A silicone-based stretchable micropost array membrane for monitoring live-cell subcellular cytoskeletal response

External forces are increasingly recognized as major regulators of cellular structure and function, yet the underlying mechanism by which cells sense forces and transduce them into intracellular biochemical signals and behavioral responses ('mechanotransduction') is largely undetermined. To aid in the mechanistic study of mechanotransduction, herein we devised a cell stretching device that allowed for quantitative control and real-time measurement of mechanical stimuli and cellular biomechanical responses. Our strategy involved a microfabricated array of silicone elastomeric microposts integrated onto a stretchable elastomeric membrane. Using a computer-controlled vacuum, this micropost array membrane (mPAM) was activated to apply equibiaxial cell stretching forces to adherent cells attached to the microposts. Using the mPAM, we studied the live-cell subcellular dynamic responses of contractile forces in vascular smooth muscle cells (VSMCs) to a sustained static equibiaxial cell stretch. Our data showed that in response to a sustained cell stretch, VSMCs regulated their cytoskeletal (CSK) contractility in a biphasic manner: they first acutely enhanced their contraction to resist rapid cell deformation ('stiffening') before they allowed slow adaptive inelastic CSK reorganization to release their contractility ('softening'). The contractile response across entire single VSMCs was spatially inhomogeneous and force-dependent. Our mPAM device and live-cell subcellular contractile measurements will help elucidate the mechanotransductive system in VSMCs and thus contribute to our understanding of pressure-induced vascular disease processes.     

An efficient approach to new dihydroxyquinolizidines

Using d-glyceraldehyde acetonide as a starting material, a four-step synthesis of enantiomerically pure 3,4-dihydroxyquinolizidines is described. The key steps of the synthesis consist of a Mitsunobu ring-closing reaction and the subsequent reduction of a pyridinium ring.     

Selective magnesiation of chloro-iodopurines: an efficient approach to new purine derivatives

[reaction: see text] Both 6-chloro-2-iodo-9-isopropylpurine (1) and 2-chloro-6-iodo-9-benzylpurine (4) undergo a selective I/Mg exchange reaction with iPrMgCl at -80 degrees C. The reaction course at 0 degrees C is different. Magnesiation of 1 proceeds with the migration of magnesium to the 8 position of the purine nuclei. In the case of 4, substitution of iodine with an alkyl group from the Grignard reagent accompanied with a Cl/Mg exchange reaction takes place, and 6-alkyl-2-magnesiated purines (9) are formed. Thus prepared Grignard reagents afford the corresponding alcohols by the reaction with aldehydes.     

A new approach to the design of surface treatments for reinforcing agents

A new approach for design of improved interfacial bonding between carbon fibers and polymeric matrices is described. In this method the affinity of surface-treated carbon fibers to various polymer matrices is simulated by analyzing the adsorption characteristics of model compounds, typical of the polymer units, onto very high surface area carbon fibers. The affinity can be evaluated by the use of Thermogravimetric Analysis (TGA) to measure adsorption–desorption characteristics. Since high surface area, activated carbon fibers (ACF) can be chemically treated to obtain acidic, basic, nonpolar or highly polar surfaces, it should be possible to assess the interactions of chemically modified surfaces with model compounds such as methanol (MeOH), acetone, dimethylformamide (DMF), dimethylether, tetrahydrofuran (THF) and water. Some preliminary results are presented, indicating that surface treatments for carbon fibers other than oxidation may lead to enhanced bonding with polymeric matrices.     

A new approach to the efficient indole synthesis by allene intramolecular cycloaddition

A new development of efficient indole synthesis via allene intramolecular cycloaddition strategy is described.     

An efficient organometallic approach to new carbocyclic nucleoside analogues

[reaction: see text] A general synthetic approach to monoprotected carbocyclic nucleoside analogues, having the nucleobase attached to a 3-hydroxymethyl-4-trialkylsilyloxymethyl-cyclopent-2-en-1-yl scaffold, was developed. A (racemic) key intermediate was prepared by a cobalt-mediated Pauson-Khand reaction. In the course of the further synthesis, the introduction of the nucleobase was achieved with complete regio- and diastereoselectivity through a palladium-catalyzed allylic substitution.     

A new approach to mineralization of biocompatible hydrogel scaffolds: an efficient process toward 3-dimensional bonelike composites

As a first step toward the design and fabrication of biomimetic bonelike composite materials, we have developed a template-driven nucleation and mineral growth process for the high-affinity integration of hydroxyapatite with a poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel scaffold. A mineralization technique was developed that exposes carboxylate groups on the surface of cross-linked pHEMA, promoting high-affinity nucleation and growth of calcium phosphate on the surface, along with extensive calcification of the hydrogel interior. Robust surface mineral layers a few microns thick were obtained. The same mineralization technique, when applied to a hydrogel that is less prone to surface hydrolysis, led to distinctly different mineralization patterns, in terms of both the extent of mineralization and the crystallinity of the apatite grown on the hydrogel surface. This template-driven mineralization technique provides an efficient approach toward bonelike composites with high mineral-hydrogel interfacial adhesion strength.     

