Polyaromatic Profluorescent Nitroxide Probes with Enhanced Photostability

Novel profluorescent mono‐ and bis‐isoindoline nitroxides linked to napthalimide and perylene diimide structural cores are described. These nitroxide‐fluorophore probes display strongly suppressed fluorescence in comparison to their corresponding non‐radical diamagnetic methoxyamine derivatives. The perylene‐based probe possessing two isoindoline systems tethered through ethynyl linkages was shown to be the most photostable in solution, demonstrating significantly enhanced longevity over the 9,10‐bis(phenylethynyl)anthracene fluorophore used in previous profluorescent nitroxide probes.     

The local anaesthetic tetracaine as a quencher of perylene fluorescence in micelles

At neutral pH the local anaesthetic tetracaine hydrochloride quenches the fluorescence of the lipophilic dye perylene incorporated into non-ionic micelles. The process follows the Stern-Volmer equation, suggesting that quenching occurs through encounter of fluorophore and quencher. As the pH is lowered from 5 to 1, the apparent quenching constant decreases sigmoidally, the midpoint of the curve being at pH 2.3, close to the pK value characterizing the ionization of the anaesthetic aromatic butylamino group. Quenching is completely reversed below pH 1. These results show that the ability of tetracaine to quench the fluorescence of perylene incorporated into micelles depends on the absence of charge on its aromatic amine. Quenching was also studied in homogeneous dioxane-water solution. In this system the quenching constant also decreases sigmoidally as the pH is lowered. The infection point of the curve is nearly coincident with the pK of tetracaine butylamino group in the same partially non-aqueous medium. Protonation of this group induces 60% reversal of the quenching, suggesting that the main mechanism of fluorescence extinction could be the electron transfer from unprotonated tetracaine aromatic amine to perylene in the excited state. However, an additional process which remains operative even when such an amino group is positively charged must also be involved. It can be concluded that the complete reversal of tetracaine quenching of perylene fluorescence in micelles induced by low pH is due to the inability of the anaesthetic to become partitioned into micelles upon protonation of its aromatic amine. In contrast, at neutral pH the local anaesthetic is able to reach the micelle non-polar core where perylene is located. This is consistent with the models, suggesting that the membrane-bound tetracaine assumes a rod-like configuration parallel to the surface normal with the aromatic butylamino group located into a highly hydrophobic region.     

Design,photochemistry and antibacterial evaluation of novel light-harvesting antenna

Abstract

Novel light-harvesting compound 6, based on 1,8-naphthalimide donors and perylenediimide acceptor were synthesized. The light-harvesting compound 6 showed intensive absorption band in range between 390 and 560?nm, that is 50?nm wider in comparison with the absorption of the model perylene dye. The novel antenna 6 has a higher ability to collect photons from environment in comparison with the single perylene diimide dyes. The chosen fluorophore units are suitable donor–acceptor pair for light-harvesting materials which was in agreement with their good antibacterial activity.     

Evaluation of pyrimido[5,4-d]pyrimidine derivatives as peroxyoxalate chemiluminescence reagents using a flow injection system

Eighteen kinds of pyrimido[5,4-d]pyrimidines together with several commercially available fluorescent compounds such as perylene, Rhodamine B, etc., were evaluated as the reagents for a peroxyoxalate chemiluminescence (CL) detection system by using a flow injection method. The peroxyoxalate CL reaction employed consists of bis(2,4,6-trichlorophenyl)oxalate, hydrogen peroxide, triethylamine, and a fluorophore. Under the conditions used, 2,6-bis[di-(2-hydroxyethyl)amino]-4,8- dipiperidinopyrimido[5,4-d]pyrimidine (Dipyridamole) and 2,4,6,8-tetrathiomorpholinopyrimido[5,4-d]pyrimidine (1i) gave very intense chemiluminescence intensities which were larger than those of any other commercially available fluorescent compounds tested (e.g., 10 times larger than that of perylene).     

