Suchergebnisse

2734 2742 14 23 ; S ; [EN] The properties of triplet excited states are markedly medium-dependent, which turns this species into valuable tools for investigating the microenvironments existing in protein binding pockets. Monitoring of the triplet excited state behavior of drugs within transport proteins (serum albumins and alpha(1)-acid glycoproteins) by laser flash photolysis constitutes a valuable source of information on the strength of interaction, conformational freedom and protection from oxygen or other external quenchers. With proteins, formation of spatially confined triplet excited states is favored over competitive processes affording ionic species. Remarkably, under aerobic atmosphere, the triplet decay of drug@protein complexes is dramatically longer than in bulk solution. This offers a convenient dynamic range for assignment of different triplet populations or for stereochemical discrimination. In this review, selected examples of the application of the laser flash photolysis technique are described, including drug distribution between the bulk solution and the protein cavities, or between two types of proteins, detection of drug-drug interactions inside proteins, and enzyme-like activity processes mediated by proteins. Finally, protein encapsulation can also modify the photoreactivity of the guest. This is illustrated by presenting an example of retarded photooxidation. Financial support by Spanish Government (CTQ2013-47872-C2-1-P) and Generalitat Valenciana (Prometeo II/2013/005) is gratefully acknowledged. Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Triplet Excited States as a Source of Relevant (Bio)Chemical Information. Current Topics in Medicinal Chemistry. 14(23):2734-2742. https://doi.org/10.2174/1568026614666141216100907

[EN] The properties of triplet excited states are markedly medium-dependent, which turns this species into valuable tools for investigating the microenvironments existing in protein binding pockets. Monitoring of the triplet excited state behavior of drugs within transport proteins (serum albumins and alpha(1)-acid glycoproteins) by laser flash photolysis constitutes a valuable source of information on the strength of interaction, conformational freedom and protection from oxygen or other external quenchers. With proteins, formation of spatially confined triplet excited states is favored over competitive processes affording ionic species. Remarkably, under aerobic atmosphere, the triplet decay of drug@protein complexes is dramatically longer than in bulk solution. This offers a convenient dynamic range for assignment of different triplet populations or for stereochemical discrimination. In this review, selected examples of the application of the laser flash photolysis technique are described, including drug distribution between the bulk solution and the protein cavities, or between two types of proteins, detection of drug-drug interactions inside proteins, and enzyme-like activity processes mediated by proteins. Finally, protein encapsulation can also modify the photoreactivity of the guest. This is illustrated by presenting an example of retarded photooxidation. ; Financial support by Spanish Government (CTQ2013-47872-C2-1-P) and Generalitat Valenciana (Prometeo II/2013/005) is gratefully acknowledged. ; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Triplet Excited States as a Source of Relevant (Bio)Chemical Information. Current Topics in Medicinal Chemistry. 14(23):2734-2742. https://doi.org/10.2174/1568026614666141216100907 ; S ; 2734 ; 2742 ; 14 ; 23

[EN] Direct absorption of UVB light by DNA may induce formation of cyclobutane pyrimidine dimers and pyrimidine-pyrimidone (6-4) photoproducts. The latter arise from the rearrangement of unstable oxetane intermediates, which have also been proposed to be the electron acceptor species in the photoenzymatic repair of this type of DNA damage. In the present work, direct photolysis of oxetanes composed of substituted uracil (Ura) or thymine (Thy) derivatives and benzophenone (BP) have been investigated by means of transient absorption spectroscopy from the femtosecond to the microsecond time-scales. The results showed that photoinduced oxetane cleavage takes place through an adiabatic process leading to the triplet excited BP and the ground state nucleobase. This process was markedly affected by the oxetane regiochemistry (head-to-head, HH, vs. head-to-tail, HT) and by the nucleobase substitution; it was nearly quantitative for all investigated HH-oxetanes while it became strongly influenced by the substitution at positions 1 and 5 for the HT-isomers. The obtained results clearly confirm the generality of the adiabatic photoinduced cleavage of BP/Ura or Thy oxetanes, as well as its dependence on the regiochemistry, supporting the involvement of triplet exciplexes. As a matter of fact, when formation of this species was favored by keeping together the Thy and BP units after splitting by means of a linear linker, a transient absorption at similar to 400 nm, ascribed to the exciplex, was detected. ; Financial support from the Spanish Government (RYC-2015-17737 and CTQ2017-89416-R) and from the Conselleria d'Educacio Cultura i Esport (PROMETEO/2017/075 and GRISOLIAP/2017/005) is gratefully acknowledged. ; Blasco-Brusola, A.; Vayá Pérez, I.; Miranda Alonso, MÁ. (2020). Regioselectivity in the adiabatic photocleavage of DNA-based oxetanes. Organic & Biomolecular Chemistry. 18(44):9117-9123. https://doi.org/10.1039/D0OB01974G ; S ; 9117 ; 9123 ; 18 ; 44

