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Jean Duhamel - One of the best experts on this subject based on the ideXlab platform.
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Interior of Amylopectin and Nano-Sized Amylopectin Fragments Probed by Viscometry, Dynamic Light Scattering, and Pyrene Excimer Fluorescence
Polymers, 2020Co-Authors: Jean DuhamelAbstract:Nano-sized amylopectin fragments (NAFs), prepared by extrusion of waxy corn starch, were investigated by viscometry, dynamic light scattering (DLS), and pyrene Excimer Fluorescence (PEF). NAF57, with a hydrodynamic diameter of 57 nm, was treated with nitric acid to yield three degraded NAFs, which appeared to share the same interior and structural features as amylopectin based on their measured intrinsic viscosity and hydrodynamic diameter. This conclusion was further supported by comparing the efficiency of forming Excimer between an excited and a ground-state pyrenyl label covalently attached to the NAFs (Py-NAFs) using their IE/IM ratio of the Fluorescence intensity of the Excimer (IE) to that of the monomer (IM). The overlapping trends obtained for all Py-NAFs and the pyrene-labeled amylopectin samples by plotting the IE/IM ratio as a function of pyrene content provided further evidence that the interior of NAFs and amylopectin shared the same structural features and contained a similar amount of free volume as predicted by the Solution-Cluster (Sol-CL) model. The presence of free volume was validated by adding linear poly(ethylene glycol) (PEG) chains that could not penetrate the interior of Py-NAFs, thus subjecting the Py-NAFs to increased osmotic pressure, which induced their compression and resulted in an increase in IE/IM.
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arborescent poly l glutamic acid s as standards to study the dense interior of polypeptide mesoglobules by pyrene Excimer Fluorescence
Macromolecules, 2018Co-Authors: Timothy Hall, Gregory Allan Whitton, Remi Casier, Mario Gauthier, Jean DuhamelAbstract:A series of arborescent poly(l-glutamic acid)s of generations 0 to 3 (PGA(GY) with Y = 0–3) were randomly labeled with 1-pyrenemethylamine to yield several Py-PGA(GY) constructs with pyrene contents ranging between 2.5 and 22 mol %. The density (ρ) of the interior of the PGA(GY) samples was estimated in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) by conducting gel permeation chromatography and dynamic light scattering experiments to determine their molar mass and hydrodynamic diameter, respectively. It was determined that ρ increased with the generation number from PGA(G1) to PGA(G2), which promoted more contacts between the pyrene labels. The increase in the number of pyrene–pyrene contacts was quantified with the parameter Nblob obtained by analysis of the Fluorescence decays for the Py-PGA(GY) samples in DMF and DMSO. In the analysis, Nblob represented the number of structural units, i.e., glutamic acid residues, comprised inside the volume probed by an exited pyrene, termed a blob. Insid...
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Long Range Polymer Chain Dynamics of Highly Flexible Polysiloxane in Solution Probed by Pyrene Excimer Fluorescence
MDPI AG, 2018Co-Authors: Janine L. Thoma, Jean Duhamel, Michael J. Bertocchi, Richard G. WeissAbstract:A poly(dimethylsiloxane-co-(3-aminopropyl)methylsiloxane) polymer (PDMS with 20.3 mol % of (3-aminopropyl)methyl siloxane monomer) has been labeled randomly with 1-pyreneacetyl groups to generate a series of polysiloxanes (Py-PDMS) with pyrenyl contents ranging from 0.7 mol % to 5.2 mol % of the total number of structural units. The remainder of the amino groups were acetylated to avoid intra-chain quenching of the excited singlet states of pyrene via exciplex formation with free amino groups while allowing the formation of Excimers to proceed. The Fluorescence spectra and temporal decays of the Py-PDMS samples were acquired in tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and dioxane. <kMF>blob, the average rate constant for intra-chain pyrene Excimer formation, was determined from the analysis of the Fluorescence decays. <kMF>blob was found to equal 1.16 (±0.13) × 109, 1.14 (±0.12) × 109, and 0.99 (±0.10) × 109 s−1 in THF, DMF, and dioxane, respectively, at room temperature. They are the largest values found to date for any polymeric backbone in these solvents. The qualitative relationship found here between <kMF>blob and the chemical structures of the polymers indicates that the luminescence characteristics of randomly labeled polymers is a very useful method to probe the long range dynamics of chains of almost any polymer that is amenable to substitution by a lumophore
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Arborescent Poly(l‑glutamic acid)s as Standards To Study the Dense Interior of Polypeptide Mesoglobules by Pyrene Excimer Fluorescence
