Oral Presentations.
Luminescence. 2014 Aug;29(S1):6-55
Authors:
Abstract
O0001 On the efficiency of the peroxyoxalate system using a simple experimental and theoretical approach Felipe A. Augusto, Carolina P. Frias, Wilhelm J. Baader Instituto de Química, São Paulo, SP, Brazil The peroxyoxalate system is the most efficient intermolecular chemiluminescent reaction with chemiluminescence quantum yields reaching up to three orders of magnitude higher than other similar systems.(1) It consists in the reaction of an oxalic ester with hydrogen peroxide, typically catalyzed by a base, forming a high-energy intermediate which interacts with a compound called activator, ACT.(2,3) This interaction leads to the ACT in its singlet excited state in a mechanism that involves a charge/electron transfer initially from the ACT to the peroxide and then back to the ACT.(2,3) Several important details have been experimentally determined about the mechanism, like the cyclization rate constant and the direct interaction between the high-energy intermediate and the ACT.(4,5) However the identity of the high-energy intermediate is still a matter of discussion, with only a few possible intermediate structures being properly studied or definitely discarded.(6) The study and characterization of the peroxyoxalate reaction with a relatively small ACT, like naphthalene, could allow a detailed theoretical study of the chemiexcitation step, contrarily to the case of the compounds normally used as ACTs which would involve prohibitive computational costs. Therefore, the reaction of bis(2,4-dinitrophenyl) oxalate (DNPO) with hydrogen peroxide catalyzed by imidazole (IMI-H) was studied using naphthalene as ACT. The observed rate constant (kobs ) showed linear dependence with the [H2 O2 ] (Fig. , kH2O2 = 23 ± 1 L mol(-1) s(-1) ) and [IMI-H] (Fig. , kIMI-H = 202 ± 7 L mol(-1) s(-1) ) and no dependence with [DNPO] or [ACT] (data not shown). [Figure: see text] The study of the peroxyoxalate system, employing naphthalene as electronically simple ACT, indicates the existence of a linear relationship between the kobs and the H2 O2 as well as IMI-H concentration, in general agreement with the mechanism proposed for the initial steps of the transformation. This fact indicates a normal behavior of the system in the conditions utilized. Therefore, the peroxyoxalate reaction with naphthalene as ACT will now be subject to theoretical studies in order to elucidate the exact mechanism of the chemiexcitation step, with the intention to understand the reason for the extremely high efficiency of the system even so it involves, apparently, intermolecular electron transfer steps. References 1. Augusto FA, Souza GA, Souza Junior SP, Khalid M, Baader WJ. Photochem. Photobiol. 2013;89:1299. 2. Ciscato LFML, Augusto FA, Weiss D, Bartoloni FH, Albrecht S, Brandl H, Zimmermann T, Baader WJ. ARKIVOC 2012;2012:391. 3. Bartoloni FH, Bastos EL, Ciscato LFML, Peixoto MMdeM, Santos APF, Santos CS, Oliveira S, Augusto FA, Pagano APE, Baader W. J. Quim. Nova 2011;34:544. 4. Da Silva SM, Casallanovo F, Oyamaguchi KH, Ciscato LFML, Stevani CV, Baader WJ. Luminescence 2002;17:313. 5. Ciscato LFML, Bartoloni FH, Bastos EL, Baader WJ. J. Org. Chem. 2009;74:8974. 6. Stevani CV, Campos IPA, Baader WJ. J. Chem. Soc., Perkin Trans. 2 1996;1645. O0002 Kinetic studies on the sodium salicylate catalyzed peroxyoxalate reaction Glalci A. Souza, Wilhelm J. Baader Instituto de Química da Universidade de São Paulo, São Paulo-SP, Brazil The peroxyoxalate reaction is the only chemiluminescence reaction which appears to involve the intermolecular Chemically Initiated Electron Exchange Luminescence (CIEEL) mechanism in its chemiexcitation step that possess highest emission quantum yields of up to 60%.(1-3) Detailed kinetic studies on this highly efficient CL system has been performed mainly using imidazole as base catalyst and the mechanistic elucidation of the complete reaction has shown that this compound is acting also as nucleophilic catalyst.(4-5) However, it has been shown also that the base and nucleophilic catalyst imidazole leads to a decrease in the CL emission quantum yield, apparently due to its interaction with the high-energy intermediate.(4-6) In order to further elucidate the mechanism of the peroxyoxalate system, the kinetics of the reaction were studied with sodium salicylate as base catalyst. The CL emission obtained in the reaction of bis(2,4,6-trichlorophenyl) oxalate (TCPO) (0.1 mM) with hydrogen peroxide, catalyzed by sodium salicylate, in the presence of 9,10-diphenylanthracene (DPA) (0.2 mM) as activator, in ethyl acetate at 25 °C, was measured in different conditions. When the reaction was performed varying the sodium salicylate concentration, the rate constants corresponding to the emission decay increased with the base concentration, showing a saturation curve like behavior. The decay rate constant also increased with increasing hydrogen peroxide concentrations and at low H2 O2 concentrations the rate constants show a linear dependence on the hydrogen peroxide concentration allowing the determination of a bimolecular rate constant (kbim ). These rate constants showed to depend also on the sodium salicylate concentration; kbim = (0.56 ± 0.06) 10(-3) ; (1.6 ± 0.2) 10(-3) and (2.04 ± 0.06) 10(-3) L mol(-1) s(-1) , for sodium salicylate concentrations of 0.3, 1.0 and 5.0 mmol L(-1) , respectively. Upon variation at higher hydrogen peroxide concentrations the rate constants showed saturation curves, indicating a change in the rate-limiting step. The rate constants corresponding to the initial rise in the emission intensity have been shown independent of the hydrogen peroxide concentration showing that this reagent does not participate in the reaction step measured in this part of the kinetic curve. Similarly to the behavior observed with imidazole, the CL emission quantum yield showed to decrease with an increase in the sodium salicylate concentration. The maximum quantum yields obtained with sodium salicylate were s (max) = (1.24 ± 0.06) 10(-3) E mol(-1) when the sodium salicylate concentration was 0.5 mmol L(-1) . These data indicate that, like imidazole, also sodium salicylate appears to interaction with the high-energy intermediate in the peroxyoxalate reaction, which diminishes the CL emission quantum yields. Financial support; FAPESP, Capes, CNPq. 1. Stevani CV, Silva SM, Baader WJ. Eur. J. Org. Chem. 2000;4037. 2. Augusto FA, Souza GA, Souza Jr., SP, Khalid M, Baader WJ. Photochem. Photobiol. 2013, 89, 1299. 3. Ciscato LFML, Augusto FA, Weiss D, Bartoloni FH, Bastos EL, Albrecht S, Brandl H, Zimmermann T, Baader, WJ. Arkivoc;2012 (iii), 391. 4. Silva SM, Casallanovo F, Oyamaguchi KH, Ciscato LFLM, Stevani CV, Baader WJ, Luminescence 2002;17:313. 5. Stevani CV, Lima DF, Toscano VG, Baader WJ, J. Chem. Soc. Perk. Trans. 2 1996;989. 6. Ciscato LFML., Bartoloni FH, Bastos EL., Baader WJ, J. Org. Chem. 2009;74:8974. O0003 How can quantitative bioluminescence and in-situ fluorescence of firefly oxyluciferin in luciferase be compared with theoretical calculations? Hidefumi Akiyama(a) , Yu Wang(a,b) , Miyabi Hiyama(a) , Toshimitsu Mochizuki(a) , Kanako Terakado(c) , Toru Nakatsu(c) (a) University of Tokyo, Kashiwa, Chiba 2778581, Japan (b) Institute of Genetics and Developmental Biology, Beijing 100101, Japan (c) Kyoto University, Sakyo-ku, Kyoto 6068501, China To investigate color-determination mechanisms from physicist points of view, we study quantitative spectra of firefly bioluminescence, and the in-situ absorption and fluorescence spectra of oxyluciferin contained in luciferase in a consumed reaction mixture, and intend to compare them with quantum-chemistry theoretical calculations. We have so far measured quantitative in-vitro firefly bioluminescence spectra influenced by pH, kinds of bivalent metal ions, temperatures, and mutant luciferase using our total-photon-flux spectrometer with our new light sta