A highly selective and sensitive perylenebisimide-based fluorescent PET sensor for Al determination in MeCN

A novel ‘turn-on’ fluorescent probe with perylene tetracarboxylic bisimide (PBI) as the fluorophore and di(2-(salicylideneamino))ethylamine (DSEA) as the metal ion receptor was designed. The capability of the prepared probe to detect metal ions was evaluated by the changes in its emission intensity. The probe demonstrated a considerable emission enhancement (ca. 110-fold) in the presence of Al³⁺ in MeCN with high selectivity and sensitivity. Furthermore, the considerably ‘off–on’ fluorescence response concomitantly led to the apparent color change from colorless to brilliant yellow, which could also be identified by naked eye easily under UV lamp.     

Synthesis and characterization of dually labeled Pickering-type stabilized polymer nanoparticles in a downscaled miniemulsion system

Dual fluorescently labeled polymer particles were prepared in a downscaled Pickering-type miniemulsion system. Stable dispersions were obtained and the size of the hybrid particles could be varied between ca. 180 and 430 nm. Silica nanoparticles were employed as sole emulsifier, which were labeled by a fluorescein dye (FITC) or (encapsulated) quantum dots, and the polymer core was labeled by a perylene derivative. Downscaling of the Pickering-type miniemulsion system is intriguing by itself as it allows the use of precious nanoparticles as emulsifiers. Here, silica particles with a fluorescent core and an overall diameter between 20 and 40 nm were prepared and employed as stabilizer. The dual excitation and emission of both dyes was tested by fluorescence measurements and confocal laser scanning microscopy (cLSM).     

Artificial DNAs based on alkynyl C-nucleosides as a superior scaffold for homo- and heteroexcimer emissions

DNA-like fluorescent oligomers composed of alkynyl beta-D-ribofuranosides bearing pyrene, perylene, and anthracene as a fluorophore were synthesized by solid-phase DNA synthesis. The fluorescent oligomers possess the defined number and order of the fluorophores. In these oligomers, the adjacent fluorophores efficiently interact with each other by hydrophobic interactions in their electronic ground states in a face-to-face fashion. The predominant excimer emissions were observed from not only the homooligomers (pyrene-pyrene and perylene-perylene systems) but also the heterooligomers (pyrene-perylene, pyrene-anthracene, and perylene-anthracene systems) in aqueous media.     

Analytical applications of peroxyoxalate chemiluminescence

Peroxyoxalate chemiluminescence can be applied to the determination of hydrogen peroxide and aromatic hydrocarbon fluorophores in a static system. Hydrogen peroxide causes a linear response in the range 10^-6–10^-1M when bis(2,4,6-trichlorophenyl) oxalate is used with perylene as the fluorophore. As the intensity of chemiluminescence from different aromatic hydrocarbons varies substantially, there is a degree of selectivity in their determination. If metal chelates are employed as fluorophores, trace metal analysis is possible.     

敏化光解 盐的研究——蒽、芘、 电子转移荧光猝灭

本文采用稳态和瞬态光谱方法研究了四种二苯基碘 盐(Ph~2I^+X^-)对蒽、芘、 的激发态的猝灭作用, 通过Stern-Volmer方程确定了它们的光致电子转移速度常数。结果表明Ph~2I^+AsF^-~6对荧光猝灭是最有效的, 猝灭过程是扩散控制的。比较荧光强度和荧光寿命测定得到的猝灭常数, 表明猝灭是动态过程, 敏化剂与 盐间没有基态复合物生成。     

Chemiluminescence of bis(2,4,6-trichlorophenyl) oxalate in aqueous micellar systems

The chemiluminescent reaction of bis(2,4,6-trichlorophenyl) oxalate (TCPO) in aqueous micellar systems is compared with the reaction in a mixture of acetonitrile and aqueous phosphate buffer. The chemiluminescence was studied in batch experiments with perylene as the fluorophore. The oxidation of TCPO produced the same intensity of chemiluminescence in the buffered acetonitrile as in Arkopal N-300 micelles, the best micellar system. The solubility of TCPO in an aqueous micellar system is greater than that in the acetonitrile/aqueous buffer (80:20, v/v), but TCPO is less stable in the former system.     

