in the UV emissions. A model of the RESI trap levels in AlGaN alloys is presented.

  4. Please do not disturb: Destruction of chromatin structure by supravital nucleic acid probes revealed by a novel assay of DNA-histone interaction

    PubMed Central

    Wlodkowic, Donald; Darzynkiewicz, Zbigniew

    2008-01-01

    The biomarkers designed to be used supravitally are expected to have minimal effect on structure and function of the cell. Unfortunately nearly all fluorochromes developed to probe live cells interact in undesired way with cellular constituents and affect functional pathways. Herein we comment on potential applications of diverse DNA binding probes in view of the recent article by Wojcik & Dobrucki on DRAQ 5 and SYTO 17. The approach used by these authors to assess DNA-histone interactions using the cells having histones tagged with fluorescent proteins offers a valuable tool to study mechanism of action of antitumor drugs targeting DNA. While the effect of many intercalating drugs may be similar to that of DRAQ5, it may be of particular interest to observe the effects induced by intra-strand and inter-strand DNA crosslinking drugs, alkylating agents, histone deacetylase inhibitors or even anti-metabolites. The cells having histones tagged with fluorescent proteins thus may serve as biomarkers to probe mechanism of action of drugs targeting DNA or affecting chromatin structure. In fact, because such gross chromatin changes as revealed by dissociation and segregation of histones from DNA are most likely incompatible with long-term cell survival, the methodology may be applied for rapid screening of investigational antitumor agents. PMID:18671237

  5. Facile route to highly photoluminescent carbon nanodots for ion detection, pH sensors and bioimaging

    NASA Astrophysics Data System (ADS)

    Shen, Chen; Sun, Yupeng; Wang, Jing; Lu, Yun

    2014-07-01

    Carbon nanodots (CDs) of uniform size were prepared simply by the hydrothermal decomposition of folic acid (FA) precursor at various reaction temperatures. The CDs formed via dehydration of FA at 260 °C contributed the strongest photoluminescence (PL) signal and the highest quantum yield at about 68%, without assistance of any passivation agent. The effects of preparation conditions on PL behavior of CDs have been investigated in detail, and the quantum yield of the CDs was found to be associated strongly with sample crystallinity. Moreover, because the obtained CDs also exhibited high luminescence stability, abundant surface functional groups and good biocompatibility, there are many promising applications in printing ink, ion detection, pH sensors and cell imaging.Carbon nanodots (CDs) of uniform size were prepared simply by the hydrothermal decomposition of folic acid (FA) precursor at various reaction temperatures. The CDs formed via dehydration of FA at 260 °C contributed the strongest photoluminescence (PL) signal and the highest quantum yield at about 68%, without assistance of any passivation agent. The effects of preparation conditions on PL behavior of CDs have been investigated in detail, and the quantum yield of the CDs was found to be associated strongly with sample crystallinity. Moreover, because the obtained CDs also exhibited high luminescence stability, abundant surface functional groups and good biocompatibility, there are many promising applications in printing ink, ion detection, pH sensors and cell imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02154a

  6. Effect of Silica Nanoparticles on the Photoluminescence Properties of BCNO Phosphor

    NASA Astrophysics Data System (ADS)

    Nuryadin, Bebeh W.; Faryuni, Irfana Diah; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal, Khairurrijal

    2011-12-01

    Effect of additional silica nanoparticles on the photoluminescence (PL) performance of boron carbon oxy-nitride (BCNO) phosphor was investigated. As a precursor, boric acid and urea were used as boron and nitrogen sources, respectively. The carbon sources was polyethylene glycol (PEG) with average molecule weight 20000 g/mol.. Precursor solutions were prepared by mixing these raw materials in pure water, followed by stirring to achieve homogeneous solutions. In this precursor, silica nanoparticles were added at various mass ratio from 0 to 7 %wt in the solution. The precursors were then heated at 750 °C for 60 min in a ceramic crucible under atmospheric pressure. The photoluminescence (PL) spectrum that characterized by spectrophotometer showed a single, distinct, and broad emission band varied from blue to near red color, depend on the PEG, boric acid and urea ratio in the precursor. The addition of silica nanoparticles caused the increasing of PL intensity as well as the shifting of peak wavelength of PL spectrum. The peak shifting of PL was affected by the concentration of silica nanoparticles that added into the precursor. We believe that the BCNO-silica composite phosphor becomes a promising material for the phosphor conversion-based white light-emitting diodes.

  7. Hydrogen atoms in acetylsalicylic acid (Aspirin): the librating methyl group and probing the potential well in the hydrogen-bonded dimer

    NASA Astrophysics Data System (ADS)

    Wilson, Chick C.

    2001-02-01

    The structure of acetylsalicylic acid (2-(acetoyloxy)benzoic acid; Aspirin) has been studied by variable temperature single crystal neutron diffraction. The usual large torsional librational motion of the terminal methyl group is observed and its temperature dependence analysed using a simple model for the potential, yielding the force constant and barrier height for this motion. In addition, asymmetry of the scattering density of the proton involved in the hydrogen bond forming the carboxylic acid dimer motif is observed at temperatures above 200 K. This asymmetry is discussed in terms of its possible implications for the shape of the hydrogen bonding potential well.

  8. Origin of the Avalanche-Like Photoluminescence from Metallic Nanowires

    PubMed Central

    Ma, Zongwei; Yu, Ying; Shen, Shaoxin; Dai, Hongwei; Yao, Linhua; Han, Yibo; Wang, Xia; Han, Jun-Bo; Li, Liang

    2016-01-01

    Surface plasmonic systems provide extremely efficient ways to modulate light-matter interaction in photon emission, light harvesting, energy conversion and transferring, etc. Various surface plasmon enhanced luminescent behaviors have been observed and investigated in these systems. But the origin of an avalanche-like photoluminescence, which was firstly reported in 2007 from Au and subsequently from Ag nanowire arrays/monomers, is still not clear. Here we show, based on systematic investigations including the excitation power/time related photoluminescent measurements as well as calculations, that this avalanche-like photoluminescence is in fact a result of surface plasmon assisted thermal radiation. Nearly all of the related observations could be perfectly interpreted with this concept. Our finding is crucial for understanding the surface plasmon mediated thermal and photoemission behaviors in plasmonic structures, which is of great importance in designing functional plasmonic devices. PMID:26728439

  9. Steady-state photoluminescent excitation characterization of semiconductor carrier recombination

    SciTech Connect

    Bhosale, J. S.; Moore, J. E.; Wang, X.; Bermel, P.; Lundstrom, M. S.

    2016-01-15

    Photoluminescence excitation spectroscopy is a contactless characterization technique that can provide valuable information about the surface and bulk recombination parameters of a semiconductor device, distinct from other sorts of photoluminescent measurements. For this technique, a temperature-tuned light emitting diode (LED) has several advantages over other light sources. The large radiation density offered by LEDs from near-infrared to ultraviolet region at a low cost enables efficient and fast photoluminescence measurements. A simple and inexpensive LED-based setup facilitates measurement of surface recombination velocity and bulk Shockley-Read-Hall lifetime, which are key parameters to assess device performance. Under the right conditions, this technique can also provide a contactless way to measure the external quantum efficiency of a solar cell.

  10. Steady-state photoluminescent excitation characterization of semiconductor carrier recombination.

    PubMed

    Bhosale, J S; Moore, J E; Wang, X; Bermel, P; Lundstrom, M S

    2016-01-01

    Photoluminescence excitation spectroscopy is a contactless characterization technique that can provide valuable information about the surface and bulk recombination parameters of a semiconductor device, distinct from other sorts of photoluminescent measurements. For this technique, a temperature-tuned light emitting diode (LED) has several advantages over other light sources. The large radiation density offered by LEDs from near-infrared to ultraviolet region at a low cost enables efficient and fast photoluminescence measurements. A simple and inexpensive LED-based setup facilitates measurement of surface recombination velocity and bulk Shockley-Read-Hall lifetime, which are key parameters to assess device performance. Under the right conditions, this technique can also provide a contactless way to measure the external quantum efficiency of a solar cell.

  11. Microcavity effects in the photoluminescence of hydrogenated amorphous silicon nitride

    NASA Astrophysics Data System (ADS)

    Serpenguzel, Ali; Aydinli, Atilla; Bek, Alpan

    1998-07-01

    Fabry-Perot microcavities are used for the alteration of photoluminescence in hydrogenated amorphous silicon nitride grown with and without ammonia. The photoluminescence is red-near-infrared for the samples grown without ammonia, and blue-green for the samples grown with ammonia. In the Fabry- Perot microcavities, the amplitude of the photoluminescence is enhanced, while its linewidth is reduced with respect to the bulk hydrogenated amorphous silicon nitride. The microcavity was realized by a metallic back mirror and a hydrogenated amorphous silicon nitride--air or a metallic front mirror. The transmittance, reflectance, and absorbance spectra were also measured and calculated. The calculated spectra agree well with the experimental spectra. The hydrogenated amorphous silicon nitride microcavity has potential for becoming a versatile silicon based optoelectronic device such as a color flat panel display, a resonant cavity enhanced light emitting diode, or a laser.

  12. Photoluminescence quantum yield of PbS nanocrystals in colloidal suspensions

    SciTech Connect

    Greben, M.; Fucikova, A.; Valenta, J.

    2015-04-14

    The absolute photoluminescence (PL) quantum yield (QY) of oleic acid-capped colloidal PbS quantum dots (QDs) in toluene is thoroughly investigated as function of QD size, concentration, excitation photon energy, and conditions of storage. We observed anomalous decrease of QY with decreasing concentration for highly diluted suspensions. The ligand desorption and QD-oxidation are demonstrated to be responsible for this phenomenon. Excess of oleic acid in suspensions makes the QY values concentration-independent over the entire reabsorption-free range. The PL emission is shown to be dominated by surface-related recombinations with some contribution from QD-core transitions. We demonstrate that QD colloidal suspension stability improves with increasing the concentration and size of PbS QDs.

  13. 3-Aminophenylboronic acid-functionalized CuInS2 quantum dots as a near-infrared fluorescence probe for the detection of dicyandiamide.

    PubMed

    Liu, Siyu; Pang, Shu; Huang, Hui; Su, Xingguang

    2014-11-21

    In this paper, a simple and highly selective method for the determination of dicyandiamide (DCD) was developed based on the fluorescence quenching of functionalized CuInS2 quantum dots (QDs). Water-soluble CuInS2 QDs, capped by mercaptopropionic acid, were directly synthesized in aqueous solution and then covalently linked to 3-aminophenylboronic acid molecules to form the 3-aminophenylboronic acid-functionalized CuInS2 QDs (F-CuInS2 QDs) that had a fairly symmetric fluorescence emission centered at 736 nm. Based on the cyclization of the guanidine group of DCD with 2,3-butanedione and 3-aminophenylboronic acid, the fluorescence of the F-CuInS2 QDs is quenched by DCD in the presence of 2,3-butanedione. This method effectively distinguishes DCD from other amino acids and nitrogen pollutants, such as melamine, in real milk samples. Under optimum conditions, there was a good linear relationship between the fluorescence intensity of F-CuInS2 QDs and the concentration of DCD in the range of 2.0 × 10(-6) to 2.0 × 10(-3) mol L(-1), with a detection limit of 0.6 μmol L(-1).

  14. Photoluminescence limiting of colloidal PbS quantum dots

    NASA Astrophysics Data System (ADS)

    Ullrich, B.; Xi, H.; Wang, J. S.

    2016-02-01

    The exposure of colloidal 2 nm PbS quantum dots to growing continuous wave laser excitation at 532 nm increases the photoluminescence intensity with the square root of the optical stimulus. The results herein in conjunction with previous findings [B. Ullrich and H. Xi, Opt. Lett. 38, 4698 (2013)] advocate the square root trend to be the general limiting function for photo-carrier transport and emission of optically excited nano-sized materials. We further show that the excitation of one electron-hole pair per quantum dot defines the saturation threshold for photoluminescence intensity and dynamic band filling.

  15. Low-temperature photoluminescence studies of mercuric-iodide photodetectors

    SciTech Connect

    James, R.B. ); Bao, X.J. ); Schlesinger, T.E.; Markakis, J.M.; Cheng, A.Y.; Ortale, C.

    1989-09-15

    Mercuric-iodide (HgI{sub 2} ) photodetectors with sputtered indium-tin-oxide (ITO) entrance electrodes were studied using low-temperature photoluminescence spectroscopy. The photoluminescence spectrum obtained on each photodetector was found to differ for points beneath the ITO contact and points adjacent to it, indicating that the contact fabrication process introduces new carrier traps and radiative recombination centers within the ITO-HgI{sub 2} interfacial region. In particular, a new broad band was observed in the spectra taken from points beneath the ITO electrode. Photocurrent-versus-position measurements showed that the intensity of this broad band was enhanced in regions having relatively poor photoresponse.

  16. Optical enhancement of photoluminescence with colloidal quantum dots

    NASA Astrophysics Data System (ADS)

    Abraham, Gabrielle; French, David A.; Bajwa, Pooja; Heyes, Colin D.; Herzog, Joseph B.