[EN] Benzophenone (BP) is present in a variety of bioactive molecules. This chromophore is able to photosensitize DNA damage, where one of the most relevant BP/ DNA interactions occurs with thymine (Thy). In view of the complex photoreactivity previously observed for dyads containing BP covalently linked to thymidine, the aim of this work is to investigate whether appropriate changes in the nature of the spacer could modulate the intramolecular BP/Thy photoreactivity, resulting in an enhanced selectivity. Accordingly, the photobehavior of a series of dyads derived from BP and Thy, separated by linear linkers of different length, has been investigated by steady-state photolysis, as well as femtosecond and nanosecond transient absorption spectroscopy. Irradiation of the dyads led to photoproducts arising from formal hydrogen abstraction or Paterno-Buchi (PB) photoreaction, with a chemoselectivity that was clearly dependent on the nature of the linking bridge; moreover, the PB process occurred with complete regio- and stereoselectivity. The overall photoreactivity increased with the length of the spacer and correlated well with the rate constants estimated from the BP triplet lifetimes. A reaction mechanism explaining these results is proposed, where the key features are the strain associated with the reactive conformations and the participation of triplet exciplexes. ; Financial support from the Spanish Government (RYC-2015-17737 and CTQ2017-89416-R) and from the Conselleria d'Educació Cultura i Esport (PROMETEO/2017/075 and GRISOLIAP/2017/005) is gratefully acknowledged. The authors would like to thank the use of RIAIDT-USC analytical facilities for the X-ray crystallography analysis. ; Blasco-Brusola, A.; Vayá Pérez, I.; Miranda Alonso, MÁ. (2020). Influence of the linking bridge on the photoreactivity of benzophenone-thymine conjugates. The Journal of Organic Chemistry. 85(21):14068-14076. https://doi.org/10.1021/acs.joc.0c02088 ; S ; 14068 ; 14076 ; 85 ; 21 ; Kraemer, K. H. (1997). Sunlight and skin cancer: ...

This is the peer reviewed version of the following article: M. Lineros-Rosa, M. A. Miranda, V. Lhiaubet-Vallet, Chem. Eur. J. 2020, 26, 7205, which has been published in final form at https://doi.org/10.1002/chem.202000123. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ; [EN] Photolabile protecting groups (PPGs) have been exploited in a wide range of chemical and biological applications, due to their ability to provide spatial and temporal control over light-triggered activation. In this work, we explore the concept of a new photocage compound based on the commercial UVA/UVB filter oxybenzone (OB; 2-hydroxy-4-methoxybenzophenone) for photoprotection and controlled release of carbonyl groups. The point here is that oxybenzone not only acts as a mere PPG, but also provides, once released, UV photoprotection to the carbonyl derivative. This design points to a possible therapeutic approach to reduce the severe photoadverse effects of drugs containing a carbonyl chromophore. ; This work was supported by the Spanish Government (project PGC2018-096684-B-I00) and the Universitat Politecnica de Valencia (FPI grant to M.L.-R.). Carmen Clemente Martínez is acknowledged for her technical help during the UPLC-HRMS experiments. ; Lineros-Rosa, M.; Miranda Alonso, MÁ.; Lhiaubet, VL. (2020). A Sunscreen-Based Photocage for Carbonyl Groups. Chemistry - A European Journal. 26(32):7205-7211. https://doi.org/10.1002/chem.202000123 ; S ; 7205 ; 7211 ; 26 ; 32 ; Silva, J. M., Silva, E., & Reis, R. L. (2019). Light-triggered release of photocaged therapeutics - Where are we now? Journal of Controlled Release, 298, 154-176. doi:10.1016/j.jconrel.2019.02.006 ; Klausen, M., Dubois, V., Verlhac, J., & Blanchard‐Desce, M. (2019). Tandem Systems for Two‐Photon Uncaging of Bioactive Molecules. ChemPlusChem, 84(6), 589-598. doi:10.1002/cplu.201900139 ; Brieke, C., Rohrbach, F., Gottschalk, A., Mayer, G., & Heckel, A. (2012). Light‐Controlled Tools. Angewandte ...

