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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] Binding of the inmunodrepresive agent mycophenolate mofetil (MMP) and its pharmacologically active metabolite mycophenolic acid (MPA) to human serum albumin (HSA) and ¿1-acid glycoprotein (HAAG) has been investigated by an integrated approach involving selective excitation of the drug fluorophore, following their UV-A triggered fluorescence and docking studies. The formation of the protein/ligand complexes was evidenced by a dramatic enhancement of the fluorescence intensity and a hypsochromic shift of the emission band. In HSA, competitive studies using oleic acid as site I probe revealed site I as the main binding site of the ligands. Binding constants revealed that the affinity of the active metabolite by HSA is four-fold higher than its proactive form. Moreover, the affinity of MMP by HSA is three-fold higher than by HAAG. Docking studies revealed significant molecular binding differences in the binding of MMP and MPA to sub-domain IIA of HSA (site 1). For MPA, the aromatic moiety would be in close contact to Trp214 with the flexible chain pointing to the other end of the sub-domain; on the contrary, for MMP, the carboxylate group of the chain would be fixed nearby Trp214 through electrostatic interactions with residues Arg218 and Arg222. ; Financial support from the Spanish Ministry of Economy and Competiveness (CTQ2013-47872-C2-1-P, CTQ2016-78875-P, SAF2016-75638-R), the Xunta de Galicia (Centro singular de investigacion de Galicia accreditation 2016-2019, ED431G/09), the European Union (European Regional Development Fund-ERDF) and the Generalitat Valenciana (PROMETEO/2017/075) is gratefully acknowledged ; Vendrell-Criado, V.; González-Bello, C.; Miranda Alonso, MÁ.; Jiménez Molero, MC. (2018). A combined photophysical and computational study on the binding of mycophenolate mofetil and its major metabolite to transport proteins. Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy. 199:308-314. https://doi.org/10.1016/j.saa.2018.03.064 ; S ; 308 ; 314 ; 199

Cyamemazine (CMZ) is a neuroleptic drug that mediates cutaneous phototoxicity in humans. Here, the photobehavior of CMZ has been examined within (1)-acid glycoproteins, - and -cyclodextrins and SDS micelles. In all these microenvironments, CMZ emission was enhanced and blue-shifted, and its lifetime was longer. Irradiation of the entrapped drug at 355nm, under air; led to the N,S-dioxide. Within glycoproteins or SDS micelles the reaction was clearly slower than in phosphate buffered solution (PBS); protection by cyclodextrins was less marked. Transient absorption spectroscopy in PBS revealed formation of the triplet state ((3)CMZ*) and the radical cation (CMZ(+center dot)). Upon addition of glycoprotein, the contribution of CMZ(+center dot) became negligible, whereas (3)CMZ* dominated the spectra; in addition, the triplet lifetime became considerably longer. In cyclodextrins, this occurred to a lower extent. In all microheterogeneous systems, quenching by oxygen was slower than in solution; this was most remarkable inside glycoproteins. The highest protection from photooxidation was achieved inside SDS micelles. The results are consistent with photooxidation of CMZ through photoionization and subsequent trapping of the resulting radical cation by oxygen. This reaction is extremely sensitive to the medium and constitutes an appropriate probe for localization of the drug within a variety of biological compartments. ; Financial support from the Spanish Government (CTQ2010-14882, BES-2011-043706, JCI-2010-06204) and from the Generalitat Valenciana (PROMETEOII/2013/005) is gratefully acknowledged. ; Limones Herrero, D.; Pérez Ruiz, R.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Retarded photooxidation of cyamemazine in biomimetic microenvironments. Photochemistry and Photobiology. 90(5):1012-1016. https://doi.org/10.1111/php.12303 ; S ; 1012 ; 1016 ; 90 ; 5 ; Feinberg, A. P., & Snyder, S. H. (1975). Phenothiazine drugs: structure-activity relationships explained by a conformation that mimics dopamine. ...