ndards. We found that all the spectra were systematically and quantitatively decomposed into one environment-sensitive and two environment -insensitive Gaussian peaks, and that no intensity conversion between yellow-green and red emissions but mere intensity variation of the pH-sensitive green peak at 2.2 eV causes the changes in apparent emission colors [1,2]. Therefore, answers for the color-determination problem need not only the assignment of the peaks, but also the explanation of the intensity change of the green peak. [Figure: see text] We next measured in-situ absorption and fluorescence characteristics of oxyluciferin, still combined with luciferase in a consumed reaction mixture [3]. The in-situ absorption spectra indicated that neutral oxyluciferin was dominant, which was in weak pH-dependent equilibrium with oxyluciferin mono-anions. The neutral oxyluciferin was more dominant in luciferase environments than in bare water environments. The in-situ fluorescence spectra shown in Fig. clarified that the neutral oxyluciferin is a blue emitter and the oxyluciferin mono-anion is a green emitter (Fig. ). Even in red-mutant luciferase environment, the in-situ fluorescence has shown strong blue and green fluorescent emissions (Fig. ). In short, the spectra of in-situ fluorescence of oxyluciferin in luciferase and those of bioluminescence have shown significant discrepancy. [Figure: see text] Therefore, the above-mentioned discrepancy between bioluminescence and in-situ fluorescence cast an important question, how they can be consistently compared with quantum-chemistry theoretical calculations, which are recently published in a large numbers. The above results may suggest that enzyme microenvironment affects the transition state in bioluminescence chemical reaction, but not the oxyluciferin states after the reaction. Physicists need to discuss this issue with biologists and chemists in the bioluminescence research community. 1. Ando Y, Niwa K, Yamada N, Irie T, Enomoto T, Kubota H, Ohmiya Y, Akiyama H. Nature Photonics 2008;2:44-47. 2. Wang Y, Akiyama H, Terakado K, Nakatsu T. Scientific Reports 2013;3:2490. 3. Wang Y, Hayamizu Y, Akiyama H. J. Phys. Chem. B 2014;118:2070-2076. O0004 Determination of the total phenolic / antioxidant content in honey samples using formaldehyde / potassium permanganate chemiluminiscence system in a novel microfluidics device Butheina A. M. Al Haddabi, Haider A. J. Al Lawati, FakhrEldin O. Suliman, Gouri B. Varma Sultan Qaboos University, Al-Khod, Oman Microfluidc device has been explored as a tool for the estimation of the total phenolic content/ antioxidant content in honey using acidic potassium permanganate chemiluminescence (KMnO4 -CL) detection system. Selected phenolic antioxidants including quercetin, catechin, gallic acid, caffeic acid and ferulic acid elicited analytically useful CL with detection limits ranging between 2.38 nmol L(-1) for galic acid and 33.9 nmol L(-1) O-coumaric acid for only 2 μL injection volume. The parameters that affect the CL signal intensity of each antioxidant were carefully optimized. . It was observed that formaldehyde can enhance the CL signal intensity of phenolic compounds up to 27 times (Fig. ). Additionally, it was observed that the chip volume and geometry both can play an important role in enhancing the CL signal intensity in this system. The CL signal intensity was enhanced five times when a spiral – flow split chip (SF) geometry was used, compared to the simple spiral chip (S) geometry commonly used (Fig. ). Other parameters were also optimized, including pH and concentration of reagents used and the flow rates. The effect of solvents and surfactants on CL signal intensities was also studied. The method was applied on Omani honey samples. Nine different honey samples resulted in total phenolic / antioxidant level range between 40 and 772 mg Kg(-1) with respect to gallic acid. Folin Coicalteu reagent (FCR) resulted in a good correlation with the developed method which was found to be a selective, rapid and sensitive method to estimate total phenolic / antioxidant level in a good agreement with reported results for honey samples. [Figure: see text] [Figure: see text] References 1. Costin JW, Barnett NW, Lewis SW, McGillivery DJ. Analytica Chimica Acta 2003;499:47-56. 2. Alvarez-Suarez JM, Gonzalez-Paramas AM, Santos-Buelga C, Battino M. J. Agric. Food Chem. 2010;58:9817-9824. O0005 Electrochemiluminescence sensor based on tris(2,2’bipyridyl)ruthenium(II)/poly(AHNSA) for chlorpheniramine maleate analysis Mohammed M. Alhinaai, Emad A. Khudaish Sultan Qaboos University, AlKhude, Muscat, Oman Since the discovery of impressive luminance property of tris(2,2’bipyridyl)ruthenium(II), [Ru(bpy)3 ](2+) , it becomes one of intensive used reagent for chemiluminescence and electrochemiluminescence (ECL) analysis with a wide range of coreactants. Immobilizing of the expensive Ru(II)-complex on the electrode surface began early 1980s using Nafion as an exchanger polymer [1] is still a hot and continuous topic by many research groups [2]. The main objective of the present work was to develop a solid-state ECL sensor based on immobilizing [Ru(bpy)3 ](2+) on a conducting polymer for chlorpheniramine maleate (CPM) determination. The sensor was fabricated by composite electropolymerization of 2.0 mM [Ru(bpy)3 ](2+) and 1.5 mM of 4-amino-3-hydroxy-naphthalene sulfonic acid (AHNSA) in acidic medium via potentiodynamic repetitive cycles between -0.8 and +2.0 V at 0.1 V s(-1) . The fabrication parameters were optimized carefully in order to produce a stable film and obtain an intense ECL signal. Figure shows the electrochemical characterization of the composite surface film where a redox peak of [Ru(bpy)3 ](2/3+) are well defined at 1180 mV (anodic) and 980 mV (cathodic), respectively. Impedance spectroscopy analysis showed that the charge transfer resistance of the composite film is greatly lowered by doping Ru(II)-complex on the moiety of the PAHNSA which suggests that Ru(II)-complex is acting as a charge transfer center [3]. [Figure: see text] This sensor exhibited excellent ECL behaviour toward CPM analysis as shown in Fig. with a good stability and reproducibility. The standard deviation of 16 measurements in flow stream was 2.35%. It also has a very good lifetime when stored in 5 °C for two weeks where the recovery measurement approached 94%. The sensor was also applied to estimate CPM in pharmaceutical preparations. The linear dynamic range was from 0.1 to 32 µg/mL (R(2) = 0.9956). The detection limit was 23 µg/L and the recovery of real sample analysis was from 102.0% to 98.50% for syrup and tablets respectively. [Figure: see text] Interference studies showed no effect of common compounds and the acceptable molar concentration ratios of foreign species to CPM were higher than1000-fold for Na(+) , K(+) , NO3 (-) , SO3 (2-) , 100-fold for Mg(2+) , Al(3+) , NH4 (+) , Cl(-) , lactose, sucrose, and glucose, and 10-fold for Fe(3+) and Co(2+) . The analytical parameters such as pH, flow rate, buffer concentration were systematically tested. In conclusion, a novel composite polymeric film was fabricated using simple electrochemical method and applied for determination of CPM in real samples. The sensor showed a good stability and sensitivity regardless the matrix of the pharmaceutical preparation. References 1. Rubinstein I, Bard A. J. J. Am. Chem. SOC. 1980;102;6641-6842. 2. Su M, Wei W, Liu S. Analytica Chimica Acta 2011;704:16-32. 3. Zhang B, Shi S, Shi W, Sun Z, Kong X, Wei M, Duan X. Electrochimica Acta 2012;67:133-139. O0006 Experimental Evidence of the Occurrence of an Intermolecular Electron Transfer in the Catalyzed Decomposition of spiro-Alkyl-1,2-Dioxetanones Fernando Heering Bartoloni(2,1) , Marcelo Almeida de Oliveira(1) , Luiz Francisco Monteiro Leite Ciscato(2,1) , Felipe Alberto Augusto(1) , Erick Leite Bastos(1) , Wilhelm Josef Baader(1) (1) Departamento de Qu&iacu
