Chromophore Moieties Research Articles

Convenient Attachment of Highly Polar Azo Chromophore Moieties to Disubstituted Polyacetylene through Polymer Reactions by Using “Click” Chemistry

Convenient Attachment of Highly Polar Azo Chromophore Moieties to Disubstituted Polyacetylene through Polymer Reactions by Using “Click” Chemistry

Tumor Targeting with Antibody-Functionalized, Radiolabeled Carbon Nanotubes

Single-walled carbon nanotubes (CNT) are mechanically robust graphene cylinders with a high aspect ratio that are comprised of sp(2)-bonded carbon atoms and possessing highly regular structures with defined periodicity. CNT exhibit unique mechanochemical properties that can be exploited for the development of novel drug delivery platforms. We hypothesized that novel prototype nanostructures consisting of biologics, radionuclides, fluorochromes, and CNT could be synthesized and designed to target tumor cells. Tumor-targeting CNT constructs were synthesized from sidewall-functionalized, water-soluble CNT platforms by covalently attaching multiple copies of tumor-specific monoclonal antibodies, radiometal-ion chelates, and fluorescent probes. The constructs were characterized spectroscopically, chromatographically, and electrophoretically. The specific reactivity of these constructs was evaluated in vitro by flow cytometry and cell-based immunoreactivity assays and in vivo using biodistribution in a murine xenograft model of lymphoma. A soluble, reactive CNT platform was used as the starting point to build multifunctional constructs with appended antibody, metal-ion chelate, and fluorescent chromophore moieties to effect specific targeting, to carry and deliver a radiometal-ion, and to report location, respectively. These nanoconstructs were found to be specifically reactive with the human cancer cells they were designed to target in vivo in a model of disseminated human lymphoma and in vitro by flow cytometry and cell-based immunoreactivity assays versus appropriate controls. The key achievement in these studies was the selective targeting of tumor in vitro and in vivo by the use of specific antibodies appended to a soluble, nanoscale CNT construct. The ability to specifically target tumor with prototype-radiolabeled or fluorescent-labeled, antibody-appended CNT constructs was encouraging and suggested further investigation of CNT as a novel delivery platform.

Characterization of NcsB2 as a Promiscuous Naphthoic Acid/Coenzyme A Ligase Integral to the Biosynthesis of the Enediyne Antitumor Antibiotic Neocarzinostatin

The enediyne antitumor antibiotic neocarzinostatin (NCS) is produced by Streptomyces carzinostaticus ATCC15944. The biosynthetic pathway for the naphthoic acid moiety (boxed) of the NCS chromophore (1) is proposed to comprise five enzymes: NcsB, NcsB1, NcsB2, NcsB3, NcsB4. Both in vivo and in vitro experiments were used to support the proposed pathway. NcsB2 was characterized for the ability to catalyze the activation of 2-hydroxy-7-methoxy-5-methyl-1-naphthoic acid (3) via a naphthoyl-AMP ester (5) and subsequent formation of the corresponding coenzyme A ester. The finding that NcsB2 exhibits promiscuous substrate specificity toward a diverse set of naphthoic acid analogues with 2-, 5-, or 7-substitutions presents an outstanding opportunity to produce novel analogues of 1 by engineering NCS biosynthesis.

Triplet Reactivity and Regio-/Stereoselectivity in the Macrocyclization of Diastereomeric Ketoprofen−Quencher Conjugates via Remote Hydrogen Abstractions

Intramolecular excited triplet state interactions in diastereomeric compounds composed of a benzophenone chromophore (ketoprofen) and various hydrogen donor moieties (tetrahydrofuran, isopropylbenzene) have been investigated by laser flash photolysis. The rate constants for hydrogen abstraction by excited triplet benzophenone are in the order of 10(4)-10(5) s(-1), with the highest reactivity for the tetrahydrofuran residue. A remarkable diastereodifferentiation, expressed in the triplet lifetimes of the carbonyl chromophore (e.g., 1.6 versus 2.7 micros), has been found for these compounds. With an alkylaromatic moiety as donor, related effects have been observed, albeit strongly dependent on the length of the spacer. The reactivity trend for the initial hydrogen transfer step is paralleled by the quantum yields of the overall photoreaction. The biradicals, formed via remote hydrogen abstraction, undergo intramolecular recombination to macrocyclic ring systems. The new photoproducts have been isolated and characterized by NMR spectroscopy. The stereochemistry of the macrocycles, which contain up to four asymmetric carbons, has been unambiguously assigned on the basis of single-crystal structures and/or NOE effects. Interestingly, a highly regio- and stereoselective macrocyclization has been found for the ketoprofen-tetrahydrofuran conjugates, where hydrogen abstraction from the less substituted carbon is exclusive; cisoid ring junction is always preferred over the transoid junction. The photoreaction is less regioselective for compounds with an isopropylbenzene residue. The reactivity and selectivity trends have been rationalized by DFT (B3LYP/6-31G*) calculations.

