Synthesis of Mesodiphenylhelianthrene from 1-Aminoanthraquinone and the Structural Elucidation of Its Endoperoxide Species after Irradiation.

A safe, five-step synthetic route to yield the reliable chemical actinometer, mesodiphenylhelianthrene (MDH), is reported from a commercially available compound. Full characterization of the intermediates of the synthetic route and the final product MDH are presented together with four crystal structures of intermediates and MDH. The usage of the actinometer is described, and finally, the structure of the endoperoxide species (MDHPO), which is formed after irradiation of MDH, has been elucidated experimentally and theoretically.

Photostable Platinated Bacteriochlorins as Potent Photodynamic Agents.

Photodynamic therapy (PDT) is used to treat various cancerous diseases. Recently, we have demonstrated that platinated pyridyl-substituted porphyrins are potent agents for PDT with very high phototoxicity (IC50 down to 17 nM) and excellent phototoxic indices of higher than 5800 (p.i. = IC50(dark)/IC50(light)) [Rubbiani, R. et al., Chem. Commun. 2020, 56, 14373]. However, the absorption of porphyrins is not ideal for the treatment of larger tumors because they essentially do not absorb light between 650 and 850 nm. Herein, we report stable conjugates of a novel bacteriochlorin with cisplatin and transplatin. They exhibit extremely high phototoxicity (IC50 values down to 6 nM, irradiated with a 750 nm LED at a fluence of 5 J/cm2), very low dark toxicity, and thereby extremely high phototoxic indices up to 8300. Based on these exciting results, we believe that platinated bacteriochlorins are promising candidates for further investigation as novel PDT anticancer agents.

Highly Phototoxic Transplatin-Modified Distyryl-BODIPY Photosensitizers for Photodynamic Therapy.

We report the synthesis of the first transplatin-BODIPY conjugates for application in photodynamic therapy (PDT). The distyryl BODIPYs containing two iodine atoms were designed to absorb in the red region, easily undergo intersystem crossing for efficient singlet oxygen generation, and additionally offer the possibility for coordination with mono-activated transplatin. We were able to demonstrate that coordination of the BODIPYs with a mono-activated transplatin increases the phototoxic index of the photosensitizers significantly, giving rise to highly phototoxic distyryl BODIPY derivatives, of which one was shown to have the highest ever reported phototoxic index against any cell line. Furthermore, the photophysical mechanism of singlet oxygen generation in distyryl BODIPYs undergoing intramolecular charge transfer was studied experimentally and using time-dependent density functional theory.

Highly sensitive protein detection based on lanthanide chelates with antenna ligands providing a linear range of five orders of magnitude.

Protein detection is an important task for pharmaceutical and clinical research today. Numerous protein staining techniques exist but are limited regarding their sensitivity and often narrow linear quantification ranges. To the best of our knowledge, this is the first description of a novel class of lanthanide chelatators, which absorb in the lower energy region at 360 nm. The new compound (6,9-dicarboxymethyl-3-{4-([1,10]-phenanthrol-2-ylethinylphenyl-carbamoyl)-methyl}-3,6,9-triaza-)-undeca-1,11-dicarboxylic acid) was coupled to different proteins and showed highly sensitive protein detection limits in both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) (1.5 fmol of bovine serum albumin) as well as Dot Blot (100 amol of lysozyme). Furthermore, the novel compound shows an exceptionally broad linear quantification range over 5 orders of magnitude allowing applications that require the highest sensitivity alongside standard sensitivity. In addition, the new compound offers multiplexing capabilities.

Molecular structures and electronic transitions of 3,6-diphenyl-1,2-dithiin and its radical cation: a spectroelectrochemical and DFT study.

One-electron oxidation of 3,6-diphenyl-1,2-dithiin yields the corresponding radical cation. The product is stable at low temperatures and can be distinguished by a triplet EPR signal. Cyclic voltammetric, UV-vis spectroelectrochemical, and DFT studies were performed to elucidate its molecular structure and electronic properties. Time-dependent DFT calculations reproduce appreciably well the UV-vis spectral changes observed during the oxidation. The results reveal a moderately twisted structure of the 1,2-dithiin heterocycle in the radical cation.

Isoserine-based biotinylated photoaffinity probes that interact with penicillin-binding protein 1b.

The photolytic decomposition of trifunctional carbene generating photoaffinity probes in methanolic solution was studied, a cleavage reaction with butylamine in water, the conjugation with a ligand (moenomycin), and experiments that demonstrate that the fully armed probes interact with penicillin-binding protein 1b.