te;mica Fundamental do Instituto de Química da Universidade de São Paulo, Sao Paulo. SP, Brazil, (2) Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo Andre, SP, Brazil Several chemical and biochemical reactions have light as a co-product and some of them can show high quantum efficiencies, include firefly bioluminescence, the peroxyoxalate system, and the induced decomposition of 1,2-dioxetanes.(1) Cyclic peroxides have been frequently described as high-energy intermediates in the chemical formation of products in the electronic excited state because their decomposition fulfill both energetic and geometric criteria required for chemiexcitation. Nevertheless, the thermal decomposition of 1,2-dioxetanes and 1,2-dioxetanones results in inefficient chemiluminescence emission due to the preferential formation of products in the non-emissive triplet-excited state (ΦS < 10(-4) E mol(-1) vs. ΦT > 0.1 E mol(-1) ). ).(2,3) However, it has been reported that fluorescent polycyclic aromatic hydrocarbons with low oxidation potentials (referred to as activators, ACT) catalyze the decomposition of 3,3-dimethyl-1,2-dioxetanone (1), resulting in noticeable increase in light emission intensity, and high singlet chemiexcitation quantum yields (ΦS = 0.1 E mol(-1) ).(4) Contrarily, our group found recently that the ΦS for the catalyzed decomposition of 1,2-dioxetanones, the model intermediate in firefly bioluminescence, were overestimated in several orders of magnitude.(5) Consequently, the validity of this system as a model for excited states formation might be questioned. Therefore, we report here our results of a kinetic study on the catalyzed decomposition of the spiro-substituted 1,2-dioxetanone derivatives, spiro-adamantyl-1,2-dioxetanone (2) and spiro-cyclopentyl-1,2-dioxetanone (3) by several activators and confirmed the occurrence of an intermolecular electron or charge transfer in this transformation. The 1,2-dioxetanone derivatives 2 and 3 were prepared, purified and handled as described elsewhere;(6) kinetic assays and data treatment were performed as detailed before.(5) The kobs values for the decomposition of 2 and 3, determined in toluene in the absence and in the presence of different ACTs, do not depend on the nature and concentration of the ACT (kobs (2, 50 °C) = (6 ± 1) 10(-3) s(-1) and kobs (3, 25 °C) = (9 ± 3) × 10(-4) s(-1) ). Therefore, the bimolecular rate constant (kCAT ) cannot be determined directly; however, the kCAT /kD ratios and the chemiexcitation quantum yields at the infinite ACT concentration (ΦS (∞) ) can be calculated for each ACT from the double reciprocal plots of the singlet quantum yields (ΦS ) versus the ACT concentrations.(5) The kCAT /kD values show linear free-energy relation with the ACT’s oxidation potential, indicating the importance of an intermolecular electron transfer from the ACT to the peroxide in the chemiexcitation step. The low efficiency in excited states formation in the catalyzed decomposition of these cyclic peroxides are rationalized by steric interactions between the activator and the bulky alkyl substituents on the peroxidic ring, thereby lowering the charge-transfer complex formation constant between the peroxide and the activator. Financial support; FAPESP, Capes, CNPq. 1. Augusto FA, Souza GA, Souza Junior SP, Khalid M, Baader WJ. Photochem. Photobiol. 2013;89:1299. 2. Adam W, Baader WJ. J. Am. Chem. Soc. 1985;107:416. 3. Adam W, Baader WJ. Angew. Chem. Int. Ed. Engl. 1984;23:166. 4. Schuster GB, Schmidt SP. Adv. Phys. Org. Chem. 1982;18:187. 5. de Oliveira MA, Bartoloni FH., Augusto FA, Ciscato LFML, Bastos EL, Baader WJ. J. Org. Chem. 2012;77;10537. 6. Bartoloni FH, de Oliveira MA, Augusto FA, Ciscato LFML, Bastos EL, Baader JW. J. Braz. Chem. Soc. 2012;23:2093. O0007 Chemiluminescent detection of Nitric Oxide Martina Bancirova Palacký University, Olomouc, Czech Republic The chemistry of nitric oxide inside humans and other mammals is perhaps the most interesting aspect of this simple molecule’s behaviour. NO is involved in controlling blood pressure; transmitting nerve signals and a variety of other signalling processes. When tissues in the body become inflamed for long periods of time, the concentration of nitric oxide within them increases and this can be used to diagnose disease. But also NO secreted by activated cells appears to be a complex “cocktail” of substances (see Fig. .)(1) [Figure: see text] So is necessary to take in account the presence of ROS during the determination of nitric oxide. One of the chemiluminescent detections is based upon the chemiluminescence reaction between NO and the luminol (5-amino-2,3-dihydro-1,4-phthalazinedione)-H2 O2 system. The luminol-H2 O2 system is specifically reactive to NO, so that other nitrogen-containing compounds (organic nitrite, organic nitrate, and thio-nitroso compounds do not interfere. (2) The light emission of luminol as detection of bloodstains is a complex process based on hydrogen peroxide decomposition catalyzed by haemoglobin. Three common known methods of bloodstains; detection according to Grodsky, Weber and by Bluestar® Forensic reagent(3), are based on the luminol chemiluminescence (complex process based on hydrogen peroxide decomposition catalyzed by haemoglobin). The Bluestar® Forensic Magnum was chosen because of its declared stability as a “new” detection system for nitric oxide. The different dilutions (up to three orders) of the Bluestar® Forensic Magnum were used. The experiments were done by using luminometer (type FB 12, Berthold Detection Systems, Germany) in the total volume of 1 mL. Sodium azide was used as a specific quencher of singlet oxygen to prove its presence (see Fig. .) [Figure: see text] 1. Kroncke KD, Fehsel K, Kolb-Bachofen V. Nitric Oxide; Cytotoxicity versus Cytoprotection-How, Why, When, and Where?, NITRIC OXIDE; Biology and Chemistry 1997;1:107-120. 2. Kikuchi K, Nagano T, Hayakawa H, Hirata Y, Hirobe M. Detection of Nitric Oxide Production from a Perfused Organ by a Luminol-H202 System. Analytical Chemistry 1993;65:1794-1799. 3. Blum LJ, Esperança P, Rocquefelte S. A new high-performance reagent and procedure for latent bloodstain detection based on luminol chemiluminescence. Canadian Society of Forensic Science Journal. 2006;39:81-100. Financial support from the Czech Science Foundation, project 301/11/0767. O0008 An In-depth study on Blue electrochemiluminescent Iridium(III) complexes Gregory Barbante(a) , Egan Doeven(a) , Paul Francis(a) , Timothy Connell(c) , Paul Donnelly(c) , Conor Hogan(b) , David Wilson(b) (a) Deakin University, Geelong, Victoria, Australia (b) La Trobe University, Melbourne, Victoria, Australia (c) Melbourne University, Melbourne, Victoria, Australia Electrogenerated chemiluminescence (ECL) is a form of luminescence produced by high-energy reactions between electrogenerated precursors,([1,2]) in which the electronically excited states responsible for the emission of light can be generated through the annihilation between oxidised and reduced forms of the same species, or by using a sacrificial co-reactant. The application of a co-reactant ECL as a highly sensitive mode of detection has been predominantly based on the use of tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)3 ](2+) ), and related polyimine-ruthenium(II) complexes, with characteristic orange/red emissions (max ca. 590-700 nm).([1,2]) Over the last decade, however, numerous researchers have begun to explore chemiluminescence and ECL reactions with cyclometalated iridium(III) complexes exhibiting a wide range of electrochemical properties and emission maxima that can be tuned through subtle changes in the structure of one or more ligands.([3]) These complexes have created new possibilities for multiplexed ECL detection systems.([4]) However, in contrast to the vast range of orange/red-emitting metal c
