Why is HSO so effective against bacteria? Insights into the mechanisms of Escherichia coli disinfection by unactivated peroxymonosulfate.

This study examined the antimicrobial efficacy of peroxymonosulfate (PMS) against bacteria, using Escherichia coli (E. coli) as a model organism. Our investigation delineates the complex mechanisms exerted by unactivated PMS.

BASHY Dyes Are Highly Efficient Lipid Droplet-Targeting Photosensitizers that Induce Ferroptosis through Lipid Peroxidation.

Ferroptosis is an iron-dependent lipid-peroxidation-driven mechanism of cell death and a promising therapeutic target to eradicate cancer cells. In this study, we discovered that boronic acid-derived salicylidenehydrazone (BASHY) dyes are highly efficient singlet-oxygen photosensitizers (PSs; Φ up to 0.8) that induce ferroptosis triggered by photodynamic therapy.

Synthesis of Bis(amino acids) Containing the Styryl-cyclobutane Core by Photosensitized [2+2]-Cross-cycloaddition of Allylidene-5(4)-oxazolones.

The irradiation of 2-aryl-4-(-3'-aryl-allylidene)-5(4)-oxazolones with blue light (456 nm) in the presence of [Ru(bpy)](BF) (bpy = 2,2'-bipyridine, 5% mol) gives the unstable cyclobutane-bis(oxazolones) by [2+2]-photocycloaddition of two oxazolones . Each oxazolone contributes to the formation of with a different C=C bond, one of them reacting through the exocyclic C=C bond, while the other does so through the styryl group. Treatment of unstable cyclobutanes with NaOMe/MeOH produces the oxazolone ring opening reaction, affording stable styryl-cyclobutane bis(amino acids) .

Engineering the BASHY Dye Platform toward Architectures with Responsive Fluorescence.

A set of nine boronic-acid-derived salicylidenehydrazone (BASHY) complexes has been synthesized in good to very good chemical yields in a versatile three-component reaction. In an extension to previous reports on this dye platform, the focus was put on the electronic modification of the "vertical" positions of the salicylidenehydrazone backbone. This enabled the observation of fluorescence quenching by photoinduced electron transfer (PeT), which can be reverted by the addition of acid in organic solvent (OFF-ON fluorescence switching).

Stereoselective, Ruthenium-Photocatalyzed Synthesis of 1,2-Diaminotruxinic Bis-amino Acids from 4-Arylidene-5(4)-oxazolones.

The irradiation of ()-2-phenyl-4-aryliden-5(4)-oxazolones in deoxygenated CHCl at 25 °C with blue light (465 nm) in the presence of [Ru(bpy)](BF) (5% mole ratio) as a triplet photocatalyst promotes the [2+2] photocycloaddition of the C═C bonds of the 4-arylidene moiety, thus allowing the completely regio- and stereoselective formation of cyclobutane-bis(oxazolone)s as single stereoisomers. Cyclobutanes have been unambiguously characterized as the μ-isomers and contain two -oxazolones coupled in an -head-to-head form. The use of continuous-flow techniques in microreactors allows the synthesis of cyclobutanes in only 60 min, compared with the 24-48 h required in batch mode.

Visible Light-Gated Organocatalysis Using a Ru -Photocage.

The light-gated organocatalysis via the release of 4-N,N-dimethylaminopyridine (DMAP) by irradiation of the [Ru(bpy) (DMAP) ] complex with visible light was investigated. As model reaction the acetylation of benzyl alcohols with acetic anhydride was chosen. The pre-catalyst releases one DMAP molecule on irradiation at wavelengths longer than 455 nm.

Assessing physical properties of amphoteric fluoroquinolones using phosphorescence spectroscopy.

The self-association of fluoroquinolones (FQ) in water would play a relevant role in their translocations across lipid membranes. Triplet excited states of these drugs have been shown as reporters of FQ self-association using laser flash photolysis technique. A study using low-temperature phosphorescence technique was performed with quinolone derivatives such as enoxacin (ENX), norfloxacin (NFX), pefloxacin (PFX), ciprofloxacin (CPX, ofloxacin (OFX), nalidixic acid (NLA), pipemidic acid (PPA) and piromidic acid (PRA) to explore emission changes associated with self-associations and to shed some light on the triplet excited state energy (E) discrepancies described in the literature for most of these drugs.

Chemical tuning for potential antitumor fluoroquinolones.