A new approach for efficient simulation of Coulomb interactions in ionic fluids

We propose a simplified version of local molecular field (LMF) theory to treat Coulomb interactions in simulations of ionic fluids. LMF theory relies on splitting the Coulomb potential into a short-ranged part that combines with other short-ranged core interactions and is simulated explicitly. The averaged effects of the remaining long-ranged part are taken into account through a self-consistently determined effective external field. The theory contains an adjustable length parameter sigma that specifies the cutoff distance for the short-ranged interaction. This can be chosen to minimize the errors resulting from the mean-field treatment of the complementary long-ranged part. Here we suggest that in many cases an accurate approximation to the effective field can be obtained directly from the equilibrium charge density given by the Debye theory of screening, thus eliminating the need for a self-consistent treatment. In the limit sigma-->0, this assumption reduces to the classical Debye approximation. We examine the numerical performance of this approximation for a simple model of a symmetric ionic mixture. Our results for thermodynamic and structural properties of uniform ionic mixtures agree well with similar results of Ewald simulations of the full ionic system. In addition, we have used the simplified theory in a grand-canonical simulation of a nonuniform ionic mixture where an ion has been fixed at the origin. Simulations using short-ranged truncations of the Coulomb interactions alone do not satisfy the exact condition of complete screening of the fixed ion, but this condition is recovered when the effective field is taken into account. We argue that this simplified approach can also be used in the simulations of more complex nonuniform systems.     

A microwave enhanced cross-metathesis approach to peptidomimetics

Functionalization of amino acid C- and N-termini with appropriate olefinic moieties allows for the generation of a peptidomimetic via a stereoselective cross-metathesis.     

A simple electrical approach to monitor dielectrophoretic focusing of particles flowing in a microchannel

This paper reports an impedance‐based system for the quantitative assessment of dielectrophoretic (DEP) focusing of single particles flowing in a microchannel. Particle lateral positions are detected in two electrical sensing zones placed before and after a DEP‐focusing region, respectively. In each sensing zone, particle lateral positions are estimated using the unbalance between the opposite pulses of a differential current signal obtained with a straightforward coplanar electrode configuration. The system is used to monitor the focusing of polystyrene beads of 7 or 10 μm diameter, under various conditions of DEP field intensities and flow rates that produce different degrees of focusing. This electrical approach represents a simple and valuable alternative to optical methods for monitoring of particle focusing systems.     

一种将三价钛引入锐钛型二氧化钛的新方法:用于有效的光催化产氢（英文）

伴随着科技的日益进步,人们的生活水平有了极大的提升,但是随之而来的环境污染问题也成为当前世界亟待解决的重大问题之一.太阳能是地球上最大的清洁能源来源,有效地利用太阳能将为解决环境污染问题提供巨大的帮助.而光催化技术的一个关键材料就是催化剂,催化剂对太阳能利用的好坏也就决定了光催化技术的应用前景.因此,人们对催化剂的研究也在逐步深入.1972年,Fuiishima和Honda在Nature杂志上首次报道了二氧化钛电极在紫外光照射下分解水产生氢气的现象,自此掀起了半导体光催化的研究热潮.二氧化钛因具有无毒、廉价和耐腐蚀等优点而在光催化领域广受关注.传统白色二氧化钛具有两大劣势(宽的禁带宽度与高的电子/空穴复合率)大大限制了它的应用.人们对于改变二氧化钛性质进行了大量的尝试,例如金属/非金属掺杂、形貌的改变等.黑色二氧化钛(存在大量的氧空位和三价钛)的出现极大地克服了传统白色二氧化钛的缺点,其具有窄的禁带宽度和低的电子/空穴复合速度.目前,黑色二氧化钛的制备方法大致分为以下几种:(1)高压下氢化;(2)高温常压下氢化;(3)铝热还原法;(4)溶液蒸发法;(5)化学氧化法;(6)电化学还原等.由于更简单安全(不涉及氢气使用)和更好的可见光光催化活性,三价钛自掺杂的二氧化钛从这些方法中脱颖而出.迄今为止,诱导三价钛的方法通常是能量密集型的,涉及不稳定的Ti原料(如TiO和TiH_2).研究用于制备三价钛自掺杂二氧化钛的新方法是十分必要的.我们以稳定的钛粉为原料,通过简单的方法将三价钛和氧空位成功地引入锐钛型二氧化钛.通过X射线衍射、场致发射扫描电子显微镜等技术研究了制备样品的物理化学性质,发现H_2O_2和水热反应时间对纳米棒型微观形貌的形成至关重要.通过调整诸如H_2O_2量和水热反应时间的参数,根据实验结果提出了形成这种微观结构的可能机制.更重要的是,可见光区域的光吸收受到样品中氧空位量的控制,存在氧空位的最佳值使光催化产氢活性最高.     

