A hyperbranched,rotaxane‐type mechanically interlocked polymer

Based on the dibenzo‐24‐crown‐8/1,2‐bis(pyridinium)ethane recognition motif, a hyperbranched mechanically interlocked polymer was prepared by polyesterification of an easily available dynamic trifunctional AB₂ pseudorotaxane monomer. It was characterized by various techniques including ¹H NMR, COSY, NOESY, GPC, viscosity, TGA, dynamic laser light scattering, AFM, and SEM. Its GPC M_n was determined to be 191 kDa with polydispersity 1.7 and its hydrodynamic diameter in a dilute solution in acetone was about 70 nm. This measured M_n value corresponds to about 93 repeating units. The study reported here presents not only a new polymer topology but also a novel and convenient way to prepare mechanically interlocked polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4067–4073, 2010     

Thermal and pH‐sensitive gold nanoparticles from H‐shaped block copolymers of (PNIPAM/PDMAEMA)‐b‐PEG‐b‐(PNIPAM/PDMAEMA)

Well‐defined H‐shaped pentablock copolymers composed of poly(N‐isopropylacrylamide) (PNIPAM), poly(N,N‐dimethylaminoethylacrylamide) (PDMAEMA), and poly(ethylene glycol) (PEG) with the chain architecture of (A/B)‐b‐C‐b‐(A/B) were synthesized by the combination of single‐electron‐transfer living radical polymerization, atom‐transfer radical polymerization, and click chemistry. Single‐electron‐transfer living radical polymerization of NIPAM using α,ω azide‐capped PEG macroinitiator resulted in PNIPAM‐b‐PEG‐b‐PNIPAM with azide groups at the block joints. Atom‐transfer radical polymerization of DMAEMA initiated by propargyl 2‐chloropropionate gave out α‐capped alkyne‐PDMAEMA. The H‐shaped copolymers were finally obtained by the click reaction between PNIPAM‐b‐PEG‐b‐PNIPAM and alkyne‐PDMAEMA. These copolymers were used to prepare stable colloidal gold nanoparticles (GNPs) in aqueous solution without any external reducing agent. The formation of GNPs was affected by the length of PDMAEMA block, the feed ratio of the copolymer to HAuCl₄, and the pH value. The surface plasmon absorbance of these obtained GNPs also exhibited pH and thermal dependence because of the existence of PNIAPM and PDAMEMA blocks. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Theoretical prediction on HBeN− and HNBe− anions using multiconfiguration second‐order perturbation theory

The HBeN^? and HNBe^? anions have been investigated for the first time using the CASSCF, CASPT2, and DFT/B3LYP methods with the contracted atomic natural orbital (ANO) and cc‐pVTZ basis sets. The geometries of all stationary points along the potential energy surfaces were optimized at the CASSCF/ANO and B3LYP/cc‐pVTZ levels. The ground and the first excited states of HBeN^? are predicted to be X²Π and A²Σ⁺ states, respectively. It was predicted that the ground state of HNBe^? is X²Σ⁺ state. The A²Π state of HNBe^? has unique imaginary frequency. A bend local minimum M1 was found along the 1²A″ potential energy surface and the A²Π state of HNBe^? should be the transition state of the isomerization reactions for M1 ? M1. The CASPT2/ANO potential energy curves of isomerization reactions were calculated as a function of HBeN bond angle. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Optically active composite nanoparticles with chemical bonds between core and shell

A facile methodology was developed to prepare a novel type of core/shell nanoparticles (NPs) with optical activity and with chemical bonds between the cores and shells. The cores were prepared via catalytic emulsion copolymerization of substituted acetylene comonomers in which one monomer contains azo groups in side chains. For preparing the core/shell NPs, the azo groups in the seed particles (i.e., cores) subsequently act as initiators for vinyl monomer to undergo free radical polymerizations, yielding the shells. This situation resulted in chemical bonds between cores and shells. Both the seed emulsion and core/shell nanoparticle emulsion exhibited optical activity, derived from the polyacetylenes adopting helical conformation of predominant handedness. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Three New Sesquiterpenoids from Echinops ritro L.