2018Co-Authors: Timothy Hall, Remi Casier, Mario Gauthier, Greg Whitton, Jean DuhamelAbstract:A series of arborescent poly(l-glutamic acid)s of generations 0 to 3 (PGA(GY) with Y = 0–3) were randomly labeled with 1-pyrenemethylamine to yield several Py-PGA(GY) constructs with pyrene contents ranging between 2.5 and 22 mol %. The density (ρ) of the interior of the PGA(GY) samples was estimated in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) by conducting gel permeation chromatography and dynamic light scattering experiments to determine their molar mass and hydrodynamic diameter, respectively. It was determined that ρ increased with the generation number from PGA(G1) to PGA(G2), which promoted more contacts between the pyrene labels. The increase in the number of pyrene–pyrene contacts was quantified with the parameter Nblob obtained by analysis of the Fluorescence decays for the Py-PGA(GY) samples in DMF and DMSO. In the analysis, Nblob represented the number of structural units, i.e., glutamic acid residues, comprised inside the volume probed by an exited pyrene, termed a blob. Inside a blob, pyrene Excimer formation (PEF) could occur upon diffusive encounters between an excited- and a ground-state pyrene label. It was found that Nblob increased with the generation number, and larger Nblob values were retrieved in DMSO as compared to DMF because the oligo(l-glutamic acid) (OGA) side chains in the PGA(GY) samples underwent partial loss of helicity in DMSO, which increased their hydrodynamic volume and forced the side chains closer to each other, thus resulting in more pyrene–pyrene contacts and larger Nblob values. The trends observed for Nblob in DMF as a function of the generation number could be correlated theoretically with the degree of polymerization of the OGA side chains used to prepare the PGA(GY) samples and their internal density ρ. The good agreement found between the theoretical and experimental Nblob values confirms that pyrene is an excellent probe to study the complex interior of partially structured polypeptides
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Pyrene Excimer Fluorescence as a Direct and Easy Experimental Means To Characterize the Length Scale and Internal Dynamics of Polypeptide Foldons
2018Co-Authors: Remi Casier, Jean DuhamelAbstract:This report provides evidence that the blobs characterized through the application of the Fluorescence blob model (FBM) to the analysis of the Fluorescence decays acquired with pyrene-labeled polypeptides are equivalent to the foldons used in the study of protein folding. The FBM was applied to characterize the length and time scale over which pyrene Excimer formation (PEF) took place between pyrene labels covalently attached onto α-helical and partially helical poly(l-glutamic acid) (Py-PLGA) in DMF and DMSO, respectively, and unfolded poly(dl-glutamic acid) (Py-PDLGA) in both DMF and DMSO. The blob size obtained for α-helical Py-PLGA in DMF and the characteristic time determined for the backbone dynamics of unfolded Py-PDLGA matched very closely the expected size of foldons and their characteristic folding times, respectively. In particular, the blob size was confirmed by conducting molecular mechanics optimizations (MMOs) with HyperChem. Furthermore, the level of pyrene clustering along the polypeptides correlated nicely with their expected conformation, either coiled or helical for the Py-PDLGA or Py-PLGA constructs in DMF, respectively. Consequently, these results suggest that PEF experiments conducted on pyrene-labeled polypeptides provide valuable information on the time and length scales experienced by the amino acids located inside a polypeptide blob and that if polypeptide blobs and foldons present similar length and time scales, both entities must be equivalent. Since dynamic or spatial information on foldons is usually retrieved by conducting NMR or hydrogen exchange mass spectrometry experiments, PEF might thus provide an alternative, possibly simpler, route toward the characterization of polypeptide foldons in solution
Nicholas J Turro - One of the best experts on this subject based on the ideXlab platform.
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pyrene Excimer signaling molecular beacons for probing nucleic acids
Journal of the American Chemical Society, 2008Co-Authors: Patrick Conlon, Chaoyong James Yang, Yanrong Wu, Y Chen, Karen Martinez, Nathan Stevens, Angel A Marti, Steffen Jockusch, Nicholas J TurroAbstract:Molecular beacon DNA probes, containing 1−4 pyrene monomers on the 5‘ end and the quencher DABCYL on the 3‘ end, were engineered and employed for real-time probing of DNA sequences. In the absence of a target sequence, the multiple-pyrene labeled molecular beacons (MBs) assumed a stem-closed conformation resulting in quenching of the pyrene Excimer Fluorescence. In the presence of target, the beacons switched to a stem-open conformation, which separated the pyrene label from the quencher molecule and generated an Excimer emission signal proportional to the target concentration. Steady-state Fluorescence assays resulted in a subnanomolar limit of detection in buffer, whereas time-resolved signaling enabled low-nanomolar target detection in cell-growth media. It was found that the Excimer emission intensity could be scaled by increasing the number of pyrene monomers conjugated to the 5‘ terminal. Each additional pyrene monomer resulted in substantial increases in the Excimer emission intensities, quantum yi...