A new efficient synthesis of substituted nazarov reagents. A wittig-horner-emmons approach

A highly stereoselective synthesis of terminally substituted ethyl 3-oxo-4-pentenoates $\text{3}$ from γ-phosphorylated ethyl acetoacetate $\text{2}$ and diverse carbonyl compounds was accomplished.     

Combinatorial decoding: an approach for universal DNA array fabrication

A fiber optic microsphere-based oligonucleotide array is described that employs the sequence of the oligonucleotide probe attached to each microsphere as positional identifiers. Each microsphere serves as an immobilized array feature, functionalized with a unique single-stranded oligonucleotide sequence and randomly distributed into an array of microwells. To determine the sequences attached to individual microspheres, a series of fluorescently labeled combinatorial-pooled oligonucleotide target solutions was designed. Each combinatorial decoding solution is intended to identify the nucleotide at a particular position on every microsphere in the array. The combinatorial target solutions were synthesized by linking the four possible nucleotides at each position to four different fluorescent reporter dyes. As such, when the solutions were hybridized to the array, one of four possible fluorescent responses was generated for each position on a microsphere probe sequence. Adjusting the stringency of hybridization enabled single-base mismatch discrimination, and the signal with the highest intensity corresponded to the perfect nucleotide match. By consecutively exposing the array to a series of combinatorial decoding pool solutions, it was possible to simultaneously determine the sequence of every randomly positioned oligonucleotide-functionalized microsphere in the array. Once mapped, the microsphere array can be used for any typical genomic microarray experiment.     

A single-step approach to create nano-pottery structures for efficient water electrocatalysis

We have introduced a simple fabrication process to create Ni nano-pottery structure using a well-controlled electrodeposition process into a nanoporous alumina template. The nanostructures were then applied as a stable and effective cathode catalyst for hydrogen evolution reaction (HER) in alkaline water electrolysis. Their catalytic activity was compared to that of the Ni nano-rod and film and the result shows that the HER activity was greatly enhanced when using the Ni nano-pottery structure which mainly resulted from both larger and higher numbers of surface reactive sites.     

Supramolecular chemistry approach to the design of a high-resolution sensor array for multianion detection in water

Reliable sensing of structurally similar anions in water is a difficult problem, and analytical tests and sensor devices for reliable sensing of multiple anions are very rare. This study describes a method for fabrication of simple colorimetric array-based assays for aqueous anion solutions, including complex analytes encountered in real-life applications. On the fundamental level, this method shows how the discriminatory capacity of sensor arrays utilizing pattern recognition operating in multianalyte environments may be dramatically improved by employing two key features. The synergy between the sensor and hydrogel host resembles the cooperative effects of an apoenzyme and cofactor: the host hydrogel helps extract the target anions from the bulk analyte while stripping the solvate molecules off the anions. In addition, the supramolecular studies of the affinity and selectivity of the potential sensors for target analytes allow for constructing an array predesigned for a particular analyte. To illustrate both aspects, an eight-sensor array utilizing colorimetric sensor materials showing selectivity for fluoride and pyrophosphate while displaying significant cross-reactivity for other anions such as carboxylates, phosphate, or chloride was used to differentiate between 10 anions. The quantitative analyses were also performed to show that the eight-sensor array was found to operate across 4 orders of magnitude concentrations (0.20-360 ppm; 10 microM to 20 mM). The applicability of this approach was demonstrated by analyzing several toothpaste brands. The toothpastes are complex analytes comprising both known and unknown anions in various concentrations. The fluoride-selective yet cross-reactive array is shown to utilize the fluoride content as the main differentiating factor while using the remaining anionic components for further differentiation between toothpaste brands.     

A new efficient route to 3-vinylthiophene

The synthesis of 3-vinylthiophene was efficiently achieved in two steps. 3-(2-bromoethyl)thiophene prepared from 3-(2-ethanol)thiophene was converted to the title compound (70% overall yield) using tetraglyme as a solvent and 1,8-diazabicyclo[5.4.0]undec-7-ene as a base.     

A mechanistically guided design leads to the synthesis of an efficient and practical new reagent for the highly enantioselective,catalytic dihydroxylation of olefins

[structure: see text] The catalytic asymmetric dihydroxylation of olefins has been accomplished with high enantioselectivities using a proline-based catalyst. The pre-transition-state assembly for styrene is shown.