    2015-08-01

    This work investigates colloidal, semiconductor Cadmium Selenide (CdSe) QDs with optical spectroscopy measurements. A custom-built microscope has been used for photoluminescence spectroscopy and has collected images, videos, and spectra of samples to study the effects of substrates, sample density, uniformity, and QD aging with time. This set up will be used to detect single to a few molecules, shown by fluorescent intermittency, or QD blinking. Differences in the spectrum will be noted as related to the age of samples, the density of the quantum dots, and the concentration of samples. Further experiments include the potential plasmonic enhancement of QD photoluminescence by gold nanoparticles or nanostructures.

  17. Photoluminescent carbon quantum dots as a directly film-forming phosphor towards white LEDs

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Feng, Xiaoting; Zhang, Yi; Yan, Lingpeng; Yang, Yongzhen; Liu, Xuguang

    2016-04-01

    Photoluminescent organosilane-functionalized carbon quantum dots (CQDs), 3.0-3.5 nm in diameter, were synthesized via a facile hydrothermal method using citric acid monohydrate as a precursor and N-(3-(trimethoxysilyl) propyl) ethylenediamine as a coordinating and passivation agent. The optical properties of the as-obtained CQDs were investigated in detail. The CQD aqueous solution emits bright blue-white light under ultraviolet (UV) illumination with a quantum yield of 57.3% and high red-green-blue (RGB) spectral composition of 60.1%, and in particular the CQDs exhibit excitation-independent photoluminescence. The CQDs have a narrow size distribution around 3.1 nm and good film-forming ability through simple heat-treatment. By virtue of these excellent optical characteristics and good film-forming ability, a white light-emitting device (LED) was fabricated by combining a UV-LED chip with a single CQD phosphor film, which exhibited cool white light with a CIE coordinate of (0.31, 0.36), a color rendering index of 84 and a correlated color temperature of 6282 K. In addition, the white LED exhibits good optical stability under various working currents and for different working time intervals. Moreover, the interaction between the carbogenic core and surface groups was discussed using the DMol3 program based on density functional theory. This research suggests the great potential of CQDs for solid-state lighting systems and reveals the effect of the surface state on the photoluminescent mechanism of CQDs.

  18. Photoluminescent carbon quantum dots as a directly film-forming phosphor towards white LEDs.

    PubMed

    Zhang, Feng; Feng, Xiaoting; Zhang, Yi; Yan, Lingpeng; Yang, Yongzhen; Liu, Xuguang

    2016-04-28

    Photoluminescent organosilane-functionalized carbon quantum dots (CQDs), 3.0-3.5 nm in diameter, were synthesized via a facile hydrothermal method using citric acid monohydrate as a precursor and N-(3-(trimethoxysilyl) propyl) ethylenediamine as a coordinating and passivation agent. The optical properties of the as-obtained CQDs were investigated in detail. The CQD aqueous solution emits bright blue-white light under ultraviolet (UV) illumination with a quantum yield of 57.3% and high red-green-blue (RGB) spectral composition of 60.1%, and in particular the CQDs exhibit excitation-independent photoluminescence. The CQDs have a narrow size distribution around 3.1 nm and good film-forming ability through simple heat-treatment. By virtue of these excellent optical characteristics and good film-forming ability, a white light-emitting device (LED) was fabricated by combining a UV-LED chip with a single CQD phosphor film, which exhibited cool white light with a CIE coordinate of (0.31, 0.36), a color rendering index of 84 and a correlated color temperature of 6282 K. In addition, the white LED exhibits good optical stability under various working currents and for different working time intervals. Moreover, the interaction between the carbogenic core and surface groups was discussed using the DMol(3) program based on density functional theory. This research suggests the great potential of CQDs for solid-state lighting systems and reveals the effect of the surface state on the photoluminescent mechanism of CQDs.

  19. Probing the segmental mobility and energy of the active zones of a protein chain (aspartic acid protease) by a coarse-grained bond-fluctuation Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Pandey, Ras; Farmer, Barry

    2008-03-01

    A protein chain such as aspartic acid protease is described by a specific sequence of 99 residues each with its own specific characteristics. In a coarse-grained description, the backbone of a protein chain is described by nodes tethered together by peptide bonds where each node (the amino acid group) is characterized by molecular weight and hydrophobicity. A well-developed and somewhat mature computational modeling tool for the polymer chain such as the bond-fluctuation model is used to study such a specific protein chain with its constitutive amino groups and their sequence. The relative magnitude of hydrophobicity is used to develop appropriate interaction potentials for these amino acid groups in explicit solvent. The Metropolis algorithm is used to move each node and solvent constituent. Local energy and mobility of each amino group are analyzed along with global energy, mobility, and conformation of the protein chain. Effect of the solvent interaction and its concentration on these quantities will be presented.

  20. A probe on the intermolecular forces in diisopropyl ether-n-butyric acid mixture by dielectric, FTIR studies and quantum chemical calculations.

    PubMed

    Arivazhagan, G; Shanmugam, R; Elangovan, A

    2013-03-15

    The results of FTIR spectral measurement on equimolar diisopropyl ether-butyric acid binary mixture and quantum chemical calculations on the complex molecule have been presented. Dielectric studies have been carried out on the binary mixture over the entire composition range and at four different temperatures 303 K, 308 K, 313 K and 318 K. n-Butyric acid seems to prefer less polar ether to interact with it. It appears that the usual interpretation of variation of static dielectric constant and positive deviation of excess permittivity from ideal mixture behavior needs to be relooked.

  1. Non-amplified Quantitative Detection of Nucleic Acid Sequences Using a Gold Nanoparticle Probe Set and Field-Emission Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Hyonchol Kim,; Atsushi Kira,; Kenji Yasuda,

    2010-06-01

    For the precise detection of the number of expressed biomarkers at the single-cell level, we have developed a method of quantifying and specifying target DNA fragments by using a set of gold nanoparticles as labels and field-emission scanning electron microscopy (FE-SEM) to measure the number and sizes of gold nanoparticles attached to target samples. One or more target DNAs on a substrate were labeled with a set of different-sized gold nanoparticle probes having complementary sequences to different target candidates. The type and number of the target DNAs having a specific sequence were identified by counting the attached nanoparticles of a specific size in FE-SEM images. The results evaluated using a DNA microarray showed high specificity and sensitivity, and a linear correlation between the number of attached particles and the target DNA concentration, indicating the feasibility of quantitative detection in the femtomolar to nanomolar concentration range.

  2. Use of H2S to Probe the Active Sites in FeNC Catalysts for the Oxygen Reduction Reaction (ORR) in Acidic Media

    SciTech Connect

    Singh, Deepika; Mamtani, Kuldeep; Bruening, Christopher R.; Miller, Jeffrey T.; Ozkan, Umit S.

    2014-10-01

    H2S has been used as a probe molecule both in an “in situ” poisoning experiment and in intermediate-temperature heat-treatment steps during and after the preparation of FeNC catalysts in an attempt to analyze its effect on their ORR activity. The heat treatments were employed either on the ball-milled precursor of FeNC or after the Ar-NH3 high temperature heat treatments. ORR activity of the H2S-treated catalysts was seen to be significantly lower than the sulfur-free catalysts, whether the sulfur exposure was during a half-cell testing, or as an intermediate-temperature exposure to H2S. The incorporation of sulfur species and interaction of Fe with sulfur were confirmed by characterization using XPS, EXAFS, TPO, and TPD. This study provides crucial evidence regarding differences in active sites in FeNC versus nitrogen-containing carbon nanostructured (CNx) catalysts.

  3. Nine New Fluorescent Probes

    NASA Astrophysics Data System (ADS)

    Lin, Tsung-I.; Jovanovic, Misa V.; Dowben, Robert M.

    1989-06-01

    Absorption and fluorescence spectroscopic studies are reported here for nine new fluorescent probes recently synthesized in our laboratories: four pyrene derivatives with substituents of (i) 1,3-diacetoxy-6,8-dichlorosulfonyl, (ii) 1,3-dihydroxy-6,8-disodiumsulfonate, (iii) 1,3-disodiumsulfonate, and (iv) l-ethoxy-3,6,8-trisodiumsulfonate groups, and five [7-julolidino] coumarin derivatives with substituents of (v) 3-carboxylate-4-methyl, (vi) 3- methylcarboxylate, (vii) 3-acetate-4-methyl, (viii) 3-propionate-4-methyl, and (ix) 3-sulfonate-4-methyl groups. Pyrene compounds i and ii and coumarin compounds v and vi exhibit interesting absorbance and fluorescence properties: their absorption maxima are red shifted compared to the parent compound to the blue-green region, and the band width broadens considerably. All four blue-absorbing dyes fluoresce intensely in the green region, and the two pyrene compounds emit at such long wavelengths without formation of excimers. The fluorescence properties of these compounds are quite environment-sensitive: considerable spectral shifts and fluorescence intensity changes have been observed in the pH range from 3 to 10 and in a wide variety of polar and hydrophobic solvents with vastly different dielectric constants. The high extinction and fluorescence quantum yield of these probes make them ideal fluorescent labeling reagents for proteins, antibodies, nucleic acids, and cellular organelles. The pH and hydrophobicity-dependent fluorescence changes can be utilized as optical pH and/or hydrophobicity indicators for mapping environmental difference in various cellular components in a single cell. Since all nine probes absorb in the UV, but emit at different wavelengths in the visible, these two groups of compounds offer an advantage of utilizing a single monochromatic light source (e.g., a nitrogen laser) to achieve multi-wavelength detection for flow cytometry application. As a first step to explore potential application in

  4. Constrained photophysics of partially and fully encapsulated charge transfer probe (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester inside cyclodextrin nano-cavities: Evidence of cyclodextrins cavity dependent complex stoichiometry

    NASA Astrophysics Data System (ADS)

    Ghosh, Shalini; Jana, Sankar; Guchhait, Nikhil

    2011-12-01

    The polarity sensitive intra-molecular charge transfer (ICT) emission from (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester (MAPAME) is found to show distinct changes once introduced into the nano-cavities of cyclodextrins in aqueous environment. Movement of the molecule from the more polar aqueous environment to the less polar, hydrophobic cyclodextrin interior is marked by the blue shift of the CT emission band with simultaneous fluorescence intensity enhancement. The emission spectral changes on complexation with the α- and β-CD show different stoichiometries as observed from the Benesi-Hildebrand plots. Fluorescence anisotropy and lifetime measurements were performed to probe the different behaviors of MAPAME in aqueous α- and β-CD solutions.

  5. THE APPLICATION OF PEPTIDE NUCLEIC ACID PROBES FOR RAPID DETECTION AND ENUMERATION OF EUBACTERIA, STAPHYLOCOCCUS AUREUS AND PSEUDOMONAS AERUGINOSA IN RECREATIONAL BEACHES OF S. FLORIDA. (R828830)

    EPA Science Inventory

    A novel chemiluminescent in situ hybridization technique using peptide nucleic acids (PNA) was adapted for the detection of bacteria in beach sand and recreational waters in South Florida. The simultaneous detection and enumeration of eubacteria and the novel indicators, S...

  6. What Is a pH Probe Study?

    MedlinePlus

    What is a pH Probe Study ? What is pH a probe study? M easuring the pH in the esophagus helps determine whether or not acid is coming up from the stomach. A pH probe study is usually done in patients where ...

  7. Excitation correlation photoluminescence in the presence of Shockley-Read-Hall recombination

    SciTech Connect

    Borgwardt, M.; Sippel, P.; Eichberger, R.; Semtsiv, M. P.; Masselink, W. T.; Schwarzburg, K.

    2015-06-07

    Excitation correlation photoluminescence (ECPL) measurements are often analyzed in the approximation of a cross correlation of charge carrier populations generated by the two delayed pulses. In semiconductors, this approach is valid for a linear non-radiative recombination path, but not for a non-linear recombination rate as in the general Shockley-Read-Hall recombination scenario. Here, the evolution of the ECPL signal was studied for deep trap recombination following Shockley-Read-Hall statistics. Analytic solutions can be obtained for a fast minority trapping regime and steady state recombination. For the steady state case, our results show that the quadratic radiative term plays only a minor role, and that the shape of the measured signal is mostly determined by the non-linearity of the recombination itself. We find that measurements with unbalanced intense pump and probe pulses can directly provide information about the dominant non-radiative recombination mechanism. The signal traces follow the charge carrier concentrations, despite the complex origins of the signal, thus showing that ECPL can be applied to study charge carrier dynamics in semiconductors without requiring elaborate calculations. The model is compared with measurements on a reference sample with alternating layers of InGaAs/InAlAs that were additionally cross-checked with time resolved optical pump terahertz probe measurements and found to be in excellent agreement.

  8. A new general model for predicting melting thermodynamics of complementary and mismatched B-form duplexes containing locked nucleic acids: application to probe design for digital PCR detection of somatic mutations.