Carbon Nanotube‐Enhanced Polarization of Fluorescent Peptides: A Novel Amplification Strategy for Homogeneous Detection of Proteases

A new fluorescence polarization (FP) amplification strategy based on the use of multiwalled carbon nanotubes (MWCNTs) as the FP enhancer was developed for the simple, sensitive, and universal monitoring of protease activity in homogeneous solution. A fluorophore‐labeled peptide that includes a protease‐cleavable element and ten histidine residues for binding MWCNTs is adsorbed on MWCNTs through strong π–π stacking and electrostatic interactions. When the fluorophore‐labeled peptide/MWCNT complexes are exposed to a protease target, specific peptide cleavage by the protease target occurs, thus releasing fragments carrying the fluorophore from the surface of MWCNTs, which in turn results in a significant decrease in the FP value. The detection limits of this assay for two proteases, thrombin and chymotrypsin (CTP), were estimated to be 0.5 pM and 0.3 pM , respectively. In addition, it is also demonstrated that this MWCNT‐enhanced FP assay is suitable for protease inhibitor screening.     

Star-shaped fluorescent polypeptides

Two series of novel, four-arm, star-shaped polypeptides were prepared via the ring-opening polymerization of γ-benzyl-L -glutamate N-carboxyanhydride and ϵ-benzyloxycarbonyl-L -lysine N-carboxyanhydride with a tetra-amino-substituted perylene fluorophore as the initiator. The removal of the α-amino acid side-chain-protecting groups resulted in unprecedented water-soluble, perylene-functionalized, star-shaped polypeptides that showed strong fluorescence in aqueous solution. One of the features that distinguished these water-soluble star polypeptides from most other star polymers was that the conformation of the arms could be reversibly changed from a random coil into an α helix by variations in the pH of the aqueous solution. These star polypeptides might be of interest for the development of novel fluorescent probes or as traceable, stimuli-sensitive molecular containers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1572–1583, 2001     

Detection of three-base deletion by exciplex formation with perylene derivatives

Here, we synthesized fluorescent DNA probes labeled with two perylene derivatives for the detection of a three-base deletion mutant. One such probe discriminated the three-base deletion mutant from the wild-type sequence by exciplex emission, and the deletion mutant was identifiable even by the naked eye.     

Continuous, on-line DNA sequencing using a versatile infrared laser scanner/electrophoresis apparatus.

A new apparatus for continuously detecting fluorescently labeled DNA fragments is based on infrared fluorescence technology. This technology combines state-of-the-art developments in chemistry, laser technology, and detection, while achieving improved reliability, sensitivity, and flexibility for applications including DNA sequencing. DNA molecules labeled with a novel infrared fluorophore are detected during electrophoresis using a scanning infrared fluorescence microscope. The microscope consists of a laser diode for exciting the fluorophore and a silicon avalanche photodiode for detecting the infrared emission. Optimum conditions for detection and throughput are obtained by adjusting electrophoresis, scanning and imaging parameters. Typical DNA sequencing runs (test templates) allow identification of over 500 bases per sample with greater than 99% accuracy.     

Rational Design for Cooperative Recognition of Specific Nucleobases Using β‐Cyclodextrin‐Modified DNAs and Fluorescent Ligands on DNA and RNA Scaffolds

We propose a binary fluorimetric method for DNA and RNA analysis by the combined use of two probes rationally designed to work cooperatively. One probe is an oligonucleotide (ODN) conjugate bearing a β‐cyclodextrin (β‐CyD). The other probe is a small reporter ligand, which comprises linked molecules of a nucleobase‐specific heterocycle and an environment‐sensitive fluorophore. The heterocycle of the reporter ligand recognizes a single nucleobase displayed in a gap on the target labeled with the conjugate and, at the same time, the fluorophore moiety forms a luminous inclusion complex with nearby β‐CyD. Three reporter ligands, MNDS (naphthyridine–dansyl linked ligand), MNDB (naphthyridine–DBD), and DPDB (pyridine–DBD), were used for DNA and RNA probing with 3′‐end or 5′‐end modified β‐CyD – ODN conjugates. For the DNA target, the β‐CyD tethered to the 3′‐end of the ODN facing into the gap interacted with the fluorophore sticking out into the major groove of the gap site ( MNDS and DPDB ). Meanwhile the β‐CyD on the 5′‐end of the ODN interacted with the fluorophore in the minor groove ( MNDB and DPDB ). The results obtained by this study could be a guideline for the design of binary DNA/RNA probe systems based on controlling the proximity of functional molecules.     

