Synthesis and comparison of the structure–property relationships of symmetric and asymmetric water‐soluble poly(p‐phenylene)s

Sodium salts of water‐soluble polymers poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(hexyloxy)‐1,4‐phenylene]} ( P1 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dodecyloxy)‐1,4‐phenylene]} ( P2 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dibenzyloxy)‐1,4‐phenylene]} ( P3 ), poly[2‐hexyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P4 ), and poly[2‐dodecyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P5 )] were synthesized with Suzuki coupling reactions and fully characterized. The first group of polymers ( P1 – P3 ) with symmetric structures gave lower absorption maxima [maximum absorption wavelength (λ_max) = 296–305 nm] and emission maxima [maximum emission wavelength (λ_em) = 361–398 nm] than asymmetric polymers P4 (λ_max = 329 nm, λ_em = 399 nm) and P5 (λ_max = 335 nm, λ_em = 401 nm). The aggregation properties of polymers P1 – P5 in different solvent mixtures were investigated, and their influence on the optical properties was examined in detail. Dynamic light scattering studies of the aggregation behavior of polymer P1 in solvents indicated the presence of aggregated species of various sizes ranging from 80 to 800 nm. The presence of alkoxy groups and 3‐sulfonatopropoxy groups on adjacent phenylene rings along the polymer backbone of the first set hindered the optimization of nonpolar interactions. The alkyl chain crystallization on one side of the polymer chain and the polar interactions on the other side allowed the polymers ( P4 and P5 ) to form a lamellar structure in the polymer lattice. Significant quenching of the polymer fluorescence upon the addition of positively charged viologen derivatives or cytochrome‐C was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers could be used in the fabrication of biological and chemical sensors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3763–3777, 2006     

Zinc salt assisted solvolyses of tertiary alkyl halides

Tertiary alkyl halides undergo facile substitution reactions under solvolytic conditions in presence of zinc ions yielding alcohols, ethers and esters.     

A strategy for extending the applicability of a validated plasma calibration curve to quantitative measurements in multiple tissue homogenate samples: a case study from a rat tissue distribution study of JI-101, a triple kinase inhibitor

A general practice in bioanalysis is that, whatever the biological matrix the analyte is being quantified in, the validation is performed in the same matrix as per regulatory guidelines. In this paper, we are presenting the applicability of a validated LC‐MS/MS method in rat plasma for JI‐101, to estimate the concentrations of JI‐101 in various tissues that were harvested in a rat tissue distribution study. A simple protein precipitation technique was used to extract JI‐101 and internal standard from the tissue homogenates. The recovery of JI‐101 in all the matrices was found to be >70%. Chromatographic separation was achieved using a binary gradient using mobile phase A (acetonitrile) and B (0.2% formic acid in water) at a flow rate of 0.30 mL/min on a Prodigy ODS column with a total run time of 4.0 min. The MS/MS ion transitions monitored were 466.1 → 265 for JI‐101 and 180.1 → 110.1 for internal standard. The linearity range was 5.02–4017 ng/mL. The JI‐101 levels were quantifiable in the various tissue samples harvested in this study. Therefore, the use of a previously validated JI‐101 assay in plasma circumvented the tedious process of method development/validation in various tissue matrices. Copyright © 2011 John Wiley & Sons, Ltd.     

BUBBLE BEHAVIOR AND HEAT TRANSFER MECHANISM IN FC-72 POOL BOILING

A transparent heater made of a thin synthetic diamond substrate along with a high-speed camera was used to investigate bubble behavior during pool boiling. The heater design, combined with the selected FC-72 liquid, overcame the difficulty of previous thin-film heater experiments where transparency and adequate heat flux could not be simultaneously achieved. It also resulted in an essentially uniform temperature field over the heater surface. The growth and merging of bubbles were visualized and quantitatively documented. The relative contribution from phase change to the overall heat flux was determined at several heat flux levels. At a heat flux level half of the critical heat flux (CHF), surface bubble nucleation was found to contribute to more than 70% of the heat transfer from the heater surface. At a similar heat flux level, the ratio of dry to wetted area was determined to exceed 1/3, significantly higher than that predicted by a recent hydrodynamic model for CHF (approximately 1/16). This result suggests that modifications are needed for the hydrodynamic model when applied to highly wetting fluid on nearly isothermal surfaces. The merging of bubbles to form vapor blankets over the heater surface was observed, as has been assumed in recent hydrodynamic models.     