[EN] Polymethylene-linked bipyrimidine models have been designed with different C5 substitutions and bridge lengths. Selective irradiation of 2'-methoxyacetophenone (2M) with the bipyrimidine models affords cyclobutane pyrimidine dimers, even in the presence of bulky substituents. Substitution at CS affects both the relative triplet energies (E-T(rel)) of the pyrimidines (Pyr) and the steric hindrance toward intermolecular energy transfer and intramolecular triplet Pyr* quenching. Photophysical studies showed that alkyl substitution resulted in a significant decrease in the E-T(rel) value. Quenching of the triplet excited state of 2M by the Pyr derivatives was proven and established their quenching rate constants (k(q)). As a general trend, the thymine-containing compounds showed k(q) values higher than 10(9) M(-1)s(-1), while in the uracil and tert-butyluracil analogues, k(q) was markedly lower. These data are explained considering three different scenarios: (a) triplet energy transfer is the rate controlling step, (b) excited state cyclization is the rate controlling step, and (c) the rate controlling step switches along the reaction. Thus, by introducing variations in the substitution at C5, the length of the linking bridge, or the substrate concentration, it is possible to switch from a process governed by the intrinsic dimerization step to an energy transfer-controlled process. ; Financial support by the Spanish Government (PGC2018-096684 and O.R.A. for FPU14/05294) and Generalitat Valenciana (PROMETEO/2017/075) is gratefully acknowledged. ; Rodriguez-Alzueta, O.; Cuquerella Alabort, MC.; Miranda Alonso, MÁ. (2019). Triplet Energy Transfer versus Excited State Cyclization as the Controlling Step in Photosensitized Bipyrimidine Dimerization. The Journal of Organic Chemistry. 84(21):13329-13335. https://doi.org/10.1021/acs.joc.9b01423 ; S ; 13329 ; 13335 ; 84 ; 21

[EN] 2'-Methoxyacetophenone (2M) presents improved UVA absorption as compared with other acetophenone derivatives. On the basis of transient infrared spectroscopy it has been previously claimed that 2M is an interesting photosensitiser for cyclobutane pyrimidine dimers (CPDs) formation. In the present paper, a complete UV-Vis transient absorption spectroscopic characterisation of this compound is provided, including triplet-triplet spectra, triplet lifetimes and rate constants for quenching of 2M by a dimeric thymine derivative. Furthermore, generation of singlet oxygen has been proven by time-resolved near IR phosphorescence measurements. Overall, the obtained results confirm the potential of 2M as a DNA photosensitiser, not only for CPDs formation, but also for oxidative damage. ; Financial support by the Spanish Government (O.R-A., FPU14/05294 and CTQ2015-70164-P) and Generalitat Valenciana (PROMETEO/2017/075) is gratefully acknowledged. ; Rodriguez-Alzueta, O.; Cuquerella Alabort, MC.; Miranda Alonso, MÁ. (2019). Transient UV-vis absorption spectroscopic characterisation of 2 '-methoxyacetophenone as a DNA photosensitiser. Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy. 218:191-195. https://doi.org/10.1016/j.saa.2019.04.007 ; S ; 191 ; 195 ; 218 ; Jornet, D., Tormos, R., & Miranda, M. A. (2011). Photobehavior of Mixed nπ*/ππ* Triplets: Simultaneous Detection of the Two Transients, Solvent-Dependent Hydrogen Abstraction, and Reequilibration upon Protein Binding. The Journal of Physical Chemistry B, 115(36), 10768-10774. doi:10.1021/jp2051432 ; Antusch, L., Gaß, N., & Wagenknecht, H. (2016). Elucidation of the Dexter‐Type Energy Transfer in DNA by Thymine–Thymine Dimer Formation Using Photosensitizers as Artificial Nucleosides. Angewandte Chemie International Edition, 56(5), 1385-1389. doi:10.1002/anie.201610065 ; Liu, X.-L., Wang, J.-B., Tong, Y., & Song, Q.-H. (2013). Regioselectivity and Competition of the Paternò-Büchi Reaction and Triplet-Triplet Energy Transfer between ...