[EN] The photoreactivity of diastereomeric dyads containing (S)- or (R)-flurbiprofen (FBP) and (S)-Tyr, either directly linked (1) or separated by a cyclic spacer (3) has been investigated. The main feature is a remarkable intramolecular quenching of FBP fluorescence, especially in 1. The process is clearly configuration dependent, being more efficient for the (R,S)- diastereomer in 1 and for the (S,S)-analogue in 3. Noteworthy, exciplex emission is detected in the 380-500 nm region in the case of 3. Fluorescence decay kinetics from the femtosecond to the nanosecond time-domains provides evidence for the dynamic nature of the quenching. In agreement with the steady-state and time-resolved observations, molecular modelling points to a more favourable geometric arrangement of the two interacting chromophores in 1 than in 3. ; Financial support from the Spanish Government (CTQ2013-47872-C2-1-P), EU (PCIG12GA-2012-334257, LASERLAB-EUROPE grant agreement no. 284464, EU FP7, and MSCA- 657465) and Generalitat Valenciana (PROMETEOII/2013/005) is gratefully acknowledged. ; Vayá Pérez, I.; Gustavsson, T.; Markovitsi, D.; Miranda Alonso, MÁ.; Jiménez Molero, MC. (2016). Influence of the spacer on the photoreactivity of flurbiprofen-tyrosine dyads. Journal of Photochemistry and Photobiology A: Chemistry. 322:95-101. https://doi.org/10.1016/j.jphotochem.2016.03.006 ; S ; 95 ; 101 ; 322

The radical anions of beta-lactams, photogenerated in the presence of DABCO as an electron donor, undergo cycloreversion via N-C4 bond cleavage, back electron transfer and final C2-C3 bond cleavage, leading to olefins. The involved intermediates are 1,4-radical anions and 1,4-biradicals. The experimental observations are consistent with the results of DFT calculations. ; Financial support from the Spanish Government (CTQ2013-47872-C2-1-P, SEV-2012-0267, BES-2011-043706, JCI-2010-06204), from CSIC (JAEDOC 101-2011 co-funded by FSE) and from the Generalitat Valenciana (PROMETEOII/2013/005) is gratefully acknowledged. J. A. S. acknowledges the computational facilities provided by the Theoretical Computational Chemistry Group of Prof. L. R. Domingo at the Universitat de Valencia. ; Pérez Ruiz, R.; Sáez Cases, JA.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Cycloreversion of beta-lactams via photoinduced electron transfer. Organic and Biomolecular Chemistry. 12(42):8428-8432. https://doi.org/10.1039/c4ob01416b ; S ; 8428 ; 8432 ; 12 ; 42 ; Von Nussbaum, F., Brands, M., Hinzen, B., Weigand, S., & Häbich, D. (2006). Antibacterial Natural Products in Medicinal Chemistry—Exodus or Revival? Angewandte Chemie International Edition, 45(31), 5072-5129. doi:10.1002/anie.200600350 ; β-Lactams in the New Millennium. Part-I: Monobactams and Carbapenems. (2004). Mini-Reviews in Medicinal Chemistry, 4(1), 69-92. doi:10.2174/1389557043487501 ; β-Lactams in the New Millennium. Part-II: Cephems, Oxacephems, Penams and Sulbactam. (2004). Mini-Reviews in Medicinal Chemistry, 4(1), 93-109. doi:10.2174/1389557043487547 ; Buynak, J. (2004). The Discovery and Development of Modified Penicillin- and Cephalosporin- Derived β-Lactamase Inhibitors. Current Medicinal Chemistry, 11(14), 1951-1964. doi:10.2174/0929867043364847 ; Veinberg, G., Vorona, M., Shestakova, I., Kanepe, I., & Lukevics, E. (2003). Design of β-Lactams with Mechanism Based Nonantibacterial Activities. Current Medicinal Chemistry, 10(17), 1741-1757. ...

224 230 13 ; S ; The photooxygenation of model compounds containing the two enantiomers of naproxen (NPX) covalently linked to histidine (His), tryptophan (Trp) and tyrosine (Tyr) has been investigated by steady state irradiation, fluorescence spectroscopy and laser flash photolysis. The NPX–His systems presented the highest oxygen-mediated photoreactivity. Their fluorescence spectra matched that of isolated NPX and showed a clear quenching by oxygen, leading to a diminished production of the NPX triplet excited state ( 3 NPX*–His). Analysis of the NPX–His and NPX–Trp photolysates by UPLC-MS–MS revealed in both cases the formation of two photoproducts, arising from the reaction of singlet oxygen (1 O2) with the amino acid moiety. The most remarkable feature of NPX–Trp systems was a fast and stereoselective intramolecular fluorescence quenching, which prevented the efficient formation of 3 NPX*–Trp, thus explaining their lower reactivity towards photooxygenation. Finally, the NPX–Tyr systems were nearly unreactive and exhibited photophysical properties essentially coincident with those of the parent NPX. Overall, these results point to a type II photooxygenation mechanism, triggered by generation of 1 O2 from the 3 NPX* chromophore Financial support from the Spanish Government (CTQ2010-14882, JCI-2011-09926, Miguel Servet CP11/00154), from the EU (PCIG12-GA-2012-334257), from the Universitat Politecnica de Valencia (SP20120757) and from the Conselleria de Educacio, cultura i Esport (PROMETEOII/2013/005, GV/2013/051) is gratefully acknowledged. Vayá Pérez, I.; Andreu Ros, MI.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Photooxygenation mechanisms in naproxen-amino acid linked systems. Photochemical & Photobiological Sciences Photochemical and Photobiological Sciences. 13:224-230. doi:10.1039/c3pp50252j L. I. Grossweiner and K. C.Smith, Photochemistry, in The Science of Photobiology, ed. K. C. Smith, Plenum Press, New York, 2nd edn, 1989, pp. 47–78 L. Pretali and A.Albini, in CRC Handbook of Organic ...

