Analysis of mebendazole binding to its target biomolecule by laser flash photolysis.

Mebendazole (MBZ) and related anticancer benzimidazoles act binding the β-subunit of Tubulin (TU) before dimerization with α-TU with subsequent blocking microtubule formation. Laser flash photolysis (LFP) is a new tool to investigate drug-albumin interactions and to determine binding parameters such as affinity constant or population of binding sites. The aim of this study was to evaluate the interactions between the nonfluorescent mebendazole (MBZ) and its target biomolecule TU using this technique.

Behavior of drug excited states within macromolecules: binding of colchicine and derivatives to albumin.

The aqueous solutions of colchicine (COL) and analogues such as colchiceine (CEI), and N-deacetylcolchiceine (DCEI) have been studied by laser flash photolysis (LFP) with and without the presence of human serum albumin (HSA) to determine the possible interactions between the drugs and the albumin. When irradiation of these drugs was performed in aqueous media, transient absorption species were not detected. However, triplet excited states of CEI and DCEI were detected when the experiments were carried out in the presence of albumin.

Photobehavior of mixed nπ*/ππ* triplets: simultaneous detection of the two transients, solvent-dependent hydrogen abstraction, and reequilibration upon protein binding.

In the present work, a systematic study on hydrogen abstraction by the excited triplet states of 4-methoxybenzophenone (1) and 4,4'-dimethoxybenzophenone (2) from 1,4-cyclohexadiene (3), 4-methylphenol (4), 1,2,3,4-tetrahydroquinoline (5), and 1-methyl-1,2,3,4-tetrahydroquinoline (6) in different media has been undertaken. Laser flash photolysis (LFP) revealed that in nonpolar solvents, 1 and 2 triplets have a nπ* configuration with the typical benzophenone-like T-T absorption spectrum (λ(max) ca. 525 nm).

Experimental and theoretical studies on the mechanism of photochemical hydrogen transfer from 2-aminobenzimidazole to nπ* and ππ* aromatic ketones.

This work has examined the photoreactivity of benzophenone (3), 2-benzoylthiophene (4), 4-methoxybenzophenone (5), 4,4'-dimethoxybenzophenone (6), and 4-carboxybenzophenone (7) with 2-aminobenzimidazole (1). Laser flash photolysis (LFP) revealed quenching of the aromatic ketone triplets by 1, leading to formation of ketyl radicals plus aminyl radical 1-H•. The quenching rate constants obtained for 3 (nπ* triplet) and 4 (ππ* triplet) were 6.

Experimental and theoretical (DFT) characterization of the excited states and N-centered radical species derived from 2-aminobenzimidazole, the core substructure of a family of bioactive compounds.

Fluorescence spectroscopy, laser flash photolysis (LFP), and density functional theory (DFT) calculations have been performed to understand the photobehavior of 2-aminobenzimidazole (1). The emission lifetime and quantum yield are solvent-dependent. Direct LFP of 1 at 266 nm in MeCN solution results in the generation of a transient identified as radical 1(-H)(*) by comparison with the species generated upon tert-butyl peroxide (ROOR) irradiation in the presence of 1.

Intramolecular NH/pi complexes of 2-allylaniline derivatives in the ground and excited states.

The photochemical and photophysical properties of three 8-allyl-1,2,3,4-tetrahydroquinolines (1a-c) have been studied. These compounds exhibit a 2-allylaniline-like photochemical behavior, undergoing photocyclization to lilolidines (3a-c). The absorption, emission, and excitation spectra of 1a-c, employing convenient model compounds for comparison, demonstrate the formation of a NH/pi intramolecular ground-state complex (AB).

Photogeneration and reactivity of 1,n-diphenyl-1,n-azabiradicals.

The 1,5-diphenyl-1,5-azapentanediyl biradical Ia was generated by photolysis of 1,2-diphenylazacyclopentane (pyrrolidine 1a). Among the reaction pathways followed by Ia, C-N bond reformation with ring closure was found to be the predominating process, as determined by separate irradiation of either of the pure enantiomers of 1a. Disproportionation was a minor process and took place only via H abstraction by the C5 benzylic radical.