Self-assembly and characterization of hydrogen-bond-induced nanostructure aggregation.

A supramolecular system of a perylene derivative containing bis(2,6-diacylaminopyridine) units and a perylene bisimide bound through three hydrogen-bonds was synthesized and characterized. 1H NMR spectra confirmed the existence of hydrogen-bonding interactions between the perylene derivative (3) and the perylene bisimide (7). The photocurrent generation of the self-assembled 3.7 film was measured, and a cathodic photocurrent response was obtained. SEM images indicated that well-defined long fibers could be fabricated by self-assembly, by exploiting the hydrogen bonding interactions and pi-pi stacking interactions of perylene rings.     

Capture and detection of a quencher labeled oligonucleotide by poly(phenylene ethynylene) particles

Fluorescence quenching of poly(phenylene ethynylene) (PPE) particles by a Cy-5 labeled oligonucleotide is 2 orders of magnitude more sensitive than direct excitation of the Cy-5 fluorophore.     

Synthesis and characterization of 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole functionalized tetraaryloxy perylene bisimide and metal-directed self-assembly

[structure: see text] New perylene bisimide dyes bearing 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole receptor units with different spacers have been synthesized and characterized. The fluorescence and electronic properties of these compounds have been studied. MALDI-TOF, UV-vis, and fluorescence titration experiments proved that monotopic perylene bisimide ligands could be assembled into dimmers by Fe(III) coordination. The coordination properties of the ditopic perylene bisimide ligands have also been studied preliminarily. Furthermore, the SEM images indicated that well-defined nanoscale structures could be fabricated by self-assembly due to metal ion coordination and pi-pi stacking interactions of perylene rings with the help of a proper spacer.     

High sensitivity separation and detection of heparan sulfate disaccharides

Eight Delta-disaccharide standards from heparan sulfate/heparin were derivatized with the fluorophore 4,4-difluoro-5,7- dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionic acid, hydrazide (BODIPY) via formation of a Schiff's base and separated using HPAEC on a Propac PA1 column with a linear salt gradient and isocratic 150 mM NaOH. Detection was with an in-line fluorescence detector. The standard deviation (sigma(n-1)) in retention times were 0.7-2% over nine runs. The limit of detection, was 100 fmol (100 x 10(-15)mol) of BODIPY labeled Delta-disaccharides, representing considerably improved detection compared to other fluorophore labeled derivatives and, unlike these, required no further purification steps. Separation and improved detection of BODIPY-Delta-disaccharide conjugates will assist the structural analysis of HS and the development of improved sequencing methodologies.     

Fluorescent sensing ochratoxin A with single fluorophore-labeled aptamer

We explored a fluorescent strategy for sensing ochratoxin A (OTA) by using a single fluorophore-labeled aptamer for detection of OTA. This method relied on the change of the fluorescence intensity of the labeled dye induced by the specific binding of the fluorescent aptamer to OTA. Different fluorescein labeling sites of aptamers were screened, including the internal thymine bases, 3′-end, and 5′-end of the aptamer, and the effect of the labeling on the aptamer affinity was investigated. Some fluorophore-labeled aptamers showed a signal-on or signal-off response. With the fluorescent aptamer switch, simple, rapid, and selective sensing of OTA at nanomolar concentrations was achieved. OTA spiked in diluted red wine could be detected, showing the feasibility of the fluorescent aptamer for a complex matrix. This method shows potential for designing aptamer sensors for other targets.