Hypocrellin B-based activatable photosensitizers for specific photodynamic effects against high H2O2-expressing cancer cells

A novel tumor-related biomarker, a H₂O₂-activatable photosensitizer 4 based on the 1,3-dicarbonyl enol moieties of hypocrellin B (3), was designed and synthesized. The photosensitizer 4 showed a blue-shifted absorption band compared with 3, and showed negligible photosensitizing ability without H₂O₂. However, the release of 3 from 4 by the reaction with H₂O₂ regenerated the photosensitizing ability. Furthermore, 4 exhibited selective and effective photo-cytotoxicity against high H₂O₂-expressing cancer cells upon photo-irradiation with 660 nm light, which is inside the phototherapeutic window.

2-Naphthol Moiety of Neocarzinostatin Chromophore as a Novel Protein-Photodegrading Agent and Its Application as a H2 O2 -Activatable Photosensitizer

A 2-naphthol derivative 2 corresponding to the aromatic ring moiety of neocarzinostatin chromophore was found to degrade proteins under photo-irradiation with long-wavelength UV light without any additives under neutral conditions. Structure-activity relationship studies of the derivative revealed that methylation of the hydroxyl group at the C2 position of 2 significantly suppressed its photodegradation ability. Furthermore, a purpose-designed synthetic tumor-related biomarker, a H₂ O₂ -activatable photosensitizer 8 possessing a H₂ O₂ -responsive arylboronic ester moiety conjugated to the hydroxyl group at the C2 position of 2, showed significantly lower photodegradation ability compared to 2. However, release of the 2 from 8 by reaction with H₂ O₂ regenerated the photodegradation ability. Compound 8 exhibited selective photo-cytotoxicity against high H₂ O₂ -expressing cancer cells upon irradiation with long-wavelength UV light.

Discovery of a Small-Molecule-Dependent Photolytic Peptide

We accidentally found that YM-53601, a known small-molecule inhibitor of squalene synthase (SQS), selectively depletes SQS from mammalian cells upon UV irradiation. Further analyses indicated that the photodepletion of SQS requires its short peptide segment located at the COOH terminus. Remarkably, when the 27 amino acid peptide was fused to green fluorescent protein or unrelated proteins at either the NH₂ or COOH terminus, such fusion proteins were selectively depleted when the cells were treated with both YM-53601 and UV exposure. Product analysis and electron spin resonance experiments suggested that the UV irradiation promotes homolytic C-O bond cleavage of the aryl ether group in YM-53601. It is likely that the radical species generated from UV-activated YM-53601 abstract hydrogen atoms from the SQS peptide, leading to the photolysis of the entire protein. The pair of the SQS peptide and YM-53601 discovered in the present study paves the way for the design of a new small-molecule-controlled optogenetic tool.

Inactivation of myostatin by photo-oxygenation using catalyst-functionalized peptides

Inhibition of myostatin is an attractive treatment for muscular dystrophy and other amyotrophic diseases. A myostatin-binding peptide was functionalized by equipped with an on/off switchable photo-oxygenation catalyst. This peptide induces a selective oxygenation of myostatin under near-infrared light, resulting in inactivation of myostatin. This peptide shows several orders of magnitude greater inhibitory effect than the original peptide.

2-Phenylquinoline-Sugar Hybrids as Photoswitchable α-Glucosidase Inhibitors

Purpose-designed 2-phenylquinoline (PQ)-sugar hybrids 1 and 2 were synthesized and evaluated for their photodegradation activities against an α-glucosidase target. The results indicated that PQ-mannose hybrid 2 selectively and effectively photodegraded α-glucosidase and significantly inhibited its enzymatic activity upon irradiation with long-wavelength UV light in the absence of any additives under neutral and aqueous conditions. Furthermore, 2 selectively and effectively inhibited α-glucosidase activity only with photo-irradiation even in complex cell lysate.

An anthraquinone–enzyme–peptide hybrid as a photo-switchable enzyme

The purpose-designed anthraquinone–horseradish peroxidase–cell penetrating peptide hybrid1exhibited cell permeability and enzymatic activity without photo-irradiation whereas significant self-degradation and loss of enzymatic activity occurred upon photo-irradiation in living cells.

Target-selective photo-degradation of AFP-L3 and selective photo-cytotoxicity against HuH-7 hepatocarcinoma cells using an anthraquinone–PhoSL hybrid

A purposefully-designed anthraquinone–Pholiota squarrosa lectin (PhoSL) hybrid effectively degraded α-fetoprotein-L3 (AFP-L3) associated with liver cancer.

Target-selective photo-degradation of a sialyl Lewis a (sLea) conjugate and photo-cytotoxicity against sLea positive cancer cells using an anthraquinone-antibody hybrid

A purpose-designed anthraquinone–monoclonal antibody (anti-sialyl Lewis A (sLe^a) mAb) hybrid 6 selectively bound to and effectively degraded the target glycoprotein, HSA (human serum albumin)–sLe^a conjugate 4.

Glycosylation of a newly functionalized orthoester derivative

Tandem glycosylation of the 6-O-Fmoc-substituted benzyl orthoester derivative 2a was carried out in moderate yields by electrogenerated acid (EGA). The Fmoc group was effectively removed under mild basic conditions, and the product was submitted to the subsequent glycosylation.