The effect of solvent composition on swelling and shrinking properties of poly(acrylamide-co-itaconic acid) hydrogels

The peculiarities of the equilibrium swelling ratio and swelling-shrinking kinetics of polyelectrolyte copolymeric hydrogels consisting of acrylamide and itaconic acid (AAm/IA) have been studied in water/nonsolvent (acetone, methanol, ethanol and 1-butanol) mixtures as a function of solvent composition and IA content in the hydrogel. The phase transition of these hydrogels was generated by changing the solvent composition by progressive substitution of water by the nonsolvent. For all P(AAm/IA) hydrogels, the form of the shrinking curves was determined to be strongly dependent on the type of the nonsolvent used. The rate of shrinking of these hydrogels increased in the order 1-butanol < ethanol < methanol < acetone.     

New tetradentate Schiff-base polymers: preparation of poly[2,5-(didodecyloxy)phenylene-1,4-diyl-alt-N,N-(o-phenylene)-bis(salicylideneiminato-4,4-diyl)] and poly[2,5-(didodecyloxy)phenylene-1,4-diyl-alt-N,N-(alkylidene)-bis(salicylideneiminato-4,4-diyl)]s

New tetradentate Schiff-base polymers, in which phenylene units alternate with salicylideneiminato units, have been prepared by condensation of 2,5-(didodecyloxy)-1,4-bis(3-formyl-4-hydroxyphenyl)benzene (DFHB) with appropriate diamines in a mixed solution of CHCl₃/toluene/acetic acid with 31-79% yields. DFHB as the key building block was prepared by the Suzuki reaction of 2,5-(didodecyloxy)benzene-1,4-diboronic acid with 5-bromosalicylaldehyde in a two-phase solution of tetrahydrofuran/water in the presence of NaHCO₃/Pd(PPh₃)₄ in 45% yield. The molecular structures of the prepared compounds were identified by spectroscopy. Their absorption spectroscopic profiles have been analyzed.     

FT–IR spectroscopic study on the thermal and thermal oxidative degradation of nylons

The effects of heat and oxygen on nylon films were studied by FT–IR spectroscopy. Nylons 6, 66 and nylons containing carbonyl groups in either the diamine or the diacid moiety were prepared. Nylon films cast on aluminum were studied in an environmental chamber under controlled conditions. The progress of chemical and physical changes was monitored by FT–IR spectroscopy. Thermal energy caused largely an increase in crystallinity due to annealing and also an increase of nonhydrogen-bonded amide groups, which seemed to entail mainly amide groups from the amorphous region. The intensities of IR absorption bands related to the folded structure reduced as soon as heating began. The IR spectra of the carbonyl groups formed by thermal oxidation showed band shapes that indicated that the formed carbonyl groups were of many different origins. The presence of keto groups purposely inserted into the backbone chains increased the rate of oxidation. Pyrolysis of the nylons was also studied to supplement data obtained at lower temperatures.     

Synthesis of the C3-C19 segment of phorboxazole B

[reaction: see text]. Three segment-coupling Prins approaches to the C3-C19 segment of phorboxazole B have been developed. One successful strategy utilized a novel TMSBr-mediated cyclization that proceeded with complete axial selectivity. Displacement of bromide with cesium acetate provided the C13 hydroxyl stereocenter of 22. Additionally, treatment of alpha-acetoxy ether 20 with TFA enabled a more concise synthesis of the C3-C19 target 13 by allowing direct access to the equatorial alcohol.     

Effect of surface-perturbed intermolecular interaction on adsorption of simple gases on a graphitized carbon surface

In this paper, we investigate the effect of the solid surface on the fluid-fluid intermolecular potential energy. This modified fluid-fluid interaction energy due to the inducement of a solid surface is used in the grand canonical Monte Carlo (GCMC) simulation of various noble gases, nitrogen, and methane on graphitized thermal carbon black. This effect is such that the effective interaction potential energy between two particles close to surface is less than the potential energy if the solid substrate is not present. With this modification the GCMC simulation results agree extremely well with the experimental data over a wide range of pressures while the simulation results with the unmodified potential energy give rise to a shoulder near the neighborhood of monolayer coverage and the significant overprediction of the second and higher layer coverages. In particular the unmodified GCMC results exhibit very sharp change in those higher layers while the experimental data have a much gradual change in the uptake. We will illustrate this theory with adsorption data of argon, xenon, neon, nitrogen, and methane on graphitized thermal carbon black.     

Fast determination of the tin content in cassiterite ores by photon activation method

Photon activation analysis has been success-fully applied to the fast and non-destructive analysis of tin in cassiterite ores based on the 159.7 keV gamma line of^123mSn produced in the¹²⁴Sn/γ, n/^123mSn reaction. In order to improve the accuracy of analytical results, corrections for self-absorption and pile-up effects were performed. Under typical conditions /15 μA electron beam current, 15 MeV bremsstrahlung energy, 5 min irradiation time and 10 min measurement/ the sensitivity of the analysis is 10 ppm. The proposed method can be used for routine analysis of tin in geological samples.     