Phototoxic effects of 6,8 dihalogenated quinolones confers to this type of molecules a potential property as photochemotherapeutic agents. Two photodehalogenation processes seem to be involved in the remarkable photoinduced cellular damage. In this context, a new 6,8 dihalogenated quinolone 1 (1-methyl-6,8-difluoro-4-oxo-7-aminodimethyl-1,4-dihydroquinoline-3-carboxylic acid) was synthetized looking for improving the phototoxic properties of fluoroquinolones (FQ) and to determine the role of the photodegradation pathways in the FQ phototoxicity.

Electronic and Functional Scope of Boronic Acid Derived Salicylidenehydrazone (BASHY) Complexes as Fluorescent Dyes.

A series of boronic acid derived salicylidenehydrazone (BASHY) complexes was prepared and photophysically characterized. The dye platform can be modified by (a) electronic tuning along the cyanine-type axis via modification of the donor-acceptor pair and (b) functional tuning via the boronic acid residue. On the one hand, approach (a) allows the control of photophysical parameters such as Stokes shift, emission color, and two-photon-absorption (2PA) cross section.

Drug-DNA complexation as the key factor in photosensitized thymine dimerization.

The crucial role of photosensitizer@DNA complexation in the formation of cyclobutane pyrimidine dimers (CPDs) has been demonstrated using femtosecond and nanosecond transient absorption and emission measurements in combination with in vitro DNA damage assays. This finding opens the door to re-evaluate the mechanisms involved in CPDs photosensitized by other chemicals.

Biradical vs singlet oxygen photogeneration in suprofen-cholesterol systems.

Cholesterol (Ch) is an important lipidic building block and a target for oxidative degradation, which can be induced via free radicals or singlet oxygen ((1)O2). Suprofen (SP) is a nonsteroidal anti-inflammatory drug that contains the 2-benzoylthiophene (BZT) chromophore and has a π,π* lowest triplet excited state. In the present work, dyads (S)- and (R)-SP-α-Ch (1 and 2), as well as (S)-SP-β-Ch (3) have been prepared from β- or α-Ch and SP to investigate the possible competition between photogeneration of biradicals and (1)O2, the key mechanistic steps in Ch photooxidation.

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.

Steric shielding σ-π orbital interactions in triplet-triplet energy transfer.

The influence of non-covalent σ-π orbital interactions on triplet-triplet energy transfer (TTET) through tuning of the donor excitation energy remains basically unexplored. In the present work, we have investigated intermolecular TTET using donor moieties covalently linked to a rigid cholesterol (Ch) scaffold. For this purpose, diaryl ketones of π,π* electronic configuration tethered to α- or β-Ch were prepared from tiaprofenic acid (TPA) and suprofen (SUP).

Understanding of the photoallergic properties of fluoroquinolones: photoreactivity of lomefloxacin with amino acids and albumin.

Although the phototoxic and photoallergic properties of fluoroquinolone antibiotics (FQ) are remarkable, the mechanisms involved in these processes are not completely understood. For this reason, it is considered worthwhile to study in detail the photochemical interactions of lomefloxacin (LFX) and its N-acetyl derivative ALFX, two 6,8-dihalogenated fluoroquinolones, with the most abundant protein in human plasma (human serum albumin, HSA) to analyze their covalent binding. Fluorescence measurements and laser flash photolysis experiments performed in this work have revealed that N-acetylation of the LFX piperazinyl moiety produces an important increase of the drug affinity to albumin.

Seeking the mechanism responsible for fluoroquinolone photomutagenicity: a pulse radiolysis, steady-state, and laser flash photolysis study.

The mechanism responsible for the remarkable photomutagenicity of fluoroquinolone (FQ) antibiotics remains unknown. For this reason, it was considered worthwhile to study in detail the interactions between DNA and a dihalogenated FQ such as lomefloxacin (LFX; one of the most photomutagenic FQs) and its N-acetyl derivative ALFX. Studies of photosensitized DNA damage by (A)LFX, such as formation of DNA single-strand breaks (SSBs), together with pulse radiolysis, laser flash photolysis, and absorption and fluorescence measurements, have shown the important effects of the cationic character of the piperazinyl ring on the affinity of this type of drug for DNA.

Size-controlled photochemical synthesis of niobium nanoparticles.

