A fluorescence sensor for detection of geranyl pyrophosphate by the chemo-ensemble method.

Hexaamide receptor 4 and coumarin phosphate 5 form an ensemble for effective sensing of geranyl pyrophosphate (GPP). Fluorescence resonance energy transfer in the 4 + 5 ensemble diminishes when 5 is replaced by GPP. Receptor 4 binds selectively with GPP over other anions, including fatty acids. The 4-GPP complex in 1:1 stoichiometry is inferred by NMR and fluorescence titrations. Receptor 4 contains a pseudotetrahedral cleft to accommodate GPP via multiple hydrogen bonds, and the two aliphatic chains exert additional hydrophobic interactions.

Fluorescent organic nanoparticles of benzofuran-naphthyridine linked molecules: formation and fluorescence enhancement in aqueous media.

[structure: see text] Ethynyl-linked benzofuran-naphthyridine compounds show high-yield fluorescence with solvatochromic properties. One of the compounds, ABAN, has successfully formed fluorescent organic nanoparticles (FONs), for which the photophysical properties such as the spectral features and intensity are remarkably different from those at the molecular level (solution) and in bulk material. The results are tentatively rationalized by the FONs inducing coplanarization of the benzofuran-naphthyridine molecule to extend its effective conjugation length and hence increase the oscillator strength.

Stereoselective recognition of tripeptides guided by encoded library screening: construction of chiral macrocyclic tetraamide ruthenium receptor for peptide sensing.

[structure: see text] Molecule sensor 1 is devised by incorporating the reporting unit of ruthenium(II) complex and two recognition motifs of chiral cyclotetraamides on the sidearms. The target binding tripeptides for sensor 1 were readily identified by using an encoded library screening method. This solid-phase screening indicated a preferable binding of molecule 1 with d-alanine over the l-isomer. The optical and NMR studies for the binding events of 1 with tripeptides Ac-Ala-Gly-Ala-NHC(12)H(25) in the solution phase showed a consistent trend for the stereoselective recognition of the dd-isomer over the ld-, dl-, and ll-isomers.

Fluorescent and circular dichroic detection of monosaccharides by molecular sensors: bis[(pyrrolyl)ethynyl]naphthyridine and bis[(indolyl)ethynyl]naphthyridine.

The push-pull conjugated molecules 2,7-bis-(1H-pyrrol-2-yl)ethynyl-1,8-naphthyridine (BPN) and 2,7-bis(1H-indol-2-yl)ethynyl-1,8-naphthyridine (BIN) adopting daad relays of proton donors (d) and acceptors (a) form multiple hydrogen-bonding complexes with various monosaccharides that possess complementary adda sequences. Although the free BPN emits blue light at lambda(max) = 475 nm in CH(2)Cl(2), its complexation with octyl beta-d-glucopyranoside gives green fluorescence at lambda(max) = 535 nm. The excellent photophysical properties make BPN a highly sensitive probe for monitoring glucopyranoside to a detection limit of approximately 100 pM. On the other hand, the CD-silent BIN molecule binds with monosaccharides to form the CD-active multiple hydrogen-bonding complexes, which exhibit the remarkable chirality dependent helicities consistent with the prediction by the ab initio approaches. On the basis of the similar daad cleft and hence the binding property, the fluorescence and CD absorption methods in BPN and BIN, respectively, are complementary, which, in combination with computational molecular modeling, not only give a detailed insight into the structures of the receptor-saccharide complexes in solution, but also differentiate octyl beta-d-glucopyranoside from its enantiomer and other monosaccharides.

Two-arm ferrocene amide compounds: synclinal conformations for selective sensing of dihydrogen phosphate ion.

[structure: see text] Ferrocene compounds bearing multiple amido groups selectively bind with the H(2)PO(4)(-) ion over other anions. The one-arm receptors form 1:1 complexes with the H(2)PO(4)(-) ion, whereas the two-arm receptors can accommodate two H(2)PO(4)(-) ions. The complexation modes and binding strengths are deduced from the NMR, calorimetry, fluorescence, and cyclic voltammetry studies. The two-arm ferrocene hexamide receptors likely exist in synclinal conformations to incorporate tetrahydrofuran molecules and H(2)PO(4)(-) ions.

2,7-Bis(1H-pyrrol-2-yl)ethynyl-1,8-naphthyridine: an ultrasensitive fluorescent probe for glucopyranoside.

[structure: see text] A push-pull conjugated molecule, 2,7-bis(1H-pyrrol-2-yl)ethynyl-1,8-naphthyridine (BPN), has been designed to bind selectively with octyl glucopyranoside (OGU). The BPN/OGU quadruple hydrogen-bonding complex adopts a rigid BPN conformation in which the proton donor (d) and acceptor (a) relays (daad) are resonantly conjugated through the ethynyl bridge, inducing pi-electron delocalization, i.e., a charge transfer effect. The excellent photophysical properties make BPN a highly sensitive probe for monitoring glucopyranoside to a detection limit of approximately 100 pM.

A novel phosphate chemosensor utilizing anion-induced fluorescence change.

[structure: see text] The neutral receptor N,N'-bis[3,5-di[(1-pyrenylmethyl)carbamoyl]benzyl] pyridine-2,6-dicarbamide (2) provides a pseudo-tetrahedron cleft and multiple hydrogen bondings to form a 1:1 complex with phosphate ion in a highly selective manner, by comparison with other anions (F(-), Cl(-), Br(-), SCN(-), AcO(-), NO(3)(-), ClO(4)(-), and HSO(4)(-)). The binding strength can be inferred from the emission intensity ratio of the pyrene monomer (lambda(max) 377 nm) to the excimer (lambda(max) 477 nm). Fluorescence titration, X-ray analysis, and NMR studies support a proposed complexation model.