omplex electrochemiluminophores,([5,6]) relatively few blue emitters are available, and the most effective design of blue-emitting complexes for ECL detection is yet to be fully elucidated. We have therefore used electrochemical, spectroscopic and computational techniques to explore a series of blue-emitting iridium(III) complexes (see Fig. ) that exhibit various potentially attractive structural attributes for conventional and multiplexed ECL detection. Theoretical and experimental studies reveal the most effective strategies for the design of blue-shifted iridium(III) complexes for efficient electrogenerated chemiluminescence. Stabilisation of the HOMO while only moderately stabilising the LUMO increases the energy gap, thus ensuring favourable thermodynamics and kinetics for the reaction leading to the excited state. Of the iridium(III) complexes examined, [Ir(df-ppy)2 (ptb)](+) was most attractive as a blue-emitter for ECL detection, featuring a large hypsochromic shift (max = 454 and 484 nm), superior co-reactant ECL intensity than the archetypal homoleptic green and blue emitters; [Ir(ppy)3 ] and [Ir(df-ppy)3 ] (by over 16-fold and threefold, respectively), and greater solubility in polar solvents. We have therefore used electrochemical, spectroscopic and computational techniques to explore a series of blue-emitting iridium(III) complexes (see Fig. ) that exhibit various potentially attractive structural attributes for conventional and multiplexed ECL detection. Theoretical and experimental studies reveal the most effective strategies for the design of blue-shifted iridium(III) complexes for efficient electrogenerated chemiluminescence. Stabilisation of the HOMO while only moderately stabilising the LUMO increases the energy gap, thus ensuring favourable thermodynamics and kinetics for the reaction leading to the excited state. Of the iridium(III) complexes examined, [Ir(df-ppy)2 (ptb)](+) was most attractive as a blue-emitter for ECL detection, featuring a large hypsochromic shift (max = 454 and 484 nm), superior co-reactant ECL intensity than the archetypal homoleptic green and blue emitters; [Ir(ppy)3 ] and [Ir(df-ppy)3 ] (by over 16-fold and threefold, respectively), and greater solubility in polar solvents. [Figure: see text] 1. Bard AJ. Electrogenerated Chemiluminescence. Marcel Dekker; New York, 2004 2. Forster RJ, Keyes TE. Neuromethods 2013;80:347-367 3. Zanarini S, Felici M, Valenti G, Marcaccio M, Prodi L, Bonacchi S, Contreras-Carballada P, Williams RM, Feiters MC, Nolte RJM, De Cola L, Paolucci F. Chem. Eur. J. 2011;17:4640-4647 4. Doeven EH, Zammit EM, Barbante GJ, Hogan CF, Barnett NW, Francis PS. Angew. Chem. 2012;124:4430-4433 5. Barbante GJ, Hogan CF, Wilson DJD, Lewcenko NA, Pfeffer FM, Barnett NW, Francis PS. Analyst 2011;136:1329-1338 6. Gorman BA, Francis PS, Barnett NW. Analyst 2006;131:616-639 O0009 Chaetopterus variopedatus tissue autofluorescence spectral characteristics Anna Belousova(a) , Fyodor Kondrashov(b) , Maria Plyuscheva(b) (a) Moscow State University, Biological Faculty, Invertebrate Zoology Department, Moscow, Russia (b) Centre de Regulació Genòmica (CRG), Barcelona, Spain Chaetopterus variopedatus is a sedentary marine polychaete that lives in a parchment U-shaped tube. It has a body with three distinct regions, each region contains different morphologically developed segments. [3] The polychaete is famous for being capable of emitting light with its epithelium and producing blue luminous mucous. Studies on anatomy and morphology of phenomenon of its epithelial bioluminescence have pointed out some special areas of intensity, such as notopodial structures of middle and posterior regions. [2] Referring to the chemical approach, previous research on the chemical compounds of Chaetopterus bioluminescent system have proved that the photoprotein takes part in the reaction. [1] As for the whole biochemical pathway of the Chaetopterus bioluminescence – it is still a question to solve. Photoproteins that are involved in the luminescence reaction are known for becoming fluorescent after the reaction of luminescence takes place. [1] Therefore, the distribution of the products of the bioluminescence reaction can be studied using the confocal light microscopy methods. The autofluorescence itself is usually relatively stable either continious, or intensive. The distribution of fluorescence of different wavelengths was observed with a confocal microscope on several cross-sections of the worm’s body and on epithelium of various parts of the body. The specimens of the worms tissue exhibit fluorescence of some ranges of wavelengths – excited by lasers from 405 to 633 nm. Confocal observations have shown that the UV excitation of a tissue results most efficiently in the strong fast-bleaching fluorescence in far-red (630 nm) spectrum area. Purified far-red autofluorescent component which is supposed to be a part of bioluminescence reaction [4] is stored in the vesicles which can be visualised with the confocal microscopy. Though having a strong intensity, the far-red fluorescence is bleaching very fast which makes it more challenging to observe. References 1. Shimomura O. Bioluminescence; chemical principles and methods. – World Scientific, 2012. 2. Anctil M. The epithelial luminescent system of Chaetopterus variopedatus //Canadian Journal of Zoology. – Т. 57. – №. 6. – С, 1979;1290-1310. 3. Harvey EN. Bioluminescence. – Academic Press, 1952. 4. Branchini BR, et al. Chemical analysis of the luminous slime secreted by the marine worm Chaetopterus (Annelida, Polychaeta) //Photochemistry and photobiology. – Т. 90. – №.1. – С, 2014;247-251. [Figure: see text] [Figure: see text] O0010 Construction of lux operon of the ancestor of bioluminescent bacteria and proposal of evolutionary hypothetical theories on the origin and propagation of luminescent bacterial species Ramesh CH, Mohanraju R Pondicherry University, Pondicherry, India Using the processes, “Horizontal gene transfer (HGT) or Chromosomal exchange mechanism (CEM) or Acquisition, Plasmid DNA exchange, genetical processes like Interchromosomal rearrangements (ICR), and geological processes” we assembled lux genes together and constructed the luminescent bacterial ancestor that might have not yet been isolated or extincted in the biological evolution during the geological processes. The construction of lux operon of this luminescent ancestor was carried out with different lux genes such as the regulatory and structural genes, and with other genes which are flanking towards upstream and downstream of the lux operon of different luminescent bacterial species. The lux operon of this ancestor was constructed based on the approximate base pairs of different lux genes. The approximate order of lux operon is as follows luxZYLOPUMNQRSTICDABFEGH-ribEBHA. Where rib genes of rib operon are linked to downstream of the lux operon. Hypothetically it is possible to construct this luminescent bacteria ancestor, while we expect possibilities of finding of this luminescent ancestor. The processes “Insertion, Deletion, Horizontal gene transfer (HGT) or Chromosomal exchange mechanism (CEM) and Interchromosomal rearrangements (ICR), geological processes and Plasmid DNA exchange (PDE) might have given origin for modern luminescent bacteria. These processes provides base for this ancestor construction and supports for the presence or possibility in constructing the ancestor of luminescent bacteria. We also propose new strong hypothetical theories which speak about the existence of luminescent ancestor and origin of modern luminescent bacterial species. O0011 Ecological functions of shark luminescence Julien Claes, Jérôme Mallefet Laboratoire de Biologie Marine, Earth and Life Institute, Université catholique de Louvain, Louvain-la-Neuve, Belgium Introduction; Sharks from the Etmopteridae and Dalatiidae families are among the most enigmatic bioluminescent organisms. Although they encompass about 12% of current shark diversity, with