    PubMed

    Hughesman, Curtis; Fakhfakh, Kareem; Bidshahri, Roza; Lund, H Louise; Haynes, Charles

    2015-02-17

    Advances in real-time polymerase chain reaction (PCR), as well as the emergence of digital PCR (dPCR) and useful modified nucleotide chemistries, including locked nucleic acids (LNAs), have created the potential to improve and expand clinical applications of PCR through their ability to better quantify and differentiate amplification products, but fully realizing this potential will require robust methods for designing dual-labeled hydrolysis probes and predicting their hybridization thermodynamics as a function of their sequence, chemistry, and template complementarity. We present here a nearest-neighbor thermodynamic model that accurately predicts the melting thermodynamics of a short oligonucleotide duplexed either to its perfect complement or to a template containing mismatched base pairs. The model may be applied to pure-DNA duplexes or to duplexes for which one strand contains any number and pattern of LNA substitutions. Perturbations to duplex stability arising from mismatched DNA:DNA or LNA:DNA base pairs are treated at the Gibbs energy level to maintain statistical significance in the regressed model parameters. This approach, when combined with the model's accounting of the temperature dependencies of the melting enthalpy and entropy, permits accurate prediction of T(m) values for pure-DNA homoduplexes or LNA-substituted heteroduplexes containing one or two independent mismatched base pairs. Terms accounting for changes in solution conditions and terminal addition of fluorescent dyes and quenchers are then introduced so that the model may be used to accurately predict and thereby tailor the T(m) of a pure-DNA or LNA-substituted hydrolysis probe when duplexed either to its perfect-match template or to a template harboring a noncomplementary base. The model, which builds on classic nearest-neighbor thermodynamics, should therefore be of use to clinicians and biologists who require probes that distinguish and quantify two closely related alleles in either a

  9. Acid-base interactions and secondary structures of poly-L-lysine probed by 15N and 13C solid state NMR and Ab initio model calculations.

    PubMed

    Dos, Alexandra; Schimming, Volkmar; Tosoni, Sergio; Limbach, Hans-Heinrich

    2008-12-11

    The interactions of the 15N-labeled amino groups of dry solid poly-L-lysine (PLL) with various halogen and oxygen acids HX and the relation to the secondary structure have been studied using solid-state 15N and 13C CPMAS NMR spectroscopy (CP = cross polarization and MAS = magic angle spinning). For comparison, 15N NMR spectra of an aqueous solution of PLL were measured as a function of pH. In order to understand the effects of protonation and hydration on the 15N chemical shifts of the amino groups, DFT and chemical shielding calculations were performed on isolated methylamine-acid complexes and on periodic halide clusters of the type (CH3NH3(+)X(-))n. The combined experimental and computational results reveal low-field shifts of the amino nitrogens upon interaction with the oxygen acids HX = HF, H2SO4, CH3COOH, (CH3)2POOH, H3PO4, HNO3, and internal carbamic acid formed by reaction of the amino groups with gaseous CO2. Evidence is obtained that only hydrogen-bonded species of the type (Lys-NH2***H-X)n are formed in the absence of water. 15N chemical shifts are maximum when H is located in the hydrogen bond center and then decrease again upon full protonation, as found for aqueous solution at low pH. By contrast, halogen acids interact in a different way. They form internal salts of the type (Lys-NH3(+)X(-))n via the interaction of many acid-base pairs. This salt formation is possible only in the beta-sheet conformation. By contrast, the formation of hydrogen-bonded complexes can occur both in beta-sheet domains as well as in alpha-helical domains. The 15N chemical shifts of the protonated ammonium groups increase when the size of the interacting halogen anions is increased from chloride to iodide and when the number of the interacting anions is increased. Thus, the observed high-field 15N shift of ammonium groups upon hydration is the consequence of replacing interacting halogen atoms by oxygen atoms.

  10. Thermally enhanced photoluminescence for heat harvesting in photovoltaics.

    PubMed

    Manor, Assaf; Kruger, Nimrod; Sabapathy, Tamilarasan; Rotschild, Carmel

    2016-10-20

    The maximal Shockley-Queisser efficiency limit of 41% for single-junction photovoltaics is primarily caused by heat dissipation following energetic-photon absorption. Solar-thermophotovoltaics concepts attempt to harvest this heat loss, but the required high temperatures (T>2,000 K) hinder device realization. Conversely, we have recently demonstrated how thermally enhanced photoluminescence is an efficient optical heat-pump that operates in comparably low temperatures. Here we theoretically and experimentally demonstrate such a thermally enhanced photoluminescence based solar-energy converter. Here heat is harvested by a low bandgap photoluminescent absorber that emits thermally enhanced photoluminescence towards a higher bandgap photovoltaic cell, resulting in a maximum theoretical efficiency of 70% at a temperature of 1,140 K. We experimentally demonstrate the key feature of sub-bandgap photon thermal upconversion with an efficiency of 1.4% at only 600 K. Experiments on white light excitation of a tailored Cr:Nd:Yb glass absorber suggest that conversion efficiencies as high as 48% at 1,500 K are in reach.

  11. Thermally enhanced photoluminescence for heat harvesting in photovoltaics

    NASA Astrophysics Data System (ADS)

    Manor, Assaf; Kruger, Nimrod; Sabapathy, Tamilarasan; Rotschild, Carmel

    2016-10-01

    The maximal Shockley-Queisser efficiency limit of 41% for single-junction photovoltaics is primarily caused by heat dissipation following energetic-photon absorption. Solar-thermophotovoltaics concepts attempt to harvest this heat loss, but the required high temperatures (T>2,000 K) hinder device realization. Conversely, we have recently demonstrated how thermally enhanced photoluminescence is an efficient optical heat-pump that operates in comparably low temperatures. Here we theoretically and experimentally demonstrate such a thermally enhanced photoluminescence based solar-energy converter. Here heat is harvested by a low bandgap photoluminescent absorber that emits thermally enhanced photoluminescence towards a higher bandgap photovoltaic cell, resulting in a maximum theoretical efficiency of 70% at a temperature of 1,140 K. We experimentally demonstrate the key feature of sub-bandgap photon thermal upconversion with an efficiency of 1.4% at only 600 K. Experiments on white light excitation of a tailored Cr:Nd:Yb glass absorber suggest that conversion efficiencies as high as 48% at 1,500 K are in reach.

  12. Photoluminescence properties of polystyrene-hosted fluorophore thin films

    NASA Astrophysics Data System (ADS)

    Chakraborty, Subha; Harris, Katherine; Huang, Mengbing

    2016-12-01

    We report on a photo-luminescence study of four different fluorophores: Coumarin 6, 2,5-Diphenyloxazole (PPO), 1,4-Bis(5-phenyl-2-oxazolyl)benzene (POPOP) and Para-terpehnyl (PTP), doped in a polystyrene-based thin film. All of the samples are prepared by spin coating from a non-polar polymer solution at various concentrations. Their emission spectra and transient properties are characterized by photoluminescence measurements. Red-shifts in the emission spectra are observed for all four types of fluorophores as their concentration increases. We explain this phenomenon based on concentration dependence of solvatochromic effects and the results show good agreement with existing literature. We also show that the singlet-singlet annihilation processes are possibly a prevalent mechanism in the high concentration regime that affects the steady state and transient emission characteristics of the fluors. With the exception of PTP, photoluminescence quenching occurs as the fluorophore concentration in the polymer is increased. Rate equations for excited state decay mechanisms are analysed by considering different radiative and non-radiative energy transfer mechanisms. The results show consistency with our experimental observations. PTP shows the best photoluminescence results as an efficient fluor in the thin film, whereas PPO shows the strongest concentration dependent quenching and an anomalous lifetime distribution.

  13. Dynamics of four-photon photoluminescence in gold nanoantennas.

    PubMed

    Biagioni, Paolo; Brida, Daniele; Huang, Jer-Shing; Kern, Johannes; Duò, Lamberto; Hecht, Bert; Finazzi, Marco; Cerullo, Giulio

    2012-06-13

    Two-pulse correlation is employed to investigate the temporal dynamics of both two-photon photoluminescence (2PPL) and four-photon photoluminescence (4PPL) in resonant and nonresonant nanoantennas excited at a wavelength of 800 nm. Both 2PPL and 4PPL data are consistent with the same two-step model already established for 2PPL, implying that the first excitation step in 4PPL is a three-photon sp → sp direct interband transition. Considering energy and parity conservation, we also explain why 4PPL behavior is favored over, for example, three- and five-photon photoluminescence in the power range below the damage threshold of our antennas. Since sizable 4PPL requires larger peak intensities of the local field, we are able to select either 2PPL or 4PPL in the same gold nanoantennas by choosing a suitable laser pulse duration. We thus provide a first consistent model for the understanding of multiphoton photoluminescence generation in gold nanoantennas, opening new perspectives for applications ranging from the characterization of plasmonic resonances to biomedical imaging.

  14. Thermally enhanced photoluminescence for heat harvesting in photovoltaics

    PubMed Central

    Manor, Assaf; Kruger, Nimrod; Sabapathy, Tamilarasan; Rotschild, Carmel

    2016-01-01

    The maximal Shockley–Queisser efficiency limit of 41% for single-junction photovoltaics is primarily caused by heat dissipation following energetic-photon absorption. Solar-thermophotovoltaics concepts attempt to harvest this heat loss, but the required high temperatures (T>2,000 K) hinder device realization. Conversely, we have recently demonstrated how thermally enhanced photoluminescence is an efficient optical heat-pump that operates in comparably low temperatures. Here we theoretically and experimentally demonstrate such a thermally enhanced photoluminescence based solar-energy converter. Here heat is harvested by a low bandgap photoluminescent absorber that emits thermally enhanced photoluminescence towards a higher bandgap photovoltaic cell, resulting in a maximum theoretical efficiency of 70% at a temperature of 1,140 K. We experimentally demonstrate the key feature of sub-bandgap photon thermal upconversion with an efficiency of 1.4% at only 600 K. Experiments on white light excitation of a tailored Cr:Nd:Yb glass absorber suggest that conversion efficiencies as high as 48% at 1,500 K are in reach. PMID:27762271

  15. Photoluminescence of spray pyrolysis deposited ZnO nanorods

    PubMed Central

    2011-01-01

    Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods. PACS: 78.55.Et, 81.15.Rs, 61.46.Km PMID:21711895

  16. Fractals of graphene quantum dots in photoluminescence of shungite

    NASA Astrophysics Data System (ADS)

    Razbirin, B. S.; Rozhkova, N. N.; Sheka, E. F.; Nelson, D. K.; Starukhin, A. N.

    2014-05-01

    Viewing shungite as loosely packed fractal nets of graphene-based (reduced graphene oxide, rGO) quantum dots (GQDs), we consider photoluminescence of the latter as a convincing proof of the structural concept as well as of the GQD attribution to individual rGO fragments. We study emission from shungite GQDs for colloidal dispersions in water, carbon tetrachloride, and toluene at both room and low temperatures. As expected, the photoluminescence of the GQD aqueous dispersions is quite similar to that of synthetic GQDs of the rGO origin. The morphological study of shungite dispersions shows a steady trend of GQDs to form fractals and to drastically change the colloid fractal structure caused by the solvent exchange. Spectral study reveals a dual character of the emitting centers: individual GQDs are responsible for the spectra position while the fractal structure of GQD colloids ensures high broadening of the spectra due to structural inhomogeneity, thus causing a peculiar dependence of the photoluminescence spectra on the excitation wavelength. For the first time, photoluminescence spectra of individual GQDs were observed in frozen toluene dispersions, which paves the way for a theoretical treatment of the GQD photonics.

  17. Photoluminescence of spray pyrolysis deposited ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Kärber, Erki; Raadik, Taavi; Dedova, Tatjana; Krustok, Jüri; Mere, Arvo; Mikli, Valdek; Krunks, Malle

    2011-04-01

    Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods. PACS: 78.55.Et, 81.15.Rs, 61.46.Km

  18. Photoluminescence of spray pyrolysis deposited ZnO nanorods.

    PubMed

    Kärber, Erki; Raadik, Taavi; Dedova, Tatjana; Krustok, Jüri; Mere, Arvo; Mikli, Valdek; Krunks, Malle

    2011-04-21

    Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.PACS: 78.55.Et, 81.15.Rs, 61.46.Km.

  19. Photoluminescence of Zn-implanted GaN

    NASA Technical Reports Server (NTRS)

    Pankove, J. I.; Hutchby, J. A.

    1974-01-01

    The photoluminescence spectrum of Zn-implanted GaN peaks at 2.87 eV at room temperature. The emission efficiency decreases linearly with the logarithm of the Zn concentration in the range from 1 x 10 to the 18th to 20 x 10 to the 18th Zn/cu cm.

  20. Luminescent Photoelectrochemical Cells. 6. Spatial Aspects of the Photoluminescence and Electroluminescence of Cadmium Selenide Electrodes.

    DTIC Science & Technology

    1981-10-06

    NO. 8 Luminescent Photoelectrochemical Cells. 6. Spatial Aspects of the Photoluminescence and Electroluminescence of Cadmium Selenide Electrodes by...Photoelectrochemistry; photoluminescence; electroluminescence; cadmium selenide electrodes 20. ABSTRACT (Continue. on reverse aide flnocosee7 and...REPORT A PERIOD COVERED Luminescent Photoelectrochemical Cells. 6.1 1 Spatial Aspects of the Photoluminescence and Elect roluminescence of Cadmium

  1. Quantification of ultra-trace molybdenum using 4-amino-5-hydroxynaphthalene-2,7-disulfonic acid monosodium salt as a chromogenic probe.