From the whole plants of E. ritro L., the three new sesquiterpenoids (3α,4α,6α)‐3,13‐dihydroxyguaia‐7(11),10(14)‐dieno‐12,6‐lactone ( 1 ), (3α,4α,6α,11β)‐3‐hydroxyguai‐1(10)‐eno‐12,6‐lactone ( 2 ), and (11α)‐11,13‐dihydroarglanilic acid methyl ester (=(4β,6α,11α)‐4,6‐dihydroxy‐1‐oxoeudesm‐2‐en‐12‐oic acid methyl ester; 3 ), together with eight known sesquiterpenoids, were isolated. Their structures were elucidated through analysis of spectroscopic data including extensive 2D‐NMR.     

An efficient synthesis of α-methylene-γ-butyrolactones from Baylis-Hillman adducts via an In-mediated Barbier reaction and stereoselective lactonization under MeSO2Cl/Et3N conditions

An efficient synthesis of trans-α-methylene-γ-butyrolactones is disclosed from syn-homoallylic alcohols via the intramolecular mesylate displacement reaction promoted by nearby ester group under the influence of MsCl/Et₃N. syn-Homoallylic alcohols were prepared via the In-mediated Barbier reaction of the bromides of Baylis-Hillman adducts.     

An automated capillary electrophoresis system for high-speed separation of DNA fragments based on a short capillary

A high-speed DNA fragment separation system was developed based on a short capillary and a slotted-vial array automated sample introduction system. The injection process of DNA sample in a short capillary was investigated systematically with three injection techniques including constant-field-strength, low-field-strength and translational spontaneous injections. Under the optimized conditions, picoliter-scale sample plugs (corresponding to ca. 20-μm plug length) were obtained, which ensure the high-speed and high-efficiency separation for DNA fragments with a short effective separation length. Other separation conditions including the sieving matrix concentration, separation field strength and effective separation length were also optimized. The present system was applied in the separation of ΦX174-Hae III digest DNA marker. With an effective separation length of 2.5 cm, the separation could be achieved in <100 s with plate heights ranging from 0.21 to 0.74 μm (corresponding to plate numbers from 4.86 × 10(6) to 1.36 × 10(6)/m). The repeatabilities for the migration time of the eleven fragments were between 0.4 and 1.1% RSD (n=8). By using the automated continuous injection method, the separation for four different DNA samples could be achieved within 250 s. The present system was further applied in the fast sizing of real DNA samples of PCR products.     

Facile assembly of size- and shape-tunable IV-VI nanocrystals into superlattices

In comparison to the previous lengthy approaches, we described a general and simple strategy for engineering the superlattice assembly of IV-VI semiconductor nanocrystals (NCs) with tunable sizes and morphologies. Not only the well-studied spherical NCs but also some special-shaped NCs, such as the quasi-cubic, cubic, truncated octahedral, and octahedral, could self-assemble into well-ordered patterns, as demonstrated in PbS, PbSe, and PbTe. These results extended our proposed model about the configuration of ligand chains in the superlattice assembly. This powerful capability of assembling superlattices was dominated by a heat-treatment process, providing a significant and extensive direction in the engineering of morphology-tunable NC superlattices.     

Telomere and Telomerase as Targets for Cancer Therapy

Telomere maintenance and telomerase reactivation is essential for the transformation of most human cancer cells. Telomere shortening to the threshold length, mutations of the telomere-associated proteins, and/or telomerase RNA lead to telomeric dysfunction and therefore genomic instability. Telomerase up-regulation in 85% of human cancer cells has become a hallmark of cancers, hence a promising target for anticancer therapy. In this review, we discuss the mechanism of cancer due to telomere dysfunction and the resulting biological effects, the control of telomerase activity, and the new developments in cancer therapies targeting telomere and telomerase.