Surface plasmon resonance-based immunosensor with oriented immobilized antibody fragments on a mixed self-assembled monolayer for the determination of staphylococcal enterotoxin B

An immunosensor based on surface plasmon resonance (SPR) with a mixed self-assembled monolayer (SAM) was developed to determine staphylococcal enterotoxin B (SEB). The SAM on a gold surface was fabricated by adsorbing a mixture of 16-mercapto-1-hexadecanoic acid (16-MHA) and hexanethiol at various molar ratios. Initially, full-length anti-SEB was randomly immobilized onto the SAM to form the immunosensing surface. Through optimization of surface functionalization and anti-SEB immobilization, the SPR sensors can be applied to the determination of SEB in a linear range of 0.01?~?1.0 μg.mL^?1. Furthermore, a smaller antibody fragment (F(ab)’) was generated and immobilized randomly (via amino groups) or in an oriented manner (via ?SH groups) to form the immunosensing surface. The oriented immobilization of F(ab)’ led to a 50% increase in the antigen binding efficiency compared to randomly immobilized covalent F(ab’) fragments. The resulting calibration curve showed higher sensitivity. In addition, the specificity and applicability of the proposed immunosensor to milk samples were also demonstrated. Furthermore, the sensor can be regenerated using 0.1 M HCl, and 70% of the initial response was maintained over 3 cycles.     

Synthesis of 62-electron square planar clusters with group 15 and 16 main group atoms: Structural characterization of Ru4(CO)11(μ4-PPh)(μ4-S) and Ru4(CO)10(μ4-PPh)(μ4-Se)(PEt3): Bonding preferences in cappingNido Ru4(CO)13(μ3-PPh)

Thecloso octahedral cluster Ru₄(CO)₁₁(μ₄-PPh)(μ₄-S)1 and selenium and tellurium analogues, the first examples of unsaturated ruthenium clusters with a planar metal core and different main group 15 and 16 atoms have been synthesized fromnido Ru₄(CO)₁₃(μ₃-PPh). An X-ray analysis of1 and Ru₄(CO)₁₀(μ₄-PPh)(μ₄-Se)(PEt₃)2a has confirmed thetrans disposition of phosphorus and group 16 main group fragments.     

Crystal and molecular structure of isogarcinol

The controversy with regard to the structures of the closely related polyisoprenylated phenolic compounds, garcinol, isogarcinol, camboginol, cambogin, xanthochymol and isoxanthochymol is cleared by X-ray crystallographic analysis of the naturally occurring isogarcinol. The unusual UV spectral characteristics of the chromophore of isogarcinol are discussed.     

Arylnaphthalide lignans from Cleistanthus collinus

Chemical examination of the aerial parts of Cleistanthus collinus afforded the arylanphthalide lignans, cleistanone (1), diphyllin (2), cleistanthins A (3), C (4) and D (5), and 4-O-(3"-O-methyl-beta-D-glucopyranosyl)-diphyllin (6). The first compound is a new member of the rare group of arylnaphthalide lignans containing an alkoxy group on the lactone ring. The structure of the compound was determined from its spectral data, chemical transformations and partial synthesis from diphyllin (2). The new lignan, 1 and its acetyl derivative, 7 were found to exhibit cytotoxicity against MT(2) cell lines.     

Volumetric determination of tetraalkyl thiuram disulphides

Summary A method for the volumetric determination of tetraalkyl thiuram disulphide is developed. It is based on its reaction with potassium cyanide in aqueous acetonitrile medium, when the corresponding tetraalkyl thiuram monosulphide and thiocyanate are formed. The former is removed by extraction with benzene and the latter converted into cyanogen bromide, which is estimated iodometrically.

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Zusammenfassung Ein Verfahren zur volumetrischen Bestimmung von Tetraalkyl-thiuramdisulfid wird beschrieben. Es beruht auf der Reaktion mit Kaliumcyanid in wäßriger Acetonitrillösung, wobei das entsprechende Tetraalkyl-thiurammonosulfid und Thiocyanat gebildet werden. Ersteres wird durch Extraktion mit Benzol entfernt; das Thiocyanat wird in Bromcyan umgewandelt, das dann jodometrisch bestimmt wird.