    PubMed

    Nagaraja, Padmarajaiah; Krishna, Honnur; Shivakumar, Anantharaman; Paulas, Anthonydas Robert; Rangappa, Dinesh

    2011-04-15

    A simple, ultrasensitive, nonextractive spectrophotometric method has been developed for the assay of Mo(VI), which involves Mo-catalyzed oxidation of 4-amino-5-hydroxynaphthalene-2,7-disulfonic acid monosodium salt (AHNDSA) by H(2)O(2) in acetic acid/sodium acetate buffer yielding an intense pink colored product with λ(max) of 540 nm. Beer's law is obeyed in the range of 10-240 ng/ml with molar absorptivity of 3.0137×10(5)L mol(-1)cm(-1). The LOD and LOQ were found to be 0.7696 and 2.565 ng/ml, respectively. The applicability of the method toward water and biological samples was tested and statistically compared with a reference method.

  2. A DFT study of the acid-base properties of anatase TiO2 and tetragonal ZrO2 by adsorption of CO and CO2 probe molecules

    NASA Astrophysics Data System (ADS)

    Chen, Hsin-Yi Tiffany; Tosoni, Sergio; Pacchioni, Gianfranco

    2016-10-01

    We have performed a comparative study of the acid-base characteristics of the surfaces of anatase TiO2 and tetragonal ZrO2. To this end we performed DFT + U calculations on CO and CO2 probe molecules adsorbed both on terraces and steps of the two oxides. For titania, CO adsorption results in a moderate adsorption energy (about - 0.3 eV) and in a positive shift of the Csbnd O stretching frequency (about + 40 cm- 1), typical of Lewis acid sites, with no clear difference in the acidity between terraces or steps. For zirconia we found a similar CO binding energy as for titania, and a CO vibrational shift that depends on the location of the Zr cation: negligible on terraces, similar to TiO2 on steps. We conclude that the acidic properties are similar in the two oxide surfaces. Things are different for CO2 adsorption. On titania the interaction is weak and surface carbonates compete with physisorbed CO2, indicating a weak basic character. On the contrary, on zirconia three types of stable carbonates have been identified. Their vibrational frequencies are consistent with IR measurements reported in the literature. The most stable species forms on steps of the t-ZrO2 surface and consists of a CO32 - unit which lies flat on the surface with the O atoms pointing towards three Zr ions. The species forms spontaneously by extraction of a lattice oxygen by an incoming CO2 molecule. The different reactivity points towards a much more pronounced basic character of zirconia compared to titania, at least if measured by CO2 adsorption.

  3. A dinuclear ruthenium(II) complex as turn-on luminescent probe for hypochlorous acid and its application for in vivo imaging

    PubMed Central

    Liu, Zonglun; Gao, Kuo; Wang, Beng; Yan, Hui; Xing, Panfei; Zhong, Chongmin; Xu, Yongqian; Li, Hongjuan; Chen, Jianxin; Wang, Wei; Sun, Shiguo

    2016-01-01

    A dinuclear ruthenium(II) complex Ruazo was designed and synthesized, in which oxidative cyclization of the azo and o-amino group was employed for the detection of hypochlorous acid (HClO) in aqueous solution. The non-emissive Ruazo formed highly luminescent triazole-ruthenium(II) complex in presence of HClO and successfully imaged HClO in living cell and living mouse. PMID:27356618

  4. Photoaffinity analogues of methotrexate as folate antagonist binding probes. 1. Photoaffinity labeling of murine L1210 dihydrofolate reductase and amino acid sequence of the binding region

    SciTech Connect

    Price, E.M.; Smith, P.L.; Klein, T.E.; Freisheim, J.H.

    1987-07-28

    N/sup ..cap alpha../-(4-Amino-4-deoxy-10-methylpteroyl)-N/sup epsilon/-(4-azido-5-(/sup 125/I)iodosalicylyl)-L-lysine, a photoaffinity analogue of methotrexate, is only 2-fold less potent than methotrexate in the inhibition of murine L1210 dihydrofolate reductase. Irradiation of the enzyme in the presence of an equimolar concentration of the /sup 125/I-labeled analogue ultimately leads to an 8% incorporation of the photoprobe. A 100-fold molar excess of methotrexate essentially blocks this incorporation. Cyanogen bromide digestion of the labeled enzyme, followed by high-pressure liquid chromatography purification of the generated peptides, indicates that greater than 85% of the total radioactivity is incorporated into a single cyanogen bromide peptide. Sequence analysis revealed this peptide to be residues 53-111, with a majority of the radioactivity centered around residues 63-65 (Lys-Asn-Arg). These data demonstrate that the photoaffinity analogue specifically binds to dihydrofolate reductase and covalently modifies the enzyme following irradiation and is therefore a photolabeling agent useful for probing the inhibitor binding domain of the enzyme.

  5. Hydrothermal synthesis, crystal structures and photoluminescence properties of mixed europium-yttrium organic frameworks

    SciTech Connect

    Han Yinfeng; Fu Lianshe; Mafra, Luis; Shi, Fa-Nian

    2012-02-15

    Three mixed europium-yttrium organic frameworks: Eu{sub 2-x}Y{sub x}(Mel)(H{sub 2}O){sub 6} (Mel=mellitic acid or benzene-1,2,3,4,5,6-hexacarboxylic acid, x=0.38 1, 0.74 2, and 0.86 3) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu{sup 3+} lifetime becomes longer in these MOFs than those of the Eu analog. - Graphical abstract: Three mixed europium and yttrium organic frameworks: Eu{sub 2-x}Y{sub x}(Mel)(H{sub 2}O){sub 6} (Mel=mellitic acid) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu{sup 3+} lifetime becomes longer in these MOFs than those of the Eu analog. Highlights: Black-Right-Pointing-Pointer Three (4, 8)-flu topological mixed Eu and Y MOFs were synthesized under mild conditions. Black-Right-Pointing-Pointer Metal ratios were refined by the single crystal data consistent with the EDS analysis. Black-Right-Pointing-Pointer Mixed Eu and Y MOFs show longer lifetime and higher quantum efficiency than the Eu analog. Black-Right-Pointing-Pointer Adding inert lanthanide into luminescent MOFs enlarges the field of luminescent MOFs.

  6. Hydrodynamic ultrasonic probe

    DOEpatents

    Day, Robert A.; Conti, Armond E.

    1980-01-01

    An improved probe for in-service ultrasonic inspection of long lengths of a workpiece, such as small diameter tubing from the interior. The improved probe utilizes a conventional transducer or transducers configured to inspect the tubing for flaws and/or wall thickness variations. The probe utilizes a hydraulic technique, in place of the conventional mechanical guides or bushings, which allows the probe to move rectilinearly or rotationally while preventing cocking thereof in the tube and provides damping vibration of the probe. The probe thus has lower friction and higher inspection speed than presently known probes.

  7. Probe tip heating assembly

    SciTech Connect

    Schmitz, Roger William; Oh, Yunje

    2016-10-25

    A heating assembly configured for use in mechanical testing at a scale of microns or less. The heating assembly includes a probe tip assembly configured for coupling with a transducer of the mechanical testing system. The probe tip assembly includes a probe tip heater system having a heating element, a probe tip coupled with the probe tip heater system, and a heater socket assembly. The heater socket assembly, in one example, includes a yoke and a heater interface that form a socket within the heater socket assembly. The probe tip heater system, coupled with the probe tip, is slidably received and clamped within the socket.

  8. DAPI: a DNA-specific fluorescent probe.

    PubMed

    Kapuscinski, J

    1995-09-01

    DAPI (4',6-diamidino-2-phenylindole) is a DNA-specific probe which forms a fluorescent complex by attaching in the minor grove of A-T rich sequences of DNA. It also forms nonfluorescent intercalative complexes with double-stranded nucleic acids. The physicochemical properties of the dye and its complexes with nucleic acids and history of the development of this dye as a biological stain are described. The application of DAPI as a DNA-specific probe for flow cytometry, chromosome staining, DNA visualization and quantitation in histochemistry and biochemistry is reviewed. The mechanisms of DAPI-nucleic acid complex formation including minor groove binding, intercalation and condensation are discussed.

  9. A general sensing strategy for detection of Fe3+ by using amino acid-modified graphene quantum dots as fluorescent probe

    NASA Astrophysics Data System (ADS)

    Ma, Qi; Song, Jinping; Wang, Shangzhi; Yang, Jie; Guo, Yong; Dong, Chuan

    2016-12-01

    Amino acid-modified graphene quantum dots (GQDs) were synthesized through acylation and amination reactions. The as-synthesized GQDs were characterized by high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-vis absorption and fluorescence spectroscopy. A general sensing strategy for detection of Fe3+ was successfully developed. The detection limit can reach as low as 50 nM. Moreover, the proposed sensing system was successfully employed to detect Fe3+ in real water sample, and satisfactory results were obtained. This work will open up new avenues to develop potential applications of GQDs materials in environmental monitoring.

  10. Probing the molecular and electronic structure of norhipposudoric and hipposudoric acids from the red sweat of Hippopotamus amphibius: a DFT investigation.

    PubMed

    Galasso, Vinicio; Pichierri, Fabio

    2009-03-19

    Molecular structure and tautomeric/conformational preferences of norhipposudoric and hipposudoric acids, the recently isolated pigments of the Hippopotamus amphibius' sweat, were investigated using the density functional theory (DFT) PBE0 formalism. Among a large variety of possible structures, two similar keto-enol tautomer/conformers are nearly isoenergetic and markedly more stable than the others both in the gas phase and aqueous solution. The bulk solvent effect was accounted for with the polarizable continuum model (PCM). A distinctive structural feature is the strong intramolecular hydrogen bonding in the keto-enol O-H...O bridge, as shown by analysis of the atoms-in-molecules topological properties of the electron density. To elucidate the claimed strong acidity of these pigments, the site-specific microscopic dissociation constants were also calculated using the cluster-continuum model, a hybrid approach based on inclusion of explicit solvent molecules and solvation of the cluster by the dielectric continuum. Notably, the first deprotonation should occur predominantly from the enolic group with a remarkably low pk(i) value. This factor could play an important role in the potent antibiotic activity of the pigments. The absorption spectra of the undissociated and dissociated compounds in aqueous solution were interpreted with time-dependent DFT/PCM calculations. The pi-pi* diquinoid excitations, mainly occurring in the fluorenoid nucleus, are the major contributors to the color and strong absorption bands in the UVA and UVB regions, which are closely related to the efficient sunscreen activity exerted by the pigments.

  11. A Novel Electrochemical Sensor for Probing Doxepin Created on a Glassy Carbon Electrode Modified with Poly(4-Amino- benzoic Acid)/Multi-Walled Carbon Nanotubes Composite Film

    PubMed Central

    Xu, Xiao-Li; Huang, Fei; Zhou, Guo-Liang; Zhang, Song; Kong, Ji-Lie

    2010-01-01

    A novel electrochemical sensor for sensitive detection of doxepin was prepared, which was based on a glassy carbon electrode modified with poly(4-aminobenzoic acid)/multi-walled carbon nanotubes composite film [poly(4-ABA)/MWNTs/GCE]. The sensor was characterized by scanning electron microscopy and electrochemical methods. It was observed that poly(4-ABA)/MWNTs/GCE showed excellent preconcentration function and electrocatalytic activities towards doxepin. Under the selected conditions, the anodic peak current was linear to the logarithm of doxepin concentration in the range from 1.0 × 10−9 to 1.0 × 10−6 M, and the detection limit obtained was 1.0 × 10−10 M. The poly(4-ABA)/MWNTs/GCE was successfully applied in the measurement of doxepin in commercial pharmaceutical formulations, and the analytical accuracy was confirmed by comparison with a conventional ultraviolet spectrophotometry assay. PMID:22163661

  12. Stealth CD44-targeted hyaluronic acid supramolecular nanoassemblies for doxorubicin delivery: probing the effect of uncovalent pegylation degree on cellular uptake and blood long circulation.

    PubMed

    Han, Xiaopeng; Li, Zhenbao; Sun, Jin; Luo, Cong; Li, Lin; Liu, Yuhai; Du, Yuqian; Qiu, Shuhong; Ai, Xiaoyu; Wu, Chunnuan; Lian, He; He, Zhonggui

    2015-01-10

    Stealth active targeting nanoparticles (NPs) usually include two types of ligand sites: ligand anchored on distal ends of the polyethylene glycol (PEG) and ligand buried under pegylated layer. The latter typical case is hyaluronic acid (HA)-based NPs; however, there is little information available for the latter NPs about effect of the optimal density of surface PEG coating on the blood circulation time, cellular uptake and in vivo anticancer activity. Thus, in this study, in order to optimize the anticancer effects of HA-based NPs, we focus on how uncovalent pegylation degree modulates blood circulation time and cellular uptake of HA-based NPs. We firstly designed a new double-hydrophilic copolymer by conjugating HP-β-cyclodextrin with HA, and this carrier was further pegylated with adamantyl-peg (ADA-PEG) to form inclusion complex HA-HPCD/ADA-PEG, termed as HCPs. The supramolecular nanoassemblies were fabricated by host-guest and polar interactions between HCPs and doxorubicin (Dox), with vitamin E succinate (VES) being a nanobridge. Despite the active recognition between HA and CD44 receptor, the cellular uptake and targeting efficiency of HA-NPs decreased with the increasing peg density, demonstrating HA was partly buried by high density peg coating. However, the high density of peg coating was beneficial to long circulation time, tumor biodistribution and anticancer activity in vivo. NPs with 5% peg coating had the optimal cellular targeting efficiency in vitro and anticancer effects in vivo. The findings suggest that balancing long circulation property and cellular uptake is important to achieve the optimal antitumor efficacy for pegylated HA-based NPs, and that PEG coating densities cannot be extended beyond a certain density for shielding effect without compromising the efficacy of hyaluronic acid targeted delivery.