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monomer and Excimer Fluorescence of horse plasma gelsolin labelled with n 1 pyrenyl iodoacetamide
Biochemistry and Cell Biology, 1992Co-Authors: Beatriz Ruiz E Silva, Leslie D. Burtnick, Edward K Koepf, Nicholas J TurroAbstract:Horse plasma gelsolin was labelled with the sulfhydryl-specific fluorescent reagent N-(1-pyrenyl)iodoacetamide. The level of incorporation of probe was 1.6 +/- 0.3 mol pyrene/mol gelsolin. The circular dichroism spectrum of pyrenyl-gelsolin and its ability to interact with muscle actin were not different from that found for unmodified gelsolin. The emission from pyrenyl-gelsolin was dominated by a broad emission band centred near 483 nm, characteristic of the presence of pyrene Excimers. Analysis of excitation spectra for the monomer and Excimer-type Fluorescence suggested that ground-state interactions may occur between adjacent pyrenes in the gelsolin structure. In the case either of Excimer formation or of ground-state pyrene-pyrene interactions in doubly labelled gelsolin molecules, the modified Cys residues must be in close proximity in the folded protein structure. Thermal denaturation of gelsolin could be monitored by observing the decrease in Excimer emission that accompanied heating and unfolding of the tertiary structure. While heat treatment alone did not eliminate Excimer Fluorescence, digestion of gelsolin with chymotrypsin completely abolished such emission. Also, pyrenyl-gelsolin prepared and studied in 6 M guanidine-HCl exhibited Fluorescence characteristic of pyrene monomers exclusively.
Juyoung Yoon - One of the best experts on this subject based on the ideXlab platform.
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unique sandwich stacking of pyrene adenine pyrene for selective and ratiometric fluorescent sensing of atp at physiological ph
Journal of the American Chemical Society, 2009Co-Authors: Zhaochao Xu, Jiten N Singh, Sungsu Park, Juyoung YoonAbstract:A pincer-like benzene-bridged sensor 1 with a pyrene Excimer as a signal source and imidazolium as a phosphate anion receptor was synthesized and investigated for ATP sensing. A unique switch of Excimer vs monomer pyrene Fluorescence of 1 is observed in the presence of ATP due to the charcteristic sandwich π−π stacking of pyrene-adenine-pyrene. On the other hand, four other bases of nucleoside triphosphates such as GTP, CTP, UTP, and TTP can interact only from the outside with the already stabilized stacked pyrene-pyrene dimer of 1, resulting in Excimer Fluorescence quenching. The fluorescent intensity ratio of monomer-to-Excimer for 1 upon binding with ATP (I375/I487) is much larger than that upon binding with ADP and AMP. This difference is large enough to discriminate ATP from ADP and AMP. As one of the biological applications, sensor 1 is successfully applied to the ATP staining experiments. Sensor 1 is also applied to monitor the hydrolysis of ATP and ADP by apyrase. The results indicate that 1 is a ...
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unique sandwich stacking of pyrene adenine pyrene for selective and ratiometric fluorescent sensing of atp at physiological ph
Journal of the American Chemical Society, 2009Co-Authors: Jiten N Singh, Sungsu Park, Jeesun Lim, Jie Pan, Ha Na Kim, Kwang S Kim, Juyoung YoonAbstract:A pincer-like benzene-bridged sensor 1 with a pyrene Excimer as a signal source and imidazolium as a phosphate anion receptor was synthesized and investigated for ATP sensing. A unique switch of Excimer vs monomer pyrene Fluorescence of 1 is observed in the presence of ATP due to the charcteristic sandwich pi-pi stacking of pyrene-adenine-pyrene. On the other hand, four other bases of nucleoside triphosphates such as GTP, CTP, UTP, and TTP can interact only from the outside with the already stabilized stacked pyrene-pyrene dimer of 1, resulting in Excimer Fluorescence quenching. The fluorescent intensity ratio of monomer-to-Excimer for 1 upon binding with ATP (I(375)/I(487)) is much larger than that upon binding with ADP and AMP. This difference is large enough to discriminate ATP from ADP and AMP. As one of the biological applications, sensor 1 is successfully applied to the ATP staining experiments. Sensor 1 is also applied to monitor the hydrolysis of ATP and ADP by apyrase. The results indicate that 1 is a useful fluorescent sensor for investigations of ATP-relevant biological processes.