The size of photochemically-prepared niobium nanoparticles (NbNP) can be controlled by varying the concentration of the photoinitiator in the reaction mixture. The particles, which may be metallic in nature, are readily oxidized upon air exposure to form stable niobium(v) oxide nanoparticles (NbONP) that act as strong Brønsted acids.

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.

Photoreactivity of fluoroquinolones: nature of aryl cations generated in water.

The nature of stabilized aryl cations generated from photodehalogenations of fluoroquinolones in aqueous media has been studied by comparing the photophysical and photochemical behavior of lomefloxacin (LFX) and its N(4')-acetylated form (ALFX). Photoproduct studies, laser flash photolysis, and emission measurements have shown that this small peripheral modification produces important changes in the properties of the singlet aryl cations generated. Also, in basic medium, a new photodehalogenation pathway for 6,8-dihalogenated fluoroquinolones has been observed.

Triplet excimers of fluoroquinolones in aqueous media.

Generation of triplet eximers of 6-fluoro-7-piperazinyl-quinolone-3-carboxylic acids (FQs) have been detected in aqueous media using laser flash photolysis (LFP). These transient species (SS) are generated by self-quenching reactions of FQ triplet excited states such as pefloxacin (PFX), norfloxacin (NFX), the N-acetylated form of NFX (ANFX), and its methyl ester (EANFX) with their ground states. In this context, self-quenching rate constants in the range of (1-7) × 10(8) M(-1) s(-1) were determined.

Seeking to shed some light on the binding of fluoroquinolones to albumins.

Interactions between serum albumins (HSA, human, and BSA, bovine) and fluoroquinolones (FQs), such as enoxacin, norfloxacin, ciprofloxacin, and ofloxacin, have been studied using the laser flash photolysis technique. Lifetimes and quantum yields of FQs triplet excited states ((3)FQs) are not affected by the presence of albumins, however, the quenching of (3)FQs by tryptophan and tyrosine and the subsequent generation of FQs radical anions and tyrosyl or tryptophanyl radicals were detected. These results, besides agreeing with association constants (K(a)) for FQs binding to albumins lower than 6 × 10(2) M(-1), are highly relevant to understanding the process of photohapten formation, the first event in the onset of photoallergy.

Solvent effects in hydrogen abstraction from cholesterol by benzophenone triplet excited state.

Hydrogen abstraction from the C-7 position of cholesterol (Ch) by triplet excited benzophenone (BZP) exhibits remarkable solvent-dependence in product studies. Kinetic measurements on the intramolecular version of the process in dyads containing covalently linked Ch and BZP units reveal important solvent effects and significant stereodifferentiation.

Tricationic porphyrin conjugates: evidence for chain-structure-dependent relaxation of excited singlet and triplet States.

Conjugates of 5-(4-carboxyphenyl)-10,15,20-tris(4-methylpyridinium-4-yl)porphyrin (P-H) are promising photoactive agents for medical applications. As their ultimate efficacy will depend on the behavior of initial excited states, photophysical parameters have been determined with conventional steady-state absorption and fluorescence as well as time-resolved femto- and nanosecond spectroscopies. The fluorescence quantum yield of P-H and P-H conjugated to uncharged groups increases from approximately 0.

Photosensitized DNA damage: the case of fluoroquinolones.

This review focuses on DNA damage photosensitized by the fluoroquinolone (FQ) antibacterial drugs. The in vivo evidence for photocarcinogenesis mediated by FQs is presented in the introduction. The different methods employed for detection of DNA-photodamage mediated by FQs are then summarized, including gel electrophoresis (with whole cells, with isolated DNA and with oligonucleotides) and chromatographic analysis (especially HPLC with electrochemical and MS/MS detection).

Photophysical properties of a photocytotoxic fluorinated chlorin conjugated to four beta-cyclodextrins.

A meso-tetrakis(pentafluorophenyl)-chlorin with the reduced pyrrole ring linked to an isoxazolidine ring (FC) has been conjugated to four beta-cyclodextrins (CDFC). The CDFC exhibits excellent water solubility and is a potent photosensitizer towards proliferating NCTC 2544 human keratinocytes. The study by conventional steady state absorption and fluorescence spectroscopies and by time-resolved femto- and nanosecond laser flash spectroscopies suggests that in ethanol and pH 7 buffer the beta-cyclodextrins embed the highly hydrophobic tetrakis(pentafluorophenyl)-chlorin macrocycle and strongly interact with the chlorin rings in the singlet and triplet manifolds.