Influence of n-ZnO Morphology on Sulfur Crosslinking and Properties of Styrene-Butadiene Rubber Vulcanizates

This paper examines the influence of the morphology of zinc oxide nanoparticles (n-ZnO) on the activation energy, vulcanization parameters, crosslink density, crosslink structure, and mechanical properties in the extension of the sulfur vulcanizates of styrene-butadiene rubber (SBR). Scanning electron microscopy was used to determine the particle size distribution and morphology, whereas the specific surface area (SSA) and squalene wettability of the n-ZnO nanoparticles were adequately evaluated using the Brunauer–Emmet–Teller (BET) equation and tensiometry. The n-ZnO were then added to the SBR in conventional (CV) or efficient (EV) vulcanization systems. The vulcametric curves were plotted, from which the cure rate index (CRI) rate of the vulcanization and the activation energy were calculated. The influence on the mechanical properties of the SBR vulcanizates was stronger in the case of the EV curing system than when the CV curing system was used. Of the vulcanizates produced in the EV curing system, the best performance was detected for n-ZnO particles with a hybrid morphology (flat-ended rod-like particles on a “cauliflower” base) and high SSA. Vulcanizates produced using the CV curing system showed slightly better mechanical properties after the addition of nanoparticles with a “cauliflower” morphology than when the rod-like type were used, irrespective of their SSA. In general, nanoparticles with a rod-like structure reduced the activation energy and increased the speed of vulcanization, whereas the cauliflower type slowed the rate of the process and the vulcanizates required a higher activation energy, especially when using the EV system. The crosslink structures were also more clearly modified, as manifested by a reduction in the polysulfidic crosslink content, especially when n-ZnO activators with a rod-like morphology were applied.

Molecular self-assembly of 1D infinite polyiodide helices in a phenanthrolinium salt

A new linear polymeric polyiodide, catena-poly[tris(1,10-phenanthrolin-1-ium)tris(1,10-phenanthroline)heptaiodide], was prepared by one-step synthesis. Its formation is driven by hydrogen-bond assisted supramolecular assembly in the presence of chromium(iii) acetate. Its structure has been characterized by the means of single-crystal X-ray diffraction. To date, this is only one of the few examples of organized linear infinite polyiodides with a known structure. The interplay between the interactions within the hypervalent iodine chain and its supramolecular environment is elucidated. The electrical, thermal, and spectroscopic properties of the studied compound were investigated and associated with the structural features. The infinite character of the polyiodide chain and its similarity to the blue starch-iodine complex has been additionally confirmed by Raman spectroscopy. Despite the apparent structural and spectroscopic similarities with the previously reported 1D polymeric polyiodide, its physical properties, i.e. electrical conductivity and thermal stability, differ significantly. This can be rationalized by the differences in the orbital overlap within the iodine chain, as well as the distinct interactions with the cation.

Synthesis and activity of opioid peptidomimetics with β2- and β3-amino acids

Morphiceptin (Tyr-Pro-Phe-Pro-NH₂) is a selective ligand of the mu opioid receptor, an important target in pain regulation. In this study, morphiceptin was modified at positions 2 or 3 by introduction of β²- or β³-amino acids and additionally in position 1 by replacing Tyr by Dmt (2',6'-dimethyltyrosine), which resulted in obtaining enzymatically stable analogs with mixed opioid receptor affinity profiles. An analog of the sequence Dmt-d-Ala-(R)-β²-1-Nal-Pro-NH₂ [Nal=3-(1-naphthyl)-alanine] showed very high activity at the mu and delta receptors in the calcium mobilization functional test but did not cross the artificial membrane imitating the blood-brain barrier. In the in vivo test this analog induced strong antinociceptive effect in the writhing test in mice after intraperitioneal but also oral administration and inhibited diarrhea similarly to loperamide. Therefore, it may become an interesting lead compound in the development of peripherally restricted drugs for the treatment of gastrointestinal disorders.

Characterization and cytotoxic effect of aqua-(2,2',2''-nitrilotriacetato)-oxo-vanadium salts on human osteosarcoma cells

The use of protonated N-heterocyclic compound, i.e. 2,2'-bipyridinium cation, [bpyH+], enabled to obtain the new nitrilotriacetate oxidovanadium(IV) salt of the stoichiometry [bpyH][VO(nta)(H2O)]H2O. The X-ray measurements have revealed that the compound comprises the discrete mononuclear [VO(nta)(H2O)]- coordination ion that can be rarely found among other known compounds containing nitrilotriacetate oxidovanadium(IV) moieties. The antitumor activity of [bpyH][VO(nta)(H2O)]H2O and its phenanthroline analogue, [phenH][VO(nta)(H2O)](H2O)0.5, towards human osteosarcoma cell lines (MG-63 and HOS) has been assessed (the LDH and BrdU tests) and referred to cis-Pt(NH3)2Cl2 (used as a positive control). The compounds exert a stronger cytotoxic effect on MG-63 and HOS cells than in untransformed human osteoblast cell line. Thus, the [VO(nta)(H2O)]- containing coordination compounds can be considered as possible antitumor agents in the osteosarcoma model of bone-related cells in culture.

