Photophysical and photochemical properties of electronically excited fluorescent dyes: a new type of time-resolved laser-scanning spectroscopy (original) (raw)
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Drug-biomolecule interactions in the excited states
Pure and Applied Chemistry, 2000
Drug-biomolecule interactions in the excited state are relevant from a photobiological point of view as they can be correlated with a number of photosensitization disorders such as photocarcinogenicity, photoallergy, phototoxicity, etc. Nonsteroidal antiinflammatory 2-arylpropionic acids and antibacterial fluoroquinolones have been selected as typical examples of photoactive drugs. Protein photosensitization has revealed photoadduct formation; the major amino acids involved are Tyr, Trp, and His. Generation of specific antibodies has allowed us to identify relevant structures of the drug epitopes. Then, drugs have been submitted to systematic steady-state and time-resolved studies on their photophysical properties, alone and in the presence of biomolecules: proteins, DNA, and their simple building blocks. The results are discussed in the framework of the chemical mechanisms underlying photosensitization by drugs and also in connection with the potential of drug excited states as (chiral) reporters for the binding sites of biomolecules.
International Journal of Pharmacy and Pharmaceutical Sciences, 2016
Objective: The main objective of this research work was to give insight from theory in interpreting electronic absorption spectra of tetrapyrrolic macrocycles bearing carboxylic acid groups: protoporphyrin IX, pheophorbide a and its 1-hydroxyethyl derivatives for application in photodynamic therapy. Methods: All calculations were carried out by using the Gaussian 03W version 6.0. Electronic excitation energies and oscillator strengths were computed as vertical excitations from the minima of the ground state structures by using ZINDO and TD-DFT approach in vacuo. The simulated spectra were obtained by using the GaussSum 2.2.0 program. Results: The results showed that chlorine compounds (pheophorbide a and its 1-hydroxyethyl derivative) display the red-most absorption (Qx Conclusion: The chlorin compounds bearing carboxylic acid groups were, however, more promising candidates to be utilized in PDT compared to the corresponding porphyrin compounds.) at longer wavelengths and their absorption were stronger than porphyrin compounds (protoporphyrin IX and its 1-hydroxyethyl derivative). On the other hand, the 1-hydroxyethyl derivatives were not able to red-shift the absorption compared to the parent compounds.
Photophysical, Electrochemical, and Theoretical Study of Protriptyline in Several Solvents
Journal of Physical Chemistry B, 2002
Photophysical and electrochemical properties of protriptyline hydrochloride (PTL-HCl) and its free base were measured in different solvents. Ground-state properties remain unchanged as a function of solvent or protonation state. The fluorescence quantum yield and lifetime, on the other hand, are solvent-dependent. Fluorescence lifetimes results were obtained from monoexponential decay fittings. Characterization of the 266 nm nanosecond laser flash photolysis species reveals the presence of the triplet-triplet transient intermediate at low-intensity conditions. At high laser intensities, two new transient intermediates were observed, which were assigned to the solvated electron and the radical cation. These species are formed through a biphotonic route, as shown with photonicity studies. The relatively high oxidation potentials measured for PTL-HCl and its free base corroborate the biphotonic process required for these species. These electrochemical studies also show that PTL-HCl is easier to oxidize than its free base. Singlet oxygen is established as one of the transient species following triplet-state formation. The PTL-HCl triplet state is probably involved in the dimer formation and other reactive intermediates, and therefore, it might be directly associated with the in vivo phototoxic effects observed for this drug.
2016
Objective: The main objective of this research work was to give insight from theory in interpreting electronic absorption spectra of tetrapyrrolic macrocycles bearing carboxylic acid groups: protoporphyrin IX, pheophorbide a and its 1-hydroxyethyl derivatives for application in photodynamic therapy. Methods : All calculations were carried out by using the Gaussian 03W version 6.0. Electronic excitation energies and oscillator strengths were computed as vertical excitations from the minima of the ground state structures by using ZINDO and TD-DFT approach in vacuo. The simulated spectra were obtained by using the GaussSum 2.2.0 program. Results : The results showed that chlorine compounds (pheophorbide a and its 1-hydroxyethyl derivative) display the red-most absorption (Q x ) at longer wavelengths and their absorption were stronger than porphyrin compounds (protoporphyrin IX and its 1-hydroxyethyl derivative). On the other hand, the 1-hydroxyethyl derivatives were not able to red-shi...
Chemical Physics Letters, 2004
The photoreaction of (5R)-5-menthyloxyfuran-2[5H]-one (1) into the adduct 2 in the presence of N-methylpyrrolidine (MeP) and several ketones in acetonitrile was investigated by time resolved absorption spectroscopy. The transient properties and the quenching rate constants of the ketone/1/MeP system are described for benzophenone, 4,4 0 -dimethoxybenzophenone, xanthone, acetophenone and methoxyacetophenone and compared with those where MeP is replaced by triethylamine.
Excited-state Properties and In Vitro Phototoxicity Studies of Three Phenothiazine Derivatives¶
Photochemistry and Photobiology, 2007
This work concerns a combined photophysical, photochemical and photobiological study of three drugs (psychotherapeutic agents) of the phenothiazine series: perphenazine, fluphenazine hydrochloride and thioridazine hydrochloride. The excited-state properties were first investigated by stationary and time-resolved fluorimetry and by laser flash photolysis. The spectral description was assisted by quantum-mechanical calculations with the INDO/1-CI method. In organic media the lowest excited singlet state was found to decay by fluorescence (small quantum yield) and mainly by intersystem crossing to the lowest triplet state, which is responsible for oxygen photosensitization (high yields of singlet oxygen production) and photodegradation. A further decay pathway in aqueous solutions was the photoionization process, which led to the formation of the phenothiazine radical cations and the solvated electron. After the preliminary study of the photobehavior in organic solvents and in water, the phototoxicity of the three drugs was investigated on various biological substrates through a series of in vitro assays under UVA irradiation. Photohemolysis of mouse erythrocytes and phototoxicity on cultured murine fibroblasts were observed for all three compounds. Lipid photoperoxidation was then investigated using linoleic acid as the unsaturated lipid model and isolated red blood cell membranes. The drug-induced photodamage was also evaluated on proteins by measuring the photosensitizing cross-linking in erythrocyte ghosts. The combined approach proved to be useful in understanding the mechanism by which these phenothiazine derivatives induce skin photosensitization. In particular, the photophysical properties of the compounds under investigation and the results of the study on their phototoxicity are in agreement with a mechanism that involves the radical cation of the drugs as a main intermediate. ¶Posted on the website on
Optics and Spectroscopy, 2010
Based on the density functional theory, quantum chemical calculations of the structure and elec tronic absorption spectra of the molecules D102, D149, and D205 of an indoline-thiazolidine series, which are used as sensitizers for solar cells, are performed. Circular dichroism spectra are predicted. The mecha nisms by which intra and intermolecular electron transfer occur upon excitation to a triplet state, as well as the relaxation mechanism, are described. The geometric and electronic structures of the molecules under study in the ground singlet and excited triplet states are considered, and the relation between their structure and photochemical properties is discussed.