Controlling nonlinear optical effects of polyurethanes by adjusting isolation spacers through facile postfunctional polymer reactions

With the aim to control nonlinear optical (NLO) effects of polyurethanes, especially to efficiently translate the fixed μβ values of the organic chromophore to possibly higher macroscopic NLO activities of polymers, a facile synthetic strategy, consisting of the postazo coupling and esterification reactions, was developed to prepare a series of second-order nonlinear optical polyurethanes ( P2– P5). And in the polymers, different isolation groups were introduced to the sulfonyl-based chromophore moieties at the acceptor side. Thus, polyurethane P1 containing aniline groups was obtained from the copolymerization of 2,4-toluenediisocyanate (TDI) and N, N-2-(2-hydroxyethyl)aniline directly; then a postazo coupling reaction of p-(2-hydroxyethyl)sulfonylbenzenediazonium fluoroborate toward the aniline ring afforded the sulfonyl-based chromphore-functionalized polyurethane P2, which underwent the subsequent esterification reactions between the hydroxyl groups in P2 and different organic acids to link different isolation spacers (changing from small groups to much larger ones such as carbazolyl groups), to the chromophore moieties at the acceptor side, to yield polyurethanes P3, P4 and P5. The polymers exhibit good solubility in common organic solvents and are thermally stable. The maximum absorption appeared at about 436 nm with a cutoff at ca. 570 nm, resulting in a wider transparency window. The tested NLO properties demonstrate that the resonant d 33 values of polymers could be improved about 1.5 times by attaching isolation spacers with suitable bulkiness.

Proton Transfer and Associated Molecular Rearrangements in the Photocycle of Photoactive Yellow Protein: Role of Water Molecular Migration on the Proton Transfer Reaction

The mechanism of the proton transfer and the concomitant molecular structural and hydrogen bond rearrangements after the photoisomerization of the chromophore in the photocycle of photoactive yellow protein are theoretically investigated by using the QM/MM method and molecular dynamics calculations. The free energy surface along this proton-transfer process is determined. This work suggests the important role of the water molecular migration into the moiety of chromophore, which facilitates proton transfer by the hydrogen bond rearrangement and the hydration of the pB' state.

Synchronous Photoinitiation of Endothelial NO Synthase Activity by a Nanotrigger Targeted at Its NADPH Site

We designed a new nanotrigger to synchronize and monitor an enzymatic activity interacting specifically with the conserved NADPH binding site. The nanotrigger (NT) combines a docking moiety targeting the NADPH site and a chromophore moiety responsive to light excitation for efficient electron transfer to the protein. Specific binding of the nanotrigger to the reductase domain of the endothelial nitric oxide synthase (eNOSred) was demonstrated by competition between NADPH and the nanotrigger on the reduction of eNOSred flavin. A micromolar Ki was estimated. We had monitored initiation of eNOSred activity by ultrafast transient spectroscopy. The transient absorption spectrum recorded at 250 ps fits the expected sum of the reduced and oxidized species, independently obtained by other chemical methods, in agreement with a photoinduced electron transfer from the excited nanotrigger to the flavin moiety of eNOSred. The rate of electron transfer from the excited state of the nanotrigger (NT*) to the protein is estimated to be k(ET) = (7 +/- 2) x 10(9) s(-1) using the decay of oxidized eNOSred-bound nanotrigger compared against prereduced eNOSred or glucose 6-P dehydrogenase as controls. This fast electron transfer bypasses the slow hydride transfer to initiate NOS catalysis as shown by ultrafast kinetics using the eNOSred mutated in the regulatory F1160 residue. The selective targeting of the nanotrigger to NADPH sites should allow controlled initiation of the enzymatic activity of numerous proteins containing an NADPH site.