  13. Vaterite-type YBO 3:Eu 3+ crystals: hydrothermal synthesis, morphology and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Lin, Jun

    2004-10-01

    Vaterite-type YBO 3:Eu 3+ crystals with interesting flower and hedgehog fungus-like structures composed of nanosheets were obtained by controlled crystallization of Y 2O 3 and Eu 2O 3 in H 3BO 3 solutions under acidic hydrothermal (HT) conditions. Nanosheets of uniform thicknesses were formed by preferential crystal growth along the (1 0 0) crystallographic plane and specific three-dimensional structures were further developed through a homocentric growth mechanism. Optical emission measurements showed that the HT-grown nanosheet crystals exhibited a higher ratio of the emitted red-to-orange light ratio than crystals grown from solid-state reactions. The photoluminescence intensity and emission lifetimes were also studied as a function of the Eu 3+ dopant concentration and the HT synthesis temperature. The effect of some additives: a chelating ligand, a surfactant and a polymer, on the YBO 3:Eu 3+ crystals morphology was also investigated.

  14. CdSe nanocrystals: controlled growth and diameter-dependent photoluminescence

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Yang, Ping; Chen, Hsueh Shin; Huang, Baibiao; Shen, Jianxing

    2014-02-01

    Phosphonic and carboxylic acids were used as capping agents to fabricate CdSe nanocrystals (NCs) through organic synthesis, leading to a controlled growth of the NCs with adjustable morphologies from dots to rods. The binding energies and steric hindrance of ligands dramatically affected the growth kinetics of CdSe NCs, and therefore the resulting geometry of NCs. The detailed investigations of ligand effect on the growth of NCs and an efficient control over the NCs morphology were presented. CdSe nanorods (NRs) with various aspect ratios were created for studying relation between the diameter of NRs and photoluminescence (PL). Consequently, a synergic use of PL spectra and transmission electron microscopy images allowed us to systematically investigate the relationship between morphology and PL properties of as-prepared CdSe rods. The PL properties of CdSe NRs were finally found to be strongly diameter dependent and weakly related to their lengths.

  15. Towards enhanced ligand-centred photoluminescence in inorganic-organic frameworks for solid state lighting

    SciTech Connect

    Furman, Joshua D; Melot, Brent C; Teat, Simon J; Mikhailovsky, Alexander A; Cheetham, Anthony K

    2011-11-17

    Three novel inorganic-organic framework compounds containing the organic chromophore ligand 9-fluorenone-2,7-dicarboxylic acid (abbreviated H2FDC) and barium (BaFDC), cadmium (CdFDC) and manganese (MnFDC), respectively, have been synthesized and evaluated for their use as phosphor materials for solid state lighting and other applications. The results are compared with two earlier reported structures containing the same ligand with calcium (CaFDC) and strontium (SrFDC). The barium- and cadmium-containing compounds both show blue excited, yellow photoluminescence, while the manganese structure does not. The trends in luminescent efficiency for the Ba, Cd, Ca, and Sr derivatives are discussed in relation to crystallographic, optical, and low-temperature specific heat considerations.

  16. 'Green'-synthesized near-infrared PbS quantum dots with silica-PEG dual-layer coating: ultrastable and biocompatible optical probes for in vivo animal imaging.

    PubMed

    Wang, D; Qian, J; Cai, F; He, S; Han, S; Mu, Y

    2012-06-22

    In this paper, PbS semiconductor quantum dots (QDs) with near-infrared (NIR) photoluminescence were synthesized in oleic acid and paraffin liquid mixture by using an easily handled and 'green' approach. Surface functionalization of the QDs was accomplished with a silica and polyethylene glycol (PEG) phospholipid dual-layer coating and the excellent chemical stability of the nanoparticles is demonstrated. We then successfully applied the ultrastable PbS QDs to in vivo sentinel lymph node (SLN) mapping of mice. Histological analyses were also carried out to ensure that the intravenously injected nanoparticles did not produce any toxicity to the organism of mice. These experimental results suggested that our ultrastable NIR PbS QDs can serve as biocompatible and efficient probes for in vivo optical bioimaging and has great potentials for disease diagnosis and clinical therapies in the future.

  17. Preparation and photoluminescence study of mesoporous indium hydroxide nanorods

    SciTech Connect

    Li, Changyu; Lian, Suoyuan; Liu, Yang; Liu, Shouxin; Kang, Zhenhui

    2010-02-15

    Mesoporous indium hydroxide nanorods were successfully synthesized by a mild one-step one-pot method. The obtained samples were characterized by X-ray diffraction, transmission electron microscopy with selected area electron diffraction, N{sub 2} adsorption, ultraviolet-visible absorption and photoluminescence, respectively. Transmission electron microscopy showed that there were some pores in the samples, which were mainly composed of rod-like shapes with length of 300 nm and diameter of 90 nm. N{sub 2} adsorption/desorption measurements confirmed that the prepared powder was mesoporous with average pore diameter of 3.1 nm. The ultraviolet-visible absorption spectroscopy analysis indicated that the band gap energy of the samples was 5.15 eV. Photoluminescence spectrum showed that there were two strong emissions under ultraviolet light irradiation. The growth mechanism of indium hydroxide nanorods and the role of cetyltrimethyl ammonium bromide were also discussed.

  18. Macromolecularly "Caged" Carbon Nanoparticles for Intracellular Trafficking via Switchable Photoluminescence.

    PubMed

    Misra, Santosh K; Srivastava, Indrajit; Tripathi, Indu; Daza, Enrique; Ostadhossein, Fatemeh; Pan, Dipanjan

    2017-02-08

    Reversible switching of photoluminescence (PL) of carbon nanoparticles (CNP) can be achieved with counterionic macromolecular caging and decaging at the nanoscale. A negatively charged uncoated, "bare" CNP with high luminescence loses its PL when positively charged macromolecules are wrapped around its surface. Prepared caged carbons could regain their emission only through interaction with anionic surfactant molecules, representing anionic amphiphiles of endocytic membranes. This process could be verified by gel electrophoresis, spectroscopically and in vitro confocal imaging studies. Results indicated for the first time that luminescence switchable CNPs can be synthesized for efficient intracellular tracking. This study further supports the origin of photoluminescence in CNP as a surface phenomenon correlated a function of characteristic charged macromolecules.

  19. UV-emitting phosphors: synthesis, photoluminescence and applications

    NASA Astrophysics Data System (ADS)

    Thakare, D. S.; Omanwar, S. K.; Muthal, P. L.; Dhopte, S. M.; Kondawar, V. K.; Moharil, S. V.

    2004-02-01

    UV-emitting phosphors find uses in various applications, such as photocopying, phototherapy, sun tanning, etc. The phosphor requirements for these applications vary. Simple methods for preparing different UV-emitting phosphors are described. Novel syntheses for some borates (SrB4O7:Eu, CeMgB5O10:Gd, GdBO3:Pr, LaB3O6:Ce,Bi, LaB3O6:Gd,Bi, LaB3O6:Ce, Ba2B5O9Cl:Eu), a silicate (Ba2SiO5:Pb), phosphates (Sr2-xMgxP2O7:Eu) and a sulphate (CaSO4:Eu) are reported. Photoluminescence spectra of the phosphors so prepared are presented and discussed in the context of applications like phototherapy and photocopying lamps, photoluminescent liquid crystal displays, radiophotoluminescence, etc.

  20. Supercollision cooling effects on the hot photoluminescence emission of graphene.

    PubMed

    Alencar, Thonimar V; Malard, Leandro M; Paula, Ana M de

    2016-09-30

    We report on hot photoluminescence measurements that show the effects of acoustic phonon supercollision processes in the intensity of graphene light emission. We use a simple optical method to induce defects on single layer graphene in a controlled manner to study in detail the light emission dependence on the sample defect density. It is now well accepted that the graphene photoluminescence is due to black-body thermal emission from the quasi-equilibrium electrons at a temperature well above the lattice temperature. Our results show that as the sample defect density is increased the electrons relax energy more efficiently via acoustic phonon supercollision processes leading to lower electron temperatures and thus lower emission intensities. The calculated intensity decrease due to supercollision energy relaxation agrees well with the experimental data.

  1. Photoluminescence Imaging Characterization of Thin-Film InP

    SciTech Connect

    Johnston, Steve; Allende Motz, Alyssa; Moore, James; Zheng, Maxwell; Javey, Ali; Bermel, Peter

    2015-06-14

    Indium phosphide grown using a novel vapor-liquid-solid method is a promising low-cost material for III-V single-junction photovoltaics. In this work, we characterize the properties of these materials using photoluminescence (PL) imaging, time-resolved photoluminescence (TRPL), and microwave-reflection photoconductive decay (u-PCD). PL image data clearly shows the emergence of a self-similar dendritic growth network from nucleation sites, while zoomed-in images show grain structure and grain boundaries. Single photon TRPL data shows initial surface-dominated recombination, while two-photon excitation TRPL shows a lifetime of 10 ns. Bulk carrier lifetime may be as long as 35 ns as measured by u-PCD, which can be less sensitive to surface recombination.

  2. Modulation of mixed-phase titania photoluminescence by oxygen adsorption

    SciTech Connect

    Pallotti, D.; Orabona, E.; Amoruso, S.; Maddalena, P.; Lettieri, S.

    2014-07-21

    We investigate the effect of oxygen (O{sub 2}) adsorption on photoluminescence properties of mixed-phase titania nanoparticle films deposited by femtosecond pulsed laser deposition, aiming to assess preliminary conclusions about the feasibility of opto-chemical sensing based on titania. We evidence that O{sub 2} produces opposite responses in rutile and anatase photoluminescence efficiency, highlighting interesting potentialities for future double-parametric optical sensing based on titania. The results evidence an important role of lattice oxygen atoms, suggesting that the standard Schottky barrier mechanism driving the response toward gas species in most used metal-oxide sensors (e.g., tin dioxide) is not the only active mechanism in titania.

  3. Spatially resolved micro-photoluminescence imaging of porphyrin single crystals

    NASA Astrophysics Data System (ADS)

    Marin, Dawn M.; Castaneda, Jose; Kaushal, Meesha; Kaouk, Ghallia; Jones, Daniel S.; Walter, Michael G.

    2016-08-01

    We describe the collection of both time-resolved and steady-state micro-photoluminescence data from solution-grown single crystals of 5,15-bis(4-carbomethoxyphenyl)porphyrin (BCM2PP). Linking molecular orientation and structure with excited-state dynamics is crucial for engineering efficient organic solar cells, light-emitting diodes, and related molecular electronics. Photoluminescence features of single porphyrin crystals were imaged using a laser scanning confocal microscope equipped with time-correlated single photon counting (TCSPC). We show enhanced exciton lifetimes (τs1 = 2.6 ns) and stronger steady-state emission in crystalline BCM2PP samples relative to semicrystalline thin films (τs1 = 1.8 ns).

  4. Probing local coordination and oxidation state of uranium in ThO2: U nanostructured

    NASA Astrophysics Data System (ADS)

    Gupta, Santosh K.; Pathak, N.; Kadam, R. M.

    2015-12-01

    Uranium doped thorium oxide nanoparticle (UDT) was synthesized using citric acid assisted combustion method. The concentration of uranium was varied from 0.5 to 5.0 mol % to investigate the effect of doping concentration on its optical properties. The synthesised UDT powder were characterized systematically using X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) respectively for phase purity, morphology and crystallinity. Pertaining to nuclear industry, UDT is an important material and investigating the local structure of uranium in UDT is interesting as well as challenging because of complexity involved in synthesis of such ceramic powder. We have used time resolved photoluminescence spectroscopy (TRPLS) to probe the local coordination and oxidation state of uranium in UDT. Based on PL emission spectroscopy it was confirmed that uranium stabilizes as UO22+ ion in UDT. Lifetime spectroscopy shows that uranyl ion is not homogenously distributed in UDT lattice; rather it has two different chemical environments. Effect of concentration on PL behaviour shows that, concentration quenching takes place beyond 2.0 mol %; and based on critical distance calculation multipolar interaction was found to be responsible for such non-radiative quenching. As far as application in luminescence industry is concerned PL measurement shows that UDT gives intense green emission under UV excitation.

  5. Sensitive fluorescence response of ZnSe(S) quantum dots: an efficient fluorescence probe

    NASA Astrophysics Data System (ADS)

    Saikia, K.; Deb, P.; Kalita, E.

