An optically and thermally switchable electronic structure based on an anthracene-BODIPY conjugate.

An optically and thermally responsive boron dipyrromethene (BODIPY) dye, namely, meso-2-(9,10-dihydro-9,10-ethanoanthracene-11,12-dione) (DK)-linked, bicyclo[2.2.2]octadiene (BCOD)-fused BODIPY (BCOD-DK), was synthesized. The weakly luminous structure of BCOD-DK can be changed quantitatively to that of the strongly fluorescent BODIPY BCOD-Ant by optical excitation at the DK unit, which induces double decarbonylation of the DK unit to give an anthracene unit. The solvent effect on the fluorescence properties of BCOD-DK suggests that the dramatic change in fluorescence intensity is controlled by intramolecular electron transfer from the BODIPY moiety to the meso-DK substituent. BCOD-DK is converted to meso-DK benzene-fused BODIPY (Benzo-DK) by heating at 220 °C with 64-70 nm redshift of absorption and fluorescence peaks without changing the fluorescence quantum yield of ΦF =0.08 in dichloromethane. Benzo-DK can be converted to strongly fluorescent meso-anthracene benzene-fused BODIPY Benzo-Ant by optical excitation. Thus, BCOD-DK can show four different optical performances simply by irradiation and heating, and hence may be applicable for optical data storage and security data encryption.

Head-to-tail interaction between amphotericin B and ergosterol occurs in hydrated phospholipid membrane.

Amphotericin B (AmB) is thought to exert its antifungal activity by forming an ion-channel assembly in the presence of ergosterol. In the present study we aimed to elucidate the mode of molecular interactions between AmB and ergosterol in hydrated phospholipid bilayers using the rotational echo double resonance (REDOR) spectra. We first performed (13)C{(19)F}REDOR experiments with C14-(19)F-labeled AmB and biosynthetically (13)C-labeled ergosterol and implied that both "head-to-head" and "head-to-tail" orientations occur for AmB-ergosterol interaction in the bilayers. To further confirm the "head-to-tail" pairing, (13)C-labeled ergosterol at the dimethyl terminus (C26/C27) was synthesized and subjected to the REDOR measurements. The spectra unambiguously demonstrated the presence of a "head-to-tail" orientation for AmB-ergosterol pairing. In order to obtain information on the position of the dimethyl terminus of ergosterol in membrane, (13)C{(31)P}REDOR were carried out using the labeled ergosterol and the phosphorus atom of a POPC headgroup. Significant REDOR dephasing was observed at the C26/C27 signal of ergosterol in the presence of AmB, but not in the absence of AmB, clearly indicating that the side-chain terminus of ergosterol in the AmB complex comes close to the bilayer surface.

Direct interaction between amphotericin B and ergosterol in lipid bilayers as revealed by 2H NMR spectroscopy.

Although amphotericin B (AmB) is thought to exert its antifungal activity by forming transmembrane ion-permeable self-assemblies together with ergosterol, no previous study has directly proven AmB-ergosterol interaction. To establish the interaction, we measured (2)H NMR using deuterium-labeled sterols and AmB. The (2)H NMR spectra of deuterated ergosterol in palmitoyloleoylphosphatidylcholine (POPC) bilayers showed that fast axial diffusion of erogosterol was almost completely inhibited by the coexistence of AmB. Conversely, cholesterol mobility in POPC membrane was essentially unchanged with or without AmB. These results unequivocally demonstrate that ergosterol has significant interaction with AmB in POPC bilayers. In addition, we examined the mobility of AmB using deuterium-labeled AmB, and found that, although AmB is almost immobilized in sterol-free and cholesterol-containing POPC membranes, a certain ratio of AmB molecules acquires mobility in the presence of ergosterol. The similar mobility of AmB and ergosterol in POPC bilayers confirmed the idea of the direct intermolecular interaction between ergosterol and AmB.