Green-Light-Sensitive BODIPY Photoprotecting Groups for Amines.

We describe a series of easily accessible, visible-light-sensitive (λ > 500 nm) BODIPY (boron-dipyrromethene)-based photoprotecting groups (PPGs) for primary and secondary amines, based on a carbamate linker. The caged compounds are stable under aqueous conditions for 24 h and can be efficiently uncaged in vitro with visible light (λ = 530 nm). These properties allow efficient photodeprotection of amines, rendering these novel PPGs potentially suitable for various applications, including the delivery of caged drugs and their remote activation.

Phototunable liquid-crystalline phases made of nanoparticles.

The properties of liquid-crystalline (LC) hybrid systems made of inorganic nanoparticles grafted with photosensitive azo compounds are presented. For materials with a large density of azo ligands at the surface, the LC structure can be reversibly melted by UV light, and the return to the LC state does not require the absorption of visible light. For systems with a lower density of azo ligands, UV light causes shortening of the distance between metal sublayers in the lamellar phase. Interestingly, the azo derivatives attached to the nanoparticle surface show very different kinetics of cis/trans conformational change as compared to the free molecules. The cis form of free ligands in solution is stable for days, whereas the isomerization of molecules attached to the nanoparticle surface to the trans form takes only a few minutes. Apparently, owing to the crowded environment, azo ligands immobilized at a metal surface behave as they would in the condensed state.

Hydroxycinnamyl Derived BODIPY as a Lipophilic Fluorescence Probe for Peroxyl Radicals.

Herein, we describe the synthesis of a fluorescent probe NB-2 and its use for the detection of peroxyl radicals. This probe is composed of two receptor segments (4-hydroxycinnamyl moieties) sensitive towards peroxyl radicals that are conjugated with a fluorescent reporter, dipyrrometheneboron difluoride (BODIPY), whose emission changes depend on the oxidation state of the receptors. The measurement of the rate of peroxidation of methyl linoleate in a micellar system in the presence of 1.0 µM NB-2 confirmed its ability to trap lipid peroxyl radicals with the rate constant kinh = 1000 M-1·s-1, which is ten-fold smaller than for pentamethylchromanol (an analog of α-tocopherol). The reaction of NB-2 with peroxyl radicals was further studied via fluorescence measurements in methanol, with α,α'-azobisisobutyronitrile (AIBN) used as a source of radicals generated by photolysis or thermolysis, and in the micellar system at pH 7.4, with 2,2'-azobis(2-amidinopropane) (ABAP) used as a thermal source of the radicals. The reaction of NB-2 receptors with peroxyl radicals manifests itself by the strong increase of a fluorescence with a maximum at 612-616 nm, with a 14-fold enhancement of emission in methanol and a 4-fold enhancement in the micelles, as compared to the unoxidized probe. Our preliminary results indicate that NB-2 behaves as a "switch on" fluorescent probe that is suitable for sensing peroxyl radicals in an organic lipid environment and in bi-phasic dispersed lipid systems.

Red-light-sensitive BODIPY photoprotecting groups for amines and their biological application in controlling heart rhythm.

Control of biological function by the use of photoremovable protecting groups (PPGs) is a gateway towards many new medical developments. Herein, we report the synthesis and application of efficient and biocompatible BODIPY-based photoprotecting groups for amines, which are cleavable with red light in the phototherapeutic window region (λ > 650 nm). We use the most promising PPG for the protection of dopamine and apply it to control the beating frequency of human cardiomyocytes.