Synthesis, excited state properties, and dynamic structural change of photoresponsive dendrimers

AbstractThis article reviews recent advances in research of the dendrimer synthesis in connection with the design, synthesis and reaction of photoresponsive dendrimers. Dendrimers with photoreversible stilbene cores undergo mutual cis–trans isomerization in organic solvents to give photostationary state mixture of cis and trans isomers. Even the fourth generation (G4) stilbene dendrimer with molecular weight as high as 6500 underwent cis–trans photoisomerization within the lifetime of the excited singlet state. The large dendron group surrounding the photoreactive core may affect the excited state properties of the core to increase the efficiency of photoisomerization and/or decrease the fluorescence efficiency. The photochemistry of stilbene dendrimers with various types of dendron groups, and azobenzene dendrimers is discussed. Furthermore, recent advance of dendrimer syntheses and the possibility of their application to construct photoresponsive large molecules are discussed

Development of non-fluorescent imaging technique for biological application

科学研究費助成事業 研究成果報告書：挑戦的萌芽研究2013-2014 課題番号：2562012

Spatial Distributions of GABA Receptors and Local Inhibition of Ca2+ Transients Studied with GABA Uncaging in the Dendrites of CA1 Pyramidal Neurons

GABA(γ-amino-butylic acid)-mediated inhibition in the dendrites of CA1 pyramidal neurons was characterized by two-photon uncaging of a caged-GABA compound, BCMACM-GABA, and one-photon uncaging of RuBi-GABA in rat hippocampal slice preparations. Although we found that GABAA-mediated currents were diffusely distributed along the dendrites, currents elicited at the branch points of the apical dendritic trunk were approximately two times larger than those elsewhere in the dendrite. We examined the inhibitory action of the GABA-induced currents on Ca2+ transients evoked with a single back-propagating action potential (bAP) in oblique dendrites. We found that GABA uncaging selectively inhibited the Ca2+ transients in the region adjacent (<20 µm) to the uncaging site, and that GABA uncaging was effective only within a short period after bAP (<20 ms). The strength of inhibition was linearly related to the amplitudes of the GABA currents, suggesting that the currents inhibited a sustained, subthreshold after-depolarization without preventing propagation of bAP. GABA uncaging at the dendritic branch points inhibited Ca2+ transients farther into dendritic branches (>20 µm). Our data indicate that GABA inhibition results in spatially confined inhibition of Ca2+ transients shortly after bAP, and suggest that this effect is particularly potent at the dendritic branch points where GABA receptors cluster

無発光イメージング法確立に向けた分子開発

科学研究費助成事業 研究成果報告書：挑戦的萌芽研究2015-2016課題番号 : 15K1373

Photochemical properties of enediyne-cored dendrimers bearing naphthalenes at the periphery

ă A novel series of trans and cis enediyne-cored dendrimers bearing naphthalenes at the periphery were synthesized and their photochemical properties were examined. The trans/cis isomer ratio in the photostationary state was dependent on the excitation site in the dendrimers. When the enediyne core was selectively excited, the trans/cis isomer ratio in the photostationary state was either around 50/50 or a cis-rich mixture in all dendrimers due to the larger molar extinction coefficient of the trans-enediynes. On the other hand, when naphthalene was excited, a trans-rich mixture was unexpectedly obtained in higher generation dendrimers even though the energy transfer efficiency was almost quantitative in the trans dendrimers. These results could be explained by the energy transfer process, which was different depending on the geometric isomerism of the enediyne core.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

細胞小器官や膜ドメインを無蛍光イメージングするための分子開発

科学研究費助成事業 研究成果報告書：基盤研究(C)2018-2021課題番号 : 18K0531