[EN] Rose Bengal (RB) is a widely used photocatalyst due to its high quantum yield of singlet oxygen (O-1(2)) formation. Hence, when RB has been employed for wastewater remediation, the observed photodegradation has been attributed to reaction between the pollutants and the O-1(2) formed (Type II mechanism). However, RB could also react, in principle, via electron transfer (Type I mechanism). Herein, competition between Type I vs Type II oxidation has been investigated for RB in the photodegradation of emerging pollutants such as diclofenac (DCF) and acetaminophen (ACP). In parallel, the photocatalyst perinaphthenone (PN) has also been evaluated for comparison. The degree of removal achieved for both pollutants in aerated/deaerated aqueous solutions irrespective of the employed photocatalyst does not support the involvement of O-1(2) as the main species responsible for removal of the pollutants. Photophysical experiments showed that the triplet excited states of RB and PN are efficiently quenched by both DCF and ACP. Moreover, O-1(2) emission was also quenched by DCF and ACP. Thus the contribution of Type I versus Type II in the photodegradation has been evaluated from the experimentally determined rate constants. Nevertheless, at the upper limit for the typical concentration of emerging pollutants (10(-5) M) photodegradation proceeds mainly via Type I mechanism. ; Financial support from Spanish Government (Grants SEV-2016-0683 and CTQ2012-38754-C03-03) and Generalitat Valenciana (Prometeo Program) is gratefully acknowledged. We also thank support from VLC/Campus. R. Martinez-Haya thanks financial support from Spanish Government (Grant SEV-2012-0267). ; Martínez-Haya, R.; Miranda Alonso, MÁ.; Marín García, ML. (2018). Type I vs Type II photodegradation of pollutants. Catalysis Today. 313:161-166. https://doi.org/10.1016/j.cattod.2017.10.034 ; S ; 161 ; 166 ; 313

[EN] Photosensitization by drugs is a problem of increasing importance in modern life. This phenomenon occurs when a chemical substance in the skin is exposed to sunlight. Photosensitizing drugs are reported to cause severe skin dermatitis, and indeed, it is generally advised to avoid sunbathing and to apply sunscreen. In this context, the nonsteroidal anti-inflammatory drug (NSAID) diclofenac is a photosensitive drug, especially when administered in topical form. In this work, efforts have been made to design and study an innovative pro-drug/pro-filter system containing diclofenac and the UVA filter avobenzone in order to develop a safer use of this topical drug. The design is based on the presence of a well-established photoremovable phenacyl group in the avobenzone structure. Steady-state photolysis of the dyad in hydrogen-donor solvents, monitored by UV-Vis spectrophotometry and HPLC, confirms the simultaneous photorelease of diclofenac and avobenzone. Laser flash photolysis and phosphorescence emission experiments allow us to gain insight into the photoactive triplet excited-state properties of the dyad. Finally, it is shown that avobenzone provides partial photoprotection to diclofenac from photocyclization to carbazole derivatives. ; The present work was supported by the Spanish Government (CTQ2015-70164-P, BES-2013-066566), Generalitat Valenciana (Prometeo/2017/075). ; Aparici-Espert, MI.; Miranda Alonso, MÁ.; Lhiaubet, VL. (2018). Sunscreen-Based Photocages for Topical Drugs: A Photophysical and Photochemical Study of A Diclofenac-Avobenzone Dyad. Molecules. 23(3):1-11. https://doi.org/10.3390/molecules23030673 ; S ; 1 ; 11 ; 23 ; 3 ; Siegel, R. L., Miller, K. D., & Jemal, A. (2018). Cancer statistics, 2018. CA: A Cancer Journal for Clinicians, 68(1), 7-30. doi:10.3322/caac.21442 ; Curtius, K., Wright, N. A., & Graham, T. A. (2017). An evolutionary perspective on field cancerization. Nature Reviews Cancer, 18(1), 19-32. doi:10.1038/nrc.2017.102 ; Brem, R., Guven, M., & Karran, P. (2017). ...