over 50 described species, their luminescence is rarely observed [1]. Moreover, contrary to the situation encountered in other animals, their intrinsic light organs (photophores) are primarily controlled by hormones rather than by nerves [2,3] and form a diversity of patterns whose adaptive advantage has long remained obscure. This work aims to synthetize recent advances made in the field of shark luminescence ecology as well as to present novel experimental data in order to inspire future research. It involves various techniques such as in vivo luminescence measurements [via an optic fibre coupled to a luminometer (Berthold FB12)], spectrophotometry [with a mini-spectrometer (Hamamatsu Photonics C10083CA)], stereology and visual modelling. Results and discussion; In the last five years, we observed and characterized the spontaneous luminescence of one dalatiid and three etmopterid shark species. At 0.5 prepelvic length, their luminescence [downward emission; λmax at 457-488 nm; ventral intensity = 0.34-130.78 Mq s(-1) mm(-2) (n = 31)] appears physically similar to the residual downwelling light present in their environment, supporting a function of camouflage by counterillumination [1,4]. However, digital photography revealed that etmopterid luminescence (i) was not homogeneous on the ventral side (Fig. A), a result confirmed by stereological analysis of photophore distribution; and (ii) was also present dorsally, as dim glows underlying several structures including fin spines, eyes and nostrils (Fig. B). This leads to a variable angular distribution pattern along the etmopterid body, as it can be seen in E. spinax, whose luminescence adopts caudally (at the level of clade-specific lateral photophore markings) a more lateral distribution well suited for intraspecific communication (Fig. ). Visual modelling demonstrated that spine-associated glow signal the presence of the defensive fin spines to predators at several meters and hence might be used for aposematism [5]. Finally, the association of photophores with photoreceptive tissues likely provides a reference for counterillumination while nostril luminescence might be used as a torch to improve prey detection. We suggest the luminescence versatility of etmopterid sharks to have powered their rapid radiation in the deep-sea. Acknowledgments Julien M. Claes and Jérôme Mallefet are respectively postdoctoral researcher and research fellow of the Fonds National de la Recherche Scientifique (FNRS, Belgium). This is a contribution to the Biodiversity Research Center (BDIV) and to the Centre Interuniversitaire de Biologie Marine (CIBIM). References 1. Claes JM, Nilsson DE, Straube N, Collin SP, Mallefet JM. Sci. Rep. 2014;4:4328 2. Claes JM, Mallefet J. J. Exp. Biol. 2009;212:3684-3692. 3. Claes JM, Ho HC, Mallefet J. J. Exp. Biol. 2011;215:1691-1699. 4. Claes JM, Aksnes DL, Mallefet J. J. Exp. Mar. Biol. Ecol. 2010;388:28-32. 5. Claes JM, Dean MN, Nilsson DE, Hart NS, Mallefet J. Sci. Rep. 2013;3:1308. [Figure: see text] [Figure: see text] O0012 Prolonging Light Emission in Enhanced Chemiluminescence (ECL) Leopoldo Della Ciana(a) , Michele Zucchelli(a) , Luca Covello(a) , Dario Foglietta(a) , Ivan Yu Sakharov(b) (a) Cyanagen, Bologna, Italy (b) Department of Chemistry of Lomonosov Moscow State University, Moscow, Russia The chemiluminescent oxidation of luminol catalyzed by peroxidase finds wide application in the detection and quantitation of antigens, haptens, and nucleic acids and, in particular blotting tests, i.e., Western (proteins), Southern (DNA), Northern (RNA) blots, and ELISA. Because peroxidases are poor catalysts in luminol oxidation, certain compounds known as enhancers are added to the substrate mixture to increase chemiluminescent (CL) intensity. Although a number of compounds were successfully used in the enhancement of peroxidase-induced CL [1,2], currently the most effective enhancer is 3-(10-phenothiazinyl)propane-1-sulfonate (SPTZ) [3]. This compound can increase CL induced by horseradish peroxidase (HRP) and soybean peroxidase (SbP), by an order of magnitude when compared to previously known enhancers, such as p-iodophenol, p-coumaric acid or p-iodophenylboronic acid [3]. Furthermore, it was shown that the introduction of some 4-dialkylaminopyridines such as 4-morpholinopyridine (MORP) a reaction mixture containing luminol, hydrogen peroxide, and SPTZ resulted in a further 10-fold increase of CL intensity. Because 4-dialkylaminopyridines enhanced CL only in the presence of a primary enhancer (SPTZ) and did not act as enhancers in the absence of SPTZ, these compounds were named ” secondary enhancers” . A recent study [4] suggests that ” for an implementation of its enhancing ability, 4-dialkylaminopyridines should get bound to a protein fragment of peroxidase located near the entrance in the canal of the active site, where adsorption of peroxidase substrates commonly occurs The existence of such a complex near the active site may help in binding SPTZ to the peroxidase due to the formation of some charge transfer and ionic bonds between 4-dialkylaminopyridines and SPTZ and, consequently, may improve the efficiency of the enzymatic oxidation of SPTZ with the formation of SPTZ(•+) , that, reacting with luminol, results in the increase of CL intensity” . No significant effect was observed when secondary enhancers were included in the formulation containing primary enhancers other than SPTZ. Apart from chemiluminescent signal intensity, another important feature of ECL systems is light output duration. A prolonged light emission is highly desirable, especially in the blotting techniques, where esposure parameters may need adjustement, without the need to repeat the experiment. In addition, to increase detection it may be useful to prolong exposures to many hours. Again, when considering formulations with only primary enhancers, SPTZ substrates are by far the best in terms of prolonged light emission. The addition of secondary enhancers such as MORP causes a gradual decrease in light output duration, reaching its minimum at the highest initial signal level. Thus, the aim of this study is the search for additives and/or reaction conditions which could prolong light output in these systems. In particular, we have extended our screening to chelators, free-radical scavengers, electron/energy transfer mediators. As a result, we discovered some formulations with significantly improved light duration. These favorable properties were also observed in model dot-blot assays and ELISA. 1. Thorpe GHG, Kricka LJ, Moseley SR, Whitehead TP. Clin. Chem. 1985;31:1335. 2. Kricka LJ, Cooper M, Ji X. Anal. Biochem. 1996;240:119-125. 3. Marzocchi E, Grilli S, Della Ciana L, Prodi L, Mirasoli M, Roda A. Anal. Biochem. 2008;377:189. 4. Yu I, Sakharov MM. Vdovenko Analytical Biochemistry 2013;434:12-14. O0013 Marine luciferases; are they really taxon-specific? A putative luciferase evolved by co-option in an echinoderm lineage Jérôme Delroisse(a) , Patrick Flammang(a) , Jérôme Mallefet(b) (a) Biology of Marine Organisms and Biomimetics, University of Mons, Mons, Belgium (b) Laboratory of Marine Biology, Catholic University of Louvain, Louvain-La-Neuve, Belgium The bioluminescence reaction can be generalized as the oxidation of a luciferin substrate catalysed by a luciferase enzyme [1]. Although some luciferins are shared by phylogenetically distant organisms, it is commonly admitted that luciferases are clade-specific [2]. The European brittle star Amphiura filiformis emits a blue light using a coelenterazine-luciferase system [3, 4]. However, brittle star luciferases (and echinoderm luciferases in general) have not been characterized so far. Using genomic and transcriptomic data, we highlighted the presence of several putative coelenterazine-specific luciferase sequences in A. filiformis. Sequence comparisons revealed that these enzymes are similar to the luciferase of the luminous sea pansy Renilla sp (up to 47% of identical amino acids, up to 69% of general similarity) despite the
