Bahareh Shirinfar

Selective fluorescent detection of RNA in living cells by using imidazolium-based cyclophane

A water-soluble imidazolium-based fluorescent chemosensor senses RNA selectively through fluorescence enhancement over other biologically relevant biomolecules in aqueous solution at physiological pH 7.4. Fluorescence image detection of RNA in living cells such as onion cells, HeLa cells, and animal model cells was successfully demonstrated which displays a chelation-enhanced fluorescence effect. These affinities can be attributed to the strong electrostatic (C-H)(+)···A(-) ionic H-bonding and the aromatic moiety driven π-stacking of imidazolium-based cyclophane with the size-complementary major groove of RNA.

Fluorescent Imidazolium-Based Cyclophane for Detection of Guanosine-5′-triphosphate and I– in Aqueous Solution of Physiological pH

A new water-soluble and fluorescent imidazolium-anthracene cyclophane (1) effectively recognizes the biologically important GTP and I(-) over other anions in a 100% aqueous solution of physiological pH 7.4. Fluorescence and (1)H NMR spectra and ab initio calculations demonstrate that emission arises from the formation of an excimer state and quenching occurs upon GTP/I(-) binding through (C-H)(+)···A(-) hydrogen bond interactions.

A highly selective fluorescent chemosensor for guanosine-5?-triphosphate via excimer formation in aqueous solution of physiological pH

A new water-soluble and fluorescent imidazolium-anthracene cyclophane 1 effectively recognizes and differentiates the biologically important GTP and ATP in 100% aqueous solution of physiological pH 7.4. Fluorescence, (1)H-NMR spectra and ab initio calculations demonstrate that excimer formation and fluorescence enhancement occur upon GTP and ATP binding, respectively, through (C-H)(+)···A(-) hydrogen bond interactions.

Precise tuning of cationic cyclophanes toward highly selective fluorogenic recognition of specific biophosphate anions

Cationic cyclophanes with bridging and spacer groups possess well-organized semirigid cavities and are able to encapsulate and stabilize anionic species through diverse molecular interactions. We highlight the precise tuning of functionalized cyclophanes toward selective recognition of AMP, GTP, and pyrophosphate (PPi) using fluorescence, NMR spectroscopy, and density functional theory (DFT).

Selective detection of guanosine-5′-triphosphate and iodide by fluorescent benzimidazolium-based cyclophanes

New fluorescent benzimidazolium-based receptors selectively display the effective fluorescence quenching effect for biologically important anions, GTP and I(-), in aqueous solution of physiological pH 7.4. These affinities can be attributed to the strong ionic H-bonding along with additional interactions of fluorophore moieties with the nucleic base of GTP and I(-).

Fluorogenic sensing of CH3CO2− and H2PO4− by ditopic receptor through conformational change

Cyclo-bis-(urea-3,6-dichlorocarbazole) (1) forms a 1 : 2 complex with CH(3)CO(2)(-) and H(2)PO(4)(-) through hydrogen bonding with the two urea moieties, resulting in fluorescence enhancement via a combined photoinduced electron transfer (PET) and energy transfer mechanism. The binding mechanism involves a conformational change of the two urea receptors to a trans orientation after binding of the first anion, which facilitates the second interaction.

A new selective ‘turn-on’ small fluorescent cationic probe for recognition of RNA in cells

Fluorescent imaging probes have revolutionised cell biology by monitoring cellular objects. However, the lack of fluorescent probes with high selectivity for RNA has been a drawback. Thus, selective RNA binding for fluorescent sensors is essential. Here, we report the selective fluorescence enhancement upon addition of RNA. By exploiting a selective recognition of small tetra-cationic probe 1 for RNA, we also explain the possible binding mode for RNA. As a membrane-permeant fluorescence probe, 1 provides selective imaging of RNA not only in human neuroblastoma tumour SH-SY5Y cell line used for Parkinsons disease but also in the unicellular green alga cells. Further exploitation could open new opportunities in neurotoxin and cancer biology.

Facile Synthesis of a Selective Biomolecule Chemosensor and Fabrication of Its Highly Fluorescent Graphene Complex

A novel hydrophilic imidazolium fluorescent chemosensor has been utilized to prepare water-soluble fluorescent graphene complex via a facile ion-exchange strategy, which gives a very high quantum yield (0.87). The highly fluorescent graphene complex displays a close resemblance to the water-soluble fluorescent chemosensor, as the chemisorbed imidazolium hinders the electron transfer between the naphthalene moiety and the graphene. If the imidazolium is simply physisorbed on graphene by physical mixing, it does not show a high quantum yield because the π-π stacking between the naphthalene moiety and graphene leads to fluorescence quenching. The fluorescent chemosensor selectively detects RNA by turn-on fluorescence at physiological pH in aqueous solution. The fluorescent chemosensor as well as the fluorescent graphene complex would find potential applications as photoresponsive materials and biomedical probes.

Halides with Fifteen Aliphatic C-H···Anion Interaction Sites.

Since the aliphatic C–H···anion interaction is relatively weak, anion binding using hydrophobic aliphatic C–H (Cali–H) groups has generally been considered not possible without the presence of additional binding sites that contain stronger interactions to the anion. Herein, we report X-ray structures of organic crystals that feature a chloride anion bound exclusively by hydrophobic Cali–H groups. An X-ray structure of imidazolium-based scaffolds using Cali–H···A− interactions (A− = anion) shows that a halide anion is directly interacting with fifteen Cali–H groups (involving eleven hydrogen bonds, two bidentate hydrogen-bond-type binding interactions and two weakly hydrogen-bonding-like binding interactions). Additional supporting interactions and/or other binding sites are not observed. We note that such types of complexes may not be rare since such high numbers of binding sites for an anion are also found in analogous tetraalkylammonium complexes. The Cali–H···A− interactions are driven by the formation of a near-spherical dipole layer shell structure around the anion. The alternating layers of electrostatic charge around the anion arise because the repulsions between weakly positively charged H atoms are reduced by the presence of the weakly negatively charged C atoms connected to H atoms.

Synthesis, Designing and Analytical Applications of Nanostructured Ceria Based Materials

Cerium-based materials possess redox properties due to the presence of dual valence states of Ce3+ and Ce4+. In the last few years, the scientific community has paid much attention to designing and synthesizing cerium-based materials through advantageous routes for widespread catalytic and sensing applications in many fields. Cerium materials have been synthesized in many different forms, shapes and sizes. The catalytic and sensing capabilities of cerium nanostructures are highly dependent on their morphologies and can be improved significantly by modifying the sizes and shapes of the nanostructures to develop sensing scaffolds with improved sensing performance. These nanostructures provide a basis for applications in many fields. From a literature survey (2010 to 2015), it can be concluded that the fundamental morphologies, ratios, and capping of cerium nanostructures (CeNSs) constructively affect their properties and applications. Designed sensors utilizing CeNSs exhibit outstanding stability, high selectivity and eminent reproducibility in relation to time and temperature. This review will provide a perspective insight on the future trends in the design of different morphologies of CeNSs and their promising applications.