This is the peer reviewed version of the following article: Martínez-Haya, Rebeca, Miranda Alonso, Miguel Ángel, Marín García, Mª Luisa. (2017). Metal-Free Photocatalytic Reductive Dehalogenation Using Visible-Light: A Time-Resolved Mechanistic Study.European Journal of Organic Chemistry, 15, 2164-2169, which has been published in final form at http://doi.org/10.1002/ejoc.201601494. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving ; [EN] The reductive dehalogenation of organic bromides has been achieved in the presence of riboflavin (RF) as photocatalyst under visible-light irradiation. Specifically, benzyl bromide (2) and -bromoacetophenone (3) were quantitatively converted into toluene and acetophenone, respectively, by using amines as electron donors and iPrOH as hydrogen donor, whereas bromobenzene (1) did not react. The thermodynamics of the reduction of the radical anion of RF were evaluated by using the redox potentials of the species involved: The reaction was found to be thermodynamically exergonic for 2 and 3, but not expected to occur for bromobenzene (1). The viability of the different competing processes on the timescales of the corresponding singlet and triplet RF excited states ((RF)-R-1* and (RF)-R-3*) was analyzed by time-resolved techniques. The quenching of (RF)-R-1* by amines was very efficient, and comparison of the transient absorption spectra recorded in the absence and presence of amines additionally confirmed the efficient redox process between (RF)-R-1* and the amines. Moreover, RF- was quenched by bromides 2 and 3, but not by 1. Thus, a deeper understanding of the overall mechanism of the photocatalytic reductive reaction has been achieved, and the key role of the radical anion of the photocatalyst has been demonstrated. ; R. M.-H. acknowledges generous support from the Spanish Government (grant SEV-2012-0267). We also thank for support from the Ministerio de Economia y Competitividat (Project CTQ2012-38754-C03-03), ...

[EN] Photolyases are intriguing enzymes that take advantage of sunlight to restore lesions like cyclobutane pyrimidine dimers or (6-4) photoproducts. This work focused on the photoreductive process responsible for splitting of the azetidine ring proposed to occur during (6-4) photoproduct repair at a thymine-cytosine sequence. A model compound formed by photocycloaddition between thymine and 6-azauracil has been designed to mimic the elusive azetidine intermediate. The photoinduced electron transfer process has been investigated by means of steady-state and time-resolved fluorescence using photosensitizers with oxidation potentials in the singlet excited state ranging from -3.3 to -2.1V vs. SCE. Azetidine ring splitting and recovery of repaired bases were proven by HPLC analysis. ; The Spanish Government (CTQ2012-32621, CTQ2015-70164-P, RIRAAF RETICS RD12/0013/0009, Severo Ochoa program/SEV-2012-0267 and SVP-2013-068057 for A.B.F.-R. grant) and the Generalitat Valenciana (Prometeo II/2013/005) are gratefully acknowledged. We are indebted to Dr. G. Sastre for his collaboration in the mathematical treatment of some experimental results. ; Fraga Timiraos, AB.; Lhiaubet, VL.; Miranda Alonso, MÁ. (2016). Repair of a Dimeric Azetidine Related to the Thymine-Cytosine (6-4) Photoproduct by Electron Transfer Photoreduction. Angewandte Chemie International Edition. 55(20):6037-6040. https://doi.org/10.1002/anie.201601475 ; S ; 6037 ; 6040 ; 55 ; 20

