FRET-based modified graphene quantum dots for direct trypsin quantification in urine.

A versatile nanoprobe was developed for trypsin quantification with fluorescence resonance energy transfer (FRET). Here, fluorescence graphene quantum dot is utilized as a donor while a well-designed coumarin derivative, CMR2, as an acceptor. Moreover, bovine serum albumin (BSA), as a protein model, is not only served as a linker for the FRET pair, but also a fluorescence enhancer of the quantum dots and CMR2.

A coumarin-based fluorescent probe for recognition of Cu(2+) and fast detection of histidine in hard-to-transfect cells by a sensing ensemble approach.

A coumarin-based fluorescent chemosensor CAQA has been synthesized. It can selectively and sensitively recognize Cu(2+) in aqueous acetonitrile solutions. Using the Cu-containing complex CAQA-Cu(2+) as a sensing ensemble, the device demonstrates highly selective recognition of His/biothiols and was applied in fluorescence imaging of histidine in hard-to-transfect living cells.

N-Acetyl-l-cysteine capped quantum dots offer neuronal cell protection by inhibiting beta (1-40) amyloid fibrillation.

This is the first work that revealed the neuro-protective effect of functionalized quantum dots against the cytotoxicity induced by beta-amyloid peptides. This study gives insight into the future treatment of Alzheimer's disease. It opens many avenues for the development of the next generation nanotechnology for biomedical and therapeutic applications.

Ultrasound, pH, and magnetically responsive crown-ether-coated core/shell nanoparticles as drug encapsulation and release systems.

Core@shell nanoparticles with superparamagnetic iron oxide core, mesoporous silica shell, and crown ether periphery were fabricated toward drug delivery and tumor cell imaging. By the concept of nanovalve based on supramolecular gatekeeper, stimuli-responsive drug delivery nanosystems Fe3O4@SiO2@meso-SiO2@crown ethers were synthesized by (i) modified solvothermal reaction; (ii) sol-gel reaction; and (iii) amide coupling reaction. The successful coupling of the dibenzo-crown ethers onto the mesoporous silica shell was confirmed by thermogravimetric analysis and Infrared spectroscopy.

Effect of surface-functionalized nanoparticles on the elongation phase of beta-amyloid (1-40) fibrillogenesis.

The influence of nanoparticles of various sizes and surface functionalities on the self-assembling fibrillogenesis of beta-amyloid (1-40) peptide was investigated. Functionalized nanoparticles including quantum dots and gold nanoparticles were co-incubated with monomeric Aβ(1-40) peptides under seed-mediated growth method to study their influences on the elongation phase of the fibrillogenesis. It is observed that charge-to-surface area ratio of the nanoparticles and the functional moiety and electrostatic charges of the conjugated ligands on the particle surfaces took crucial regulatory role in the Aβ(1-40) fibrillogenesis.

Ratiometric fluorescent probe for enantioselective detection of D-cysteine in aqueous solution.

A ratiometric fluorescent probe based on a Cd(2+)-ACAQ complex was designed and demonstrated for the chemo- and enantioselective detection of cysteine in 99:1 buffered HEPES:ACN solutions. Under the measuring conditions, the sensor demonstrates high selectivity toward Cys against Hcy and GSH, and an enantioselectivity of 3.35 can be achieved for antipodal forms of Cys.

Chiral sulfonimide as a Brønsted acid organocatalyst for asymmetric Friedel-Crafts alkylation of indoles with imines.

Binaphthyl-based chiral sulfonimide (CSI) is demonstrated for the first time to be an efficient, strong Brønsted acid in asymmetric organocatalysis. A series of CSIs were synthesized and screened in the asymmetric Friedel-Crafts alkylation of indoles with imines. Good to excellent yields and enantioselectivities have been achieved.

Anthracene capped isobenzofuran: a synthon for the preparations of iptycenes and iptycene quinones.