Bing Yang - One of the best experts on this subject based on the ideXlab platform.
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Highly Efficient Orange-Red/Red Excimer Fluorescence from Dimeric π–π Stacking of Perylene and Its Nanoparticle Applications
2019Co-Authors: Yue Shen, Shitong Zhang, Haichao Liu, Yan Yan, Zhe Zhang, Bing YangAbstract:To achieve high-efficiency red Excimer Fluorescence, two novel perylene (PE) derivatives (mTPA-3PE and 2SF-3PE) are designed and synthesized with different monosubstituent triphenylamine (TPA) and spirofluorene (SF), respectively. The photophysical investigations reveal that mTPA-3PE and 2SF-3PE exhibit red/orange-red Excimer Fluorescence (637 and 610 nm) with long lifetimes (37.86 and 72.41 ns) in crystals but significantly different photoluminescence efficiencies (24 and 77%). Both crystal structure and excited-state property emphasize that the discreteness of the PE dimer with π–π stacking is essentially responsible for the high-efficiency Excimer emission in the crystal. Using PE as a π–π emissive core in this work, highly efficient red Excimer Fluorescence is harvested in the crystal for the first time. Moreover, their nanoparticles with the same Excimer Fluorescence exhibit the advantage of easy processing and the promising application in cell imaging. Once again, our results validate the mechanism of Excimer-induced enhanced emission (EIEE) by the discrete dimeric π–π stacking of PE in the solid state, which opens a new way to develop high-efficiency narrow band gap (e.g., near-infrared) light-emitting materials using the EIEE mechanism in the future
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Excimer formation and evolution of excited state properties in discrete dimeric stacking of an anthracene derivative a computational investigation
Physical Chemistry Chemical Physics, 2018Co-Authors: Yu Gao, Shitong Zhang, Haichao Liu, Yue Shen, Bing YangAbstract:Herein, density functional theory (DFT) computations were performed to investigate the discrete dimer of a mono-substituted anthracene derivative (2-TA-AN), which exhibited highly efficient pure Excimer Fluorescence in its crystal form. As a more practical model, its geometry, potential energy curve and excited state property were systematically calculated to better understand the Excimer formation process and photophysical properties. The compressed Excimer geometry is responsible for the highly efficient Excimer emission, arising from the enhanced rigidity that greatly suppresses its non-radiative vibrations. Potential energy curves along three directions reveal the non-uniqueness of Excimer formation along the long axis of anthracene, which is in a good agreement with the experimental findings. Upon decreasing the displacement, the intermonomer charge-transfer (CT) component gradually increased towards an approximately equivalent hybridization with the locally-emissive (LE) state of the monomer during the formation of the Excimer. The Excimer emission wavelength versus intermonomer CT content shows a similar trend along the three directions, revealing a turning point related to the essential transition of the excited state properties from the LE of the monomer to the HLCT of the Excimer. The present results will contribute to the better understanding of the structure-property relationships in Excimer formation and photophysical properties.
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discrete face to face stacking of anthracene inducing high efficiency Excimer Fluorescence in solids via a thermally activated phase transition
Journal of Materials Chemistry C, 2017Co-Authors: Yue Shen, Shitong Zhang, Haichao Liu, Yu Gao, Yan Yan, Lijuan Zhao, Bing YangAbstract:It is always a challenge for planar polycyclic aromatic molecules to achieve high efficiency in solids owing to their frequent encounter with aggregation-caused quenching (ACQ). An anthracene derivative with one-side meta-substituted triphenylamine (TPA) was found to show high-efficiency Excimer Fluorescence (ηPL = 76.8%) in G-phase (green) crystals as well as a long lifetime, in sharp contrast with that of a monomer in a doped film (ηPL = 36.6%) and that of B-phase (blue) crystals (ηPL = 8.1%). In essence, the Excimer-induced enhanced emission can be ascribed to the special intermolecular stacking in the solid state, namely, discrete antiparallel dimeric stacks between anthracene moieties in G-phase crystals, which are responsible for greatly suppressed non-radiative deactivation due to a uniform emissive state preventing the formation of an energy-trapping “dark” state. Moreover, a G-phase could be obtained through a thermally-activated phase transition from B-phase crystals, corresponding to the completely synchronized change of Fluorescence properties. The present results consolidate a novel strategy of designing discrete dimeric stacking of planar polycyclic aromatic molecules to achieve high-efficiency Fluorescence in the solid state by an Excimer-induced enhanced emission (EIEE) mechanism.
