Amphiphilic conetworks. II. Novel two‐step synthesis of poly[2‐(dimethylamino)ethyl methacrylate]–polyisobutylene,poly(N‐isopropylacrylamide)–polyisobutylene,and poly(N,N‐dimethylacrylamide)–polyisobutylene hydrogels

Amphiphilic polymer conetworks consisting of hydrophilic poly[2‐(dimethylamino)ethyl methacrylate], poly(N‐isopropylacrylamide), or poly(N,N‐dimethylacrylamide) and hydrophobic polyisobutylene chains were synthesized with a novel two‐step procedure. In the first step, a methacrylate‐multifunctional polyisobutylene crosslinker was prepared by the cationic copolymerization of isobutylene with 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate. In the second step, the methacrylate‐multifunctional polyisobutylene crosslinker, with a number‐average molecular weight of 8200 and an average functionality of approximately 4 per chain, was copolymerized radically with 2‐(dimethylamino)ethyl methacrylate, N‐isopropylacrylamide, or N,N‐dimethylacrylamide into transparent amphiphilic conetworks containing 42–47 mol % hydrophilic monomer. The synthesized conetworks were characterized with solid‐state ¹³C NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proved by swelling in both water and n‐heptane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6378–6384, 2006     

Nutrient Removal Efficiency and Physiological Responses of Desmodesmus communis at Different HRTs and Nutrient Stress Condition Using Different Sources of Urban Wastewater Effluents

The objective of the present study was to evaluate the nutrient removal efficiency and the physiological responses in terms of growth, biochemical composition and photosynthetic activity of the autochthonous freshwater algal strain Desmodesmus communis. Microalgae were grown in a primary municipal effluent under different hydraulic retention times (HRTs) and in a two-phases process using both primary and secondary wastewater effluents. Semi-continuous cultures were operated for 7 day at 5-, 3- and 1.5-day HRT and the different dilution rate showed a greater influence on the biomass composition and nutrient removal efficiency. Removal of N-NH₃ and P-PO₄ was over 99 % and the highest accumulation of polysaccharides (57.2 wt.%) was obtained at high HRT (5 day); the maximum content of proteins (26.9 wt.%) was achieved at 1.5-day HRT, even if, under this condition, a clear inefficiency in terms of ammonia removal was observed. Moreover the accumulation of N-NH₃ occurring at 1.5-day HRT caused the decrease of the photosynthetic response in terms of efficiency of light capture (α) and relative electron transport rate (rETR), both parameters extracted from the rapid light curves (RLC) measurements. No significant differences were observed for the total fatty acids (TFAs), with a content of 2–3.5 wt.% for each HRT condition. On the other hand, in the two-phases process, when a nutrient deprivation condition was induced by diluting the culture with the secondary wastewater effluent, the algal cells accumulated TFAs, achieving a maximum content of 9.7 wt.% and a great increment in terms of biomass (1.64?±?0.02 g L^?1) due to the ability of this algal strain to accumulate intracellular N. The wide and accurate investigation of the different aspects related to the whole process represents a relevant point of novelty in this research field and suggests the operational conditions for the start-up of an open pond system for wastewater treatment and biomass production for further applications.     

A Highly Luminescent Tetrahydrocurcumin IrIII Complex with Remarkable Photoactivated Anticancer Activity

Curcumin has chemopreventative properties against a variety of tumours, but has poor bioavailability. Here, two new bis-cyclometallated iridium(III) complexes have been prepared, featuring the natural product curcumin (CUR) or its reduced form, tetrahydrocurcumin (THC), as bidentate, anionic O O-binding ligands. The iridium THC complex is highly luminescent in deoxygenated solution and efficiently generates singlet oxygen under aerated conditions, whereas in the CUR analogue, other non-radiative decay pathways are competitive. The complexes are rapidly taken up by a variety of human tumour cell lines from solutions of micromolar concentration. They show negligible cytotoxicity in the absence of irradiation. When briefly irradiated with visible light, Ir-THC becomes highly phototoxic, inducing rapid apoptosis within 2 h. The results show the high potential of such complexes as sensitizers in photodynamic therapy (PDT).     