large phylogenetic distance between these two species. Luciferase-like genes are also predicted in the purple sea urchin genome and surprisingly, mRNAs were also specifically identified in different transcriptomes from non-luminous echinoderms. Luciferase-like protein expression in non-luminous organisms raises the question of whether luciferin could be the limitative parameter of the bioluminescence reaction. A physiological approach, performed on tube feet of the common sea star (organs expressing luciferase-like mRNA) demonstrated that coelenterazine supplementation did not induce light emission in crude extracts from tube feet. Therefore, this luciferase-like enzyme must have a different function in sea stars, as it was previously suggested for the purple sea urchin [5]. Assuming Renilla luciferase derived from haloalkane dehalogenases [6], we can hypothesize that haloalkane dehalogenases were presumably independently co-opted in luciferases in both Renilla sp and A. filiformis. Using anti-Renilla luciferase antibody, immunodetections were performed on the arm of A. filiformis. Specific immunolabeling was observed in the stroma of the spines, organs that we previously described as the unique photogenic areas (Fig. ). Our results confirm the probable implication of an enzyme similar to Renilla luciferase in the bioluminescence of the brittle star A. filiformis. Two luminous systems using the same luciferin and homologous luciferases seem to have emerged in a convergent manner in two phylogenetically distant species. The similar way of life of these benthic suspension-feeding species could constitute a strong selective pressure for the emergence of bioluminescence. [Figure: see text] Acknowledgements Jérôme Delroisse, Patrick Flammang and Jérôme Mallefet are respectively research fellow, research director and research associate of F.R.S.-FNRS (Fonds de la Recherche Scientifique). Thanks to Olga Ortega-Martinez, Sam Dupont and Magnus Rosenblad (University of Gothenburg) for the access to Amphiura genomic database. Contribution to the “Centre interuniversitaire de la Biologie Marine”. Work supported in part by a FRFC Grant n° 2.4590.11. References 1. Henry JP, Michelson AM. Bioluminescence. Photochemistry and Photobiology 1978;27(6);855-858. 2. Haddock SH, Moline MA, Case JF. Bioluminescence in the sea. Marine Science 2010;2. 3. Shimomura O. Bioluminescence; chemical principles and methods. World Scientific Publishing Company, 2012. 4. Mallefet J, Parmentier B, Mulliez X, Shimomura O, Morsomme P. Characterisation of Amphiura filiformis luciferase (Ophiuroidea, Echinodermata). In Echinoderms in a Changing World – Johnson (ed) CRC Press The Netherlands. 293, 2013. 5. Fortova A, Sebestova E, Stepankova V, Koudelakova T, Palkova L, Damborsky J, Chaloupkova R. DspA from Strongylocentrotus purpuratus; The first biochemically characterized haloalkane dehalogenase of non-microbial origin. Biochimie 2013;95(11);2091-2096. 6. Loening AM, Fenn TD, Wu AM, Gambhir SS. Consensus guided mutagenesis of Renilla luciferase yields enhanced stability and light output. Protein Engineering Design and Selection 2006;19(9);391-400. O0014 Ultrasensitive bioanalytical application using silica nanoparticles doped with new thermochemiluminescent 1,2-dioxetane derivatives Massimo Di Fusco(a) , Massimo Guardigli(b) , Mara Mirasoli(b) , Arianna Quintavalla(b) , Marco Lombardo(b) , Claudio Trombini(b) , Aldo Roda(b) (a) CIRI-MAM, Alma Mater Studiorum, University of Bologna, Bologna, Italy (b) Department of Chemistry “G. Ciamician”, Alma Mater Studiorum, University of Bologna, Bologna, Italy Thermochemiluminescence (TCL), i.e., the light emission originating from the thermolysis of a suitable molecule, was proposed in the late ’80s as a detection technique for immunoassays [1]. Being TCL emission simply triggered by heat, this technique would allow for reagentless luminescence-based detection, thus simplifying the microfluidic network in miniaturized analytical devices and biosensors. However, TCL detection was abandoned due to methodological problems, such as the high operating temperature (200-250 °C) and the poorer detectability in comparison with other labels. Despite these advantages, TCL detection remains very attractive because it potentially offers the same advantages of other chemiluminescent techniques. Recently, we tried to overcome the problems related to the reported TCL studies and in particular we described the synthesis of a library of TCL acridine-based 1,2-dioxetane derivatives (1-11 in Fig. ) proposed as new TCL labels [2,3]. Suitable structural modifications were introduced to decrease the emission triggering temperature down to 80-100 °C and to produce highly efficient fluorophores in the singlet excited state. [Figure: see text] In the first stage of the work we evaluated the photophysical properties of the acridanone derivatives and the TCL properties of 1,2-dioxetane derivatives using an ITO-coated glass slide as heating element placed directly in contact with a thermoelectrically cooled CCD sensor through a fiber optic taper. Such a lensless contact imaging configuration combined adequate spatial resolution and high light collection efficiency within a small size portable device. We showed that the 10-ethylacetate-9-acridanone derivative moieties produced in the singlet excited state were the main responsible for luminescence emission with fluorescence quantum yields (ϕF ) in the range 0.1-0.5. In addition, with the more efficient 1,2-dioxetane derivative 10 we obtained a limit of detection 17 times lower than 1. Herein, we described the encapsulation of these 1,2-dioxetane derivatives in silica nanoparticles (SiNPs), both alone or together with fluorescent energy acceptors, to obtain amplification of the TCL signal and their superficial modification with biotin for biosensing applications. The amino-functionalized SiNPs loaded with TCL compounds and fluorescent energy acceptor dipyridamole (DP) or 9,10-bis(phenylethynyl)anthracene (BPEA) thanks to the signal amplification due to the large number of 1,2-dioxetane molecules (about 104) in each SiNP and the increased emission efficiency due to the energy transfer to the fluorescent acceptor, could be revealed by TCL imaging with a detectability close to that of the CL enzyme label horseradish peroxidase [2]. In conclusion, the new TCL compounds showed emission triggering temperatures much lower (i.e., < 100 °C) than the compounds used in the past and higher emission yield. In addition, the entrapment of this compound in functionalized SiNPs, used as probes to amplify the TCL signal exploiting the strong biotin-avidin interaction, demonstrated its suitability for the development of TCL-based immune or nucleic acid biosensors. 1. Hummelen JC, Luider TM, Wynberg H. Complementary immunoassays. Chapter 14, Ed. W.P. Collins, 1988;191-208. 2. Roda A, Di Fusco M, Quintavalla A, Guardigli M, Mirasoli M, Lombardo M, Trombini Anal C. Chem. 2012;84:9913-9919. 3. Di Fusco M, Quintavalla A, Trombini C, Lombardo M, Roda A, Guardigli M, Mirasoli M. J. Org. Chem. 2013;78:11238-11246. O0015 Strategies towards Multi-colour Electrochemiluminescence Sensors Egan Doeven, Gregory Barbante, Emily Kerr, Paul Francis Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Faculty of Science, Engineering and Built Environment, Deakin University, Waurn Ponds, Victoria, Australia In recent times electrochemiluminescence (ECL) has emerged as an important analytical technique, its selectivity and sensitivity making it suitable for the detection of a wide range of compounds. ECL is exploited routinely in commercial applications for rapid, sensitive detection and quantification of biomarkers, food borne pathogens and biowarfare agents. New applications of ECL as a sensing technique continue to appear in a wide range of fields, with a range of novel ECL-active luminophores having diverse properties being developed. Generally a single luminophore is excited in an ECL experiment without wavelength discrimination, for exa