8428 8432 12 42 ; S Fischer, M. (1968). Photochemische Reaktionen, IV. Photochemische Fragmentierungen von β-Lactamen. Chemische Berichte, 101(8), 2669-2678. doi:10.1002/cber.19681010809 Eicher, T., Böhm, S., Ehrhardt, H., Harth, R., & Lerch, D. (1981). Zur Reaktion von Diphenylcyclopropenon, seinen funktionellen Derivaten und Imoniumsalzen mit Aminen. Liebigs Annalen der Chemie, 1981(5), 765-788. doi:10.1002/jlac.198119810503 ; The radical anions of beta-lactams, photogenerated in the presence of DABCO as an electron donor, undergo cycloreversion via N-C4 bond cleavage, back electron transfer and final C2-C3 bond cleavage, leading to olefins. The involved intermediates are 1,4-radical anions and 1,4-biradicals. The experimental observations are consistent with the results of DFT calculations. Financial support from the Spanish Government (CTQ2013-47872-C2-1-P, SEV-2012-0267, BES-2011-043706, JCI-2010-06204), from CSIC (JAEDOC 101-2011 co-funded by FSE) and from the Generalitat Valenciana (PROMETEOII/2013/005) is gratefully acknowledged. J. A. S. acknowledges the computational facilities provided by the Theoretical Computational Chemistry Group of Prof. L. R. Domingo at the Universitat de Valencia. Pérez Ruiz, R.; Sáez Cases, JA.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Cycloreversion of beta-lactams via photoinduced electron transfer. Organic and Biomolecular Chemistry. 12(42):8428-8432. doi:10.1039/c4ob01416b Von Nussbaum, F., Brands, M., Hinzen, B., Weigand, S., & Häbich, D. (2006). Antibacterial Natural Products in Medicinal Chemistry—Exodus or Revival? Angewandte Chemie International Edition, 45(31), 5072-5129. doi:10.1002/anie.200600350 β-Lactams in the New Millennium. Part-I: Monobactams and Carbapenems. (2004). Mini-Reviews in Medicinal Chemistry, 4(1), 69-92. doi:10.2174/1389557043487501 β-Lactams in the New Millennium. Part-II: Cephems, Oxacephems, Penams and Sulbactam. (2004). Mini-Reviews in Medicinal Chemistry, 4(1), 93-109. doi:10.2174/1389557043487547 Buynak, J. (2004). The ...

The photooxygenation of model compounds containing the two enantiomers of naproxen (NPX) covalently linked to histidine (His), tryptophan (Trp) and tyrosine (Tyr) has been investigated by steady state irradiation, fluorescence spectroscopy and laser flash photolysis. The NPX–His systems presented the highest oxygen-mediated photoreactivity. Their fluorescence spectra matched that of isolated NPX and showed a clear quenching by oxygen, leading to a diminished production of the NPX triplet excited state ( 3 NPX*–His). Analysis of the NPX–His and NPX–Trp photolysates by UPLC-MS–MS revealed in both cases the formation of two photoproducts, arising from the reaction of singlet oxygen (1 O2) with the amino acid moiety. The most remarkable feature of NPX–Trp systems was a fast and stereoselective intramolecular fluorescence quenching, which prevented the efficient formation of 3 NPX*–Trp, thus explaining their lower reactivity towards photooxygenation. Finally, the NPX–Tyr systems were nearly unreactive and exhibited photophysical properties essentially coincident with those of the parent NPX. Overall, these results point to a type II photooxygenation mechanism, triggered by generation of 1 O2 from the 3 NPX* chromophore ; Financial support from the Spanish Government (CTQ2010-14882, JCI-2011-09926, Miguel Servet CP11/00154), from the EU (PCIG12-GA-2012-334257), from the Universitat Politecnica de Valencia (SP20120757) and from the Conselleria de Educacio, cultura i Esport (PROMETEOII/2013/005, GV/2013/051) is gratefully acknowledged. ; Vayá Pérez, I.; Andreu Ros, MI.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Photooxygenation mechanisms in naproxen-amino acid linked systems. Photochemical & Photobiological Sciences Photochemical and Photobiological Sciences. 13:224-230. https://doi.org/10.1039/c3pp50252j ; S ; 224 ; 230 ; 13 ; L. I. Grossweiner and K. C.Smith, Photochemistry, in The Science of Photobiology, ed. K. C. Smith, Plenum Press, New York, 2nd edn, 1989, pp. 47–78 ; L. Pretali and A.Albini, in CRC ...