Synthesis and nonlinear optical properties of polyphosphazenes with binaphtholyl and indole side groups

AbstractNew polyphosphazenes (P2 and P3) that contain indole‐based chromophore and binaphtholyl moieties as side chains are prepared by a new postfunctional strategy. Molecular structural characterization for the high polymers was presented by 1H‐NMR, IR and UV‐Visible spectra, gel permeation chromatograply, and differential scanning calorimetry. The glass transition temperature of P2 was determined to be 168°C, higher than those polyphosphazenes reported previously in the literatures. P2 and P3 are thermal stable and easily soluble in high polar solvents. The maximum absorption of P2 in chloroform was at 425 nm and cuts off at about 550 nm, while that of P3 was 393 nm and 500 nm, respectively, which resulted in a wide transparency window. The poled films of P2 and P3 reveal a resonant d33 value of 20 pm/V and 14 pm/V, respectively, by second harmonic generation measurements. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 365–371, 2007

Synthesis of colorimetric sensors for isomeric dicarboxylate anions: selective discrimination between maleate and fumarate

Four new colorimetric receptors (1-4) were synthesized and characterized. Upon addition of maleate to receptor in DMSO, the appearance of the solution of receptor 1 showed a color change from dark-blue to dark-red, which can be detected by the naked eye at parts per million. Similar experiments were repeated using receptors 2-4; the solution showed a distinct color change from blue to violet for receptor 2 and from blue-green to purple for both receptors 3 and 4, when they are formed as complexes with maleate. The striking color changes are thought to be due to the deprotonation of the thiourea moiety of the 4-nitronaphthyl chromophore. Whereas, in the addition of fumarate to receptors 1-4, the color of the solution changed from dark-blue to bright yellow for receptor and did not induce any color change for receptors 2-4. Thus, for a distinct color change, receptors 1-4 can act as optical chemosensors for recognition of maleate versus fumarate. Especially, only receptor 1 has a unique color change for the recognition of fumarate, accordingly it can be used for detection of the fumarate anion. In this research it was also found that the performance of the receptor is highly dependent on the substituent group on the phenyl ring; a stronger electron-withdrawing group resulted in a receptor with a higher binding constant with the maleate anion.

1-(Bromoacetyl)pyrene, a novel photoinitiator for the copolymerization of styrene and acrylonitrile

A comparative study on photoinitiated solution copolymerization of Styrene (Sty), with acrylonitrile (AN) using pyrene, 1-acetylpyrene, and 1-(bromoacetyl)pyrene (BrPy) as initiators, showed that the introduction of a chromophoric moiety, bromoacetyl (–COCH2Br), significantly increased the photoinitiating ability of pyrene. The kinetics and mechanism of copolymerization of Sty with AN (Sty–co–AN) using BrPy as photoinitiator has been studied in detail. The kinetic data, inhibiting effect of benzoquinone, and electron spin resonance (ESR) studies suggest that the polymerization proceeds via a free radical mechanism. The system followed non-ideal kinetics (R p α[BrPy]0.7[Sty]1.09[AN]1.01) and degradative solvent transfer reasonably explained these kinetic non-idealities. The co-monomer reactivity ratios calculated by using the Finemann–Ross and Kelen–Tudos models were r 1 (Sty) = 0.39 and r 2 (AN) = 0.05. The reactivity ratios strongly indicate that the two monomers enter in almost alternating arrangement along the copolymer chain.

An Attempt To Modify Nonlinear Optical Effects of Polyurethanes by Adjusting the Structure of the Chromophore Moieties at the Molecular Level Using “Click” Chemistry

ADVERTISEMENT RETURN TO ISSUEPREVNoteAn Attempt To Modify Nonlinear Optical Effects of Polyurethanes by Adjusting the Structure of the Chromophore Moieties at the Molecular Level Using “Click” ChemistryZhong'an Li, Qi Zeng, Zhen Li, Shoucheng Dong, Zhichao Zhu, Qianqian Li, Cheng Ye, Chong'an Di, Yunqi Liu, and Jingui QinView Author Information Hubei Key Lab on Organic and Polymeric Opto-Electronic Materials, Department of Chemistry, Wuhan University, Wuhan 430072, China, and Organic Solids Laboratories, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, China Cite this: Macromolecules 2006, 39, 24, 8544–8546Publication Date (Web):November 7, 2006Publication History Received12 August 2006Revised22 September 2006Published online7 November 2006Published inissue 1 November 2006https://doi.org/10.1021/ma061854sCopyright © 2006 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1016Altmetric-Citations80LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (52 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Chromophores,Isolation,Nonlinear optics,Polymers,Quantum mechanics Get e-Alerts

