De Novo Synthesis of 2,2'-Bipyridines and Related Bis-azines via Cascade Coupling and Double Pyridannulation of Isocyanides.

Herein, we present a new and general protocol for the assembly of 2,2'-bipyridyls from nonpyridine substrates without using any metal catalysts or organometallic reagents. The process starts from the coupling of two 1,3-dienyl isocyanides followed by a 6π-electrocyclization/aromatization cascade featuring the simultaneous formation of two pyridine rings in a single operation. Notably, this strategy is also applicable to the construction of nonsymmetrical 2-(2-pyridyl)-quinolines/-quinoxalines. Furthermore, the aggregation-induced emission (AIE) characteristics endow our approach with great potential in biorelevant fields.

Isocyanide Heterodimerization-Triggered Three-Component Reaction: Diversity-Oriented Synthesis of Quinoxalines.

Known isocyanide-based multicomponent reactions (IMCRs) are usually triggered by addition of the isocyano group to the strong electrophilic component. We herein report a new isocyanide-based three-component reaction, in which an unprecedented quinoxaline-based zwitterionic intermediate is generated from the chemoselective heterodimerization of weak electrophilic ortho-diisocyanoarenes and common isocyanides. This reactive zwitterion could react in situ with various trapping agents to furnish a range of structurally diverse quinoxalines.

A novel fluorescence sensor for uranyl ion detection based on a dansyl-modified peptide.

It is of great significance to sensitively and selectively detect uranyl ion (UO22+) in environmental and biological samples due to the high risks of UO22+ to human health. However, such suitable sensors are still scarce. A novel fluorescence sensor based on a dansyl-modified peptide, Dansyl-Glu-Glu-Pro-Glu-Trp-COOH (D-P5), was efficiently synthesized by Fmoc solid phase peptide synthesis. As the first linear peptide-based fluorescence sensor for UO22+, D-P5 exhibited high selectivity and sensitivity to UO22+ over 27 metal ions (UO22+, Cr3+, Cu2+, Ba2+, Hg2+, Pb2+, Co2+, Ag+, Fe3+, Ca2+, K+, Mg2+, Mn2+, Na+, Ni2+, Cd2+, Zn2+, Al3+, Dy3+, Er3+, Gd2+, Ho3+, La3+, Lu3+, Pr3+, Sm3+, Tm3+) by a turn-off fluorescence response in 10 mM HEPES buffer (pH 6.3). The effects of anions such as S2-, NO3-, SO42- CO32-, HCOO-, antioxidant ascorbic acid and 4-nitrophenyl acetate on the selectivity for UO22+ detection were also studies. D-P5 sensor could be used for detecting UO22+ in a good linear relationship with concentration in the range of 0-8.0 µM with a low limit of detection of 83.2 nM. Furthermore, the interaction of the sensor with UO22+ was characterized by ESI-MS, IR, XPS and ITC measurements. The 1:1 binding stoichiometry between the sensor and UO22+ was measured by the job's plot and further verified by ESI-MS. The binding constant of the sensor with UO22+ was calculated to be 9.8 × 104 M-1 by modified Benesi-Hildebrand equation. ITC results showed that theΔHθ andΔSθ for the interaction of D-P5 with UO22+ were -(7.167 ± 1.25) kJ·mol-1 and 66.5 J·mol-1·K-1, respectively. Time-resolved fluorescence spectroscopy indicated that the mechanism of fluorescence quenching of D-P5 by UO22+ ion was static quenching process. In addition, this sensor displayed a good practicality for UO22+ detection in lake water sample without tedious sample pretreatment.

Sensitive electrochemiluminescence analysis of lung cancer marker miRNA-21 based on RAFT signal amplification.

An electrochemiluminescence approach based on surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) was developed for miRNA-21 detection for the first time. The SI-RAFT polymerization generates polymer chains with functional groups that are used to recruit luminol, enabling strong ECL signal output with low concentrations of miRNA-21, and greatly improving the detection sensitivity.

Analysis of capillary interferometry for measuring refractive indices of minute samples.

A method of measuring the refractive indices of minute samples by analyzing capillary interferometry is introduced. With the interference theory of light, the intensity distribution of an interference fringe pattern formed by a cylindrical tube of a capillary is obtained, and the influence of some parameters on the fringes are discussed. The measurement accuracy and its relative problems are analyzed.

[Measurements of diffusion reflectance and transmittance of biological tissues by using CCD].

The CCD experimental setup and the CCD image analysis system that were developed by using C Language were presented, and the spatially resolved diffusion reflectance and transmittance of porcine muscle and fat were determined by using CCD experimental setup. The experimental results were compared with those of Monte Carlo simulations and those of the two models based on diffusion theory, and we found good agreement between theory and experiment for the range from the beam center to 12 mm. It i s shown that the CCD experimental setup and the CCD image analysis system can be used to measure the spatially resolved diffusion reflectance and transmittance of biological tissues, and this work offers the experimental bases for noninvasive and fast measurement of optical parameters of biological tissues.

Measurement and analysis of light distribution in intralipid-10% at 650 nm.

A method for measuring the distributions of light in the biological tissue phantom Intralipid by use of an optical fiber is presented and measurements of distributions of light in Intralipid-10% suspensions at 650 nm are described. This approach is complementary to that in which an optical fiber with an isotropic tip detects the distribution of light in tissue phantoms. The characteristics of the distance-dependent intensity of scattering light in different directions were revealed by the experimental results; the effects of the optical parameters and of the radius of the incident beam on the distributions of light in tissue phantoms were given; and the experimental results were analyzed by the diffusion theory. These studies will help in further understanding of the scattering characteristics of tissue.

Simultaneous refractive index and thickness measurements of bio tissue by optical coherence tomography.

This paper presents two techniques based on optical coherence tomography, the "focus tracking method" and the "optical path shifting method," for determining refractive index and thickness simultaneously, which are especially useful for bio tissues. From comparison of these two methods, it was found that the focus tracking method is suitable for in vivo measurement, but does not have high precision. The optical path shifting method is limited to in vitro measurement, but has high precision. Using the optical path shifting method, the refractive indices of cucumber were measured at the wavelength of 850 and 1300 nm.