[EN] Four new dyes that derive from borylated arylisoquinolines were prepared, containing a third aryl residue (naphthyl, 4-methoxynaphthyl, pyrenyl or anthryl) that is linked via an additional stereogenic axis. The triaryl cores were synthesized by Suzuki couplings and then transformed into boronic acid esters by employing an Ir(I)-catalyzed reaction. The chromophores show dual emission behavior, where the long-wavelength emission band can reach maxima close to 600 nm in polar solvents. The fluorescence quantum yields of the dyes are generally in the range of 0.2¿0.4, reaching in some cases values as high as 0.5¿0.6. Laserflash photolysis provided evidence for the existence of excited triplet states. The dyes form fluoroboronate complexes with fluoride anions, leading to the observation of the quenching of the long-wavelength emission band and ratiometric response by the build-up of a hypsochromically shifted emission signal. ; Funding by the Spanish Ministry of Economy, Industry, and Competitiveness (CTQ2014-54729-C2-1-P for U.P., CTQ2013-48164-C2-1-P and CTQ2013-48164-C2-2-P for A.R., Ramon y Cajal contracts RYC-2013-12585 for A.R. and RYC-2015-17737 for I.V.), the Spanish Ministry of Science, Innovation, and Universities (CTQ2017-89832-P for U.P., CTQ2016-78875-P for M.C.J., and CTQ2017-89416-R for I.V.), the European Research and Development Fund, and the Andalusian Government (2012/FQM-2140 for U.P., 2009/FQM-4537 and 2012/FQM-1078 for A.R) is gratefully acknowledged. ; Pais, VF.; Neumann, T.; Vayá Pérez, I.; Jiménez Molero, MC.; Ros, A.; Pischel, U. (2019). Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence. Beilstein Journal of Organic Chemistry. 15:2612-2622. https://doi.org/10.3762/BJOC.15.254 ; S ; 2612 ; 2622 ; 15 ; Frath, D., Massue, J., Ulrich, G., & Ziessel, R. (2014). Lumineszierende Materialien: Fixierung von π-konjugierten und heterocyclischen Liganden mit Bor(III). Angewandte Chemie, 126(9), 2322-2342. doi:10.1002/ange.201305554 ; Ji, L., Griesbeck, ...

Four new dyes that derive from borylated arylisoquinolines were prepared, containing a third aryl residue (naphthyl, 4-methoxynaphthyl, pyrenyl or anthryl) that is linked via an additional stereogenic axis. The triaryl cores were synthesized by Suzuki couplings and then transformed into boronic acid esters by employing an Ir(I)-catalyzed reaction. The chromophores show dual emission behavior, where the long-wavelength emission band can reach maxima close to 600 nm in polar solvents. The fluorescence quantum yields of the dyes are generally in the range of 0.2–0.4, reaching in some cases values as high as 0.5–0.6. Laser-flash photolysis provided evidence for the existence of excited triplet states. The dyes form fluoroboronate complexes with fluoride anions, leading to the observation of the quenching of the long-wavelength emission band and ratiometric response by the build-up of a hypsochromically shifted emission signal. ; Funding by the Spanish Ministry of Economy, Industry, and Competitiveness (CTQ2014-54729-C2-1-P for U.P., CTQ2013- 48164-C2-1-P and CTQ2013-48164-C2-2-P for A.R., Ramón y Cajal contracts RYC-2013-12585 for A.R. and RYC-2015- 17737 for I.V.), the Spanish Ministry of Science, Innovation, and Universities (CTQ2017-89832-P for U.P., CTQ2016- 78875-P for M.C.J., and CTQ2017-89416-R for I.V.), the European Research and Development Fund, and the Andalusian Government (2012/FQM-2140 for U.P., 2009/FQM-4537 and 2012/FQM-1078 for A.R) is gratefully acknowledged.