    2013-06-01

    An efficient fluorescence probe based on ZnSe(S) alloyed quantum dots (QDs) has been reported here. The alloyed QDs were prepared through an aqueous route, where 3-mercaptopropionic acid (MPA) was employed as the effective precursor for both the sulfur source and stabilizer in the development of the alloyed system. Five-fold quantum yield (QY) enhancement was obtained for the ZnSe(S) QDs compared to the ZnSe QDs, formed in the initial stage of the refluxing process. The ultimate alloyed systems retained their high biocompatibility characteristics similar to the conventional ZnSe QDs. The photoluminescence of the ZnSe(S) QDs showed pH dependence, which was also evidenced in mammalian lymphocyte cells suspended in biological buffer over a wide pH range of 4.00-12.00. These characteristics make our prepared ZnSe(S) an efficient system for development of cell tracking, monitoring and sensing intracellular nanoprobes and devices.

  6. Low Temperature Photoluminescence (PL) from High Electron Mobility Transistors (HEMTs)

    DTIC Science & Technology

    2015-03-01

    temperature Photoluminescence (PL) from High Electron Mobility Transistor (HEMT) structures that have been modified by proton irradiation. The samples are...samples and exposed the structures to various levels of proton irradiation. For electronics operating in extreme environments where the parts...valence band, generating photons. This emission could be used to determine the effects of proton irradiation on a 2DEG. Exciting the HEMT samples

  7. Nonlinear broadband photoluminescence of graphene induced by femtosecond laser irradiation

    SciTech Connect

    Liu, Wei-Tao; Wu, S.W.; Schuck, P.J.; Salmeron, Miquel; Shen, Y.R.; Wang, F.

    2010-07-01

    Upon femtosecond laser irradiation, a bright, broadband photoluminescence is observed from graphene at frequencies well above the excitation frequency. Analyses show that it arises from radiative recombination of a broad distribution of nonequilibrium electrons and holes, generated by rapid scattering between photoexcited carriers within tens of femtoseconds after the optical excitation. Its highly unusual characteristics come from the unique electronic and structural properties of graphene.

  8. Properties of Zn-doped GaN. I - Photoluminescence

    NASA Technical Reports Server (NTRS)

    Pankove, J. I.; Berkeyheiser, J. E.; Miller, E. A.

    1974-01-01

    It is shown that zinc in gallium nitride forms an efficient radiative center emitting blue light at 2.86 plus or minus 0.02 eV and acts as a deep acceptor that can render the crystal insulating. A systematic variation of growth conditions indicates that an optimization of the photoluminescence efficiency is possible. Under nonoptimal conditions lower photon energy emission is obtained.

  9. 5 prime -Azido-(3,6- sup 3 H sub 2 )-1-naphthylphthalamic acid, a photoactivatable probe for naphthylphthalamic acid receptor proteins from higher plants: Identification of a 23-kDa protein from maize coleoptile plasma membranes

    SciTech Connect

    Zettl, R.; Feldwisch, J.; Schell, J.; Palme, K. ); Boland, W. )

    1992-01-15

    1-Naphthylphthalamic acid (NPA) is a specific inhibitor of polar auxin transport that blocks carrier mediated auxin efflux from plant cells. To allow identification of the NPA receptor thought to be part of the auxin efflux carrier, the authors have synthesized a tritiated, photolabile NPA analogue, 5{prime}-azido-(3,6-{sup 3}H{sub 2})NPA (({sup 3}H{sub 2})N{sub 3}NPA). This analogue was used to identify NPA-binding proteins in fractions highly enriched for plasma membrane vesicles isolated from maize coleoptiles (Zea mays L.). Competition studies showed that binding of ({sup 3}H{sub 2})N{sub 3}NPA to maize plasma membrane vesicles was blocked by nonradioactive NPA but not by benzoic acid. After incubation of plasma membrane vesicles with ({sup 3}H{sub 2})N{sub 3}NPA and exposure to UV light, they observed specific photoaffinity labeling of a protein with an apparent molecular mass of 23 kDa. Pretreatment of the plasma membrane vesicles with indole-3-acetic acid or with the auxin-transport inhibitors NPA and 2,3,5-triiodobenzoic acid strongly reduced specific labeling of this protein. This 23-kDa protein was also labeled by addition of 5-azido-(7-{sup 3}H)indole-3-acetic acid to plasma membranes prior to exposure to UV light. The 23-kDa protein was solubilized from plasma membranes by 1% Triton X-100. The possibility that this 23-kDa polypeptide is part of the auxin efflux carrier system is discussed.

  10. Acidic pH-induced membrane insertion of colicin A into E. coli natural lipids probed by site-directed spin labeling.

    PubMed

    Pulagam, Lakshmi Padmavathi; Steinhoff, Heinz-Jürgen

    2013-05-27

    Colicin A is a pore-forming toxin that forms a voltage-gated channel in the inner membrane of the target bacteria. The structures of the closed and open channel states of membrane-bound colicin A are not resolved. In the present site-directed spin-labeling study, the insertion-competent state of colicin A is provoked by an acidic pH jump prior to the insertion into liposomes prepared from Escherichia coli natural lipids. The membrane-bound colicin A is able to open a voltage-dependent channel as demonstrated by the efflux of tempophosphate spin label from the lumen of liposomes. The EPR spectra of spin-labeled colicin A variants in the membrane-bound closed channel state reveal a conformational equilibrium with resolved interhelical tertiary contacts. The spin label accessibility and polarity profiles suggest the amphipathic helices (H1-H7 and H10) to be located in the membrane close to the membrane-water interface and the hydrophobic hairpin (H8 and H9) to be immersed more deeply in the membrane.

  11. Probing Lewis Acid-Base Interactions with Born-Oppenheimer Molecular Dynamics: The Electronic Absorption Spectrum of p-Nitroaniline in Supercritical CO2.

    PubMed

    Cabral, Benedito J Costa; Rivelino, Roberto; Coutinho, Kaline; Canuto, Sylvio

    2015-07-02

    The structure and dynamics of p-nitroaniline (PNA) in supercritical CO2 (scCO2) at T = 315 K and ρ = 0.81 g cm(-3) are investigated by carrying out Born-Oppenheimer molecular dynamics, and the electronic absorption spectrum in scCO2 is determined by time dependent density functional theory. The structure of the PNA-scCO2 solution illustrates the role played by Lewis acid-base (LA-LB) interactions. In comparison with isolated PNA, the ν(N-O) symmetric and asymmetric stretching modes of PNA in scCO2 are red-shifted by -17 and -29 cm(-1), respectively. The maximum of the charge transfer (CT) absorption band of PNA in scSCO2 is at 3.9 eV, and the predicted red-shift of the π → π* electronic transition relative to the isolated gas-phase PNA molecule reproduces the experimental value of -0.35 eV. An analysis of the relationship between geometry distortions and excitation energies of PNA in scCO2 shows that the π → π* CT transition is very sensitive to changes of the N-O bond distance, strongly indicating a correlation between vibrational and electronic solvatochromism driven by LA-LB interactions. Despite the importance of LA-LB interactions to explain the solvation of PNA in scCO2, the red-shift of the CT band is mainly determined by electrostatic interactions.

  12. Selective photo-deposition of Cu onto the surface of monodisperse oleic acid capped TiO2 nanorods probed by FT-IR CO-adsorption studies.

    PubMed

    Hikov, Todor; Schroeter, Marie-Katrin; Khodeir, Lamma; Chemseddine, Abdelkrim; Muhler, Martin; Fischer, Roland A

    2006-04-07

    A novel, non-aqueous, organometallic route to nanocomposite Cu@TiO2 materials is presented. TiO2 nanorods stabilized with oleic acid (OLA) were used as support for the photo-assisted deposition of Cu using the organometallic Cu(II) precursor [Cu(OCH(CH3)CH2N(CH3)2)2] (1). The copper precursor penetrates through the shell of OLA and is photo reduced to deposit Cu0 directly at the surface of the TiO2 rods. The obtained Cu decorated nanorods were still soluble in nonpolar organic solvents without change of the morphology of nanorods. The Cu@TiO2 colloid was characterized by means of UV-VIS, XRD, AAS, and HRTEM. FTIR CO adsorption studies provide evidence for Cu0 anchored at the titania surface by a characteristic absorption at 2084 cm-1. Comparative studies of Cu-deposition were performed using CuCl2 as simple Cu source which proved that the concept of organometallic disguise of the metal centre results in a higher reaction rate and the circumvention of non-selective reduction, parasitic side reactions and undesired agglomeration of the OLA stabilized titania nanorods.

  13. Hot-wire probe

    NASA Technical Reports Server (NTRS)

    Mikulla, V.

    1976-01-01

    High-temperature platinum probe measures turbulence and Reynolds shear stresses in high-temperature compressible flows. Probe does not vibrate at high velocities and does not react like strain gage on warmup.

  14. Production rate estimation of mycosporine-like amino acids in two Arctic melt ponds by stable isotope probing with NAH(13) CO3.

    PubMed

    Ha, Sun-Yong; Min, Jun-Oh; Joo, Hyun Min; Chung, Kyung Ho; Shin, Kyung-Hoon; Yang, EunJin; Kang, Sung-Ho

    2014-10-01

    The net carbon uptake rate and net production rate of mycosporine-like amino acids (MAAs) were measured in phytoplankton from 2 different melt ponds (MPs; closed and open type pond) in the western Arctic Ocean using a (13) C stable isotope tracer technique. The Research Vessel Araon visited ice-covered western-central basins situated at 82°N and 173°E in the summer of 2012, when Arctic sea ice declined to a record minimum. The average net carbon uptake rate of the phytoplankton in polycarbonate (PC) bottles in the closed MP was 3.24 mg C · m(-3) · h(-1) (SD = ±1.12 mg C · m(-3) · h(-1) ), while that in the open MP was 1.3 mg C · m(-3) · h(-1) (SD = ±0.05 mg C · m(-3) · h(-1) ). The net production rate of total MAAs in incubated PC bottles was highest (1.44 (SD = ±0.24) ng C · L(-1) · h(-1) ) in the open MP and lowest (0.05 (SD = ±0.003) ng C · L(-1) · h(-1) ) in the closed MP. The net production rate of shinorine and palythine in incubated PC bottles at the open MP presented significantly high values 0.76 (SD = ±0.12) ng C · L(-1) · h(-1) and 0.53 (SD = ±0.06) ng C · L(-1) · h(-1) . Our results showed that high net production rate of MAAs in the open MP was enhanced by a combination of osmotic and UVR stress and that in situ net production rates of individual MAA can be determined using (13) C tracer in MPs in Arctic sea ice.

  15. Developing an Acidic Residue Reactive and Sulfoxide-Containing MS-Cleavable Homobifunctional Cross-Linker for Probing Protein–Protein Interactions

    PubMed Central

    2016-01-01

    Cross-linking mass spectrometry (XL-MS) has become a powerful strategy for defining protein–protein interactions and elucidating architectures of large protein complexes. However, one of the inherent challenges in MS analysis of cross-linked peptides is their unambiguous identification. To facilitate this process, we have previously developed a series of amine-reactive sulfoxide-containing MS-cleavable cross-linkers. These MS-cleavable reagents have allowed us to establish a common robust XL-MS workflow that enables fast and accurate identification of cross-linked peptides using multistage tandem mass spectrometry (MSn). Although amine-reactive reagents targeting lysine residues have been successful, it remains difficult to characterize protein interaction interfaces with little or no lysine residues. To expand the coverage of protein interaction regions, we present here the development of a new acidic residue-targeting sulfoxide-containing MS-cleavable homobifunctional cross-linker, dihydrazide sulfoxide (DHSO). We demonstrate that DHSO cross-linked peptides display the same predictable and characteristic fragmentation pattern during collision induced dissociation as amine-reactive sulfoxide-containing MS-cleavable cross-linked peptides, thus permitting their simplified analysis and unambiguous identification by MSn. Additionally, we show that DHSO can provide complementary data to amine-reactive reagents. Collectively, this work not only enlarges the range of the application of XL-MS approaches but also further demonstrates the robustness and applicability of sulfoxide-based MS-cleavability in conjunction with various cross-linking chemistries. PMID:27417384

  16. Probing the roles of Ca(2+) and Mg(2+) in humic acids-induced ultrafiltration membrane fouling using an integrated approach.

    PubMed

    Wang, Long-Fei; He, Dong-Qin; Chen, Wei; Yu, Han-Qing

    2015-09-15

    Membrane fouling induced by natural organic matter (NOM) negatively affects the performance of ultrafiltration (UF) technology in producing drinking water. Divalent cation is found to be an important factor that affects the NOM-induced membrane fouling process. In this work, attenuated total reflection-Fourier transformation infrared spectroscopy (ATR-FTIR) coupled with quartz crystal microbalance (QCM), assisted by isothermal titration calorimetry (ITC), is used to explore the contribution of Mg(2+) and Ca(2+), the two abundant divalent cations in natural water, to the UF membrane fouling caused by humic acid (HA) at a molecular level. The results show that Ca(2+) exhibited superior performance in accelerating fouling compared to Mg(2+). The hydrophobic polyethersulfone (PES) membrane exhibited greater complexation with HA in the presence of Mg(2+) and Ca(2+), compared to the hydrophilic cellulose membrane, as evidenced by the more intense polysaccharide C-O, aromatic C=C and carboxylic C=O bands in the FTIR spectra. The QCM and ITC measurements provide quantitative evidence to support that Ca(2+) was more effective than Mg(2+) in binding with HA and accumulating foulants on the membrane surfaces. The higher charge neutralization capacity and more favorable binding ability of Ca(2+) were found to be responsible for its greater contribution to the NOM-induced membrane fouling than Mg(2+). This work offers a new insight into the mechanism of cation-mediated NOM-induced membrane fouling process, and demonstrates that such an integrated ATR-FTIR/QCM/ITC approach could be a useful tool to explore other complicated interaction processes in natural and engineered environments.

