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1.
We describe the synthesis and photophysical properties of a series of neutral and cationic 3,4-tetrapyridinoporphyrazines, potential lead photosensitizers for photodynamic inactivation of bacteria. Tetracationic TPyPzs exist essentially as monomers in aqueous systems, but the presence of trialkylated compounds due to incomplete quaternization of the outer nitrogen atoms induces severe aggregation. The absorption, fluorescence, triplet, and singlet oxygen quantum yields for both the neutral and cationic compounds are comparable to those of the related phthalocyanines. 相似文献
2.
ClaudiaG. Martínez Annette Neuner Cristina Martí Santi Nonell AndrM. Braun Esther Oliveros 《Helvetica chimica acta》2003,86(2):384-397
We have investigated the effect of a series of 18 solvents and mixtures of solvents on the production of singlet molecular oxygen (O2(1Δg), denoted as 1O2) by 9H‐fluoren‐9‐one (FLU). The normalized empirical parameter E derived from ET(30) has been chosen as a measure of solvent polarity using Reichardt's betaine dyes. Quantum yields of 1O2 production (ΦΔ) decrease with increasing solvent polarity and protic character as a consequence of the decrease of the quantum yield of intersystem crossing (ΦISC). Values of ΦΔ of unity have been found in alkanes. In nonprotic solvents of increasing polarity, ΦISC and, therefore, ΦΔ decrease due to solvent‐induced changes in the energy levels of singlet and triplet excited states of FLU. This compound is a poor 1O2 sensitizer in protic solvents, because hydrogen bonding considerably increases the rate of internal conversion from the singlet excited state, thus diminishing ΦΔ to values much lower than those in nonprotic solvents of similar polarity. In mixtures of cyclohexane and alcohols, preferential solvation of FLU by the protic solvent leads to a fast decrease of ΦΔ upon addition of increasing amounts of the latter. 相似文献
3.
M. Granet A. Nonell G. Favre F. Chartier H. Isnard J. Moureau C. Caussignac B. Tran 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
In the general frameworks of the nuclear fuel cycle and environmental research field, the Cs isotopic composition must be known with high precision and accuracy. The direct determination of Cs isotopes by mass spectrometry techniques is generally hampered by the presence of Ba isobaric interferences however. Here we present a new method which takes advantage of the collision-reaction cell based Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and allows to analyse Cs isotopes in the presence of Ba without prior separation step. The addition of N2O gas in the cell leads to an antagonistic behavior of Cs+ and Ba+ as the latter reacts with the gas to form BaO+ and BaOH+ products whereas Cs+ remains unreactive. The efficiency of the method was demonstrated for an UOx sample by comparing the results obtained (1) from the measurements of pure Cs fractions and (2) from Fission Products fractions containing more than 30 ionisable elements in addition to Cs, Ba, and where U and Pu were previously removed by using ion exchange resin. An excellent agreement is achieved between each set of experiments with an external reproducibility always better than 0.5% (RSD, k = 2). This study confirms the strong potential of collision–reaction cell to measure Cs isotopes in presence of interfering Ba, precluding therefore former systematic chemical separations. 相似文献
4.
Florence Guéguen Hélène Isnard Karsten Kossert Carole Bresson Céline Caussignac Guillaume Stadelmann Anthony Nonell Sébastien Mialle Frédéric Chartier 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(1):289-295
A methodology to purify a 166mHo solution has been developed by a combination of activity and mass concentration measurements in order to further determine the 166mHo half-life. The isobaric interference at m/q ? 166 requires Ho purification from non-natural Er with a high purification degree due to the large amount of Ho as opposed to Er. The Ho/Er separation was achieved using high-performance liquid chromatography on a semi-preparative column followed by purification on gravitational chromatography. The efficiency of the separation was evaluated after precise determination of the Er isotopic composition. The purification methodology enabled to separate Ho from Er. 相似文献
5.
H. Isnard M. Granet C. Caussignac E. Ducarme A. Nonell B. Tran F. Chartier 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009,64(11-12):1280-1286
In the nuclear domain, precise and accurate isotopic composition determination of elements in spent nuclear fuels is mandatory to validate neutron calculation codes and for nuclear waste disposal. The present study presents the results obtained on Cs isotope ratio by mass spectrometric measurements. Natural cesium is monoisotopic (133Cs) whereas cesium in spent fuels has 4 isotopes (133Cs, 134Cs, 135Cs, and 137Cs). As no standard reference material is available to evaluate the accuracy of Cs isotopic measurements, a comparison of cesium isotopic composition in spent nuclear fuels has been performed between Thermal Ionization Mass Spectrometry (TIMS) and a new method involving Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) measurements. For TIMS measurements, isotopic fractionation has been evaluated by studying the behavior of cesium isotope ratios (133Cs/137Cs and 135Cs/137Cs) during the analyses. For MC-ICPMS measurements, the mass bias effects have been corrected with an external mass bias correction using elements (Eu and Sb) close to cesium masses. The results obtained by the two techniques show good agreement: relative difference on 133Cs/137Cs and 135Cs/137Cs ratios for two nuclear samples, analyzed after chemical separation, ranges from 0.2% to 0.5% depending on the choice of reference value for mass bias correction by MC-ICPMS. Finally the quantification of the 135Cs/238U ratio by the isotope dilution technique is presented in the case of a MOx (mixed oxide) spent fuel sample. Evaluation of the global uncertainties shows that this ratio could be defined at an uncertainty of 0.5% (k = 2). The intercomparison between two independent mass spectrometric techniques is fundamental for the evaluation of uncertainty when no isotopic standard is available. 相似文献
6.
