10.1246/bcsj.67.3030
The research focuses on the photochemical one-way isomerization of 2-anthrylethylenes, specifically investigating the preparative methods and the quantum chain process involved in the cis-to-trans isomerization. The study aims to understand the high efficiency of this process and the factors contributing to it. The researchers used various chemicals, including 2-anthrylethylenes (la-d), Michler's ketone, biacetyl, and a range of dyes with different triplet energies, such as Rose Bengal, Eosin Y, erythrosine, fluorescein, Acridine Orange, and proflavine. The conclusions drawn from the research indicate that the isomerization efficiently proceeds through a quantum chain process, with the efficiency being slightly higher for 1b and 1c than for la. The high efficiency is attributed to the long lifetime of the triplet state, which enables its nearly thermoneutral energy transfer to take place effectively, competing with its relatively slow decay.
10.1021/ja027110l
This research aims to develop a novel off/on fluorescent chemosensor for the selective detection of histidine, an important amino acid in biochemistry and molecular biology. The study introduces a "chemosensing ensemble" approach, where a fluorescent indicator is bound to a receptor through noncovalent interactions, and the receptor quenches the indicator's fluorescence. When histidine is added, it displaces the indicator, restoring its fluorescence and signaling histidine's presence. The receptor used is the [CuII2(1)]4+ complex, which can interact with histidine's imidazole residue through CuII ions, providing selective recognition over other amino acids. The researchers tested three fluorescent indicators—coumarine 343, fluorescein, and eosine Y—with eosine Y showing the highest selectivity for histidine. The study concludes that the choice of fluorescent indicator is crucial for achieving selectivity in sensing, and the [CuII2(1)]4+/eosine Y ensemble provides the best discrimination of histidine from other amino acids. This work demonstrates a new strategy for designing selective fluorescent sensors for amino acids, which could have significant applications in biochemical analysis and molecular biology.
10.1002/anie.201915744
The research focuses on enhancing the photophysical properties of donor-acceptor (D-A) molecules by introducing a β-carbonyl substituent, which serves as a solvent-excluding group to mitigate excited state quenching mechanisms. The study involves the synthesis of a series of D-A fluorophores, including derivatives of 4-dialkylamino-7-nitro-benzoxadiazole (NBD), with β-carbonyl donors in various forms such as amides, esters, and thioesters. The photophysical properties of these fluorophores were experimentally analyzed through measurements of fluorescence quantum yield, brightness, and fluorescence lifetimes in different solvents. Fluorescein was used as a standard for measuring fluorescence quantum yields. Computational modeling and crystallographic characterizations were also employed to understand the structural basis of the observed enhancements. The results showed that the β-carbonyl substitution led to significant improvements in fluorescence quantum yields and brightness, particularly in polar solvents, by inhibiting both twisted intramolecular charge transfer (TICT) and external conversion (EC) pathways. This was achieved by increasing the energy barrier for rotation, which inhibited TICT, and by excluding solvent interactions through the orientation of the β-carbonyl group, which inhibited EC. The study demonstrates the potential of β-carbonyl modified D-A molecules for applications in live-cell imaging, offering brighter labeling probes.
10.1016/S0960-894X(97)00278-3
The research focuses on the synthesis of novel non-nucleosidic phosphoramidites and controlled pore glass (CPG) supports, which are based on a cyclohexyl-4-amino-1,1-dimethanol backbone. The purpose of this study was to develop a series of reagents that could be used to label oligonucleotides with biotin and fluorescein at various positions, including the 5'-, 3'-, and internal sites. The researchers aimed to improve the efficiency of synthesis and mimic the stereochemical properties of the natural polynucleotide backbone, while also keeping the reporter groups away from the oligonucleotide chain to enhance hybridization efficiency. The key chemicals used in the process included 3-cyclohexene-1,1-dimethanol, benzoyl chloride, sodium borohydride, BF3-Et2O, hydroxylamine-O-sulfonic acid, biotin-N-hydroxysuccinimide ester (biotin-NHSu), fluorescein-NHSu, and various other reagents for the protection, deprotection, and coupling steps. The conclusions of the research were that these novel biotin, fluorescein, and amino labeled phosphoramidites and CPG supports could be used advantageously for the introduction of multiple reporter groups onto oligonucleotides in a cost-effective and efficient manner, retaining the natural 3-carbon atom internucleotide phosphate distance in DNA/RNA, which does not affect the hybridization and annealing properties of the duplex.
Xi