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Excimer-induced high-efficiency Fluorescence due to pairwise anthracene stacking in a crystal with long lifetime
Chem. Commun., 2016Co-Authors: Haichao Liu, Xiankai Chen, Liang Yao, Bao Li, Shitong Zhang, Weijun Li, Bing Yang, Ping Lu, Yu Gao, Yuguang MaAbstract:Herein, we report an anthracene-based material, 2-(anthracen-9-yl)thianthrene (2-TA-AN), whose crystal exhibits Excimer Fluorescence with an unexpected high luminous efficiency (up to 80%) and long lifetime (163.75 ns), due to pairwise anthracene stacking. These results will update the traditional view that Excimers are poorly efficient in photoluminescence.
Frank Seela - One of the best experts on this subject based on the ideXlab platform.
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a ratiometric fluorescent on off zn2 chemosensor based on a tripropargylamine pyrene azide click adduct
Journal of Organic Chemistry, 2012Co-Authors: Sachin A Ingale, Frank SeelaAbstract:A new, easy-to-prepare and highly selective pyrene-linked tris-triazole amine fluorescent chemosensor has been designed from tripropargylamine and pyrene azide using Cu(I)-catalyzed click chemistry. The Fluorescence on–off sensor 1 is highly selective for Zn2+ displaying a ratiometric change in emission. The relative intensity ratio of monomer to Excimer Fluorescence (M376/E465) of the sensor increases 80-fold upon the addition of 10 equiv of Zn2+ ions (with a detection limit of 0.2 μM).
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7 deazapurine and 8 aza 7 deazapurine nucleoside and oligonucleotide pyrene click conjugates synthesis nucleobase controlled Fluorescence quenching and duplex stability
Journal of Organic Chemistry, 2012Co-Authors: Sachin A Ingale, Suresh S Pujari, Venkata Ramana Sirivolu, Ping Ding, Hai Xiong, Hui Mei, Frank SeelaAbstract:7-Deazapurine and 8-aza-7-deazapurine nucleosides related to dA and dG bearing 7-octadiynyl or 7-tripropargylamine side chains as well as corresponding oligonucleotides were synthesized. “Click” conjugation with 1-azidomethyl pyrene (10) resulted in fluorescent derivatives. Octadiynyl conjugates show only monomer Fluorescence, while the proximal alignment of pyrene residues in the tripropargylamine derivatives causes Excimer emission. 8-Aza-7-deazapurine pyrene “click” conjugates exhibit Fluorescence emission much higher than that of 7-deazapurine derivatives. They are quenched by intramolecular charge transfer between the nucleobase and the dye. Oligonucleotide single strands decorated with two “double clicked” pyrenes show weak or no Excimer Fluorescence. However, when duplexes carry proximal pyrenes in complementary strands, strong Excimer Fluorescence is observed. A single replacement of a canonical nucleoside by a pyrene conjugate stabilizes the duplex substantially, most likely by stacking interacti...
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parallel stranded oligonucleotide duplexes containing 5 methylisocytosine guanine and isoguanine cytosine base pairs
Tetrahedron, 1999Co-Authors: Frank Seela, C WeiAbstract:Abstract Parallel-stranded oligonucleotides containing 5-methylisocytosine-guanine and/or isoguanine-cytosine base pairs were prepared. The coupling efficiency was higher than 99% when the phosphoramidites of 2′-deoxy-5-methylisocytidine (2a) and of 2′-deoxyisoguanosine (3) were employed in solid-phase synthesis. The glycosylic bond of 2′-deoxy-5-methylisocytidine (1a) is stabilized against acid in the case of the amidine derivatives 4a, b. Depyrimidination occurs upon extended exposure to ammonia. The orientation of the parallel-stranded (ps) duplexes was unambiguously determined using the pyrene Excimer Fluorescence. The antiparallel (aps) duplex d(A12)•d(T12) (25•26) turned into the parallel orientation when two central adenine-thymine base pairs were replaced by isoguanine-cytosine pairs. The thermal stability of ps-duplexes containing 5-methylisocytosine-guanine base pairs was found to be significantly lower than that of duplexes with isoguanine-cytosine pairs. According to the CD spectra, ps-DNA-DNA or DNA-RNA hybrids show differences in their secondary structures compared to their aps counterparts.