mple tris(2,2′-bipyridyl)ruthenium(II) ([Ru(bpy)3 ](2+) ) emits strong co-reactant ECL centred at 620 nm. This work explores the use of multiple, selectively excited ECL luminophores, as well as the recently discovered inhibition of Ir(ppy)3 ECL(1) (under certain conditions) in order to selectively detect three emitting species in a single solution.(2) The emitting species of interest have been developed to have complimentary photophysical and electrochemical properties, and can thus be selectively excited via application of different electrode potentials. Quantification of the emission from the luminophores is investigated using two different approaches. Simultaneously collecting electrochemical and spectral data using a potentiostat and typical wavelength-sensitive detector such as a CCD can be exploited to generate a 3D map of the emission vs. applied potential. Alternatively, the use of a low cost consumer-level digital camera and image analysis algorithms to isolate and quantify the contribution of each complex has been explored. Using this approach we demonstrate simultaneous detection of three emitting species at the low micro-molar level. This low cost multiplexed ECL detection system has potential applications in the emerging fields of mobile phone based telemedicine, as well as expanding the utility of current ECL based assays. 1. Doeven EH, Zammit EM, Barbante GJ, Francis PS, Barnett NW, Hogan CF. A potential-controlled switch on/off mechanism for selective excitation in mixed electrochemiluminescent systems. Chemical Science 2013;4(3);977-982. 2. Doeven EH, Barbante GJ, Kerr E, Hogan CF, Endler JA, Francis PS. Red-green-blue electrogenerated chemiluminescence utilizing a digital camera as detector. Analytical Chemistry 2014. DOI; 10.1021/ac404135f. O0017 Application of quinone as a selective chemiluminescent reagent for determination of biothiols in biological fluids Mohamed Elgawish(a,b) , Naoya Kishikawa(a) , Kaname Ohyama(a) , Naotaka Kuroda(a) (a) Graduate School of Biomedical Sciences, Course of Pharmaceutical Sciences, Nagasaki, Japan (b) Pharmaceutical Chemistry Department, Faculty of Pharmacy, Suez Canal University, Ismailia, Egypt Background The physiological significance of low molecular weight thiols is well recognised with the levels of these compounds within biological fluids such as plasma and urine serving as valuable biomarkers in a number of clinical situations(1) . While there is a clear need to monitor these important analytes and indeed many procedures proffered, considerable scope remains for the development of fast protocols that require minimal sample pre-treatment. The biological important of quinones can be assign to their electrophilic and versatile oxidative properties, which are capable of promoting Michael-addition with cellular thiols, such as free glutathione, cysteine, and cysteine residues of proteins and electron transfer in living system through redox cycling of quinone/semiquinone/quinol triad system. Michael-addition-type probes have been actively developed in recent years and exploited for the design of chromo-and fluorogenic probes for thiol sensing(1) . In this context, we applied for the first time the Michael-addition reaction for chemiluminescence (CL) determination of biothiols. The principal of the proposed method relies on the application of quinone as Michael acceptor to react rapidly and specifically with biothiols. The liberated adducts retain the redox cycling capability of parent quinones to react with reductant, dithiothreitol (DTT), releasing reactive oxygen species (ROS) which can be measured by luminol-CL assay.(2) Materials and Methods Sample preparation One hundred microliters of human plasma, diluted with 500 mmol/L HEPES buffer, pH 8.5 to approximately 300 μL, was mixed with 10 μL of tris (2-carboxyethyl) phosphine (TCEP) solution (100 mmol/L in HEPES buffer, pH 8.5) and allowed to react at room temperature for 15 min. 10 μL of menadione (MQ) solution (100 mmol/L in acetonitrile (ACN)) was added and the sample was spin for 15 min at room temperature. Oasis HLB 1 cm(3) /30 mg cartridges were used to isolate the resulting adducts from each biological sample. The cartridges were conditioned with 0.5 mL of methanol and equilibrated with 0.5 mL of purified water. The samples were passed through individual cartridges, after which the cartridges were washed two times with 250 μL of purified water. The target analytes were eluted with 150 μL of 40% ACN, followed by 150 μL of neat ACN. Each mixture was vortex mixed, diluted ten times, and 20 μL was then inject ed into the HPLC-CL system (Fig. ) [Figure: see text] Results Four of the most important thiols in our body, cysteine (CYS), homocysteine (HCY), glutathione (GSH), and N-acetylcysteine (NAC), were selected under our investigation. MQ, the highly reactive and selective compound of studied quinones, overcame the problems of commonly utilized probe and reacted with thiol group specifically and rapidly at lowest possible temperature. All studied thiols reacted with MQ in 0.5 M HEPES buffer, pH 8.5, at room temperature. The reaction was carried out for 5 min at MQ to thiol molar ratio of about ten. The reaction was specific to aminothiol compared with other aminoacids which shown no reactivity. The calibration curves of MQ-thiol adducts showed excellent linearity over the range 0.0025-2 µmol/L with excellent r values and the detection limits at a signal-to-noise ratio of 3 were 0.0002-0.0008 µmol/L for all analytes. The derivatization of thiols was occurred before solid phase extraction technique to prevail the high polarity which makes their extraction from biological matrices very difficult. The proposed method could successfully quantify the studied thiols in human plasma samples with reasonable accuracy and precision. The protocol shown here clearly provides a sound footing from which further studies can be advanced to the measurement of other sulfhydryl thiols and matrices. References 1. Chen X, Zhou Y, Peng X, Yoon J et al Chem. Soc. Rev. 2010;39:2120. 2. Elgawish MS, Shimomai C, Kishikawa N, Ohyama K, Wada M, Kuroda N et al Chem. Res. Toxicol. 2013;26:1409. O0018 CASPT2//CASSCF Study Of the Ring-opening Mechanism of Dewar Dioxetane Pooria Farahani(a,b) , Marcus Lundberg(a) , Roland Lindh(a) , Daniel Roca-Sanjuán(b) (a) Uppsala University, Uppsala, Sweden (b) Universitat de València, Valencia, Spain Light emission from the heating of Dewar benzene was reported by McCapra.(1) Since the process was observed to be dependent on the presence of oxygen and most of the chemiluminescence reactions occur through an O-O cleavage,(1) the light observed was suggested to be produced after the ring opening of an intermediate structure, named Dewar dioxetane (see Fig. ).(2) The oxidation of Dewar benzene might lead to Dewar dioxetane and, after O-O and C-C cleavage,to the 2,4-hexadiendial product. The thermally activated decomposition mechanism of the Dewar dioxetane has been studied here by the multiconfigurational CASPT2//CASSCF approach,(3,4,5) and accurate reaction path strategies based on minimum energy path and intrinsic reaction coordinate computations. A two-steps biradical mechanism is determined for the process. It involves asynchronous O-O’ and C-C’ bond cleavage as in the related system 1,2-dioxetane.(6) Moreover, a radiationless decay path to the ground-state potential energy surface has been determined for the molecule along the manifold of the excited triplet state, while in the excited singlet state the system evolves toward an equilibrium structure that might be responsible of the light emission. This findings provide clues for rationalizing the observed light and point to a higher efficiency of fluorescence than phosphorescence. [Figure: see text] References 1. McCapra F. QUARTERLY Rev. 1966;20:485. 2. Koo J-Y, Schmidt S, Schuster G. Proc. Natl. Acad. Sci. USA 1978;75:30-33. 3. Roca-Sanju&a