2612 2622 15 ; S Frath, D., Massue, J., Ulrich, G., & Ziessel, R. (2014). Lumineszierende Materialien: Fixierung von π-konjugierten und heterocyclischen Liganden mit Bor(III). Angewandte Chemie, 126(9), 2322-2342. doi:10.1002/ange.201305554 ; [EN] Four new dyes that derive from borylated arylisoquinolines were prepared, containing a third aryl residue (naphthyl, 4-methoxynaphthyl, pyrenyl or anthryl) that is linked via an additional stereogenic axis. The triaryl cores were synthesized by Suzuki couplings and then transformed into boronic acid esters by employing an Ir(I)-catalyzed reaction. The chromophores show dual emission behavior, where the long-wavelength emission band can reach maxima close to 600 nm in polar solvents. The fluorescence quantum yields of the dyes are generally in the range of 0.2¿0.4, reaching in some cases values as high as 0.5¿0.6. Laserflash photolysis provided evidence for the existence of excited triplet states. The dyes form fluoroboronate complexes with fluoride anions, leading to the observation of the quenching of the long-wavelength emission band and ratiometric response by the build-up of a hypsochromically shifted emission signal. Funding by the Spanish Ministry of Economy, Industry, and Competitiveness (CTQ2014-54729-C2-1-P for U.P., CTQ2013-48164-C2-1-P and CTQ2013-48164-C2-2-P for A.R., Ramon y Cajal contracts RYC-2013-12585 for A.R. and RYC-2015-17737 for I.V.), the Spanish Ministry of Science, Innovation, and Universities (CTQ2017-89832-P for U.P., CTQ2016-78875-P for M.C.J., and CTQ2017-89416-R for I.V.), the European Research and Development Fund, and the Andalusian Government (2012/FQM-2140 for U.P., 2009/FQM-4537 and 2012/FQM-1078 for A.R) is gratefully acknowledged. Pais, VF.; Neumann, T.; Vayá Pérez, I.; Jiménez Molero, MC.; Ros, A.; Pischel, U. (2019). Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence. Beilstein Journal of Organic Chemistry. 15:2612-2622. https://doi.org/10.3762/BJOC.15.254 Ji, L., Griesbeck, S., & ...

[EN] Currently, evolution of chemical transformations by visible light irradiation is highly desirable from cost, safety, availability, and environmental friendliness points of view. Besides, activation of less reactive substrates under very mild conditions becomes one of the most challenging tasks in organic synthesis. However, the insufficient energy provided by one photon of visible light for their activation definitely makes necessary the development of new protocols together with the design of new photocatalytic systems to overcome this limitation. In this context, the implementation of biphotonic processes has been found to be a solution for these drawbacks. This new mechanistic paradigm which combines light upconversion processes with energy/electron transfers holds great potential for high energy demanding bond activations, expanding the accessible reactivity window. Here, we wish to highlight the recent applications of biphotonic processes in organic synthesis. ; Financial support from the Generalitat Valenciana (CIDEGENT/2018/044) and the Spanish Government (CTQ2016-78875-P, BES-2017-080215 and BEAGAL18/00166) is gratefully acknowledged. ; Castellanos-Soriano, J.; Herrera-Luna, JC.; Díaz Díaz, D.; Jiménez Molero, MC.; Pérez-Ruiz, R. (2020). Recent Applications of Biphotonic Processes to Organic Synthesis. Organic Chemistry Frontiers. 7(13):1709-1716. https://doi.org/10.1039/D0QO00466A ; S ; 1709 ; 1716 ; 7 ; 13 ; Scholes, G. D., Fleming, G. R., Olaya-Castro, A., & van Grondelle, R. (2011). Lessons from nature about solar light harvesting. Nature Chemistry, 3(10), 763-774. doi:10.1038/nchem.1145 ; Scholes, G. D., Mirkovic, T., Turner, D. B., Fassioli, F., & Buchleitner, A. (2012). Solar light harvesting by energy transfer: from ecology to coherence. Energy & Environmental Science, 5(11), 9374. doi:10.1039/c2ee23013e ; Demmig-Adams, B., Stewart, J. J., Burch, T. A., & Adams, W. W. (2014). Insights from Placing Photosynthetic Light Harvesting into Context. The Journal of Physical Chemistry ...