Anthracene capped isobenzofuran 5 (5,6-(9,10-dihydroanthracen-9,10-yl)isobenzofuran) was synthesized for the first time. It is a highly reactive and versatile synthon for the synthesis of iptycene derivatives via Diels-Alder reactions. Cycloadducts 10 could be readily deoxygenated to iptycenes 11.

An easy assembled fluorescent sensor for dicarboxylates and acidic amino acids.

Two mesitylene based neutral receptors 1 and 2 bearing two thiourea binding sites were constructed as fluorescent probes for sensing dicarboxylates. Their binding affinities toward dicarboxylates, aspartate and glutamate have been investigated in acetonitrile solution by fluorescence titration experiments. Both fluorescent sensors exhibited some ability to discriminate the antipodal forms of aspartate and glutamate.

Oxadisilole fused triptycene and extended triptycene: precursors of triptycyne and extended triptycyne.

With benzobisoxadisilole 1 as a 1,4-benzdiyne equivalent, oxadisilole fused triptycene 5 and extended triptycene 6 were synthesized. Triptycenes 5 and 6 are new precursors of triptycyne 7 and extended triptycyne 8 respectively via the phenyliodination/fluoride induced elimination protocol. Using these two arynes, a series of triptycene derivatives were synthesized.

A colorimetric and fluorescent turn-on chemosensor operative in aqueous media for Zn2+ based on a multifunctionalized spirobenzopyran derivative.

By conjugating spiropyran chloride 8 with 2-amino-N-(quinolin-8-yl)acetamide (5), multifunctionalized spirobenzopyran derivative SPQN was designed and synthesized as a water soluble colorimetric and fluorescent turn-on chemosensor for Zn(2+). In 50% aqueous ethanol buffer solution, SPQN displayed a selective chelation fluorescence enhancement (16-fold) at 650 nm and visible color change (from colorless to red) with Zn(2+) among the metal ions examined. In addition, as the third channel to display the metal binding characteristics of SPQN, operating on an efficient FRET process between the quinoline and the merocyanine moiety of the sensor, ratiometric determination of Zn(2+) can be realized.

Quantum dot-mediated photoproduction of reactive oxygen species for cancer cell annihilation.

While semiconductor quantum dots produce little singlet oxygen, they may undergo Type I photoreactions to produce other reactive oxygen species (ROS) to kill cells. CdTe quantum dots coated with thioglycolic acid were used to test that possibility. Some thiol ligands were purposely removed to regenerate the surface electron traps that were passivated by the ligand.

Inhibition of beta 1-40 amyloid fibrillation with N-acetyl-L-cysteine capped quantum dots.

One of the primary factors that induce Alzheimer's disease (AD) is the deposition of beta-amyloid (Abeta). The Abeta molecules can self-assemble to form neurotoxic aggregates with various morphologies, such as dimers, oligomers, protofibrils and fibrils. For this aspect, we demonstrated that the amyloid fibrillation can be inhibited by quenching the nucleation and elongation processes with a low concentration of water dispersed N-acetyl-L-cysteine capped quantum dots (NAC-QDs).

Camphor sulfonyl hydrazines (CaSH) as organocatalysts in enantioselective Diels-Alder reactions.

Cyclic sulfonyl hydrazine was demonstrated for the first time as a new functionality for organocatalysis. A series of six-membered cyclic hydrazines derived from camphor sulfonic acid were synthesized. With trichloroacetic acid as cocatalyst, they are efficient organocatalysts for enantioselective Diels-Alder reactions with good chemical yields and up to 96% ee.

Tunable photochromism of spirobenzopyran via selective metal ion coordination: an efficient visual and ratioing fluorescent probe for divalent copper ion.

In the present paper, a new spirobenzopyran derivative was synthesized and applied in simultaneously colorimetric and fluorescence ratiometric detections of Cu2+. In contrast to the virtually photochromic character of the common spirobenzopyrans in most organic solvents, this spirobenzopyran is colorless in organic aqueous solution even irradiating by ultraviolet light. The formation of red merocyanine in an ethanol-aqueous solution is only induced by Cu2+ coordination.