The aim of the present paper is to explore the potential of radical-mediated dehydrogenation of bile salts (BSs), which is reminiscent of the enzymatic action of hydroxysteroid dehydrogenase enzymes (HSDH). The concept has been demonstrated using triplet carbonyls that can be efficiently generated upon selective UVA-excitation. Hydrogen atom transfer (HAT) from BSs to triplet benzophenone (BP) derivatives gave rise to radicals, ultimately leading to reduction of the BP chromophore with concomitant formation of the oxo-analogs of the corresponding BSs. The direct reactivity of triplet BP with BSs in the initial step was evaluated by determining the kinetic rate constants using laser flash photolysis (LFP). The BP triplet decay was monitored (lambda(max) = 520 nm) upon addition of increasing BS concentrations, and the obtained rate constant values indicated a reactivity of the methine hydrogen atoms in the order of C-3 C-12 C-7. The steady-state kinetics of the overall process, monitored through the disappearance of the typical BP absorption band at 260 nm, was much faster under N-2 than under O-2, also supporting the role of the oxygen-quenchable triplet in the dehydrogenation process. Furthermore, irradiation of deaerated aqueous solutions of sodium cholate in the presence of KPMe provided the oxo-analogs, 3[O], 7[O]-CA, 3[O]-CA and 7[O]-CA, arising from the HAT process. ; Financial support from the Spanish Government (Grants SEV-2012-0267 and CTQ2012-38754-C03-03), Generalitat Valenciana (Prometeo Program) and the Technical University of Valencia (Predoctoral FPI fellowship for P. Miro) is gratefully acknowledged. ; Miró Richart, P.; Marín García, ML.; Miranda Alonso, MÁ. (2016). Radical-mediated dehydrogenation of bile acids by means of hydrogen atom transfer to triplet carbonyls. Organic and Biomolecular Chemistry. 14(9):2679-2683. https://doi.org/10.1039/c5ob02561c ; S ; 2679 ; 2683 ; 14 ; 9

The aim of the present work is to develop two-channel emitters to probe local hydrophobicity by means of fluorescence quenching within different biomimetic supramolecular environments. To achieve this goal, the dansyl (Dns) and tryptophan (Trp) fluorophores have been covalently attached to cholic acid (CA) in order to ensure simultaneous incorporation of the two emitting units into the same compartment. In principle, the two fluorophores of the synthesized Dns-CA-Trp probes could either exhibit an orthogonal behavior or display excited state interactions. The fluorescence spectra of 3 beta-Dns-CA-Trp showed a residual Trp emission band at ca. 350 nm and an enhanced Dns maximum in the 500-550 nm region. This reveals a partial intramolecular energy transfer, which is consistent with the Dns and Trp singlet energies. Thus, the two photoactive units are not orthogonal; nevertheless, 3 beta-Dns-CA-Trp seems appropriate as a two-channel reporter for the supramolecular systems of interest. Fluorescence quenching of 3 beta-Dns-CA-Trp by iodide (which remains essentially in bulk water) was examined within sodium cholate, sodium taurocholate, sodium deoxycholate and mixed micelles. Interestingly, a decrease in the emission intensity of the two bands was observed with increasing iodide concentrations. The most remarkable effect was observed for mixed micelles, where the quenching rate constants were one order of magnitude lower than in solution. As anticipated, the quenching efficiency by iodide decreased with increasing hydrophobicity of the microenvironment, a trend that can be correlated with the relative accessibility of the probe to the ionic quencher. ; Financial support from the Spanish Government (CTQ2012-38754-C03-03), Predoctoral FPU fellowship (AP2008-03295), and the Generalitat Valenciana (Prometeo Program) is gratefully acknowledged. ; Gómez Mendoza, M.; Marín García, ML.; Miranda Alonso, MÁ. (2014). Two-channel dansyl/tryptophan emitters with a cholic acid bridge as reporters for local hydrophobicity within ...