acute;n D, Aquilante F, Lindh R. WIREs Comput. Mol. Sci. 2012;2:585-603. 4. Andersson P, Malmqvist P.-Å, Roos B.O. J. Chem. Phys. 1992;96:1218. 5. Andersson P, Malmqvist P.-Å, Roos B.O, Sadlej A, Wolinski K. J. Chem. Phys. 1992;94:5483. 6. Farahani P, Roca-Sanjuán D, Zapata F, Lindh R. J. Chem. Theory Comput. 2013;9:5404-5411. O0019 Bioluminescence of Obelin; identification of the light emitters using QM/MM models Shufeng Chen(a,b) , Isabelle Navizet(c,e) , Roland Lindh(d) , Yajun Liu(b) , Nicolas Ferré(a) (a) Aix-Marseille Université, Marseille, France (b) Beijing Normal University, Beijing, China (c) Université Paris-Est, Marne-la-Vallée, France (d) Uppsala University, Uppsala, Sweden (e) University of Witwatersrand, Johannesburg, South Africa The chemiluminescent compound coelenterazine is related to the bioluminescence of a wide range of marine organisms, eg the Obelia Longissima hydrozoan. While the corresponding photochemical reaction (an oxidative decarboxylation of oxo-coelenterazine in which the coelenteramide product is in an excited electronic state) is commonly used as a luminescent probe,(1) the details of its mechanism are still unknown. In particular, the chemical nature of the light emitters responsible for the multi-modal bioluminescence and fluorescence emission spectra is still matter of debate. Up to now, the neutral coelenteramide molecule and its phenolate anion (obtained through a proton transfer towards the close His22 residue, hence forming an ion-pair) are the two most serious candidates.(2) Using hybrid QM/MM calculations,(3) we confirm the implication of the neutral coelenteramide in its first excited state as the primary light emitter (the computed TDDFT/MM vertical emission is 339 nm). However our results demonstrate that the postulated ion-pair is not a stable light emitter. Actually, an electron transfers together with the proton to form a diradical state (Fig. ) and the corresponding system ultimately evolves towards a point of degeneracy between the ground and first excited states. Hence a non-radiative decay path is suggested to compete with the light emission process. [Figure: see text] Alternatively, the phenolate coelenteramide is found to be a light emitter, as long as His22 looses another proton at the same time its accepts the one coming from coelenteramide, hence keeping its electric neutrality (the computed TDDFT/MM vertical emission is about 500 nm, in excellent agreement with the experimental λ(max) ). Our calculations show that the final location of the proton is not of primary importance. Finally, using the unique modeling capabilities of QM/MM calculations, and comparing our results with previous computations of coelenteramide in gas phase or in a solvent(4) , we assess the different contributions responsible for the color of the emitted light. Besides the protonation state of the luminophore, the steric constraints induced to the tight cavity in which coelenteramide is bound is the most important factor, far more than the electrostatic interaction with the protein. References 1. Frank LA, Borisova VV, Markova SV, Malikova NP, Stepanyuk GA, Vysotski ES. Violet and Greenish Photoprotein Obelin Mutants for Reporter Applications in Dual-color Assay. Anal. Bioanal. Chem. 2008;391:2891-2896. 2. Belogurova NV, Kudryasheva NS, Alieva RR, Sizykh AG. Spectral Components of Bioluminescence of Aequorin and Obelin. J. Photochem. Photobiol., B 2008;92:117-122. 3. Chen S-F, Navizet I, Lindh R, Liu Y-J, Ferré N. Hybrid QM/MM Simulations of the Obelin Bioluminescence and Fluorescence Reveal an Unexpected Light Emitter. J. Phys. Chem. B 2014 (in press, dx.doi.org/10.1021/jp412198w). 4. Chen S-F, Navizet, I, Roca-Sanjuá n D, Lindh R, Liu Y-J, Ferré N. Chemiluminescence of Coelenterazine and Fluorescence of Coelenteramide; A Systematic Theoretical Study. J. Chem. Theory Comput. 2012, 8, 2796-2807. O0020 Identification of a fluorescent compound from the bioluminescent polychaete Tomopteris Warren Francis(a,b) , Meghan Powers(a,b) , Steve Haddock(a) (a) Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA (b) University of California, Santa Cruz, Santa Cruz, CA, USA Tomopteris is a cosmopolitan genus of luminous polychaetes that release bright yellow particles from the parapodia when stimulated. Although the yellow bioluminescence of this genus has been the subject of a few investigations, the chemistry is essentially unstudied. All that is known is that the reaction does not involve any of the known molecules, like coelenterazine. The connection between fluorescence and bioluminescence has been a topic of great discussion. A brief report half a century ago described the yellow fluorescence of the parapodia with an identical similar spectrum to the bioluminescence, which suggested that it may be the luciferin or terminal light-emitter. Here we report the isolation of an abundant, fluorescent yellow-orange compound found in the luminous exudate and in the body of the animals. LCMS revealed the mass to be 270 m/z with a molecular formula of C15 H10 O5 , which ultimately was shown to be aloe-emodin, an anthraquinone previously found in various Aloe plant species. From known redox properties and chemiluminescence from other anthraquinones, we hypothesize that aloe-emodin is the oxyluciferin for Tomopteris bioluminescence. O0021 Chemiluminescent methods for explosives (TNT, TATP, HMTD) detection Stefano Girotti(a) , Elida Ferri(a) , Marcello D’Elia(b) , Mara Mirasoli(c) , Aldo Roda(c) , Luigi Ripani(d) , Giuseppe Peluso(d) , Roberta Risoluti(e) , Elisabetta Maiolini(a) , Francesco Saverio Romolo(f,g) (a) Dipartimento di Farmacia e Biotecnologie, Università di Bologna, Bologna,, Italy (b) Gabinetto Regionale di Polizia Scientifica per l’Emilia Romagna, Bologna, Italy (c) Dipartimento di Chimica, Università di Bologna, Bologna, Italy (d) Reparto Investigazioni Scientifiche (RIS) Carabinieri, Roma, Italy (e) Dipartimento di Chimica, Università “La Sapienza”, Roma, Italy (f) Institut de Police Scientifique, Université de Lausanne, Lausanne, Switzerland (g) Legal Medicine Section, Università “La Sapienza”, Roma, Jamaica The terroristic attacks performed in the last ten years have focused the attention on the protection and security of the citizen and the detection of various types of explosives is included in this purpose. Our work was finalised to develop chemiluminescent methods that permit the detection of TNT (2,4,6-trinitrotoluene), TATP (Triacetone triperoxide) and HMTD (Hexamethylene triperoxide diamine), displaying higher detectabilityand ease of use with respect to currently available methods (1-2). TNT is one of the most employed explosives in the 20th century and at the same time one possible well known environmental pollutant for its toxicity (3). For these reasons its detection could permit the prevention of terrorism acts (or the identification of the explosive used for these purposes) and for an early sign of environmental pollution. TATP (Triacetone triperoxide) and HMTD (Hexamethylene triperoxide diamine) are compounds extremely instable because they contain peroxide groups (4). Due to their simple synthesis, which requires, as reagents, compounds easily available at any supermarket, and that can be performed at home, they are frequently used in terrorist attacks. For TATP and HMTD we developed a chemiluminescent method that permits their indirect identification. Upon treatment with aci
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