Cholic acid-based fluorescent probes for enantioselective recognition of trifunctional amino acids.

The ditopic fluorescent photoinduced electron transfer (PET) amino acid sensory probes and were designed and synthesized from cholic acid. To confer the probes with specific binding ability, an amidothiourea moiety and a cyclic diamino-chiral receptive site were introduced on the C17 side chain and the C7 and C12 hydroxyl pendants, respectively. In acetonitrile, the probes demonstrated differential binding toward trifunctional amino acids like serine, lysine, threonine and tyrosine against other simple amino acids.

A cholic acid-based fluorescent chemosenor for the detection of ATP.

A novel ditopic cholic acid-based fluorescent chemosensor for ATP, 1a, was designed and synthesized. Its interactions with phosphates, AMP, ADP, ATP, CTP, GTP, and TTP have been investigated. When ATP was added to a 1:1 aqueous CH3CN solution of the sensor at pH 7.

Enantiomeric separation and quantification of ephedrine-type alkaloids in herbal materials by comprehensive two-dimensional gas chromatography.

The separation of ephedrine-type alkaloids and their enantiomers in raw herbs and commercial herbal products was investigated by carrying out enantioselective separation in the first-dimension column (containing beta-cyclodextrin as the chiral selector) of a comprehensive two-dimensional gas chromatography (GC x GC) system, whereas a polar polyethylene glycol capillary column was used for separation in the second dimension. Naturally occurring ephedrine-type alkaloids and their synthetic analogues (enantiomeric counterparts) were adequately resolved from each other, as well as from potential interference species in the sample matrix using GC x GC, whereas single column GC analysis was unable to separate all the alkaloids of interest. Detection limits in the order of 0.

Cholic-acid-based fluorescent sensor for dicarboxylates and acidic amino acids in aqueous solutions.

[structure: see text] The binding affinities of a cholic-acid-based fluorescent neutral receptor toward dicarboxylate anions and amino acids have been investigated in a CH3OH/H2O system (1:1, 0.01 M HEPES buffer, pH = 7.4) by fluorescence titration experiments.

Fluorescent anion sensor derived from cholic acid: the use of flexible side chain.

[structure: see text] The fluorescent photoinduced electron transfer (PET) chemosensors 1-3 were synthesized from cholic acid. 1 and 2 containing amidothiourea groups as anion receptive sites demonstrated much higher affinity toward anions than 3 containing traditional thiourea H-bond donating group. Comparative studies on their binding affinity toward carboxylates, dihydrogen phosphate, and halides revealed that the amidothiourea moiety on the C17 side chain could work cooperatively with H-bond donating groups on C7 and C12 to bind spherical halogen anions.

Separation of enantiomers in microemulsion electrokinetic chromatography using chiral alcohols as cosurfactants.

A novel chiral microemulsion, which involved the use of chiral alcohols as cosurfactants, was demonstrated for the enantiomeric separation of a number of pharmaceutical drugs in microemulsion electrokinetic chromatography (MEEKC). The chiral alcohols investigated were optically active 2-alkanols, with the alkyl chain length having carbon number ranging from 4 to 7. The data indicated that, except for R-(-)-2-butanol, the use of R-(-)-2-pentanol, R-(-)-2-hexanol or R-(-)-2-heptanol as the chiral cosurfactant resulted in the baseline or partial resolution of most of the test solutes, i.

A ratiometric fluorescent sensor for Ag(I) with high selectivity and sensitivity.

A bicyclic cycloadduct 1 bearing a pyrenyl moiety has been synthesized and investigated as a ratiometric fluorescent sensor for AgI. In an aqueous ethanol solution of 1, the presence of silver ion induces the formation of a 1:2 metal-ligand complex, which exhibits a strong intensity enhancement of the pyrene excimer emission at the expense of the emission of monomeric pyrene.