  17. The use of retinoic acid to probe the relation between hyperproliferation-associated keratins and cell proliferation in normal and malignant epidermal cells

    PubMed Central

    1989-01-01

    When cells from normal human epidermis and from the human squamous cell carcinoma line SCC-13 were seeded on floating rafts of collagen and fibroblasts, they stratified and underwent terminal differentiation. Although the program of differentiation in SCC-13 cells was morphologically abnormal, the cultures resembled normal epidermal raft cultures by expressing the terminal differentiation-specific keratins, K1/K10, and by restricting their proliferative capacity to the basal- like cells of the population. In addition, the differentiating cells of both normal and SCC-13 raft cultures expressed keratins K6 and K16, which are not normally expressed in epidermis, but are synthesized suprabasally during wound-healing and in various epidermal diseases associated with hyperproliferation. While the behavior of normal and SCC-13 rafts was quite similar when they were cultured over normal medium, significant biochemical differences began to emerge when the cultures were exposed to retinoic acid. Most notably, while the SCC-13 cultures still stratified extensively, they showed a marked inhibition of both abnormal (K6/K16) and normal (K1/K10) differentiation- associated keratins, concomitantly with an overall disappearance of differentiated phenotype. Surprisingly, the reduction in K6/K16 in retinoid-treated SCC-13 cultures was not accompanied by a decrease in cell proliferation. Using immunohistochemistry combined with [3H]thymidine labeling, we demonstrate that while the expression of K6 and K16 are often associated with hyperproliferation, these keratins are only produced in the nondividing, differentiating populations of proliferating cultures. Moreover, since their expression can be suppressed without a corresponding decrease in proliferation, the expression of these keratins cannot be essential to the nature of the hyperproliferative epidermal cell. PMID:2473080

  18. Mechanoresponsive change in photoluminescent color of rod-like liquid-crystalline compounds and control of molecular orientation on photoaligned layer

    NASA Astrophysics Data System (ADS)

    Kondo, Mizuho; Miura, Seiya; Okumoto, Kentaro; Hashimoto, Mayuko; Fukae, Ryohei; Kawatsuki, Nobuhiro

    2014-10-01

    In this paper, we reported novel liquid-crystalline luminophore that switches its photoluminescent color by mechanically grinding. Mechanochromic luminescence (MCL) is expected for mechanical sensor, cellular imaging, detection of microenvironmental changes, and optical memory. In this work, we focused on liquid-crystalline MCL compounds on alignment layer. Controlling the molecular alignment of MCL compounds with photoalignment layer have potential to succeed in functional MCL film such as polarized micropatterned MCL and directional detection of mechanical stimuli. Herein, we prepared asymmetric rodlike MCL compounds containing cyano- and pyridyl molecular terminal and explored their photoluminescence behavior under mechanical stimulus. The cyano terminated compound showed a nematic phase and tuned its photoluminescent color from green to yellow upon grinding, while the pyridyl-terminated compounds that show no mesophase changed its photoluminescent color from blue to green and reverted to its initial color by heating above its melting point. The cyano-terminated MCL was aligned along the orientation direction of photoalignment layer and pyridyl-terminated MCL exhibited uniaxial alignment when it coated on photoaligned film containing carboxylic acid.

  19. Galileo Probe Battery System

    NASA Technical Reports Server (NTRS)

    Dagarin, B. P.; Taenaka, R. K.; Stofel, E. J.

    1997-01-01

    The conclusions of the Galileo probe battery system are: the battery performance met mission requirements with margin; extensive ground-based and flight tests of batteries prior to probe separation from orbiter provided good prediction of actual entry performance at Jupiter; and the Li-SO2 battery was an important choice for the probe's main power.

  20. A Magnetoresistance Measuring Probe.

    DTIC Science & Technology

    The in line four point probe, commonly used for measuring the sheet resistance in a conductor, cannot measure the anisotropic ferromagnetic magnetoresistance. However, the addition of two contact points that are not collinear with the current contacts give the probe the ability to non-destructively measure the anistropic magnetoresistance. Keywords: Magnetoresistance; Anisotropic; Thin-Film; Permalloy; Four Point Probe; Anisotropic Resistance.

  1. Probing catalysis by Escherichia coli dTDP-glucose-4,6-dehydratase: identification and preliminary characterization of functional amino acid residues at the active site.

    PubMed

    Hegeman, A D; Gross, J W; Frey, P A

    2001-06-05

    A model of the Escherichia coli dTDP-glucose-4,6-dehydratase (4,6-dehydratase) active site has been generated by combining amino acid sequence alignment information with the 3-dimensional structure of UDP-galactose-4-epimerase. The active site configuration is consistent with the partially refined 3-dimensional structure of 4,6-dehydratase, which lacks substrate-nucleotide but contains NAD(+) (PDB file ). From the model, two groups of active site residues were identified. The first group consists of Asp135(DEH), Glu136(DEH), Glu198(DEH), Lys199(DEH), and Tyr301(DEH). These residues are near the substrate-pyranose binding pocket in the model, they are completely conserved in 4,6-dehydratase, and they differ from the corresponding equally well-conserved residues in 4-epimerase. The second group of residues is Cys187(DEH), Asn190(DEH), and His232(DEH), which form a motif on the re face of the cofactor nicotinamide binding pocket that resembles the catalytic triad of cysteine-proteases. The importance of both groups of residues was tested by mutagenesis and steady-state kinetic analysis. In all but one case, a decrease in catalytic efficiency of approximately 2 orders of magnitude below wild-type activity was observed. Mutagenesis of each of these residues, with the exception of Cys187(DEH), which showed near-wild-type activity, clearly has important negative consequences for catalysis. The allocation of specific functions to these residues and the absolute magnitude of these effects are obscured by the complex chemistry in this multistep mechanism. Tools will be needed to characterize each chemical step individually in order to assign loss of catalytic efficiency to specific residue functions. To this end, the effects of each of these variants on the initial dehydrogenation step were evaluated using a the substrate analogue dTDP-xylose. Additional steady-state techniques were employed in an attempt to further limit the assignment of rate limitation. The results are

  2. Raman tags: Novel optical probes for intracellular sensing and imaging.

    PubMed

    Li, Yuee; Wang, Zhong; Mu, Xijiao; Ma, Aning; Guo, Shu

    Optical labels are needed for probing specific target molecules in complex biological systems. As a newly emerging category of tags for molecular imaging in live cells, the Raman label attracts much attention because of the rich information obtained from targeted and untargeted molecules by detecting molecular vibrations. Here, we list three types of Raman probes based on different mechanisms: Surface Enhanced Raman Scattering (SERS) probes, bioorthogonal Raman probes, and Resonance Raman (RR) probes. We review how these Raman probes work for detecting and imaging proteins, nucleic acids, lipids, and other biomolecules in vitro, within cells, or in vivo. We also summarize recent noteworthy studies, expound on the construction of every type of Raman probe and operating principle, sum up in tables typically targeting molecules for specific binding, and provide merits, drawbacks, and future prospects for the three Raman probes.

  3. Use of a fiber optic probe for organic species determination

    DOEpatents

    Ekechukwu, Amy A.

    1996-01-01

    A fiber optic probe for remotely detecting the presence and concentration organic species in aqueous solutions. The probe includes a cylindrical housing with an organic species indicator, preferably diaminonaphthyl sulfonic acid adsorbed in a silica gel (DANS-modified gel), contained in the probe's distal end. The probe admits aqueous solutions to the probe interior for mixing within the DANS-modified gel. An optical fiber transmits light through the DANS-modified gel while the indicator reacts with organic species present in the solution, thereby shifting the location of the fluorescent peak. The altered light is reflected to a receiving fiber that carries the light to a spectrophotometer or other analysis device.

  4. Reusable fluorescent sensor for captopril based on energy transfer from photoluminescent graphene oxide self-assembly multilayers to silver nanoparticles.

    PubMed

    Sun, Xiangying; Liu, Bin; Li, Shuchun; Li, Fang

    2016-05-15

    In this work we designed a self-assembly multilayers, in which photoluminescent graphene oxide was employed as a fluorescence probe. This multilayers film can effectively recognize captopril by resonance energy transfer from graphite oxide to silver nanoparticles. A new interfacial sensing method for captopril with high signal to noise ratio was established, by means of that multilayers was quenched by silver nanoparticles and subsequently recovered by adding captopril. The linear relation between intensity and captopril concentration was good, and the detection limit was found to be 0.1578 μM. Also, this novel detection platform demonstrated intriguing reusable properties, and the sensor could be repeated more than ten times without obviously losing its sensing performance.

  5. Reusable fluorescent sensor for captopril based on energy transfer from photoluminescent graphene oxide self-assembly multilayers to silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Sun, Xiangying; Liu, Bin; Li, Shuchun; Li, Fang

    2016-05-01

    In this work we designed a self-assembly multilayers, in which photoluminescent graphene oxide was employed as a fluorescence probe. This multilayers film can effectively recognize captopril by resonance energy transfer from graphite oxide to silver nanoparticles. A new interfacial sensing method for captopril with high signal to noise ratio was established, by means of that multilayers was quenched by silver nanoparticles and subsequently recovered by adding captopril. The linear relation between intensity and captopril concentration was good, and the detection limit was found to be 0.1578 μM. Also, this novel detection platform demonstrated intriguing reusable properties, and the sensor could be repeated more than ten times without obviously losing its sensing performance.

  6. [Effects of different annealing conditions on the photoluminescence of nanoporous alumina film].

    PubMed

    Xie, Ning; Ma, Kai-Di; Shen, Yi-Fan; Wang, Qian

    2013-12-01

    The nanoporous alumina films were prepared by two-step anodic oxidation in 0.5 mol L-1 oxalic acid electrolyte at 40 V. Photoluminescence (PL) of nanoporous alumina films was investigated under different annealing atmosphere and different temperature. The authors got three results about the PL measurements. In the same annealing atmosphere, when the annealling temperature T< or =600 degreeC, the intensity of the PL peak increases with elevated annealing temperature and reaches a maximum value at 500 degreeC, but the intensity decreases with a further increase in the annealing temperature, and the PL peak intensity of samples increases with the increase in the annealing temperature when the annealling temperature T> or =800 degreeC. In the different annealling atmosphere, the change in the photoluminescence peak position for nanoporous alumina films with the increase in the annealing temperature is different: With the increase in the annealling temperature, the PL peak position for the samples annealed in air atmosphere is blue shifted, while the PL peak position for the samples annealed in vacuum atmosphere will not change. The PL spectra of nanoporous alumina films annealed at 1100 degreeC in air atmosphere can be de-convoluted by three Gaussian components at an excitation wavelength of 350 nm, with bands centered at 387, 410 and 439 nm, respectively. These results suggest that there might be three luminescence centers for the PL of annealed alumina films. At the same annealling temperature, the PL peak intensity of samples annealed in air atmosphere is stronger than that annealed in the vacuum. Based on the experimental results and the X-ray dispersive energy spectrum (EDS) combined with infrared reflect spectra, the luminescence mechanisms of nanoporous alumina films are discussed. There are three luminescence centers in the annealed nanoporous alumina films, which originate from the F center, F+ center and the center associated with the oxalic impurities. The

  7. Ultrafast scanning probe microscopy

    DOEpatents

    Weiss, Shimon; Chemla, Daniel S.; Ogletree, D. Frank; Botkin, David

    1995-01-01

    An ultrafast scanning probe microscopy method for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample.

  8. Traversing probe system

    DOEpatents

    Mashburn, Douglas N.; Stevens, Richard H.; Woodall, Harold C.

    1977-01-01

    This invention comprises a rotatable annular probe-positioner which carries at least one radially disposed sensing probe, such as a Pitot tube having a right-angled tip. The positioner can be coaxially and rotatably mounted within a compressor casing or the like and then actuated to orient the sensing probe as required to make measurements at selected stations in the annulus between the positioner and compressor casing. The positioner can be actuated to (a) selectively move the probe along its own axis, (b) adjust the yaw angle of the right-angled probe tip, and (c) revolve the probe about the axis common to the positioner and casing. A cam plate engages a cam-follower portion of the probe and normally rotates with the positioner. The positioner includes a first-motor-driven ring gear which effects slidable movement of the probe by rotating the positioner at a time when an external pneumatic cylinder is actuated to engage the cam plate and hold it stationary. When the pneumatic cylinder is not actuated, this ring gear can be driven to revolve the positioner and thus the probe to a desired circumferential location about the above-mentioned common axis. A second motor-driven ring gear included in the positioner can be driven to rotate the probe about its axis, thus adjusting the yaw angle of the probe tip. The positioner can be used in highly corrosive atmosphere, such as gaseous uranium hexafluoride.