8499 8504 12 42 ; S ; The aim of the present work is to develop two-channel emitters to probe local hydrophobicity by means of fluorescence quenching within different biomimetic supramolecular environments. To achieve this goal, the dansyl (Dns) and tryptophan (Trp) fluorophores have been covalently attached to cholic acid (CA) in order to ensure simultaneous incorporation of the two emitting units into the same compartment. In principle, the two fluorophores of the synthesized Dns-CA-Trp probes could either exhibit an orthogonal behavior or display excited state interactions. The fluorescence spectra of 3 beta-Dns-CA-Trp showed a residual Trp emission band at ca. 350 nm and an enhanced Dns maximum in the 500-550 nm region. This reveals a partial intramolecular energy transfer, which is consistent with the Dns and Trp singlet energies. Thus, the two photoactive units are not orthogonal; nevertheless, 3 beta-Dns-CA-Trp seems appropriate as a two-channel reporter for the supramolecular systems of interest. Fluorescence quenching of 3 beta-Dns-CA-Trp by iodide (which remains essentially in bulk water) was examined within sodium cholate, sodium taurocholate, sodium deoxycholate and mixed micelles. Interestingly, a decrease in the emission intensity of the two bands was observed with increasing iodide concentrations. The most remarkable effect was observed for mixed micelles, where the quenching rate constants were one order of magnitude lower than in solution. As anticipated, the quenching efficiency by iodide decreased with increasing hydrophobicity of the microenvironment, a trend that can be correlated with the relative accessibility of the probe to the ionic quencher. Financial support from the Spanish Government (CTQ2012-38754-C03-03), Predoctoral FPU fellowship (AP2008-03295), and the Generalitat Valenciana (Prometeo Program) is gratefully acknowledged. Gomez Mendoza, M.; Marín García, ML.; Miranda Alonso, MÁ. (2014). Two-channel dansyl/tryptophan emitters with a cholic acid bridge as reporters for local ...

[EN] Reactive oxygen species (ROS) can provoke damage to cells, where their concentrations are regulated by antioxidants. As the hydroxyl radical (center dot OH) is the most oxidizing ROS, we have focused our attention on the use of a mechanistically based time-resolved methodology, such as laser flash photolysis, to determine the relative reactivity of alcoholic beverages towards center dot OH as an indicator of their antioxidant potential. The selected drinks were of two different origins: (i) those derived from grapes such as red wine, white wine, white vermouth, marc and brandy and (ii) spirits not derived from grapes: triple sec, gin, whisky, and rum. Initially, we determined the quenching rate constant of ethanol with center dot OH and then we explored the reactivity of the different beverages, which was higher than expected based on their alcoholic content. This can be attributed to the presence of antioxidants and was especially remarkable for the grape-derived drinks. ; This research was funded by Spanish Government (Grant SEV-2016-0683) and Generalitat Valenciana (Prometeo Program). ; Rodriguez-Muniz, GM.; Miranda Alonso, MÁ.; Marín García, ML. (2019). A Time-Resolved Study on the Reactivity of Alcoholic Drinks with the Hydroxyl Radical. Molecules. 24(2):1-9. https://doi.org/10.3390/molecules24020234 ; S ; 1 ; 9 ; 24 ; 2 ; Nathan, C., & Ding, A. (2010). SnapShot: Reactive Oxygen Intermediates (ROI). Cell, 140(6), 951-951.e2. doi:10.1016/j.cell.2010.03.008 ; Buettner, G. R. (1993). The Pecking Order of Free Radicals and Antioxidants: Lipid Peroxidation, α-Tocopherol, and Ascorbate. Archives of Biochemistry and Biophysics, 300(2), 535-543. doi:10.1006/abbi.1993.1074 ; Treml, J., & Šmejkal, K. (2016). Flavonoids as Potent Scavengers of Hydroxyl Radicals. Comprehensive Reviews in Food Science and Food Safety, 15(4), 720-738. doi:10.1111/1541-4337.12204 ; Rodriguez-Muñiz, G. M., Gomis, J., Arques, A., Amat, A. M., Marin, M. L., & Miranda, M. A. (2014). Hydroxyl Radical as an Unlikely Key ...