We report here on the interaction dynamics between flurbiprofen (FBP) and tryptophan (Trp) covalently linked in model dyads and in a complex of FBP with human serum albumin (HSA) probed by time-resolved fluorescence spectroscopy from the femto- to the nano-second timescales. In the dyads, a rapid (k > 10(10) s(-1)) dynamic quenching of the (FBP star)-F-1 fluorescence is followed by a slower (k > 10(9) s(-1)) quenching of the remaining (1)Trp(star) fluorescence. Both processes display a clear stereoselectivity; the rates are 2-3 times higher for the (R,S)-dyad. In addition, a red-shifted exciplex emission is observed, rising in the range of 100-200 ps. A similar two-step dynamic fluorescence quenching is also observed in the FBP-HSA complex, although the kinetics of the involved processes are slower. The characteristic reorientational times determined for the two enantiomeric forms of FBP in the protein show that the interaction is stronger for the (R)-form. This is, to our knowledge, the first observation of stereo-selective flurbiprofen-tryptophan interaction dynamics with femtosecond time resolution. ; Financial support from the Spanish Government (Grants CTQ2010-14882 and CTQ2009-13699, JCI-2011-09926, BES-2008-003314 and PR2011-0581), the Generalitat Valenciana (Prometeo 2008/090) and from the Universitat Politecnica de Valencia (PAID 05-11, Ref 2766) is gratefully acknowledged. ; Vayá Pérez, I.; Bonancía Roca, P.; Jiménez Molero, MC.; Markovitsi, D.; Gustavsson, T.; Miranda Alonso, MÁ. (2013). Excited state interactions between flurbiprofen and tryptophan in drug-protein complexes and in model dyads. Fluorescence studies from the femtosecond to the nanosecond time domains. Physical Chemistry Chemical Physics. 15(13):4727-4734. https://doi.org/10.1039/c3cp43847c ; S ; 4727 ; 4734 ; 15 ; 13 ; Carter, D. C., & Ho, J. X. (1994). Structure of Serum Albumin. Advances in Protein Chemistry, 153-203. doi:10.1016/s0065-3233(08)60640-3 ; Zimmermann, B., Hahnefeld, C., & Herberg, F. W. (2002). ...

The photochemical processes occurring in diastereomeric dyads (S, S)-1 and (S, R)-1, prepared by conjugation of (S)-2-(2-hydroxy-1,1'-biphenyl-4-yl) propanoic acid ((S)-BPOH) with (S)- and (R)-Trp, have been investigated. In acetonitrile, the fluorescence spectra of (S, S)-1 and (S, R)-1 were coincident in shape and position with that of (S)-BPOH, although they revealed a markedly stereoselective quenching. Since singlet energy transfer from BPOH to Trp is forbidden (5 kcal mol(-1) uphill), the quenching was attributed to thermodynamically favoured (according to Rehm-Weller) electron transfer or exciplex formation. Upon addition of 20% water, the fluorescence quantum yield of (S)-BPOH decreased, while only minor changes were observed for the dyads. This can be explained by an enhancement of the excited state acidity of (S)-BPOH, associated with bridging of the carboxy and hydroxy groups by water, in agreement with the presence of water molecules in the X-ray structure of (S)-BPOH. When the carboxy group was not available for coordination with water, as in the methyl ester (S)-BPOHMe or in the dyads, this effect was prevented; accordingly, the fluorescence quantum yields did not depend on the presence or absence of water. The fluorescence lifetimes in dry acetonitrile were 1.67, 0.95 and 0.46 ns for (S)-BPOH, (S, S)-1 and (S, R)-1, respectively, indicating that the observed quenching is indeed dynamic. In line with the steady-state and time-resolved observations, molecular modelling pointed to a more favourable geometric arrangement of the two interacting chromophores in (S, R)-1. Interestingly, this dyad exhibited a folded conformation in the solid state. ; Financial support from the Spanish Government (CTQ2010-14882, BES-2008-003314, JCI-2011-09926, PR2011-0581), from the Generalitat Valenciana (Prometeo 2008/090) and from the Universitat Politecnica de Valencia (PAID 05-11, 2766) is gratefully acknowledged. ; Bonancía Roca, P.; Vayá Pérez, I.; Markovitsi, D.; Gustavsson, T.; Jiménez Molero, MC.; Miranda ...