Flux synthesis of the noncentrosymmetric cluster compounds Cs2SnAs2Q9 (Q = S,Se) containing two different polychalcoarsenite beta-[AsQ4]3- and [AsQ5]3- ligands

Two noncentrosymmetric quaternary tin chalcoarsenates, Cs(2)SnAs(2)S(9) (1) and Cs(2)SnAs(2)Se(9) (2), were synthesized by the polychalcoarsenate flux method. Compound 1 crystallizes in the orthorhombic space group Pmc2(1) with a = 7.386(3) A, b = 14.614(5) A, c = 14.417(5) A, and Z = 4. Compound 2 crystallizes in the monoclinic space group P2(1) with a = 7.715(5) A, b = 17.56(1) A, c = 7.663(5) A, beta = 115.86(1) degrees, and Z = 2. Both structures contain the same tin-centered molecular cluster anions [Sn[AsQ(2)(Q(2))][AsQ(Q(2))(2)]](2)(-) (Q = S, Se) separated by Cs cations. The Sn(4+) ion is in a distorted octahedral environment coordinated by two different pyramidal-shaped tridentate ligands, [AsQ(2)(Q(2))](3)(-) and [AsQ(Q(2))(2)](3)(-). These compounds absorb visible light at energies above 1.98 and 1.45 eV for 1 and 2, respectively. Differential thermal analysis revealed that 1 melts at 350 degrees C and on cooling gives a glass. The glass recrystallizes at 268 degrees C upon subsequent heating. Compound 2 melts at 258 degrees C.     

Electron spin resonance studies of the radiolysis of bi-π-cyclopentadienylalkyls of molybdenum and tungsten

Exposure of (C₅H₅)₂MO(CH₃)₂ and (C₅H₅)₂W(CH₃)₂, prepared from the corresponding dichlorides, to ²⁰Co γ-rays at 77 K gave H₂C.CML₃ carbene species characterised by their ESR spectra, together with a central feature possibly due to the parent cations. Dilute solutions in CD₃OD gave features assigned to the parent anions which were converted on bleaching with visible light into methyl radicals, and H₂C.ML₃ radicals. From the magnitude of the ¹H and ¹⁸³W hyperfine coupling constants, it is deduced that the SOMO for H₂C.WL₃ radicals is strongly localised on carbon.Dilute solutions in aqueous sulphuric acid also gave species with A(2H) = 20 G, identified as the carbene derivatives, H₂C.Ml₃. These were formed on annealing, as signals assigned to HSO₄ · radicals were lost.     

α-CGRP disrupts amylin fibrillization and regulates insulin secretion: implications on diabetes and migraine

Despite being relatively benign and not an indicative signature of toxicity, fibril formation and fibrillar structures continue to be key factors in assessing the structure–function relationship in protein aggregation diseases. The inability to capture molecular cross-talk among key players at the tissue level before fibril formation greatly accounts for the missing link toward the development of an efficacious therapeutic intervention for Type II diabetes mellitus (T2DM). We show that human α-calcitonin gene-related peptide (α-CGRP) remodeled amylin fibrillization. Furthermore, while CGRP and/or amylin monomers reduce the secretion of both mouse Ins1 and Ins2 proteins, CGRP oligomers have a reverse effect on Ins1. Genetically reduced Ins2, the orthologous version of human insulin, has been shown to enhance insulin sensitivity and extend the life-span in old female mice. Beyond the mechanistic insights, our data suggest that CGRP regulates insulin secretion and lowers the risk of T2DM. Our result rationalizes how migraine might be protective against T2DM. We envision the new paradigm of CGRP : amylin interactions as a pivotal aspect for T2DM diagnostics and therapeutics. Maintaining a low level of amylin while increasing the level of CGRP could become a viable approach toward T2DM prevention and treatment.

CGRP concentration is elevated in migraine conditions. The protective effect of migraine against type 2 diabetes is attributed to the ability of CGRP to remodel human amylin aggregation and to suppress the secretion of mouse insulin 2 (the orthologue of human insulin).     

Conjugated enynes as a new type of substrates for olefin metathesis

[reaction: see text] It has been demonstrated for the first time that conjugated enynes can be employed as a facile substrate in olefin metathesis with the use of a bispyridine-substituted ruthenium benzylidene catalyst. Cross-metathesis of the enynes with alkenes turns out to proceed with preferential formation of (Z)-isomers over (E)-isomers up to >25:1 in moderate to good yields. The intramolecular version of conjugated enynes affords novel butadienyl cycloalkenes, which are a highly useful synthetic building blocks, in acceptable yields.