Cage-like structure formation during sol–gel polymerization of glycidyloxypropyltrimethoxysilane

The sol–gel polymerization of 3-glycidyloxypropyltrimethoxysilane (GTMS) was followed by size exclusion chromatography and ²⁹Si NMR. Extensive non-random cyclization under formation of polyhedral cycles – cubic cages – predominates at the beginning of the reaction. Structure growth of polysilsesquioxanes proceeds by combining the incompletely condensed cage frameworks. The extent of the cage formation increases with dilution and the amount of water and depends appreciably on a catalyst. The cage fraction was isolated from a reaction mixture using preparative size exclusion chromatography and identified by ²⁹Si NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS). High content of polyhedral cages prevents gelation of the trifunctional GTMS monomer. Reaction of pendant epoxy groups is much slower; however, at a late reaction stage the epoxy hydrolysis can be significant. Under some conditions, like base catalysis, polysilsesquioxane clusters are crosslinked by intermolecular condensation of SiOH with hydrolyzed epoxy groups and the system gels. The cage with epoxide functionalities may serve as a rigid precursor of crosslinking.     

Messages in molecules: ligand/cation coding and self-recognition in a constitutionally dynamic system of heterometallic double helicates

Double helicates are known to exhibit self-recognition characteristics determined by the coordination geometry of the metal involved as well as by the topicity of the ligands. Combining tridentate (terpyridine, T) or bidentate (bipyridine, B) subunits in a tritopic strand affords a set of ligands able to assemble by pairs to form double helicates, homo- or heterostranded, homo- or heterotopic, depending on the coordination properties of the metals involved. The four ligand strands, BBB, TTT, BBT, and TBT form constitutionally dynamic sets of double helicates with the metal ions Cu(I), Cu(II), and Zn(II); these helicates correspond to the correct coding of the BB, BT, and TT pairs for tetra-, penta-, and hexacoordinate Cu(I), Cu(II), and Zn(II) cations, respectively.     

Determination of Olanzapine in rat brain using liquid chromatography with coulometric detection and a rapid solid-phase extraction procedure

A sensitive and selective method was developed for the determination of the antipsychotic drug Olanzapine levels in rat brain tissue, based on HPLC with electrochemical detection. The analyses were carried out on a C8 reversed phase column (150 mm x 4.6 mm, 5 microm), using a mobile phase composed of methanol and a phosphate buffer (44.0 mM, pH 3.5), containing triethylamine (21:79, v/v), flowing at 1.2 mL min(-1). A high sensitivity coulometric detection analytical cell containing two flow-through low volume working electrodes was used: electrode 1 was set at +0.350 V and electrode 2 at -0.200 V. Olanzapine, administered to rats in different doses or in different times, was extracted from tissue homogenate of either the whole brain or specific areas (cortex, hyppocampus, nucleus striatum) with a rapid solid phase extraction procedure (SPE) on Oasis HLB cartridges. The method provided a high extraction yield of Olanzapine and internal standard (2-methylolanzapine) from brain tissue homogenate with absolute recovery values higher than 90.0%. The detector response was linear over a concentration range of 0.2-100.0 ng mL(-1) of Olanzapine. The limit of quantification (LOQ) was 0.2 ng mL(-1). Precision results, expressed by the intra-day and the inter-day relative standard deviation values, were satisfactory, better than 4.6%. Accuracy was satisfactory as well. This method proved to be suitable for the analysis of Olanzapine in rat brain tissues and for the study of distribution and pharmacokinetics of Olanzapine in rat brain after a single treatment with the antipsychotic drug.     

Labeling trees with a condition at distance two

An L(h,k)-labeling of a graph G is an integer labeling of vertices of G, such that adjacent vertices have labels which differ by at least h, and vertices at distance two have labels which differ by at least k. The span of an L(h,k)-labeling is the difference between the largest and the smallest label. We investigate L(h,k)-labelings of trees of maximum degree Δ, seeking those with small span. Given Δ, h and k, span λ is optimal for the class of trees of maximum degree Δ, if λ is the smallest integer such that every tree of maximum degree Δ has an L(h,k)-labeling with span at most λ. For all parameters Δ,h,k, such that h<k, we construct L(h,k)-labelings with optimal span. We also establish optimal span of L(h,k)-labelings for stars of arbitrary degree and all values of h and k.     

A simple route towards peptide analogues containing substituted (S)- or (R)-tryptophans

We investigated the Lewis acid-promoted Friedel-Crafts alkylation of indole and substituted indoles with dehydroalanine-containing dipeptides R-Xaa-Dha-OR¹. The reaction proceeded with modest to sufficient diastereoselectivity, and yields strongly varied depending on the Lewis acid selected. The substituent R¹ of the ester group revealed some impact on the preferential formation of (S)-Trp or (R)-Trp. We exploited the reaction to prepare different peptides containing substituted tryptophans. To test the efficacy of this method for preparing biologically relevant compounds, we synthesized two unprecedented analogues of endomorphin-1, the endogenous agonist of the μ-opioid receptor, having either (S)- or (R)-2-methyltryptophan in position 3.