Biomedical subjects

Jiangli Fan

Publications and source records attributed to Jiangli Fan.

7 recordsLinked to original sources

PubMed2007

Fluorescence sensing of anions based on inhibition of excited-state intramolecular proton transfer.

Condensation of 2-(2'-aminophenyl)benzoxazole with p-toluenesulfonyl chloride and phenyl isocyanate yields two new anion sensors (TABO and PUBO), which can undergo excited-state intramolecular proton transfer (ESIPT) upon excitation. For the acid receptor TABO, the ESIPT process can be readily disturbed by basic anions such as F-, CH3COO-, and H2PO4- by deprotonating the sulfonamide unit, whereas in the case of PUBO, a good hydrogen-bonding donor, the ESIPT process is inhibited either by the fluoride-induced deprotonation of the urea unit or by the formation of a strong CH3COO--urea intermolecular hydrogen bond complex, and these two types of inhibition mechanisms consequently result in different ratiometric responses. But other anions with less hydrogen-bonding acceptor abilities cannot inhibit the ESIPT. Interestingly, the different inhibition abilities of F-, CH3COO-, and H2PO4- produce different spectral behaviors in PUBO, so this new sensor successfully distinguishes the subtle difference in these three anionic substrates of similar basicity and surface charge density.

Anions↗

PubMed2007

Simple bis-thiocarbono-hydrazones as sensitive, selective, colorimetric, and switch-on fluorescent chemosensors for fluoride anions.

Bis-thiocarbono-hydrazones are found to be a class of sensitive, selective, ratiometric, and colorimetric chemosensors for anions such as fluoride (F(-)) or acetate (Ac(-)). The sensitivities, or the binding constants of the sensors with anions, were found to be strongly dependent on the substituents appended on the pi-conjugation framework, the delocalization bridge CH==N, the aromatic moiety, and the hetero atom in the C==X group (X=O, S) of the sensors. Single-crystal structures and (1)H NMR titration analysis shows that the --CH==N-- moiety is a hydrogen-bond donor, and it is proposed that an additional CHF hydrogen bond is formed for the sensors in the presence F(-). A sensor bearing anthracenyl groups is demonstrated as a switch-on fluorescent chemosensor for F(-) and Ac(-). The recognition of F(-) in acetonitrile (MeCN) by a sensor with nitrophenyl substituents is tolerant to MeOH (MeCN/MeOH=10:1, v/v) and water (MeCN/H(2)O=30:1, v/v); at these solvent ratios the absorption intensity of the sensor-F(-) complex solution at maximal absorption wavelength was attenuated to half of the original value in pure MeCN.

Absorption↗

PubMed2006

A ratiometric fluorescent sensor for phosphates: Zn2+-enhanced ICT and ligand competition.

A pyrene-terpyridine-Zn conjugate has been synthesized and characterized, where Zn2+ acts as an electron acceptor to enhance molecular ICT with a large emission red-shift (>100 nm). It showed a ratiometric fluorescence change upon addition of phosphate anions in buffered aqueous solution. The selective response to phosphates or pyrophosphates involved ICT and ligand competition processes.

Journal Article↗

PubMed2005

Colorimetric and ratiometric fluorescence sensing of fluoride: tuning selectivity in proton transfer.

[reaction: see text] Phenyl-1H-anthra[1,2-d]imidazole-6,11-dione (1) and its derivatives (2 and 3) have been investigated as new colorimetric and ratiometric fluorescent chemosensors for fluoride. Acute spectral responses of 1 and 3 to fluoride in acetonitrile have been observed: an approximately 100 nm red shift in absorption and fluorescence emission and a very large ratiometric fluorescent response (Rmax/Rmin is 88 for sensor 1 and 548 for sensor 3). From the changes in the absorption, fluorescence, and 1H NMR titration spectra, proton-transfer mechanisms have been deduced. In ground states, a two-step process has been observed: first, the formation of the sensor-fluoride hydrogen-bond complex [LH...F]- and then the fluoride-induced deprotonation of the complex to form L- and FHF-. In excited states, the excited-state intermolecular proton-transfer made a contribution to the deprotonation. The selectivity for F- can be tuned by electron push-pull properties of the substituents on the phenyl para position of the sensors. Sensor 1 shows the best selectivity. The excellent selectivity of 1 for F- is attributed to the fitness in the acidity of its NH-group, which is tuned to be able to distinguish the subtle difference in the affinity of F-, CH3CO2(-), and H2PO4(-) to proton.

Journal Article↗

PubMed2005

Heptamethine cyanine dyes with a large stokes shift and strong fluorescence: a paradigm for excited-state intramolecular charge transfer.

New heptamethine cyanine dyes with an alkylamino group at the central position were found to exhibit a large Stokes shift (>140 nm) and strong fluorescence. They were suggested to be a new paradigm for excited-state intramolecular charge transfer (ICT). The configuration change of the bridgehead amine accompanying ICT was investigated in different viscosity and pH media.

Biosensing Techniques↗

PubMed2005

Boron dipyrromethene fluorophore based fluorescence sensor for the selective imaging of Zn(II) in living cells.

A simple PET fluorescence sensor (BDA) for Zn2+ that utilizes 1,3,5,7-tetramethyl-boron dipyrromethene as a reporting group and di(2-picolyl)amine as a chelator for Zn2+ has been synthesized and characterized. BDA has an excitation (491 nm) and emission wavelength (509 nm) in the visible range. The fluorescence quantum yields of the zinc-free and zinc-bound states of BDA are 0.077 and 0.857, respectively. With a low pKa of 2.1 +/- 0.1, BDA has the advantage of less sensitivity to pH than fluorescein-based Zn2+ sensors, and the fluorescence emission of zinc-binding is pH-independent in the range of pH 3-10. Under physiological conditions, metal ions such as Na+, K+, Ca2+, Mg2+, Mn2+ and Fe2+ have little interference. The apparent dissociation constant (Kd) is 1.0 +/- 0.1 nM. Using fluorescence microscopy, the sensor is shown to be capable of imaging intracellular Zn2+ changes.

Animals↗

PubMed2005

A novel fluorescent sensor for triplex DNA.

A triplex DNA fluorescent sensor based on PET is described. The sensor takes 4-aminonaphthalimide as a reporting group and a triplex-select intercalator as a recognizing group. The results show that it is a selective sensor for T.AT triplex DNA in compared with duplex and ssDNA by fluorescence enhancement in PIPES 20 buffer.

Biosensing Techniques↗