Photochemical Reactions of 1,3,3‐Trimethylbicyclo[2.2.2]octa‐5,7‐dien‐2‐ones

AbstractThe photochemistry of 1,3,3‐trimethylbicyclo[2.2.2]octa‐5,7‐dien‐2‐ones 1a–f containing multiple chromophoric moieties under various conditions is described. Upon direct irradiation, dienones 1a–f in benzene, acetonitrile, and methanol were found to aromatize through photoelimination of dimethylketene, which was trapped with 3‐phenylprop‐2‐en‐1‐ol (12). Triplet sensitization of dienone 1a in acetone and in acetone/acetophenone mixed solvents afforded aromatic compound 2a, whilst bicyclic systems 1b–c were found to be unreactive on sensitization. In the cases of dienones 1d–f in acetone, aromatic compounds 2d–f and di‐π‐methane (DPM) photoproducts 3d–f and 4f were observed, but in the acetone/acetophenone mixed solvent system only DPM photoproducts were detected. Plausible mechanisms for these photochemical reactions are described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Structural Control of the Side-Chain Chromophores To Achieve Highly Efficient Nonlinear Optical Polyurethanes

Two series of polyurethanes (P1−P10) containing NLO chromophores as side chains were prepared, in which the size of isolation groups was changed from small atoms to much larger groups such as carbazolyl groups. The polymers were well characterized. The tested NLO properties of the polymers demonstrate that the NLO values and the poling efficiency of the polymers are not always improved with increasing of the size of isolation spacer, and for a given chromophore moiety, there is a suitable isolation group present to boost its microscopic β value to possibly higher macroscopic NLO property efficiently.

Copolymerization of n‐butylacrylate with styrene by a novel photoinitiator, 1‐(bromoacetyl)pyrene

AbstractA comparative study on photoinitiated solution copolymerization of n‐butylacrylate (BA) with styrene (Sty) using pyrene (Py), 1‐acetylpyrene (AP), and 1‐(bromoacetyl)pyrene (BP) as initiators showed that the introduction of a chromophoric moiety, bromoacetyl (COCH2Br), significantly increased the photoinitiating ability of pyrene. The kinetics and mechanism of copolymerization of BA with Sty using BP as photoinitiator have been studied in detail. The system follows nonideal kinetics (Rp ∝ [BP]0.34 [BA]1.07 [Sty]0.97). The nonideality was attributed to both primary radical termination and degradative initiator transfer. The monomer reactivity ratios of Sty and BA have been estimated by the Finemann–Ross and Kelen–Tudos methods, by analyzing copolymer compositions determined by 1H NMR spectra. The values of r1 (Sty) and r2 (BA) were found to be 0.78 and 0.25, respectively, which suggested the high concentration of alternating sequences in the random copolymers obtained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3233–3239, 2006

Atom transfer radical polymerization of styrene with 2‐(1‐bromoethyl)‐anthraquinone as an initiator

Abstract2‐(1‐Bromoethyl)‐anthraquinone (BEAQ) was successfully used as an initiator in the atom transfer radical polymerization of styrene with CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as the catalyst at 110°C. The polymerizations were well controlled with a linear increase in the molecular weights (Mn's) of the polymers with monomer conversion and relatively low polydispersities (1.1 < weight‐average molecular weight (Mw)/Mn < 1.5) throughout the poly merizations. The resultant polystyrene thus possessed one chromophore moiety (2‐ethyl‐anthraquinone) at the α end and one bromine atom at the ω end, both from the initiator BEAQ. The intensity of UV absorptions of the resultant polymers decreased with increasing molecular weights of the polymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2081–2085, 2006

Large Cross-Section Enhancement and Intramolecular Energy Transfer upon Multiphoton Absorption of Hindered Diphenylaminofluorene-C60 Dyads and Triads

Sterically hindered fullerenyl chromophore dyad and triads, C60(>DPAF-C9)x (x = 1 and 2, respectively), in an acceptor−donor (A−D) molecular linkage of C60-(keto-fluorene)x were synthesized and fully characterized. Attachment of two 3,5,5-trimethylhexyl groups on C9 of the fluorene ring moiety greatly improves their solubility and makes direct intermolecular aromatic stacking contacts more difficult. They are the first series of fullerene derivatives showing high three-photon absorptivity (3PA). Accordingly, C60(>DPAF-C9)2 exhibits 2PA and 3PA cross sections in the values of 0.824 × 10-48 cm4 s (or 82.4 GM) and 6.30 × 10-25 cm6/GW2, respectively, in femtosecond region among the highest ones reported for many diphenylaminofluorene-derived AFX chromophores. Utilization of a keto linker located immediately between C60 cage and fluorene chromophore moieties facilitates molecular polarization of the DPAF ring toward the C60 cage. That may serve as the fundamental cause for correlation of enhanced A−D electron interactions to, ultimately, observed multiphoton absorption cross sections. By using nanosecond laser flash photolysis results taken at 355 nm as the reference, transient absorption data obtained from femtosecond pump−probe experiments at 800 nm unambiguously verified the occurrence of two-photon excitation processes of C60(>DPAF-C9) in air-saturated benzene and subsequent efficient energy transfer from the two-photon pumped DPAF-C9 moiety to the C60 cage moiety.