Proton, electron and energy transfer processes in excited phenol-olefin dyads.

Dyads containing phenol and olefin subunits are versatile models for the investigation of proton, electron and energy transfer processes. As they are readily accessible, a number of analogues (allylphenols, cinnamylphenols and derivatives) have been prepared with a wide range of photophysical and photochemical properties. By means of appropriate structural modification of a very simple initial structure, it is possible to reproduce, at will, different types of behaviour.

Enhanced reactivity in OH/NH/pi polyfunctional systems through coupled proton/electron transfer in the excited state: the photocyclisation of 2-allyl-3-aminophenol.

The photocyclisation rate of 2-allyl-3-(or 5-)aminophenols (1, 4 and 8) is dramatically enhanced, when compared with reference compounds, as a consequence of a coupled proton/electron transfer process.

Characterisation of the lowest singlet and triplet excited states of S-flurbiprofen.

The photophysical properties of S-flurbiprofen [S-2-fluoro-alpha-methyl-4-biphenylacetic acid], a nonsteroidal anti-inflammatory drug, have been examined using steady-state and time-resolved spectroscopic techniques. The energy of its first singlet excited state is 99 kcal mol(-1). The fluorescence quantum yields and lifetimes (at 300 nm) have been determined in acetonitrile, methanol, hexane and PBS; they are in the range 0.

Selective fluorescence sensing of Li+ in an aqueous environment by a ferrocene-anthracene-linked dyad.

A new 1-(9-anthryl)-4-ferrocenyl-2-aza-1,3-butadiene showing selective fluorescence enhancement upon binding to lithium cations over other alkaline cations in aqueous environment has been conveniently synthesized and characterized. [structure: see text]

Stereoselectivity in the triplet decay of chiral benzophenone-naphthalene bichromophoric systems.

Chiral recognition in the intramolecular induced quenching of the methoxynaphthalene triplet by benzophenone has been observed by using diastereomeric bichromophores

Photogeneration of o-quinone methides from o-cycloalkenylphenols.

6-Alkylidenecyclohexa-2,4-dienones (o-quinone methides II) have been generated by photolysis of 2-(2'-cycloalkenyl)phenols 1 and trapped by methanol to give the ring-opened products 2. The best results have been obtained with the cyclohexenyl derivatives 1a, 1e, and 1f. In the case of the cyclopentenyl derivative 1b, photoproduct 2b was not observed, whereas only small amounts of 2c and 2d were formed from the seven- and eight-membered ring analogues 1c and 1d.

Entropy-controlled diastereoselectivity in the photocyclization of rigid derivatives of o-allylaniline.

Two rigid derivatives of o-allylaniline, namely 8-allyl-2-phenyl-1,2,3,4-tetrahydroquinoline (1b) and 7-(trans-2-cinnamyl)-2-methylindoline (1c), have been chosen as suitable systems to study the potential stereoselectivity of the photocyclization process. Photolysis of 1b leads to a mixture of diastereomeric lilolidines 4 (trans/cis), while 1cproduces a mixture of 4 (trans/cis) and the tetrahydropyrrolo[3,2,1-hi]indole derivatives 5 (trans/cis). To disclose whether the diastereoselectivity could be entropy dependent, photolysis of 1b and 1c has been performed at several temperatures.

Photoreactions of trans-1-o-Hydroxyphenyl-2-phenylcyclopropane.

The photochemistry of trans-1-o-hydroxyphenyl-2-phenylcyclopropane, trans-1, was studied under a variety of experimental conditions. Direct irradiation through quartz in cyclohexane gave rise mainly to ring-expanded products, 2-phenyl-3,4-dihydro-2H-benzopyran, 2, 2-benzyl-2,3-dihydrobenzofuran, 3, and 1-o-hydroxyphenylindan, 4. The major products, 2 and 3, are rationalized by intramolecular proton transfer.