  9. Ultrafast scanning probe microscopy

    DOEpatents

    Weiss, S.; Chemla, D.S.; Ogletree, D.F.; Botkin, D.

    1995-05-16

    An ultrafast scanning probe microscopy method is described for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample. 6 Figs.

  10. Young's type interference for probing the mode symmetry in photonic structures.

    PubMed

    Intonti, F; Riboli, F; Caselli, N; Abbarchi, M; Vignolini, S; Wiersma, D S; Vinattieri, A; Gerace, D; Balet, L; Li, L H; Francardi, M; Gerardino, A; Fiore, A; Gurioli, M

    2011-04-08

    A revisited realization of the Young's double slit experiment is introduced to directly probe the photonic mode symmetry by photoluminescence experiments. We experimentally measure the far field angular emission pattern of quantum dots embedded in photonic molecules. The experimental data well agree with predictions from Young's interference and numerical simulations. Moreover, the vectorial nature of photonic eigenmodes results in a rather complicated parity property for different polarizations, a feature which has no counterpart in quantum mechanics.

  11. Young's Type Interference for Probing the Mode Symmetry in Photonic Structures

    NASA Astrophysics Data System (ADS)

    Intonti, F.; Riboli, F.; Caselli, N.; Abbarchi, M.; Vignolini, S.; Wiersma, D. S.; Vinattieri, A.; Gerace, D.; Balet, L.; Li, L. H.; Francardi, M.; Gerardino, A.; Fiore, A.; Gurioli, M.

    2011-04-01

    A revisited realization of the Young’s double slit experiment is introduced to directly probe the photonic mode symmetry by photoluminescence experiments. We experimentally measure the far field angular emission pattern of quantum dots embedded in photonic molecules. The experimental data well agree with predictions from Young’s interference and numerical simulations. Moreover, the vectorial nature of photonic eigenmodes results in a rather complicated parity property for different polarizations, a feature which has no counterpart in quantum mechanics.

  12. Electrical resistivity probes

    DOEpatents

    Lee, Ki Ha; Becker, Alex; Faybishenko, Boris A.; Solbau, Ray D.

    2003-10-21

    A miniaturized electrical resistivity (ER) probe based on a known current-voltage (I-V) electrode structure, the Wenner array, is designed for local (point) measurement. A pair of voltage measuring electrodes are positioned between a pair of current carrying electrodes. The electrodes are typically about 1 cm long, separated by 1 cm, so the probe is only about 1 inch long. The electrodes are mounted to a rigid tube with electrical wires in the tube and a sand bag may be placed around the electrodes to protect the electrodes. The probes can be positioned in a borehole or on the surface. The electrodes make contact with the surrounding medium. In a dual mode system, individual probes of a plurality of spaced probes can be used to measure local resistance, i.e. point measurements, but the system can select different probes to make interval measurements between probes and between boreholes.

  13. A Label-Free Photoluminescence Genosensor Using Nanostructured Magnesium Oxide for Cholera Detection.

    PubMed

    Patel, Manoj Kumar; Ali, Md Azahar; Krishnan, Sadagopan; Agrawal, Ved Varun; Al Kheraif, AbdulAziz A; Fouad, H; Ansari, Z A; Ansari, S G; Malhotra, Bansi D

    2015-11-27

    Nanomaterial-based photoluminescence (PL) diagnostic devices offer fast and highly sensitive detection of pesticides, DNA, and toxic agents. Here we report a label-free PL genosensor for sensitive detection of Vibrio cholerae that is based on a DNA hybridization strategy utilizing nanostructured magnesium oxide (nMgO; size >30 nm) particles. The morphology and size of the synthesized nMgO were determined by transmission electron microscopic (TEM) studies. The probe DNA (pDNA) was conjugated with nMgO and characterized by X-ray photoelectron and Fourier transform infrared spectroscopic techniques. The target complementary genomic DNA (cDNA) isolated from clinical samples of V. cholerae was subjected to DNA hybridization studies using the pDNA-nMgO complex and detection of the cDNA was accomplished by measuring changes in PL intensity. The PL peak intensity measured at 700 nm (red emission) increases with the increase in cDNA concentration. A linear range of response in the developed PL genosensor was observed from 100 to 500 ng/μL with a sensitivity of 1.306 emi/ng, detection limit of 3.133 ng/μL and a regression coefficient (R(2)) of 0.987. These results show that this ultrasensitive PL genosensor has the potential for applications in the clinical diagnosis of cholera.

  14. Photoluminescence of polydiacetylene membranes on porous silicon utilized for chemical sensors

    NASA Astrophysics Data System (ADS)

    Sabatani, Eyal; Kalisky, Yehoshua; Berman, Amir; Golan, Yuval; Gutman, Nadav; Urbach, Benayahu; Sa'ar, Amir

    2008-07-01

    Langmuir-Blodgett (LB) films of the conjugated polydiacetylene (PDA) exhibit spectroscopic behavior, which is dependent on the type of the supporting substrate. While on polished silicon surfaces the photoluminescence (PL) of PDA is quenched, it is preserved on top of 2D patterned macro-porous silicon (2D-MPS). 2D-MPS, prepared by electrochemical etching of photo-lithographically pre-patterned silicon, is a 2D array of ca. 10 μm deep pores with lateral 2-4 μm repeating unit cells in orthogonal or hexagonal arrangements. LB films of PDA on such surfaces form membranes with continuous domains of the size sufficient to cover laterally many cell units. Apparently, the PL from this film results exclusively from the portion of the PDA membrane which is suspended over pore openings, while portions of the film which are attached to the silicon on top of the pores walls does not exhibit PL at all. We have used these membranes in different configurations and exposed them to different chemical and biological agents and followed the PL intensity change. This report demonstrates the effectiveness of the combined system: LB films of PDA on top of 2D-MPS as sensing probe for a variety of chemicals including, Cd ions and TNT explosives. In addition, the use of films of PDA, in which glycol-lipid were embedded, for binding and recognition of lectin protein, mimicking the cell membrane interaction with its environment, is also demonstrated.

  15. A Label-Free Photoluminescence Genosensor Using Nanostructured Magnesium Oxide for Cholera Detection

    NASA Astrophysics Data System (ADS)

    Patel, Manoj Kumar; Ali, Md. Azahar; Krishnan, Sadagopan; Agrawal, Ved Varun; Al Kheraif, Abdulaziz A.; Fouad, H.; Ansari, Z. A.; Ansari, S. G.; Malhotra, Bansi D.

    2015-11-01

    Nanomaterial-based photoluminescence (PL) diagnostic devices offer fast and highly sensitive detection of pesticides, DNA, and toxic agents. Here we report a label-free PL genosensor for sensitive detection of Vibrio cholerae that is based on a DNA hybridization strategy utilizing nanostructured magnesium oxide (nMgO; size >30 nm) particles. The morphology and size of the synthesized nMgO were determined by transmission electron microscopic (TEM) studies. The probe DNA (pDNA) was conjugated with nMgO and characterized by X-ray photoelectron and Fourier transform infrared spectroscopic techniques. The target complementary genomic DNA (cDNA) isolated from clinical samples of V. cholerae was subjected to DNA hybridization studies using the pDNA-nMgO complex and detection of the cDNA was accomplished by measuring changes in PL intensity. The PL peak intensity measured at 700 nm (red emission) increases with the increase in cDNA concentration. A linear range of response in the developed PL genosensor was observed from 100 to 500 ng/μL with a sensitivity of 1.306 emi/ng, detection limit of 3.133 ng/μL and a regression coefficient (R2) of 0.987. These results show that this ultrasensitive PL genosensor has the potential for applications in the clinical diagnosis of cholera.

  16. Au/SiO2/QD core/shell/shell nanostructures with plasmonic-enhanced photoluminescence

    NASA Astrophysics Data System (ADS)

    Yang, Ping; Kawasaki, Kazunori; Ando, Masanori; Murase, Norio

    2012-09-01

    A sol-gel method has been developed to fabricate Au/SiO2/quantum dot (QD) core-shell-shell nanostructures with plasmonic-enhanced photoluminescence (PL). Au nanoparticle (NP) was homogeneously coated with a SiO2 shell with adjusted thickness through a Stöber synthesis. When the toluene solution of hydrophobic CdSe/ZnS QDs was mixed with partially hydrolyzed 3-aminopropyltrimethoxysilane (APS) sol, the ligands on the QDs were replaced by a thin functional SiO2 layer because the amino group in partially hydrolyzed APS has strong binding interaction with the QDs. Partially hydrolyzed APS plays an important role as a thin functional layer for the transfers of QDs to water phase and the subsequent connection to aqueous SiO2-coated Au NPs. Although Au NPs were demonstrated as efficient PL quenchers when the SiO2 shell on the Au NPs is thin (less than 5 nm), we found that precise control of the spacing between the Au NP core and the QD shell resulted in QDs with an enhancement of 30 % of PL efficiency. The Au/SiO2/QD core/shell/shell nanostructures also reveal strong surface plasmon scattering, which makes the Au/SiO/QD core-shell-shell nanostructures an excellent dual-modality imaging probe. This technology can serve as a general route for encapsulating a variety of discrete nanomaterials because monodispersed nanostructures often have a similar surface chemistry.

  17. A Label-Free Photoluminescence Genosensor Using Nanostructured Magnesium Oxide for Cholera Detection

    PubMed Central

    Patel, Manoj Kumar; Ali, Md. Azahar; Krishnan, Sadagopan; Agrawal, Ved Varun; Al Kheraif, AbdulAziz A.; Fouad, H.; Ansari, Z.A.; Ansari, S. G.; Malhotra, Bansi D.

    2015-01-01

    Nanomaterial-based photoluminescence (PL) diagnostic devices offer fast and highly sensitive detection of pesticides, DNA, and toxic agents. Here we report a label-free PL genosensor for sensitive detection of Vibrio cholerae that is based on a DNA hybridization strategy utilizing nanostructured magnesium oxide (nMgO; size >30 nm) particles. The morphology and size of the synthesized nMgO were determined by transmission electron microscopic (TEM) studies. The probe DNA (pDNA) was conjugated with nMgO and characterized by X-ray photoelectron and Fourier transform infrared spectroscopic techniques. The target complementary genomic DNA (cDNA) isolated from clinical samples of V. cholerae was subjected to DNA hybridization studies using the pDNA-nMgO complex and detection of the cDNA was accomplished by measuring changes in PL intensity. The PL peak intensity measured at 700 nm (red emission) increases with the increase in cDNA concentration. A linear range of response in the developed PL genosensor was observed from 100 to 500 ng/μL with a sensitivity of 1.306 emi/ng, detection limit of 3.133 ng/μL and a regression coefficient (R2) of 0.987. These results show that this ultrasensitive PL genosensor has the potential for applications in the clinical diagnosis of cholera. PMID:26611737

  18. Phenylboronic acid functionalized reduced graphene oxide based fluorescence nano sensor for glucose sensing.

    PubMed

    Basiruddin, S K; Swain, Sarat K

    2016-01-01

    Reduced graphene has emerged as promising tools for detection based application of biomolecules as it has high surface area with strong fluorescence quenching property. We have used the concept of fluorescent quenching property of reduced graphene oxide to the fluorescent probes which are close vicinity of its surface. In present work, we have synthesized fluorescent based nano-sensor consist of phenylboronic acid functionalized reduced graphene oxide (rGO-PBA) and di-ol modified fluorescent probe for detection of biologically important glucose molecules. This fluorescent graphene based nano-probe has been characterized by high resolution transmission electron microscope (HRTEM), Atomic force microscope (AFM), UV-visible, Photo-luminescence (PL) and Fourier transformed infrared (FT-IR) spectroscopy. Finally, using this PBA functionalized reduced GO based nano-sensor, we were able to detect glucose molecule in the range of 2 mg/mL to 75 mg/mL in aqueous solution of pH7.4.

  19. Photoluminescence of Undoped, Semi-Insulating, and Mg-Implanted Indium Phosphide.

    DTIC Science & Technology

    1979-12-01

    PH/79D-8 PHOTOLUMINESCENCE OF UNDOPED, SEMI-INSULATING, AND Mg- IMPLANTED INDIUM PHOSPHIDE THESIS Presented to the Faculty of the School of Engineering...Unannealed, Unimplanted and Mg- Implanted InP:Fe at 500 K ...... 132 Appendix H: Photoluminescence of Mg- Implanted , 750* C Annealed InP:Fe at 50 K...136 Appendix I: Photoluminescence of Mg- Implanted , 7000 C Annealed InP:Fe at 4.20 K ..................... 146 Appendix J

  20. Near-infrared and visible photoluminescence from argon plasma polymerized fullerene film

    SciTech Connect

    Xu, C.; Chen, G.; Xie, E.; Gong, J.

    1997-05-01

    Oxygenated polymeric fullerene films synthesized in argon plasma show strong photoluminescence in near-infrared and visible region (1.50{endash}2.36 eV) at room temperature excited by a 514.5 nm argon ion laser. After being annealed at different high temperatures, photoluminescence decreased in intensity. The generation and decrease of the photoluminescence were explained in terms of the change of the fullerene C{sub 60} symmetry. {copyright} {ital 1997 American Institute of Physics.}