1‐(bromoacetyl)pyrene and its arsonium salt as novel photoinitiators for styrene polymerization

AbstractThe photopolymerization of styrene (Sty) in DMSO induced by pyrene (Py), 1‐Acetylpyrene (AP), 1‐(Bromoacetyl) pyrene (BP), and 1‐Acetylpyrene triphenyl arsonium bromide (APAS) has been investigated. Under all conditions employed, Py was completely ineffective. Incorporation of a chromophoric (COCH3) moiety introduces photoinitiating activity into Py. It was observed that introduction of Br into AP markedly accelerated the rate of UV irradiation‐induced polymerization. BP was further modified to its arsonium salt (APAS). The kinetics and mechanism of polymerization using BP and APAS as initiators have been investigated in detail. The polymerization with BP followed nonideal kinetics (Rp ∝ [BP]0.8 [Sty]1.1) with respect to initiator concentration whereas ideal kinetics (Rp ∝ [APAS]0.48 [Sty]1.1) was observed when APAS was used as initiator. Degradative transfer is thought to be mainly responsible for this unusual kinetic behavior for BP–Sty system. The kinetic data proved that BP was more effective and faster initiator than APAS. In both the cases, the mechanism of polymerization was free radical as evident by inhibiting the effect of hydroquinone and ESR studies. IR and NMR spectra showed the atactic nature of polystyrene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1793–1798, 2006

Ultrafast Excited-State Dynamics of DNA Fluorescent Intercalators: New Insight into the Fluorescence Enhancement Mechanism

The excited-state dynamics of the DNA bisintercalator YOYO-1 and of two derivatives has been investigated using ultrafast fluorescence up-conversion and time-correlated single photon counting. The free dyes in water exist in two forms: nonaggregated dyes and intramolecular H-type aggregates, the latter form being only very weakly fluorescent because of excitonic interaction. The excited-state dynamics of the nonaggregated dyes is dominated by a nonradiative decay with a time constant of the order of 5 ps associated with large amplitude motion around the monomethine bridge of the cyanine chromophores. The strong fluorescence enhancement observed upon binding of the dyes to DNA is due to both the inhibition of this nonradiative deactivation of the nonaggregated dyes and the dissociation of the aggregates and thus to the disruption of the excitonic interaction. However, the interaction between the two chromophoric moieties in DNA is sufficient to enable ultrafast hopping of the excitation energy as revealed by the decay of the fluorescence anisotropy. Finally, these dyes act as solvation probes since a dynamic fluorescence Stokes shift was observed both in bulk water and in DNA. Very similar time scales were found in bulk water and in DNA.

Total Synthesis of TANDEM on Solid Phase

The total synthesis of N-demethylated triostin A (TANDEM), a C 2-symmetric bicyclic octadepsipeptide, on solid phase was successfully achieved in 22 steps (19 steps on solid phase) in an overall yield of 18%. Starting from N-Fmoc-alanine attached to Wang resin, seven amino acids and two chromophore moieties were successively incorporated in an alphabetical order [(a)-(i)]. The octadepsipeptide chain was then released from the resin by acidolysis using TFA (j), and macrolactamization of the resulting octadepsipeptide (k) followed by disulfide bond formation (l) gave TANDEM. DNase I footprinting analyses showed the ability of TANDEM to bind to DNA with a preference for 5′-TpA sequences.

Synthesis of novel poly{methyl-[3-(9-indolyl)propyl]siloxane}-based nonlinear optical polymers via postfunctionalization

A novel series of nonlinear optical (NLO) polysiloxanes with a high density of chromophore moieties based on poly{methyl-[3-(9-indolyl)propyl]siloxane} (PMIPS) were synthesized by a post functional strategy. First, PMIPS ( P1) was prepared through hydrosilylation reaction, then P1 is partially formylated by the reaction between P1 and the reagents of dimethylformamide (DMF) and phosphorus oxychloride under the standard Vilsmeier reaction conditions, and these formyl groups with high reactivity are condensed with four predesigned cyanoacetylated chromophores to afford the series of chromophore functionalized polysiloxanes ( P3– 6). The most special point is the molar concentrations of chromophore moieties are the same in polymers P3– 6, which makes it convenient to study the behavior of different chromophores in the polymeric system. The poled films of P3– 6 reveal the resonant d 33 values in the range of 7.9–55.2 pm/V by second harmonic generation (SHG) measurements.