Synthesis, crystal structure and magnetic properties of H2tppz[ReCl6] and [Cu(bpzm)2(μ-Cl)ReCl3(μ-ox)Cu(bpzm)2(μ-ox)ReCl3(μ-Cl)]n

Two new Re(iv) compounds of formulae H2tppz[ReCl6] (1) and [Cu(bpzm)2(μ-Cl)ReCl3(μ-ox)Cu(bpzm)2(μ-ox)ReCl3(μ-Cl)]n (2) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and bpzm = bis(pyrazolyl-1-yl)methane] have been prepared and their crystal structures determined by X-ray diffraction on single crystals. Compound 1 is a mononuclear species whose structure consists of octahedral hexachlororhenate(iv) anions and diprotonated H2tppz(2+) cations which are arranged in the unit cell as alternating anionic and cationic layers, held together by electrostatic forces. The structure of 2 is made up of alternating [Cu(1)(bpzm)2](2+) and [(ox)ReCl3(μ-Cl)Cu(2)(bpzm)2(μ-Cl)ReCl3(ox)](2-) entities interlinked by oxalate bridges to afford a neutral heterobimetallic chain. The oxalate group adopts the didentate (at Re)/monodentate (at Cu) bridging mode. The magnetic behavior of 1 and 2 has been investigated over the temperature range 1.9-295 K. 1 is a magnetically diluted Re(iv) complex, the relatively large value of the zero-field splitting of the ground level [D = -15.8(2) cm(-1)] accounting for the variation of χMT in the low temperature range. Weak intrachain ferromagnetic interactions between Re(iv) and Cu(ii) through oxalate (J1 = +0.15 cm(-1)) and single chloro (J2 = +4.9 cm(-1)) bridges occur in 2 which are obscured by the large zero-field splitting of the Re(iv) ion (DRe = 42 cm(-1)). In addition, interchain antiferromagnetic interactions are also involved in 2 which are responsible for the metamagnetic behavior observed, the value of the critical dc magnetic field (Hc) being 20 kOe.

New benzimidazole derivatives with potential cytotoxic activity--study of their stability by RP-HPLC

Obtained benzimidazole derivatives, our next synthesized heterocyclic compounds, belong to a new group of chemical bondings with potential anticancer properties (Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2006, J Liguid Chrom Rel Tech 29: 2367-2385; Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2008, Wiad Chem 62: 11-12, in Polish; Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2011, J Liguid Chrom Rel Tech 34: 1901-1912). We used HPLC analysis to determine stability of these compounds in 0.2% DMSO (dimethyl sulfoxide). Optimisation of the chromatographic system and validation of the established analytical method were performed. Reversed phases (RP-18) and a 1:1 mixture of acetate buffer (pH 4.5) and acetonitrile as a mobile phase were used for all the analysed compounds at a flow rate 1.0 mL/min. The eluted compounds were monitored using a UV detector, the wavelength was specific for compounds 6 and 9 and compounds 7 and 10. The retention time was specific for all four compounds. The used method was found to have linearity in the concentration range of (0.1 mg/mL-0.1 μg/mL) with a correlation coefficient not less than r(2)=0.9995. Statistical validation of the method proved it to be a simple, highly precise and accurate way to determine the stability of benzimidazole derivatives in 0.2% DMSO. The recoveries of all four compounds examined were in the range 99.24-100.00%. The developed HPLC analysis revealed that the compounds studied remain homogeneous in 0.2% DMSO for up to 96 h and that the analysed N-oxide benzimidazole derivatives do not disintegrate into their analogues - benzimidazole derivatives. Compounds 8, 6 and 9 exhibit the best cytotoxic properties under normoxic conditions when tested against cells of human malignant melanoma WM 115.

New benzimidazole derivatives with potential cytotoxic activity--study of their stability by RP-HPLC

Obtained benzimidazole derivatives, our next synthesized heterocyclic compounds, belong to a new group of chemical bondings with potential anticancer properties (Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2006, J Liguid Chrom Rel Tech 29: 2367-2385; Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2008, Wiad Chem 62: 11-12, in Polish; Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2011, J Liguid Chrom Rel Tech 34: 1901-1912). We used HPLC analysis to determine stability of these compounds in 0.2% DMSO (dimethyl sulfoxide). Optimisation of the chromatographic system and validation of the established analytical method were performed. Reversed phases (RP-18) and a 1:1 mixture of acetate buffer (pH 4.5) and acetonitrile as a mobile phase were used for all the analysed compounds at a flow rate 1.0 mL/min. The eluted compounds were monitored using a UV detector, the wavelength was specific for compounds 6 and 9 and compounds 7 and 10. The retention time was specific for all four compounds. The used method was found to have linearity in the concentration range of (0.1 mg/mL-0.1 μg/mL) with a correlation coefficient not less than r(2)=0.9995. Statistical validation of the method proved it to be a simple, highly precise and accurate way to determine the stability of benzimidazole derivatives in 0.2% DMSO. The recoveries of all four compounds examined were in the range 99.24-100.00%. The developed HPLC analysis revealed that the compounds studied remain homogeneous in 0.2% DMSO for up to 96 h and that the analysed N-oxide benzimidazole derivatives do not disintegrate into their analogues - benzimidazole derivatives. Compounds 8, 6 and 9 exhibit the best cytotoxic properties under normoxic conditions when tested against cells of human malignant melanoma WM 115.

New Derivatives of Quinazoline and 1, 2-DihydroquinazolineN3-Oxide with Expected Antitumor Activity

Some derivatives of quinazoline and 1, 2-dihydroquinazoline N(3)-oxide were synthesised and their cytotoxic activities against human leukaemia HL-60 cells under hypoxic and aerobic conditions were tested and compared to tirapazamine as the reference compound. Compound 8 showed 5-fold higher toxicity under hypoxic conditions than in normal oxygen atmosphere. The structure of quinazoline derivatives was established by X-ray crystal structure analysis.