Dr. Xavier Ragàs Laurie P. Cooper Dr. John H. White Prof. Santi Nonell Dr. Cristina Flors 《Chemphyschem》2011,12(1):161-165
Fluorescent proteins are increasingly becoming actuators in a range of cell biology techniques. One of those techniques is chromophore‐assisted laser inactivation (CALI), which is employed to specifically inactivate the function of target proteins or organelles by producing photochemical damage. CALI is achieved by the irradiation of dyes that are able to produce reactive oxygen species (ROS). The combination of CALI and the labelling specificity that fluorescent proteins provide is useful to avoid uncontrolled photodamage, although the inactivation mechanisms by ROS are dependent on the fluorescent protein and are not fully understood. Herein, we present a quantitative study of the ability of the red fluorescent protein TagRFP to produce ROS, in particular singlet oxygen (1O2). TagRFP is able to photosensitize 1O2 with an estimated quantum yield of 0.004. This is the first estimation of a quantum yield of 1O2 production value for a GFP‐like protein. We also find that TagRFP has a short triplet lifetime compared to EGFP, which reflects relatively high oxygen accessibility to the chromophore. The insight into the structural and photophysical properties of TagRFP has implications in improving fluorescent proteins for fluorescence microscopy and CALI. 相似文献
7.
Santiago Nonell Silvia E. Braslavsky † Kurt Schaffner 《Photochemistry and photobiology》1990,51(5):551-556
The quantum yield of formation and kinetic behaviour of O2(1 delta g) in D2O dispersions of small unilamellar vesicles (SUVs) of dipalmitoyl phosphatidylcholine were studied by time-resolved detection of near-IR phosphorescence. At a SUV concentration of 26 nM, O2(1 delta g) is not quenched by the vesicles. It diffuses quickly through the lipid bilayer and a partition equilibrium of O2(1 delta g) between the lipid bilayer and the buffer is attained before decay occurs. In this equilibrium situation O2(1 delta g) is mostly located in the buffer phase, which permits the determination of absolute quantum yields for O2(1 delta g) production, phi delta, by comparison of the luminescence in the dispersions with that in neat D2O. The maximal phi delta values for the sensitizers incorporated in the SUV bilayer were 0.47 +/- 0.09 for the dipyridyl complex of zinc(II) phthalocyanine (ZnPc), 0.35 +/- 0.08 for porphycene, and 0.36 +/- 0.08 for 2,7,12,17-tetra-n-propylporphycene. These values are equal to those in neat organic solvents but lower than those previously obtained in SUVs by using chemical trapping agents. The high degree of organization of the environment around the sensitizers does not influence their efficiency of producing O2(1 delta g). While no concentration dependence is observed for ZnPc (at least up to a local concentration of 20 mM in the bilayer), phi delta for both porphycenes significantly decreases above a local concentration of 4 mM in the bilayer. This result is expected in view of previous observations on the concentration dependence of other photophysical parameters of the porphycenes in such microheterogeneous media. 相似文献
8.
Effects of Visible‐Light Irradiation of Protoporphyrin IX on the Self‐Assembly of Tubulin Heterodimers 下载免费PDF全文
Alicia Vall‐Sagarra Dr. Brady McMicken Prof. Santi Nonell Dr. Lorenzo Brancaleon 《Chemphyschem》2016,17(20):3269-3282
The formation and the effects of laser irradiation of the complex formed by protoporphyrin IX (PPIX) and tubulin was investigated. We have used tubulin as a model protein to investigate whether docked photoactive ligands can affect the structure and function of polypeptides upon exposure to visible light. We observed that laser irradiation in the Soret band prompts bleaching of the PPIX, which is accompanied by a sharp decrease in the intensity and average fluorescence lifetime of the protein (dominated by the four tryptophan residues of the tubulin monomer). The kinetics indicate non‐trivial effects and suggest that the photosensitization of the PPIX bound to tubulin prompts structural alterations of the protein. These modifications were also observed through changes in the energy transfer between Trp residues and PPIX. The results suggest that laser irradiation produces localized partial unfolding of tubulin and that the changes prompt modification of the formation of microtubules in vitro. Measurements of singlet oxygen formation were inconclusive in determining whether the changes are prompted by reactive oxygen species or other excited state mechanisms. 相似文献
9.
Flors C Ogilby PR Luis JG Grillo TA Izquierdo LR Gentili PL Bussotti L Nonell S 《Photochemistry and photobiology》2006,82(1):95-103
Experiments were performed to elucidate the excited-state behavior of 9-phenylphenalenones, which are phototoxic plant secondary metabolites involved in mechanisms of light-mediated plant defense. Using a combination of time-resolved and steady-state UV/visible spectroscopies, time-resolved IR absorption spectroscopy, time-resolved singlet oxygen phosphorescence measurements and cyclic voltammetry, we provide evidence of an intramolecular charge-transfer process in the excited singlet and the triplet states of 9-phenylphenalenones that modulates the photosensitized production of singlet oxygen. 相似文献
10.
Pedro F. Aramendia Robert W. Redmond Santiago Nonell Wolfang Schuster Silvia E. Braslavsky Kurt Schaffner Emanuel Vogel 《Photochemistry and photobiology》1986,44(5):555-559
Porphycene and a tetra-n-propyl derivative remained unaltered on irradiation in toluene at room temperature. Quantum yields of fluorescence, S T intersystem crossing, and singlet molecular oxygen sensitization, as well as lifetimes of the singlet and triplet excited states were measured. In view of their structural relationship to porphyrin, their high absorption above 620 nm, their stability towards photooxidation, and their high quantum yields of fluorescence and singlet oxygen sensitization, these compounds qualify as potential agents for tumor marking and photodynamic therapy. 相似文献